EPA-IAG-79-D-X0513

NBS/EPA

ENERGY ENVIRONMENT

PROJECT

to the

Enveonmental Protection Agency

Office of Envaonmental Processes & Effects

1980

US DepL of Commerce

National Bureau of Standards

Washhglonb DC 20234

TABLE OF CONTENTS

FORWARD i

INTRODUCTION & SUMMARY ii

81-BCKa-ENERGY RELATED POLLUTANT MEASUREMENT AND INSTRUMENTION AND

DEVELOPMENT

1. Energy-Related Water Pollutant Analysis Instrumentation 1

l.a. Development of Marker Compound 1

l.b. Liquid Chromatography - Mass Spectrometry 9

l.c. Liquid Chromatography with Electrochemical Detection (LC-EC) 12

l.d. Interferences in the Inductively Coupled Plasma (ICP) Technique 17

l.e. Metal Speciation Using High Performance Liquid Chromatography/

Atomic Absorption Spectrometry 20

l.f. Sulfur Speciation in Coal 23

1.

g. Ionic Chromium Speciation Measurements 24

81-BCKb-ENERGY RELATED WATER POLLUTANT ANALYSIS INSTRUMEMENTATION

2. Development of Measurement Methods for Non-Volatile Organic

Pollutants in Water Due to Energy Technologies 26

2. a. Fluoroimmunoassay Procedure Developed for Dinitrophenols in Water.. 26

2.b. Development of a Fourier Transform Infrared Spectrometer-Gas

Chromatograph Interface and Its Application to Pollutant

Identification .28

81-BCLa-ENERGY RELATED POLLUTANTS AND EFFECTS MONITORING AND

ASSOCIATED METHODS AND TECHNIQUES DEVELOPMENT

1. Development of SRM's for Stationary Sources Associated with Energy

Production 30

l.a. NO

2

in Air Gas Blend SRM's 30
l.b. SO

2

in N

2

SRM's 32

1.

c. NO in N

2

SRM's 33

1 .d. O

2 in N2

SRM's 34

2. Development of SRMs for Monitoring ambient Air Impacted by

Emission Resulting from Energy Production 34

2. a. CO

2

in Air SRMs 34

2.b. Automation of Gas Analysis 34

2.

C. Development of a Traceability Procedure for Gas Standards 35

3. Develop Methods for Dispersal of Particulates on Filter Media and

Methods for Determining and Controlling the Composition and

Morphology of Such Dispersed Particulates 37

3.

a. Thin Glass Films Produced by Focused-ion Beam Sputtering 37

4. Particulate Physical and Chemical Characterization 40

4. a. Particle Doppler Shift Spectrometer (PDSS) 40

4.b. Particulates on Glass Fiber Filters: Certification of SRM's

for Pb, Sulfate, and Nitrate on Filter Media 42

81-BCLb-ENERGY RELATED AIR POLLUTANT ANALYSIS INSTRUMENTATION

1. Development of an Instrument to Measure Airborne Sulfate

Particulate Matter 43

81-BCLc-ENERGY RELATED POLLUTANTS AND EFFECTS MONITORING AND ASSOCIATED

METHODS AND TECHNIQUES DEVELOPMENT

1. Radiocarbon as an Environmental Trace 46

l.a. Applications 46

l.b. Research Advances 47

l.c. Statistical Evaluations of the International Radiocarbon Cross

Calibration Exercise, and of the Natural Radiocarbon Fluctuations. .50
l.d. Advances in Small Sample Radiocarbon Measurement Techniques:

Application to the Assay of Individual Atmospheric Chemical

Species 55

8l-BCMa-ENER6Y RELATED POLLUTANTS AND EFFECTS MONITORING AND ASSOICATED

METHODS AND TECHNIQUES DEVELOPMENT

1. Energy Related Water Pollutant Standard Reference Materials 59

l.a. Aqueous Polynuclear Aromatic Hydrocarbons in Water (SRM 1644) 59

l.b. First Natural Matrix Trace Organic SRM Issued for Shale Oil 63

l.c. Work Plan and Evaluation/Feasibility Study of Drilling Fluid

Reference Standards for Chemical Analysis 67

l.d. Laser Analysis of Pollutants in Cryogenic Matrices 69

81-BCMb-ENERGY RELATED POLLUTANTS AND EFFECTS MONITORING AND ASSOCIATED

METHODS AND TECHNIQUES DEVELOPMENT

1. Development of Organic SRM's for the Calibration of Energy-Related

Water Pollutant Measurement Methods 70

l.a. Analysis of Phenolic and Polynuclear Aromatic Hydrocarbon Species

in Alternate Fuels and Effluents 71

l.b. Combined LC/MS Technique for Direct Quantitative Analysis of

Individual Organic Compounds in Complex Mixtures 77

l.c. Development of Phenol in Water SRM 78

81-BCN-ENERGY RELATED POLLUTANTS AND EFFECTS MONITORING AND ASSOCIATED

METHODS AND TECHNIQUES

1. Radiological Pollutant Quality Assurance 83

2 32

l.a. Th Solution 83

l.b. Mixed Radionuclide Solutions 83

APPENDIX 1 91

APPENDIX 2 1^5

APPENDIX 3 138

APPENDIX 4 169
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FOREWORD

The role of the National Bureau of Standards (NBS) in the Interagency

Energy/Environment R&D program, coordinated by the Office of Research

and Development, U. S. Environmental Protection Agency, is to provide

those services necessary to assure data quality in measurements being

made by a wide variety of Federal, state, local, and private industry

participants in the entire program. The work at NBS is under the

direction of the Office of Environmental Measurements and is conducted

in the Center for Analytical Chemistry, the Center for Radiation Research,

and Center for Chemical Physics. NBS activities are in the Characterization, Measurement, and Monitoring Program category and address

data quality assurance needs in the areas of air and water measurement

methods, standards, and instrumentation. NBS outputs in support of this

program consist of the development and description of new or improved

methods of measurement, studies of the feasibility of production of

Standard Reference Materials for the calibration of both field and laboratory instruments, and the development of data on the physical and

chemical properties of materials of environmental importance in energy

production. This report is the last of a series of reports which had

been issued every six months by NBS over the past five years (i.e. 1975-

1980) as part of the Interagency Energy/Environmental program.

William H. Kirchhoff

Chief, Office of Environmental Measurements

National Bureau of Standards
INTRODUCTION AND SUMMARY

This report describes work performed by the National Bureau of Standards

(NBS) during the period, January 1980 through December 1980, under the

Interagency Agreement (EPA-79-D-X0513) between the U. S. Environmental

Protection Agency and NBS. This Agreement authorizes NBS activities

concerned with the development of measurement methods, techniques. Standard

Reference Materials (SRM's), and instrumentation in support of other

programs for evaluating environmental effects of increased energy use. The resultant measurement methods and SRM's are used to provide data

quality assurance for measurements made in the laboratory and in field

monitoring associated with energy production and use. The highlights

for this reporting period in the eight sub-agreement areas are given

below. Detailed project information is provided in the body of this

report.

81 BCKa - ENERGY RELATED POLLUTANT MEASUREMENT AND INSTRUMENTATION

DEVELOPMENT

Under the task, "Energy Related Water Pollutant Analysis Instrumentation",

internal standard mixtures required for testing the Master Analytical

Scheme (MAS) were prepared. Three different standard mixtures, "purgeable",

"extractable", and "intractable" organic compounds, each at two concentration

levels were prepared. Since time did not permit extensive stability testing,

accelerated aging studies were performed on test mixtures similar to the

internal standard mixtures to allow a preliminary assessment of stability.

Although some decomposition was observed, the rates were such that properly

stored mixtures (0-5 °C) were expected to be usable for the required several

months of evaluation of the MAS. Approximately 600 individually sealed

ampoules of the various internal standard mixtures were prepared, and the

400 required for initial tests of the MAS were delivered as requested.

Ampoules from all six internal standard mixtures prepared have been stored

at 0-5 °C here at NBS. Periodically, selected ampoules will be removed

from storage and the concentrations of individual components checked by

gas or liquid chromoatography to permit another evaluation/assessment of

stability.
A patent application covering the NBS developed interface device for

a conventional liquid chromatograph and a conventional mass spectrometer was approved. Several LC/MS experiments have been performed to

evaluate and optimize this system for quantitative measurements.

Work related to liquid chromatography-electrochemical detection (LC-EC)

focused on the development of new chromatographic separations and the

optimization of the electrochemical detection response. A manuscript

on NBS activities in LC-EC has been submitted to Analytical Chemistry.

Work related to the inductively coupled plasma (ICP) technique focused

on the characterization and correction for interferences which degrade

the quality of analytical results.

In an effort to develop/improve methodologies for characterizing and

quantitating chemical species in various energy related matrices,

activities focused on the use of high performance liquid chromatography/

atomic absorption spectrometry, plasma emission spectrometry and ion

exchange/atomic absorption spectrometry.

81 BCKb - ENERGY RELATED WATER POLLUTANT ANALYSIS INSTRUMENTATION

Work performed under the task, “Development of Measurement Methods for

Non-Volatile Organic Pollutants in Water Due to Energy Technologies "

,

focused on the development of a fluoroimmunochemical procedure for

detection and quantitation of dini trophenols in water. Specific immunoglobulins were prepared and used in quantitative competitive assay

experiments to assess their effectiveness.

Additionally, installation of the Fourier transform infrared (FTIR)

spectrometer was completed. Plans have been made to use the FTIR in

four specific areas: high resolution/low pressure gas work, liquid

samples, liquid chromatography and gas chromatography. Construction and

testing of an interface for wall coated open tubular gas chromatographic

columns (WCOT), which allow real-time FTIR analysis of compounds, and

other gas chromatographic studies were conducted this reporting period.
Previous reports included progress of activities related to Coherent AntiStokes Raman Spectroscopy (CARS). An evaluation of CARS and its application to high performance liquid chromatography is summarized in Appendix

2 .

81 BCLa - ENERGY RELATED POLLUTANTS AND EFFECTS MONITORING AND ASSOICATED

METHODS AND TECHNIQUES DEVELOPMENT

Under the task, "Development of SRM's for Stationary Sources Associated

with Energy Production ", measurement of the concentration of nitrogen dioxide

(NO

2

) in gas mixtures on a relative basis has been completed. Work related

to determining the final concentration value of the 250, 500, 1000 and 2500

ppm NO

2

mixtures and the length of the period of certification must continue

before final issuance of the mixtures as SRM's. Two new SRMs consisting

of 50 and 100 ppm nominal concentration of sulfur dioxide in nitrogen are nearing completion. Standard Reference Materials have been issued for 1500

and 3000 ppm NO in N

2

. Two new SRM's (SRM 2657 and SRM 2658) consisting of

two and ten mole percent O

2

in N

2 are now available (see certificate in

Appendix).

Under "Development of SIWs for Monitoring Ambient Air Impacted by Emissions

Resulting from Energy Production", work has been completed on the analysis

of tbe air which will be used to prepare the CO

2

in Air SRM's. Fifty

sample lots of approximately 320, 330, and 340 ppm CO

2

in air are being

prepared. A third COGAS system has been constructed for the automation of

permeation tube calibrations. A traceability procedure/protocol for gas

standards has been developed which in essence transfers the responsibility

for producing large numbers of accurate standards (Certified Reference

Materials) to the specialty gas industry. A document has been prepared for

publication under the Interagency Energy- Environment program, entitled "A

Procedure for Establishing Traceability of Gas Mixtures to Certain National

Bureau of Standards Standard Reference Materials".

iv
The goal of work under task " Develop Methods for Dispersal of

Particulates on Filter Media and Methods for Determining and Controlling

the Composition and Morphology of such Dispersed Particulates ", was to

perform the research and development required to produce thin standard

samples especially useful for calibration of x-ray fluorescence analysis

of collected airborne particulate matter. Several candidate methods for

preparing such samples have been investigated and the results are described

in this report.

Under " Particulate Physical and Chemical Charaterization ", results of

studies to improve and verify the particle size and count measurements

with particle Doppler Shift Spectrometry (PDSS) is described. Several

publications detailing NBS work with PDSS are included in the appendix.

Final certification of SRM 2673, Sulfate and Nitrate on Filter media,

and SRM 2674, Lead on Filter media, has been completed (see Certificates

in Appendix).

81 BCLb - ENERGY RELATED AIR POLLUTANT ANALYSIS INSTRUMENTATION

Under the task, " Development of an Instrument to Measure Airborne Sulfate

Particulate Matter", the development and characterization of the pulsed

Electrostatic Precipitator-Flame Photometric Detector (PEP-FPD) system

for the measurement of ambient level aerosol sulfur concentrations has

been completed and a final report is in the review process. A summary

of these characterization and optimization activities is described in

this report.

81 BCLc - ENERGY RELATED POLLUTANTS AND EFFECTS MONITORING AND

ASSOCIATED METHODS AND TECHNIQUES DEVELOPMENT

Work under the task, " Radiocarbon as an Environmental Trace ", has continued

with the objective of utilizing the natural ^‘*C/^^C ratios to distinguish

7
between biogenic and fossil pollutant sources. A rather detailed

description of activities related to radiocarbon measurements (e.g.

research ackances. statistical evaluations of interlaboratory data,

advances in small sanple radiocarbon measurement techniques) is incloclmd In this report.

81 BCMa - ENERGY RELATED POLLUTANTS AND EFFECTS MONITORING AND

ASSOCIATED METHODS AND TECHNIQUES DEVELOPMENT

Under the task, “Energy Related Water Pollutant Standard Reference

Materials ”, certification and issuance of SRM 1644, (Polynculear

Aroiwitic Hydrocarbons) was completed. This SRM includes three generator

columns (anthrtncene, benz(a)anthracene, and benzo(a)pyrene) which

can be used to produce known concentrations of these PAH's in aqueous

solirtioms. The first natural matrix SRM for trace level organic con- stituents (Org*nics in Shale Oil, SRM 1580) was also issued. SRM 1580,

is intended primarily for evaluating the reliability of analytical

methods used for the determination of trace level polynuclear aromatic

hydrocarbons, piienols, and nitrogen heterocyclic compounds in shale oil,

coal-derived liquids, or petroleum products. In addition, this SRM

may be used as a surrogate standard for any complex environmental

extrekct containing classes of compounds for which the SRM is certified.

A work plan was developed and approved to intitate evaluation/feasibility

studies of drilling fluid reference standards. The objective of this

activity is to prepare a drilling fluid mixture which could be useful

in evaluative/assessment studies of chemical constituents on aquatic

and terrestrial environment, as well as provide an important reference

standard in a quality assurance protocol for measurements made on discharges from drilling and production operations.

Work continued on the development improvment, and application of laser

Raman spectroscopy to the analysis of organic pollutants. An optical

vi
mulitchannel analyzer and a commerical gas chromatograph were acquired.

The sampling system has been refabricated to provide for higher sensitivity and sample through-put. A publication describing matrix

isolation Raman spectroscopy is included in the Appendix.

81 BCMb - ENERGY RELATED POLLUTANTS AND EFFECTS MONITORING AND

ASSOCIATED METHODS AND TECHNIQUES DEVELOPMENT

Activities under the task, " Develop Organic SRM's for the Calibration

of Energy-Related Water Pollutant Measurement Methods ", focused on the

development of SRM’s for organic pollutants associated with emerging

energy technologies. Experience and knowledge gained from research

studies conducted with the LC-MS technique (see BCKa) have been applied

to direct quantitative analysis of individual organic compounds in complex

mi xtures

Studies have continued for the development of a phenol in water SRM.

A comparison of the stability of selected phenols in distilled water

and in industrial wastewater using HPLC was performed and the results

are included in this report.

81 BCN - ENERGY RELATED POLLUTANTS AND EFFECTS MONITORING AND

ASSOCIATED METHODS AND TECHNIQUES DEVELOPMENT

Work performed under the task, " Radiological Pollutant Quality Assurance ",

resulted in the preparation and characterization of two hundred ampoules

of thorium-232 solution for EPA/LV. Also, two concentration levels of

a mixed radionuclide solution standard were prepared and issued to

EPA/LV. Reports of calibration for these standard solutions are included

in the body of this report.
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81-BCK-a-ENERGY RELATED POLLUTANT MEASUREMENT AND INSTRUMENTATION

AND DEVELOPMENT

1 . Energy-Related Water Pollutant Analysis Instrumentation

1 .a. Development of Marker Compounds

The internal standard mixtures required for testing the Master Analytical

Scheme have been prepared and delivered.

A final list of 23 deuterium labeled compounds was agreed upon for use as internal standards in the trial implementation of the Master Analytical Scheme.

The standards each consist of seven to eleven compounds in a solvent. Three

different mixtures, "purgeable," "extractable," and "intractable" organic

compounds, each at two concentration levels were prepared. The components and

gravimetric concentrations are shown in Tables 1, 2, and 3.

Table 1

Internal Standards for "Purgeables"

- - — Set No.l---- ---- Set No. 2 — - - yq/ampoule^ yg/L in yg/ampoule^ yg/L in H 2 p*^

Bromoethane-dg 0.15 0.2g 1.47 2.9

Diethyl ether-dio 1.36 2.7 13.5 27.0

Ani sole-2 ,4, 6-da 1.25 2.5 12.4 24.9

Chlorobenzene-dg 0.17 0

34 1.69 3.4

n-Decane-d22 1.40 2.8 13.9 27.8

Naphthalene-de 1.24 2.5 12.4 24.7

^Each ampoule also contains 1 yL of methanol

^Concentration is yg/L if the contents of one ampoule are added to a 500

water sample.

1
Table 2

Internal Standards for "Extractables"

yg/ampoule = yg/L in

Set No. 1 Set No. 2

o-Xylene-dio 11.3 551

Ni trobenzene-ds 519 2463

Naphthalene-da 95.0 383

Anthracene-dio 41.1 40

Di-n-octyl ether-da 4 590 2561

Acridine-da 98.2 499

Phenyl ethyl ami ne-d4 10.0 517

Hexamethy1 enetetrami ne-d

^ 98.8 500

Phenol -de 460 2134

Benzoic Acid-ds 11.4 499

Bisphenol A-die 499 2502

®When added to 1 L of water.

Table 3

Internal Standards for "Intractables"

yg/ampoule = yg/L in HzO^

Set No. 1 Set Ho. 2

n -Butyl amine-da 570 2058

n-Butyric Acid-dy 51 2342

2-Naphthalenesulfonic Acid-dy 99 501

n-Dodecyl Phosphate-da 5 484 2047

Ethanol -ds 120 512

Acetonitrile-da 544 2709

t-Butanol-dg 112 519

^When added to 1 L of water.

2
Synthesis of Labeled Compounds

Two labeled compounds, 2-naphthalenesulfonic acid-d? and mono-n-dodecyl- i phosphoric acid-d 2 s» were synthesized. The preparation of the 2-naphthalenesulfonic acid-d7 was briefly described in the previous report. Mono-n-dodecyl

phosphoric acid was prepared from the commercially available n-dodecyl alcohol

da 6 according to the scheme:

0

CDs(CDj)iiOD CD3(CD2)n0P{0C6H5)2

or

0

CD3(CD2)iiOP(OH)2

The purity of the material was 98 percent as established by gas chromatography of the tri methyl si lyl derivative. The impurity was identified as phosphoric acid.

Chemical and Isotopic Purity of Marker Compounds

Each compound was checked for purity by gas chromatography (GC) or liquid

chromatography (LC) for quantitative data and also by mass spectrometry. The

results are summarized in Table 4.

Isotopic purities shown in Table 5 were calculated from an average of six

scans of the molecular ion cluster of the underivatized compounds except for:

(1) bisphenol-A-di 4 which was measured from the molecular ion of the trimethyl si lyl derivative; (2) n-butyric acid-d?, ethanol -ds, and phenol -ds which

were measured on the molecular ions of the material formed by the simultaneous

introduction of the corresponding fully deuterated compound and a large excess of water into the source of the mass spectrometer; (3) di-n-octyl ether which

J. was measured at m/z 130 (CsDiy ); (4) t-butanol-dg which was measured at

m/z 64 (C 4 D 8 ^‘) at a resolution of 5200. This resolution is sufficient to

eliminate interference from oxygen containing fragments. The t-butanol-dg was formed from t-butanol-dio by the simultaneous introduction of a large excess of water.

3
Table 4

Chemical Purity of Marker Compounds

Chemical Purity

Compound Quantitative Method % Impurities

Acetonitrile-da GC <1%

Acridine-dg GC <1%

Ani sole-2,4, 6-da GC <1%

Anthracene-dio GC <1%

Benzoic-dg acid GC <1%

Bisphenol-A-di 4 LC ND

Bromoethane-dg GC <0.1%

t-Butanol -dg GC ND

n - Butyl ami ne-dg GC ND

n-Butyric-d7 acid GC <1%

Chlorobenzene-dg GC ND

n-Decane-d22 GC ND

Diethyl ether-dit GC ND

Di-n-octyl ether-d 34 GC ND

Mono-n-dodecyl phosphate-d2 5 GC^ <2%

Ethanol -dg GC <1%

Hexamethy1 enetetrami ne-di 2 GC ND

Naphtha! ecM-de GC ND

2-Naphthalenesii!fonic acid-dy LC <1%

Ni trobenzene-dg GC ND

2-Phenyl ethyl -1 ,1 ,2,2-d4-amine GC NO

Phenol-ds GC ND

o-Xylene-dio GC ND

^As the tri methyl si lyl derivative.

ND = non-detected

4
Table 5

Isotopic Purity of Marker Compounds

No. of Deuterium Atoms

Present in Compound

Mole %

Atom % . Completely

Compound As Supplied After Exchange” Deuteri um° Labeled^

Acetonitrile-da 3 3 99.3 98

Acridine-dg 9 9 96.7 71

Anisole-2,4,6-d3 3 3 96.1 88

Anthracene-dio 10 10 99.4 94

Benzoic-ds acid 5 5 99.4 97

Bisphenol-A-di 4 16 14 98.6 81

Bromoethane-ds 5 5 99.3 97

t-Butanol-dg 10 9 99.5 94

n-Butylamine-dg 9 9 99.3 94

n-Butyric-dy acid 7 7 99.3 95

Chlorobenzene-ds 5 5 99.4 97

n-Decane-d22 22 22 99.4 87

Diethyl ether-dio 10 10 99.6 96

Di-n-octyl ether-d34 34 34 99.7 94

Mono-n-dodecyl phosphate-d2 5 25 25 99.4 85

Ethanol -ds 6 5 99.0 95

Hexamethy1 enetetrami ne-di 2 12 12 99.8 98

Naphthalene-ds 8 8 98.6 89

2-Naphthalenesulfonic acid-dy 7 7 98.6 87

Nitrobenzene-ds 5 5 99.0 95

2-Phenyl ethyl -1 ,1 ,2,2-d4-amine 4 4 99.2 97

Phenol -ds 6 5 98.5 92

o-Xylene-dio 10 10 99.4 94

^As used for spectra.

^For labeled positions after exchange.

5
Mass Spectra

Electron impact mass spectra at 70 eV were recorded for each marker

compound in the labeled form expected to be recovered from aqueous solution

with the exception of mono-n-dodecyl phosphoric acid-das which did not give a mass spectrum representative of intact material. The mass spectrum of mono-n- dodecyl phosphoric acid-d25 as the trimethyl si lyl derivative was recorded. The

complete mass spectra in both tabular and bar graph form are reported in NBS

Interagency Report 80-2160, "The Mass Spectra and Isotopic Purity of Compounds

Proposed for Use in the 'Master Analytical Scheme for the Analysis of Organic

Compounds in Water,'" by E. White V, M. J. Welch, and H. S. Hertz.

Procedures for the Preparation of Internal Standard Solutions

of Marker Compounds

"Purqeables" . A small serum vial (approximately 1 cm diameter x 2 cm

high)^ was weighted to the nearest 0.01 mg on a semi-micro balance. Approximately 6 mg naphthalene was weighed into the vial. A circle of aluminum foil was put over the top followed by a liner of Teflon bonded to silicone rubber.

An aluminum cap was crimped over these liners. The vial was weighed, 500 pL

methanol was added through the septum with a syringe, and the vial reweighed.

(A separate test of the weight loss of methanol was made under these weighing

conditions and it was found to be 0.01 mg/min.) The remaining compounds were

added by filling a syringe with the required volume, adding to the weighed

vial through the septum, and reweighing the vial and its contents. Least

volatile materials were added first. The order was decane, anisole, chlorobenzene, bromoethane, and diethyl ether. After all constituents were weighed

in, the solution was mixed.

The dilute solution was prepared by a weighed dilution of the concen- trated solution. A clean vial was capped as before, weighed, 450 yL of

methanol was added through the septum by syringe, and vial and contents

weighed. Then 50 yL of the concentrated solution was added, and vial and

^The small vials used for weighing were 1 mL Reaction Vessels, Cat. No. 3-3123,

Supelco. Since the vials were too long to be used easily for filling 1-yL

Microcaps, the vials were shortened from a length of about 3.2 cm to a length

of 2 cm.

6
contents reweighed and then mixed. The remaining concentrated solution was put into a clean glass ampoule and sealed until needed, at which time it was transferred to a small serum vial.

To ampoule either solution, the vial was capped with aluminum foil only,

1-pL Microcaps were filled with the solution through a small hole in the cap,

put into a melting point tube^ already sealed on one end, and then the re- maining end was sealed. Tweezers were used to handle the Microcaps.

In order to minimize concentration changes, the steps needed for

ampouling were done as rapidly as possible. It took 35 minutes to aliquot

and seal 100 samples.

The approximate amounts to be weighed for the preparation of the

concentrated solution were as follows:

The concentration data for the two sets, prepared in April 1980, by

the above procedures are shown in Table 1.

A total of 52 ampoules of Set No. 1 and 60 ampoules of Set No. 2 were

delivered. Additional ampoules were held at NBS for stability studies.

"Extractable" . Solutions for the preparation of the ampoules of

internal standards for "extractable" samples were made by weight. For each

set, solids were weighed and placed into an approximately 500 ml flask.

Liquids were weighed by syringe, weighing the full and empty syringe. The

required amount of methanol was added by pi pet and the amount added checked by

weight. After mixing the solution, 5 mL. amounts were dispersed with a MicroMedic automatic pipetter into 10 mL glass ampoules, which were then sealed.

^The melting point capillaries were cleaned before use. They were placed in

a clean separatory funnel, HPLC grade methanol was added to cover the tubes,

the tubes were filled by applying a vacuum, then inverted, refilled, and

emptied. This process was repeated. The tubes were then dried in a vacuum

oven at 7 Pa (0.05 mm Hg) and 140 °C, for 48 hours.

Naphthalene

Decane

Anisole

Chlorobenzene

Bromoethane

Diethyl ether

6.25 mg

6.25

mg = 8.56 yL

6.25

mg = 6.31 yL

0.62s mg = 0.56 yL

0.62s mg = 0.45 yL

6.25

mg = 8.83 yL

7
The concentration data for the two sets, prepared in May 1980, are shown

in Table 2.

A total of 68 ampoules of Set No. 1 and 54 ampoules of Set No. 2 were

delivered. Additional ampoules were held at NBS for stability studies.

"Intractables" . Solutions for the preparation of the ampoules of

internal standards for "intractable" samples were made by weight. For each

set, n-butylamine-ds and dodecyl phosphate-dzs were weighed first and dissolved in distilled water before the addition of the other labeled materials.

Liquids were weighed by syringe, weighing the full and empty syringe. The

required amount of water was added by pi pet, and the amount checked by weight.

After mixing each solution, 7.5 ml (Set 1) or 10 mL (Set 2) amounts were

dispensed with a Micro-Medic automatic pipetter into 10 mL glass ampoules,

which were then sealed.

The concentration data for the two sets, prepared in June 1980, are shown

in Table 3.

A total of 68 ampoules of Set No. 1 and 116 ampoules of Set No. 2 were

delivered. Additional ampoules were held at NBS for stability studies.

Stability of Marker Compound Solutions

Accelerated Aging Studies . Although the time between the final decision

on the constituents for the marker compound internal standard solutions and

the required delivery did not permit extensive stability testing, it was recognized that some of the compounds, when stored in the mixtures, might

react with other constituents or lose deuterium by exchange. As a consequence,

several test mixtures similar to the "extractable" and "intractable" internal

standards, but simplified and of undeuterated compounds in deuterated solvents,

were prepared and subjected to conditions to accelerate aging. These solutions

were examined by nuclear magnetic resonance spectroscopy. For the surrogate

"extractable" standard decreases in the concentration of hexamethylenetetra8
mine and phenol were observed, but the rates were such that properly stored

(0-5 °C) mixtures were expected to be usable for the several months required.

A surrogate "intractable" standard containing acetonitrile, dodecyl phosphoric

acid, butyric acid, and a tertiary amine base showed no change.

Stability . Ampoules from all six internal standard mixtures prepared

have been stored at 0-5 ®C. Selected ampoules are periodically removed and

the concentrations of individual components checked by gas or liquid chromatography. Initial results are encouraging, but the testing is not yet complete.

1 .b. Liquid Chromatography - Mass Spectrometry

Coupling liquid chromatography (LC) and mass spectrometry (MS) has most

widely been achieved by two methods. One operates by splitting off a small

fraction of the LC stream and introducing it directly into the high vacuum of

the MS. Another employs a moving belt onto which the stream is evaporated.

The belt then moves into the high vacuum region where the solutes are desorbed.

The interface which we are developing is an attempt to combine advantages

of both methods; the simplicity of direct liquid injection together with the

solute preconcentration of the moving belt technique. Preconcentration of the

LC stream is achieved by allowing it to flow down a heated wire where 90-

95 percent of the solvent is evaporated. A portion of the residual liquid is

admitted to the high vacuum through a probe which is, in essence, a miniature

needle valve. Our early efforts were concentrated on development of the

heated wire and its controls, and on the construction of a probe which would

give a steady, uniform spray of liquid droplets into the ion source of the MS.

A slightly unsteady or intermittent spray gives rise to very noisy signals

from the MS.

A patent application covering the device has been approved and a paper

describing it has been accepted for publication in ANALYTICAL CHEMISTRY. A

preprint of the latter is appended.

9
Normal -Phase LC/MS Experiments :

Encouraged by the stability of the spray of hydrocarbon solvents from the

LC/MS probe, we initiated experiments to make quantitative measurements. The

determination of phenol and o-cresol in shale oil ordinarily requires several

steps: extraction followed by GC or GC/MS quantitation. It was found to be

possible to quantitate these materials directly by LC/MS, using either external

standards or the method of standard addition, monitoring m/z = 94 (phenol) or m/z = 108 (cresols). One yL of undiluted shale oil was injected. Even with

so volatile a compound as phenol, it was found that the concentrator device

gave a six-fold concentration enhancement. Standard deviations of the determined values were about 10 percent, and the means were within about 10 percent

of the certified concentrations of about 400 ppm. A UV trace and single ion

record for the phenol determination are shown in Figure 1.

Reversed-Phase LC/MS Experiments :

Considerable difficulty was encountered in getting droplets to detach

from the probe tip when solvents containing large concentrations of water were

used.

In an attempt to get a more uniform spray of water-containing solvents, a

rvew probe was constructed. This used a threaded cap to retain a replaceable

seat against the end of the probe. The orifice was formed by allowing a tungsten wire to pierce the seat material. Seats tried were aluminum and gold

foils, mylar, teflon, TFE-IOOX, Kapton, and poly(vinylidene fluoride). The

latter seems to have the most satisfactory mechanical properties.

Owing to the high surface tension and high heat of vaporization of

water, it does not explosively vaporize into the vacuum as do the hydrocarbon

solvents. Also, our design does not permit application of increased pressure

to the stream to impart sufficient momentum to detach droplets. Therefore, a concentric tube was added through which a nebulizing gas (e.g., argon or methane) could be passed. With this system, it was possible to get molecular

10
Ion

Intensity

UV

Absorbance

i

I

L

I

[

r

r

I

r

r

0 10 20 30 0 10 20 30 40

Time, minutes

Figure l Chromatogram of shale oil obtatned during phenol quantitation. t Upper trace; ultraviolet detector recording at 254 nm. Lower

trace; single ton record at m/z 94.

11

f
ions of the non-volatile compound adenosine. This apparatus is shown in

Figure 2.

The results obtained from these experiments were encouraging, but not optimum

for this system. A number of experiements with the LC/MS probe were planned

for the near future; however, timely implementation of these plans may be

hampered due to lack of funding.

1 .c. Liquid Chromatography with Electrochemical Detection (LC-EC)

Research emphasis in this past year has been focused on the development of new chromatographic separations and the optimization of the

electrochemical detector response.

Following a literature survey by A. Cohen (NBS/CAC), the electroactivity of over 30 currently used organic pesticides was investigated

using current-sampled polarography to provide a basis for their electrochemical detection. A chromatographic separation of six frequently

encountered pesticides (including parathion and guthion) has been developed (see Figure 3 ).

Many possible separation conditions have been evaluated for the

separation of the cationic organotin species, employing such methods as ion exchange and reverse-phase chromatography in the presence of com- plexing agents. Little success has been obtained in this laboratory,

but Brinckman and Jewett have developed a separation for the mono- cationic species, and this separation was used to evaluate the electrochemical detection approach. The amperometric detection of tri phenyl tin

cation was complicated by the formation of an electrode deactivating

film of hexaphenylditin. This problem was overcome using pulsed detection

wave-forms which take advantage of the electrochemical reversibility

of the reduction (see Figure 4).

12
New

orobe

for

concentric

admission

of

atomizing

gas.

The

dianhragms

(shaded)

are

of

noly(vinylidene

fluoride).
SEPARATION OF SOME INSECTICIDES

Column: Spherisorb ODS, 5 pm, 4.6 x 250 mm

Soluent: 60% Me0H/H20 , 0.12 mol/L NH4OAC

1.5 mL/min

Detector: Amperometry, -0.85 V, HMDE

Sample: 20 pL of 10'® mol/L (about 3 ppm) of each

DNOC

I I

M-Parathion

+

M-Guthion

Fenitrothion

E-Guthicn

T

10. nA

1

E-Parathion

i I I I I I I I Inject 2_4 6 8 10 12 14

Minutes

Figure 3 . Reverse-phase Insecticide separation employing amperometric

detection.

14
Amperometric

Detection

-0.80 V

Pulse

Detection

-0.65 V, 150 mV pulse height

0.5 s Pulse Period

1

20 nA

i

Differential Pulse

Detection

-0.65 V, 100 mV pulse height

0.5 s Pulse Period

Inject I I I I I 246 8 10

Minutes

Figure 4

• Detection of tri phenyl tin cation using different detector

wavefor.ns.

15
A comparison has been made of several materials for the working

electrode of the detector cell. A dropping and hanging mercury electrode

cell, as well as several solid-electrode thin-layer cells (based on mercury-coated gold, platinum, and glassy carbon), were evaluated for

their negative potential range and detection limits for reducible

organic pesticides. A manuscript on LC-EC has been submitted to Analytical Chemistry.

Development of a High-Sensitivity Dual -Electrode Detector for

Liquid Chromatography

Reductive electrochemical detection in liquid chromatography (LC)

is potentially a very powerful measurement technique in the determination of trace organic pollutants by virtue of its sensitivity and

selectivity. However, for the best sensitivity, oxygen exclusion is

required. This makes the technique cumbersome to use and has restricted

its application.

A new approach for reductive LC detection that eliminates the need

for complete oxygen exclusion has been developed. A two-electrode,

thin-layer cell is used in a manner conceptually similar to a ring-disc

system. Two closely spaced electrodes are poised at different potentials. The first electrode encountered by the flowing electrolyte is

held at a potential sufficiently negative to reduce the analyte. The

second detector electrode is held at a potential sufficiently positive

to reoxidize the generated species and also to avoid the reduction of

oxygen. The low residual current at this potential assures a low

background noise, upon which the analytical current is easily measured

with high sensitivity.

The best analytical response is obtained for analytes that either

are reversibly reduced or that have chemical followup reactions that

generate easily oxidized products. The reductive/oxidative behavior of

16
three important industrial /environmental pollutants - nitrobenzene,

di chi one, and tri butyl tin - have been studied by reverse pulse voltammetry.

The sensitivity and linearity of the dual electrode technique has

been evaluated by comparison to direct reductive detection. Two chromatograms

with equal concentrations are pictured in figure 5. The baseline noise

of direct reductive detection without use of an inert atmosphere box is

apparent (upper figure). The lower chromatogram shows the very low

baseline noise of the dual electrode approach achieved with a minimum of

difficulty.

Current experiments involve the evaluation of the technique's

selectivity by application to the measurement of organic analytes in

environmental samples. Also, investigation is in progress on the use of

modulated waveforms and phase selective detection to improve selectivity.

1 .d. Interferences in the Inductively Coupled Plasma (ICP) Technique

In the application of the ICP technique to high-accuracy analysis of

Standard Reference Materials (SRM's), interferences have been found which

can degrade the quality of analytical results. These interferences can be traced to spectral and matrix- related interactions which must be

characterized and corrected for in order to minimize their effect. The

problem of spectral interference in the ICP technique is well known.

Procedures for background and spectral overlap corrections have been

established and are presently being employed in this laboratory. The

first step is to expose a photographic plate with spectra of the sample

and pure-element standards. Spectral lines are then chosen from con- siderations of sensitivity and absence of spectral overlap. The exitslit carriage is mounted on the microdensitometer with the reference

photographic plate, and slits are positioned in alignment with the chosen

lines on the plate. Final alignment is accomplished by adjustment of

a refractor plate in front of each slit.

17
Oxidation at + 0,CS V

(Second Boctrcds)

t 1 nA

<§>-NO:

0

- 2.3 nA i! i i OHsel pvr-ri ,

}

4 8 121620

inia/'f on.ii Minutes

Cl

Cl

of 10'* mol/l

Different Reductive Detection Modes. Conditions; .^ra'/ces1.3 X IC"^ Jiol/L of nicrocenzene and dichlcne; Soi'/ent--cC

percent MeCH/H 2Q, 3.1 .-nol/L NHuOAc pH 3.2 at 1.0 TiL/m'nuta;

Column—Whatnan Partisil RXS 3 um. Uoper figure—ci rect '•edi. ti'/e detection at -G.3 7 without enclosure of the .C in >n inert atmosphere box. Lower figure--dual electroce :etect::n

-0.3 7 on generator electrode, -0.C8 7 on detector :lectrode.
A wavelength scan of each element is stored in the computer for output

on the terminal. From plots of intensity-versus-wavelength for each

element, the spectral peak position is checked and background correction

points on either side of the peak are chosen. Spectral scanning and

background sampling are accomplished by computer-controlled rotation of

a refractor plate positioned behind the spectrometer entrance slit. In this manner, true net intensities for the spectral lines are calculated

and either stored in the computer for calibration or displayed on the

terminal

.

Evidence has been found indicating differences in analytical response

between pure-element standards and samples of complex matrices which are not due to spectral interference. These effects become significant when

applying the ICP technique to high-accuracy analysis of SRM's. Chemical

matrix effects in the plasma itself can cause up to fifteen percent relative enhancement or depression of the analyte element intensity depending

on the spectral line and plasma operating conditions. Complete definition

of the problem has involved examination of compromise conditions for

simultaneous multielement analysis both from the point of view of sensitivity as well as matrix effect suppression.

One way to estimate a suspected matrix effect is to record net intensities

for various elements at constant concentrations, with and without an excess (3000 yg/mL) of potassium present. The ratio of intensity with

potassium to intensity without potassium can be plotted with respect to an instrument variable such as power, or observation height. The objective

is to find operating conditions which result in a ratio close to 1.00

without significantly affecting the signal-to-background ratio. At

present, no serious degradation in signal-to-background ratio has been

caused by tuning the ICP for minimum matrix effect. However, the data

include only five elements thus far; therefore the results must be

considered to be preliminary. These data, as well as extension to

additional elements and matrices, will provide the information necessary

to minimize analytical bias in simultaneous multi-element analysis using

the ICP techniques.

19
1 .e Metal Speciation Using High Performance Liquid Chromatography/Atomic

feorption Spectrometry

During recent years it has become increasingly apparent that total metal

data alone may not provide complete and accurate descriptions of the

complicated roles which many metals play in our ecosystem. It is generally

believed that alkylated forms of certain metals (e.g., Hg, Pb, and Se) are much more toxic than the inorganic salts of the metals or even the

metals themselves. Some microorganisms are capable of chemically

and biochemically transforming certain toxic elements into more toxic

organometallic compounds which may then be released into the environment.

Additionally, chemical speciation of trace metals can be a real problem

in defining nutrient composition of foods because the biological activity

of a metal such as chromium or iron depends on the chemical species to

which the metal is bound.

The rapidly increasing interest in metal speciation in diverse scientific

disciplines has prompted the inmediate need for development of analytical

instrumentation which allows the determination of not only the total

metal content but also the different chemical forms in which the metal

may be distributed. Atomic spectrometric techniques (absorption, emission,

and fluorescence) have long been regarded as being sensitive and metal

specific spectrochemical technqiues for total metal analyses are limited

in their ability to differentiate between various chemical forms of the

metal within the sample. Chromatographic techniques can be successfully

employed to separate various chemical forms of the analyte, but poor

detector specificity frequently limits their analytical utility when

highly complex mixtures are encountered. However, interfacing chromatographic and atomic spectroscopic instrumentation into a single analytical

hybrid system which has the combined advantages of both techniques

presents a viable means of potentially solving analytical problems which

otherwise would not be possible by either individual technique.

20
In an effort to gain more knowledge about the metal distribution in

complex matrices, an investigation has been undertaken using the com- bined instrumentation of a flame atomic absorption spectrometer interfaced to sample the mobile phase exiting at the outlet of the analytical

column of a high performance liquid chromatograph (HPLC). To demonstrate

the analytical feasibility of HPLC/AAS for molecular characterization of

metals in complex matrices, tetraalkyl lead (TAL) compounds were determined directly in gasoline. Baseline resolution of the TAL mixture con- sisting of tetramethyl lead (TML), trimethyl ethyl lead (TMEL), dimethyl

diethyl lead (DMDEL), methyl triethyl lead (MTEL), and tetraethyl lead

(TEL) was effected by reverse-phase HPLC using a 70 percent acetonitrile

(CH3CN)/30 percent H 2 O mobile phase. The eluted tetraalkyl lead species

were then sequentially atomized in an air/ acetylene flame. The lead

absorbance for each TAL compound was measured by atomic absorption

spectrometry using the 283.3. nm lead resonance line. Analyses were

conducted free of spectral interferences. Detection limits for lead by

this hybrid technique were about 10 ng for each TAL compound. Using our instrumental configuration and analytical conditions, the 5 tetraalkyl

lead compounds were separated and detected in less than 10 minutes. A

number of different commercial gasolines were analyzed for their tetraalkyl lead content. The TAL distribution was found to vary widely among

manufacturers.

Atomic absorption spectrometry has been compared in terms of analytical

performance to UV absorbance spectrophotometry as a detector for HPLC

for the determination of tetraalkyl lead compounds in petroleum refinery

products. Preliminary data indicate that for certain applications the

metal -specific AA detector is more analytically useful as an HPLC

detector than UV absorbance spectrophotometry for the study of different

metal species in complex matrices. In some cases, the UV absorbance

detector is severely plagued by spectral interference at 254 nm due to

coeluting aliphatic, olefinic, and aromatic hydrocarbons of the gasoline

matrix which absorb at this wavelength. As shown in figure 6, a clean

chromatograph of tetraalkyl lead compounds in gasoline is obtained with

21
Direct Determination of Tetraalkyl Lead

Compounds in Gasoline by Reverse-Phase HPLC

UV Absorbance Detector

(254 nm)

Flame AA Detector

(283.3 nm)

DMDEL

Figure 6

22
the AA detector because it responds to only lead-containing compounds at

the 283.3 nm line.

In order to improve the analytical performance of the HPLC/AAS system

described in this preliminary report, it is necessary to optimize the

chromatographic conditions and to decrease the dead volume present

between the column and the detection system. In addition, the detection

limits can be significantly lowered by using a flameless atomic reservoir.

The HPLC/AAS technique can be easily extended to the determination of

different organometallic compounds in diverse matrices by simply tuning

the monochromator to the analytical line of the metal of interest. This

inherent specificity of AAS cannot be realized by existing commercial

HPLC spectroscopic detectors. Moreover, the specificity of AAS considerably

relaxes the constraints of the analytical conditions required for the

separation. With AAS, only the compounds containing the metal of

interest need to be separated from one another; the metal -containing

compounds need not necessarily be separated from the sample matrix.

1 .f . Sulfur Speciation in Coal

This methodology is based on the measurement of the characteristic

vaporization temperatures at atmospheric pressure of the various forms

of sulfur, using plasma emission spectrometry to monitor each vaporized

sulfur species. The resulting spectrometric thermogram consists of a series of relatively broad peaks, each peak being a different sulfur

species.

For this experiment, the 190.027 nm sulfur atomic emission line was used

with a HTV R-919 photomultiplier tube and a one-meter monochromator with

air purging. This system, using the 190.027 nm line can detect 100 yg of

sulfur. If air is purged and the 182.625 nm line is used, the detection

limit can be lowered to 5 yg. Previously, three sulfur species in coal

I
have been reported in the literature, pyritic sulfur (FeSa), sulfate

sulfur (FeSOn), and an "organic" sulfur. In the present experi Bents,

sulfur and iron emission intensities were monitored as a function of

temperature.

From these experiments, four sulfur species have been found,

Fe$2 » FeS0i»» organic sulfur, and a low evaporation temperature sulfur.

This low evaporation temperature sulfur starts to evaporate at 28 ®C.

SRM 1635 Western Coal has been found to contain about 18 times more of

this species than SRM 1632a Penn Coal. Also, organic sulfur has been

found to be linked with iron. In a previously described analytical

techni^e, organic sulfur was calculated by substracting pyritic and

sulfate sulfur from the total. Therefore, the value obtained from the

"organic" sulfur species included the low evaporation temperature

sulfur. In the future, an attempt will be made to identify the chemical

forms of these species using thermal separation and a cold trap collection technique. Also, an investigation will be undertaken in which

two monochromators are used simultaneously to detect both sulfur and

iron or any other elements which may be bound with sulfur.

Sulfur species analysis still needs work on the development of a standardization procedure, but it is a simple technique and has potential

for the direct determination of each species present.

l.g. Ionic Chromium Speciation Measurements

An anion-exchange method has been developed for the separation of

tri valent and hexavalent forms of chromium in synthetic aqueous solutions. The aqueous sample is made IN in HCl and is then Introduced onto

the anion-exchange column. In a IN HCl medium, Cr (III) elutes from the

column while Cr (VI) is adsorbed by the active sites of the anion24
exchange resin. After Cr (III) has eluted from the column, a solution

of IN ascorbic acid in IN HCl is added to the column which then reduces

the Cr (VI) species to Cr (III) species directly on the column. The

newly-formed Cr (III) species are then eluted from the column as in the

first part of the procedure. Atomic absorption spectrometry is used for

on-line detection of the chromium species as they elute from the column.

The aspiration uptake capillary of the AAS nebulizer is replaced by a Teflon microsampling cup. The anion-exchange column is positioned so that the eluent drops directly into the microsampling cup for continuous

nebulization and atomization of the sample. A chromatogram which

illustrates the direct speciation of tri valent and hexavalent chromium

by ion exchange-atomic absorption spectrometry (IE- AAS) is shown in

Figure 7.

Figure 7

25
81-BCK-b-ENERGY RELATED WATER POLLUTANT ANALYSIS INSTRUMENTATION

2. Development of Measurement Methods for Non-Volatile Organic

Pollutants in Water Due to Energy Technologf^

2. a. Fluoroimmunoassay Procedure Developed for Dinitrophenols in Water

Detection of trace amounts of the toxic pollutant 2,4-dinitrophenol

in water is an analytical problem that presents many challenges to the

analytical chemist. Laboratory investigations have shown that gas

chromatography and high-performance liquid chromatography, while suited

for analytical determinations of most of the toxic pollutants, are not

as efficient in the separation and identification of the ni trophenols.

The development of an immunochemical procedure for detection and quantitation of dini trophenols in water has been the focus of efforts during

1980.

In developing a model system for detection of priority pollutants such as dini trophenols (DNP) in water, we prepared conjugates of DNP by reacting

proteins, 2,4-dinitrobenzenesulfonic acid, and K2CO3 in aqueous solution.

The extent of conjugation was calculated by optical density measurements at

360 nm, using 17,350 at pH 7.4 as the molar extinction coefficient for DNPlysyl residues.

Selected conjugates were injected in rabbits at monthly intervals beginning

in February 1980. Antibody response was measured versus homologous conjugates

in a micro-double-gel diffusion slide system by observing the precipitation

lines developed in the agar matrix. The rabbits were finally bled 25 weeks

after initial irminization via cardiac puncture for optimal yield of serum.

Antibodies in the form of immunoglobulin G (IgG) were obtained from serum

by use of a beaded, cross-linked agarose gel to which Cibicron Blue F3GA dye

and diethyl ami noethyl groups are attached. In this procedure, buffer-equilibrated serum was passed over a packed column (2.0 cm x 18 cm) of the gel.

26
Protease-free IgG was obtained as the first peak eluted with a wash of the

starting buffer. To obtain a specific solid-phase binding reagent for assay

purposes, the purified IgG was covalently bound to hydrophilic polyacrylamide

beads, 5-10 ym in diameter.

For assay purposes, we have focused our research efforts on fluorimmunoassay rather than radioimmunoassay. The use of a fluorescently-labeled ligand

in a fluoroimmunoassay has the advantage of longer shelf life, less expensive

instrumentation, ease of counting, and less stringent disposal procedures. In fact, the use of fluorescence labels in immunoassays has the potential to

replace many existing radioimmunoassay procedures. The fluorescent ligand we

first used in the assay system was a complex of 2,4-dini trobenzenesulfonic

acid and 5-[(4,6-dichlorotriazin-2-yl )-amino]fl uorescein hydrochloride. While

having adequate fluorescent activity, specific binding was low. More recently,

labeled ligands have been developed by (a) reacting 2,4-dinitrobenzenesulfonyl

chloride with fluorescein isothiocyanate (FITC) in anhydrous pyridine and

isolating the reaction product by exclusion gel column chromatography, or

(b) double labeling of RSA with DNP and with FITC.

Characterization of ligand (a) is still in progress, while ligand (b) has

been successfully used in a competitive binding assay. Current detection

limits are at the 100 microgram/L level for DNP in water. To be useful in

pollution analysis, sensitivity must be in the submicrogram/L level. Sensitivity of this order has been established for immunoassays in clinical use. By combining the specificity of the assay with capabilities of concentrating

dinitrophenols with an affinity "accumulator" column, detection of ultra- trace

amounts of dinitrophenol pollutants in water should be achieved. This will

be of importance in the monitoring of industrial effluents.

27
2.b. Development of a Fourier Transform Infrared Spectrometer-Gas

Chromatograph Interface and Its Application to Pollutant

Identification

Installation of a Nicolet 7000 Fourier transform infrared (FTIR)

spectrometer was begun in September 1979, and essentailly completed by

January 1980. The instrument was found to meet all design specifications and even exceed some, such as resolution and signal-to-noise

ratio. The instrument is being used for four distinct research and/or

service functions: high-resolution low-pressure gas work, liquid samples,

liquid chromatography, and gas chromatography.

The studies of gas chromatographic applications have progressed

through the utilization of packed column chromatography to the construction

and testing of an interface for wall coated open tubular gas chromatographic

columns (WCOT), which will allow real-time FTIR analysis of compounds

eluting from the WCOT. The use of packed columns was not pursued

because they were not found to have the resolving power required for the

separation of the complex samples we wished to analyze. The WCOT columns

used in this project were chosen to maximize sample capacity of the

column, since the FTIR instrument requires MOO ng of component for the

collection of a reasonably identifiable spectrum. Also, an on-column

injector was fabricated to facilitate injection of a maximum amount of

sample onto the column without undue loss of efficiency. The first

interface design consisted of a Pt/Ir tube which connected the output of

the thermal conductivity detector (TCD) to the FTIR light pipe. This

interface was found to be unsuitable because too much dead volume (located

mostly in the TCD and connecting fitting) caused unacceptable peak

broadening. In addition, the Pt/Ir tube thermally trapped out and/or

reacted with all solutes boiling above 300°C.

The present interface consists of a 50 cm length of deactivated,

methyl silicone-coated quartz capillary of 0.15 mm internal diameter.

The TCD has been bypassed and no other gas chromatographic detectors are

28
used. This interface is connected to a glass WCOT by use of AgCl

cement; if a quartz WCOT were used, then the last 50 cm of the capillary

itself could act as the interface. The quartz interface does not appear

to react with or retard eluting compounds and spectra have been obtained

for compounds such as methyl di benzanthracene (b.p. <500 °C). Reconstructed gas chromatograms (from IR data) still show large losses in

efficiency over those obtained from normal gas chromatographic detectors. This loss is most likely due to the large volume of the FTIR

light pipe, and a new low volume light pipe is being procured. Even

though the FTIR data does not fully reflect the high-efficiency separations obtained on the WCOT columns, very recognizable and identifiable spectra are being obtained from environmental samples being

analyzed (e.g., phenols in shale oil, PCB's, etc.). This is, to a large

extent, being made possible by some newly developed manipulative com- puter software which numerically regains some of this lost column

efficiency.
81-BCL-a-ENERGY RELATED POLLUTANTS AND EFFECTS MONITOIRNG AND

ASSOCIATED METHODS AND TECHNIQUES DEVELOPMENT

1 . Development of SRM's for Stationary Sources Associated with Energy

Production

1 . a . NOq in Air Gas Blend SRM's

The analytical work necessary to establish the feasibility of nitrogen

dioxide in air mixtures as Standard Reference Materials has not been

completed. The areas in which work must continue are related to the

assignment of accurate values to the concentration and to the length

of the period of certification. Measurement of the concentration of

all samples on a relative basis has been completed but the final absolute

value has not been assigned pending further work. It appears that most

samples are stable and if further analyses confirm the overall stability

a certification period of one year will be assigned to these gas mixture

SRM's.

There are virtually no accurate methods of analysis for NO

2

which

result in concentration measurements uncertain to less than ±1% relative.

Consequently, a considerable effort was expended to relate the concentration of NO

2

in these samples to the concentration of well characterized

standards containing similar concentrations of NO. A double catalytic

converter was assent)! ed which appeared to give stable consistent ratios

of conversion of NO

2

to NO. If it could be assumed that conversion in

the second converter in series was 100% efficient then a direct comparison

could be made between NO standards and the samples containing NO

2

. However, this assiimption cannot be made without confirmatory evidence.

We have established that if the conversion in the second converter is

less than 100% it isles by a constant percentage of the NO

2 entering

the system. This was confirmed by comparing the concentration of NO

2

measured by a UV photometric method with that measured by conversion to

NO and analysis by chemiluminescence. In the case of both instruments

the relationship between samples was identical within the combined

30
uncertainties of the two methods. The table below relates the observed

concentration of each sample to sample 1 for each method of analysis

and is expressed as the ratio of the signal measured for each sample

divided by the measured signal for sample 1.

Ratio of Sample Signal to Sample 1 Sample Chemiluminescence UV

1 1.000 1.000

2 .425 .425

3 .217 .217

4 .109 .108

All of the 250 ppm and the 1000 ppm samples were reanalyzed approximately

one year after the first analysis. The data for the 250 ppm samples

indicates that only one sample out of 50 has changed by more than 1%

relative. This one sample appears to have decreased about 2% relative.

However, the results for the 1000 ppm lot show a number of samples to

have either increased or decreased in concentration but in no case by

more than 1% relative. It should be noted that while more variability

was observed with the 1000 ppm samples it does not necessarily follow

that these samples are less stable. The precision with which a sample

can be analyzed is roughly ±2 ppm. Thus at the 1000 ppm level a relative

change of 0.2% could be recognized but at 250 ppm a relative change of

this size would not be apparent.

At this time it appears that it will be possible to assign an accurate

final concentration to each sample but the uncertainty will be somewhat

greater than with the less reactive gaseous SRMs. We estimate that the

final total uncertainty with which the 250 ppm samples will be certified

will be ±3% relative (7.5 ppm) and that at 1000 ppm it will be ±1% (10 ppm).

The analysis of NO

2 by chemiluminescence requires a very long equilibration time if the sample lines are exposed to atmospheric moisture such

31
as occurs when samples are changed. For this reason and because of the

reactivity of NO

2

toward other parts of the COGAS system it was decided

that attempts to automate the analysis would be fruitless. Consequently,

a special sample manifold was constructed to facilitate the manual

analysis. The system consists of a "spider" to which 5 or 6 samples can be attached. The spider and associated tubing which connects the spider

to the instrument are flushed with gas containing a concentration of NO

2

similar to that of the samples to be analyzed. It is then sealed and

not exposed to the atmosphere until analysis of the 5 or 6 samples has

been completed. This procedure has reduced the equilibration time

considerably and has reduced the amount of sample needed for analysis.

The remainder of the samples, 500 and 2500 ppm will be analyzed by

January 31, 1981. Following this step, the data for all samples will

be examined and the final decision necessary for issuance on SRMs will

be made.

l.b. SOo in No SRM's

Two new SRMs consisting of 50 and 100 ppm nominal concentration of

sulfur dioxide in nitrogen are nearing completion. Each SRM will

consist of 50 samples each. The analysis of the 50 ppm samples has been

completed and the analysis of the 100 ppm samples will be completed by

the end of 1980.

The use of an automated analytical system (COGAS) for the analysis of

these samples was not attempted. Preliminary results using an instrumental method (NDIR) suggested strongly that problems due to adsorption

of SO

2 on the stainless steel parts of COGAS could lead to erroneous

results. Considerable investigation of the problem was anticipated

and it was decided to analyze each sample manually in which case the

problems of adsorption could be minimized. However, when these SRMs are completed the use of COGAS will be investigated using a small number

of the analyzed SRMs.

32
The final concentration of the samples in the 50 ppm lot cover a range

of about 1 ppm (2% relative) and at this time there is no evidence of

instability of any samples in the lot. The range of concentration in

the 100 ppm lot is about the same on an absolute basis (1 ppm) but

smaller on a relative basis (1%).

The final uncertainty to be assigned to each sample in the 50 ppm lot

will probably be about 2% relative. This value is based on the uncertainty

of the chemical method used to analyze the reference sample and on the

imprecision with which this reference sample is compared to each sample

in the lot. The uncertainty of the 100 ppm lot is expected to be smaller

than that of the 50 ppm lot. It is not likely that the uncertainty of

the 50 ppm level can be reduced significantly. Several techniques were

investigated including gas chromatography, precise dilution and measurement with a flame photometric detector and non-dispersive infrared

measurement (NDIR). Measurements by NDIR was found to be the most precise

but because of the relative insensitivity of the technique to SO

2

the

results at 50 ppm probably represent a practical lower limit for analysis

of SRMs.

The material for a new SRM (SO

2

in N

2

, 3500 ppm) has been ordered and is

in preparation. Analysis of a reference sample to be used by the com- mercial supplier has been completed and delivery of the lot of 50 samples

should occur before the end of 1980. Previous analytical experience

with concentration of SO

2

of 2500 ppm suggests the absence of any significant analytical problems at the 3500 ppm level and further suggest that

a certification to ±1% relative will be feasible.

It is planned to issue these as SRMs by June 30, 1981.

1 . c . NO in No SRM's

SRM's have been issued for 1500 and 3000 ppm NO in N

2

.

33
1.

d. Oo in No SRMs

C

All work is complete

Two SRMs consisting of 2 and 10% oxygen (SRM 2657 and SRM 2658) in nitrogen

are now available.

2. Development of SRMs for Monitoring Ambient Air Impacted

by Emission Resulting from Energy Production

2. a. COq in Air SRMs

Specifications were developed and a commercial supplier is currently

preparing three lots of 50 samples each at approximately 320, 330, and

340 ppm carbon dioxide in air. Work has been completed on the analysis

of the air with which the samples will be prepared, to assure that the

composition in terms of both the major and trace constituents is identical

to "normal" air.

2.b. Automation of Gas Analysis

A third system (C06AS-III) has been constructed for the automation of

permeation tube calibrations. Preliminary results indicate that the

system will operate as intended.

Under a separate program with the Motor Vehicle Manufacturers Association,

ten new carbon monoxide in nitrogen mixtures were developed involving

measurements which demonstrated the usefulness of high-pressure injection

from large sample loops into a gas chromatograph to increase detector

response for carbon monoxide mixtures at concentrations of less than 100

ppm. The technique allowed the intercomparison of samples with standards

with a precision of ± 0.2 percent. Certification of these SRM's involved

the first test of the software used to control the combined gas chromatography

NBS-developed computer operated-gas analysis system (COGAS). COGAS had

previously been used only with continuous flow gas analyzers.

34
2.C. npvpinpmpnt of a Traceability Procedure for Gas Standards

The demand for gas standards is increasing at an accelerated rate.

Improvement in instrumentation during the last two decades and mandated

requirements for accuracy in gas measurements related to environmental

concern have both contributed to the demand. Limitations imposed on the

gaseous SRM program resulted in severe shortages of standards which on occasion has caused concern among regulatory agencies, users and producers. Since it is not realistic, either philosophically or physically,

to consider expanding the gaseous SRM program beyond its present bounds,

it has become essential to establish some alternative supply of accurate

standards. As a result of this need a protocol has been developed which

in essence transfers the responsibility for producing large numbers of

accurate standards (Certified Reference Materials) to the specialty gas

industry. The protocol makes provision for monitoring by the regulatory

agencies and at the same time NBS retains the responsibility for assuring

traceability of the Certified Reference Materials (CRM's) to NBS gaseous

SRM's.

According to the protocol, the specialty gas producer will prepare

CRM's at concentrations equal to or very close to the concentration of

existing SRM's. These will be prepared in large homogeneous batches.

The producer will analyze each CRM from the batch by comparison to an

SRM. The regulatory agency will select samples from each batch for

analysis. The analysis by the regulatory agency will be performed using

SRM's as cal i brants. Both the producer and the regulatory agency will

furnish NBS with complete information concerning the production and

analysis of the CRM's including the data for both calibration of the

instruments used and the analysis of the CRM's. NBS will then statistically

compare the results reported by the producer with those found by analysis

by the regulatory agency. In addition, NBS will examine all the results

reported by the producer to ascertain the homogeneity of the batch.

From these data it will be possible to verify the total uncertainty of

the concentration claimed by the producer. At this point the concerned

35
parties will be notified that the particular batch of CRM's has been

prepared in accordance with the protocol and that the stated concen- tration is correct within the defined limits of uncertainty.

The protocol in its present form has been extensively modified in

response to comments from the gas industry, users of SRM's and the

principal regulatory agency, the Environmental Protection Agency. It is

not a "cook book" by which CRM's can be prepared. Rather, it recognizes

the experience and expertise of the specialty gas industry while at the same time it recognizes the reservations which the user may have re- garding the industry and which the industry may have regarding the

regulatory agency. It is expected that the role of NBS as an independent

overseer will inspire confidence not only in the quality of the CRM's

but in the integrity of the entire procedure.

The availability of CRM's should moderate the demand for the

corresponding SRM's, so that the latter would be used largely as primary

standards, which was the purpose for which they were originally produced. A document has been prepared for publication under the Interagency Energy-Environment Program, entitled "A Procedure for Establishing

Traceability of Gas Mixtures to Certain National Bureau of Standards

Standard Reference Materials".

3. Develop Methods for Dispersal of Particulates on Filter Media

and Methods for Determining and Controlling the Composition

and Morphology of Such Dispersed Particulates

3. a. Thin Glass Films Produced by Focused- Ion Beam Sputtering

X-ray fluorescence spectrometry has proven to be a versatile and rapid

method for multielement analysis in many analytical applications. Of

particular interest are substances which can be analyzed in the form

of a deposit on a filter, mesh or membrane, or as a thin pressed pellet.

Collected airborne particulate matter, particulates in waste water and

36
geochemical samples are just a few examples of this type. In some respects such "thin samples" are ideal for x-ray fluorescence analysis

because the detection limits are suitably low and interelement effects

such as x-ray absorption and/or enhancement are negligible. The absence

of any sizable interelement effects makes possible a linear instrument

response to element mass per unit area. Spectrometer calibration for

analysis of such samples is usually performed with thin samples containing

known concentrations of the analyte(s) of interest. Some problems

associated with the "thin specimen model" are x-ray self-absorption in

particles (notably for the light elements such as A1 , Si, P, and S)

commonly referred to as particle-size effects, and self-absorption in

the substrate. Both of these effects require the application of correction

factors. Therefore, the basic premise is that accurate multielement

analysis of thin samples can be performed based on the thin specimen

model, together with empirical or theoretical correction factors.

There are several important criteria which need to be met if thin

samples are to be acceptable for calibration purposes. First, the

uniformity of the sample as well as its homogeneity must be within an acceptable well-defined tolerance limit. If the sample contains particulate matter, both the size and distribution should be characterized.

Secondly, the mass loading of the sample must be known to an acceptable

degree of accuracy. And finally, the sample should possess sufficient

durability and integrity.

The goal of a joint program between NBS and the U.S. Environmental

Protection Agency (EPA) was to perform the research and development

required to produce thin standard samples especially useful for calibration of x-ray fluorescence analysis of collected airborne particulate

matter. For this purpose we have investigated several candidate methods

for preparing such samples.

One method which shows great promise is the deposition of thin

films of glass containing known concentrations of several elements of

interest on polycarbonate substrates bv a technique known as focused

37
ion-beam sputtering. Ion-sputtering essentially involves the transfer

of atoms and/or molecules from a target to a substrate by the action of

an ion beam (usually argon) incident upon the target. The ion beam is

accelerated at high potential (700-1100 volts) with a flux of about 0.5

mA/cm^ toward the target at a 45° angle. Since the substrate is not in

the plasma environment, substrate damage does not occur. This is a distinct advantage of this particular sputtering technique. Other

advantages to be gained are: (1) production of thin films from synthetic

materials such as glasses of known elemental composition which can be

varied as desired; (2) high adherence of the glass to the substrate

which obviates the need for overcoating to maintain sample integrity;

and (3) easy control of the glass mass loading on the substrate by

variation of the sputtering time.

Several studies were performed with glass targets fabricated at NBS

which allowed up to eight 47 mm substrates to be coated at one time.

Instrumental parameters such as ion acceleration voltage and ion current

were systematically varied to determine their effect on film composition.

It was found that rather severe changes in these parameters often do not

affect the film composition by more than ± 15 percent. Glass films

sputtered from targets containing phosphorous and sulfur were also

prepared to demonstrate the feasibility of preparing films containing

elements of low atomic number.

In Table 6 are sunmarized the elemental compositions of three sets

of films at mass loadings ranging from 167 to 185 yg/cm^ which were

prepared at various times. These data demonstrate that the compositional reproducibility of thin films from set to set is satisfactory for

the purposes of preparing standard films.

Multi-element thin standards suitable for calibration purposes can

be fabricated by the focused ion-beam sputtering technique. In order to

include all the elements of interest in any particular film, several

glass targets would need to be fabricated. It is believed that these

films would be useful to monitoring agencies such as EPA for assessing

environmental impact of airborne particulate matter. Work is now in

progress to prepare several sets of films which will be certified by the

Office of Standard Reference Materials as NBS Standard Reference Materials.

38
Table 6

Composition

of

Glass

Films

at

Higher

Mass

Loadings

cvi O

jO

CM• O

O

flj

•M +1

H -H

C

0) 0 U3 C •cr r>. 0 VO VO CM CM • r— CM 0

i- a. CO CO VO VO VO to VO VO VO VO' VO VO ir> VO VO VO

<u r— f—•r— * F— «— f—•r— f—

cx.

ja Xi

r—•CM • • • 0 0 0 4-> c +1 +1 H

<u 0u c CO CO 10 CO VO VO VO CTi VO VO CM VO

t- rM

OJ CM CM CM CM CM CM CM CM 1 CM CM CM . r— r— r—

a. r— ' •“ r—

jd .a

CM CM CM in • • • u. 0 0 0 4~> 0 C +1 +1 +1

CJ 0U rtJ CO r>. If) in CO VO r>. 0 CM cr> CO 0 «vr VO CM

5- 0<u CO CM CM CO CO CO •C" CO «:5- •=r <3- r—

cx. CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM VO JO JO l( CM CO • • • cu 0 0 c •r—

4-»

H +1 +1 ’ H— c

<U CM r— r** vn VO *3" 0 cr» 1^ 0 0 •vT CM CM 0 • ** CJ 0 < c>n CM r— CO CO CM VO VO *53“ VO VO

cu c/) >5r •vr < 'S- a. 0CT\n

CT> c e

"O 'r-CM

«3 lu 2 «5T 0 CM

Q VO 0 0

VO 0 <3- cr> to cn - CO CO CO CO

VI fO f—

(/) f—

«3O 0 «3- CO r— 0 VO CM • • • • • • • • cn CO m CO c CVJ m

r>* CO VO r». CO r— r— r— 1

r— 1—

+-> c

(UsS-301 c:oocon e • r— O

I— CM fO < IX) ><

CJ

cr> «3 +JO>cc

i)

4J • a o

on 2: CM • n

o»uu

«3I coa

39

Standard

deviation

of

the

mean

value

i.e.,

(S//n')

where S

is

the

standard

deviation

ofa

single

measurement.
4. Particulate Physical and Chemical Characterization

4. a. Particle Doppler Shift Spectrometer (PDSS)

Two major areas of study to improve and verify the particle size and

count measurements with the Particle Doppler Shift Spectrometer (PDSS)

have been the extension of the measurement range to submicron particles

and the development of a "diagnostic" parameter measure to detect and

quantitate particle velocity components arising from sources other than

gravitational settling, such as thermal -induced or particle-induced flows

in the measurement cell.

Low Pressure PDSS Measurements : Submicron particle and slip effect studies

We attempted to extend the measurement range of the PDSS to submicron

diameters by evacuating the measurement cell in order to enhance the

sedimentation velocity of smaller particles by the slip effect, a pressuredependent phenomena. We were able to extend the range from 5 ym diameter

down to about 2 ym, but were unable to get any lower due to experimental

difficulties. The limiting problem is the difficulty of generating aerosols

in an evacuated system at 10-15 torr or less. A spray nozzle system was used to generate particles at low pressure. The nozzle does not develop

a spray below about 10 torr. We also attempted to introduce aerosols

generated at high pressures (760 torr) by control -leaking them into the

evacuated measurement cell. Dilution of the sample particle concentration

is so severe however, that the counting statistics become unacceptable.

These experimental difficulties will require a large effort to overcome.

In order to make the slip effect study feasible it would be necessary,

in addition to solving the sample generation-introduction problem, to

a) incorporate a method of rapid, four-place, accurate pressure measure- ment in the torr pressure range and to b) build either a thermally insulated

or thermally controlled measurement cell. Accurate, precise pressure

40
measurement is necessary because pressure and settling velocity are the only independent parameters measureable in the PDSS experiments.

Thermal control of the cell is required because even in the 10-20 torr

pressure region, thermal convections can become the major particle

velocity driving force, destroying spectrum resolution.

Detection and quantitiation of non-gravitational settling particle

velocity components

The accurate particle diameter measurement by the PDSS is described in

the paper "Particle Doppler Shift Spectrometry. Accurate determinations

of 5-15 ym aerosol." by Fletcher, Bright and Chabay in J. Phys. Chem. , 84 : 1607 (1980). The ability to detect and quantitate spurious velocity

components has been described in "Low Reynolds number fluid flow induced

by settling aerosol and detected by Particle Doppler shift spectrometry"

by Fletcher, Bright and Chabay, J. Phys. Chem. , 84: 1611 (1980). A

complete study was made on the settling droplet induced flow effect and

is described in the paper "Droplet Induced Flow Effect" by Bright, Fletcher

and Baum which has been submitted for publication in the J. of Fluid Mech.

These papers are included as the report of these studies.
4.b. Particulates on Glass Fiber Filters: Certification of

$RM*s for Pb, Sulfate, and Nitrate on Filter Media

Final certification of SRM 2673, Sulfate and Nitrate on Filter

Media, and SRM 2674, Lead on Filter Media, has been completed. These

materials are intended for use in the evaluation of apparatus and

methods used in the determination of lead, sulfate, or nitrate in

atmospheric particulates collected on filters.

Certification measurements for the anions were accomplished by ion

chromatography. Lead for SRM 2674 was determined by both voltammetry

and atomic absorption spectrometry (AAS). Statistical analysis of the

data indicated no significant effects of biases in the AAS due to

undissolved solids from the glass filter matrix.

42
81-BCL-b-ENERGY RELATED AIR POLLUTANT ANALYSIS INSTRUMENTATION

1 . Development of an Instrument to Measure Airborne Sulfate Particulate

Matter

Work continued on the characterization and optimization of the pulsed

precipitator/ flame photometric detector (FPD) aerosol sulfate measurement

technique. As indicated in the preceding report, we made an evaluation

of the feasibility of doping the hydrogen gas with SO

2

or ethyl mercaptan

in order to increase the total FPD response into a range where the

instrument is more stable, and to increase the sensitivity of the response.

The sensitivity of the system is a function of the total signal, because

the FPD response (R) is nonlinear with sulfur concentration (s ) ; (i.e.,

where n = 1.8, therefore Sens. = “ n[S]). We have experimentally

verified this prediction; viz., an increase in total sulfur concentration

of a factor of 2.6 is predicted to give an increase in sensitivity of

4.7, in good agreement with an observed increase of 5.1.

An important limitation in the application of the FPD for airborne

sulfate particulate measurement is the slow response time of the burner

to changes in sulfur concentration. The rise time for 90 percent of

full equilibrium response is about 15 seconds, and the fall time is 2.8

seconds. For a precipitator operating frequency of 0.2 Hz we can obtain

only 60 percent of the potentially available response. This is equivalent

to a loss in sensitivity of almost 50 percent. We therefore have looked

for better burner designs. We recently evaluated a burner and detector

system built by Dr. Don Stedman at the University of Michigan and found

that it was much faster (rise time = 1 sec; fall time - 0.2 seconds).

We will obtain this instrument through a collaborative study arrangement,

evaluate the burner for sensitivity, and optimize it for application

with the pulsed precipitator technique. Table 7 shows a comparison of

the percent of full response vs. precipitator frequency for the instrument

we have been using, and for the University of Michigan burner/detector.

43
Table 7

Recovery of Potentially Available Response vs. Precipitation

Frequency

Percent of Full Response

Frequency (hertz) Meloy^ FPD U. of Mich. FPD

.2 60 100

.5 17 85

1.0 5 65

2.0 2 30

4.0 — 10

The development and characterization of the Pulsed Electrostatic

Precipitator-Flame Photometric Detector (PEP-FPD) system for the measure- ment of ambient level aerosol sulfur concentrations has been completed

this year and a final report to EPA is in the review process. The basis

of the technique is the use of the PEP to selectively modulate the

aerosol component of the sample while leaving the gas phase component

unaffected, resulting in a signal from the detector (FPD) which has two

separable components corresponding to the particle and gas phase sulfur

concentrations. Because the FPD response to sulfur concentration is

non-linear (Response where n = 1.5 to 2 depending on various flame

and flow parameters) the sensitivity of the FPD is a function of the

total sulfur concentration in the sample. The following data shows the

sensitivity (dl/dS) and sensitivity relative to sensitivity at 1 ppb for

our FPD:

1

—

1

CO 1

1 o a

or dl/dS (amp/ppb) dl/dS relative to 1 ppb

1 -10

1.42 X 10 (1)

5 4.81 X lO"''’ 3.4

10 8.13 X 10"'° 5.7

50 2.75 X

10"^ 19.4

100 4.65 X

10"^ 32.7

200 7.86 X 10’" 55.4

500 1.57 X

10'® 110.8

1000 2.66 X

10‘® 187.3

®In order to adequately describe materials and experimental

procedures, it is occasionally necessary to identify commercial

products by manufacturer's name or label. In no instance does

such identification imply endorsement by the National Bureau of

Standards nor does it imply that the particular products or equipment is necessarily the best available for that purpose.

44
One consequence of this operational characteristic is that it is possible

to increase the sensitivity of the PEP-FPD system by increasing the total

sulfur concentration in the flame. We have verified this by adding a constant concentration of CH3CH2SH to the hydrogen. A second consequence,

however is a complication of data reduction when one is attempting to

measure more than one sample component because the sensitivities are related to total sulfur concentration, not to sample component concentrations. We have solved this problem by developing a data acquisition/

reduction procedure that enables us to achieve simultaneous measurement of

aerosol and gas phase sulfur concentrations with sensitivities of 0.2

ygm S/m^ and 1 ppb respectively. Initial data comparison from an intercomparison study shows a very high correlation coefficient with data

obtained by a dichotomous sampler-x-ray-fluorescence system.

We have shown the major limitation in response time of the technique

is in the FPD. (The commercially available FPDs have > 60 sec rise

times and 'v 1.5 sec fall times.) We have completed characterization of

a new FPD design which has symmetric rise and fall times of less than one

second. This faster response time means the PEP-FPD system will be

capable of real-time measurements of ambient SO2/SO4 concentrations under

conditions where the concentrations are dynamic, such as in plume traverses.

Additional research will be needed to improve the sensitivity and flow

stability of the fast-flame FPD to its full potential, though it now is

comparable to commercially available FPDs in those respects.
81-BCL-c-ENERGY related pollutants and effects monitoring and associated

METHODS AND TECHNIQUES DEVELOPMENT

1 . Radiocarbon as an Environmental Trace

1 .a. Appi i cations

The use of mini radiocarbon measurements with 5-10 mg (carbon) environmental samples (gases, atmospheric particles, sediment) has continued

with the objective of utilizing the natural ^**C/^^C ratios to distinguish

between biogenic and fossil pollutant sources. Important progress has

been made in our understanding of the source of carbonaceous particles,

especially of those collected in urban areas, through several cooperative

studies with industry* and universities**. A critical element in these

investigations has been the utilization of sample selectivity (chemical

and physical) in combination with the radiocarbon measurements. That

is, because small samples can be used, we have been able to increase the

"information content" of our measurements by examining samples that have

been preselected according to geographical region, known activities,

chemical nature, and stable isotopic composition. A summary of our recent radiocarbon results, together with an indication of these critical

supporting data, is given in Tablie 8. The general conclusions to be

drawn from these studies are (i) urban particles tend to show predominately

fossil carbon (though with a non-negligible biospheric contribution);

and (ii) particles from remote locations contain less organic carbon,

which is primarily biogenic. An extremely important exception occurred

in the Portland Study***, where the combustion of biospheric material

(field, slash, and residential wood burning) led to the first observations

of urban carbonaceous particles containing up to 100 percent biogenic

carbon. These results have caused us to focus on the air pollution

potential of residential wood combustion - a problem which will be a subject of our continuing studies (see Table 9).

* General Motors, Global Geochemistry Corporation.

** Oregon Grad|;(ate Center, Colorado School of Mines, University of

Washington.

*** The Portland Aerosol Characterization Study measurements were carried

out in cooperation with the Oregon Graduate Center and the Oregon

Department of Environmental Quality.

46
l.b. Research Advances

Research activities have been directed toward the analysis of atmospheric

gases, high accuracy natural radiocarbon measurements, chemical -mathematical investigations of the Radiocarbon Dating Calibration Curve, and

extension of the state of the environmental radiocarbon art to microgram

samples using Accelerator Mass Spectrometry. Work with the atmospheric

gases is still in the initial stages; thus far milligram quantities of

atmospheric methane  have been extracted for radiocarbon measurement.

High accuracy radiocarbon measurements are underway in connection with

calibration of the new NBS International Radiocarbon Dating Standard,

and concomitant chemical -statisitical investigations have been performed

in cooperation with the Australian National University on an International

Laboratory Intercalibration exercise involving some 20 laboratories and

three calibration materials (Oxalic Acid, 1850 Tree Rings, Sucrose).

Evaluation of the fluctuations of the Radiocarbon Dating Calibration

Curve is underway in cooperation with the Statitistical Engineering

Division of NBS under the auspices of an international committee

formed for this purpose. Information to be derived includes the assess- ment of accuracy, development of an accepted calibration curve for

accurate dating, and geophysical model information for the assessment of

past climatic variations. Studies initiated in 1979 show outstanding

promise for the analysis of extremely "old" and extremely small samples.

Our exploratory work, which utilized the NBS variable geometry isotope

separator and the University of Rochester Tandem Van de Graaff Accelerator,

demonstrated the feasibility of measuring natural radiocarbon in the 10

ug range. All of the above activities are intended to increase our ability to extract reliable information on anthropogenic and natural

contributions to both environmental pollutants and chemically-induced

climatic perturbations, now and in the past.

** ** The methane study, of interest for climatic reasons and to learn

about man's perturbation of the carbon cycle, is being carried

in cooperation with NOAA (Air Reserves Laboratory).

47
RADIOCARBON

IN

AEROSOLS

AND

SEDIMENT

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49
1 .c. Statistical Evaluations of the International Radiocarbon Cross

Calibration Exercise » and of the Natural Radiocarbon Fluctuations

High accuracy natural radiocarbon measurements are of critical importance

in a number of fields, ranging from archeology to climatology to environmental science. In addition to our current activities related to the

calibration of the new International Standard for Radiocarbon Dating

(replacement for SRM 4990B), we have contributed to the numerical evaluation

of interlaboratory data representing a) high precision measurements of

homogeneous primary and secondary natural radiocarbon standards, and b)

the "calibration" relationship between radiocarbon concentrations and

calendar age as deduced from dendrochronology (tree ring measurements).

The first activity is important for assessing the relative activity of

the three "standards" and for identifying error sources and limits

(random and systematic) among the best laboratories internationally.

Deliberations on the second topic culminated in the organization of the

International Comnittee for the Calibration of the Radiocarbon Time

Scale, to which NBS scientist, Lloyd A. Currie, is an advisor. The fine

structure of the radiocarbon dating calibration curve — i.e., long-term

trends and short-term fluctuations about the simple exponential decay

model — is important for two major reasons: a) fine structure must be

adequately evaluated/fitted to achieve accurate dating, b) modeling of

the fine structure provides a means for us to learn more about the

history of the earth (climate, environmental changes, ocean circulation,

solar activity, etc.).

i. Exploratory Analysis of the International Radiocarbon

Cross-Calibration Data: Consensus Values and Interlaboratory Error

Data from the international cross -cal ibrati on exercise have provided an important opportunity to assess the state-of-the-art of high-precision

natural radiocarbon measurement and to derive consensus values for two

relatively pure and homogeneous materials relative to the international

radiocarbon dating standard (NBS Oxalic Acid, SRM-4990B). Performance

was good: some fifteen laboratories returned results for the two indepen50
dent ratios -- Australian National University Sucrose/Modern Standard

(S/M) and 1850 Wood/Modern Standard (W/M) — with a typical imprecision

(standard deviation) of about five percent per mil; and the distribution

of results was relatively narrow. The primary limitations encountered

were incomplete laboratory data and variable reporting practices.

Analysis of the data led to the following observations:

• Imprecisions (standard deviations) reported varied from about two

percent per mil to eight percent per mil, with one laboratory

reporting 28 percent per mil. Most, but not all, imprecisions

represented counting statistics only.

• Apparent blunders (large deviations from consensus values) occurred

in a few cases, especially for estimates of the ratio S/M.

• "Laboratory error," a — i.e., a non-Poisson error component --

A was estimated from the data distributions for both sample ratios.

Results were similar: for S/M, a = 3.5 percent per mil; for

A

W/M, a = 1.8 percent per mil. These error estimates, though

A

rather uncertain because of the limited number of degrees of

freedom, are consistent with earlier estimates, and the may

reflect the accuracy limit for current counting techniques.

• Consensus ratios, following the use of exploratory techniques to

identify blunders, and taking into account "laboratory error" and

varying Poisson imprecision, were A^‘*C - 508.1 ± 2.0 percent per

mil (1850 Wood, age-corrected for decay to 1950). (Uncertainties

represent one standard error, and both S and W are normalized to

= -25 percent per mil).

Further results of the evaluation include distributions and the

search for measurement method-, sample nature-, and isotope fractionationrelated effects. (See Figure 8 for histograms of the intercomparison

results).

ii. Calibration of the Radiocarbon Time Scale

Evaluation of the structure of the radiocarbon calibration curve is

critically important both for accurate dating (as shown in Figure 9)

51
CROSS-CALIBRATION HISTOGRAMS

(corrected deviations, in ^loo)

S/M

530 WifM SIW

525

520 10 s 525

‘’I 515 s 5 q 520 G

0

k m

510 A G k 0 d j L 515

505 E F^L 0 -5 A B E G h 510 A E F

500 B d m R -10 F k 0 505 B

495 h j -15 m P 500 d h L

490 495 c j P s

485 I

480 P

S, M, W = Sucrose, Modern Standard, Wood

Cj = 2 °/oo ~ 40/00 (Cap.); 5 0/00 - 8 0/00 (Lower Case)

Figure 8 Histogram of the radiocarbon ratios for AND sucrose (S), 1S50

wood (W) and the modern standard (M; 0.95 x NBS oxalic acid).

Numerical scales are expressed as deviations (in parts -perthousand) from unity from each of the three ratios; and

laboratories are coded alphabetically.

I

52
CONVENTIONAL

RADIOCARBON

DATES

IN

RADIOCARBON

YEARS

BEFORE

PRESENT

cr> c

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53
RADIOCARBON

AND

SOLAR

ACTIVITY

.1 § s ,

LUs—<o

54

Figure

10

Correlation

of

radiocarbon

fluctuations

with

solar

activity

(sunspots)

and

climate

(*®0

in

ice

cores).

The

upper

figure

is

taken

from:

Eddy. 0.

A.,

The

Maunder

Minimum,

Science

192.

1189

(1976).

The

lower

figure

is

taken

from

figure

on

p.

615:

Mathews,

S.

W.,

What's

Happening

to

Our

Climate.

National

Geographic

150,

576

(Nov.

1976).
and for geophysics and climatology (Figure 10). At the present time,

because of the remarkable precision of natural radiocarbon measurements

and the unique time (8000 year) record provided by dendrochronology,

radiocarbon is the only radionuclide capable of giving us direct information on past fluctuations in solar activity. When combined with geophysical

modeling and ice core measurements of the ancient atmosphere (CO

2

)* the

variations will yield further insight into the history of the carbon

cycle and prognosis for "the CO

2 problem."

Objectives of the International Committee are to assemble high quality

data and to utilize geophysical and statist! cal -mathematical approaches

to "fitting" the data. More specifically, the Committee seeks to

identify means for combining all (reliable) ^'*C measurements of treering dated wood specimens into a single radiocarbon scale calibration

scheme, preserving as much of the high frequency components as seem

warranted by the data. During the past year cooperative efforts by

L. A. Currie (Center for Analytical Chemistry), C. Spiegelman (Center

for Applied Mathematics), and J. C. Lerman (Univ. of Arizona) have

produced important insights into measurement and i nterl aborato ry errors

(see also part 1, above), assumed functional models, and best estimates

for the calibration curve and its uncertainty band.

l.d. AdvanrP<; in Small Sample Radiocarbon ^asurement Techniques : Application to the Assay of Individual Atmospheric Chemical Species

During the past year the NBS program to utilize natural radiocarbon as

a tracer for sources of carbonaceous pollutants has been directed

toward a) fundamental advances in measurement and data evaluation techniques

and b) critical studies of urban air pollution episodes (such as the

Denver "brown cloud") and basic investigations of sources of atmospheric

gases and particles. The importance of these investigations rests upon

the impact of both natural and man-made carbonaceous contaminants on health, stratospheric ozone, and climate. The success of this program,

the only such program extant, is due to the ability of NBS to perform

55
reliable radiocarbon measurements on ambient samples containing microgram to milligram quantities of carbon.

Measurement advances are continuing through the development of miniature

gas proportional counter and nuclear accelerator ("atom-counting")

techniques which provide sensitivity gains of 10^ to 10^ compared to

conventional radiocarbon dating techniques. Important meetings treating

these topics (among others), organized by individuals in the group,

included an ACS Symposium ("Nuclear and Chemical Dating Techniques",

March 1980) and a meeting at NBS (August 1980) on sample preparation for

accelerator measurements. Our work with the accelerator, which last

year demonstrated the capability of precise measurement using less than

40 yg (carbon) of the new international radiocarbon dating standard, is

continuing with studies in alternative source preparation methods,

isotopic enrichment, and baseline tests with the first "dedicated"

tandem accelerator constructed exclusively for atom-counting measurements.

This particular machine is considered a National Science Foundation

Regional Facility, and it will be located at the University of Arizona.

The accelerator approach will make possible the radiocarbon assay of

yg quantities of individual hydrocarbons and halocarbons, and individual

chemical and size fractions of non-urban atmospheric particulates.

Applications to urban pollution and source studies of carbonaceous

particles have centered on vegetative burning in the Portland, Oregon

region, vegetative v£. oil shale aerosol contributions in a remote Utah

location, urban pollution in Los Angeles and Denver, and an international

effort (joint US - USSR AFAEX-79 project) to investigate "processes and

mechanisms of formation and transformation of natural aerosol" in a remote forested region in the Soviet Union. In all of these studies,

which were broadly interdisciplinary in nature, our group provided the

only isotopic data; and the natural radiocarbon results yielded the only

unique measure of the biogenic (non-fossil) contribution. This was especially important in the Denver and Portland studies where as a

56
result of our measurements it was concluded that residential wood burning

constituted one of most significant sources of inhalable (< 2.5 ym) and

visibility-reducing particles. In Denver for example, it was concluded

that 18 percent of the visibility reduction of the winter time atmosphere

arose from wood burning. Furthermore, 39 percent of the most effective

visibi ty-reducing species -- elemental ("graphitic") carbon — has been

ascribed to wood burning.

It should be noted that the foregoing regional studies have included

considerable data on chemical and physical characteristics of the ambient

particles, together with supporting emission inventory and meteorological

data. Although radiocarbon techniques provided the only direct measure

of contemporary carbon, the other (indirect) indicators supported the

conclusions from radiocarbon measurements in every case. A major challenge exists in selecting and evaluating the entire multidimensional data

patterns from such experiments; this need formed the basis for the first

Receptor Modeling Workshop (March 1980 in Durham) and the resulting

conmiittee on chemical mass balance and multivariate analysis methods of

source reconciliation. Our program at NBS has been expanded to include

such modeling efforts, in cooperation with NBS Center for Applied Mathematics. The combined use of isotopic data (^^C and ^**0) with particle

size and chemical data (pyrolysis mass spectrometry, inorganic composition

and elemental V£. organic carbon) has, in fact, been an intrinsic part of

the above urban and remote particulate studies.

A summary of our recent radiocarbon measurements, which now include

atmospheric gases as well as particles, is given in Table 10. Future

work will be directed toward further sampling of selected gases (hydrocarbons, carbon monoxide), sources of urban run-off and sediment studies,

high-altitude sampling, investigations of arctic haze and climatological

consequences, and paleoatmospheric (isotopic) composition via ice core

samples.

57
Recent

Rad1oc»‘:ruon

Resul eo

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58

Residential

wood

combustion
81-BCM-a-ENERGY RELATED POLLUTANTS AND EFFECTS MONITORING AND ASSOCIATED

METHODS AND TECHNIQUES DEVELOPMENT

1 . Energy Related Water Pollutant Standard Reference Materials

1 .a. Aqueous Polynuclear Aromatic Hydrocarbons in Water (SRM 1644)

Generator columns for the production of saturated aqueous solutions of

anthracene, benz(a)anthracene, and benzo(a)pyrene constitute SRM 1644. The

columns were prepared commercially and have been certified by two independent

analytical techniques.

The first technique involves quantitative extraction of the PAH from the

aqueous stream by an "extractor column" packed with Cis bonded phase, use of

an acetonitrile-water eluent to transfer components from the extractor column

to an analytical Cis column for separation of the analyte from non-analyte

components, and detection of the analyte by absorbance at 254 nm.

The second technique uses a "standard addition" technique for "on stream"

analysis. The effluent from the generator column is mixed with PAH standards

dissolved in acetonitrile, and the resultant PAH in the mixed solvent determined by fluorescence.

Preliminary data from the certification are given in Table 11. The filial

certified values will result from a compilation of the data obtained from both

methods. Such a compilation has been completed for benzo(a)pyrene, where:

In (cone.) = 20.35 - 5924 (^)

where cone, is in units of pg/kg.

or

In (cone.) = 1.00 - 5924 (—

)

K

where cone, is in moles/liter.

59
Table 11

Preliminary Results of Analysis Using Two Techniques

for Generator Column Aqueous Effluents

Temperature

Anthracene

Concentration (yg/kg)

m Technique 1 Technique 2

30 58.8 59.6

25 42.8 42.9

20 31.1 30.9

15 22.6 22.2

Benz(a)anthracene

Temperature Concentration (yq/kg)

(°C) Technique 1 Technique 2

30 12.3 13.0

25 8.86 9.32

20 6.37 6.67

15 4.58 4.78

Benzo( a) pyrene

Temperature Concentration (yg/kg)

CO Technique 1 Technique 2

30 2.28 2.26

25 1.62 1.60

20 1.14 1.14

15 0.80 0.81

10 0.57 0.58

60
Table 12a

Fitted Concentrations Utilizing the Equation for Benzo (a) pyrene Data

(in yg/kg)

Temp., C Concentration Lower Limit Upper Limit

10.0 .5616 .5382 .5859

11.0 .6045 .5811 .6288

12.0 .6503 .6270 .6745

13.0 .6993 .6761 .7233

14.0 .7516 .7287 .7753

15.0 .8074 .7848 .8307

16.0 .8669 .8447 .8897

17.0 > .9303 .9085 .9527

18.0 .9979 .9764 1.01 99

19.0 1.0699 1.0486 1.0916

20.0 1.1465 1.1252 1.1683

21.0 1.2281 1.2062 1.2503

22.0 1.3148 1.2918 1.3382

23.0 1.4070 1.3821 1.4323

24.0 1.5050 1 .4774 1 .5331

25.0 1.6091 1.5777 1.6410

26.0 1.7196 1.6836 1.7563

27.0 1.8369 1.7952 1.8795

28.0 1.9613 1.9130 2.01 08

29.0 2.0932 2.0373 2.1507

30.0 2.2331 2.1685 2.2996

61
Table 12b

Fitted Concentrations Utilizing the Equation for

Benzo(a)pyrene Data in S.I. Units (mol/L)

Temp. , C Concentration Lower Limit Upper Limit

10.0 2.2261 2.1336 2.3226

11.0 2.3962 2.3035 2.4926

12.0 2.5780 2.4854 2.6739

13.0 2.7721 2.6802 2.8672

14.0 2.9794 2.8884 3.0732

15.0 3.2005 3.1109 3.2927

16.0 3.4364 3.3482 3.5268

17.0 3.6878 3.6013 3.7764

18.0 3.9557 3.8706 4.0427

19.0 4.2411 4.1568 4.3271

20.0 4.5448 4.4602 4.6310

21.0 4.8680 4.7815 4.9562

22.0 5.2118 5.1208 5.3045

23.0 5.5773 5.4788 5.6776

24.0 5.9657 5.8563 6.0773

25.0 6.3783 6.2541 6.5050

26.0 6.8164 6.6737 6.9621

27.0 7.2813 7.1162 7.4502

28.0 7.7745 7.5832 7.9708

29.0 8.2976 8.0759 8.5253

30.0 8.8520 8.5960 9.1156

*N0TE: Concentrations are reported in units of 10"®.

62
K is degrees Kelvin in both equations.

The maximum uncertainty for either of the equations between 10 °C and

30 °C (273.15 and 303.15 K) is + 0.042. Tables 12a andl 2b express the

concentrations at one degree intervals between 10 °C and 30 °C.

1 .b. First Natural Matrix Trace Organic SRM Issued for Shale Oil

The Center for Analytical Chemistry has in the past conducted

several collaborative studies aimed at assessing the accuracy of data

obtained from trace organic analytical methodologies. The results of a recent study involving the determination of specified phenols, polynuclear aromatic hydrocarbons, and N-heterocyclics in a shale oil sample

by several laboratories revealed large systematic biases among laboratories. One method for enhancing the accuracy of analytical mea- surements is the use of suitable quality assurance standards or Standard

Reference Materials (SRM's). However, until now, SRM's for environmental

trace organic analyses were nonexistent due to the lack of analytical

methodologies necessary for certification.

Over the past few years, analytical methodologies have been developed and used to certify the first natural matrix SRM for trace-level

organic constituents. Organics in Shale Oil, SRM 1580. The quantitation

of individual compounds in the complex shale oil matrix necessitated the use of multi -dimensional chromatographic procedures, i.e., gas or liquid

chromatography on two columns of different selectivity and/or extremely

selective detection methods.

Three different methods of sample preparation were used prior to

analysis: simple dilution of the shale oil with methylene chloride (or

other suitable solvent); aci d/base extraction to isolate acidic, basic,

and neutral components; and a high-performance liquid chromatographic

63
fractionation. Two of the following techniques were employed to determine the certified values for the organic compounds in shale oil:

capillary gas chromatography (GC), gas chromatography/mass spectrometry

(GC/MS) with single ion (monitoring) for selective detection, and high - performance liquid chromatography (HPLC) with selective fluorescence

detection. All GC/MS analyses used the standard addition method for

quantitation. The GC and HPLC analyses employed either internal standard, external standard, or standard addition methods. The excellent

comparability of the values determined by these different analytical

methods is illustrated in Table 13. Table 14 lists values for other

compounds determined by only one technique. These values will appear on the SRM certificate for information only. The methods developed for the

certification of this SRM are applicable to the determination of similar

compounds in other complex natural matrices. Standard Reference Material

1580, Organics in Shale Oil, is intended primarily for evaulating the

reliability of analytical methods used for the determination of trace

level polynuclear aromatic hydrocarbons, phenols, and nitrogen heterocyclic compounds in shale oil, coal -derived liquids, or petroleum products.

In addition, this SRM may be used as a surrogate standard for any com- plex environmental extract containing classes of compounds for which the

SRM is certified.

64
Table

13-

Summary

of

Results

for

Or*\janic

Compounds

in

Shale

Oil

Determined

by

Tv;o

Inde|)cndent

Techniques . o ^ .-r—

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a CO

a o s S 1 S 1 S 1 -J

fa •f- a. •f— c. Cl* (n Q 33 Q = 33 33 (33

(U

C 3 3

d> 0) O)

a 3 c. 3 3 >% g; 3 O. 3. JZ O —> a

3. la < O f c zz

fO fj 5 o o c. f—

COMM o >> 3 3 3 f GJ GJ r— w

03 -Q 4> CL 3 3 3 c O O C o

•f— •r- “r— +J 4-* 4-> 4J 3 u O CO O O <a r3 <a <a

•r— c. &. c. s. •P p 4-> 4-> 4-> O X X X X

0> LU LlI UJ IJLI 'O3 a <U a <y »—«

•y> (/) CO CO fO fa <a a

4-> CO CO C3 ca Oa CO CO -O CO -3 o -a -O CO S 1 —J *r— _J •- —1 *1— •r» —1

•r- O. QU o.

u £X CJ

O QQ 33 33 < 33 < o: < < 33

ZJN»c

ula

r—

O o 3 o c —

0) f— E C •*G 3. 3

r— •r—3

o: cr

4-> o

r—

a

M o o 3

OJ r— y>a Cl 3 O (U a JO 3 0 3 s- 1 1 cr CJ u CO CO

>., or 1 •f' C3. (3l o CC4 3J n

65
Table 14. Summary of Results for Organic Compounds in Shale Oil

Determined by One Technique.

Compound

Sample Preparation

Technique

Analytical

Technique

Concentration

(yg/g)

benzo(k)fluoranthene HPLC HPLC 13

phenanthridine HPLC HPLC 45

m-cresol Acid/Base Extraction GC 330

p-cresol Acid/Base Extraction GC 270

2, 4-di methyl phenol Acid/Base Extraction GC 380

2, 5-dimethyl phenol Acid/Base Extraction GC 320

2 ,5 ,6-tri methyl phenol HPLC GC/MS 360

2 ,4 ,6-tri methyl phenol HPLC GC/MS 120

a. Shale Oil Round Robin :

Many laboratories are currently involved in the quantitative

analysis of individual toxic organic compounds in alternate fuels and

energy effluents. For many of these environmental analyses there is

little knowledge of the comparabi li ty of data from different laboratories, and in most cases probably little knowledge of intra laboratory

precision. To gain insight on this matter aliquots of the shale oil

sample were sent to six laboratories currently involved in characterizing alternate fuels. The labs were requested to determine the con- centrations of selected compounds in the shale oil. The results of

this limited inter laboratory exercise are presented in Table 15 . The

scatter of the results indicates the variability of state-of-the-art

quantitative analyses for individual compounds in a complex matrix. It

also stresses the need for an SRM such as the shale oil which laboratories can use to guage the accuracy of their analytical methods.

Table 15. Interlaboratory comparison

(ppm).

of results of shale oil analyses

Compound NBS^ 2 3 4 5 6 7

pyrene 107 155 360 150 168 212 141

fluoranthene 61 102 220 80 108 104 112

phenol 395 392 180 - - - 399

£-cresol 338 350 150 - - - 381

2 ,4 ,6-tri methyl pyri di ne 1060 468 460 - 950 - 1092

^Results reported by NBS represent the mean of values obtained by GC,

GC/MS, and HPLC.

66
1 .c. Work Plan and Evaluation/Feasibility Study of Drilling Fluid

Reference Standards for Chemical Analysis

Background

Man's activities in off-shore drilling (as well as on-shore drilling)

must proceed in order to locate new sources of oil and gas to satisfy

the increasing demands for energy resources. If we are to preserve our

renewable resources as we extract oil and gas from the continental

shelf, research, development, and monitoring are needed to provide a better foundation for rational decisions on minimizing risks and protecting other resources.

Drilling fluids are now recognized as one of the major factors

involved in the success or failure of drilling operations. The com- position of a drilling fluid depends upon the formation to be drilled.

Drilling fluids normally consist of colloidal suspensions of clay and

minerals in water with chemical additives, and are used in production

operations to support the borehole, to remove cuttings, and to cool the

drill bits. In order to control the physical and chemical properties of

drilling fluids, several types of inorganic and organic chemicals are used in conjunction with the clays, minerals, thinning and dispersing

agents, etc. Since disposal of the drilling fluids is into water or onto adjacent land, it is essential to characterize these fluids for

their chemical constituents in order to evaluate and assess the fate of

the chemical constituents (many of them toxic) on the aquatic and

terrestrial environment.

Scope

NBS will develop and provide EPA/Gulf Breeze with drilling fluid

reference standards for use in characterization efforts and in a quality

assurance program to improve and maintain reliability of measurements

made on discharges from drilling and production operations.

Milestones :

(1) Obtain candidate reference material (s) from EPA/Gulf Breeze

and assess the feasibility for preparing a dry mixture of

four major drilling fluid components

67
(2) If milestone (1) proves feasible, prepare a batch (i.e.,

grind, blend, sieve) of material and establish homogeneity

(3) Characterize the drilling fluid mixture for several trace

elements to be determined by NBS and EPA/Gulf Breeze

(4) Package, label, and provide EPA/Gulf Breeze with drilling

fluid reference standard for specified trace elements

(5) Initiate studies on a drilling fluid material chosen in

concert with EPA/Gulf Breeze for future (FY81) issuance as

a more complex or more characterized standard

Progress

EPA/Gulf Breeze provided NBS with three test "fluids" for feasibility and assessment studies. As a result of these studies, EPA/Gulf

Breeze and NBS have agreed that the reference drilling fluid sample

should consist of a dry mix of the components found in drilling mud.

NBS has ordered and received the five major components of drilling mud - barite, bentonite, chrome lignosulfonate, lignin, and caustic soda.

The first three components have been blended in a dual V blender.

Samples of this blend will be analyzed to confirm or deny the apparent

homogeneity of the sample. Conceivably, some re-segregation of the

sample may occur on storage due to the large difference in component

densities. Therefore, some effort will be made to determine the degree

to which this may happen. Packaging in small units and requiring use of

the entire sample in an experiment would be another way around this

problem.

If lignin is added in the solid state with caustic soda, two problems

arise. First, the oil companies believe that the total mixture of dry

components will not mix with water to yield the normal mud. Secondly,

caustic soda is hygroscopic and in a flake form (all other components

are powders, 200-400 mesh). It would have to be ground (difficult to

do) in order to blend well with the other components. At this point, it

would be appropriate to solicit reaction to a three component dry mix

because of the problems associated with a 5 component mix.

68
1 .d. Laser Analysis of Pollutants in Cryogenic Matrices

Scientists in the NBS Center for Thermodynamics and Molecular Science

(CTMS) have designed and completed the first stage of testing of a molecule specific measurement technique for the analysis of complex

environmental samples for evaluation or compliance with EPA standards.

In the past several years it have been recognized that realistic legislation "impacting environmental quality must be targeted at a small

number of potentially harmful chemicals, rather than gross regulation

of, for instance, total organic carbon. Of the existing techniques, the

computer controlled gas chromatograph-mass spectrometer system is the

most powerful in terms of sensitivity and specificity. A high degree of

sensitivity is required since many of these regulated chemicals have

toxic or carcinogenic effects at levels in the ppt level; specificity is

required since in many cases the toxicity of a given chemical species

may vary as much as several orders of magnitude between isomers. This

is particularly true for the dioxins.

The laser technique offers a quantiative sensitivity comparable to

that obtained by state-of-the-art 6C-MS systems, a much higher degree of

selectivity, and should, when fully implemented, be suitable for certification of environmental SRM's and performance of referee-type mea- surements. This technique involves laser Raman scattering from molecules

isolated in a cryogenic matrix. Raman spectroscopy provides a valuable

fingerprint of the vibrational modes of the molecules present allowing

for identification based on comparison to a library file of known spectra.

Since the molecules are physically trapped in an inert matrix, there is no interference in the Raman spectrum of the first species due to the

presence of a second or other species, the signals from a complex mixture such as expected from real environmental samples is simply the sum

of the individual components.

To date, NBS scientists have successfully demonstrated the potential sensitivity and selectivity of this sytem in the analysis of lab69
oratory samples of complex mixtures of volatile organic species at the

sub nanogram level (corresponding to recapture of environmental samples

at the ppt level). In these studies isomeric species were readily

resolved with a 0.3 cm'^ resolution (isomeric peaks often show Raman

shifts of 10 -50 cm’M- The group recently acquired an LSI-11 controlled

optical multichannel analyzer (OMA) and commercial gas chromatograph and

have refabricated the sampling system to provide for higher sensitivity

and sample through-put and to allow analysis of real world samples.

The status of this work is now at the point that within 6 months

our operative system should be ready for the acquisition, separation and

analysis of environmental samples. Considerable help was received from

colleagues at Argonne National Laboratory. The initial tests of this

system will include analysis of laboratory and real world samples of the

tetrachlorodibenzo-dioxin isomers which cannot currently be distinguished

by any existing technique at any concentration.

70
81-BCM-b-ENERGY RELATED POLLUTANTS AND EFFECTS MONITORING AND ASSOCIATED

METHODS AND TECHNIQUES DEVELOPMENT

1 . Development of Organic SRM's for the Calibration of Energy- Related

Water Pollutant Measurement Methods

1 .a. Analysis of Phenolic and Polynuclear Aromatic Hydrocarbon Species

in Alternate Fuels and Effluents

Several coal gasification, oil shale refinery, and oil refinery aqueous

effluents have been analyzed for selected phenolic and polynuclear aromatic

hydrocarbon (PAH) species. A simple one-step organic extraction has been

developed to isolate the phenolic and PAH compounds prior to quantitative

analysis by selected ion monitoring (SIM) GC/MS. Individual compound con- centrations were determined by an internal standard method (where suitable

internal standards were available) or by comparison with a series of external

standards

.

Samples

The aqueous effluents were obtained from the Gulf South Research Institute,

New Orleans, Louisiana. They were stored in amber glass bottles at 4 °C until

analyzed. Prior to analysis, each sample was equilibrated at room temperature,

homogenized by mixing vigorously for 1 minute, and filtered through Whatman #41

paper to remove any suspended particulate matter and/or insoluble oil. One

hundred (100) mL of each sample was analyzed as described below:

Polynuclear Aromatic Hydrocarbons : The effluent (100 mL) was spiked with an appropriate amount of pyrene-dio internal standard (IS). The sample was filtered and extracted with 100 mL CH 2 CI 2 . The organic extract was dried by

filtering through a cone of anhydrous Na2S0it. The sample volume was reduced

to MOO pL under a stream of dry N2 for GC/MS analysis. All samples were

analyzed in duplicate, and a sample blank consisting of 100 mL deionized H 2 O was also analyzed. 1 to 2 yL of the concentrated extract was chromatographed

on a 30 m SE-30 fused silica wall -coated open tubular (WCOT) column, which was

li
interfaced directly to the ion source of a quadrupole mass spectrometer. The mass spectrometer was operated in the selected ion monitoring mode. The

molecular ions for the analytes (fluoranthene m/z 202, pyrene m/z 202, benzo(a)

pyrene [B(a)P] m/z 252, benzo(e)pyrene [B(e)P] m/z 252, perylene m/z 252) and

the pyrene-dio internal standard (m/z 212) were monitored with a mass spectrometer dwell time of 100 ms (see Figure 11).

Relative response factors for the analytes relative to the pyrene-dio

internal standard were determined from a gravimetrical ly prepared solution of

the pure compounds. Individual compound concentrations were determined from

the analyte and internal standard peak areas and the experimental ly determined

relative response factors. The results of these determinations are shown in

Table 16. PAH concentrations were al so determined in a separate series of

experiments using an external standard method. No precision data is reported

for these values as only one determination of each compound was made. In most

cases, however, the agreement between the internal standard and the external

standard determinations is very good.

Phenols : The following phenols were determined in the aqueous effluents:

phenol, o-cresol , m-cresol , p-cresol , 2,4- + 2, 5-dimethyl phenol , and 2,6-

dimethyl phenol . One hundred (100) mL of the effluent was spiked with an appropriate amount of 2-chlorophenol as an internal standard. The pH of the

sample was adjusted to M with HaSOit and the sample extracted with 50 ml

CH 2 CI 2 . The sample volume was reduced to 100-200 yL under a stream of dry Na,

and 1-2 yL aliquots analyzed by 6C/MS. Chromatographic separations were

carried out on a 20 m Pluronics PL-64 WCOT column which gives excellent

resolution of all the phenols except the 2,4- and 2, 5-dimethyl phenols which

are unresolved (the values determined represent a sum of the concentrations of

the two isomers). The molecular ions for the analytes and the internal

standard were monitored in real time with a 100 ms dwell time in order to

insure at least 20 data points across the chromatographic peak (see Figure 12).

Relative response factors for the analytes relative to the 2-chlorophenol

internal standard were determined from a gravimetrical ly prepared solution of

72
6C/MS SIM Analysis of PAH in Coal Gasification Effluent

73
Figure 12

6C/MS SIM Analysis of Phenols in Coal Gasification Effluent

74
Table 16

Polynuclear Aromatic Hydrocarbons in Energy Effluents

(PPb)

Sampl e Analyte Concentration

External Standard

Coal gasification effluent fl uoranthene 11.6 + 0.2 7.5

CG-04

pyrene 11.0 + 0.1 7.6

benzo(e)pyrene 0.92 + 0.02 0.7

benzo( a) pyrene 1.6 + 0.3 1.5

perylene 0.5 + 0.1 0.5

Coal gasification effluent fl uoranthene 303 + 2.8 296

CG-06

pyrene 281 i 12 244

benzo(e)pyrene 30 + 0.7 37

benzo(a) pyrene 58 + 1.4 57

peryl ene 18 + 0 86*

*non-analyte interference co-eluting with perylene.

75
Phenols

in

Enerqy

Effluents o

to KO o O o o o Q 0) C\J to r” z 1—

z:

t- o1 o.

CM

VV 0

to

01 VO cr> o Ci o Q o i. CM z z z o1E

CO

VV

Q.

a. oto CT> CM o o o o o <u fmm O r— r— f— r-^ uo1o

00 CM

V

VV

V

V

•> •p

>1

'C o

•r“ •P

»0C

•r“E Pc a cy» O o o o o S-. OJ 1 CM CM 00 r— r— r— r— r— (1) 3

to CM 4-> r“ V V V V V 0) 4- -P CM o 4- C

<u a) CM •P 3 C C t—

4- 0 (U 4- O •1-3 4- r- 4-> r— 0) 0> O to 4-

CO

C

O 4- >>

<d 0)T- <U t- TD x>

O CO

O CM o o o O

O s- JZ 4- tU s- l- xz CO CO to r~ r~ r— r“ f“ 0> O.T- tu C to to o O 1^ > r— to r— T- •o o

j:

VVV

V

V «o >0 <0 to 4- £= c

Cu jc cn xz tu to to "O c •P to i- •p +J <u m d) r— to to P E to r— r— o p •r— O ’t— *r— f— r— a c •o U O O to to p

<u c C <L) to III III III III s- S- x> * <u 0) (U

tt •It c. Op

pp

—

^—^ Q. 2: CO to oi c X o

to to to to to to to to 0) o o o o •c— CL) CZ 0) —

UJ LU Ui 1—

*—

1—

•—

&-

r-“ •V ^ V ^ > ^ ^ ' ' ' ^ II II II Q. to • • E •£> CM CM f— CO to <u to to to o (O o o O CM CM CM 3 <u »—

UJ z to 1 1 1 1 1 1 1 1 r— •p -it * -It CO C3 CJ3 to to az oi: oc to o •It •It (_) t_> t_) o o o o o > z •l:

76
the pure compounds. Individual analyte concentrations were determined from

the analyte and internal standard peak areas and the experimentally determined

relative response factors. The results of these determinations are shown in

Table ]7. Concentrations in the coal gasification effluent C6-06 and the oil

shale effluent OS-42 could not be determined by the internal standard method

because of a co-eluting interference at the retention time of the 2-chlorophenol internal standard (the co-eluting compound(s) produced a significant

ion current at m/z 128, the Cl -35 molecular ion of the internal standard).

Determinations for these samples were based on a series of external standards.

1 .b. Combined LC/MS Technique for Direct Quantitative Analysis of

Individual Organic Compounds in Complex Mixtures

An interface for a conventional liquid chromatograph and a conventional mass spectrometer has been constructed which operates on the principle of pre-concentrating a liquid stream and then admitting

part of it to the ionization region of the mass spectrometer. The

selectivity of the mass spectrometer and the reproducible behavior of

the entire system allow the direct quantitation of substances in complex

mi xtures

.

The pre-concentration is accomplished by allowing the effluent from

the liquid chromatograph to flow down a heater wire. The evaporation

of solvent has yielded up to a 20-fold enrichment of analyte, and it is

believed that 100-fold enrichment is feasible.

The flow into the mass spectrometer is controlled by a small

needle valve built into the tip of the inlet tube. The valve is formed

by a 0.05 mm teflon film at the tip of the tube pierced by a pointed 0.1 mm wire which passes throught the bore of the tube. Flow rate into the mass spectrometer can be controlled in the range of 0-20 yL/minute.

Since all of the pressure drop occurs at the high vacuum end of the

tube, boiling within the tube with consequent unstable flow is avoided.

77
The stability of the system is such that quantitation can be done

with external as well as internal standards. Figure 1 (pg. 11) shows

typical chromatograms from the determination of phenol in a shale oil

matrix using external standards. The level found was 400 ± 40 ppm, a value in good agreement with, and with precision comparable to, two

other methods requiring lengthy sample pretreatment. The direct shale

oil determination by LC/MS required about 15 minutes per run.

1 .c. Development of Phenol in Water SRM

To date, a comparison of the stability of some selected phenols in

distilled water and in industrial wastewater using high-performance

liquid chromatography (HPLC) has been made. A standard solution of some of the phenols on the Priority Pollutant List were used to spike both the

distilled water (Table 18) and industrial wastewater (Table 19).

Since a detectable amount of phenol was initially found in the industrial

wastewater, no additional phenol was added. The spiked solutions were

stored in both ani)er and clear ampoules. This was done to observe any

possible degradation of the sample due to light. Also, to observe the

correlation between the loss of phenolic compounds and microbiological

activity which possibly effects chemical stability in wastewater, a preservative technique used by Carter et al.^ (pH 3.7 data), was employed

for one set of the wastewater samples.

There is no clear explanation for the behavior of the phenolic compounds

in the preserved industrial wastewater. Our results indicate that the solutions

have been stable at neutral pH (see Table 19).

To determine the stability of some phenols in water during a more longterm study, a four-year-old phenol in distilled water solution was analyzed.

The results are shown in Table 20.

^From the draft of "Preservation of Phenolic Compounds in Wastewater" by

Mark Carter and Madeline Huston, Central Regional Laboratory, Environmental

Protection Agency.

78
In the future, a similar study using two less concentrated (<10 ppm)

solutions of some phenols in distilled water and in industrial wastewater without sample preservation will be carried out.

79
Phenols

In

Distilled

Water

Stability

Study

g.

CLco

00

1. 4^C

Cfu

c:oo o r—

o o O r— o csi 41 4J 41 41 41 41

IT) in CO VO

>» in CO <r 00 ro in

to • • • • • o fO CM CO

Csl CO CM r" CO r—

to CO so CM Lf> CM • • • • • • o o o O o CM 41 41 41 41 41 41 CM 00 00 a>

>> CO r-* ir> CO cr» o lO • • • • • • o m CM

CM CO CM CO « VO CVJ in CM

in • • • • CO C) o o o O o r— 41 41 41 41 41 41

CTi CM VO >> CM CM 00 VO CO o rtJ • • • • • • Q VO CM

CM CO CM CO

fmm 00

<o • • • • • «a- r*“ fmm. o o 00 41 41 41 41 41 CO O in cr» >, o> cr» o in CO

ta • • • • • Q CO in CO CO VO CM CO CM r— CO

in VO CM CO 0 • • • CO r" r“ o o CM r~

in 41 41 41 41 41 +1 CO CM CM O 00

CO r>- in VO o to • • • • • • o CO in CO

CM CO r— rTM CO

CO VO in

•0 • • • • 00 fM r~» o o CM in 41 41 41 41 41 as CO o CO

>> CM o m in in

fO « • « • • Q CM CO o CO VO CM CO CM CO

CM in

a • • • • • VO o r“ CM fmm in 41 41 41 41 41 4! CM 00 CM CO

>> VO VO r“

10 • o CO o VO CO

CM CO CM r“ CO r—

hs. as CO in in

JD • • « • • VO O o f~ o •—

41 41 41 CM 41 41 >» VO CO • LO CO CO in VO O • • • • • CO in r— CM

CM CO CM CO O oo CJ> as

(0 • • • • • • CM CM fmm r~* o r->* 41 41 41 41 41 41 VO VO o in CM

r0 o r-~ o\ CO (O O • • • « • • vr r“ CO o c*> CM CO CM CO f—

tA l/> 4-> CJ Cl

10 XI in CM as OO VO o 1- O o as o in CM o 3 3 4J X> • • « « O P c -o in CO in O. a.

Oi

C CM CO CM #—•

CO r~ E E u

c:o L. S- o O) to XI Cl E

<0

u o c c

f—

l/l •r* o 01 r— c u O X> T>

OJ

u c o 01 x: 1 o 1. w o cx o o o c o 1 Ol 4-» 0> c >^ o O 1/1 • V/) J= 0) SI u L. CL JC 4-> •M O c ' c: p Ol 0> •r— o o C o e c XL *r* o u •r* V> 4->

O

M o o fO

n 3 c x: 1 4~> piw 0) o VO c o O

jC 1 * <u V/*! lO

a. CM CM CM Cl »0 Si 80 j
Phenols

in

Industrial

Wastewater

Stability

Study E

CLO.

to

•!-> C

0>unoo

r—

rO ro o CJ LO CM

m • • • • •

-i-i CJ r— o o O

r— 3 H 1 41 -II 41 -M

q; CT> o\ o O

CJ CO VO LO

n3 • • • • • Cj rc CO o CTi CO

D. LO r“ r- rto CO LO CTi CM

r— « • • • • ^ 4-> r-“ r—

o O o 1— 3 41 -II 41 41 41

Q> CO cn <T> CO >>Z LO CJ CO CO o • • • • o nr CO o r—

o. lf> CJ r— •— r—

r~ in LO CM CTi

O fO • • • • • o> ^ CJ o O O r—

ro 4-> 41 41 41 41 41

r3 VO

O CJ

(U

O CM CTi 00 o • • • • • ro CO CO CTi o rn LO r— f— r— r—

o.

VO LO CO o

K£> r— o CD , 1-^ o% • 41 41 41 4i 41 ro O LO CTi O LO

>> r-* LO CJ CM CM

to nr • • • • O CL KO r-* r-

VO r-“ r“ *” r—

r— CM

VO cn LO CM CO

<o • • • • • VD S- CM o O r— O

0\ 4-> 41 41 41 41 41

rs CO CM LO LO

>, a; CJ>

O

O LO

to ar « « • • • o f— CTi CO

re LO r— r— r— r—

CL LO ro CJ CTi CO

r—

O CD

OO CD

KO • 41 41 41 41 41 CO LO LO CM

>> to

O CM «=J- CTi <0 n: • • • • O CL LO o o 1— LO

r~ CM r—

CJ

r— VO CM CTi <o • • • • r— i- o o O o KO •*-> 4! 41 41 41

r5O CO r“ CM

>0 cu r— CO CO CM

ro rz • • • * o VO o CTi 3C LO

O. • LO ro ro VO

C> o cr> CO

vj* • 41 41 41 CO 41

c*> CTi VO • CTi >> CJ r— VO CO

lo nr • • « • Q CL CO CO o *“ •— r— r“

VO CO CO CTi

csj CO o o o O • 41 41 41 41 41 * CO VO r* O ro CO o VO CO Q nr • • • • « CL VO CM o VO

LO CJ r— r”

r~

fO CJ CJ CTi o i- • • • • CvJ •J o o O n> 41 41 41 41 41 >> 0.) VO CT^ CTi CO r—

to 7'll VO O • • • • • n: LO o CTi Q. LO r— r~~ co

4-> to *o lO

O LO o • S- Q> LO CO VO CJ O 4-> • • • • o C XJ CO o CTi Cv

G) <t «— f—

r— f-*» VO

O r“

c:o 4-» o lO *o r— CJ O u

f—

in o O o 4J c u tA

CJ o

-C CJ

O f— cv o L. C o f— CJ <u cr >i o 5

.c CJ x: S- cx _c: in o o. C) •r* c»

X- o E c r~

r-* CJ S- •rD O r-* 4-> C_) rj D c jr: »i~ 1 CX

Q> CD V'.i t:

.fJ. 1 1 (i. CM CM CJ

u

81
stability

of

Selected

Phenols

In

Distilled

Water

O U*) LT) LO • • * • CM o r— O O o m +1 +1 41 41 41 5s o O ID C7% f—

to • • • • • o to CM CM CO CM in ro l£> CM

*o «o o\

u • • • • • S o o CO CO , « CO +1 41 41 41 41 >> 00 o r— 00

>0 o o cn 00 CO CJ m CO \o CO

CO in Ot CO

u • • • • • COo o o o o

to 41 41 +1 +1 +1 >» m GO ir> to CO

(0 • • • • • o o CM CM CO CM in CO VO CO

CO Ol CO

u • • • • Ot

(3 o o o

41 41 41 41 41 >> O VO in CO

<0 • • • • • Q r* CO CM m CO VO CO • 0> cn

•• r— 01 <u in CO o> VO o 3 n o • • • • • O. O o

in o o o o CO E cx.

X rs. Id E E

41 41 41 41 41 Id Id

(U 5s O in in > o 0>

to • • • • c o r»* in as in <4- 4> o CM in CO VO CO

4- 4-

OOO

CO cn cn V C/) cn cn f— CM r“ o\ CO >> 5s >»

u • • • • f“

CM o CO Id Id Id as c c c

41 41 41 41 +1 5S Id Id Id X Id CM CM VO VO CO O. 01 o 0) o • • • • • Id 4> 4-> 4-> CM r^t. o as k Id Id Id CM in CO CO Ok u u u o «T“ «T“ 4> y !

Id CL Cl

X c5 k k k

CM t. 4-> 4> 4J ja • • • • JZ

CO o o o o u E E 1

5s 41 41 41 41 41 •o e Ok

Ok

Id •»— 4- 4- 4- o cn a\ CO CO 3 • • • • • cr *o "O •o

C7\ CO in 00 01 O’ O) in CO r-N. CO C c c

•r* •?— •r* o> Id Id Id u 4> 4-> 4-> c X X X R) o o o E u O -J c o 01 o>

•r* •»— o Ok as Ok

t- 4-> —1 <- Id Id Id 4* Id E u k k k

QJ t-w

O CO CO CO a* (U P 0> E 4J • • • • « a. > > >

•rC -O r“ 00 Id Id Id > 01 CM in CO CO JC

#0O *0 cn •o S3 *o

k. c -o •t— 01 0> 01 U) O < JC c c c O >> X X X

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a 3 X X X o t/t 4» 4J 4> c <o 0> 01 4-> 4» 4> X E C c C

cx P 0> 0) vt in in in 5% c 0> P P X o k k k c w CL CL X o 0> O) O) 01 Q E •a k •k k

S. o •t-*u E x; k 1/) in in O O O 4-> H- c 4-» 4-» 4-» O r*“ (/» *A X 1 01 P 0) P Q. VO u O C u U Id * c i/k in in

Q> o o sm NT o CJ P • o CC o: < o:

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V

82 f
81-BCN-ENERGY RELATED POLLUTANTS AND EFFECTS MONITORING AND ASSOCIATED

METHODS AND TECHNIQUES

1 . Radiological Pollutant Quality Assurance

1 .a. ^^^Th Solution

Thorium-232 is a radionuclide whose presence is of concern when in

effluent and run-off waters from some types of mines, ore mills, and tailing

piles, and in certain drinking water supplies. This calibrated solution

of ^^^Th is for laboratories that assay these waters. The starting material was all thorium nitrate, chosen so that the ^^^Th progeny would be in

radioactive equilibrium. The ^^^Th content was assayed by isotopedilution mass spectrometry and confirmed by counting. Two impurities were observed and measured: ^^°Th by means of a-particle spectrometry with a silicon surface-barrier detector, and ^^®Ra by means of

Ge(Li) detector spectrometry. The a-particle spectrum is shown in

Figure 13, and the Report of Calibration is given at the end of this section.

Two hundred ampoules of this solution were provided to EPA-LV.

1 .b. Mixed Radionuclide Solutions

Two mixed radionuclide solutions were needed by EPA to distribute

to laboratories that assay for radionuclides in drinking water. One

solution mixture is a ten-fold dilution of the other. Each mixture

contains ^H, ®°Sr-^°Y, ^^“"Cs, ^^®Ra and its progeny, and natural uranium

and its progeny. The ^^®Ra and natural uranium components were developed

earlier in this multi-year program; the ^^**Cs solution was calibrated

specifically for these mixtures. A Report of Calibration for one of the

mixtures is given at the end of this section.

83
o

I

I,

84

200

400

600

800

Figure

13

CHANNEL

NUMBER
U.S. DEPARTMENT OF OJMMERCE

NATIONAL BUREAU OF STANDARDS

WASHINGTON, O.C. 202S4

REPORT OF CALIBRATION

THORIUM-232 SOLUTION

• prepared for the

Quality Assurance Division

Environmental Monitoring and Support Laboratory

U.S. Environmental Protection Agency

Las Vegas, Nevada

This solution consists of thorium-232 and progeny in equilibrium in approximately

4.0 grams of one-molar nitric acid in a flame-sealed borosil icate-glass ampoule.

The solution v/as prepared by dissolving old thorium nitrate in dilute nitric acid

and filtering the solution through a membrane-type filter having 0. 3-micrometer

openings. Information from the supplier about the thorium nitrate is given in the

appendix to this Report.

Two hjjndred and twenty ampoules containing approximately equal portions of this

solution v/are prepared. Six of these ampoules were assayed for thorium concentration by isotope-dilution mass spectrometry in May 1979. These assays by the

Inorganic Analytical Research Division, National Bureau of Standards, are described

in the attached memorandum. The mean value from the assays is 0.04738 gram of

total thorium per gram of solution. The total uncertainty in this value is 0.5

percent. ,

The radioactivity concentration of thorium-232 in the solution, which was calculated

from the mass-spectrometric value and the conversion factors and constants in Table

1, is

*1.92 x 102 s-ig-i ± 1.8^*.

I In making this conversion, all of the thorium was assumed to be thorium-232, on a

inass basis.

The^uncertainty in the radioactivity concentration, 1.9 percent, is the linear sum

of tne total uncertainty in the mass-spectrometric value and three times the un- certainty in the thorium-232 half life.

The thorium nitrate from which this solution was prepared contains radium-226 and

tnorium-230 impurities. An ampoule of the solution was assayed for thorium-232

and radium-226 by measuring the emission rates of gamma rays from the decay of their

'respective progeny with a Ge(Li )-detector spectrometer. The radioactivity concentraof thorium-232 obtained from this assay agreed, to within four percent, with the

value derived from the mass-spectrometric assays. The ratio of the radioactivity

concentration of radium-226 to that of thorium-232 was 0.010 ± 0.003 in July 1979.

85
Tht thon*uB^230 to thoriua-232 activity ratio of a dried deposit of this solution

was calculated frow the results of silicon surface-barrier-spectrometer measurements to be 0.15 ± 0.01. The radioactivity concentration of uranium-238 was estimated from the alpha-particle spectra to be less than 0.5 percent of that'of

thorium-232, and likewise for uranium-234.

TABLE 1. RELEVANT CONVERSION FACTORS AND CONSTANTS

Half life of 232jh = (1.405 ± 0.006) x lO^o y

Atomic mass of = (232.038053805 ± 0.000002515) amu (2)

Avefadro constant * (6.0220978 ± 0.0000010) x 10^^ (2)

Length of tropical year * 3.155693 x 10^ s

^®^Based on the ephemeris second.

REFERENCES

t

< ! 1) M. Pw Schraorak, "Nuclear Data Sheets for A=232, 236, 240“, !' cl . Data Sheets, i 165 (1977).

'

2) A. H. Uapstra and K. Bos, "The 1977 Atomic Mass Evaluation, Part I. Atomic ; Mass Table", Atomic and Nucl . Data Tables , 19 , 177 (1977).

3) Pvecent, unpublished value. National Bureau of Standards. !

I For the Director, i

I

j/\j_ j

W. B. Mann, Principal Scientist ! Radioactivity Group

i Center for Radiation Research

March 12, 1980 I

f

:• \

-I

!

.

!

86
APPENDIX TO REPORT OF CALIBRATION

TBORIUM-232 SOLUTION

The following set of data about the tnorium nitrate used for this solution was

provided by the supplier, and is given here for information only.

The thorium in the compound, Th(N03 ) 4

* 6H20 , was purified in 1906. Spectrophotometric assays of the compound in 1954 gave these results for some impurity metals.

Element Content^ Ppm

Li < 5

Na < 25

K <5

Ca 3

Rb < 5

Sr < 3

Cs < 25

Ba 3

i'I

87
(wcv. u-u)

U.S. DEPARTMENT OF COMMERCE

NATIONAL. BUREAU OF STANDARDS

WASHINGTON, D.C. 20234

REPORT OF CALIBRATION

MIXED RADIONUCLIDE CALIBRATED SOLUTION HI

prepared for the

QUALITY ASSURANCE DIVISION

U.S. ENVIRONMENTAL PROTECTION AGENCY

LAS VEGAS, NEVADA

This calibrated solution consists of hydrogen-3, strontium-90-yttrium-90, cesium134, radium-226 and its progeny, radium-228 and its progeny, and uranium of

natural isotopic composition and its progenies in approximately 4.2 g of carrier

solution in a flame-sealed, borcsilicate-glass ampoule. The carrier solution is

1 HMO3 containing approximately 10 yg each of stable strontium,yttrium, cesium,

and barium per gram of solution, and is approximately 0.1 M in HCl. The ampoule

contains part of a master solution which v/as prepared by gravimetric additions

of calibrated solutions of the radionuclides to a known mass of the carrier solution.

The radioactivity concentrations on January 1, 1980, the total uranium concentration

by mass, their uncertainties, and the half lives used in the decay calculations are given in the attached table.

The hydrogen-3 used in the preparation of this mixture was Standard Reference

Material (SRM) 4927-B. The strontium-90-yttrium-90 was a portion of the solution

from which SRM 4919-D was quantitatively prepared. The activity of the cesium-134

solution v/as measured using the National Bureau of Standards (NBS) pressurized “47r“Y

ionization chamber that had previously been calibrated with a cesium-134 standard

in terms of a radium-226 reference source. The radium-226 used in the preparation

cjf this mixture was a portion of the solution from which SRM 4953-B v/as quantitatively prepared. The radium-228 was the NBS calibrated solution of July 1977. The

uranium in the mixture came from the NBS calibrated solution of natural uranium of

November 1978, plus part of the more concentrated solution from which the 1978

uranium solution was quantitatively prepared.

The total uncertainty in the radioacti vity concentration of each radionuclide and

in the total uranium concentration by mass is the linear sum of the 99-percent

confidence limits for the mean and the estimated upper limits of conceivable systematic errors in the calibration, the decay calculation (where applicable), and

the preparation of this solution.

88
Each radioactive component of the mixture was examined for gamma-ray-emitting

ij impurities using germanium-spectrometer systems that covered the energy region from

'1 90 to 1900 keV. Rad.ium-226 and its progeny were observed in the radium-228 and*

uranium solutions. Radium-228 and its progeny were observed in the uranium solution.

The radium-226 and radium-228 impurities are included in the total radioactivity

ji concentrations reported for these nuclides. No other gamjna-ray-emitting impurities

!! were identified.

For the Director,

1 Attachment

i March 1980 Radioactivity Group

Center for Radiation Research

89
MIXED RADIONUCLIDE CALIBRATED SOLUTION Ml

PARENT s-^‘l ON L NCERTAINTY, %

RADIONUCLIDEJAN. 1, 1980 RANDOM

(99% C.L.)

SYSTEMATICTOTAL HALF LIFE,

YEARS

2353 0.2 0.5 0.7 12.35 ± O.Ol(l^)

90sr 14.5 1.3 0.8 2.1 29.12 ± 0 . 24 (b)

13^Cs 104.3 0.4 1.2 1.6 2.062 ± 0 . 005 (b)

226Ra 8.88 0.1 1.6 1.7 1600 ± 7(b)

228Ra 7.28 1.4 1.9 3.3 5.75 ± a-.03(c)

234u 12.2 3.9 1.3 5.2 (2.445 + 0.010)

X 105(c)

235u 0.5851 0.1 0.3 0.4 (7.038 ± 0.005)

X loS(d)

238u 12.68 0.1 0.3 0.4 (4. 463 + 0.003)

X 109(c)

TOTAL U 1.028(a) 0.1 0.1 0.2

1 igrams of U per gram of solution, by isotope-dilution mass spectrometry.

The radioactivity concentrations of the uranium isotopes were determined

from this concentration, the isotopic abundances measured by mass spectrometry,

and the respective uranium half lives.

(*^)ncRP Report No. 58, App. A, National Council on Radiation Protection and

Measurements, Washington (1978).

(^)d.C. Kocher, ORNL/NUREG/TM-102 , Oak Ridge National Laboratory, Oak Ridge,

TN (1977).

(^)m.R, Schmorak, Nucl . Data Sheets, 91 (1977).

90

i
vuHTEMPORA •’ 1 VART I CU L A

7’

. *•

‘fHi

V . i.Xoyii A» Cua k’ ^pv

Center fci* Analytical ClitiRi at rv

Mationdl Burt'avj oP S^ -ndardt

Washington, 1).C

: ’appendix 1

y.-- 4

'

•<" ' >•

W\ •* '-1, * Vi> . 'IM' ,

V'

; m

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; Atmo < p h^rtc L i v e

jiearch Labs , Octobai »

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: „ < V..

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piiK' •' > -

I 93.

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1

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parw i'

mxo^ JA.H iwaiflt; '

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soiunw hi

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S’ " "

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12.35 t O.l.

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2.062 s 0 ; 005.W I ^

1600 J

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s •^r€ t-ii ‘‘--S'-

Lr . mt 0" Ratfr*tlot>.i»r«Ae^<ff ^n<t;j

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^ f k- k ^ lU.

ld# V*

,/S ,A*» .,’f , ' *'• .-.-
CONTEMPORARY PARTICULATE CARBON*

Lloyd A. Currie

Center for Analytical Chemistry

National Bureau of Standards

Washington, D.C. 20234

To be published in the Proc. of the International Symposium on

Particulate Carbon: Atmospheric Life Cycle, sponsored by OM

Research Labs., October, 1980.

•k Contribution of the NBS, not subject to copyright.

91
ABSTRACT

Advances in natural radiocarbon measurement techniques

have made it feasible, for the first time, to assess the contribution of biogenic (contemporary) carbonaceous sources to

individual chemical fractions in milligram quantities of atmospheric

particles. Isotopic measurements for source reconciliation are

doubly important when dealing with pure species, such as methane,

carbon monoxide or elemental carbon, because they represent the

only compositional information obtainable. Elemental carbon is of

special interest in this regard because of changing energy patterns

associated with both contemporary (wood-burning) and fossil

(diesel fuel and unleaded gasoline) carbon. Following a review

of the assumptions underlying the use of radiocarbon as a biogenic tracer and the status of minicounter and accelerator

techniques for the assay of milligram and microgram samples,

a survey is presented of recent observations on urban and

rural carbonaceous particles. Results for these particles,

which have been fractionated according to size or volatility,

have exhibited the full range from fossil to biogenic source

dominance.

Keywords: Accelerator mass spectrometry; air pollution sources;

atmospheric particulate matter; biogenic carbon; carbonaceous

particles; carbon-13; contemporary carbon; elementary carbon;

fossil fuel; natural tracer; radiocarbon; urban and rural

carbonaceous aerosols.

4

92

k
INTRODUCTION

One o£ the foremost questions involved in our understanding

of the atmospheric cycle of particulate carbon is the quantitative assessment of perturbations introduced through human

activities. Although natural emissions of carbonaceous gases

and particles clearly predominate on a global scale [1-3], man's

use of coal, petroleum, natural gas and wood as fuel is known

to have very severe consequences for particulate pollution

ranging from local (especially urban) episodes to long-range

effects [3-6]. A major objective of our research program is

therefore the deconvolution of sources of atmospheric carbon

through the analysis of ambient samples, with special emphasis

on fine particle (<2 ym) elemental carbon, because of important

effects on health, climate and visibility [7-9].

12 13 14 Naturally-occurring isotopes of carbon -- C, C, C (radio

carbon) -- provide important tools for the deconvolution process,

for their isotopic concentrations (^^C/^^C, differ

significantly among different classes of potential source material.

As indicated in Table 1, for example, measurement of <S C -- the

deviation of the ratio from that of the PDB standard [10] -

allows one to distinguish between carbon originating from species

such as carbonate minerals, marine plants, petroleum and natural

gas, or carbon from and terrestrial vegetation [11,12].

Of greater importance, radiocarbon serves as a unique

discriminator between contemporary biogenic (e.g., vegetation)

and fossil organic matter [13]

.

The measurement of radiocarbon

93
thus serves as a very important complement to indirect methods

(chemical element balance, factor analysis, dispersion modeling)

for inferring sources of ambient carbonaceous particles. Its

special characteristics are that it is a direct and unique

indicator of biogenic carbon, and that, along with it is

robust with respect to changes during transport. Also, for

single chemical substances such as elemental carbon, isotopic

measurements provide the only compositional information

attainable

Since the preceding conference on atmospheric particulate

carbon, at which we reported the first radiocarbon results for

milligram quantities of carbonaceous particles [14] , there

have been some important societal and technical developments.

In the first category, the need for a reliable, direct tracer

for carbonaceous emissions has been magnified because of

increases in wood-burning and in the use of diesel fuel and

unleaded gasoline. (The relative decrease in the mix of

pre-1975 automobiles is, in effect, causing the "loss of a tracer," i.e., lead upon which the chemical element balance

method heavily depended.) Technical progress includes improved

control and demonstrated reliability of our mini-gas proportional

radiocarbon counting system, and most importantly, the introduction of the accelerator method of atom counting [15,16], which

is likely to extend the range of sample sizes downward by another

three orders of magnitude, to about 10 yg of carbon [17].

9h
This development is of special consequence for elemental carbon,

because this chemical form appears to be optimal for placement

in the tandem accelerator sputter ion source [18] , and the

(sampling) blank for elemental carbon appears to be far lower

than that for organic carbon [19]

.

Following a brief review of recent developments in small

sample radiocarbon measurement and critical assumptions involved

in interpreting the resulting data, we shall present a summary

of several recent applications to urban and rural ambient

aerosols which have helped to establish the validity of the

method and which have provided a direct measure of the importance

of biogenic sources on individual chemical and physical (size)

fractions of carbonaceous particulate matter.

BIOGENIC CARBON TRACING -- METHODS AND CAUTIONS

The phenonemon which makes possible the use of radiocarbon

as a direct tracer for sources of biogenic carbon is the same

as that upon which radiocarbon dating is based [20]. That is,

all living matter is in (approximate) isotopic equilibrium

with atmospheric CO2 which continually acquires radiocarbon

following cosmic ray neutron capture on ^^N in the atmosphere.

14 Unlike radiocarbon dating, in which C concentrations are

related to age, biogenic carbon tracing is based on isotope

dilution -- the ^^C concentration in an ambient sample

reflecting directly the mixing ratio of contemporary ("living")

carbonaceous material and fossil material. Carbonaceous

95
substances of intermediate age -- e.g., 500 to 20,000 years --

are largely absent from atmospheric particulate matter.

Progress in the measurement of natural radiocarbon is

indicated in Table 2. Following its discovery by W. F. Libby

in the late forties, radiocarbon dating was recognized with

a Nobel prize in 1960, and its use has continued to increase

since that time. The method, as generally practiced, is

characterized by excellent precision, but required sample sizes

are extremely large (by air pollution standards) and chemical

or physical separations are rare (with the exception of simple

”pretreatment" , and the extraction of cellulose for tree ring

dating) . Rapid progress in measurement techniques for small

atmospheric samples was marked by (a) the introduction of

mini-counter liquid scintillation and gas proportional counting

in 1976 [21] for 100 mg and 10 mg size samples, respectively,

14 and (b) the development in 1977 of direct C atom (rather than

8-decay) counting by means of high energy nuclear accelerators

[15,16], Although the first dedicated radiocarbon accelerator

has not yet been installed, it has been demonstrated that natural

radiocarbon may be measured in samples containing only 10-20 yg

of carbon [17].

During the past three years, the mini-gas proportional

counting method has been applied to a number of interesting

problems, ranging from gas and particulate matter in the

atmosphere to organic species in sediment [22] , and it may be

96
considered validated and almost routine in operation. Atom

counting (with accelerators) is still very much in an exploratory stage, but its enormous sensitivity (with consequent

sample size reduction) will lead to very broad applications.

As shown at the bottom of Table 2, based on current measurement

parameters, decay counting of 10 mg of contemporary carbon

yields a Poisson imprecision of about 6 percent (415 sample

counts, S/B-2) , whereas atom counting of 10 yg yields a value

of 3 to 4 percent (786 counts, S/B>>!) . The latter method

requires an overall measurement time of hours rather than days.

Many other factors which affect the time, cost and reliability

of the alternative methods are beyond the scope of this paper.

What the two methods share, however, is the exciting opportunity

of determining the isotopic composition of individual chemical

species and size fractions in atmospheric samples selected

according to time and location.

A number of assumptions and cautions involved in the

measurement and interpretation of radiocarbon data are highlighted in Table 3. With respect to the (two-source, isotope

dilution) model the only currently significant assumptionlimitation is connected with the variations in the biosphere.

The three principal causes of these variations are (a) solar

modulation of the cosmic rays, (b) dilution of atmospheric

radiocarbon with fossil fuel generated CO

2

(Suess effect) and

(c) artificial radiocarbon production (primarily associated with

91
atmospheric nuclear tests) [23]. As shown in Figure 1, the

perturbation due to nuclear testing predominates, causing

about a 30 percent radiocarbon excess in currently-living matter.

Because of this, radiocarbon concentrations, relative to the

"modern standard" (0.95 x NBS Oxalic Acid SRM # 4990-B) must be

divided by 1.3 to estimate the fraction of contemporary (biogenic)

carbon. When the biogenic source spans a number of years, the

situation is less straightforward. If a 60 year-old log is

burned in a fireplace, for example, its average radiocarbon

contribution is enhanced by an additional 9 percent due to the

wood formed during the period of major nuclear testing [24].

(One must integrate the input function. Figure 1, over the life

of the vegetation taking into account also the rather small

correction for radioactive decay.) Unlike most chemical species,

however, radiocarbon directly tracks the biospheric source emissions,

and the isotope ratio is extremely resistant to changes during

transport, from source to receptor site.

Most of the subtle, yet critical sources of error in the

low-level counting of radiocarbon have been discussed previously

[14,21]. To assure reliability we now routinely monitor six

parameters during counting periods; and our measurements generally

encompass five (hierarchical) levels of quality control.

New information concerning two other factors, developed

within the past year, bears special mention. These are the

blank and isotopic heterogeneity. Until recently sufficient

98
material and information concerning the blank was lacking.

Blank quartz-fiber filters obtained recently from R. K. Stevens,

of the U.S. EPA, however, gave us sufficient filter-blank

carbon to carry out a radiocarbon determination. The result,

that the blank was indistinguishable from contemporary carbon,

must be considered when measuring samples having less than a few milligrams of carbon.

Isotopic heterogeneity, variation of the isotopic ratio

among different chemical and/or size fractions of the ambient

sample, is exactly analogous to the problem of non-contemporanei ty

in radiocarbon dating [25]. That is, although the overall

radiocarbon concentration may be meaningful in terms of the

average biogenic source contribution (or age) , significant

information loss takes place unless measurements are made on the

individual fractions. As will be discussed in the next section,

we have observed particle size and volatility-related isotopic

heterogeneity in carbonaceous particulate samples; therefore, the

relative mix of biogenic and fossil source contributions must

differ among the different fractions, and conclusions based

upon just the average isotopic composition (TSP) may be relatively

weak or ambiguous. A corollary to these observations is that

quantitative chemical recoveries (from particles to pure CO

2

counting gas) are mandatory; otherwise even the estimated average

isotopic composition may be biased due to selective chemical

losses

.

99
EXPERIMENTAL RESULTS CONTEMPORARY CARBON IN URBAN AND RURAL

AEROSOLS

1 . The isotopic dimension; chemical and physical selectivity . Initially, nini-radiocarbon measurements were applied in a simple

dichotomous manner to determine whether urban and rural ambient

aerosols were typically "anthropogenic" (fossil) or "natural"

(biogenic, vegetative) in origin; the results were not surprising

[14] . More recently, it has become important to assay radiocarbon in samples from specific episodes which implied serious

health consequences (especially involving fine carbonaceous

particles) or where significant contemporary carbon emissions,

from wood burning or vegetative emissions, were presumed present.

Under these circumstances it has become necessary not just to

14

assay C in the Total Suspended Particulate matter (TSP) , but

also to examine individual chemical or size fractions. In

addition to this "serial selectivity", "parallel" measurements

of other chemical or physical characteristics of the samples in

question have served two important purposes: (a) validation of

the isotopic conclusions (or the converse, the Chemical Mass

Balance [CMB] conclusions), and (b) complementarity (orthogonality) needed for extracting more source information than

either approach alone could provide.

The first, quality control, application has been and will

continue to be of major importance in the development and

validation of new methods; its value rests especially on the

uniqueness of the radiocarbon tracer, and on the complete

independence (with respect to underlying assumptions and methods)

100
of the alternative (isotopic, chemical) techniques. The second

aspect, which implies complete integration of the isotopic dimensions with the chemical characterization, provides the most powerful

use of the isotopic data, and it should lead to one of the more

reliable and precise approaches to future efforts in receptor

modeling [26,27]. The summary in Table 4 of one rural and three

urban ambient aerosol investigations, all completed within the

last two years, illustrates both of these aspects.

Is is noteworthy that the percent of contemporary carbon

observed in these investigations covered the full range from

10 ± 3 percent to 107 ± 15 percent. (Both of the extremes

represented periods of severe particulate pollution, but from

very different sources!) A general observation from these

studies is that contemporary sources do contribute significant

amounts of particulate carbon to the ambient aerosol from

vegetative emissions during the summer (Los Angeles, rural Utah),

and from wood-burning in the winter (Portland, Denver).

Continuing severe pollution episodes in Los Angeles and Denver

("Denver brown cloud") were the geneses for two of the investigations, and the remaining two were connected with special

situations involving contemporary (Portland, field and slash

burning) and fossil (Utah, oil shale tracts) carbon. Of

particular importance is the nature of the supporting data.

As shown in the fourth column of Table 4, serial or parallel

information on particle size, emission/dispersion modeling.

101
and inorganic or organic composition were intimately involved in

the overall efforts at source reconciliation.

2 . Patterns of results and conclusions

The isotopic data served as a truly independent dimension

in the urban studies, in that they were more or less formally

combined with chemical, meteorological and emission data to

infer sources of the carbonaceous particles. Emission, chemical

and radiocarbon data collected for Denver samples, for example,

were consistent with the conclusion (for the sampling period

in the winter of 1978) that wood-burning was responsible for about

one-fifth of the carbonaceous aerosol and two-fifths of the

visibility-reducing elemental carbon [28,29], Qualitative

support for the 54 percent contemporary carbon in the Los

Angeles study was given by observations of significant amounts of

primary or secondary organic species characteristic of fossil sources

(a large hump of branched cyclic compounds in the GC trace of

the hydrocarbon fraction, polycyclic aromatic hydrocarbons,

and dicarboxylic acids) on the one hand, and species reflecting

vegetative emissions (6 C, odd carbon-numbered high molecular

weight n-alkanes, predominantly even carbon-numbered fatty

acids, 2-ketones, camphor) on the other. It should be noted

that individual size fractions were examined in the Los Angeles

study, and that wind patterns at the location of the receptor

site (City of Hope hospital, Duarte, in the foothills of the

San Gabriel Mountains) favored impacts from both intense urban

smog and forest emissions (carried by night-time winds) [30].
The investigations in Portland and Utah provided important

opportunities for semi-quantitative tests of consistency

between isotopic and chemical data. Table 5 lists results

(and Poisson standard deviations) for ^^C-inferred contemporary

carbon derived from vegetative burning in Portland and vegetative

emissions in Utah. Paralleling the radiocarbon results are independent estimates based on inorganic chemical mass balance (CMB)

in Portland [24] and organic chemical "pattern recognition" (CPR)

in Utah [31]. The general pattern of results is quite satisfactory,

but two special comments are in order. That is, the CMB estimates

(of biogenic carbon) were rather indirect, involving several assumptions, so that the assignment of uncertainties was extremely

difficult. (Overall consistency between the and CMB estimates

would admit an average (CMB) standard deviation of about 9 percent.)

The CPR uncertainties (Utah samples) reflected measurement error

only; sampling and model errors would, of course, increase the

uncertainty intervals. It is interesting to note that K/Fe ratios

(Portland) were qualitatively consistent with the radiocarbon

data, but were subject to large fluctuations.

Finally, let us briefly examine patterns associated with

the Utah and Denver results. Figures 2 and 3 show: the

pyrolysis -mass spectra for the fossil and three vegetative

components contributing to the ambient sample in Utah, and the

resulting separation of these components as shown in non-linear

103
two-space using pattern recognition technqiues. An overview of

the Denver study is given in Table 6, and a three dimensional

projection of the pattern of selected results (TSP) appears in

Figure 4. This figure shows contemporary carbon as a function

of three variables: degree of pollution, percent of volatile

(’’organic”) carbon, and chemical fraction (total carbon,

* ’’elemental” carbon) . General conclusions which may be drawn

from this overall pattern of results are (a) that the radiocarbon blank must not be ignored, (b) contemporary carbon,

comprising up to about 40 percent of the carbonaceous material,

is a significant component -- presumably due to residential

wood burning -- in the winter-time Denver ’’brown cloud”, and

(c) the fossil component is more pronounced: in the elemental

carbon fi^action, with increasing pollution, and with decreasing

volatility.

Three of the major assumptions/limitations in the isotopic

inferences mentioned in the previous section deserve special

comment with respect to the Denver results. First, the average

age of the wood burned was not taken into account in deriving

the results as shown in Figure 4. The maximum likely effect

would be a relative shift of about 9 percent toward fossil carbon.

A The terms organic and elemental are used here in an operational

sense. The ’’elemental” fraction, defined as being non-volatile,

may include high molecular weight compounds as well as amorphous

or graphitic carbon [28,29].

loh
Second, the effect of the blank, which corresponded to about

0.7 mg-C, has been taken into account. Fortunately, the

corrections were small compared to the Poisson counting errors,

since the correction involves assumptions concerning the

chemical and isotopic compositions and variability in the total

mass of the carbon blank [19]. For the samples (Fig. 4) having

the smallest and largest blank contributions -- sample "P" with

23.9 mg-C and sample *’U” with 9.8 mg-C -- the adjustment to the

percent of contemporary carbon was just -1.5 percent and -3.3

percent, respectively.

The third limitation relates to chemical yield. If the

recovery (as CO

2

, counting gas) is non-quantitat ive , isotopic

heterogeneity can lead to bias for the estimated average percent

contemporary carbon; and low yields greatly increase the

error-propagation uncertainties when the volatile carbon

component is deduced from the two (total, elemental) measured

components. For example, the pair of samples, "WD", had

estimated recoveries of 87 percent (total) and 101 percent

(non-volatile) , and contemporary carbon compositions of 26 ± 5

percent and 14 ± 5 percent, respectively. The derived contemporary carbon estimate for the volatile component was 56 ±

26 percent. Obviously, quantitative recovery and direct

14 measurement of C in the volatile component are desirable for

future studies.

105
SUMMARY

Radiocarbon has been demonstrated to be a unique and robust

tracer for contemporary carbon in atmospheric particles.

Utilization of this isotope, together with selective sampling

13 plus measurements of 6 C and inorganic and organic chemical

composition has indicated the importance of a number of specific

vegetative sources coatributing to urban and rural ambient

particles. Semi-quantitative confirmation of the radiocarbon

conclusions has been derived from chemical mass balance

(inorganic species, emission ratios) and chemical pattern

recognition (organic species).

Rapid progress has occurred in the measurement of radiocarbon, in that (a) small (5-10 mg-C) samples may be measured

using mini-gas proportional counters with a method which has

been developed with a high degree of internal control and is

nearly routine in applicability, and (b) the eventual capability

for micro (10-20 yg-C) samples has been demonstrated using

direct atom counting with a tandem accelerator.

Assay of contemporary carbon, which has been carried out

for the first time on a complete blank and on different chemical

fractions of small samples of atmospheric particles, has

indicated isotopic heterogeneity -- viz .

the organic and

elemental carbon fractions of ambient particles have been shown

to depend to differing extents on biogenic carbon sources.

These observations, obtained from measurements of "Denver Brown

Cloud" particles, are analogous to the contemporary carbon

io6
(isotopic) heterogeneity which we observed in different size

fractions of particles collected both in Denver and in Portland,

Oregon. For the particles sampled in these studies, the contemporary carbon fraction -- presumably from vegetative burning --

tended to be concentrated in the organic carbon fraction and in the

fine particle fraction. The overall contemporary carbon

fraction depended greatly on locale and conditions, ranging

from 10 ± 3 percent (Denver) to 107 ± 15 percent (Portland).

Elemental carbon, already important because of its impact

on climate, health and visibility, is of special interest for

radiocarbon measurements. This is because the composition of such

a single chemical species can only be characterized using isotopes,

because it has a very low blank, and because it is a chemically

robust tracer for combustion sources. Finally, elemental carbon

represents the ideal chemical form for the technique having

greatest sensitivity -- accelerator atom counting.

As isotopic measurements of greater sensitivity (smaller

sample size) or improved precision become practicable, it will be

increasingly important to pay attention to three critical

factors: the blank, recovery (and isotopic heterogeneity), and

assumed vegetative age. Uncertainties connected with the

blank are negligible for elemental carbon and slightly smaller

than current Poisson counting errors for total carbon. Isotopic

heterogeneity means that low chemical yields will result in

107
biased contemporary carbon estimates, and important information

loss will occur if individual chemical and size fractions are

not separately analyzed. Vegetation age, if inadequately

corrected for, can introduce uncertainties up to about 10 percent,

due to the injection of bomb radiocarbon during the last two

decades

The next steps to be taken in the application of carbon

isotopes to the investigation of the life cycle of carbonaceous

particles will include sampling at remote sites and advances

in measurement methodology. The latter will include isotopic

enrichment and multiple counter arrays plus exploration of

precision and sensitivity improvements using a dedicated

radiocarbon accelerator. Also, further utilization of chemical

and size selectivity are planned, together with full integration

of the isotopic and chemical data in the source deconvolution

process. For these purposes, efforts will be made to further

characterize a particulate standard reference material, and to

provide a standard data set for receptor modeling.

108
ACKNOWLEDGMENT

The urban and rural studies reviewed in this manuscript,

and to be published in full elsewhere, took place in cooperation

with the following scientists: Portland -- J. A. Cooper (Oregon

Graduate Center), Los Angeles -- I. R. Kaplan (Global Geochemistry,

Inc.)> Utah -- K. J. Voorhees (Colorado School of Mines), and

Denver -- R. J. Countess, G. T. Wolff and D. P. Stroup (General

Motors Research Laboratory) . R. K. Stevens (USEPA) supplied the

blank ("B", Fig. 4). G. A. Klouda and R. E. Continetti of NBS

were largely responsible for the experimental radiocarbon measurements. Grateful acknowledgment is expressed to all of these

colleagues. Partial support for this research was provided by

the Office of Environmental Measurements, U. S. National Bureau

of Standards, and the Energy-Environment Program (EPA- IAG-D6 -E684)

,

U. S. Environmental Protection Agency.

109
Table 1. Carbon Isotope Concentrations Characterizing

Different Sources

PDB standard, Si 3 , [10]. Note that contemporary ('\^1979) C-14

is about 30% higher than "modern standard" (pre-nuclear era, C-14.

(b) C 4 ,C 3 plants represent the two major photosynthetic classes,

[12]. Point @represents a Los Angeles aerosol sample whose

isotopic composition is consistent with 54% temperate (C 3 ) vegetative emissions and 46% fossil fuel [30]

no
<D

X P 3 p CO -H p 0 X X

CO

N o

•H •H 3 € CO 0 r—

u

CO

X 3 CO

O 33 0 u 3 iH 3 P 0 p 33 3 O 3 P o p •H O •H 3 3 f—

2 ceJ > -H P O O X g •H g O X -H oo •H 3} 0 3 PP33 CO HC Pi 3 X 3 X 0 X « 4C •H I-H u PP W Q LO

X S X 00 /—

CO II II p

+-> o /—\ /—\ •H XI Pi 3 > € Pi •H t—\ •H o S Pi •P CO •H O >s •H CO o\« o\o o\® O

COm •H CM lO to 00 o

Pi o U

V / 00

(D 0 CM CM CO Pi Pi o\o v_/ 00 o PU LO /-> V—

•H • OO r-N

C P o • X o OJ o o

•H Pi

w o P oS /—\ • I—

X o

i—H

a 1 v_^ o X ,—\ 3 > 0 •H X w •H e • 'T3 3 3 1 Pi o‘ oo >S 1 cS •H X

t—

4C • Ln

p CO / N

X /—S * O CJ\ Pi 0 g •V X CM 4C ' / ' > 0 o fH CO X o t—\ e Pi o aJ U CJ CJ II II 0 0 «p 00 V > V / V—

>H

u

V / V / P H 3 0 00 00 oo < ' CO p CO oo S 6 3. w w 0 CO < < 0 U cci o o o o s s I—

o rH X

5h 1—

II c O o «P CO P P 3

ccJ

X 3 O 0 00 O o P • ^ 3 u

•H /—\

•H 00 T3 0 o P 3 m

CCJ 0 VO 3 •H o

Oi CO o> 3 3 P ' / iH O o 3 3 ' / u •H 3 0 P O X

OO 3 rH

U 6 3 3 iH 3 3

•H

O rH 3 S 2 P 0 •H O o

Oj

Q P •H

p

Q 3 P < 0 •H U 3 P o o 3 O pin CO pp O X 6 •• o P • 3 3 /—

33 3 3 /—

eg 3 CO

X •H PL,

U

O 3 0 0 o iH CO cr CO X CO

rH •H i-H 1—

•H 3 0 X 3 X CJ u ^

cej 3 6 o H pci CO <

111
Table 3. Cautions and Assumptions

Model Validity

Radiocarbon : * two-source assumption (soil-carbon, nuclear energy,

gasohol)

* ^^C-variations (solar, bomb, Suess effects)

* vegetation age (firewood)

Receptor : * all sources identified

* accurate, reproducible profiles at receptor site

Sample and Sample Preparation Limitations

* the blank

* large particle contamination (spores, insect parts, ...)

* chemical stability, reliable separations (recovery, charring)

Counting Difficulties

* isotopic heterogeneity (non-quantitative recovery)

* background fluctuations (sunspots, barometric pressure)

* radon contamination

* electronegative contamination (efficiency)

* spurious pulses

112
(Uo

c;0 o I—

00

Jh (SI to to CM 0

lh0

Pi /—\ 3O 3 3 ’H to •» O P P 3 bO •H 3 0 *H O 3 P O 6 3 •H *H

•H /—\ •HO bO P iH 0 to 0 to 3 O U »> 0

iH

OU 3 P U 3 3 '3 to

O P 3 0 O 0 3 0 0 3

•H

g ((} P u 0 P m .H

g

O P O rH to -H P P •H 3 CJ 3 •H a to C rH -H '3 P p 3 PQ nd 3 3 3 to 3 O 3 P O bO to 0 P O 3 3

(3 •H to r' 3 to P 3 P 3 ^ 3 to 0 o 3 P 0 g 3 (p

W3 P 3 3 ISl 6 3 6 O P 3 O bOS •H 3 • P 0 U 3 0

•H 3 3 to

u

O 1 rH r3 3 P P O rH CO *H W rH 0 CJ •H

(/) 3 6 3 3 0r^ P •H 3 \-H 3 t+H o O •H *H o iH i<5 *H to U 0 3 0 —

•H •H

u to >s'H •H 3 *H 0

'Id P 3 6 •H o o 1 6 3 bO to to 3 3 ^00 P 3 P O 0 3 3 to 3

+-> c/3

O

N ^ 3 P 6 3 Xi bO

O *H 3 w 3 -H U 3 3 0 3 3 6 O « to s_/ P *3 O P o *H 0 u op

iH

H • • 3 3 LO O P 3 o LO •H 3 3 i—H P 0 O • • o U O P o '!d' p

Ctf 3 e P LO VO

CL, 0 0 ? <? • p p • Q p 3 rH 3 O LTJ 0 u O0 rH rH

bO 1 •H 0 bO 3 3 O 3 3

to •H P to 4-1 *H 0 3 0 3 '3 3 o ,3 3 iH 00 o 3 rH 3 3 3 3 •H 0 -H 3 •H 3 3 3 ^ to > to 0 P to x> O I—

to to > to to to

C/3 to *3

O '3 -H •H 3 3 O nd

O Pt 3 6 P O '3

m o 3 O 3 0 3 'H o O 3 > 3 P to 0 3 >

JP 1—

3 iH 0 0 to tH 3 3 0 *3 rO 0 > bO-H 3 jp Td

oJ •H 3 3 3 -H 0 6 xi 3 3

C_) P 3 ID Lh P > 0 to

D 3 po to0 X iH 3 • 0 '3 0 P

rH 3 bO

D 3 3 3 3 0 O iH < r4 0

rH

O P 3 >

XI

X 3 to 3 3 3 O o 3 0 H P X P Q

113
Table 5. Quantitative Consistency

(percent contemporary carbon)

Portland^^^ Utah^^^

I

1 I

CMB, Emission Ratios CPR, Py-MS

(inorganic) (organic)

107 + 15 (field) 99

I (sage) 64 ± 2

111 + 19 (slash) 85 64 ± 4 1 (pine) 11 ± 2

83 + 16 (slash) 78 \ (juniper)

79 + 12 (slash) 97 fossil (shale) 24 ± 2

57 + 12 (wood) 79

fal ^ Fine particle fraction (<2.5 pm), corrected

for wood age (ref. [24]). (CMB = Chemical Mass Balance.)

Ref. [31]. Chemical Pattern Recognition (CPR) . Figures

represent the derived percent contributions from the

indicated sources.
Table 6. Denver Samples (Overview)

Conditions : Sunny, cloudy, -20 °C to +10 °C

Clear, weekend, weekday, polluted

[7. to 43. yg-C/m®]

Fractions : Total, non-volatile, fine

Percent Volatile :

25. to 70.

Percent Recovery (COa) .

70 to 108

Mass (carbon) :

5.6 mg to 23.9 mg 2 [Blank =0.7 mg; '^ 8 . yg/cm ] Percent Contemporary :

10 ± 3 to 55 ± 13

115
References

[1] Covert, D. A., Charlson, R. J. , Rasmussen, R. , and

Harrison, H. , ’’Atmospheric Chemistry and Air Quality”,

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[2] Kneip, T. J. , Lioy, P. J. , Eds., ’’Aerosols: anthropogenic

and natural sources and transport.” Annals N.Y. Acad. Sci.,

558 , 1-618, (1980).

[5] Bolin, B., ’’The impact of production and use of energy on

the global climate”, Ann. Rev. Energy, 197 (1977).

[4] Cooper, J. A., Watson, J. G., and Huntzicker, J. J. , ’’Summary

of the Portland aerosol characterization study”. Paper No.

79-24.4, 72nd Air Pollution Control Association Meeting,

Cincinnati, Ohio, June 1979.

[5] Courtney, W. J. , Tesch, J. W. , Russwurm, G. M. , Stevens,

R. K., Dzubay, T. G., and Lewis, C. W. , ’’Characterization

of the Denver aerosol between December, 1978 and December

1979”, Paper No. 80.58-1, 75rd Air Pollution Control

Association Meeting, Montreal, Canada, June 1980.

[6] Rahn, K. A., Brosset, C. , Ottar, B., and Patterson, E. M.

’’Black and White Episodes, Chemical Evolution of Eurasian

Air Masses, and Long-Range Transport of Carbon to the

Arctic”, Particulate Carbon: Atmospheric Life Cycle , GMR

Symposium (Warren, October 1980)

[7] National Research Council. Controlling Airborne Particles . National Academy of Sciences: Washington, D. C., 1980.

Il6
[8] Geophysics Study Committee, Energy and Climate , NRC Geophysics

Research Board, National Academy of Sciences, Washington, D.C.

1977.

[9] Novakov, T., Ed., Proc. Conf. Carbonaceous Particles in the

Atmosphere . LBL-9037 CLawrence Berkeley Laboratory) 1978.

[10] Craig, H. , Geochim. Cosmochim. Acta, _3, 53 (1953).

[11] Calder, J. A., and Parker, P. L., Stable isotope ratios as

indices of petrochemical pollution of aquatic systems,

Env. Sci. Tech., 1_, 535 (1968).

[12] Troughton, J. H. , "Carbon Isotope Fractionation by Plants",

Proceedings of the Eighth International Radiocarbon Dating

Conference, Lower Hutt, New Zealand, Vol. 2, 421, 1972.

[13] Currie, L. A., and Murphy, R. B. , "Origin and residence

times of atmospheric pollutants: Application of ^‘^C", in

Methods and Standards for Environmental Measurement , W. H.

Kirchoff, Ed., NBS Spec. Pub. 464, National Bureau of

Standards, Washington, D.C., p. 439, Nov. 1977.

[14] Currie, L. A., Kunen, S. M. , Voorhees, K. J., Murphy, R. B.,

and Koch, W. F., "Analysis of Carbonaceous Particulates and

Characterization of Their Sources by Low-Level Radiocarbon

Counting and Pyrolysis/Gas Chromatography/Mass Spectrometry,"

Conference on Carbonaceous Particles in the Atmosphere , University of California, Berkeley, 1978.

[15] Muller, R. A., "Radioisotope dating with a cyclotron,"

Science, 196, 489 (1977).

117
[16] Gove, H. , Ed., Proce edings of the First Conference on

Radiocarbon Dating with Accelerators , University of Rochester

1978.

[17] Currie, L. A., Klouda, G. A., Elmore, D. , Ferraro, R. , and

Gove, H. , "Accelerator Mass Spectrometry and Electromagnetic

Isotope Separation for the Determination of Natural Radiocarbon at the Microgram Level," (in preparation).

[18] Rubin, M. , "Sample Preparation for Van de Graaff Accelerator

Dating," in L. A. Currie, Ed., Nuclear and Chemical Dating

Techniques , American Chemical Society Symposium Series, 1981.

[19] Stevens, R. K. , McClenny, W. A., Dzubay, T. G. , Mason, M. A.,

and Courtney, W. J. , "Analytical Methods to Measure

Carbonaceous Content of Aerosols," Particulate Carbon : Atmospheric Life Cycle , GMR Symposium, Warren, Oct. 1980.

[20] Libby, W. F. , Radiocarbon Dating , University of Chicago Press

Chicago, 1952.

[21] Currie, L. A., Noakes, J. , and Breiter, D. , "Measurement of

Small Radiocarbon Samples: Power of Alternative Methods for

Tracing Atmospheric Hydrocarbons," Ninth International

Radiocarbon Conference , University of California, Los Angeles

and San Diego, 1976.

[22] Swanson, J. , Fairhall, A., and Currie, L. A., "Carbon Isotope

Analysis of Sedimentary Polycyclic Aromatic Hydrocarbons,"

(in preparation)

118
[23] Olsson, I. U. , Ed., Radiocarbon Variations and Absolute

Chronology , Proceedings of the 12th Nobel Symposium held

at the Institute of Physics at Uppsala University, WileyInterscience , New York, 1970; and Damon, P. E. , Lerman, J.

C. , and Long, A. , "Temporal Fluctuations of Atmospheric

C-14: Causal Factors and Implications", Annual Review of

Earth and Planetary Science, 457 (1978).

[24] Cooper, J. A., Currie, L. A., and Klouda, G. A., "Assessment

of Contemporary Carbon Combustion Source Contributions to

Urban Air Particulate Levels Using C-14 Measurements," to

be published in Env. Sci. § Tech., 1981.

[25] Schultz, H. , Currie, L. A., Matson, F. R. , and Miller, W. W.

,

"Pretreatment of Wood and Char Samples," Radiocarbon,

342 (1963).

[26] Watson, J. G. , Edit., Proc. Receptor Modeling Workshop , Quail

Roost, N. C., Feb. 1980.

[27] Gordon, G. E., "Receptor Models," Env. Sci. 6 Tech., 14 , 792 (1980).

[28] Currie, L. A., Countess, R. J. , Klouda, G. A., G. T. V/olff,

and Stroup, D. , "The Contribution of Contemporary Carbon to

the ’Denver Brown Cloud'," (in preparation).

[29] Wolff, G. T. , Countess, R. J. , Groblicki, P. J. , Ferman, M.

A., Cadle, S. H. , and Muhlbaier, J. L., "Visibility-Reducing

Species in the Denver ’Brown CJoud'. Part II. Sources and

Temporal Patterns," GMR-3394, 1980. See also Ref. 5, and

119
Heisler, S. L. , Henry, R. C. , Watson, J. G., and Hidy, G. M.

’’The 1978 Denver Winter Haze Study", Motor Vehicle Manufacturers Association, Detroit, Michigan, 1980.

[30] Kaplan, I. R. , Currie, L. A. and Klouda, G. A., "Isotopic

and Chemical Tracers for Organic Pollutants in the Southern

California Air Basin," (in preparation).

[31] Voorhees, K. J. , Kunen, S. M. , Durfee, S. L. , Currie, L. A.,

and Klouda, G. A. , "The Determination of Source Contribution

of Organic Matter in Atmospheric Particulates by Pyrolysis/

Mass Spectrometry and ^"^C Analysis," to be published in

Analytical Chemistry, 1981.

120
Maunder

Minimum

Suess

Effect I 0) o u

•H o

nd 1—I I rt <U (D -H J-t Jh "d W CU

p! t/) '+-I 0 d d o <D +J 0 cd 4-1 Jh

rt •»-> s 4-^

tfl 4h 0 -P 1 0X0p 0

t3 Jh *P

c3

O 4-1 0 P •• W POO (/) d P (/) 4-( (/) e n:) 0 O rt d 3

Jh o W

4^ ^ tfl 0

(A 0 X d 'd J-i p O 0 d

•H

O ^ p d o d d 0

•H p^r

M > xeG< 0 0 r 0

V) t3 u 0 -H d l-H bc d d 0 0 P r-i •'i-H d d r p 0 U CO p O CO P *H P X 0

pL, • r 0 o S X P r p • 0

t/)

X ^d 'd P P. 0 P o (/) X d

•H o P p .H d d X e >- •H P pd>PoXpdooH

ndd

Pii P

•HPo• HPdPpP0uPoo d p P O 3 X P P d d 2 o

t/) -H P > O -H

•H P

trt

U P d 3O P X d 0 po p (/) o

•r-> P d *H S E • i O -r- LO P

cn •!- >—I E 0P3

bO •H

pH

121

CO2

dilution)

and

the

Bomb

effect

(atmospheric

nuclear

testing) .

See

ence

[23]

for

further

discussion.
Pyrolysis —

Mass

Spectrometry

Data

Figure

2.

Summary

of

Pyrolysis-Mass

Spectra

(Py-MS)

for

Source

Samples

and

Ambient

Atmospheric

Particulate

Sample

Collected

in

Utah

Oil

Shale

Tract

[31].
AMBIENT

4S

Figure

3.

Non-Linear

Map

of

Py-MS

Data

Summarized

in

Figure
Percent

Contemporary

Carbon

(Denver

Aerosol) I 0)

roo>coz o o o O 00 (O o o o ^ CM c

CD>

bO -M 5h

>1 c c o

t/)

O <U rt *4-1 •H M-l I—

C 43

<U <U \ O- !-( 4-> • cd Oi O (U cQ O I +-> O >-i O D c rH -H 13 p, >H >H n3 bo 6 »> 4-! C -H

<U t/5

C -H (+H +J 0) <; M c I-H 4-> t/5 <U Op, .H X U e • «5 4-> nJ D

+J trt

p o'

O *+J P O J-. O O rl- 43 P o 0) 6

>-i

p

p irt o

<DOO P P 4-> ! P, H-! O 4-> »H p o

(D I-H P 43 • P i-l 0 "H o -H ;s o 0 p -H 4-> P 4:: C/D +J P P 4-I H P rH P 0

'-'i-l

O 4:: 4-> r—I t> •' E-* P

rH

O I P o p p Is

p

p o o • ;s o bfi p 4:: p O p p r p p 4:: 0 *H 0 P

<;

pp P 0 0 P > o P a 0 -H Q m0 o 4UP PO P -H

•H PU P P O P

43 «p pp /-> U -P0p p 0 P t3 P P o o Oh^ €0 p p p pO P U P p >

•H 0 P O C/D iH P P I-H • P p p -H O -H wu PJ P P >mH p 0 43 O O .-H >

•H P.T3 P £ 0 P U P P P Pm P0 p p 0

p, o

p. f-> p 01

X > pp

p P • H 0

*—t D

•HP 0 /—\ "xD P P 0 P > P P P U P >H 0 I P Q 0 O I P P P P' e o g O P P O ^ p

pp

bc p
J

I

' •

' * *' .'

.

Cva 1 H;'

.1 r" - Capin -^fy W^ivpn.,1 • .* 5y«t«ni for H^'IC

John J. Bl. anij >jnf,r C w-:: r

I

: ^V'^" s

- - ’ ^ thfc AjjWW*<'’4 h fftfj ..

.' . t1‘n zc Llio

t>t'T 7 :; ie'^ R»^i?>arf ,'0..-y '.'‘s' l4otoin«u<c' i«T“

: ..,

' i.C

.'^V . JHSHfl'Otii cl^oracl

toTu*^-: Cp04wct«d “ oxai^r^ ;- found •:

iv-

“ '‘‘iHttely-

_; TOt^fl.C tC/ he

Very >«g p.'jth

'ength, • eai>1 1

' \ry tube used .

: '*

^or po^-ycy r i i . , ;6b< .: 1 ry of vH*t tec^nlo;.

APPENDIX 2

tx

t

ii»en:,«ne

> . » ••. •'. Ani^il e :« i 1 fV '»f tr,‘^ AR?

ewpared to ' -'.r I cn: nUry ^ 'jU X.iJ

II <7, iy iTtComal iTiUfma! C'JOlJU'W-'^ jJ tost:, ?!

•

/ tjiarfffcti-r .i»y so vi; •.‘•i’

f thus, ^ Tower tn« ^tOstjoti llwits by oon- e: u. • «n to «t-.iyr (')'‘’r

Puionance Gtihdrr;^-J ^'ARS 'whe'-". the - , hA.i,.; ^ lii^s 211 .n 'Iow:

tioctru C.; .j]€ tr<ine: ; 'ori iMr ’- 1 uV^r i •:f -tee

’ ••mi ts -1

. to : 'Vi r*T*c O' •:

. sr COnce»' iv-

Ur^- :; .i i .i . tt'vogul de. cc ".' ;?p r i

r-: slgrv>’.

I dftacuort limits ^

'f. THn_]^i^'t.d snAKi vl- “ v.-IRS t ' uo'^c. , :- ' 1 tnil t‘/^nd ef'fe?* fhe '*dd«=‘u ' tOr Of m

TY'' : i% p\e be 5, is for iti.

k\ t;.o

r ment<» 1 i chr^up^iTJuj!

tesi' ' the cabin ary v/av»^v

wave< jc jsodrff^d to fft In

«vr-! /to, bp ^ita^c^ed ao that t

' :j ^CihevXr-rrrr] t .f

' mant €fih '.-c,, J ,r ’©S8 ^mit/ht ‘".ft aoritfyo4.

’ :

': 1

; de t.ecli o> ara-iysu.

•..«•] in t-g' 1on?c*:<

ic '-vf.

,

1), '. ,,w capi'Ury

ior .Hi d *r> a

• ^.‘ir , of <i eC ‘*

;•

!

'iwo OOpTycytllc Oif|pi^lidkverid1^ i '.’(ryser,'' >#ii'5fPo •..d In toh'<:>'.e'^ were axawi[^ilw^. '^'utiv"..- e/fcH r ifr M-t

were fTLoarod ond in tri>s ....-iliary fo’- These asterfn*, |S|Bf .twined -/-i' :! -i 1 c* .; • rr j^U. ' TTsa der' scrlpUon of, ty;-- HKilWRb^ basi^d on trt beo*'''"*'’'*

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V'C-,'

Evaluation of the CARS - Capillary Waveguide Detection

System for HPLC

John J. Blaha and John C. Schaefer

INTRODUCTION

The work reported here was an attempt to utilize the capillary

waveguide cell for Coherent Anti -Stokes Raman Spectroscopy (CARS) to

determine lower limits of detection for polycyclic aromatic hydrocarbons and to establish the applicability of the technique as a detector for HPLC.

In previous characterizations of organic materials (benzene

and toluene) conducted with CARS, the capillary waveguide sample cell was examined and found to increase the detectability of the CARS

signal by approximately two orders of magnitude compared to the 1 cm path length cuvette normally used (1). The capillary waveguide was found to be most efficient with a very small internal diameter and a very long pathlength. For the tests, a 50 pm diameter by 30 cm long

capillary tube was used to obtain the 100-fold signal enhancement and

thus to lower the detection limits by non-resonant CARS to about 10"‘*M.

Resonance enhanced CARS (wherein the w^ beam approaches an allowed

electric dipole transition) shows a lowering of the limits of detection

to the micromolar concentration level. If the extra enhancement of

the capillary waveguide could be applied to the resonant enhanced CARS

signal, detection limits of approximately 10"^ or less might be achieved.

This would make the CARS technique comparable to fluorescence in detection

limits and offer the added factor of molecular specificity to an analysis.

This was the basis for this work.

EXPERIMENTAL

The experimental set-up is identical to that used in the initial

testing of the capillary waveguide (Figure 1 in Ref. 1). The capillary

waveguide was modified to fit in an adjustable holder and to allow a syringe pump to be attached so that the conditions of a flowing cell

could be examined.

Two polycyclic organic materials (chrysene in benzene and perylene

in toluene) were examined. Solutions of each in their respective solvents

were prepared and then placed in the capillary waveguide for testing.

These materials were also examined with a 1 cm cuvette cell. The description of results will be based on the perylene in toluene system.

125
Studies were conducted with both non-resonant and resonant-enhanced

conditions. To determine the appropriate wavelength for the pump laser,

Xi, in each case, UV - VIS absorption spectra of the solutions were

obtained. These are presented in figures 1 and 2. For the non-resonant

enhanced scans, Xi was selected to be 510 nm. For the perylene solution

Xi was chosen to be 450 nm for resonant enhancement and for chrysene Xi was chosen to be 337 nm.

RESULTS

Pe^lene could easily be observed in toluene at concentrations down to

10 ^ under non-resonant conditions with the capillary waveguide. No

such spectra could be found at this concentration when a cuvette was used as a saniple cell. This demonstrates the enhancement potential of

the capillary waveguide cell.

No spectral features of perylene could be observed for 10"'*M concentrations when resonant conditions were applied. In addition, no toluene

peaks could be discerned either. The 1002 cm~^ toluene band would be

expected to be the strongest band in the spectrum so its absence indicates

the absorption of the signal by the solution. To investigate this possibility

a 10" solution of perylene in toluene was prepared and examined in the_

waveguide. Under non-resonant conditions, the bands at 1002 and 1035 cm"^

in figure d and at 1204 cm~^ in figure 4 of toluene are readily observed.

However, when resonant conditions are applied the features are entirely

obscured indicating that the CARS signal has been absorbed by the sample.

When resonant conditions are used, Xi is at 450 nm and the CARS signal

varies in the region between 425 and 435 nm. In this region the absorption

of the light by perylene is 10 fold greater for the CARS signal than for

this Xi beam. Considering that the enhancement of the capillary waveguide

is produced by multiple passes of the lasers through the sample solution

(up to 130 passes for this cell), the total absorption of the signal by

perylene is so great that no signal reaches the detector. Thus resonant

enhanced CARS is not possible with a capillary waveguide.

We also examined the possibility of using coherent Stokes scattering

to eliminate the absorption problem. Here, fluorescence proved to be too

intense to permit any but the strongest features to be observed (figures

5 and 6 for coherent Stokes and figure 7 for normal Raman scattering; note

in this figure the indication of the reported Raman bands on the intense

fluorescence profile).

To eliminate the fluorescence interference, CARS must be used. To

eliminate the absorption of the signal by the sample and thus obtain

detection limits at the 10"^M level, a single pass cell with a very short

path length is necessary. This has already been tried and found to be an excellent cell by Carreria et al . (2). By using a melting point capillary

126
cell of I.D. 1.6 mm, detection limits for many organic materials have been

reported at 10~® to 10”^M levels. This approach appears to be best suited

for continuing study in the use of CARS as a detection system for HPLC.

REFERENCES

1. J. C. Schaefer and J. Chabay, "Generation of Enhanced Coherent AntiStokes Raman Spectroscopy Signals in Liquid-Filled Waveguides",

Optics Letters 227-229 (1979).

2. L. A. Carreria and L. B. Rogers, "New Liquid Chromatographic Detection

System For Environmental Pollutants," EPA research report EPA-600/4-

80-015, February 1980, 55 pages.

127
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xi

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o

I

M

Figure

1.

UV-Vis

absorption

spectra

of

chrysene

in

benzene
s

Vj~

^ puBio syv3

o

DELTA

CKEGA

(l/cm>

Figure

3.

CARS

spectra

of

perylene

(10

in

toluene.

Ai

constant

=

510.000;

\2

increasing;

Ardol

laser

produces

\\

36

pulses

per

point:

10

pulses

per

second;

A

step

size

=

O.OlOnm
jouSto syv3

Fig.

4.

CARS

spectra

of

peiylene

(10

in

toluene.

X,

constant

510.000;

X2

increasing;

Ardel

laser

produces

Xi36

pulses

per

point:

10

pulses

per

second;

X

2

step

size

=

0.010

nm
5.

Cohci’cnt

Stokes

Scattering

(^CSRS)

of

10 ^

perylene

in

toluene,

constant =

510.000,

increasing:

Ardel

laser

produces

Xi

36

pulses

per

point:

10

pulses

per

second: X2

step

size =

0.010

nm

Crsm o o

CD

UJ s

DELTA

C:
Fig.

6.

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Stokes

Raman

Scattering

(CSRS)

of

lO"^

perylene

in

toluene.

constant

=

510.000,

X«

increasing:

Ardel

laser

produces

X]^

36

pulses

per

point!

10

pulses

per

second:

X2

step

size

=

0.010

nm.

fO

f- iDuSio sas3

* O

DELTA

0:;EGA

(i/cK)
Fig.

7.

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Raman

scattering

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o£

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(10~^)

in

toluene.

(Xq

=

514.5

nm)

Reprinted from OPTICS LETTERS, Vol. 4, page 227, Aususl 1979 Copyright fc) 1979 by the Optical Society of America and reprinted by permission of the copyright owner.

Generation of enhanced coherent anti-Stokes Raman

spectroscopy signals in liquid-filled waveguides

John C. Schaefer and Han Chabay

National Measurement Laboratory, Center for Analytical Chemistry. National Bureau of Standards, Washington. D.C. 20234

Received April 2. 1979 We have demonstrated enhancement of coherent anti-Stokes Raman spectroscopy signals in liquid benzene contained in dielectric waveguide capillaries with angular phase-matching conditions. Enhancement factors as high

as 130 were observed relative to a single crossing. These were measured for capillaries of various cross sections as

a function of length. The maximum enhancement we observed was in a 50-pm X 50-^/m X 292-mm capillary with

a sample volume of 0.75 pil. Signals increased steadily with capillary length and showed the same dependence on pump-beam crossing angle (phase-matching conditions) as in bulk samples.

We report here the use of optical waveguides to en- hance the coherent anti-Stokes Raman spectroscopy

(CARS)^ signal of a liquid sample. Optical waveguides

have been employed previously to enhance spontaneous

Raman spectra^"^ and coherent Raman spectra of gases and solid fibers.®”® Our experiments differ from the

gas-phase experiments in that the nonnegligible fre- quency dispersion of a liquid sample requires that the

two incident pump beams cross at a certain angle, which

depends on the pump frequencies. At this phasematching angle (generally, a few degrees) momentumconservation relationships among the pump and signal

photons are satisfied, and maximum signal is generated.

The use of mode dispersion to allow collinear, phasematdhed three-wave mixing as reported for solid

waveguides by Stolen et al.^ is possible only at a limited

number of wavelengths, making spectroscopy impractical. Angular phase matching is possible for any two

pump wavelengths but does have the disadvantage that

the volume probed is limited to the intersection of the

two focused pump beains. The purpose of these ex- periments was to increase the intensity of CARS spectra

from liquids by increasing the interaction volume while

maintaining angular phase matching.

Waveguide enhancement of CARS signals in liquids was demonstrated by measuring the signal that is due

to the 992-cm“' symmetric stretch mode of benzene for a single crossing in a bulk sample and comparing it with

the signal obtained from benzene in hollow waveguides.

Pyrex and quartz capillaries of various lengths, crosssectional areas, and geometries were tested. A square

Pyrex capillary with dimensions 50 pm X 50 pm X 292

mm (~0.75-pl volume) produced a signal that was

greater than the bulk signal by more than 2 orders of

magnitude.

I'he experimental arrangement was functionally the same as that described previously.' 'The effective /

number for crossing with the IGO-mm crossing lens (Lj)

was//l(), whereas that for each pump beam separately

was/AlO. For hulk samples, the crossing point was lo- cated within a 1-cm path-length cuvette filled with

spcctro-grade henzene. In the waveguide experiments.

the crossing point was located at the entrance aperture

of the capillary.

Two collecting lenses were placed between the cell and the spectrometer. The pump beams and the CARS

signal were recollimated by the first lens, which was

identical to the crossing lens. The focus of this lens

could be placed at the crossing point when a bulk sample was run or at the exit aperture of the capillary w’hen a waveguide was being used. The recollimated beams

were focused onto the 0.5-mm-wide slit of a small double

monochromator (JY DH-10) by the second lens, whose

/ number was chosen to match that of the monochromator if/3.b). The lens was used at f/8. CARS signals were detected by a photomultiplier tube and measured

with a Molectron LP20 photometer. A mirror could be

introduced just upstream of the monochromator, al- lowing the power in the pump beams to be measured by

a photodiode.

The waveguide cell is shown in Fig. 1. It consisted

of a cylindrical Pyrex cell of the appropriate length

having a long narrow waist and reservoirs at each end.

These reservoirs were capped with end windows made

from microscope slide covers. The capillary itself was mounted so that it was supported at its ends by a

slightly larger Pyrex jacket. The jacket was supported

over most of its length by the narrow waist of the cell.

Air

Fig. 1. Capillary cell, showing pump and CAItS heains.
228 OI' I’ICS I.l-'ITKRS / Vol.4. No. 8 / Au^u.st 1979

'Flu' capillary extoiulcd lo within a few millimeters of

t he cell windows. 'I'he cell was mounted on a two-axis

jiimhal mount, placed on .V.V,/ translation staj;cs, al- lowing complete adjustment of position and alijjnment

of the capillary.

'File capillaries used in these experiments were purchased frotn Vitro Dynamics Company. One type was made of Pyrex and had a square cross section. These

were available in lengths up to 300 mm. A second variety was made of quartz with a circular cross section

and was available only in lengths to 100 mm. Inner

dimensions of these capillaries were comparable to the

size of the beam waists at their foci. Capillaries were

tested whose inner dimensions were 50, 65, 75, 100, and

200 f.im. For all the capillaries, the numerical aperture was assumed to be determined by the largest angle for which total internal reflection occurs in benzene. This

angle was calculated to be about 17°, corresponding to

a numerical aperture of 0.30. 'Fhe experiments were done in the following manner. A cuvette was centered at the crossing point, and pump

powers were measured for the pump beams. The

C.\RS signal at 2u.'i — too was optimized by moving only

the two collection lenses. The cuvette was then re- placed with a capillary cell that was aligned with the a'l beam. The collimating lens was moved downstream to refocus the pumj) and signal beams onto the monochromator slit, and minor adjustments of the collection lenses were made to reoptimize the CARS signal. The

crossing angle was set to generate the maximum CARS

signal in the cuvette for a particular coi — CO 2 . Dependence of signal on crossing angle was measured for a 75-/im X 75-/jm X 92-mm capillary and was the same

as for the cuvette. •Measurement of the enhancement was made by direct comparison of the CARS signal from benzene in the

capillary with that from the cuvette with no change in the input beams or detection sensitivity. Only the

signal-collection optics and capillary alignment were

tweaked. The value of each capillary measurement was

divided by the cuvette signal measured immediately

belbre. These results are shown in Fig. 2 for the 50-

/nn-square capillaries and the 65-/im-diameter round

capillaries. Thus the enhancement factor of 130 for the

50-^m-square by 292-mm capillary shown in Fig. 2 is totally independent of the transmitted pump-beam

powers (43Cf of the incident power for the o.'i beam and

2~fc for the cco beam).

Variations in capillary alignment, signal collection

elTiciency, and the degree to which the capillary was

ol)structed by particles could all combine to reduce or

e\'en eliminate the C.ARS signal in a given experiment,

as is evident in Fig. 2. Cuvette signals, on the other

hand, were constant to within 20% and correlated with

\ ariation in pump powers. In spite of the variations in the capillary results, however, the results as a whole

show consistent, signil'icant enhancement and definite

trends with re.spect to dimensions. As a function of

length, enhancement increased steadily up to 300 mm.

.Spectra can he generated in the waveguide in spite of

the variations in signal since i)ump wavelengths can l)e changed without adjustment of capillary alignment or

collection optics. Sju'ctroscopic results will be described in a future article. 'Fhe spatial distribution ol' pump and CARS signals

Fig. 2. Waveguide enhancement compared to a single

crossing in a cuvette as a function of capillary length for 50- pm-square Pyrex capillaries and 65-^m-diameter round

quartz capillaries.

from the capillary was determined by photographing

the output pattern. The two pump beams formed

separate images, showing maxima and apparent nodes

that were reproducible from one photograph to another.

The oji pump beam was aligned with the capillary axis

and formed a central spot. The output pattern of a round capillary is shown schematically in Fig. 1. For

a square capillary, the 0:0 beam formed two vertical

bands about the central cci maximum. Each band at

cco had vertical and horizontal nodes. FTom the dis-. tance between coo maxima and the center of the pattern,

it is estimated that the light at CO 2 emerges from the

capillary at an angle of ~1.8° relative to the coi axis. This is consistent with the entrance crossing angle (2°

in air) within the accuracy of the measurement.

The CARS signal w'as also photographed with a nar- row-band interference filter used at the CARS fre- quency. When both pump beams were present, three

maxima occurred, a central spot with a vertical band on

either side. The patterns observed when the pump

beams were present individually indicated that the

central spot was due to stimulated emission at coi -I- 992

cm“' (the anti-Stokes frequency) and the bands on ei- ther side were CARS signal. It is significant that phase

matching by angular displacement was maintained

throughout the length of the capillary. Spatial filtering can be used to improve the signal-to-noise ratio just as

in the bulk measurement.

For convenience, all the results were measured using

pump beams attenuated by approximately 1 order of

magnitude below the powers that could normally be

used with a sample contained in a cuvette. At pump

powers 1.3 orders of magnitude higher than those used,

bubble formation within the capillaries interfered with

production and measurement of CAR.S signals.

Enhancement showed an overall inverse dependence

on capillary cross-sectional area. To model this dependence, we employed the expression given by DeWitt

el alp for anti-.Stokcs power in the plane-wave limit.

4 7T-a;,vs“ criAS

., [R(c0i)]-^[R(co2)] .9

A‘^ 136
August 1979 / Vol. 4. No. 8 / OPTICS LinTPRS 229

where L i.s the length and A the cross-.sectional area of

the interaction region. We normalized the results for various-diameter capillaries to remove the dependence

of signal on pump power and cross-sectional area. One

would expect this normalization to yield identical dependences of normalized CARS output power on length

for all the capillaries. Results indicated that this simple

picture is not adequate to describe the data accurately.

The dependence of CARS power on length for a single

crossing can be inferred from a comparison of the confocal beam parameter, b, the interaction length, L, and

the waveguide radius, a." For our experiments the

plane-wave approximation is appropriate, and CARS

power will increase as the square of the interaction

length. This square dependence will also apply to the

50-/rm capillary since the capillary’s inner dimension

is close to the opt imum waveguide radius for beams with

6 s 10 mm. Our data do not allow a clear distinction

to be made between quadratic and linear dependence

on length, although the 50-/rm capillary appeared to indicate quadratic dependence.

The number of phase-matched crossings per unit

length was found to depend critically on the alignment

of the pump beams with respect to the capillary axis. The maximum number of phase-matched crossings occurs when one beam is aligned with the capillary axis

and the other beam intersects this axis at the crossing

angle. When both beams are tilted in the same direction with respect to the capillary axis, more crossings

occur, but there are fewer crossings at the correct phase-matching angle. The number of phase-matched

crossings for a symmetrical alignment is one half of the

maximum value. The enhancement measured for the

symmetric case was indeed significantly less than that

for the optimum alignment used to obtain all the re- ported data.

• We have demonstrated a capillary cell that enhances

the CARS signal by more than 2 orders of magnitude

with a liquid sample volume of ~0.75 ;/l. A cell can be

designed in which the sample could be made to flow

through the capillary. Such a cell could be connected

directly to a liquid chromatograph to provide continuous, nondestructive chemical analysis of the output of

the chromatograph.'*^ Mixing of contiguous eluent

fractions would be minimized in a longitudinal capillary

cell, and signal is increased by 2 orders of magnitude

with the same pump powers. Effective sample volumes

in a longitudinal waveguide cell and a transverse melting

point capillary are approximately equal. The waveguide cell may also prove valuable in studies of vibrational and electronic excited states produced in the

capillary and probed by CARS.

The waveguide properties of the capillary require that

the index of refraction of the sample be greater than

that of the waveguide material. If silica capillaries must

be used, this is a serious limitation since it precludes the

study of aqueous solutions. The dec’elopment of a low-index capillary or the use of metal or metal-coated

capillaries could remove this restriction and allow al- most any sample to be used.

We are grateful to Instruments S.A. for the loan of the

double monochromator and scan control used in these

experiments. We would like to thank Hank DeLeonibus for expert assistance in constructing cells and

Gregory Rosasco for valuable discussions.

References

1. I. Chabay, G. K. Klauminzer, and B. S. Hudson, Appl.

Phys. Lett. 28, 27-29 (1976).

2. R. H. Stolen, E. P. Ippen, and A. R. Tvnes, Appl. Phys.

Lett. 20,62-64 (1972).

3. G. E. Walrafen and J. Stone, Appl. Spectrosc. 29, 337-

344 (1975).

4. P. Rabinowitz, A. Kaldor, R. Brickman, and W. Schmidt,

Appl. Opt. 15, 200.5-2006 (1976).

5. G. E. Walrafen and J. Stone, Appl. Spectrosc. 26, 58.5-589

(1972).

6. R. H. Stolen, J. E. Bjorkholm, and A. Ashkin, Appl. Phvs.

Lett. 24, 308-310 (1974).

7. R. B. Miles, G. Laufer, and G. C. Bjorklund, Appl. Phvs.

Lett. 30,417-419 (1977).

8. J. Stone, J. Chem. Phys. 69, 4349-4356 (1978).

9. R. N. DeWitt, A. B. Harvey, and W. M. Tolies, Naval

Research Laboratory Memorandum Report 3260 (1976),

p. 21.

10.

L. B. Rogers, J. D. Stuart, L. P. Goss, T. B. Malloy, -Jr., and

L. A. Carreira, Anal. Chem. 49, 9.59-962 (1977).

137
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APPENDIX 3

[Reprinted from the Journal of Physical Chemistry, 84, 1611 (1980).] Copyright © 1980 by the American Chemical Society and reprinted by permission of the copyright owner.

Low Reynolds Number Fluid Flow Induced by Settling Aerosol and Detected by the

Particle Doppler Shift Spectrometer

Robert A. Fletcher, David S. Bright, and Ilan Chabay

138

Published in Journal of Physical Chemistry, June 12, 1980, pp. 1611-1614, by the American Chemical Society

Low Reynolds Number Fluid Flow Induced by Settling Aerosol and Detected by the

Particle Doppler Shift Spectrometer

Robert A. Fletcher,* David S. Bright, and Ilan Chabay

Gas and Particulate Science Division, Center for Analytical Chemistry, National Bureau of Standards, Washington D.C. 20234

(Received September 28, 1979)

Publication costs assisted by the National Bureau of Standards

Air flow generated by gravitationally settling S-lS-ftm diameter droplets has been observed. The magnitude

of the flow phenomenon is derived from measurements of the particle settling velocities by using the particle

Doppler shift spectrometer (PDSS). The PDSS can determine particle velocity and size with high accuracy due to the inherent internal calibration characteristic of the instrument. The magnitude of the fluid flow velocity

is dependent on the particle number concentration. Experimental evidence verifying the flow pattern is presented.

Introduction

Each settling particle in a cloud drags some of the air medium with it which effectively increases the settling

velocity of neighboring particles. The net effect is to in- crease the apparent settling velocity of a cloud of particles. In a closed system, such as our PDSS optical scattering

chamber, the downward flow of the medium, which results from the settling particles, must be compensated by an

equal, but oppositely directed flow. If only part of the

chamber is filled with settling particles, an air circulation pattern will be set up as shown in Figure la. This occurs because the return flow will be along the path of least resistance which is the path void of particles. If particles

homogeneously fill the tube as in Figure lb, there will be no apparent settling velocity increase due to interaction

of the return flow with the aerosol. This description

follows that of Happel and Brenner.^

An alternative way to describe this particle-induced fluid motion is to examine the net flow in a small sample volume

element. For case lb, the net flow will be zero for a small

volume element taken anywhere in the chamber. While

for case la, if a volume element is taken in the particle

stream, a net downward flow will be observed. Likewise,

outside the particle column, there will be a upward flow. In both cases, the net flow through any cross-sectional slice of the tube is zero. We present the first experimental measure of settlingaerosol-induced fluid flow in the low Reynolds number

regime. The fluid velocity measurements are made by

measuring the settling velocity of clouds of 5-15-Atm di- ameter dioctyl phthalate (DOP) particles which are gravitationally settling in a smedl closed vessel filled with air. The particle Doppler shift spectrometer (PDSS) is used

to detect and measure the particle-induced fluid motion.

The fluid motion is observed as a small velocity increment

to the particle settling velocity which is calculated from

Stokes law. Measurements of such small velocities are primarily due to the internal calibration capability of the

PDSS.

The PDSS measures particle settling velocity directly.

From the gravitational settling velocity, the aerodynamic

size can be determined. The PDSS is capable of deter- mining particle diameter to an accuracy of 0.05 )im (Bright

et al.)^ as a result of an internal calibrating procedure based on the fact that the light scattering intensity is a rapidly

varying function of particle diameter over the size range

of 5-15 fim. The Experimental Section contains a description of the

PDSS and experimental conditions. In the Results section,

the data reduction technique and experimental results are presented. The Discussion section summarizes the work

and offers possible applications of the results. Experimental Section

A schematic of the experiment is shown in Figure 2. Pure DOP aerosol is generated by a medicinal atomizer

modified to generate large (5-15-Mm diameter) aerosol. The atomizer is driven by a positive pressure air stream

that is precisely flow controlled. Dilution air flowing past

the atomizer entrains the aerosol streeun and determines

the final particle concentration. The aerosol is then passed

through a charge neutralizer and then is sampled in a 1.3

139
1612 The Journal of Physical Chemistry, Vol. 84, No. 12, 1980 A B

fr0 ° o ^

C

° ^ o

° o c

o o’

f

° o oo /1

ftO o ® ^ o

0 O

. OO o /J

° 1 ° o ° O

O 0

° o

0 ° p o o

°

° ° 1

°

o

' o ' o

1 O 1 O O o

° °ot°

o 0 .S'

Figure 1. Description by Happei and Brenner of the particle-induced

air flow pattern. Case a segregates the return flow to the outside region

of the cythder (region void of particles) while case b integrates the return flow into the cloud.

Figure 2. Schematic view of the experimental arrangement.

m long by 0.022 m diameter drift tube. The drift tube is jacketed by a larger diameter tube to allow stable air density layering to occur for the 1-2 °C/m vertical thermal

gradient in the laboratory. The drift tube is valved to

isolate the aerosol sample from the laboratory environ- ment. The optical scattering chamber is located below the

drift tube. The aerosol clouds used in these experiments contain

5-15-Mm diameter DOP particles in number concentrations

of 100-1000/cm^. The aerosol cloud settles through an air medium which is at 25 °C and 1 atm (10^ kPa) pressure. The Reynolds number for flow past particles of this size range is on the order of lO’^-lO"^. The particles are allowed

to freely settle under only gravitational influence and the

opposing Stokes drag force. The PDSS has been described in full.^’’* Briefly, a

horizontal laser beam is directed through the settling

particle stream. As the particles pass through the beam,

they scatter light most strongly in the forwa d direction. By virtue of the particle motion, the scattered light fre- quency is Doppler shifted. This frequency shift can be

detected by mixing the frequency shifted radiation with

unshifted scattered radiation from a stationary source (the

chamber window) onto the photomultiplier tube. The

frequency shift is related to the particle velocity. The

photomultiplier tube output is filtered, amplified, fast Fourier transformed, and displayed as relative scattered

light intensity vs. frequency, from which the Doppler

frequency shift may be determined.

The PDSS can be used to size single particles or de- termine the size of individual particles in an aerosol cloud. For a wide size distribution (5-15 ^m diameter) of spherical

particles the summation of the spectra generates a pre- dictable pattern. The summation spectrum contains local

Fletcher, Bright, and Chabay

3 6 9 12 15 18 DIAMETER M

Figure 3. Relative light scattering intensity as a function of Doppler

shift frequency compared to theoretical scattering curve. The solid

line is the data for DOP aerosol. The dashed line is the exact theoretical calculation. The positions of the data extrema are shifted to the right as a result of the air flow. The shift is measured in terms of the frequency change, Af, which is subsequently converted to settling velocity.

maxima and minima “features” which reflect the resonant

scattering properties of spheres as described by the Mie

scattering theory (see Figure 3). Approximately 20 of the

features product are used in the data reduction technique

discussed later. The laser probes the aerosol cloud in the optical scat- tering cell, which is located directly below the drift tube

as shown in Figure 2. The cell is a straight glass cylinder

of 9-mm i.d. with microscope slide windows attached for

optical purposes. A disk conteining a 2-8-mm orifice which

serves as an aperture for the particle stream is located

above the scattering chamber (Figure 2). Verification of

the return, upward directed fluid flow requires a disk of

special design. One half of the cell’s cross sectional area

is open to admit particles, the other side is closed with the

exception of a small particle admitting orifice. This design

allows us to examine the influence of a large particle stream upon a much smaller one. The bottom of the scattering

cell is sealed with a microscope slide which is removeable.

Particles collected on this slide can be counted with a microscope to determine the sample number concentration. The seals above and below the scattering window region

are made with vacuum o-ring glass joints to ensure isolation of the seunple and yet give flexibility in chamber orienta- tion and aperture (disk) alignment.

Results

The experiments demonstrate that the circulation pattern illustrated in Figure la is present and that the induced

fluid flow velocity depends on particle concentration. The

fluid velocity is the difference between the experimentally

measured particle settling velocity, v, and the corre- sponding settling velocity, Ug, calculated from Stokes law. Stokes law is applicable for a single particle settling in a

still fluid. The velocity shift is experimentally observed as a shift of the entire experimental curve to the right of the cal- culated curve. The frequency difference. A/, is obtained

by subtracting the center position of each experimental

extrema from its corresponding calculated position.^ The

frequency difference is converted to velocity difference,

V - Vg, by

V - Ug = A/X/sin 6

where X is the wavelength of the laser line in air, v is the

140
Low Reynolds Number Fluid Flow

Figure 4. Velocity shift as a function of particle diameter for four sets

of data. The upper curves show a positive velocity shift for the aerosol column. When the same scattering chamber is used without the orifice

in place (two lower curves), there is no shift. The orifice geometries

are indicated on the left of their respective data curves.

Figure 5. Velocity shift vs. particle diameter for three particle number

concentrations. This plot show the dependence of air flow velocity on the particle number concentration.

Figure 6. Velocity shift plotted as a function of aerosol particle concentration. Each point is an average of the velocity shift found for the

first 15 Mie extrema. experimentally observed velocity, is the calculated

settling velocity via Stokes law, and d is the angle between

the incident laser beam and the detector (typically 5-7°).

The results are plotted in Figures 4-8 as velocity shift

The Journal of Physical Chemistry, Vol. 84, No. 12, 1980 1613

0.02

CD

I LU

O

o

e

0

e

0.00 1 . . , 0.5 1.0 ORIFICE DIAMETER/CHAMBER DIAMETER

Figure 7. The fluid velocity dependence on the particle admitting orifice size. The orifice is located above the scattering cell.

DIAMETER

Figure 8. Demonstration of return fluid flow. The various particle void geometries and the resultant velocity shifts of the particles are illustrated

in parts a-d. A positive velocity sWt is observed in cases a and c where

a return flow path is present. A negative velocity shift is observed for the small column of particles because it is located in the return path

of the fluid flow induced by the large column of settling particles. This

velocity shift demonstrates the existence of the return flow. When the

return flow is integrated in the volume of the particle column (d) no

velocity shift is observed.

(fluid velocity, v - vj vs. extrema position where the ex- trema position have been converted to particle diameter

by using Stokes law. The demonstration of the particle-induced fluid flow is illustrated in Figure 4. The upper two curves show the

condition illustrated hy Figure la, where the column of

aerosol produces a downward air flow in the aerosol column

and an upward air flow outside the aerosol column, i.e., in the region void of particles. The result show pronounced

positive velocity shifts. The bottom two curves are for the

case when the entire cross section of the chamber is filled with particles, illustrated in Figure lb, and show that in this case there is no velocity shift indicating there is no

141
1614 The Journal of Physical Chemistry, Vol. 84, No. 12, 1960

net microscopic flow. The duplicate data sets show the

reproducibility of the experiment.

The particle-induced fluid flow circulation increases with

increase in particle concentration. The velocity shifts for three particle concentrations are shown in Figure 5. A

summary of velocity shift as a function of particle concentration is presented in Figure 6 where each single shift point is an unweighted average of the velocity shift for the

first 15 feature positions at a given particle concentration.

A 4-mm diameter collimating orifice is used throughout

and the particle concentrations are determined by microscopy. An order of magnitude calculation is in good agreement

with the experimental results. When applying the Navier-Stokes equation in the creep flow regime, the acceler- ation and inertial terms may be neglected.® Balemcing the

viscous diffusion force against the Stokes particle driving

force, F, and replacing d/dr by 1/R, we can estimate the

vertical fluid (air) velocity, u^, by

i^almax ~ riFR^/v

Here, n is the particle number concentration, rj is the fluid viscosity, and R is the radial dimension of the particle

column. If we assume an average particle size of S-^m

diameter which has a settling velocity of 0.19 cm/s, a

particle number concentration of 1000/cm®, and R ~ 0.1 cm, then Uj|max is on the order of 0.01 cm/s. The exper- imental results in Figure 6 confirm both the linear de- pendence on particle number concentration and the general magnitude of the result to within a factor of 2. The velocity shift as a function of the orifice size (Figure

2) normalized by the chamber size is shown in Figure 7. Below 4 mm, an increase in orifice size causes an increase

in the velocity shift. This is reasonable because more

particles are put into the system to drive the fluid. As the

orifice diameter is increased above 4 mm, the boundary

of the particle column and the vessel restrict the return flow resulting in the observed gradual decrease in the

velocity shift. The existence of return flow in the particle-void regions,

i.e., outside of a collimated particle stream (Figure la) is demonstrated in the following experiment. The fluid velocities are very small, on the order of 0.001-0.01 cm/s, and

thus difficult to measure by ordinary means. It is possible,

however, to observe the return fluid flow resulting from

a column of settling particles by measuring its effect on

the velocity of a small column of particles settling in the

return fluid flow. The smaller column is used as a probe

to sense the fluid flow generated by the larger particle

column.

The existence of the return flow is demonstrated by

comparing the particle velocities for four geometries as presented in Figure 8a-d. The settling velocity of the

particles in the small particle column (Figure 8a) shows

a positive shift, as expected for particles settling in a closed system where the return upward fluid flow can occur

outside the particle stream. The introduction of the large

Fletcher, Bright, and Chabay

particle column (Figure 8b) produces a negative velocity

shift in the small particle column. This apparent velocity

reduction is due to the interaction of the downward velocity field of the small particle column and the upweird

return flow induced by the large particle column. Measurement of the large particle column velocity reveals the

expected positive velocity shift (Figure 8c) for the same

reason as in Figure 8a. When the collimators are removed, we see no shift (Figure 8d).

Conclusions

This work presents two main results: one, the experimental observation and quantification of particle-induced

steady-state fluid flow phenomenon and, two, demonstrations of the unique capacity of the particle Doppler

shift spectrometer to measure small velocities when used

in a manner such that the internal size calibration capability can be utilized. To our knowledge, this is the first experimental measurement of particle-induced fluid flow from cloud droplet

size aerosol (5-15 fim) gravitationally settling in air. The

results of these experiments may be useful for particle

cloud modeling. The role of particle-induced fluid flow

in a cloud will for the most part be secondary to thermal

convective forces,® however, the particle-induced circula- tion velocities are particle number concentration dependent and thus may become significant at high number

concentrations. This work also suggests that a few percent

error can result in particle size determinations when using

only Stokes law for particle clouds settling in closed containers that have regions void of particles. The ability to measure air flow velocity-particle concentration dependence provides a means of determining the quality of a

specific PDSS scattering chamber. The absence of particle

concentration dependence implies that a chamber is sat- isfactory and thus will allow us, by knowing that the

calibration is correct, to use solely the aerodynamic

properties of the particles to a much higher degree of

accuracy. Conversely, in a chamber where circulation

occurs, we can estimate particle number concentrations

by measuring the velocity shift. This work also shows the capability of the particle

Dopple shift spectrometer to make extremely small velocity measurements in real time. Some of the velocities reported are on the order of 10 tim/s. We will apply these techniques and the unique sensitivity and accuracy of the

PDSS to further studies of fluid behavior in the low

Reynolds number, low velocity regime.

References and Notes

(1) J. Happel and H. Brenner, "Low Reynolds Number Hydrodynamics",

Prentice-Hall, Englewood Cliffs, N.J., 1965, p 371.

(2) D. S. Bright, R. A. Fletcher, and I. Chabay, J. Phys. Chem., this

(3) I. Chabay and D. S. Bright, J. Colloid Interface Sci., 63, 304 (1977).

(4) J. P. Gdlub, I. Chabay, and W. H. Flygare, Appl. Opt., 12, 2838 (1973).

(5) J. Happel and H. Brenner, ref 1, p 41.

(6) N. H. Fletcher, "The Physics of Rainclouds", University Press, New

York, 1969.

142
J. Phys. Chem. 1W0. 84, 1607-1611 1607

Particle Doppler Shift Spectrometry. Accurate Size Determinations of 5-15-/im Aerosol

David S. Bright,* Robert A. Fletcher, and Ilan Chabay

Gas and Particle Science Division, Center for Analytical Chemistry, National Bureau of Standards, Washington, D.C. 20234

(Received September 28, 1979)

Publication costs assisted by the National Bureau of Standards

We have improved the particle Doppler shift spectrometer (PDSS) to determine the diameter of 5-15-Mm droplets

to high accuracy (±0.05 pm). The diameter is calculated from Stokes law and the gravitational settling velocity

which is obtained by measuring the Doppler shift of laser light scattered at a single angle. This scattered light also shows intensity variations with diameter as predicted by Lorenz-Mie light scattering theory. Characteristic features of the plot of scattered light intensity vs. droplet diameter are used £is size calibration markers. The

features are a function of only the index of refraction of the aerosol material and the wavelength of the light.

Our results show better agreement with Stokes law without the slip correction than with the correction.

Introduction

Particle size measurement has many important applications. For example, particle size measurements will

likely be involved in the monitoring of industrial crushing

or grinding processes and quality control of paints, ce- ments, or other powders is likely to involve particle size measurement.^"^ The implementation of industrial hygiene

standards and the study of air pollution^ also involve

particle size measurements. Most particle sizing and size measurement instruments cannot be calibrated from first principles and require calibration by a laboratory generated

aerosol. For example, the widely used optical particle

counters^^ which measure particle size as a function of the

light intensity scattered off single particles must be cali- brated by using some type of aerosol standard. Most

aerosol generators in turn require size measurement of the

aerosol by an accurate method® in order to be useful as a

calibrating standard.

The particle Doppler shift spectrometer (PDSS) has

been already applied in the calibration of an optical particle counter® by determining the diameter of the monodisperse calibrating aerosols. In this paper we will establish the accuracy of the PDSS technique and demonstrate its utility.

Golub, Chabay, and Flygare^® first used a laser Doppler

shift technique to measure droplet growth. A variation

of the more commonly used dual-beam laser Doppler

velocimetry technique, this single beam heterodyne tech- nique involved beating Doppler shifted laser light scattered from particles against reference laser light scattered from

the chamber window, which is the heterodyne source. This

technique measured many droplets in the laser beam at once, since the individual signal packets of each droplet

could be separated with respect to the heterodyne fre- quencies. The frequency information gave the settling

velocities and thus the droplet diameters. The same authors suggested using the Mie intensity features in the data

as sized calibration markers, and they qualitatively employed one such marker. “

Using this same technique with the PDSS, Bright and

Chabay^^ then reported using five to ten Mie size markers.

Here we report the following developments: (a) improved

precision of the PDSS; (b) a quantative measurement of

improved accuracy by using up to 20 Mie features as size markers; (c) the experimental conditions necessary to obtain this accuracy, and; (d) an experimental verification

of Stokes law without the slip correction factor.'®

Experimental Section

The PDSS is shown schematically in Figure 1, where a horizontal laser beam, polarized horizontally, passes

through a verticeil tube (A) in which the p^ticles settle under gravity. The optics now include a 20-cm focal length

lens with a 10-/ttm pinhole at the focal point. This allows

observation of the particles for the full 2-mm height of the

beam while limiting the observation angle to within 3 mdeg

of 6, i.e., 6 ± 0.003°. Any averaging of light scattering over

this angle range is negligible; light scattering and Doppler

calculations are performed for precisely 6°. The optics are mounted on a tiltable table which can be lowered to d =

0° for alignment. Alignment of the pinhole is the most

critical step. The tilt of the table, which has been checked

with gauge blocks and a sine-bar, is within less than 0.01° of 6°. A 0.01° error is compared with other sources of error

in Figure 5. The maximum effect expected from the observation angle error is small. Light is scattered into the detector (see Figure 1) both

from the particles and from the windows on tube A. The

light from the windows is the heterodyne source. The

heterodyne frequency"^'^ for a particle is F = V'K or, since

|Xs| |/Co| = 27t/\ and K = Kq - then

F = ^ sin 6 (1) A where K is the scattering vector, Kq and are the initial and scattered momentum vectors, 6 is the scattering angle, X the wavelength of the laser line in air through which the

particle falls, 514.5 nm, and V = |V| is the velocity of the

particle.

A single particle falling through the beam with Stokes

velocity V produces a photomultiplier current signal having

modulation frequency F and amplitude envelope proportional to the product of the intensity of the light scattered by the particle and the time the packet is observed. The

resolution of the PDSS is shown by the representative

single-particle peaks in Figure 2. The limits of resolution are a function of the following parameters:

(a) Resolution of the 400-channel FFT (fast Fourier

transform) spectrum analyzer. This is 5 Hz for the

2000-Hz range.

(b) Broadening due to Brownian motion. The full width

at half-maximum is 2D\Kf/2w,^^-^* where D is the diffusion

coefficient of the particle.'® '® This width is less than 3 Hz

for 5-pm diameter DOP (dioctyl phthalate) spheres, and

is even less for larger spheres.

Published in Journal of Physical Chemistry, June 12, 1980, pp. 1607-1611, by the American Chemical Society

ik

143
1608 The Journal of Physical Chemistry, Vol. 84, No. 12, 1980

Figure 1. Schematic of apparatus. Aerosol is passed through tube B (1 m X 22 mm). Valves are closed, sealing the tube A-tube B system. Data are collected for 5 min with the FFT spectrum analyzer as the

particles settle into tube A (20 cm X 9 mm) and through the beam.

Microscope slide sections are inserted into the walls of tube A for windows for the laser light. The lens-pinhole-PMT (photomultiplier tube) system rests on a tiltable platform inclined at the scattering angle 6

(6°) and collects light scattered at angle d from the full length of the beam intersecting tube A. The loudspeaker is routinely used to monitor experimental conditions.

Figure 2. Example of resolution of PDSS. Frequency spectrum of a

0.2-s time window, during which four particles were falling through the beam. Data reported in this paper are 5 min of such spectra, averaged

in the frequency domain. The full width at half-maximum of peak 2

is 10 Hz, corresponding to 0.005 cm/s or, from Stokes law, 0.06 /urn.

(c) Truncation error. The error associated with a FFT

frequency measurement is inversely proportional to the

time of the measurement. The minimum amount of time

the fastest particles (18 /zm, V = 1 cm/s) are in the beam

is about 0.2 s, which is also the sampling window of the

FFT. This resolution is then limited by the 5-Hz channel

widths of the FFT analyzer.

For shorter portions of wave packets, the corresponding

peaks on the frequency spectrum are broader than 5 Hz

and are of low amplitude. These low amplitudes result from the short duration of the packets or because the

particles are in the edge of the beam. These broad peaks

contribute a small amount to the background noise. The Doppler frequencies are audibly distinguishable

especially at the beginning of a nm when only a few larger

particles are in the beam. Small leaks, streaming of the

air near the beam, or excessively dirty windows can be

detected conveniently and quickly after some practice by

listening to these Doppler signals. This serves as a diagnostic which allows us to avoid making a complete run only

to find the Mie structure (Figure 3) buried in noise and

artifacts. Of all the geometries tried for scattering chambers, the

best is a tube with windows made of pieces of microscope

slides set into the walls. Thermal shielding is not necessary, especieilly since a stabilizing thermal gradient of about

1 °C/m fortuitously exists in the room. However, thermal

convection cells do spontaneously occur Tor chambers with

Bright, Fletcher, and Chabay

Figure 3. Mie features in the light scattering calculations. The inset shows Lorentz-Mie light scattering calculations plotted vs. diameter

for DOP at 25 °C (index of refraction = 1.48970, \ = 514.5 nm, d = 6 °). In the main figure, for direct comparison with the data, the

light scattering calculations are plotted vs. the Doppler frequency F

(calculated from the diameter, Stokes law, and the density, p = 0.9797

at 25 °C). The intensity is scaled by MF. Two corresponding features are labeled as A and B.

any horizontal dimension greater than that of the 9 or 10

mm diameter tube (tube A, Figure 1). Another subtle

factor is important in the design of the chamber. If there

are regions void of particles near the scattering region, air flow will be induced in the scattering region by the motion

of the falling particles. This streaming invalidates diameter measurements by Stokes law because it results in a

settling velocity greater than the aerosol gravitational

settling velocity. This is easily detected on the PDSS.^®

To avoid this phenomenon, the chamber must be filled homogeneously with the falling aerosol, which is achieved

by the relatively simple design of tube A. The windows

are set into the wall to match the inner diameter as closely as possible, protruding slightly into the aerosol stream

rather than leaving small gaps that would not be filled with

the falling aerosol. The tubes are set as closely as possible to vertical. We have chosen dioctyl phthalate (DOP) aerosol for our experiments because it has the following characteristics:

(a) It has a low vapor pressure; the particles do not change

size significantly during the measurement time of less than

1 (b) It is optically nonabsorbing at 514.5 nm. (c) Its physical characteristics have been accurately measured

here at the National Bureau of Standards. At 25 °C and

514.5 nm, the index of refiraction is 1.48970 and the density

is 0.9797 g/m®.

The DOP aerosol is generated by using a glass medicinal

atomizer modified by removing the curved tube where the

larger droplets normally impact and run back to the liquid

reservoir. This modification extends the upper size limit of the generated aerosol. The air supply to the atomizer

is carefully regulated and filtered. The aerosol, after di- lution with filtered air, is transported through tube B (see Figure 1). For a measurement, valves at both ends of tube

B are closed, trapping some aerosol in the tube, and the

aerosol in the sample then to settles through tube A. The

20-cm settling space in tube A above the scattering region

allows only those particles greater than 4 pro. to reach the

laser beam during a 5-min run. The maximum concentration of particles during any part of a run is several hundred per cm®. If the large number of very small particles generated by the atomizer drifted into the scattering

region, the light scattered from these particles would mask

the heterodyne signal from the beam spots on the windows

which serve as the heterodyne sources. This homodyning

would obliterate the Mie structure in the data. 144
Particle Doppler Shift Spectrometry The Journal of Physical Chemistry, Vol. 84, No. 12, 1980 1609

Figure 4. Velocity shift measurement example. The calculated photocurrent vs. diameter curve of Figure 3 (dotted) is superimposed on

data (solid) to illustrate how the differences in the feature positions (abscissa only) are measured. The inset shows this peak, with a shift of -0.003 cm/s is one such feature. The vertical lines mark the centers

of the parabolas fitted to a selected region of points of the data and

the calculations. The segment of points fitted with a parabola is shown

only for the data. The shift of -0.003 cm/s corresponds to a diameter measurement error of -0.04

Figure 5. Error analysis. These five calculated curves show shifts of feature positions from positions of the correctly calculated curve, for the following reasons: A. Temperature shift of 2.5 °C. (Experimental

temperature changes were less than 0.5 °C.) B. Additional light scattered through 174° = 180° - 6° due to 9% of the beam returning back through the aerosol from each surface the second window. C. Aerosol density change of -FO.57% and index of refraction change

of -0.1 %. This mimics a run with near zero shifts. Changes of index and density by the right ratio to exactly offset each other are improbable. For example, they do not occur with temperature changes, as seen

from curve A. D. Scattering angle change, 0 = 6.01°. E. Index of

refraction change of 0. 1 % only.

Theory

Setting Velocity. In still air, spheres with diameter d

settle with terminal or Stokes velocity

=

Pgd^

I8v

( 2)

where g = 0.9802 m/s^ is the acceleration of gravity, p is the density of the sphere minus the density of air, and ?? = 1.832 X 10^ Pa*s (1.832 X 10“* P) is the viscosity of air at 1.01 X 10^ Pa (760 mmHg) and 25 °C. For larger particles, a Reynold’s number correction becomes necessary. For example, the velocity corrections^ for 30-pm particles of unit density is 0.7%. Extrapolation of Davies’S® empirical formula to diameters less than 30 pm shows the

correction for the size range discussed here to be less than

0.09% and to be proportional to d^. For particles below

the 5-15-mm size range a slip correction is used.s^ The

slip correction in air for particles larger than 2 pm is of the form V = SV^ where

S = 1 +

1.257/

0.5d

(3)

and where I is the mean free path of air molecules, 6.53 X 10“® cm, at atmospheric pressure. Extrapolation of this empirical formula beyond the particle sized originally

measured,^® of about 2 pm, then shows that the velocity

correction from the slip factor increases linearly with di- ameter:

pg(1.257)2/

V-V,® = SV,-V, ® = d

® 18t7

In the 5-15-pm size range, the velocity correction is re- spectively 3-1% of the overall settling velocity. The PDSS

technique has sufficient accuracy to test for this correction, as will be shown.

Mie Features and Calibration. Lorentz-Mie light

scattering calculations^^’^^ show the relative scattered light

intensity at a fixed angle to oscillate rapidly with increasing

diameter for transparent or weakly absorbing spheres

(Figure 3, inset). Features such as peaks or valleys occur

at specific diameters.^^ To make Lorentz-Mie scattering

Figure 6. Sensitivity of the velocity shift measurements to the measurement procedure. Three separate determinations of shift were

performed on one data curve from one measurement (solid lines) and on one curve from Mie calculations (dotted lines). The measurement

procedure involves choosing initial feature positions by hand and gives a small degree of variability. Feature positions of the data are not measured above 15 pm because there are too few particles to define the features there.

calculations, one must know the wavelength of the incident

light and the index of refraction of the particles. DOP

particles meet these requirements: DOP is a clear liquid

and the index and density of the bulk material are well

characterized. After the light scattering calculations are

suitably scaled (Figure 3), they resemble PDSS data for a reasonably flat distribution of particles as seen in Figure

4. The comparison of data with the scaled theoretical

calculations corresponds to the comparison of the measured Doppler settling velocities (solid vertical line. Figure

4, inset) with the theoretically calculated velocities from

the feature diameters using Stokes law (dotted vertical line. Figure 4, inset). The measured velocity minus the calcu- lated velocity, i.e., the velocity shift, is determined as il- lustrated in Figure 4 and is measured at a number of

diameters throughout the size range as shown in Figures

5-8. In practice, an initial feature position is marked on

a plot of the data, and then digitized to locate the center

of the segment data points used for the parabola fit. This

fit (Figure 4) then determines the feature position more

accurately. For both theoretical calculations and experimental data analysis, the width of the segment of each

curve that works well with the parabola fit is a constant

145
1610 The Journal of Physical Chemistry, Vol. 84, No. 12, 1980

Figure 7. Effect of the slip correction. Shifts of data from seven runs and several chambers were measured with respect to calculations employing the slip correction (dotted lines) and with respect to calculations using Stokes law only (solid lines).

Figure 8. Typical calibration data. These curves show shift vs. diameter

for three runs from one chamber. The shifts reflect the differences between the settling velocities measured by the Doppler shift and the

settling velocities calculated from the optical diameter (abscissa) by

using Stokes law only. Slanted lines show the shifts corresponding

to the indicated diameter changes as a function of diameter. This relates the error in diameter determination to the scatter in the shift measurements.

fraction of the total segment between adjacent features. Figure 4 illustrates the determination of velocity shifts. A feature is not used if there are insufficient particles to give a measurable peak (or valley).

Changes in temperature shift the features (Figure 5, curve A) because of temperature dependence of the index

of refraction and density of the particles and the viscosity

of air. The apparent velocity shifts are small for the ex- perimental temperature deviations of 0.5 °C or less. Since the diameter is related to the Doppler frequency

by eq 1 and 2, a calibration measurement is a verification of these equations, especially of the value of the densityviscosity ratio. If the shifts for a measurement are all near

zero and if the index of refraction is correct, then the ratio must be accurate. The sensitivity of the calculated feature positions to changes in either the ratio or the index of

refraction is shown by examples in Figure 5. Also illus- trated in Figure 5 is the mathematically possible but ex- perimentally unlikely instance of compensation of errors

in the two above parameters. In cases such as this, where

the fractional error in the ratio is -6 times that in the index

of refraction, all shifts are expected to be near zero. Experimentally, such changes in the parameters are not ex- pected because the droplets were made from pure DOP

in contact with glass only.

There is some additional light scattered into the PMT

from the particles at an angle of 174°. The windows of tube A are almost perpendicular to the beam, and 9% of the Ught going through the second window is reflected back

into the aerosol from each surface. The Doppler frequency

associated with this light is the same as with the 6°

Bright, Fletcher, and Chabay

scattered light; this additional reflected light potentially

could distort the Mie features and shift their positions.

Curve B of Figure 5 shows that these shifts are minimal.

Reflected light is ignored in all other calculations. The repeatability of feature position measurements is illustrated in Figure 6. The slight amount of scatter for any one feature is due to the manual stage of the measurement process, and the larger scatter from feature to feature is due to the statistical nature of the data. The accuracy with which the PDSS can measure velocities suggests that other effects on velocity might be- come experimentally observable such as hydrodynamic

particle-particle or particle-wall interactions. For the

diameters in use, however, the chamber should give a wall

effect^^ one order of magnitude below that presently detectable. Particle-particle interactions should not be

significant. Although theoretical predictions of such in- teractions for randomly sized droplets are not available,

calculations for monodispersed droplets are.® The particle

concentration in the chamber was never above several hundred cm~^. When the number-averaged sized droplets

with this concentration is used, these calculations predict

the magnitude of this effect to be again an order of magnitude below that presently detectable. Results

The noise level or variability of the PDSS shift measurements is illustrated by the solid curves in Figures 7 and 8. This variability is small enough to allow measurement of the slip phenomenon. The dotted curves of Figure 7 show the differences between the measured velocities and the calculated velocities when the slip-corrected Stokes law is used, i.e., eq 2 and 3. The slip cor- rection overpredicts the settling velocities (the downward

trend of the dotted curves) while stokes law, eq 2, provides

best agreement with the data (the near zero shifts of the

solid curves). Thus any slip phenomenon is much less than

predicted. Equation 3 is not valid for this size range at atmospheric pressure.

Finally, the accuracy of the PDSS is shown by the small

magnitudes of the velocity shifts. The slanted lines that

form a varying diameter scale in Figure 8 shows the deviations in diameter via eq 2 that result from the velocity

shifts. From runs such as these, diameter measurements

of 5-15-/im DOP aerosol are cedibrated to within 0.05 tim. Conclusions

The internal calibration of the PDSS has been demonstrated for spherical particles. Velocity shifts average less than 0.002 cm/s. Most of the diameters from the settling

velocities and the nonslip-corrected Stokes law match the

optical diameters to within ±0.05 mm- In the 5-15-Mm size range, we believe this to be the most accurate real time

size measurement of droplet diameter.

We have used the PDSS for calibrating an optical particle counter® and for measuring small air flows induced

by a settling particle stream.^® We plan to use the PDSS for calibrating other instru- ments and monodisperse aerosol generators, for investi- gating the aerodynamic and light scattering properties of

aerosols, for measuring the deviations from Stokes law due

to slip for small particles in a partial vacuum, and for measuring the deviation from Stokes law due to turbulence

for larger particles.

References and Notes

(1) S. Berg, Powder TechnoL, 10, 1 (1974).

(2) R. Davies. Am. Lab., 10, 97 (1978).

(3) J. W. Sadowski and E. Byckling, Powder TechnoL, 20, 273 (1978).

(4) K. T. Whitby and R. A. Vomela, Environ. Sci. Technol., 1, 801 (1967).
1611

(5) D. Y. H. Pui and B. Y. H. Liu, "TsI Quarterly", TSI Inc., St. Paul, MN, May/June 1979.

(6) D. D. Cooke and M. Kerker, Appl. Opt., 14, 734 (1975).

(7) B. Y. H. Liu, R. N. Berglund, and J. K. Agarwal, Atm. Environ., 8, 717 (1974).

(8) K. T. Whitby, D. A. Lundgren, and C. M. Peterson, Int. J. Air Water

Pollut., 9, 263 (1965).

(9) R. A. Fletcher, G. Mulholland, I. Chabay, and D. S. Bright, J. Aerosol

Sci., in press.

(10) J. P. Gdlub, I. Chabay, and W. H. Flygare, Appl. Opt., 12, 2838 (1973).

(1 1) J. P. GoUub, I. Chabay, and W. H. Flygare, J. Chem. Phys., 61, 2139

(1974).

(12) I. Chabay and D. S. Bright, J. Colloid Interface Sci., 63, 304 (1978).

(13) C. N. Davies, Proc. R. Soc. London, 57, 18 (1945).

(14) H. Z. Cummins and H. L. Swinney, FYpg. Olp., 8, 135, 155, 157 (1970). (15) S. K. Freidlander "Smoke, Dust and Haze: Fundamentals of Aerosol

Behavior", Wiley, New York, 1977, Chapter 2. (16) R. A. Fletcher, D. S. Bright, and I. Chabay, J. Phys. Chem., this issue. (17) B. Y. H. Liu, V. A. Marple, and H. Yazdani, Enviorn. Sci. Techno!.,

3, 381 (1969).

(18) R. Chang and E. J. Davis, J. Colloid Interface Sci., 54, 352 (1976).

(19) E. J. Davis and A. K. Ray, J. Aerosol Sci., 9, 411 (1978).

(20) R. A. Millikan, Phys. Rev., 22, 1 (1923).

(21) M. Kerker, “The Scattering of Light and Other Electromagnetic

Radiation", Academic Press, New York, 1969.

(22) J. V. Dave, “Subroutines for Computing the Parameters of Elec- tromagnetic Racfiation Scattered by a Sphere", Report No. 320-3237, IBM Scientific Center, Palo Alto, CA, May, 1968.

(23) J. Happel and H. Brenner, “Low Reynolds Number Hydrodynamics

with Special Applications to Particulate Media", Prentice-Hall, En- glewood Cliffs, N.J., 1965.

147
AIR FLOWS INDUCED BY SPARSE CLOUDS OF DROPLETS

by

David S. Bright, Robert A. Fletcher and Howard R. Baum

Submitted to Journal of Fluid Mechanics

148
Experimental Variables

a

r

R

''o Ud(a)

U^Ca)

u(r)

fh

U = y u(r)dr

0

F(a)

n

y

p

droplet diameter

distance from axis of chamber

inner radius of chamber

radius of droplet column

Doppler velocity of droplets downward past chamber

windows

Stokes velocity of droplets, calculated using

optically measured diameters

air velocity induced by droplets, u(r) =

U^(a) - U^(a)

measured air velocity = u(r) averaged across

droplet column (positive downward)

3 force on 1 cm air by one droplet = biryaU^Ca)

3 droplet number density, #/cm

viscosity of air

density of droplets

Dimensionless Variables

k = Rq/R

P = r/R

U’ (n) = yu(a)/R^nF

dimensionless radius of particle column

dimensionless distance from axis of chamber

dimensionless air velocity

149
I. Abstract

Very slow air flows (.01 cm/s) , induced by a column of 5

-

15 ym diameter droplets settling in a 9 mm diameter chamber were

measured with a laser light velocimeter apparatus. We measured

the air flow velocity as the difference between the Dopplermeasured Stokes settling velocity of individual droplets and the

settling velocity calculated from simultaneous optical measurements

of droplet diameter. Experimental conditions included a wide

range of droplet sizes, relatively slow air motion, and many

droplets being in the laser beam at the same time.

We describe the interaction of the particles with the air in

terms of a simple two-fluid model with an exact solution of the

Navier-Stokes equation.

150
II. Introduction

The theory of suspensions is currently in a state of active

development. Many models employ particle-particle interactions

via the fluid medium, Happel (1965) and Fuchs (1964) . Batchelor

(1972), in particular, has performed a series of studies based on

the analysis of pairs of randomly placed spheres. The recognition that the particle-fluid interaction cannot be calculated by

treating the particles as a fixed array has led to a variety of

other approaches, Nagatani (1978), and to a statistical theory of

suspensions. A recent review of this work is given by

Herczynski and Pienkowska (1980)

.

Although statistical approaches have led to greatly increased

understanding of the collective interactions between particles,

they are difficult to apply to experimental macroscopic flow

problems. Here, we introduce the "two-fluid" model to analyze

our experiments. This model assumes that the positions of

droplets at different locations are completely uncorrelated,

allowing the droplets to be described by a number density only.

While providing less detailed information than Batchelor's

approach, the model does permit direct computation of the fluid

flow induced by the settling droplets.

The two-fluid model agreed well with this experiment:

We measured the velocities of slow air flow caused by settling

aerosol droplets. The 5 to 20 ym diameter droplets settled by

gravity down the center of a closed glass tube. When there was

an annular droplet free region surrounding the column of droplets,

the air moved down the center of the tube and returned back up

151
the annular region surrounding the column. When the cross

section of the tube was uniformly filled with droplets, no

motion was detected. The air velocity was determined in a and accurate manner based on laser Doppler velocimetry and

Lorentz-Mie light scattering of spheres. The air motion

determined to within 0.002 cm/s, ranged from approximately

cm/s to 0.015 cm/s and varied linearly with droplet number

air

unique

on the

0.002

concentration.
III. Theory

To model the particle induced air flow, we make the following

assumptions

:

1) There is an inner cylindrical droplet-air fluid phase inside

a coaxial air annulus which is the second fluid phase

(figure 1) . Each phase may be described by mass and momentum

transport equations. In the droplet phase, coagulation and

diffusion may be ignored.

2) The mean droplet velocity relative to the air, of magnitude

Ug(a), is directed vertically downward. The droplets have

reached a steady state and are no longer accelerating.

3) The tube in which the measurements are made is sufficiently

long for all quantities near the measurement volume to be

taken as independent of distance along the tube.

Under these conditions the size distribution n(r,a) is given

by:

n(r,a) = nQ(a) 0 1 r < Rq

=0 Rq < r < R

and U^(a) is given by Stoke 's law:

4 3 ^

Ppa g

= birayUgCa) = F(a).

Here, r is the radial distance from the centerline of the

measurement tube, Rq is the radius of the droplet stream (figure

1) , R is the tube radius, Pp is the droplet density, y is the

viscosity of the air , g is the gravitational acceleration, nQ(a)

is the spatially averaged droplet number density, and F(a) is the

force exerted on the air by one droplet. The air phase mass and

momentum balances are given bv:

153
i u(r) rdr = 0

R

?

^ ^

Jo F(a)da

^2)

where u(r) is the air velocity and ^ is the unknown pressure

gradient, taken to be independent of z. Equation (2) must be

integrated subject to the following boundary conditions:

u(r=R) = 0

^(r=0) = 0

(3)

Moreover, at r = Rq, the velocity u(r) and shear stress ydu/dr

must be continuous. Since the viscosity y is constant (recall y

is the viscosity of the air anci not of the suspension) , this

reduces to a requirement that ydu/dr be continuous at droplet

stream boundary Rq. Note that the inertial acceleration terms

vanish identically in this geometry without approximation. This

fact, together with assumption (2) means that equations (1) and

(2) are an exact set of equations for this two-fluid model.

These equations can be readily integrated to yield:

U-= ^ log(k) - (1 - k'=) ;

0 £ n £ k.

k^ _2, k^ U’= (2 - k")(l - n") - 5- log Cn); T"

k < n < 1. (4)

where dimensionless forms for u(r), r and R^ are respectively

, ^ yu(r)

U' E r _ R^noF

K

- 1, and

^0

^ = k, and where

154
da .

00 iIqF =J n^Ca) F(a)

'0 “ C5)

The results are plotted in dimensionless form in figure 2. Positive values of u(r) denote downward motion. The upwelling on the

side is needed to ensure an air mmass balance since the tube is

blocked off at the bottom. Note that there is no induced flow if

the tube is uniformly filled with droplets. The absolute motion

of the droplets relative to the laboratory, U^, is then given by:

^d^^^

= UgCa) + u(r)

.

It is this formula which is tested against the experiments to

which we now turn.

155
IV. Experimental

Dioctylphthalate (DOP) droplets were generated with a medicinal atomizer. The atomizer air flow rate controlled the

number density of the droplets, but did not appreciably affect

the relative size distribution. The atomizer was modified to

remove the impaction surface that ordinarily collects most of the

droplets above tw# to three micrometers in diameter. The cloud

of droplets then passed through a krypton- 85 neutralizer, and

then through tube B Cfigure 3). For a velocity measurement, the

valves were closed for 500 s and the droplets were allowed to

fall through tube A, the orifice and the laser beam, and then

allowed to settle onto the microscope slide. Immediately after

the measurement, the microscope slide was removed, droplets

were counted, and both tubes were flushed with air. The droplets

ranged in diameter from about 5 ym, those large enough to reach

the laser bean during the 500 s measurement period, to about

15 ym.

The radius of the stream of droplets, Rq

,

was fixed by the

radius of the orifice (see figures 1 and 3) . was assumed to l|j

be constant throughout the height of the chamber (tube B) because

||

the droplets formed a clear image of the orifice on the slide

'rl

•'I after settling over 15 cm. ‘!

The motion that the droplets induced in the air was measured ij

by a laser light scattering technique. Bright, Fletcher § Chabay |!

(1980) and Fletcher, Bright § Chabay (1980). Briefly, the falling||

velocities of the droplets were measured relative to the chamber

windows by a single beam laser Doppler velocimetry technique |,

(figure 3) . Data was collected for the entire width of the ' i ,

156
droplet stream that was intersected by the laser beam (figure 1)

.

The velocity of the air was the excess of the falling velocities

over the Stokes velocities calculated using the optically measured

diameters. The diameters were measured by light scattering

measurements done concurrently with the velocity measurements.

The light scattering size measurements were performed on a collection of droplets as follows: Data for a broad size distribution of droplets, such as generated here, appeared as a curve

of light intensity vs. droplet velocity, U^, with about twenty

peaks and valleys or features. This was because the 500 second

summation of data averaged out the much narrower signal peaks of

the individual droplets, but retained the broader variations of

intensity vs. size due to the properties of light scattered from

spheres. In other words, the features corresponded to droplet

diameters that scatter the laser light most or least strongly at

the 6 degree scattering angle (figure 3) . The features were

matched along the velocity axis with similar features in a calculated curve, Kerker (1969), of Lorentz-Mie light scattering

intensity vs. Stokes settling velocity for droplets of known

index of refraction and density. The index of refraction and

density of the bulk DOP liquid were measured by standard techniques at NBS.

The velocities for these feature diameters were U^(a) and (a)

for the data and Lorentz-Mie-Stokes calculations respectively.

In air moving up or down, the velocity of the air, u(r) = U^(a)-U^(a),

is the velocity of each data feature with respect to the corresponding Lorentz-Mie-Stokes feature.

157
The air velocities reported were the averages of velocity

measurements for the twenty or so feature diameters between

5 and 15 ym. The Doppler velocities, U^Ca), were measured to a precision of better than 0.002 cm/s and the diameters to a precision of better than 0.03 ym, allowing a determination of air

velocities from 0.002 to 0.015 cm/s even though U^(a) and U^(a)

were in the range of 0.1 to 0.7 cm/ s

.

Absolute concentrations of the droplets could not be determined from the light scattering data due to an undetermined

amount of background shot noise that would change with very

minute shifts in chamber orientation. However, the data did

provide an estimate of the relative size distribution, from which

a mass mean diameter was determined, and from which the force

term, n F was calculated.

Total droplet concentrations were determined from microscope

slide counts. The slides with oil repelling surfaces collected

the settling particles for the 500 s measurement.

158
V. Results

The predictions of the two-fluid model agree well with the

data from two experiments, as shown in figures 4 and 5. For

these experiments the air velocity uCr) , integrated along the

laser beam was

:

In figure 4, the induced flow is maximized for a droplet stream

of about one half chamber diameter. Here, the droplet stream

radius, Rq

,

is varied by changing the orifice, while the droplet

concentration is not changed. When the droplet concentration is

changed with Rq constant, as in figure 5, the induced flow

velocity is directly proportional to the force term, nQp (equation

5). Because the relative size distributions were similar, the

mass mean diameter varied by less than 4 percent. Thus, the

force term, HqF, and the flow velocity were proportional to the

droplet concentration or slide count. The mass mean diameter was

estimated from the light scattering data to be 12.8 ym. The

droplet concentration was estimated from the slide counts of

collected droplets and the volume of a cylinder with a base of

the counted slide area and a height equal to the distance that a

12.8 ym droplet falls in 500 s. The diameter and concentration estimates are crude and both

parameters are in fact changing during the measurement period as

the larger droplets settle out first.. In spite of this, our

calculated air velocities from the two-fluid model stay within

10 to 20 percent of the experimental measurements as shown in

figures 4 and 5.

159
VI. Conclusions

We have demonstrated experimentally that an air column

sparsely populated with droplets can be modeled as a homogeneous

fluid. This was verified by measuring air velocities less than

150 ym/s using small droplets as probes. The index of refraction

and density of the droplets must be known, but their radii need

not be measured by other means. A distinctive feature of the twofluid model is the linear dependence of the induced air velocity

on droplet concentration.

160
References

BATCHELOR, G. K. 1972 Sedimentation in a dilute suspension of

spheres. J. Fluid Mech ."S2, 245.

BRIGHT, D. S., FLETCHER, R. A. § CHABAY, I. 1980 Particle Doppler

shift spectrometry. Accurate size determinations of 5 - 15 ym

aerosol. J. Phys. Chem . 84 , 1607.

FLETCHER, R. A., BRIGHT, D. S. § CHABAY, I. 1980 Low Reynolds

number fluid flow induced by settling aerosol and detected

by particle Doppler shift spectrometry. J. Phys. Chem . 84 , 1611.

FUCHS, N. A. 1964 The Mechanics of Aerosols . The McMillan Company,

New York, p. 46.

HAPPEL, J. § BRENNER, H. 1965 Low Reynolds Number Hydrodynamics

with Special Applications to Particulate Media . Prentice Hall,

Englewood Cliffs, New Jersey.

HERCZYNSKI § PIENKOWSKA. 1980 Toward a statistical theory of

suspension. Ann. Rev. Fluid Mech . 12 , 237.

KERKER, M. 1969 The Scattering of Light and Other Electromagnetic

Radiation . Academic Press, New York.

NAGATANI, T. 1978 Statistical theory of effective viscosity in a random suspension. J. Phy. Soc. Japan 47 , No. 1, 320.

161
9 mm Chamber Diameter

4

Figure 1. Geometry of the experiment: — schematic diagram of the

measurement chamber and droplet stream.

162
OCo

<D

d

5-1 > W

<D

O t/5 •H ^ n3 <D

+-> IS i-i O <U d d 5-*x: o d O H -H m md to rt do

•H • • +J / N

d 'H LO

(U ^3

(Od

<ubO bO'd d <0 • H

1-H <D

*-H

X

(U -M

ISp^'d d dd

<D I—I /—\

X5 <-H d II d cr D wd £

pdO (Dd o d O II d o <u rdH

,d

d 0 4-> <D •

to i-H d d o IS u d

to 0

'H ^ d P! ^ G d »' G P d 0 d d X

to to iH ^ • 0 u p to pu u ^rd

•H o G o H 0 d d d 0 II , rC d o X rd d • d

Pi

d 0 d o d

to ^ d <d

d

d 0

to o o o 0 d 0 0 rH <d d d IS

1-4 <4-1

d

d

d

d •'0 0 0 o d 0 d U • rd

•H •H

d 0 ' to d o G P d d Z d rd LO o 0 <D -H d • -H G rd d o bo •H d • d II P Q G P d d d

M-l

d rd o 0 4->

d

d 0 d +-> td N O to r—I *H •H d G

+J -M rd -H O 0 X

•H rH to

d

d fti-H 6 0 o ^ d G

pndd

r-l 0 0 ,d d 4-> oG o dG <u d Pu 0 d d X +-> to

to

d '—

0 d LO rd »H • •d P O d II 0 d d d ^ o

CMo

CMo

•H 0 p.

d P M O *H

r-l 'H

dd

<4-1 to

d

d 0 0 d

IS

XX

d

H 4-> 4-> IS

to 0 d rP P d O d £d0dd

to I o d d 0

p: -H

X

bO

d

d

•H

t-l <d <-H to o o

CM

(pjBMUMOp aAxq.isod)

,n ‘X:n:3OX0A jtv ssaiuoTsuauiiQ 0dP

bO

•H
ifi ooU*90 • O

0 a a o CMP <9 W O <• O

sv »-» w o» a. hh

H <t >«• C ’M

: c a «* o

O tXM

a C -

ti»

' ^ >4* t4» th o -• «>vwtt 9> n b»

*"• ciL P

1 » ^ Of*

T "a M ihi» •» K*

i

A'.I’

cr

' «* m tf XJ •» M *4» eu »• , H* a.«rfs m , 1] lU t+- *•JDL. U *4

. #• H P O

tj Hi IV rv di <* n H*«j3 tr

. tMf a. DO O c fv a M M

» a >-* a a o o

sr a M

K*© W* 8

^ M H. M U

a» M. o

^ V* c o t» »4* ai M o i o a

< a- cr M W»-M; o *.

C

a.*^Jx U thiM O

K< M <* O O

•»* tH* experfkfatf •*f»cft««tic di*gr#« o? th*

(!>OtX^|A© qOMim»l.q)

f)^9dU3|0VX6«9 VXX AGJOCIfX* Hi
•H

0) d

Figure

3.

Schematic

diagram

of

the

experimental

apparatus.

Droplet

diameters

and

falling

velocities

are

measured

from

the

laser

light

scattered

at

6

degrees.

Tube

B

is

a

reservoir

for

the

droplets.

Tube

A

is

the

9

mm

diameter

measurement

chamber.

The

orifice

sets

,

the

radius

of

the

droplet

stream.
.14

0 00

CM o •0 VO rj rH tH o o o o

• • • • • • o o o o o o

s/unH ‘n ‘XiiDOisA jtv

Figure

4.

Air

velocity

averaged

across

the

illuminated

droplet

stream,

plotted

as

a

function

of

the

radius

of

the

droplet

stream.

The

two

theoretical

lines

represent

two

measurements

of

droplet

concentration.

Data

are

lacking

for

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Matrix isolation Raman spectroscopy

D.S. KING, J.C. STEPHENSON

A new primary laboratory measurement is described for testing field standards

and measurement techniques used to detect trace amounts of toxic organic

substances in water.

Until this decade, the assessment of pollutant levels in water was based on measurements of such properties as

total organic carbon or biochemical oxygen demand.

Although it was realized that these tests did not take into account the toxic properties of specific chemicals, it was

not until the discovery of specific toxic and carcinogenic

substances in drinking water supplies in the early 1970’s

that programmes to identify and quantify routinely low

concentrations of specific organic compounds were initiated. Now phrases such as ‘consent decree pollutants’ and ‘priority

pollutants’ which reflect the legislative and regulatory mandates of the last few years are commonly heard in discussions

of environmental assessment. In response to the need to

identify and quantify low concentrations of organic compounds in environmental samples, a new arsenal of sophisticated analytical instruments is appearing in environmental

laboratories. All use liquid or gas chromatography to separate the many compounds found in environmental samples.

The individual components emerge sequentially from the chromatograph, swept along by the carrier gas or liquid.

The technical challenge of the past ten years has been to develop methods to identify and measure the individual compounds in the few seconds during which they emerge

from the chromatograph.

Several months ago, the authors initiated a programme, to develop a primary laboratory measurement method suitable for analysis of Standard Reference Materials (SRM’s) or for referee-type measurements of trace toxic organics in water. This new method, involving laser Raman scattering from

pollutants isolated in cryogenic matrices, should provide an

alternative technique for the analysis of pollutants of the type on the EPA lists of regulated chemicals with a molecular

specificity and sensitivity comparable to, or better than,

existing techniques (eg, gas chromatography and mass

spectrometry).

Any realistic approach to the identification and quantification

of individual trace organic compounds in a complex sample

must begin with the application of modern separation procedures, such as liquid or gas phase chromatography. However, even verjj efficient separation procedures may be unable to do more, in a realistic time frame, than to produce a

series of fractions which themselves are rather complex

mixtures. Therefore, any successful analytical procedure for

The authors are at the Molecular Spectroscopy Division, B268

Physics Building, National Bureau of Standards, Washington D.C. 20234, USA. Paper received 6 December 1979

the qualitative and quantitative analysis of complex mixtures of organics must incorporate a secondary and moleculespecific measurement method. Our approach involves three

steps:

1. sample acquisition and initial separation,

2. matrix isolation,

3. spectroscopic analysis.

The total volatile pollutant content of the aqueous sample

will be acquired by dynamic head-space sampling followed

by concentration on a precolumn, and then separation on a gas chromatography (GC) column using argon as the carrier gas. The GC will separate the initial mixture into several fractions containing either a single or small number of

physically or chemically similar molecular species. As the pollutants elute out the GC, a responsive valving system will be used to take cuts, or small sample amounts, of the eff- luent stream. These cuts will then be sprayed onto a cold

finger, cryogenically maintained at 12 K. Both the organic

pollutant and the argon carrier gas are frozen in a spot

approximately 1 mm in diameter. The cold finger is rotated,

in a step-like fashion, between sample cuts to maintain the

initial separation achieved in the GC. Each sample containing

only the compounds, if any, that emerged from the chromatograph during a specific one to three second period

and now frozen dilute in an argon matrix, is sequentially

analyzed by matrix isolated laser Raman spectroscopy as it is stepped into view of a high resolution spectrometer. If chemical compounds are present in the region irradiated by

the laser, they will re-emit light at wavelengths different from

the wavelength of laser. This re-emitted Raman scattered

light is characteristic of the compound(s). The intensity of

the Raman scattered light is proportional to the amount of

the compound present. As in the other detectors that have

been developed for chromatographs, a small computer is needed to analyze the vast amount of data being generated

and to present it in a form useable by the environmental

analyst.

Matrix isolated laser Raman spectroscopy is used as the

diagnostic means for several reasons: 1 . Raman spectroscopy

is a vibrational spectroscopy and as such provides a characteristic and reproducible ‘fingerprint’ that carries structural information to allow for the unambiguous identification of

unknown contaminants; 2. All molecules have characteristic Raman spectra in an experimentally convenient spectral range; 3. The matrix substrate (in this case argon) is free of

organic contaminants and has no spectral interferences; it is 0030-3992/80/020097-02 $02.00 © 1980 IPC Business Press OPTICS AND LASER TECHNOLOGY . APRIL 1980

O.L.T. 12/2—D 167

97
T Matrix- isolation Raman spectroscopy

Benzene / Ar

Fig. 1 Matrix isolated Raman spectrum of benzene. High resolu- tion scan of the mode of 5 n gram benzene isolated in argon at

1 1 K. The scan was acquired at 0.1 cm”^ resolution in 20 seconds.

Fig. 2 Matrix isolated Raman spectra of three dichloroethylene

isomers. The spectra were acquired at 5 cm~^ resolution in ten minutes. The dotted peaks are Oj and Nj 'spiked' into the initial gas mixtures to aid in quantification. Also shown, to the right, is a

closer look, at 1 cm~^ resolution, of the 1500-1600 cm"^ region.

transparent and allows the vibrational frequencies of the trapped pollutant to be readily compared to the gas phase

values of known, pure compounds; 4. At the low temperatures used, all rotational motion is frozen out, and the

spectral linewidths are very sharp, so sharp that the over- lapping of bands observed in solution and in the gas phase

is not a problem.

Although the engineering aspects of interfacing the technologies of sample acquisition, gas chromatography, and matrix

preparation have not been fully implemented, matrix iso- lated Raman spectra have been obtained for laboratory

samples of many of the toxic organics on the EPA’s regulated list; benzene and substituted benzenes, halo-menthanes,

ethylenes, and ethanes. Significantly, vibrational bandwidths were observed of about 1 cm"* (see Fig. 1). By

contrast, room temperature gas or liquid phase bandwidths

are about 50 cm”*; with such large bandwidths the spectral

lines of many toxic and non-toxic compounds overlap,

making analysis difficult or impossible. On the other hand,

due to the narrowness of the spectral features in the low

temperature matrix, spectra of these molecules are readily resolved; there is no difficulty in, for instance, analyzing

mixtures of different molecular isomers (molecules with

the same chemical formula but differing arrangements of

the constituent atoms) such as cis, trans, and 1 ,1 -dichloro- ethylene (see Fig. 2). With our present and far from optimum

optics and low-power laser nanogram quantities of a wide

variety of toxic organics can readily be detected. Matrix isolated Raman spectroscopy may be favourably

compared to the other techniques utilized in the analysis

of low-level mixtures of complex organic species. Although

similar in principle to infra-red absorption spectroscopy,

Raman spectroscopy is inherently more sensitive (basically,

in Raman spectroscopy one looks for small signals in the absence of any background while in infra-red absorption one

looks for a small change in an otherwise very large continuum

background). The Raman process is not prone to the inter- ference problems that energy transfer introduces to fluore- scence type measurements. Also, many regulated pollutants

either do not fluoresce or they have electronic absorption

spectra which are very broad or are in the experimentally

difficult vacuum ultra-violet region. Although mass spectrometry has an equivalent sensitivity, it does not have the

specificity of the Raman diagnostic (mass spectrometry cannot readily distinguish between similar species, such as isomers, even when one of these is regulated by the EPA

while others are not).

The work to date has clearly demonstrated the feasibility

of our technique for preparing and spectroscopically analyzing small quantities of complex organic molecules. It is now planned to use high-intensity pulsed laser Raman

scattering, with gated electronics, to improve sensitivity

and an optical multichannel analyzer with computer inter- facing to reduce sampling time and to provide for rapid

comparison of an ‘unknown’ spectrum to reference spectra. The feasibility of interfacing our sensitive detection apparatus to a liquid chromatograph for the analysis of nonvolatile environmental and biological samples is currently

under study. Although in its initial stages of development,

this method, which is being developed with partial support

by the U.S. Environmental Protection Agency, promises to be a major advance in the analysis of organic compounds.

OPTICS AND LASER TECHNOLOGY . APRIL 1980

168

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U.S. Departnluant of Commerce

Juanita Kreps

fecRtaatyf’

Ernest

National I iuMnir of Standards

(kinb^r, pircctor

J^alto«al ^ureaw of ^tanrfarrfo

Certificate

Standard Reference Material 2630

Nitric Oxide in Nitrogen

(Mobile-Source Emission Gas Standard)

(In Cooperation with the Motor Vehicle Manufacturers Association)

This Standard Reference Material is a mixture of nitric oxide in high purity nitrogen which is supplied in a highpressure, compressed gas cylinder. The statistical uncertainty in each step of the preparation and analysis of this mixture has been carefully evaluated at the 95% confidence level. This Standard Reference Material should be

used sparingly as a valuable primary standard to which daily working standards may be related. CAUTION: Every precaution must be taken to avoid accidental contamination of the sample with atmospheric

air during connection of the cylinder to any gas-handling system.

Nitric Oxide Concentration: ± /nmol/ mol (ppm)

Cylinder Number: Sample Number:

The concentration of nitric oxide is relative to all other constituents of the gas. Each cylinder of gas is individually analyzed, but the concentration appearing on this certificate applies to all samples within the lot. The concentration of all samples in the lot fell within a limit of ± 0.3 percent of the

average for the lot and all samples are considered identical within the stated limits of accuracy. The estimated

upper limit of error of the nitric oxide concentration is ± 1.0% relative. This estimate is the 95% confidence

interval based on allowances for known sources of possible error. The research and development of this Standard Reference Material was supported by the Motor Vehicle Manufacturers Association of the United States, Inc. (MVMA), Detroit, Michigan.

The development and evaluation of the gravimetric primary standards used to certify this Standard Reference

Material were performed at the National Bureau of Standards by MVMA Research Associates W. R. Miller and

W. J. Thom.

The overall direction and coordination of the technical measurements leading to certification were performed

under the chairmanship of E.E. Hughes and H.L. Rook.

The technical and support aspects involved in the preparation, certification and issuance of this Standard Refer- ence Material were coordinated through the Office of Standard Reference Materials by W.P. Reed.

Washington, D.C. 20234 George A. Uriano, Chief

May 2, 1979 Office of Standard Reference Materials

(over)

i' 169
Analysis:

The nitric oxide content of this Standard Reference Material was determined by comparison with secondary

standards that had been previously intercompared with a set of primary gravimetric standards. The method of

intercomparison utilized the chemiluminescent reaction of nitric oxide with ozone. The upper limit of the total uncertainty including both the imprecision of intercomparison and the inaccuracy

of the gravimetric standards is less than 1.0% relative at the 9S% confidence level. At least 8% of the samples from the lot have been analyzed for nitrogen dioxide by a wet chemical method (a

modified Saltzman technique). The maximum concentration of nitrogen dioxide did not exceed 0.5% relative to the nitric oxide in the samples analyzed.

Stal^ty:

These samples are contained in aluminum cylinders. The stability is considered excellent and no losses of nitric oxide have been observed for similar samples contained in aluminum cylinders for periods of time greater than 2

years. The value appearing on this certificate is considered valid for 2 years from date of purchase. Periodic

reanalyses of represmtative samples from this lot will be performed, and if significant changes are observed

within a one year period the purchasers of other samples from the lot will be notified. Validation of the

concentration of nitric oxide in cylinders that have been in the possession of the purchasers for more than one

year can be made by the National Bureau of Standards at a nominal charge if more than 1000 psi remains in the

cylinder.

Cylinder:

These gases are supplied in cylinders with a delivered volume of 0.85 m^ (30 cubic feet) at STP. The cylinders

conform to the DOT specification and are equipped with CGA 660 valves.

NOTE:

This cylinder is the property of the purchaser. If the user is unable to dispose of the cylinder it may be returned,

prepaid, to the National Bureau of Standards for disposal.

170
U.S. Department of Commerce

Juanita Mv Kreps

Secretary %

National Bureau of Standards

Ernest Ambler, Director

i

!

I

i

j

i

Rational ^urrau of ^tanttards

Certificate

Standard Reference Material 2631

Nitric Oxide in Nitrogen

(Mobile-Source Emission Gas Standard)

(In Cooperation with the Motor Vehicle Manufacturers Association)

This Standard Reference Material is a mixture of nitric oxide in high purity nitrogen which is supplied in a

high-pressure, compressed gas cylinder. The statistical uncertainty in each step of the preparation and analysis

of this mixture has been carefully evaluated at the 95% confidence level. This Standard Reference Material

should be used sparingly as a valuable primary standard to which daily working standards may be related. CAUTION: Every precaution must be taken to avoid accidental contamination of the sample with atmospheric

air during connection of the cylinder to any gas-handling system.

Nitric Oxide Concentration: ± yumol/mol (ppm)

Cylinder Number: Sample Number

The concentration of nitric oxide is relative to all other constituents of the gas. Each cylinder of gas is individually analyzed, but the concentration appearing on this certificate applies to all samples within the lot. The concentration of all samples in the lot fell within a limit of ± 0.3 percent of the

average for the lot and all samples are considered identical within the stated limits of accuracy. The estimated

upper limit of error of the nitric oxide concentration is ± 1 .0% relative. This estimate is the 95% confidence

interval based on allowances for known sources of possible error. The research and development of this Standard Reference Material was supported by the Motor Vehicle

Manufacturers Association of the United States, Inc. (MVMA), Detroit, Michigan.

The development and evaluation of the gravimetric primary standards used to certify this Standard Reference

Material were performed at the National Bureau of Standards by MVMA Research Associates W.R. Miller and

W. J. Thorn.

The overall direction and coordination of the technical measurements leading to certification were performed

under the chairmanship of E.E. Hughes and H.L. Rook.

The technical and support aspects involved in the preparation, certification, and issuance of this Standard

Reference Material were coordinated through the Office of Standard Reference Materials by W.P. Reed.

Washington, D.C. 20234 George A. Uriano, Chief

May 2, 1979 Office of Standard Reference Materials

(over)

I 171
Analysis:

The nitric oxide content of this Standard Reference Material was determined by comparison with secondary

standards that had been previously intercompared with a set of primary gravimetric standards. The method of

intercomparison utilized the chemiluminescent reaction of nitric oxide with ozone. The upper limit of the total uncertainty including both the imprecision of intercomparison and the inaccuracy of

the gravimetric standards is less than 1.0% relative at the 95% confidence level. At least 8% of the samples from the lot have been analyzed for nitrogen dioxide by a wet chemical method (a

modified Saltzman technique). The maximum concentration of nitrogen dioxide did not exceed 0.5% relative to the nitric oxide in the samples analyzed.

Stability:

These samples are contained in aluminum cylinders. The stability is considered excellent and no losses of nitric oxide have been observed for similar samples contained in aluminum cylinders for periods of time greater than 2

years. The value appearing on this certificate is considered valid for 2 years from date of purchase. Periodic

reanalyses of representative samples from this lot will be pierformed,and if significant changes are observed

within a one year period the purchasers of other samples from the lot will be notified. Validation of the

concentration of nitric oxide in cylinders that have been in the possession of the purchasers for more than one

year can be made by the National Bureau of Standards at a nominal charge if more than 1000 psi remains in the

cylinder.

Cylinder:

These gases are supplied in cylinders with a delivered volume of 0.85 m^ (30 cubic feet) at STP. The cylinders

conform to the DOT specification and are equipped with CGA 660 valves.

NOTE:

This cylinder is the property of the purchaser. If the user is unable to dispose of the cylinder it may be returned,

prepaid, to the National Bureau of Standards for disposal.

172
U.S. Departnl»itt;ilf Commerce

Juanita Kreps

Cec>u«iyp

National I Itondarda Emeit l^b^r, ttrector ^ureau of Standards

Cerftftcats of ^Anal^oto

Standard Reference Material 2673

Sulfate and Nitrate on Filter Media

This Standard Reference Material is intended for use in the evaluation of apparatus and methods used in the

determination of atmospheric particulate sulfate and nitrate which have been collected on filters. It consists of a

series of filter strips upon which sulfate and nitrate have been deposited in an essentially central location. The

values certified correspond to the quantities ofthe substances leached from the filter strip without destruction of

the filter matrix.

Sample

Number

Sulfate content /ig/ filter Nitrate content ptg/ filter

Average value Tolerance limits Average value Tolerance limits

I 503 493 - 513 100 98 - 102

II 2002 1955 - 2049 1002 978 - 1026

HI 6939 6635 - 7243 2513 2404 - 2622

Blank 2 0-6* 2 0-3*

* Range of measured values The average value is the mean based on the analysis of 24 or 28 filters randomly selected from the lot. The

tolerance limits are determined so that at the 95% confidence level they will contain the central 95% of the

population of filter values. Details of the preparation, analysis, and statistical treatment of the data are given on

the reverse side of the certificate.

This Standard Reference Material was prepared by B. I. Diamondstone. The analytical measurements were made l>y W. F. Koch. Statistical analysis of the data was provided by J. Orban. The overall direction and

coordination of the preparation and analytical measurements leading to certification were performed in the

Center for Analytical Chemistry under the chairmanship of J. K. Taylor.

The technical and support aspects involved in the preparation, certification, and issuance of this SRM were

coordinated through the Office of Standard Reference Materials by W. P. Reed.

Washington, D.C.

June 25, 1979

20234 George A. Uriano, Chief

Office of Standard Reference Materials

(over)

173
Preparation

This SRM consists of strips cut from glass fiber filters, such as are commonly used for measurements of

atmospheric particulates, using high volume samplers. Solutions containing known amounts of ptMassium

sulfate and potassium nitrate were prepared, gravimetrically, and multiple aliquots of 25 nL were placed on the

filter strips. Four aliquots were so transferred to each filter in the case of samples I and II, and five in the case of

Sample III. The pipets were calibrated by weighing similar aliquots transferred into weighing bottles. The filters were prepared in a clean room and allowed to air-dry before packaging in glassine envelopes. The

filters were prepared in groups of 100 and the proper number of aliquots were dispensed into wei^iing bottles at the beginning and end of each sequence, to monitor the performance of the pipet.

Analytical Measurements

Twenty four samples were randomly selected from the production lot (28 in the case of sample III) for chemical

measurement of their extractable sulfate and nitrate. Each filter strip was extracted with a standard eluent (see

below) for IS minutes in a SS ultrasonic bath. The extracts were analyzed for sulfate and nitrate by ion

chromatography. The eluent was a solution of 0.003 M NaHCOs and 0.0018 M Na2 C03. A 100 /xLsample loop was used. Peak heights were compared with those obtained from accurately prepared standard solutions. Three

standards were prepared for each concentration level so as to bracket the extracts. The randomly selected filters were also analyzed in random order. No significant systematic errors were

observed related to the order of preparation. Average values and the overall standard deviation, so, of

individual measurements were calculated. This standard deviation includes measurement error and filter content error. The standard deviation, Sf, due to filter content variability was computed from a sample of 12 or 14 weighed

quantities delivered by the pipets during the preparation of the filters. The resulting tolerance interval for the

sulfate /nitrate contents is of the form

X ± k Sf

It is this tolerance interval that should be of greater interest to the participating laboratory since it gives practical

bounds for the likely values of the sulfate or nitrate contents that might be found in a given fdter. The following table lists the values of so and Sf for each set of Hlters. The measurement standard deviation, Sm, for NBS can be computed using the relation so = Sm^ + Sf^

Set Average (/xg) So Sf

S04 502.6 8.89 3.14

N03 100.3 2.56 .63 S04 2001.7 29.30 14.88 N03 1001.7 15.92 7.44

S04 6939.0 109.35 100.75

N03 2513.0 43.70 36.30

The average values calculated from the composition of the solutions and the quantitites delivered by the pipets are in general agreement with the analytical values. However, the values certified are those obtained by analysis.

Recommended Usage

The material is not homogeneously distributed on the filter; hence the sample must be used in its entirety for

analysis. It is recommended that the filter be extracted at 55 °C in an ultrasonic bath, with water or other

noiireactive solvents. The filter base should not be digested to put it into solution.

174
U.S. DepaitRtent of Commerce

I Juanita Kreps

I

I ~*v' •<>- i

i National ^RMn»ofStandards

Ernest l^mbl^r, pirector

i

JCaltottal ^ureau of ^tanrfardo

Certificate of

Standard Reference Material 2674

Lead on Filter Media

This Standard Reference Material is intended for use in the calibration of apparatus and the evaluation of

methods used in the determination ofatmospheric particulate lead which has been collected on filters. It consists

of a series of filter strips upon which lead has been deposited in an essentially central location. The values

certified correspond to the quantities of the substance leached from the filter strip without destruction of the

filter matrix.

Sample No.

Lead Content, /xg/ filter

Average Value Tolerance Limits

1 100 97 - 103

II 303 294 - 312

III 1505 1477 - 1533

Blank 1.4 0.7- 2.1*

I *Range of measured values

I The average value is the mean based on the analysis of 26 or 28 filters randomly selected from the lot. The

j tolerance limits are determined so that at the 95% confidence level they will contain the central 95% of the

I

I population of filter values. Details of the preparation, analysis, and statistical treatment of the data are given on

the reverse side of this certificate.

5, This Standard Reference Material was prepared by B. 1. Diamondstone. The analytical measurements were

I made by £. J. Maienthal and M. S. Epstein of the Inorganic Analytical Research Division. Statistical analysis of

the data was provided by J. Orban of the Statistical Engineering Division.

The overall direction and coordination of the preparation and analytical measurements leading to certification

j were performed in the Center for Analytical Chemistry under the charimanship of J. K. Taylor.

I The technical and support aspects involved in the preparation, certification, and issuance of this SRM were

1 coordinated through the Office of Standard Reference Materials by T. E. Gills.

1 Washington, D.C. 20234

December 18, 1979

(over)

George A. Uriano, Chief

Office of Standard Reference Materials

175
Preparation

This SRM consists of strips cut from glass fiber filters of the type normally used in high volume samplers for the

measurement of atmospheric particulates. Solutions containing known amounts of lead nitrate were prepared

gravimetrically, and aliquots of 25 fiL were placed on the filter strips using micropipets. Four aliquots were

transferred to each filter in the case of samples I and II and five in the case of sample III. The pipets were

calibrated by weighing similar aliquots transferred into weighing bottles. The filters were {M’epared in a clean room and allowed to air-dry before packaging into glassine envelopes. The

niters were prepared in groups of 100 and the proper number of aliquots were dispensed into weighing bottles at the beginning and end of each sequence, to monitor the performance of the pipet.

Analytical Measurements

Twenty-eight filters were randomly selected from the production lot (26 in the case of Sample I) for chemical

measurement of extractable lead. Selected filters were extracted with dilute nitric acid, using ultrasonic

vibration to assist in the extraction. After the nitric acid extraction, the filters were thoroughly rinsed with

distilled water to ensure complete extraction. The extracts were quantitatively diluted and analyzed by linear sweep voltammetry which had been calibrated with solution standards prepared from high purity lead. The selected filters were analyzed in random order. No significant systematic errors were observed related to order of preparation. Average values were calculated together with the overall standard deviation, So, of

individual measurements. This standard deviation includes measurement error and filter content error. The

resulting confidence interval for the mean is of the form

X ± t So//~lT,

where So is based on n - 1 =27 degrees of freedom.

A selected number of filters were also analyzed by atomic absorption. The results obtained were well within the

tolerance limits given and were consistent with the certified values. The standard deviation, Sf, due to filter content variability was computed from a sample of 12 or 14 weighed

quantities delivered by the pipets during the preparation of the filters. The resulting tolerance interval for the

lead content is of the form

X ± k Sf

It is the tolerance interval that should be ofgreater interest to the participating laboratory since it gives practical

bounds for the likely values of the lead content that might be found in a given filter. The following table lists the values of So and Sf for each set of filters. The measurement standard deviation, Sm, for NBS can be computed using the relation So‘^= Sm"^ + Sf

Set Average (ng) So Sf

I 99J 1.59 0.89

II 302.9 5.37 3.00

III 1505.2 12.73 9.24

The average values calculated from the composition of the solutions and the quantities delivered by the pipets are in general agreement with the analytical values. However, the values certified are those obtained by the

analysis.

Recommended Usage

The material is not homogeneously distributed on the filter, hence the sample must be used in its entirety for

analysis. It is recommended that the filter be extracted at 45-50°C in an ultrasonic bath, with dilute nitric acid (2

mL HNO3 + 15 mL H2O). After extraction the filters should be thoroughly rinsed with distilled water. The filter base should not be dissolved.

176
'.S. I )f|>ari menu nl' ('oinmeri-c

•luanila M. Krepa

Secretary

NHtionHl Bureau of SundardK

KrnpHi Ambler. IJiiw-tur ^umw of ^fantbrrfo

Certificate of (Anal^oio

Standard Reference Material 2657

Oxygen in Nitrogen

(Gas Standard)

This Standard Reference Material is intended for use in the calibration of instruments used for combustion

control and respiratory gas analysis. It is not intended as a daily working standard, but rather as a primary

standard to which the concentration of the daily working standards may be related.

The concentration of oxygen is relative to all other constituents of the gas. Each cylinder is individually analyzed and the concentration that appears on this certificate applies to the

cylinder identified by cylinder and sample number.

The original development and evaluation of the oxygen in nitrogen series of Standard Reference Materials were performed at the National Bureau of Standards by W. D. Dorko and W. P. Schmidt.

The overall direction and coordination oftechnical measurements leading to certification were performed under

the chairmanship of E. E. Hughes and H. L. Rook.

The technical and support aspects involved in the preparation, certification, and issuance of this Standard

Reference Material were coordinated through the Office of Standard Reference Materials by R. Alvarez.

Washington, D.C. 20234 George A. Uriano, Chief

December 3 1 , 1979 Office of Standard Reference Materials

Oxygen concentration:

Cylinder Number: Sample Number:

mole percent

(over)

177
Analysis:

The concentration of oxygen in this Standard Reference Material was ctetermined by comparison with a set of

gravimetric primary standards. The kitercomparisons were performed using both a gas chromatograph

equipped with a thermal conductivity detector and an analyzer sensitive to the paramagnetic properties of

oxygen. The uncertainty shown is based on an estimate of the upper limit of the total uncertainty including the

inaccuracy of the gravimetric primary standards and the imprecision intercomparison of the Standard

Reference Material with the gravinwtric standards. This uncertainty at the 95%confidence level does not exceed

1.0% relative.

This sample is certified only fiK the concentration of oxygen.

A representative number of samples were examined to determine the argon concentration and it is estimated to be mole percent.

Stability;

This SRM is contained in an ahtminum cylinder. TIm stability is considered good and no change in concentratuHi is anticipated. However, the value appearing on this certificate is considered valid for only 2 years from date of purchase. Periodic reanalyses of representative samples from this lot will be performed at NBS, and

if significant changes are observed within the 2 year period, purchasers of the SRM will be notified.

Cylinder:

This SRM is supplied in cylinders at 12.4 MPa (1800 psi) pressure with a delivered volume of 0.88 m^ (31 cubic

feet) at STP. The cylinders conform to DOT specifications and are equipped with CGA-580 valves. The cylinders become the property of the purchaser. However, they may be returned, prepaid, to the National

Bureau of Standards for disposal.

SRM

2657

178
I'.S. I)i*parini«int of ('onimerct*

•luanita M. Krepa SecraUry

Satiiinal Buraav of Sundarda

Kmrat Amhltr. Uiminr

Certificate of ^tml^sis

Standard Reference Material 2658

This Standard Reference Material is intended for use in the calibration of instruments used for combustion

control and respiratory gas analysis. It is not intended as a daily working standard, but rather as a primary

standard to which the concentration of the daily working standards may be related.

The concentration of oxygen is relative to all other constituents of the gas. Each cylinder is individually analyzed and the concentration that appears on this certificate applies to the

cylinder identified by cylinder and sample number.

The original development and evaluation of the oxygen in nitrogen series of Standard Reference Materials were performed at the National Bureau of Standards by W. D. Dorko and W. P. Schmidt.

The overall direction and coordination of technical measurements leading to certification were performed under

the chairmanship of E. E. Hughes and H. L. Rook.

The techniral and support aspects involved in the preparation, certification, and issuance of this Standard

Reference Material were coordinated through the Office of Standard Reference Materials by R. Alvarez.

Oxygen in Nitrogen

(Gas Standard)

Oxygen concentration:

Cylinder Number: Sample Number:

mole percent

Washington, D.C. 20234

December 31, 1979

George A. Uriano, Chief

Office of Standard Reference Materials
/

Analysis:

The concentration of oxygen in this Standard Reference Material was determined by comparison with a set of

gravimetric primary standards. The intercomparisons were performed using both a gas chromatograph

equipped with a thermal conductivity detector and an analyzer sensitive to the paramagnetic properties of

oxygen. The uncertainty shown is based on an estimate of the upper limit of the total uncertainty including the inaccuracy of the gravimetric primary standards and the imprecision of intercomparison of the Standard

Reference Material with the gravimetric standards. This uncertainty at the 95% confidence level does not exceed

1.0% relative.

This sample is certified only for the concentration of oxygen.

A representative number of samples were examined to determine the argon concentration and it is estimated to be mole percent.

Stability:

This SRM is contained in an aluminum cylinder. The stability is considered good and no change in concentration is anticipated. However, the value appearing on this certificate is considered valid for only 2 years from date of purchase. Periodic reanalyses of representative samples from this lot will be performed at NBS, and

if significant changes are observed within the 2 year period, purchasers of the SRM will be notified.

Cylinder:

This SRM is supplied in cylinders at 12.4 MPa (1800 psi) pressure with a delivered volume of 0.88 m^ (31 cubic

feet) at STP. The cylinders conform to DOT specifications and are equipped with CGA-580 valves. The cylinders become the property of the purchaser. However, they may be returned, prepaid, to the National

Bureau of Standards for disposal.

SRM

2658

180