|0 STATES 1ENT OF iwlERCE

NATION

National Bureau of Standards

Library, E-01 Admin. BIdg.

OEC.3 370 NBS TECHNICAL NOTE 545

U.S.

^RTMENT

OF

MMERCE

National

Bureau

of

tandards

Microchemical

Analysis Section:

Summary of Activities

July 1969 to June 1970

mi BUREAU Of ST/WflARDS

UNITED STATES DEPARTMENT OF COMMERCE

Maurice H. Stans, Secretary

(ji S . NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director

NBS TECHNICAL NOTE 545

ISSUED DECEMBER 1970

Nat. Bur. Stand. (U.S.), Tech. Note 545, 126 pages (Dec. 1970) CODEN; NBTNA

Microchemical Analysis Section:

Summary of Activities, July 1969 to June 1970

John K. Taylor, Editor

Microchemical Analysis Section

Analytical Chemistry Division

Institute for Materials Research

National Bureau of Standards

Washington, D.C. 20234

^^^"^

°' ^o, .\

""CAU Of

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C, 20402.

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1
FOREWORD

The Analytical Chemistry Division was established as a

separate division at the National Bureau of Standards on

September 1, 1963^ and became part of the Institute for

Materials Research in the February 1, 1964, reorganization.

It consists at present of nine sections and about 100 technical personnel encompassing some 60 different analytical

competences from activation analysis and atomic absorption to

vacuum fusion and x-ray spectroscopy. These competences, and

in turn the sections which they comprise, are charged with

research at the forefront of analysis as well as awareness of

the practical sample, be it standard reference material or

service analysis. In addition it is their responsibility to

inform others of their efforts.

Formal publication in scientific periodicals is a highly

important output of our laboratories. In addition, however,

it has been our experience that informal, annual summaries of

progress describing efforts of the past year can be very valuable in disseminating information about our programs. A word

is perhaps in order about the philosophy of these yearly

progress reports. In any research program a large amount of

information is obtained and techniques developed which never

find their way into the literature. This includes the

"negative results" which are so disappointing and unspectacular but which can often save others considerable work. Of

importance also are the numerous small items which are often

explored in a few days and which are not important enough to

warrant publication--yet can be of great interest and use to

specialists in a given area. Finally there are the experimental techniques and procedures, the designs and modifications

of equipment, etCo, which often require months to perfect and

yet all too often must be covered in only a line or two of a

journal article.

iii
Thus our progress reports endeavor to present this information which we have struggled to obtain and which we feel

might be of some help to others. Certain areas which it

appears will not be treated fully in regular publications are

considered in some detail here. Other results which are

being written up for publication in the journal literature

are covered in a much more abbreviated form.

At the National Bureau of Standards publications such as

these fit logically into the category of a Technical Note.

In 1970 we plan to issue these summaries for all of our

sections. The following is the sixth annual report on progress of the Microchemical Analysis Section.

W. Wayne Meinke, Chief

Analytical Chemistry Division

IV
PREFACE

This report summarizes the current program and recent

activities of the Microchemical Analysis Section of the

Analytical Chemistry Division. This Section has the primary

mission to contribute to the science and technology of the

analysis of small samples and its program Includes both

fundamental studies to improve the precision, accuracy and

sensitivity of analytical techniques, and developmental

research to provide new and improved methods applicable to

wide areas of materials characterization. As a closely

related activity, the Section provides analytical measurements for various research programs of the Bureau and develops

and characterizes Standard Reference Materials. Research

projects are active in the following competence areas: gas

analysis; polarography ; microscopy; and conventional

microchemical analysis.

A major effort of the Section during the year has been

concerned with the analysis of standard reference materials.

No effort has been spared to characterize these materials to

a high degree of reliability. The use of such materials not

only establishes benchmarks for industrial control but also

provides a sound basis for inter- laboratory comparisons and

for the intercomparison of measurement techniques and methodology. Such materials are regularly used in this laboratory

to verify the accuracy of analytical procedures. They are

referred to by an identification such as SRM l60b, for example.

A catalog containing full descriptions of these materials may

be obtained from the Office of Standard Reference Materials,

National Bureau of Standards, Washington, D. C. 20234.

A number of analytical methods developed or modified for

the analysis of standard reference materials as well as

materials submitted by several NBS research projects are

described briefly. Space limitations have dictated only a

V
brief description of methods in most cases. It is hoped that

such descriptions will be understandable to an experienced

analyst. However, specific details of all work reported here

will be made available to anyone interested in such matters.

Some of the work discussed is a continuation of activities

described in previous reports. Copies of the latter are

available upon request in most cases.

In order to describe procedures, it has been necessary

occasionally to identify commercial materials and equipment

in this report. In no case does such identification imply

recommendation or endorsement by the National Bureau of

Standards, nor does it imply that the material or equipment

is necessarily the best availalbe for the purpose.

John K. Taylor, Chief

Microchemical Analysis Section

VI
TABLE OF CONTENTS

PAGE

1. GAS ANALYSIS 1

A. Introduction 1

B. Standard Reference Materials 2

1. Carbon Monoxide In Air 3 a. Method of Analysis 3

b. Method Evaluation 7 c. Method Modifications 8

2. Sulfur Dioxide Permeation Tubes 9 a. Calibration 10

b. Results 18

c. Storage and Use 22

d. Conclusions 29

3. Organic Materials 30

C. Hlgh-Purlty Gases 31

D. Atmospheric Oxygen Determination 36

E. Research Support Services. . : 36

1. Products from Polymer Degradation Studies. 37

2. Hellum-3 Analysis 38

3. Polywater 39

2. POLAROGRAPHIC ANALYSIS ^1

A. Introduction ^1

B. New Facilities 4l

C. Major Constituent Analysis 4^

1. Copper and Zinc In Metal Foil 44

2. Copper and Nickel In Polls 44

3. Antimony In Lead-base Bearing Metal. ... 45

4. Cadmium In Cadmium Cyclohexanebutyrate

(SRM 1053a) 46

D. Minor Constituent Analysis 46

E. Small Sample Analysis 48

F. Trace Analysis 49

1. Reagent Analysis 49

a. Perchloric Acid 49

b. Nitric Acid and Hydrochloric Acid. . . 51

c. Ammonium Hydroxide 52

2. Environmental Analysis 53

a. Laboratory Air 53

b. Industrial Air 55

3. Lead In Fish Protein Concentrate 56

4. Copper and Zinc In Blood Plasma Processing

Intermediates 56

5. Lead, Bismuth and Tellurium In Special

Steels 57

6. Titanium In Special Steels and Ductile

Irons 59

vll
TABLE OF CONTENTS (CONT'D)

PAGE

7. Nickel, Iron, and Titanium in Glass. ... 6l

3. MICROSCOPIC AND CLASSICAL MICROCHEMICAL ANALYSIS. 70

A. Introduction 70

B. Microchemical Standards 70

1. Urea, SRM 2l4l 70

2. Inter comparison of Microchemical SRMs . . . 73

3. Orchard Leaves, SRM 1571 7^

C. Ultramicrochemical Standards 77

D. Research Material Analysis 78

1. Copper-Nickel and Copper-Palladium Alloys. 78

2. Tungsten-Rhenium Alloys 79

3. Thermochemical Reaction Evaluation .... 80

h. Fluorinated Copolymer Analysis 8l

4. AIR POLLUTANT ANALYSIS 82

A. Nature of the Analytical Problem 82

1. Interpretation 83

2. Sampling 85

3. Physical Analysis 86

4. Metrology 86

5. Chemical Analysis 86

B. State of the Art of Chemical Analysis 88

C. State of the Art of Standard Reference

Materials 89

D. Analytical Methods for Specific Pollutants . . 91

1. Gaseous Pollutants 9^

a. Sulfur Dioxide 9^

b. Hydrogen Sulfide 95

c. Nitrogen Oxides 95

d. Ozone and Oxidants 96

e. Volatile Fluorides and Hydrogen

Fluoride 97

f

.

Carbon Monoxide 98

g. Hydrocarbons 98

h. Other Pollutants 99

i. Other Techniques 99

2. Particulate Pollutants 100

a. Dustfall and Sootfall 100

b. Air-borne Particulates 101

3. Analysis of Single Particles 104

E. Summary 105

5. PERSONNEL AND ACTIVITIES 10 7

A. Personnel Listing 107

B. Publications 107

viii
TABLE OF CONTENTS (CONT'D)

PAGE

C. Talks 107

D. Committee Activities 109

E. Award 110

F. Standard Reference Materials Analyses .... 110

6. REFERENCES 112

LIST OP FIGURES

FIGURE NO. PAGE

1. Double focusing mass spectrometer 2

2. Schematic diagram of apparatus for

determination of carbon monoxide 4

3. Apparatus for determination of carbon

monoxide 5

4. Chamber for maintaining permeation tubes at

constant temperature 11

5. Gravimetric calibration of permeation tubes. 12

6. Predicted, effect of moisture on SOp

permeation rate 15

7. Predicted decrease of vapor pressure of S0„. 16

8. Change in weight of permeation tube after

low-temperature storage 25

9. Correlation of permeation rate with tube

sequence 29

10. Apparatus for absorption of major

constituent in a gas mixture 32

11. Device for concentrating impurities in

carbon dioxide 34

12. Device for minimizing contamination when

sampling from gas cylinder 35

13. Three-unit clean air module 42

14. Single-unit clean air module 43

15. The analytical system for environmental

measurements 84

IX
LIST OP TABLES

TABLE NO. PAGE

1. Reliability of gravimetric calibration ... 20

2. Typical calibration uncertainties 21

3. Storage behavior 22

4. Recovery of rate after removal from low

temperature storage 23

5. Temperature cycling behavior 26

6. Short term temperature effects 28

7. Atmospheric oxygen determination 37

8. Gaseous products from thermally degraded

H-film 38

9. Gas analytical services 4o

10. Analysis of Cu-Ni foils 45

11. Cadmium in SRM 1053a 47

12. Aluminum in ferrosilicon, SRM 59a 48

13. Fe, Cu, Pb J and Cd in perchloric acid. ... 50

14. Total EDTA-complexed metals in perchloric

acid 51

15. Analysis of ammonium hydroxide 52

16. Particulates in laboratory air 53

17. Particulates in clean room air 54

18. Fallout in laboratory and clean room air . . 54

19. Copper and zinc in sodium lactate and

sodium chloride solutions 57

20. Lead and bismuth in special steels 58

21. Tellurium in special steels 59

22. Titanium in ductile iron SRM ll40 60

23. Titanium in SRM 365 and SRM 1265 60

24. Nickel in 500-ppm glass 62

25. Nickel in 1-ppm glass 63

26. Iron and titanium in base glass 64

27. Iron and titanium in 0.02-ppm glass 65

28. Iron and titanium in 50-ppm glass 66

29. Iron in 500-ppm glass 68

X
LIST OF TABLES (CONT'D)

TABLE NO. PAGE

30. Titanium in 500-ppm glass 69

31. Determination of nitrogen In urea SRM 2l4l . 71

32. Homogeneity studies of urea SRM 2l4l .... 72

33. Purity of mlcrochemlcal SRMs 73

34. Nitrogen In orchard leaves, SRM 1571 75

35. Phosphorus In orchard leaves, SRM 1571 ... 76

36. Microscopic Nessler spot test 78

37. Standard reference materials related to

environmental analysis 91

38. Analysis of gaseous pollutants , , 93

39« Particulate characterization^ 93

4o. Expected schedule of appearance of NAPCA

air quality criteria documents 9^

XI
1
MICROCHEMICAL ANALYSIS SECTION: SUMMARY OP ACTIVITIES

JULY 1969 to JUNE 1970

Edited by John K. Taylor

This report describes the research activities

and scientific programs of the Microchemical

Analysis Section of the Analytical Chemistry

Division of the National Bureau of Standards,

Institute for Materials Research during the

period July I969 to June 1970. General

Activities are reviewed in areas of gas analysis

polarography , chemical microscopy, and classical

microchemical analysis. Research activities

described in some detail include: preparation

and analysis of carbon monoxide mixture for

standard reference materials; evaluation of

sulfur dioxide permeation tubes as analytical

standards; polarographic methods for determination

of trace elements in a number of materials;

certification of urea as a microchemical standard.

A chapter reviewing the state-of-the art of

analysis for air pollutants is also included.

Key words: Air pollutant analysis; chemical

analysis; gas analysis; microchemical analysis;

microscopic analysis; polarographic analysis.

1. GAS ANALYSIS

A . Introduction

The Gas Analysis Laboratory is concerned with the development of new or improved methods of gas analysis, mainly by mass

spectrometry. The development of standard reference materials

and their certification and the analysis of a wide variety of

research materials are important functions. Emphasis on both

methodology and SRMs for air pollution analyses has been an

increasing activity over the past several years and especially

so during the past year. A program to develop new concepts for

SRMs for air pollutant analysis and for the evaluation of

analytical methodology has been initiated in cooperation with

the National Air Pollution Control Administration.
The laboratory acquired a new double focusing mass

spectrometer during the year. The extended mass range (12-

3000 amu) and heated probe (up to 400 °C) have greatly

facilitated the rapid analysis of solid and liquid organic

materials of relatively low vapor pressure. In addition, the

moderately high resolution (1 part in 3000 amu) has been of

value in the examination of gases containing molecules

producing ions of the same nominal masses, such as carbon

dioxide and nitrogen. The apparatus is shown in Figure 1.

Figure 1. Double focusing mass spectrometer

B. Standard Reference Materials

A program to develop standard reference materials for

gas analysis was initiated in I966. The first of these,

issued in 1967j consisted of mixtures of carbon dioxide in

nitrogen, (SRM I6OI, SRM l602, SRM l603), at CO levels close

to concentrations of the normal atmosphere. In the following

years, a series of standards was prepared containing oxygen

2
at trace-to-atmospheric concentrations (SRM 1604, SRM 1605,

SRM 1606, SRM 1607, SRM 1608, SRM 1609).

The first gaseous SRMs specifically prepared for air

pollution analysis were issued in I968. These consisted of

a series of methane-in-air standards, (SRM I6IO, SRM I6II,

SRM 1612, and SRM 1613), containing approximately 1000, 100,

10 and 1 ppm methane, respectively. During the past year,

a series of standards containing carbon monoxide in air has

been under development and is nearing completion. In addition,

a program for the development of SRMs for pollution studies,

based on new concepts, has been initiated in cooperation with

the National Air Pollution Control Administration. These

activities are described in the following sections.

1 . Carbon Monoxide in Air

The importance of carbon monoxide as an atmospheric

pollutant has prompted a program to produce a series of

standard reference materials containing known amounts of this

gas. Such SRMs should be useful to calibrate measurement

instruments and procedures utilizing non dispersive infrared

measurements and gas chromatography. The problem of certifying

these materials is twofold -- the accurate measurement of the

CO content, and the question of stability of composition during

extended periods of storage. Some results of the investigation

of both aspects of the problem are described here.

a. Method of Analysis . Past attempts in this

laboratory to determine CO in air by oxidizing the CO to COp,

which is then determined mass spectrometrically have not been

entirely successful. Specifically, this method fails at concentrations of CO similar to those expected in the atmosphere.

Stevens [1] described a method whereby the CO, separated from

oxygen, nitrogen, and hydrocarbons by a chromatographic

technique was reduced with hydrogen on a nickel catalyst to

form methane which was subsequently determined by a flame

ionization technique. It was thought that the above method.
or a variation thereof, would be suitable for determining

CO with sufficient accuracy for certification of standard

reference gases whose CO contents were to range from 100 to

10 ppm.

The nickel catalyst was prepared by evaporation to

dryness of a saturated solution of nlckelous nitrate and

30/40 mesh fire brick. A six inch column of this material

was packed in 3/8 inch stainless steel tubing and was heated

to 500 °C using a tube furnace. The catalyst was activated

prior to use and, periodically during use, by oxidation with

oxygen, followed by reduction with hydrogen. The catalyst

tube was incorporated in the system as shown in Figure 2.

The gas mixing system upstream of the catalyst tube facilitated

the blending of the hydrogen-helium carrier gas in proportions

VENT

A

/--3r

CARRIER

GASES

/

GAS SAMPLING

VALVE NICKEL CATAYST

IN TUBE FURNACE

v-

^

-ujmasji^

MOLECULAR SIEVE

COLUMN IN OVEN

FLAME IONIZATION

DETECTOR

ASCARITE

COLUMN

SAMPLE

Figure 2. Schematic diagram of apparatus for determination

of carbon monoxide.
to give maximum sensitivity. The gas sampling valve admitted

a sample of reproducible volume to the system. A flame

ionization hydrocarbon detector was connected to the outlet

end of the catalyst tube. The apparatus is shown in Figure 3

Figure 3. Apparatus for determination of carbon monoxide

Several mixtures of CO in air and CO in nitrogen ranging

from 13 to 1300 ppm CO were available for testing the method,

3 Briefly, it was found that a helium flow rate of about 7 cm /

minute, a hydrogen flow rate of about 25 cm /minute, and a catalyst temperature of about 500 °C gave maximum response

from 1 cm of a CO mixture injected into the gas stream by

the gas sampling valve. Any COp in the mixture which would

be reduced on the catalyst to CHj,, was removed by placing a

6-in column of Ascarite in the line between the sample gas

cylinder and the gas sampling valve.
Comparison of CO in nitrogen mixtures with COp or CH^^

in nitrogen mixtures of approximately the same concentration

gave results which were reproducible but which were 4-5

percent low. Results with mixtures of CO in air were erratic

due to effects of oxygen upon the catalyst.

Since analyses of CO in air were required, the oxygen

had to be separated from the CO before it passed over the

catalyst. Accordingly, a 6 foot chromatographic column of

1/4 in copper tubing containing 60/80 mesh 5X molecular sieve

was placed in a thermostatically controlled oven in the system

between the catalyst and the gas sampling valve. This provided

adequate separation of both nitrogen and oxygen from CO,

however, methane was not separated. Accordingly, methane had

to be determined in all CO mixtures which might be analyzed

and its response subtracted in order to obtain the actual CO

response.

Variation of helium and hydrogen flow rates and column

and catalyst temperatures established values of these parameters

which gave optimum peak height and separation of the CO peak.

The hydrogen and helium flow rates were 10 and 8 cm /mln,

respectively. The chromatographic column was operated at

85 °C and the catalyst was maintained at 450 °C. A series of

six mixtures of CO in air was compounded in 1.5 ft cylinders

using CO which had been analyzed for impurities and diluent air

which was analyzed specifically for CO and methane. (These

mixtures were to be transferred to smaller cylinders and used

as standard reference materials after analysis.) The concentrations of CO in the mixtures calculated from the pressures

of the component gases were 1017, 534, 304, 102, 45.1, and

10.1 ppm CO, respectively. The response, in terms of signal

versus concentration, was reproducible at any concentration

but was not linear over the observed range. A CO detecting

tube inserted in the exhaust line from the flame ionization

detector showed no evidence of CO, therefore complete con-
version was assumed. Laboratory standards of CO in air were

prepared in small cylinders by gravlmetry to which comparisons

could be made as the final step in the analysis.

b. Method Evaluation . Initially, three

laboratory standards were compounded gravimetrically with CO

concentrations of 1002, 101. 7j and 10.25 ppm CO; respectively.

The use of these laboratory standards whose concentrations were

within about 1 percent of those of the corresponding standard

reference material gases, should have yielded valid calibrations

for the SRMs . Comparisons made between three SRMs and the

corresponding laboratory standard gases gave the results below.

Concentration (measured) Concentration (mixing data)

(ppm CO) (ppm CO)

1021 1017

102.5 102

9.45 10.1

Responses from the other three standard reference gases fell

at approximately the proper position on a response vs. concentration plot. The discrepancy between analytical and mixing

data at the 10 ppm level was at first thought to be due to an

error in the mixing data for the standard reference gas.

Accordingly, another mixture of CO in air was prepared with a

calculated CO content of 10.26 ppm. Comparison of this with

the corresponding laboratory standard indicated a CO concentration of 10.39 ppm.

In order to confirm the CO concentrations of the other

standard reference gases, laboratory standards containing 533.9

and 44.7 Ppm CO, respectively, were prepared gravimetrically.

Comparison of these with the standard reference gases of similar

concentration gave discrepant results which were about 2 percent

low at the 500 ppm level and about 5 percent low at the 50 ppm

level. The standard reference gases had been prepared about

four months before comparison to the freshly prepared laboratory

7
standards. The discrepancies observed suggested an instability

of CO-alr mixtures stored in mild steel cylinders. The

deviation between concentrations from analytical and mixing

data at the 10 ppm CO level could also be explained as due to

loss of CO rather than an error in mixing data.

There is other evidence that CO is not stable when

stored in mild steel cylinders. Some of the standard

reference gas at the 100 ppm CO level was transferred from

its original large cylinder to small mild steel cylinders.

Measurements made two months after the transfer showed the

CO content of the gas in the small cylinders had decreased

by 2 to 3 percent. It was found that heating small cylinders

containing CO in air at the 300 and 100 ppm levels at 60 °C

for 6 days reduced the CO content by about 3 and 7 percent,

respectively. Mixtures of about 50 ppm CO in nitrogen also

showed deterioration when heated in mild steel cylinders at

60 °C for several days.

The apparent loss of CO in mild steel containers is

probably the result of oxidation of CO to COp. Whether

this results from direct oxidation by gaseous oxygen or whether

it occurs indirectly in the presence of iron oxides is not

known. It suggests, however, that a possible solution to the

problem of instability may lie in the use of a less reactive

container such as one constructed of stainless steel.

Accordingly, CO in air mixtures at the 10 and 1000 ppm level

were stored in stainless steel containers at 60 °C for two

weeks without detectable losses of CO. Aging tests of longer

duration are now in progress.

c. Method Modifications . During the course of

the investigation described above, several modifications of

the apparatus were made. A valve with 5 ml sampling loops

was installed which was also able to withstand higher carrier

gas pressure than the original valve. The 6-foot copper

chromatographic column was replaced by a 12-foot, 1/^ in
stainless steel column, to better separate the CO and methane

peaks. The optimum flow rates for hydrogen and helium with

this column were 12 and 8 cm /min, respectively, at a column

temperature of 85 °C.

A series of mixtures of CO in air, ranging in concentration

from 10 to 1000 ppm, was prepared in stainless steel cylinders.

Not only do these mixtures appear to be stable but a linear

response was obtained when they were measured with the modified

apparatus. The non-linearity previously observed with the

copper column could have resulted from oxidation of small

amounts of CO to C0„ by traces of copper oxide present on the

walls, at the 85 °C column operation temperature.

The linear response with the improved apparatus demonstrated

that the efficiency of reduction of carbon monoxide to methane

is independent of concentration of the former. Therefore, it

is possible to verify the efficiency of the reduction reaction

by the use of NBS Standard Reference Materials, Methane-in-Air

,

SRM 1610, SRM 1611, SRM 1612, SRM I613. These measurements

are now in progress and indicate that the efficiency of the

catalytic reduction of CO to methane, under the conditions

described above which are essentially those recommended by

Stevens [1], is essentially 100 percent on the entire concentration range. The two series of SRMs , CO-in-Air and Methanein-Air, will be certified as to their inter-comparability so

that they may be used to verify analytical procedures, such

as the Stevens method [1].

2 . Sulfur Dioxide Permeation Tubes

The use of plastic tubes containing liquid sulfur dioxide,

from which the sulfur dioxide effuses at a rate dependent only

on temperature, has been proposed as a method for producing

known concentration of sulfur dioxide in controlled atmospheres

[2]. Sulfur dioxide is too reactive to allow preparation and

storage of low concentration mixtures in metallic cylinders

without the danger of subsequent changes in the concentration.
Consequently, these devices known as effusion or permeation

tubes offer the most promising method for the production of

known concentrations In the part per billion to part per

million range.

The usefulness of these devices has been established [3]

but their behavior over long periods of time and under conditions similar to those encountered in normal use has not

been fully studied. A study was made, therefore, to follow

a group of "representative" tubes throughout typical circumstances which might be encountered during calibration and use.

a. Calibration . Initially, lots of tubes from

two different producers were Included in the major portion of

the evaluation and later two different lots from the same

suppliers were studied in regard to their calibration only.

The calibration was performed by periodically weighing

the tubes, maintained at a constant temperature, after measured

time Intervals. The rate of permeation is simply the weight

change during this time divided by the time. To obtain

accurate rates, the temperature of the tubes was maintained

constant to about ± 0.01 °C during storage between weighing.

The tubes were stored in a chamber similar to that shown in

Figure 4. Air, previously passed through a column of

activated charcoal, enters the chamber at the bottom after

passing through the heat exchanger tube. The whole vessel is

immersed in a thermostatted bath to the level shown. Measurement of the temperature of the bath and of the interior of

the chamber under actual conditions of storage indicated a difference of less than 0.005 degrees at the fastest flow

rates employed. When large numbers of tubes were contained

in a chamber, the flow rate was at least 2 liters per minute.

With fewer tubes slower rates were employed. The time between

weighings varied from about 20 hours to four or five days.

The time was chosen such that the weight loss was more than

two orders of magnitude greater than the estimated error

Involved In the weighing. Because of the large number of

10
THIN BRASS TUBE

WATER LEVEL

PERFORATED

SPACER

PERMEATION TUBE

IN POSITION

AIR OUTLET

REMOVABLE BRASS CAP

AIR FLOW

WATER LEVEL

PERMEATION TUBE

HOLDER

SEVERAL TURNS

OF COPPER TUBING

PERFORATED DISK

BOTTOM PLATE

AIR INLET

Figure 4. Chamber for maintaining permeation tubes at

constant temperature.

tubes which were to be weighed^ and because the temperature

at the time of weighing often differed from the temperature

of storage, the weighing procedure had to be simplified as

much as possible.

11
A single pan mlcrobalance, readable to 1 yg was used

for all weighings (Fig. 5)- Losses in weight between weighings

Figure 5. Gravimetric calibration of permeation tubes.

were always greater than 1 mg. The method of handling tubes

did not produce an error in terms of accumulated weight of more

than 10 yg for 20 weighings. This quantity is quite small

in terms of the total weight loss of about 30 to 70 mg during

this period. Thus, it was concluded that tubes could be

weighed rapidly without special precautions , thereby reducing

the amount of time that tubes were exposed to temperatures

differing from that of the storage chambers.

While it could be shown that direct handling of the

tubes introduced only a small error in the weighing, it was

further necessary to determine whether the type of direct

12
handling employed In weighing could affect the rate of loss

of sulfur dioxide In a manner that would not easily be detected

during calibration. Such an effect could arise from an

accumulation of grease or dust In the pores of the Teflon.

Surface dirt would probably have little or no effect on the

rate of passage of sulfur dioxide but any foreign matter

which could effectively block the pore spaces In the Teflon

could Influence the effusion rate. In practice. If tubes

are used with reasonable care to prevent contact with dirty

surfaces, the only major source of contamination would be from

the fingers of the person weighing or otherwise handling the

tubes. An accumulation of a significant amount of oil or

grease would require constant mishandling and carelessness

on the part of the operator. Small amounts, however, might

accumulate through normal handling.

A simple, but probably valid experiment was prepared to

determine whether accumulation of grease could be a significant

source of error. The concentration of sulfur dioxide produced

by a single tube in an air stream at a fixed flow rate and

temperature was determined using a flame photometric sulfur

analyzer [^]. The tube was then wiped with a hydrocarbon

grease over 25 percent of its surface area and the concentration

of SOp produced in the air stream was redetermined. Since no

change was observed when 25 percent of the surface was treated,

the entire surface was next treated similarly. The surface

was rubbed vigorously with grease, then the excess was wiped

off. Again, no change in the concentration was observed

indicating that this type of contamination does not affect

the rate of transport of sulfur dioxide through the Teflon.

Another source of error, but one which is much less

easily evaluated, is the effect of the passage of water from

the atmosphere into the sulfur dioxide within the tube.

To evaluate this, several tubes were immersed in distilled

water for periods up to three days. The rate of effusion of

13

m
sulfur dioxide did not appear to be any different after this

treatment when compared instrumentally with the rate before.

However, if the rate of transport through the Teflon for a

particular substance is determined largely by the vapor

pressure of the substance then long-term exposure to an

atmosphere partially saturated with water vapor could have

appreciably greater effect than short-term exposure to liquid

water. This is confirmed to some extent by the observation

that the rate of loss of sulfur dioxide from a tube is

independent of the ratio of liquid to vapor provided that two

phases do exist. The rate of loss of water from tubes

fabricated from similar tubing, that is, tubing of equal

porosity to sulfur dioxide, is about 2 percent of that for

sulfur dioxide. Accordingly, we can make a rough estimate

of the total effect to be expected on exposure of a tube to

ambient atmospheres containing moisture for long periods of

time

.

Sulfur dioxide permeation tubes are not usually allowed

to remain in the atmosphere for long periods of time. They

are ordinarily stored in closed containers with a dessicant

or refrigerated at low temperature. In either case, it is

unlikely that they would be in contact with a high concentration of water vapor for any but a brief period of time during

their useful life. However, tubes may be used for the

production of SOp concentrations using ambient air, although

a pre-drying of the air is recommended. The following considerations have been made to estimate the consequences of

such a practice.

Consider a tube of typical effusion rate and assume that

throughout its useful life it is constantly exposed to an

atmosphere with a relative humidity of 25 percent at 25 °C.

Water vapor will continually pass into the tube countercurrent, so to speak, to the sulfur dioxide. This passage

will continue until the effective water vapor pressure within

the tube is about 6 mm. The solubility of the water in sulfur

14
dioxide is variously reported but it is probably about 2.5

weight percent water [5]- (This pressure would not be reached

in the vapor phase until the sulfur dioxide ^as nearly

saturated with water.) The reduction in vapor pressure, and

presumably the permeation rate, at saturation and where

water would no longer migrate would be about 5 percent of the

rate if water were not present. Because of the difference in

the rate of permeation of the two species it is of interest

to predict at approximately what time in the life of a tube

that this effect would seriously alter the effusion rate.

Figure 6 shows the rate of weight loss in micrograms per day

LUQ

X

o

Q

Ll_ S

_l <

o

~

I-X

CD

LU

ZJZ OC

CD LU

CO

-a:

10

Figure 6,

WEIGHT PERCENT H^O IN SO2

±

100

TIME

150

IN DAYS

200 250

Predicted effect of moisture on SO

permeation rate.

15

2
of sulfur dioxide from a typical tube, the predicted weight

of water gained by the tube during the same time and a superimposed curve of the weight percent of water in the

liquid sulfur dioxide. Figure 7 is a representation of the

decrease in vapor pressure in a system, sulfur dioxide-water,

where the sulfur dioxide is less than saturated with water.

This was derived from the vapor pressure data of Maass and

Maass [6] and the solubility values of Daisaboro Murakumi

and Niichiro Tokura [7]. The composition of the vapor as

calculated from Raoult's law is uncertain because water is

probably present in the sulfur dioxide as the hydrate of

sulfurous acid, HpSO^ 6HpO [8]. At a weight concentration

of water of 2.49 percent, the system is saturated and a second water-rich phase will separate. Up to this point.

LUQ

X

o

Q

(T

ZD

Li_ _l

LO

Li. O

LU

CC

ZD

(/)

C/) LU

QC

Cl

QCO

CL

292 \

1 1 1 1 1

288 - ^^/o^^2

284

280

-

^\5_

276 SATURATION-H

0.5 1.0 1.5 2.0 2.5

WATER IN SULFUR DIOXIDE WEIGHT PERCENT

Figure 7. Predicted decrease of vapor pressure of SOp

16
the pressure of water vapor should not exceed about 2 mm and

the total pressure can be considered as almost entirely due

to sulfur dioxide. When the amount of water in the system

increases, the vapor pressure of water will Increase and will

continue to increase until the absolute pressure of water

vapor equals the pressure of water vapor in the ambient

atmosphere. At 25 °C and 25 percent relative humidity, this

will be about 6 mm. The system will never contain more than

a small amount of water, whether it is saturated or not, and

the vapor pressure of SOp at saturation, 277.5 mm, represents

the minimum vapor pressure of SO and; consequently, the minimum

effusion. If the assumption that the effusion rate is

proportional to the pressure of the effusing substance is

valid; then the error due to absorbed water will never exceed

5 percent and most likely, will be less than this during most

of the life of a tube. If tubes are continually exposed to air

saturated with water vapor at room temperature, about 25 mm

water vapor pressure, the rate of absorption of water will be

increased and a reduction of the effusion rate of 5 percent of

the original value will occur sooner than at 25 percent relative

humidity, but no matter what the rate of absorption the minimum

effusion rate should remain the same during the life of a tube

while a sulfur dioxide phase still exists.

The simplest way to avoid this error is to minimize exposure of tubes to atmospheres containing large quantities of water

vapor. Storage at low temperature, even at 100 percent relative

humidity, would reduce the transfer of water as would volume.

During these studies, several tubes handled with reasonable care

have reached the point where no liquid phase was present. As

long as even a discernible amount of liquid was present, the

rate of effusion of sulfur dioxide remained the same as when the

tube was first measured. An example is the results obtained for

a single tube where a column of sulfur dioxide of 2 mm remained

as compared with an original of more than 90 mm. The liquid was

yellow in color, consisted of a single liquid phase, and con17
tained a small residue of particles resembling flakes of rust. | The effusion rate at 25 °C determined while the tube contained

more than 50 percent of liquid was 2.766 micrograms per minute.

The rate determined v/ith only 2 mm, or less than 3 percent of

the original sulfur dioxide, was 2.76^ micrograms per minute.

The difference is considerably less than the approximate 1 per- \ cent uncertainty of measurement of the original rate and is con-- sidered to be insignificant. Accordingly, it is concluded that

with only moderate care the effusion rate will not be seriously

affected by exposure to the ambient atmosphere.

Another source of error which cannot be easily evaluated

concerns the purity of the sulfur dioxide within the tube.

An implicit assumption of the gravimetric calibration is that

the contents of the tubes are pure and that the weight loss

represents only the loss of sulfur dioxide. Measurements of

several tubes identical in external dimensions but differing

in permeation rate by 10 percent, using the Instrumental

technique previously mentioned, showed good correlation between

the quantity of sulfur and the gravimetrically observed rates.

These same tubes and one having an intermediate rate were

sealed in evacuated glass ampoules and were allowed to effuse

for a period of several days. The gases which accumulated

were then examined mass spectrometrically . All consisted

only of sulfur dioxide with no evidence whatever of any other

species except small quantities of air in amounts normally

observed as "background."

It is conceivable that the situation could arise where

impure sulfur dioxide could be used in the fabrication of a

lot of tubes. However, the quality control of commercial

sulfur dioxide is believed to be good so that such an occurrence

is unlikely.

b. Results . The effusion rates of 160 tubes were

determined gravimetrically during this study. The tubes

were produced by two different manufacturers presumably from

different supplies of tubing and had slightly different design

18
characteristics. Tubes from one source, hereafter referred to

as "A" were in general of the same wall thickness but of

different lengths. Tubes from the other source, "B," were all

of the same length but of different wall thickness. It was

observed early in the study that tubes from source "B" were

in general more erratic in behavior than those from source "A."

This may be due in part to the use of a thicker-walled Teflon

tubing but as yet the cause is not entirely identified. In

the final calculation, some of the tubes from "B" were not

included because their behavior was not considered typical

in terms of the intent of the study.

All of the gravimetric data for the measurements at

various temperatures was computer processed. The equation

log R = mT + b

where R is the rate in micrograms per minute and T is the

temperature in degrees absolute, was found to give a straight

line in the temperature interval between 20 and 30 °C. The

data were fitted by a method of least squares and the constants

m and b as well as the error associated with them were calculated. The rates at 20, 25 and 30 °C were then calculated as

was the uncertainty in the rate at each temperature.

The voluminous results are not reproduced here but

several points of interest were noted and will be expanded upon,

The calibration uncertainty associated with two different

groups of tubes was found to be essentially the same even

though one was based upon as many as 51 useable weighings while

the other was based on only 7. Although the second calibration

was done at a later date and involved minor refinements of

techniques it indicates that an adequate degree of accuracy

in determination of the rate can be achieved in a relatively

short period of time without loss of a significant amount

of material from the tube. Table 1 lists the rate at 25 °C

for several tubes together with the uncertainty (expressed as

19
the 95 percent confidence limit of the average) and the number

of useable weighings. A useable weighing is simply a weight

obtained after the tube has reached equilibrium at a particular

temperature. Since hysteresis does occur, weights obtained

shortly after a temperature change probably do not reflect the

equilibrium rate of weight loss. No significant difference in

the uncertainty appears between the two groups. It can be

concluded that an uncertainty of about ± 2 percent would

constitute a conservative limit to be placed on values obtained

by the gravimetric technique.

Table 1. Reliability of gravimetric calibration.

Rate in Relative error.

Tube micrograms No. of 95$^ confidence

number per minute

1.321

determinations

7

limit

4819 1.92

6231 2.52 9 1.48

6229 2.57 9 1.55

6235 2.67 9 1.15

217 1.35 48 2.09

137 2.67 45 1.19

157 2.71 44 1.60

128 2.92 48 1.20

Another significant point is the larger uncertainty

associated with tubes from source "B." Reproduced in

Table 2 are the errors associated with 20 tubes selected at

random from batch "A" and "B." The average as well as most

individual results show a significant difference.

The tubes from source "B" differ little from "A" except

in external diameter and in wall thickness. The larger wall

thickness, as previously mentioned, is believed to be the

source of this larger error. A theoretical treatment of the

mechanism of diffusion through a porous membrane would perhaps

20
confirm that a greater uncertainty would be experienced when

thicker membranes are used. For the present, however, let

us examine the process In an empirical manner simply to allow

some speculation as to what might be occurring. It was observed

when these tubes were first Investigated that permeation rates

Table 2. Typical calibration uncertainties.

Tube

number Source "A" Source "B"

1 1.56 2.72

2 1.59 ^.^9

3 2.24 5.83

4 2.92 3.02

5 1.66 3.10

6 1.80 5.22

7 0.87 2.54

8 1.23 3.75

9 2.10 3.72

10 1.89 3.00

Average: I.78 3.74

of tubes from "A" were more or less Independent of the rate at

which air passed over them. Tubes In an exposure chamber to

which the air supply was Inadvertently reduced or shut off

were found to have about the same permeation rate as when a moderate stream of air was flowing. Tubes from "B," however,

exhibited generally different behavior In that very erratic

permeation rates were observed when the air flow through the

chamber was reduced. The results obtained on successive days

for one tube from each batch exposed at low or zero air flow

rates are shown In Table 3. (The average for the tube from

"A" was the same In an adequate flow of air.) The average

permeation rate for the tube from "B" determined while an

adequate flow of air was maintained was found to be 1.37 mg/mln

21
or about the same as the average of the erratic set. This

suggests a conservation of sulfur dioxide, and that in spite

of the erratic loss from the outer surface, the mass flow of

sulfur dioxide across the inner surface remains constant. A

thicker wall must of necessity have a lower concentration

gradient expecially near the outer surface. Perhaps the slope

of the gradient for a thick wall is so low that variation in

sulfur dioxide concentration in the boundary layer caused by

variation in the rate of removal of sulfur dioxide can cause

a temporary reduction and even reversal of the rate of loss

from the surface.

Table 3. Storage behavior.

Determination Rate in micrograms per minute

No. "A" "B"

1 0.96 2.18

2 0.97 1.20

3 , 0.94 1.31

4 0.94 1.46

5 0.96 1.22

6 0.96 .54

7 1.61

8 0.96 1.35

c. Storage and Use . A tube which originally

contains about a gram of sulfur dioxide and which loses sulfur

dioxide at a rate of 2 yg per minute at room temperature will

have a useful life of less than one year. Therefore, if

permeation tubes are to have maximum service life it is

necessary to reduce the effusion rates when the tubes are not

in use. A simple procedure is storage at low temperature with

removal only when needed for calibration purposes. It has been

observed, however, that there is considerable lag in response

to temperature changes. It is extremely difficult to observe

22

1
this hysteresis quantitatively over a short period of time.

Three tubes which had been stored at temperatures between

-20 and -30 °C were compared with a tube of known rate at

various times after removal from the low temperature. The

results are shown in Table 4. The rates are the observed

rate as a percentage of the final rate measured 72 hours

later. The readings at 24, 48 and 72 hours are considered

constant within the limits of the method. The readings after

3 and 6 hours definitely indicate that equilibrium has not

been reestablished.

Table 4. Recovery of rate after removal from

low temperature storage.

Time after

removal/hours

Tub

Rate,

e number

1

v_ercent

Tube

of final

number

2

value

Tube number

3

3 92 92 91

6 92 92 91

24

48

98

100

99

100

100

100

Because of the basic difficulty in following small

changes in effusion rate with the instrumental technique an

attempt was made to determine the rate of change of the rate

after storage at low temperature by a gravimetric technique.

Several tubes were removed from low temperature storage

(<-30 °C) and were weighed as often as practical during

a 24 hour period after removal. The rates at the various

times were then calculated. The results were quite erratic

and effusion rates calculated from the weight losses were

inconsistent. The probable cause of the inconsistency is the

error associated with the determination of effusion rates

using short term weight losses. Accordingly, a single tube

was removed from low temperature storage and suspended from

the balance. The weight of the tube was then determined over

a period of 36 hours without removal from the balance. The

23
observed temperature In the balance case fluctuated about

± 0.1 degrees but was not significantly different from the

average at any time during the 36 hours. Experience has shown

that the magnitude of the long term drift of the balance zero

would have no significant effect on the overall rates described

below. Weights were determined at intervals varying from 10

minutes to 2 hours except during the overnight period. Two

different rates were observed. These are shown in figure 8.

The slope of the two Indicated portions of the curve were

computed and their intercept was calculated. The results

indicate that the intercept would have occurred 886 minutes

after removal from cold storage. The effusion rate before the

intercept is only 86 percent of the true rate observed after

equilibrium had finally been reached.

The above results confirm the earlier and less exact

work using the flame photometric technique. However, the

question as to the minimum waiting period after removal from

storage is still unanswered. If the transition from one rate

to the other was abrupt the minimum time would be the time

of intercept. If the intercept is only theoretical and the

transition is in fact gradual then the minimum waiting period

would be greater than the Intercept would indicate. Accordingly,

a second tube was removed from low temperature and the weight

loss was recorded in the same manner. Again, different slopes

were observed over a period of 32 hours. The calculated

intercept for this tube was 99 3 minutes. However, a change in

slope of the line representing the lower rate began to occur

after approximately 700 minutes. The slope, in the region

from 700 through 800 was about 2.44 yg/min determined graphically. This value is intermediate between the early rate and the

final rate. If a symetrical transition is assumed then the

minimum waiting period would be about 130 minutes. Since it

is known that 24 hours (l440 minutes) is sufficient to

reestablish the time rate it is recommended that this latter

value be used as a safe minimum waiting period.

24
en<

a:

UJ

003

I-X

iij

4.429000

28000

27000

26000

25000

4.424000

RATE I

1 INTERCEPT

\

\

\

\

500 1000

TIME IN MINUTES

RATE 2

1500 2000

Figure 8. Change in weight of permeation tube after

low-temperature storage.

Teflon is known to experience a double phase transition

in the region between and 4o °C with the transitions centered

around 20 and 30 °C [9]. Equilibrium is not rapidly reestablished and the experimental data indicate that temperature

changes of one degree per hour are not sufficiently slow to

25
maintain equilibrium. Considerable periods of time may be

required to reestablish the steady state specific volume of

Teflon depending on the rate of change of temperature and the

magnitude of the change. It is not known whether these phase

changes will have a major effect on the effusion rate but the

effect is highly suspect as a reason for the hysteresis

observed when temperature cycling of the tubes occurs. It was

consistently observed when determining the rate of effusion

of the tube that the first rate determined after a change of

temperature usually differed from the succeeding rates and

the difference was always in the direction of the previous

temperature. As an illustration, the results obtained with a single tube are shown in Table 5. The behavior for this

tube is quite typical for other tubes in the same set treated

in the same manner.

The values are the condensed results in the order in

which the temperature was changed. The initial reading

appears at the indicated temperature and the final (approximately!

the average) rate obtained after a series of measurements at

the indicated temperature appears immediately below.

Table 5. Temperature cycling behavior.

Temperature, °C

26.3

29.4

29.4

20.0

20.0

31.0

31.0

25.5

25.5

30.4

30.4

final)

initial

)

final)

initial

final)

initial)

final)

initial

)

final)

Initial)

final)

Measured rate, yg/min

3.09

3.80

3.86

2.23

1.85

2.85

4.47

4.89

2.86

3.21

4.23

26
The only change not characterized by a difference from

the final value is the transition from 31.0 to 25.5 °C.

This, however, occurred over a longer period of time and

equilibrium had probably been well established before the

first weighing was made.

The period of time represented by the interval between

temperature changes was at least one day. The first rate at

the new temperature was always based on a rate determined

after the temperature change occurred and was not based on a

weight loss measured between different temperatures.

The calibration procedure requires equilibration at the

temperature of calibration for long periods of time. The

I time is presumably more than sufficient to reestablish

I

I equilibrium in the Teflon. However, in use the tubes may be

j used at different temperatures for short periods of time in

j order to produce different concentrations of sulfur dioxide

in a gas stream. If, for example, a tube normally stored

at room temperatures is used for a short time at 30 °C, what

periods of time are involved in reequilibrating the tube?

Several tubes were stored at 25 °C and their rates relative

to a reference were determined using the flame photometric

instrument. They were then stored at 31 °C for periods

varying from 135 to 290 minutes. The tubes were then immediately cooled to 25 °C and the rate of loss of sulfur dioxide

was periodically determined until the rate returned to the

value previously obtained at 25 °C. The results are shown in

Table 6. The length of storage at 31 °C is shown. The rate

is indicated as the percent of the rate originally observed

before storage at 31 °C.

This experiment was repeated several times and from these

results and other experiments it appears advisable that the

tubes should be used at a single fixed temperature. If

different temperatures are used, then sufficient time should

be allowed for the reestablishment of equilibrium. The time

27
will depend to a large extent on the length of time a tube

has remained at a temperature differing from that to be used.

In general, tubes stored or used at one temperature for

periods greater than one day should be allowed to equilibrate

at any new temperature for at least 24 hours. Tubes cycled

over short temperature ranges in short periods of time can

probably be used at the starting temperature with little

change in accuracy of the rate. If the temperature is changed

permanently, the rate at the second temperature cannot be

expected to reflect the true rate at that temperature within

a period of time less than 24 hours.

Table 6, Short term temperature effects.

Tube number Time at 31 °C Time at 25 °C Percent of 2 5° rate

171

157

146

135 min. 10 102

25 101

43 101

67 101

87 100

230 min. 2 107

7 101

11 100

290 min. 11 101

40 101

45 101

65 100

Another interesting detail gleaned from the tabulated

results is shown in Figure 9. The rates are plotted with

respect to tube number in ascending order. This is the only

set of tubes in which it was known that the tubes were prepared

from a continuous length of tubing and where the tube num.bers

indicate the position of the tube relative to the others.

It is obvious from the regular variations that a significant

difference in permeation rate is associated with different

sections of the stock tubing from which the tubes were

prepared.

28
TUBE SEQUENCE FROM STOCK

Figure 9. Correlation of permeation rate with tube

sequence

d. Conclusions . Sulfur dioxide permeation tubes

provide a practical means of producing gases of accurately

known concentration of this substance for calibration of

air pollution measurements o The disadvantages of stringent

requirements for accurate temperature control and measurement

as well as an accurate knowledge of flow rate of ambient air

are offset by the Inherent reliability of the gaseous mixtures

that can be so produced. Accordingly, the tubes seem to be

superior to any other means of producing a gas of known S0„

content

The studies described above have demonstrated the

feasibility of certification of permeation tubes as SRMs for

air pollution analysis and a program for this purpose has

been Initiated. Plans call for certification of commercially

29
produced tubes on the basis of Individual calibration. The

gravimetric procedure already described will be used. In

addition, tubes selected from each lot will be checked by

coulometric calibration [3] and also by measurements with

the flame photometric detector. Mass spectrometric measurements will also be made of the effused gas to verify its

composition. A certificate giving the measured permeation

rates of each tube at several temperatures will be furnished.

This SRM is expected to be available for distribution in

latter part of 1970.

In connection with this certification program, NBS will i maintain a group of permeation tubes as NBS Laboratory

Standards. These tubes will be periodically recalibrated and

intercompared. Tubes certified for public use as SRMs will

be compared with the NBS Laboratory Standards as part of

the calibration procedure already described. i The NBS SRM permeation tubes will provide a means not

only to calibrate analtical instrumentation but will also

make possible the interlaboratory comparison of techniques

and methodology. Furthermore, their use as laboratory

controls would virtually eliminate measurement uncertainty

as a factor in questions concerning ambient air quality.

3 . Organic Materials

A number of organic standard reference materials have

been examined in the past year. While not gaseous materials

under ordinary conditions, these standards were amenable to

investigation by mass spectrometry and hence were analyzed

by this laboratory. Much of this work was concerned with the

examination of material concerned with the clinical standards

programc Bilirubin, cholesterol, urea, and various derivatives

of substances related to these materials were examined. The

entire NBS line of microchemical standards was also examined,

since they have been shelf items for several years and their

stability needed verification (see Section 3oB.2 of this report)o

30
C . Hlgh-Purlty Gases

A frequent problem In gas analysis Is the determination

of the purity of commercially produced gases. Probably the

most convenient and potentially most Informative Instrumental

technique Is mass spectrometry. In general, samples can be

analyzed with little difficulty and both the nature and

quantity of many Impurities can be readily determined. This

Is most often true for the less commonly encountered gases,

and unfortunately. Is least true for the common gases, oxygen

and carbon dioxide. The major difficulty In the assay of

oxygen Is that sample pressure which would allow a simple and

direct analysis of gases such as nitrogen, argon, helium and

carbon monoxide are prohibitively high In the case of oxygen.

Not only are compounds foreign to the sample formed In the

Ionization region at high pressures of oxygen but the oxygen

Itself has a very deleterious effect on the electron emitting

filament of the Instrument. In the case of carbon dioxide,

the major Impurity Is nitrogen which has a mass approximately

equal to that of the major fragment Ion of carbon dioxide.

Because of the great difference In concentration between the

Ion produced by the carbon dioxide and nitrogen high resolution

mass spectrometry offers little analytical aid.

In the case of both these gases, a reagent Is available

which "selectively" removes the major constituent enabling a direct examination of the Impurity. Oxygen can be completely

removed with either phosphorous or a sodlum-potasslum alloy

without removing nitrogen or the rare gases which are the

normal Impurities In reagent grade oxygen. Carbon dioxide,

of course, can be removed with "Ascarlte."

Two simple devices were constructed to facilitate these

analyseSo The first, shown In Figure 10, Is designed for

oxygen. The bulb marked "A" Is filled with the sample and

Is then connected at "A." The bulb marked "B" contains the

reagent o Preparation and use of the reagent, either phosphorous or sodlum-potasslum alloy Is described In detail

31
elsewhere [10]. The entire apparatus can be evacuated through

"C" which is connected directly to the inlet system of the

mass spectrometer. The sample is bled slowly into the reagent

flask until the reaction is complete and a stable pressure

minimum is reached as indicated by the manometer. If sodiumpotassium alloy is used, the sample may then be introduced

directly into the inlet system and a mass spectrum is obtained,

Figure 10. Apparatus for absorption of major

constituent in a gas mixture.

When phosphorous is used, it is desirable to cool the bulb with

dry ice after reaction to reduce the vapor pressure of phosphorous below the level where it interferes with the analysis.

The Impurities can then be expanded into the inlet system.

Some precautions should be observed by the careful analyst

if reliable results are to be obtained. The metal alloy reacts

32
readily with carbon dioxide and this gas even though present

In the oxygen will not be observed In the residue. Too rapid

a reaction may Introduce spurious species through reaction

with melted stopcock grease and possibly between the constituents of the sample. To minimize these problems, bulbs can be

cooled either with a stream of air or In an Ice bath. And

lastly, both reagents are quite reactive and should be handled

cautiously.

Experience has shown that more than 99 percent of the

sample reacts In a reasonable length of time leaving the

Impurities together with less than 1 percent of the oxygen In

the sample flask. The volume of the reaction flask and the

Inlet system can be readily determined allowing a simple

calculation to be made of the quantities of the various

Impurities originally present In the oxygen. As an example

the following was found In a sample of hlgh-purlty oxygen:

Nitrogen 133 parts per million by volume . Carbon Dioxide 35 parts per million by volume

Argon 8 parts per million by volume

Krypton 16 parts per million by volume

Xenon 3 parts per million by volume

The sample was analyzed using each reagent In order to

avoid the possibility of overlooking an Impurity which might

react with one but not the other reagent. The pressure and

Identification of the rare gases Is both plausible and certain

as this oxygen was prepared by fractional distillation of air.

The apparatus for carbon dioxide shown In Figure 11 Is

simply a modification of a type of reagent tube long used In

the field of gas analysis [11]. The sample flask "A" Is

filled with carbon dioxide from the cylinder to be analyzed.

The flask Is then attached at "A" and the entire apparatus

Is evacuated to the stopcock of the flask. The appropriate

stopcocks are then opened or closed and the sample Is allowed

33
to pass slowly through the reagent column and then directly

Into the inlet system of the mass spectrometer. The magnesium

perchlorate column is necessary to remove excessive water

desorbed from the Ascarite. It has been observed that when

using this technique, removal of the carbon dioxide may be

incomplete if the sample is passed too rapidly through the

reagent. This does not pose a serious problem, however,

because it is only necessary to lower the carbon dioxide

pressure to a value where the fragment ions are sufficiently

reduced to allow a recognition and calculation of contributions

from other species. Again, as with the oxygen, a determination

of the ratio of the volume of the flask to that of the inlet

system allows a simple calculation of the quantity of impurity.

ASCARITE MAGNESIUM

PERCHLORATE

ZP

TO MASS

SPECTROMETER

INLET

CAP MADE FROM

OUTER GROUND

JOINT

Figure 11. Device for concentrating impurities in

carbon dioxide.

A simple device for transferring samples from the cylinder

to the sample flask is shown in Figure 12. This device has

been in use for several years and was inherited by one of the

authors (E. E. Hughes) from predecessors in the former Gas

Chemistry Section of the National Bureau of Standards. We have

failed to note such an apparatus in the literature. We do not

wish to claim any credit for its design but wish to pass it

along as a useful device for transferring samples from cylinders

34
STAINLESS STEEL

BLOCK

STAINLESS STEEL

STANDARD PAPER

JOINTS

HOSE NIPPLE

B

1/4 NPT

MERCURY

RESEVOIR

Figure 12. Device for minimizing contamination when

sampling from gas cylinder.

with little or no danger of contamination from the atmosphere.

When analyzing gases such as these described here, this latter

source of contamination Is of great Importance and constitutes

the single most significant source of error.

The transfer apparatus Is connected directly to a control

valve, not a regulator, attached to the cylinder. The previously

evacuated sample flask Is attached to the stainless steel

35
ground joint (A) . A moderate vacuum is applied through the

valve (B). The cylinder valve B is then closed and the

cylinder control valve is opened slightly to allow gas to flow

into the system. When the pressure reaches atmospheric as

shown by escape of gas through the mercury reservoir, the sample

flask may be opened and the pressure adjusted to one atmosphere.

A series of evacuations and flushings prior to sampling gives

the analyst a degree of confidence in the integrity of the

sample that is found in few other techniques. The fact that

the system need never be below a pressure of one atmosphere

after the initial filling and flushing eliminates many sources

of error such as small leaks in joints and around valve stems.

D

.

Atmospheric Oxygen Determination

A systematic determination of atmospheric oxygen has been

described in previous reports [12] [13]. The results have

been consolidated and have been published together with a discussion of their significance in relation to earlier investigations [l4]. During the past year, several additional

samples were obtained in a rural area in Maryland. The oxygen

content of these samples was determined by comparison with

a standard reference material (SRM l609j Oxygen in Nitrogen).

The results are shown in Table 7.

The average agrees with that of the previous survey.

Samples of a similar nature will be analyzed periodically in

the future to establish a "benchmark" value for the present

oxygen content of the atmosphere

„

E. Research Support Services - This laboratory analyzes a wide variety of gaseous

samples related to the research programs of other NBS divisions as well as samples for other government laboratories.

Carefully compounded and analyzed gaseous mixtures are also

prepared on occasion. The analytical services mainly utilize

mass spectrometry but other techniques, including gas

chromatography and electrochemistry are used as requiredo

36
Table 7. Atmospheric oxygen determination.

Sample No. Oxygen content in mole %

1 20.9^^

2 20.9^9

3 20.946

4 20.9^6

5 20.9^7

6 20.944

7 20.949

8 20.945

9 20.946

10 20.947

Average 20.946

Gravimetric procedures are used to compound gaseous mixtures,

provided the overall mass, including container, does not

exceed 10 kgo Otherwise, pressure measurements with carefully

calibrated gauges are used to compound mixtures.

Gas analysis ranges in complexity from simple identification of specified substances to the quantitative determinations of trace or residual components in highly complex

mixtures, such as reaction products. Many of these are done

on a continuing basis and are scheduled to coordinate with

experimental work in progress in other laboratories. Table 9

lists the more significant analyses during the past year.

Several of the more interesting items are below.

1. Products from Polymer Degradation Studies

This laboratory cooperates with the NBS Polymer Division

in the analysis of the gaseous and liquid products of thermally

degraded polymers. A total of 18 samples were received over

a six month periodo The samples were contained in glass

37
ampoules and mass spectrometry was used to determine the total

pressure as well as to Identify and/or quantitatively determine

the gaseous products.

The determination of thermal degradation products of

polyimides is given as an example of this kind of analysis.

Four 50 ml ampoules, designated "A," "B," "A liq," and "B liq"

were received. The gas pressure in both "A" and "B" was 2 mm

Hg. The pressure in the remaining two ampoules was not of

interest so was not measured. The compositions of these

samples are given in Table 8.

Table 8. Gaseous products from thermally degraded H-film.

Composition in mole percent

Component "A"

1.5

"B" "A liq"

lo3

"B liq"

^2 7.0 1.4

CO^ 1.2 1.4 95.2 90.8

«2 13.5 17.5

°2

0.7 4.1

CO 83.1 74.1

Benzene 0.9 0.9

Xylenes Trace

HCN 2.5 2.8

Other samples contained such components as N, N-dimethyl

acetamide, benzonitrile , phenol, aniline, and the f luorocarbons

CpF^ and C^P^. Most contained water and air in various amounts.

2 . Helium-3 Analysis

In a continuing program in cooperation with the Monsanto

Research Corporation, this laboratory periodically analyzes

a series of He-3 samples for He-4 and other impurities. The

He-3 samples have been taken from bulk lots of He-3 which are

produced for use in gas thermometry. The analysis performed

by this laboratory constitutes NBS certification of the He-4

content of the He-3.

38
The He-4 content of the samples ranges from about 0.007

to 0.01 mole percent. In order to analyze for He-'^ at this

low concentration J "high pressure mass spectrometry" is

utilized, i.e., the sample pressure is about 10 mm as opposed

to pressures of 0.01 to . 2 mm for normal operation. High

gas pressures increase the signal of components present in

small quantities, but are only feasible with gases which will

not adversely affect the spectrometer or complicate the

interpretation of the spectrum. The high pressure technique

results in He-4 analyses with a precision of about ± 0.0005

mole percent at the above mentioned He-4 levels. During the

year, a total of 10 samples of He-3 were analyzed for He-4,

and 2 samples v/ere analyzed for trace impurities such as water,

nitrogen, oxygen, argon, and carbon dioxide. These impurities

range from a few hundredths to a ten-thousandth of a mole

percent which is about the limit of detection by this technique.

3 . Polywater

.

Attempts have been made to observe significant ions in

the mass spectral pattern of several samples of "polywater"

and related "poly-alcohols." Samples prepared by Dr. Warren

Grant of the NBS Polymer Division were submitted either in

the capillaries in which the material was prepared or on the

surface of a diamond plate, after removal from the capillaries.

Samples were analyzed with a double focusing mass spectrometer.

A heated probe was used to insert the samples as close to the

ionization region as possible.

Many problems were encountered which precluded definitive

results [15]. The primary problem arose from the small

quantities of material which were available with a resulting

difficulty in distinguishing spectra arising from the sample

from spectra generated withing the instrument. Accordingly,

quantitative interpretation of the spectra was not possible

and no further work is contemplated until larger samples are

available.

39
Table 9. Gas analytical services.

A. Mass Spectrometrlc Analysis

No. of

Material s amp 1 e s Sample size Determined

Gas Mixture 1 cylinder H^, CO

Nitrogen 1 cylinder Impurities

Air 1 cylinder Hp, CO

Hellum-3

Ketene

CF0CFCH2

02

Reaction Products

Reaction Products 1 glass ampoule HpO, methyl

styrene

1 1 cc metal He-^

container

3 large glass CO25 acetic acid,

tubes HpO, O2

5 glass container CF0CF2CH2J

N 50 cc Impurities

2 glass container CF^,

1 glass ampoule deutero-a-methylstyrene HpO

Helium from reactor 2 11 STP He, D2, H2O, N2,

02, Ar, CO2

Reaction Products 8 glass ampoules H2:CHij ratio, O2

Reaction Products 2 glass ampoules H2a CH4j CO, N2a

HpO, CO2, O2

Reaction Products 8 glass ampoules H2j N2J CO, CHij,

H2O, CO2, O2,

benzene, acetone

B. Compounding of Gas Mixtures

Mixture Concentration of minor component

CO In Np 109 ppm

COp In Np 27.3 ppm

COp In Np 7.84 ppm

CpH^ In Np 0.4 ppm

CpHp In Np 0.09 ppm

CHk In air 511 ppm

(E. E. Hughes, J. M. Ives, and G. Silver)

40
2. POLAROGRAPHIC ANALYSIS

A. Introduction

The activities of the Polarographic Laboratory have been

concerned largely with the analysis of standard reference

materials and with samples of research materials connected

with the programs of other NBS sections as well as several

other government agencies. Determinations of major constituents have been an important part of the program; however,

the major emphasis has been on trace analysis. As the end of

the reporting year approached, considerable effort was being

devoted to environmental analysis, especially the determination

of certain metallic elements in particulate samples. All of

this was accompanied by a considerable amount of method

development activity.

A recapitulation of the year's work shows about 15 major

reports concerned with standard reference material analysis

and about 10 reports on the analysis of research materials.

The more significant aspects of these activities are summarized

in the following sections of this chapter.

B. New Facilities

Contamination introduced from particulate material in the

laboratory air is a potential danger in trace analysis . Since

many chemical operations need to be carried out over an extended

period of time, exposure to even relatively clean air can

significantly increase the analytical blank in many instances.

To improve this situation, an assembly of clean air hoods has

been installed in the chemical laboratory. This consists of

four modular class-100 laminar flow clean hoods to provide 8

square feet of clean working area and an additional 8 square

feet of clean air fume hoods

.

Modular units, each having a working area of two feet

by two feet, provide filtered air in a downward laminar flow,

at rates adjustable from 50 to 150 linear feet per minute.

The pre-filter consists of washable, reusable polyurethane

41
foam and the final filter is an HEPA-absolute type with aluminurr!

separators, with reported efficiency of 99.97 percent in the

removal of particles with diameters of 0.3 micrometers or

greater. The side panels are of plexiglass and the cabinet of

steel, covered with epoxy paint.

Two of these modules, together with a modified module,

constitute the clean area shown in Figure 13. The two modules

in the foreground provide 8 square feet of working space to

perform chemical operations normally done in the open laboratory as well as a storage area for processed material. The

third module has been modified to provide a clean fume hood.

Figure 13. Three-unit clean air module.

42
It is fitted with a perforated Teflon base and placed upon a fiberglass plenum which can be vented to the regular laboratory

exhaust duct.

A different arrangement which also serves as a clean fume

hood is shown in Figure 14. The vertical laminar flow hood

is placed on a table in front of the conventional laboratory

hood. The air from the clean unit is vented directly from its

open front into the face of the laboratory hood.

Figure l4. Single-unit clean air module

The equipment described above has been in use for a period

of about six months and is believed to provide considerable

improvement over the exposure conditions prevalent in a

^3
relatively clean laboratory. Some experiments designed to

evaluate the quality of the air within these hoods are described

in Section F.2. on page 53 of this report.

C . Major Constituent Analysis

Both conventional and comparative polarographic methods

have been under continuous development during the past several

years to provide improved methods for microchemical analysis.

The analysis of standard reference materials as well as research

materials from other NBS programs has been facilitated. A fev;

examples are described in the following sections.

1

Copper and Zinc in Metal Foils

A sample of metal foil, believed to be either 70 Cu-30

Zn or 80 Cu-20 Zn was submitted for identification. A lyO-mg

sample was dissolved in nitric acid and diluted to one liter

with a supporting electrolyte of pyridine- pyridinium chloride.

Copper and zinc were then measured concurrently at about -0.4

and -1.1 V, respectively vs. a mercury pool anode by cathode

ray polarography . Calibrations were established using SRM 45d,

melting point copper, and SRM 43e, melting point zinc, respectively as standards. This particular analysis gave results

of 80.4 percent Cu and l8 . 7 percent Zn. While a relatively

large sample was available, similar results could have been

obtained on fractional milligram samples, by appropriately

adjusting the volume of solution. Under such circumstances,

weighing of the sample would be the major source of error.

2Copper and Nickel in Foils

Several foils containing major concentrations of copper

and nickel with iron as a minor constituent were submitted

for analysis. These foils were to be used as standards for

spectrographic analysis for which purpose the major constituents

needed to be determined within 0.5 percent. Samples weighing

8, 10, and 23 mg, respectively, were dissolved and diluted to

either 50 or 200 ml with a pyridine-pyridinium chloride supporting electrolyte. The copper and nickel reduction peaks were

44
measured concurrently at about -0.4 and -0.8 V, respectively,

vs. a mercury pool anode. The results are given in Table 10.

Table 10. Analysis of Cu-Ni foils.

Sample

designat ion Fe, %^ Cu, % Ni, % Total, %

P 33 0.4 54.8 43.4 98.6

P 48 1.8 54.3 43.4 99.5

P 6o 1.7 47.6 50.7 100.0

^By B. B. Bendigo, Analytical Coordination Chemistry Section.

3 . Antimony in Lead-base Bearing Metal

A comparative polarographic method has been developed and

used for the determination of antimony in lead-base bearing

metal. The new method is equal in reliability but is more

rapid than the long, conventional chemical procedure which

involves a distillation, a hydrogen sulfide precipitation,

and titration with potassium permanganate. A set of samples

can easily be completed within several hours.

The procedure is as follows: One-gram samples are

dissolved in dilute nitric and perchloric acids and heated

to perchloric fumes. Concentrated hydrochloric acid is

added, the solution is warmed gently to dissolve salts, and

transferred to a 1-liter volumetric flask. Ascorbic acid is

added to reduce any iron present, and water is added to the

flask to dilute to volume. Antimony is measured comparatively

with respect to a suitable standard. In this case lead-base

bearing metal, SRM 53e, served as the standard.

This method was used to determine antimony in a leadbase bearing metal standard undergoing certification analysis.

This material is issued in chip form as SRM 53e for chemical

methods, and as SRM 1132 for use as a spectrographic standard.

45
The SRM 53e had been completely analyzed by conventional

chemical methods, as had all of the elements in the SRM 1132

except for the antimony content., Accordingly, SRM 53e was

available as a standard for the comparative polarographic

method, although previous members of the SRM 53 series could

have been used.

The accuracy of the method is illustrated by the value

of 10.22 percent antimony that was obtained. Due to the comparative nature of the method and availability of a reliable

standard, this result is believed to be accurate to within

0.04 percent, absolute.

4 . Cadmium in Cadmium Cyclohexanebutyrate (SRM 1053a)

The comparative polarographic technique has provided

accurate results in the analysis and homogeneity testing of

cadmium cyclohexanebutyrate (SRM 1053a) which is used for

blending with lubricating oils to prepare standards for

monitoring wear of engine parts. The following procedure was

used: After drying over PpO^- for 48 hours, duplicate 0.4-g

samples were slowly ashed and ignited. The residues were

dissolved in diluted hydrochloric acid and diluted to one

liter. Cadmium was then determined polarographically at about

-0.7 V vs. a mercury pool anode using reference solutions

prepared from cadmium metal which was approximately 99.99

percent pure. The results, as well as those later obtained

by another technique are shown in Table 11.

D . Minor Constituent Analysis

Previous experience in this laboratory has verified the

sensitivity, selectivity, and accuracy of the polarographic

determination of aluminum involving the reduction of the

Solochrome Violet RS complex. Accordingly, procedures developed

earlier for its determination in irons and stainless steels

were modified and applied to the determination of aluminum in

ferrosilicon, SRM 59a.

46
Table 11. Cadmium in SRM 1053a.

Cadmium, percent

Sample Neutron activation

designation Polarography analysisQTop 1

Top 2

Top 3

Top 4

Average 24.77 24.81

t_s

/n 95^ confidence level 0.03 0.25

Polarography

24 .81

24 .78

24 .74

24 .76

24 .74

24 .73

24 .80

24 .83

By S. S. Nargolwalla and J. E. Suddueth, Activation Analysis

Section.

The procedure is as follows: Samples of about 0.5 g were

dissolved in nitric and hydrofluoric acids, fumed with

perchloric acids and diluted to 50 ml. Five ml aliquots were

taken and the iron was extracted with cupferron and chloroform.

After adjustment of the pH to about 4.5 by addition of sodium

acetate, the aluminum was extracted with chloroform and

cupferron. Organic material was then destroyed with nitric

and perchloric acids and aluminum was determined polarographically

by reduction of the Solochrome Violet RS complex at about

-0.7 V vs. a mercury pool anode. The results are given in

Table 12 along with those submitted by cooperators using

other techniques.

47
Table 12. Aluminum in f errosilicon , SRM 59a.

Aluminum, percent

Sample Polarography A B C D

59a, IB 0.357

59a, 2M O.S^'^

59a, 3M 0.3^5

59a, 5T 0.3^5

59a, 5B 0.3^4

Average 0.3^7 0.35 0.35 0.37 0.35

s 0.006

E. Small Sample Analysis

Work has continued on the analysis of very small samples

of thin films vaporized onto a glass substrate. These films

have been produced by the Harry Diamond Laboratory in the

study of production of low temperature-coefficient circuitry

materials for highly stable microminiaturized circuits. Such

factors as resistive properties and the temperature coefficient

of resistance need to be correlated with film composition.

Since only several hundred micrograms of a sample is generally

available, methods of high sensitivity and accuracy are required,

A number of samples were submitted for determination of

copper, nickel, and chromium. In addition, nickel analyses

were required on 3 tungsten filaments from which the metal

film had been vaporized. The film was stripped from the

plate with dilute hydrochloric acid and hydrogen peroxide and

diluted to 50 ml. For chromium, 10-ml aliquots were taken

and oxidized by heating with hydrogen peroxide and sodium

hydroxide. The solutions were diluted to 10 ml and the

chromium reduction peak was measured at about -0.7 V vs . a

mercury pool anode. For copper and nickel, 10-ml aliquots

were used. After reduction of chromium with HpSO^, the

solutions were diluted to 10 ml with a pyridine-pyridinium

48
sulfate supporting electrolyte. The copper peak was measured

at about -0.5 V and nickel at about -0.9 V vs. a mercury

pool anode. Values ranging from 8 to 12 yg of copper, 100 to

200 yg of nickel and 70 to 200 yg of chromium were obtained

with Ni/Cu ratios of about 25 and Ni/Cr ratios of about 1.5.

Nickel in the tungsten filaments was determined in a similar

supporting electrolyte after prolonged leaching of the

filament with hot nitric and hydrochloric acids. Seven

hundred to 1000 micrograms of nickel was found on the filaments.

F . Trace Analysis

Most of the effort in the past year in the polarographic

laboratory has been concerned with trace analysis. The major

problem in such analyses is the blank, arising from the

environment as well as from the reagents used in the processing

of the sample. Sufficient instrumental sensitivity is presently

available and the techniques developed in this laboratory are

capable of determining a nanogram or less of many elements,

but the practical limit is often raised to the microgram

level, because of the large blank involved. Attempts to

alleviate this problem have been in two directions — that of

obtaining purer reagents, and that of providing a cleaner

atmosphere during the period of chemical processing.

1. Reagent Analysis

A number of commercially prepared "high-purity" reagents

have been supplied to us by the Separation and Purification

Section. In order to evaluate their usefulness in certain

determinations, it was necessary to first analyze them for

the elements of interest.

a. Perchloric Acid . Perchloric acid of "highpurity" grade was available from two different manufacturers.

One of the manufacturers also supplied two different lots

prepared at different times. Iron, copper, lead, and cadmium

were of interest and could be determined concurrently.

49
1

Fe Cu Pb Cd

2 1 3 <1

26 1 5 11

18 1 3 18

Twenty-five or 30-ml portions of the different samples

were evaporated to dryness in Teflon beakers. The residues

were redissolved in 0.05 ml of dilute hydrochloric acid,

diluted with 5 ml of an oxalic acid- ammonium oxalate supporting

electrolyte, and measured subtractively . The results are

shown in Table 13.

Table 13- Fe, Cu, Pb , and Cd in perchloric acid.

S amp 1 e Concentration, ng/g

Brand A

Brand B, Lot X

Brand B, Lot Y 34 1 3 <1

A method described by Pohl [16] for determination of a similar group of impurities in the ppb range in reactor

water appeared to be applicable with some modifications to

analysis of the acid. Pohl's method consists of addition of

equivalent amounts of Na EDTA and cadmium solutions to the

water sample. Those elements which form stronger complexes

with EDTA than cadmium displace equivalent amounts of cadmium

from the EDTA complex. The excess cadmium is then determined

polarographically . The method was modified to operate at a pH of 3 for use in the analysis of perchloric acid. At a pH

of 3j metals reported to have stability constants higher than

that of cadmium include copper, iron, mercury, nickel, and

lead. Other metals which are reported to form more stable

complexes than cadmium under the proper experimental conditions

might also be included in this group. Some of these are

vanadium, indium, thorium, scandium, gallium, zirconium,

titanium, bismuth, zinc, and rare earths. The method as

developed is as follows: Twenty-five or 30-ml portions of

the different samples of perchloric acid were evaporated to

50
dryness in Teflon. The residues were dissolved in 1 ml of

0.01 N hydrochloric acid and 1 ml of NapEDTA solution (94.6

yg) was added. The solutions were heated to form the EDTAcomplexes, then mixed with 3 ml of a solution containing

28.6 yg of cadmium which is equivalent to the amount of

EDTA added. The polarographic reduction peak of the uncomplexed

cadmium was then measured in the subtractive mode of operation

against a procedure blank which had been carried through the

entire procedure. The uncomplexed cadmium reduction peak

measured results from its displacement from the EDTA-complex

by metals present in the sample which form stronger EDTAcomplexes at this pH. Cadmium originally present in the samples

would also contribute to the measured reduction peak. The

results are given in Table l4.

Table 14. Total EDTA-complexed metals in perchloric acid.

Sample Concentration^ ng/g

Brand A 4o

43

Brand B, Lot X 170

Brand B, Lot Y 88

Ordinary Commercial 250

ACS spec, reagent

b. Nitric Acid and Hydrochloric Acid . Samples of

commercially purified nitric acid and hydrochloric acid were

received for evaluation for suitability for use in the determination of trace amounts of iron. Samples of 100 ml were

evaporated to dryness in quartz, the residues dissolved in

0.05 ml of dilute hydrochloric acid, and diluted with an

oxalic acid-ammonium oxalate supporting electrolyte. Iron

was measured polarographically and found to be 53 ppb (ng/g)

for the nitric acid and 19 ppb for the hydrochloric acid.

5:
Bismuth is an interference in this procedure and hence would

be included in the result above. Subsequent analysis by

another technique of a different lot of purified nitric acid

from the same supplier showed bismuth to be about 25 ppb.

Bismuth interference can be eliminated by the use of the

supporting electrolyte, ammonium acetate-EDTA , in which iron

is reduced at about -0.2 V and bismuth at about -0.7 V. A

repetition of the analysis in this latter electrolyte gave an

iron value of 50 ppb for the nitric acid and 14 ppb for the

hydrochloric acid, which are considered to be in good agreement with the previous results.

c. Ammonium Hydroxide . A solution of ammonium

hydroxide prepared by G. Sleater of the Separation and

Purification Section was submitted for determination of iron,

copper, lead, and cadmium; This reagent had been prepared by

passing tank ammonia gas through distilled water for 5 1/2 hrs.

The sample was analyzed as follows: Triplicate 100-ml portions

were evaporated to dryness. The residues were dissolved in

0.1 N HCl, 5 ml of an oxalic acid-ammonium oxalate solution

was added, and iron, copper, cadmium and lead were determined

polarographically . The results are shown in Table 15.

Table 15. Analysis of ammonium hydroxide.

Concentration, ng/ml

i

Fe Cu Pb Cd

3.2 3.8 <1 n.d.

3.5 5.4 n.d. n.d.

5.6 5.4 n.d. n.d.

Average 4.1 4.8 n.d. n.d.

Under the conditions of this experiment the detection

limit was less than 0.5 ng/ml.

52
2 . Environmental Analysis

a. Laboratory Air . The contamination from the

ambient air of samples undergoing chemical processing Is a serious problem In trace analysis. The potential danger of

Introduction of foreign material Is obvious but the quantitative aspects are difficult If not Impossible to fully evaluate.

Experience over many years has shown fluctuations In blanks

that could only be ascribed to accidental contamination from

the surrounding air.

A number of analyses have been made during the past year

to determine the quality of the air In a typical laboratory.

In the clean-air hoods described earlier In this chapter (p. 44),

and In the class 100 clean room of this Division.

Samples were collected on acid-washed, 47 mm, 0.8 ym

pore size membrane filters, using the house vacuum line with

a lO-l/mln limiting orifice Inserted In the outlet connector

of the filter holder. From about 30 to 100 m of air were

sampled. The results are shown In Table 16.

Table 16. Particulates In laboratory air.

Concentration, yg/m

Room

B309 high

low

B325 high

low

B323 0.2 0.01 0.2 0.001

The new class 100 laminar flow clean hoods were also

monitored when they were first Installed In room B323. Air

samples from 170 to 350 m were collected and the polarographlc

results are shown In Table 17 together with those from similar

studies of the clean room A306. This and the above work was

53

Pe Cu Pb Cd

0.3 0.03 0.6 0.002

0.1 0.003 0.1 0.001

0.3 0.04 0.7 0.007

0.1 0.01 0.3 0.001
done in collaboration with R. A. Paulson also of the Microchemical Analysis Section.

Table 17- Particulates in clean room air.

,3 Concentration^ yg/m

Fe Cu Pb Cd

0.0009 0.007 0.0003 0.0002

0.001 0.002 0.0002 n.d.

Location

B323 clean hood #k

A306 clean room

A comparison of the results given in Tables 16 and 17

show the marked improvement provided by clean facilities.

To determine the size of blank resulting from atmospheric

exposure of a typical sample container during processing,

2 beakers with internal surface areas of about 0.012 m were

allowed to sit in various laboratory areas for 6 days. Iron,

copper, lead, and cadmium were then determined polarographically

and the results are shown in Table l8

.

Table l8. Fallout in laboratory and clean room air.

Fallout, yg/6 days/0.012 m

Location Fe Cu Pb Cd

clean hood #0

clean hood #4

conventional lab 0.042 0.008 0.006

hood

Iron is seen in all cases to be high enough to limit the

polarographic sensitivity obtainable. Copper and lead in hood

and lead and cadmium in the regular lab hood are also higher

than the polarographic detection limit and, accordingly, would

make significant contributions to the blank.

Experiments will be carried out to determine the titanium

and aluminum blanks from the regular laboratory hood and the

laminar flow hoods in the near future. A titanium pigment54

Fe Cu Pb

0.010 0.010 0.015

0.027

0.042 0.008
epoxy paint was used in the laminar flow hoods and conceivably

could contribute to a titanium blank. Also, large areas of

aluminum are present as separators in the filter, possibly

adding to the already high aluminum blank. It is especially

important to have clean hoods which will lower the iron, aluminum

and titanium blanks rather than contribute to them. Studies

made in the Spectrochemical Analysis Section indicate that these

elements (as well as others) may be present in amounts greater

than 10 percent in ordinary laboratory dust fallout. In some

recent determinations in this laboratory of traces of iron and

aluminum in orchard leaves, the total blanks ranged from 1 to 3

micrograms. Applying the rule that the total signal from the

sample should be twice that of the blank, this would limit the

amount determined to several micrograms, whereas sufficient

sensitivity is available to determine several nanograms.

b. Industrial Air . To illustrate polarographic

contributions in the solution of a typical industrial hygiene

problem, a recent example will be described. The NBS Glass

Section needed to prepare several special batches of leaded

glass in a general purpose laboratory; however, safety regulations require that the lead content of the air in such a case should not exceed 200 yg/m . Samples collected under

various conditions were submitted along with a blank filter.

The procedure used was as follows: The samples were ashed

in a low temperature asher at 200 °C and the residues dissolved

by heating with nitric acid. Hydrochloric acid was added and

the solutions were again evaporated to dryness. The residues

were dissolved in 10 ml of 0.1 N hydrochloric acid and measured

subtractively on a cathode ray polarograph at about -0.5 V vs.

a mercury pool anode using the blank filter which had been

carried through the procedure as a background blank. Results

of about 0.9 to 8 micrograms showed the lead particulate

content to be well within safety regulations.

55
3 , Lead In Fish Protein Concentrate . This laboratory has cooperated with the U.S. Bureau of

Commercial Fisheries for several years in the determination

of im.purities in fish protein concentrate (FPC) intended for

human consumption. During the past year, a number of analyses

were made to compare the lead content of concentrates prepared

from several kinds of fish.

Samples of either fish or protein concentrate V7ere dry-ashed,

the residues were dissolved in dilute hydrochloric acid, and

iron was reduced with hydrazine hydrochloride. The lead was

then extracted with sodium diethyldithiocarbamate and chloroform.

The organic material was destroyed, after which the lead

reduction peak was measured polarographically in 0.1 N HCl.

The values obtained in previous years as well as most of the

present values ranged from several tenths to about 1 yg/g of

FPC, but those for FPC prepared from anchovies were about

5.5 yg/g of FPC. In order to verify that the lead was coming

from the anchovy and not introduced during the processing,

samples of raw fish were analyzed. The anchovy again showed a

similar high level of lead. We have been informed that these

analyses provide the basis of a decision not to use anchovies

from this location for the preparation of FPC. The studies also

showed a variation in lead content with the geographic area from

which the fish were taken.

4

Copper and Zinc in Blood Plasma Processing Intermediates . Determinations of copper and zinc in saline solutions and

sodium lactate solutions used in processing blood were made for

the American National Red Cross. Either one or both of the

solutions provided were suspected of being contaminated with

copper or zinc. These elements could be determined directly

in the sample using the solution itself as a supporting electrolyte provided a suitable calibration curve could be established.

For the curve to be valid, known amounts of copper and zinc

should be added to solutions simulating the composition of the

56
samples. However, no sodium chloride or sodium lactate of

known purity was available, so the method of standard additions

was used, which consisted of adding aliquots of copper and

zinc solutions prepared from high purity melting point copper

and melting point zinc to 5-nil aliquots of the samples. The

results of the analysis are shown in Table 19.

Table 19. Copper and zinc in sodium lactate and sodium

chloride solutions.

Concentration, yg/ml

S amp 1 e s Cu Zn

\% Sodium chloride 0.23 0.30

.15 .32

Average .19 .31

\% Sodium lactate 3.3 1.9

3.5 1.5

Average 3.^ 1.7

It was concluded that the sodium lactate solution was not of

sufficient purity for use in blood processing.

5 . Lead, Bismuth and Tellurium in Special Steels . A series of 5 special steels and irons have been developed

for issue as general purpose standard reference materials for

the iron and steel industry. These materials were prepared by

special melting, casting and fabrication techniques and consist

of a graded series of some 36 elements covering the useful

concentration ranges required by the iron and steel industry.

Polarographic methods have been developed and used for the

determination of lead, bismuth, and tellurium in these special

steels. Because these elements are present only in trace amounts,

conventional chemical methods are not very satisfactory. The

57
procedures are as follows: For lead and bismuth, 5-g samples

of SRM 361 and SRM 1261 and 0.5-g samples of SRM II78 were

dissolved in hydrochloric and nitric acids, evaporated to

dryness, dissolved in HCl and diluted to 50 ml with concentrated

HCl. The silica was allowed to settle after which 10-ml

aliquots were taken and the bulk of the iron was extracted with

isobutyl acetate. The aqueous layer was evaporated to dryness

and the residue dissolved in 10 drops of hydrochloric acid,

then in 15 ml of water. Lead and bismuth were extracted with

sodium diethyldithiocarbamate and chloroform from an ammoniacal

solution containing cyanide and tartrate to complex interferences. After elimination of organic material, lead and bismuth

were determined polarographically . SRM II78 was used as an

analytical control. Values of 0.013 percent bismuth and

0.004 percent lead were obtained for SRM II78 which is

certified to contain 0.013 percent bismuth and 0.00^ percent

lead. The results for the special steels are shown in

Table 20. Although comercially purified acids were used and

all other reagents were purified by pre-extraction of lead,

a reagent blank of approximately 1 yg of lead was obtained.

Table 20. Lead and bismuth in special steels.

Metal content

Sample Bi ^ppm Pb , ppm

361-composite 4.4 .22

5.7 .17

Average 5.0 : .20

1261-composite B (2A + 2C) 4.1 .20

4.3 .22

Average 4.2 .21

58
The major part of this blank has been proven to come

from the reagents. Earlier work has shown none to come from

the containers and the fallout studies discussed In Section 2.

show an expected contribution of only 8 ng, or less than

1 percent of the total lead blank, attributable to the

atmosphere

For the determination of tellurium, 10-ml allquots of

the solutions described above were taken. Tellurium was

separated from the iron by precipitation with sulfur dioxide

using a selenium carrier [1?]. After filtration, destruction

of organic material and volatilization of selenium, tellurium

was determined polarographically . The results are shown in

Table 21.

Table 21. Tellurium in special steels.

Sample Tellurium, percent

36l-composite 0.00041

0.00039

1261-composite B (2A+2C) 0.00051

0.00046

Essentially, the same procedure was also used to ascertain

conformance with specification of a forthcoming addition to

this series of special steels. Average values of 0.012 percent

lead, s=0.0001, 0.020 percent bismuth, s=0.001; and 0.0043

percent tellurium, s=0.00033 were obtained.

6 . Titanium in Special Steels and Ductile Irons . Procedures were developed and used to determine titanium

in ductile iron as well as in the special steels provided above.

Titanium in ductile iron SRM ll4o was determined on triplicate

0.5-g samples. Titanium was separated by precipitation first

with cupferron, and then with ammonium hydroxide. After

destruction of organic material and evaporation to dryness,

59
the titanium residue was dissolved in sulfuric acid (1+1) and

diluted with an oxalic acid- ammonium oxalate supporting

electrolyte. Titanium was then measured polarographically

and the results are given in Table 22, along with results

obtained by a cooperating analyst.

Table 22. Titanium in ductile iron SRM ll40.

Titanium^ percent

Polarography Cooperator A

0.093

0.095

0.098

Average 0.095 0.09^

Titanium in special steels, SRM 365 and SRM 1265, was

determined using 1-g samples. In this case the bulk of iron

was extracted with isobutyl acetate from a hydrochloric acid

solution. The acid extract was evaporated to dryness and the

titanium determination finished as already described for SRM

Il40. The results are shown in Table 23.

Table 23. Titanium in SRM 365 and SRM 1265.

Sample Titanium, percent

SRM 365 0.00072

0.00064

0.00052

0.00061

Average O.OOO6I

SRM 1265 0.00052

0.00052

Average 0.00052

60
7 . Nickel, Iron, and Titanium In Glass . The concept of glass-base trace element standard reference

materials as well as preliminary work and method development

were described in the I969 report of this Section [12], Work

has continued in this laboratory on the determination of

trace elements in glass standard reference materials.

The method developed here for nickel in nickel-doped

soda lime glass has been applied to its determination in the

500-ppm glass and has been modified for the 1-ppm glass with

excellent results. The modified method will also be applicable

to the remaining standards. Excellent agreement with results

by another technique (spectrophotometry) was also obtained for

the 500-ppm glass. No other technique has so far determined

nickel in the 1-ppm standard. The method developed is given

below.

Wafers weighing approximately 1 g were cleaned first

with alcohol and then with dilute nitric acid. The samples

were dried, weighed, dissolved in hydrofluoric acid, and

fumed with perchloric acid. After dilution to 50 ml, addition

of sodium citrate, hydroxy lamine hydrochloride, and ammonium

hydroxide, nickel was extracted with dimethylglyoxime and

chloroform. The chloroform was evaporated, organic material

destroyed, and the nickel reduction peak was measured at

about -1.0 V in a pyridine-pyridinium sulfate supporting

electrolyte. The results are shown in Table 24.

Results later obtained by E. R. Deardorff of the

Analytical Coordination Chemistry Section using spectrophotometry agreed exactly with the 450 ppm value obtained in

this laboratory.

By a minor modification involving limitation of total

volume, the method described above can be applied to the

1-ppra glass. Although the previous literature reports that

at least 5 yg must be present to insure complete extraction,

it was noted that most of these methods used relatively large

volumes during the extraction. By keeping the extraction

61
Table 24. Nickel in 500-ppm glass.

Nickel, ppm

Set No. 1 2 3 4 b 6

Sample

avg. ppm

Sample No. 2A 450

459

455

455

13A

18a

48A

442

458

463

442

449

441 447

441 450

450

451 445

447 451

459

56A 441

448

439 443

66A 459

464

461

446

456

455

447

455

78A 444 451

444

446

I06A 444 445

446

445

Set Avg^ppm 451

Total Avgjppm 450

Sjppm 7

s,^ . 1.6

461 444 444 450 450

ts for 95^ confidence, 2.6

Vn ppm

ts for 95^ confidence, 0.6

7n %

62
volumes as small as possible, it seemed probable that a microgram or less could be extracted. Accordingly, the

volume of the aqueous layer was kept at 7-8 ml and it was

found that as little as 0.5 yg of nickel could be quantitatively

extracted.

Nickel in 1-g samples of the 1-ppm glasses was then

determined as just described and the results are given in

Table 25.

Table 25. Nickel in 1-ppm Glass

Portion Ni , ppm Sample Average

2 0.84

0.85

0.84

36 1.05

0.98

40 0.91

0.85

69 1.03

1.06

76 0.97

0.93

114 0.97

1.01

Overall Sample Av erage, ppm

s , ppm

0.84

1.02

0.88

1.04

0.95

0.99

0.95

0.08

s, % 8.4

The method developed previously [12] for the determination

of iron and titanium in soda-lime glass appeared to be

applicable to the trace glass standards, with some modifications. Two supporting electrolytes had been investigated —

EDTA-sodium acetate and sulfuric acid-sodium pyrophosphate.

63
Because problems had recently been experienced with keeping

the titanium in solution using the pyrophosphate supporting

electrolyte, it was eliminated as a possibility. Investigation

of an oxalic acid supporting electrolyte showed good applicability in the 1-10 ug range, so it was used for the 0.02-ppm

and the base glasses.

After dissolution of the samples and volatilization of

HF as already described for nickel, iron and titanium were

extracted with cupferron and chloroform. The chloroform was

removed by evaporation, the organic material was destroyed,

and the iron and titanium reduction peaks were measured

subtractively using, in the second cell, a blank carried through

the procedure. Iron blanks were somewhat high as discussed

earlier in Section 2a; values ranging from 1 to 3 yg were

obtained. The results on the base and 0.02-ppm glasses are

given in Tables 26 and 27.

Table 26. Iron and tj.tanium in base glass.

Position Fe, ppm Ti, ppm

8 11.98, 12 .99 2.70, 2.58

31 12.29 2.78

41 13.05 2.86

61 12.25, 13. 07, 12 .78 3.07, 2.43, 2.60

87 13.68 2.80

107 12.46 2.88

117 12.35 3.02

131 12.52 2.75

Average 12.67 2.77

Standard Deviat ion 0.49 0.19

ppm

ts for 95^

7n confidence, ppm 0.34 0.13

At first, there was speculation over the possible reversal

of samples, since the 0.02-ppm glass showed somewhat lower

64
Table 27. Iron and titanium in 0.02-ppm glass.

Position Fe, ppiTl Tl, ppm

2 11.16, 11.39, 10.78

33 9.96

43 10.54

51 10.47

61 10.25

76 10.16 -- 130 11.49, 12.35, 11.92

Average 10.95

Standard deviat-ion 0.77

ppm

ts for 95^

/n confidencej ppm 0.53

2.33, 2.39, 2.63

2.14

2.84

2.73

2.67

2.59

2.17, 2.52, 2.38

2.49

0.23

0.16

amounts of iron and titanium than the base glass. As results

for other elements came in, however, the same apparent reversal

persisted. It was then postulated that the base glass, which

had been prepared first, had in effect, cleaned the walls of

the melter of certain impurities and in so doing contaminated

itself. No other values have been reported for iron and

titanium as yet.

Iron and titanium were then determined in the 1-ppm

glasses using the same procedure, except dilute hydrochloric

acid was used instead of dilute nitric acid to clean the glass

wafers. It was felt that hydrochloric would be a better

solvent for adventitious iron or titanium on the wafer surface.

Single or duplicate determinations were made at six different

sample positions. Average values of 13.5 PPm of iron with a standard deviation of 0.7 Ppm and 3.1 Ppm of titanium, with

a standard deviation of 0.15 Ppm were obtained. No other

values have been reported as yet.

For the 50-ppm glass, an additional separation was

necessary, as 50 ppm each of possible interferences such as

65
copper, vanadium and molybdenum had been added. These elements

would be also extracted with cupferron, but could be separated

by an ammonium hydroxide separation. To insure complete

precipitation of iron and titanium and also a valid blank,

zirconium was added as a carrier. Since bismuth, which was

also added to the glasses, might not be completely separated,

it was necessary to use a supporting electrolyte other than

oxalic acid. (The bismuth peak potential in the oxalic acid

supporting electrolyte is too close to that of iron for good

peak resolution. ) In the EDTA-sodium acetate supporting

electrolyte discussed earlier, the bismuth peak potential is

displaced to about -0.7 V which is sufficiently far from

both iron and titanium to provide good resolution. The 50-ppm

wafers were analyzed using this modified procedure and the

results are shown in Table 28.

Table 28. Iron and '.titanium in

Sample

Designation Fe, ppm

2A 42.22^

37A 52.43

4 4A 51.43

68A 50.55

75 50.53

114 51.14

114 51.69

Average 51.30

s , ppm 0.75

s, % 1.5

Ti, ppm

40.32^

49.91

50.65

49.78

51.03

50.36

48.16

49.98

0.31

.62

Not included in average.

The extremely low value obtained for 2A is thought to

be real and indicates a deviation in composition of this rod.

Accordingly, it will not be used as a SRM. An average value

of 51.7 ppm of iron was obtained by R. W. Burke, of the

66
Analytical Coordination Chemistry Section by a spectrophotometrlc

procedure, showing excellent agreement between the two

techniques. No other values have been reported for titanium.

Iron and titanium were determined In the 500-ppm glass

by essentially the same procedure as for the 50-ppm glass;

however, some difficulty was experienced In keeping the titanium

In solution at various steps of the procedure. For example,

after fuming with perchloric acid to remove the hydrofluoric

acid, a large amount of Insoluble residue was obtained and

addition of hydrochloric acid was necessary along with prolonged

heating to redlssolve It. Concentrated sulfuric acid is a better solvent for hydrolyzed tltanla, but the excessive

precipitate of calcium and lead sulfates precluded its use at

this stage. Reversing the order of the separations and

precipitating with ammonium hydroxide before extraction with

cupferron was unsuccessful because the bulky precipitate

resulting from the presence of almost every element of the

ammonium hydroxide group, including the rare earths, made

thorough washing of the precipitate very difficult. In taking

pure solutions of iron and titanium with zirconium added as

carrier through the entire procedure, recoveries of 99.6 percent

of the iron, and 99.^ percent of the titanium were obtained.

The first results for 15 separate determinations gave an

average for iron of 461 ppm with a standard deviation of

20 ppm. In an attempt to determine if this deviation resulted

from actual sample Inhomogeneity or arose from the procedure,

duplicate allquots were taken. Some errors from loss or

contamination could, of course, occur during solution and

before the allquots were taken; but the bulk of the chemical

processing occurs after the allquoting. The results are

shown in Table 29

.

. While the agreement between allquots is somewhat better

than that between separate samples, it is not enough to show

conclusively whether sample Inhomogeneities exist. Again,

the average spectrophotometrlc value of 461 ppm obtained by

67
Table 29. Iron in 500 ppm-glass.

Sample No. Iron, ppm

Aliquot

Average

Sample

Average

2 482^

482^

482 482

18

460^

456 456

56 469^

469

469 469

13 458^

458^

447°

441°

458

444

451

48 447^

466^

464^

452°

456

458

457

66 458^

452^

458

448

453

78 462^

462^

460^

454'^

462

457

460

106

458^

456 456

Overall sample average, ppm 460

Standard deviation, ppm 10

Standard deviation, % 2.2

Duplicate aliquots

Duplicate aliquots of second solution

R. W. Burke is in excellent agreement with the polarographic

results. Sample 2 was significantly and consistently higher

in iron, so it will not be included in the final SRM. The

values obtained at the same time for titanium are shown in

Table 30.

68
Table 30. Titanium in 500-ppm glass.

Sample No. Titanium, ppm

Aliquot

Average

S amp 1

Average

2 432^ 434 434

18 427^

427

427 427

56 447^

442^

444 444

13 430^

437^

417^

434

434

434

48 427^

428^

433^

442

430

436

ee 415 415 415

78 419^

423^

449^

449

421

449

435

106 444^

451^

448 448

Overall sample average, ppm 434

Standard deviation, ppm 10

, duplicate aliquots

duplicate aliquots of second solution

Niobium, which was also added to the glasses could

probably have been analyzed at the same time as it is also

separated with the iron and titanium and its reduction peak

follows that of titanium.

(E. J. Maienthal).

69
3. MICROSCOPIC AND CLASSICAL MICROCHEMICAL ANALYSIS

A . Introduction

This laboratory has been concerned for a number of years

with the analysis of small samples by classical microchemical

techniques. Both organic and inorganic samples are analyzed

with the work level about equally divided between the two

categories. The laboratory has responsibility for maintenance

of a clean room facility and provides microscopic and micromanipulation services to other projects of the Division. Some

of the more interesting activities of the past year in the

areas mentioned above are described in the following sections

of this report.

B. Microchemical Standards

This laboratory has the responsibility for the development

and certification analysis of a series of standard reference

materials specially suitable for calibration or analytical

control of microchemical procedures. Two new materials have

been added to this list of SRMs during the past year. One of

these is highly purified urea for use in nitrogen determination

while the second is bromobenzoic acid intended as a halogen

standard. Preliminary work has been done on certification of

chlorobenzoic acid and a search is in progress for procurement

of a highly fluorinated organic compound.

1. Urea, SRM 2l4l

The NBS office of Standard Reference Materials presently

issues Urea SRM 912 as a standard for clinical chemical

analysis. A similar lot of highly purified urea has been

procured, standardized, and has just been released for issue

as a standard for the determination of nitrogen in organic

materials containing large amounts of this element. Many of

the present day automatic carbon-hydrogen-nitrogen analyzers

compare samples through peak heights. Thus compounds of

known high purity must be used to standardize the apparatus.

More accurate results are obtained when the composition of the

70
sample is close to that of a standard. The highest nitrogen

in the present microchemical SRM series is only 11.4^ nitrogen.

Urea contains 46.65^ nitrogen, hence, a more appropriate

standard for high nitrogen determinations. Since knowledge

of the nitrogen content is of considerable importance in many

instances, highly reliable nitrogen values are often needed.

The A.O.A.C. microchemical Kjeldahl method [18] was

adapted for larger samiples of higher nitrogen content. Fifty

milligram samples were used and the ammonia was absorbed in

50 ml of 0.05 N HCl. Preliminary experiments showed that the

large amount of distillate required to carry over all of the

ammonia resulted in excessive dilution which made the titration

in the boric-acid methyl-purple indicator method less accurate.

Accordingly, hydrochloric acid was used in the absorbing

solution and the excess was determined by potentiometric

titration with 0.05 N NaOH to a pH of 5.5. Each distillation

was run for ten minutes. To be certain that all of the ammonia

had distilled over, the first absorber was replaced with a second one containing 5 ml of boric acid. The ammonia thus

absorbed was titrated directly v/ith 0.05 N HCl using methyl

purple indicator. Under the conditions used, the second

titration seldom exceeded 0.1 ml. The 0.05 N HCl was standardized both by coulometric titration and by titration against

[ (Tris (hydroxymethyl) aminomethane) ] SRM 723, a basimetric

standard.

Table 31. Determination of nitrogen in urea SRM 2l4l.

Day

Bottle

1 46.54

12

(1) 46.58 (3) 46.66

3^

(4) 46.66 (6)

2 46.65 (6) 46.55 (2) 46.62 (1) 46.72 (3)

3 46.63 (5) ^6.64 (4) 46.57 (5) 46.66 (2)

4 46.65 (2) 46.62 (6) 46.65 (3) 46.61 (1)

5 46.78 (3) 46.68 (5) 46.67 (2) 46.57 (4)

6 46.71 (4) 46.62 (1) 46.54 (6) 46.62 (5)

71
The urea was received from the supplier in six bottles.

One sample from each bottle was analyzed on each of four days

in a random order for a total of 24 determinations. The

analytical results are given in Table 31. The numbers in

parenthesis indicate the order of analysis on that day. The

overall average found was 46.633% N with the standard deviation

for a single measurement of 0.058%. The standard error of the

overall average is 0.0119% and the 95% confidence interval is

46.6o8 to 46.658. The theoretical value for nitrogen in urea

is 46.659%. There is no evidence of systematic differences

due to order of analysis or between samples of the lot of

material

.

The nitrogen value of a sample of single crystal ammonium

dihydrogen phosphate was determined at the same time. The

average value of six determinations was 12.173% N with a

standard deviation of the mean of 0.005. The theoretical value

is 12.178%. Accordingly, it was concluded that there is no

significant amount of bias in the analytical measurements.

An estimate of the homogeneity of the urea using small

(0.6 mg) samples was made using a commercial carbon-hydrogennitrogen analyzer. The peak heights for each element in a

series of six runs were measured and compared. The results

are given in Table 32. The variation in peak height includes

both, any inhomogenelty of the sample and the variability of

operations and measurement. It is concluded that the urea

Table 32. Homogeneity studies of urea SRM 2l4l.

Avg peak height, mm (x)

s = standard deviation, mm

Relative s = ^^3^,,%

X

Theoretical composition, %

Relative s at this composition

level, %

72

Nitrogen Carbon Hydrogen

166.2 171.3 105.7

0.2 0.8 0.4

0.12 . .^7 0.38

46.12 20.00 6.67

0.06 0.09 0.03
is homogeneous in respect to those elements within the limits

of precision of the analytical method. The moisture content

of the urea was found to be 0.05% by the Karl Fisher titration

method

.

2 . Intercomparison of Microchemical SRMs

A study was made of the present microchemical SRMs to

ascertain whether there had been any change in these materials

since they were first issued. Several of these standards are

almost ten years old and one—^Anisic Acid SRM l42 —is almost

30 years old.

Benzoic Acid SRM l40b5 Acetanilide SRM l4lb. Anisic

Acid SRM 142, and Nicotinic Acid SRM l48 were analyzed at the

same time in our laboratory and they showed a high inter-sample

consistency in carbon and hydrogen and, in the two where it is

present, nitrogen. The elemental compositions found were well

within the expected limits of agreement with their theoretical

proportions. Excellent agreement was also found in the phosphorus and sulfur content of triphenyl phosphate and cystine,

respectively. In addition, benzoic, anisic and nicotinic acids

were titrated with 0.1 N sodium hydroxide to obtain their acid

equivalent values. The results of all of the determinations

are summarized in Table 33.

Table 33- Purity of microchemical SRM's.

Analytical measurement

Micro Micro Micro Micro Titrations

carbon nitrogen sulfur phosphorus

I % %

100.10

99.96

i

Benzoic Acid

SRM l40b

100..1

Acetanilide

SRM l4lb

99..9

Anisic Acid

SRM 142

Cystine SRM l43b

Trlphenylphosphate

SRM 147

Nicotinic Acid

SRM 148

99.

99.

.9

.2

99.7

99.7

100.4

98.2 100.00

73
While the results of Table 33 Indicate that the SRMs

were satisfactory to serve as microchemical standards, it was

conceivable that a significant amount of decomposition not

affecting the elemental analysis could have taken place. To

eliminate any doubts of this nature, the materials were

examined by several instrumental techniques including mass

spectrometry, gas chromatography, paper and thin-layer chromatography, differential scanning calorimetry, and ultra-violet

and infra-red spectrometry. Nuclear magnetic resonance spectra

were also obtained. None of these techniques indicated any

significant levels of impurities. Accordingly, the general

conclusion was reached that these materials have not undergone

any significant changes in composition and are entirely

adequate for use as microchemical standards.

3. Orchard Leaves, SRM 1571

This sample of orchard leaves will be issued as a standard

for the analysis of botanical matter. While the primary interest in it is perhaps the trace elements, it can also serve as a

standard reference material for the determination of elements

such as nitrogen and phosphorus in agricultural analysis.

Accordingly, determinations of nitrogen and phosphorus were

performed in this laboratory. In line with the recommendation

of the A.O.A.C. methods, the samples were dried at 90° C. for

24 hours under vacuum before analysis.

In the determination of nitrogen, the A.O.A.C. microchemical Kjeldahl method [l8] was used with some modifications.

Dried sample weights of approximately 0.25 g were digested with

sulfuric acid, potassium sulfate and mercuric oxide and then

distilled in the micro Kjeldahl distillation apparatus. As

with the determination of nitrogen in urea (given above), the

ammonia was absorbed in standard 0.05 N hydrochloric acid. The

excess standard hydrochloric acid was titrated potentiometrically with 0.1 N sodium hydroxide to a pH of 5.6. In

this determination the initial hydrochloric acid was measured

74
j with a weight burette instead of by volumetric measurement with

a 50 ml pipette. This gave better control over the amount of

excess acid present as well as a more accurate measurement.

The distillation was continued for 15 minutes since it was

verified that all of the ammonia was distilled in this time.

Although a second flask was added to check each determination,

no ammonia was found in it.

The leaves were received in 20 containers. Since

previous experience had Indicated that a relative standard

deviation of about 1 percent could be expected, it was decided

to analyze one sample from each bottle and to do replicate

analyses on any bottle that appeared to differ significantly

in composition from the others . No such differences were

found.

The results of the determination of nitrogen are tabulated

in Table 3^. The analytical sequence was downward in each

column.

Table 34. Nitrogen in orchard leaves, SRM 1571-

Bottle Percent

number nitrogen

18 2.76q

19 2.78^

15 2.7^2

5 2.74^

7 2.72^

17 2.76^

11 2.772

9 2.76-^

- 1- 2.74^

13 2.77q

General average 2.755

Standard deviation .019

Standard deviation of the mean .004

75

Bottle Percent

numb er nitrogen

4 2.72^

14 2.78^

8 2.75^

3 2.74^

6 2.72^

2 2.73^

20 2.77^

10 2.755

16 2.752

12 2.78q
Phosphorus was determined in the same 20 bottles of

orchard leaves using the A.O.A.C. microchemical method for

phosphorus [19]. Dried weighed samples of 0.3 g were used.

Each sample was digested with sulfuric acid and nitric acid

until the organic material was decomposed. This digestion

usually required about 5 hours. After dilution with an acid

solution, the phosphorus was precipitated as ammonium

phosphomolybdate, using ammonium molybdate reagent. After

standing overnight, the precipitate was filtered through a weighed fritted glass micro filtering tube. It was found to

be advantageous to use an ultrasonic bath to dislodge the last

traces of precipitate from the walls of the precipitation

flask. The precipitate was washed with ammonium nitrate

solution, ethanol, and acetone and then dried for 30 minutes

under vacuum at room temperature. The empirical factor of

0.01452 [20] was used in the calculations.

Table 35. Phosphorus in orchard leaves, SRM 1571.

Sample % Phosphorus Sample % Phosphorus

18 0.2088

15 .2112

7 .2065

17 .2097

5 .2081

4 .2108

19 .2079

9 .2060

6 .2082

14 .2072

13 0.2071

3 .2106

8 .2091

12 .2062

10 .2109

16 .2067

1 .2105

20 .2083

11 .2063

2 .2091

Avg. 0.2085

Overall average 0.2085^

Standard deviation 0.0017^

Standard deviation of the mean 0.0004^

76
The analytical results for all of the determinations

of phosphorus are given in Table 35. The analytical sequence

is downward and from left, then right.

The results obtained for both nitrogen and phosphorus

show that the SRM is homogeneous with respect to each element,

at the 0.25 to 0.30 g sample level, within the limit of the

analytical determinations.

C . Ultramicrochemical Standards

Work on the evaluation of very small ion exchange beads

as ultramicrostandards has continued (see reference [12]

pg. 101). Beads ranging in diameter from 5 to 25 ym have been

prepared by the Separation and Purification Section of this

Division and loaded with various cations. Since such beads

furnish a concentrated source of a very small amount of an

ion, they should furnish very small amounts of material for

checking such procedures as detection limits, for example.

Beads loaded with ammonium ion were prepared and studied

recently. Unlike many of the beads previously prepared,

this surrenders its cation, ammonium ion, readily so is a convenient source of that ion. The use of these beads as

standards for the microscopic spot test was studied, briefly.

Lodge [21] has used such a technique for identification of

air-borne particles but has not quantified it. The beads were

dispersed on a microscope slide and the diameters of individual

beads were measured using an eyepiece micrometer. Beads of

appropriate size were selected and transferred to a white

membrane filter. The color was developed by placing the

filter on a drop of Nessler reagent and letting it soak

through the paper for 30 seconds. The filter was then rinsed

well with water and dried. The filter was examined under the

microscope by both reflected and transmitted light and the

diameters of the spots were measured with the eyepiece micrometer. Results of a typical experiment are given in Table 36.

77
Weight NH^i

ng

Diameter of stain, ym

dark light

51 300 1100

8.2 150 750

1.^ 80

0.2 40

Table 36. Microscopic Nessler spot test.

4- Diameter of bead

ym

95

52

29

16

The weight of contained ammonium ion was calculated

by the formula W = p ^ d, where d is the diameter of the bead

and p is the partial density of the ammonium ion. These beads

contained 8.0 percent ammonium ion by weight and the density

was not measured but was assumed to be l.k g cm , based on

measurement of other beads. From this data, the value p

= 0.112 was calculated. When d is measured in micrometers, w

is expressed in picograms.

A logarithmic plot of weight of ammonium ion v/ith respect

to diameter of stain (light) is linear although the precision

was not as good as would have been desired. It is believed

that this would be improved by further studies which are

planned for the near future,

D . Research Material Analysis

1 . Copper-Nickel and Copper-Palladium Alloys

The Alloy Physics Section of the Metallurgy Division

prepared a series of copper-nickel and copper-palladium alloys

for use in studies of corrosion mechanisms. Samples of

approximately 0.5 g were available for analysis. Since spectregraphic analysis confirmed a pure binary system, only one of

the components, mainly copper, was determined and the second

calculated by difference.

The copper-nickel alloys were analyzed by a conventional

method, consisting of solution in nitric acid and electrogravimetric determination of the copper. Residual copper in the

electrolyte was determined spectrophotometrically using the

78
j sodium diethyldlthiocarbamate method. The alloys contained

I a small amount of black material insoluble in nitric acid.

! This residue was filtered on filter paper and ignited. The

ignited residue ranged from less than 0.01 percent to 0.24

percent of the original sample. The insoluble matter appeared

to be carbon and the analysis was corrected for its presence.

The determination of palladium in the copper-palladium

alloys provided a somewhat more complicated problem. Since

both copper and palladium are electrodeposlted under the same

conditions, a pre-separation had to be made. A method developed

by Gilchrist [22] at NBS a number of years ago was used to

effect this separation. In this, palladium is complexed with

sodium nitrite after which the copper may be hydrolytically

precipitated from hot solution at pH 8 as the hydroxide.

Since the precipitate is non-stoichiometric, it was filtered,

redissolved in nitric acid and the copper was electrodeposlted

on tared electrodes

„

In a few cases, the copper deposit was dark, indicating

some codeposition of palladium as a result of coprecipitation.

In such circumstances, the copper was redissolved in acid and

the palladium was determined by the gravimetric dimethylglyoxime method. The copper deposit was then corrected for

this palladium content which varied from 0.2 to 0.7 mg, A

correction was also made for residual copper in the electrolyte, which ranged from 0.1 to 1.8 mg.

By the use of the procedure described above, 0.5 g

samples were analyzed in duplicate for copper contents ranging

from 27 to 96 percent. Duplicate analysis shov/ed a maximum

difference of 0.08 percent copper.

2 . Tungsten-Rhenium Alloys

The Temperature Section of the Heat Division prepared

a series of 19 tungsten-rhenium alloys with rhenium content

ranging from 1 to 27 percent for special thermocouple studies.

The initial step in the preparation consisted of mixing purified

metal powders in proper proportion and subsequent formation into

79
4

wires. Analyses accurate to 0.1 percent were needed for control

of composition.

A method furnished by Cleveland Refractory Metals [23]

was used with only minor modifications for the determination

of the rhenium content. Weighed samples of the metal (50 mg

for 27^, 2 grams for 1%) were dissolved in a 3% hydrogen

peroxide solution. Both components dissolved under this condition, but the tungsten could be precipitated as the hydrous

oxide by the addition of hydrochloric acid. This oxide was

then redissolved and held in solution by the addition of

tartaric acid and ammonia. The rhenium was then precipitated

with tetrapheny larsonium chloride and 6 M ammonium hydroxide.

The tetrapheny larsonium-perrhenate was filtered on a

tared fritted glass filter, washed with a saturated solution

of tetrapheny larsonium-perrhenate solution, and dried. One

sample was analyzed in triplicate for which the results,

26.7^5 26.655 and 26.64 percent rhenium were obtained. Only

single determinations were made on the remaining alloys.

3. Thermochemical Reaction Evaluation

Assistance has been given to the Thermodynamics Section

in the analysis of residual sodium hydroxide from calorimetric

measurements of the enthalpy of the reaction of ketone gas

with aqueous sodium hydroxide in an adiabatic calorimeter,

according to the equation [24].

CH^ CO (g) + NaOH (aq, 500 H^O) —^ CH COONa ( aq , NaOH solution)

The best method for determination of the amount of reaction

that had occurred appears to be a careful determination of

the sodium hydroxide consumed. This was measured by analysis

of the original solution and after the final reaction.

For the calorimetric experiments the initial concentrations of the sodium hydroxide solutions was either 2 g/kg or

4 g/kg. Aliquots of original and final solutions were taken

by weight, and amounted to 50 g in each case. These were

titrated with 0.1 N hydrochloric acid in COp-free air. Each

80
was done in duplicate and differences reliable to 0.1^ were

obtained.

Because carbon dioxide was an impurity in the ketene and

also in the original sodium hydroxide, it too had to be determined. This was determined gravimetrically after evolution with

acid. The amount of carbon dioxide present in the residual sodium hydroxide solution averaged about 0.01 mg/g.

The final solutions were also analyzed for acetone which

could arise from polymerization of the ketene. An iodimetric

technique was used for this purpose and as little as 0.1 mg of

acetone/50 g aliquot would have been detected which would have

amounted to less than 0.05^. No acetone was found.

4. Fluorinated Copolymer Analysis

Elemental microchemical analysis has been used to determine

the composition of fluorinated copolymers for the NBS Polymer

Division, These polymers were prepared by mixing C„Fk with

C_F^H„, C^F„H^, or C|,F^H„. When two monomers are combined to 33 3' 57 3' 462

form a copolymer, the combining ratios are difficult to determine. However, if the monomers differ sufficiently in composition, determination of carbon or hydrogen in the copolymer can

serve to establish the ratio. The carbon determination is the

more precise procedure.

As an example of the technique, one set of these copolymers

was prepared from C^F^ and C^F^Hp which have carbon values of

24.0 and 29.3 percent, respectively. Even though these values

are not markedly different, precise analysis should provide useful information. To achieve acceptable precision, determinations

were made in replicate using 5 mg samples. A combustion tube

packed with MgO was used to remove fluorine and the COp and

water were absorbed and determined gravimetrically. The usual

standard deviations for a single determination in microdeterminations of this kind are 0.10^ for carbon and 0.05^ for hydrogen, respectively. By running 5 to 10 replicates, the 95 percent

confidence interval for the mean value approximates these limits.

R. A. Paulson and W. P. Schmidt

81
^. AIR POLLUTANT ANALYSIS*

A. Nature of the Analytical Problem

Chemical analysis is one of the most important aspects of

environmental surveillance and control. The atmosphere needs

to be analyzed and often continuously monitored to ascertain

compliance with or deviation from air quality standards. Such

data are also essential for establishing criteria upon which

air quality standards are based. Since measurements typically

are made over long periods of time, must be comparable v/ith

those of other locations or stations, and must be of legal

integrity to support compliance with standards, they must have

a high degree of precision and accuracy.

The determination of atmospheric pollutants and contaminants

involves a high degree of sophistication in trace analysis.

Constituents of interest need to be measured down to the partsper-billlon level in many cases. Consequently, analytical

methods must be very sensitive as well as selective to minimize

preseparation steps. Upon these requirements is often s-uperimposed such specifications as portability, continuous

monitoring capability, simplicity to enable use by semiskilled

technicians, and low initial and maintenance cost. Accordingly,

it is suprising that the state of the art is as well advanced

as it presently is.

Chemical analysis for air pollutants involves several

distinctive steps:

Interpretation

Sampling

Metrology

Physical Analysis

Chemical Analysis

This chapter consists of an appraisal of the present state

of the art of air pollutant analysis, identifies measurement

problems concerned with such analyses, and suggests areas of

research to provide improved measurement capability.
Each of these steps is involved directly or indirectly to a

greater or less extent in every determination. The details

(sub-steps) of each step need to be designed for the particular

application and must be of requisite reliability. When substeps are minimized or passed over, it must be assumed that

they are not significant and the validity of such assumptions

influences the validity of the entire measurement.

1. Interpretation

The use to be made of the data is a question that must be

answered before any analysis is made. This is necessary to

establish such matters as detection limits, accuracy, precision,

and the fine structural requirements such as whether an

elemental analysis or determination of a specific substance is

required. Measurement methods such as the "dust bucket",

"sulfur candle", or total oxidant may be meaningful or totally

inadequate, depending upon the information they are intended

to convey.

In addition to its critical input into method selection,

a consideration of the end use of the data will establish

sampling frequency and procedures, and provide for the design

of experimental procedures to insure statistical adequacy.

The significance of analysis is illustrated by Figure I5.

Analysis provides the numbers upon which decisions are made

and is the major measurement science of environmental evaluation

as well as other aspects of materials research. The diagram

emphasizes the extreme importance of the related steps and

their interdependence. The diagram also points out that

research in environmental analysis can lead to better methods,

techniques, and instrumentation, which conversely can lead to

better analytical data. Furthermore, fundamental studies can

provide input to better measurements which in turn are a

requisite for better understanding of fundamental principles.
ECOLOGY TOXICOLOGY

INDUSTRIAL HYGIENE

Figure 15. The analytical system for environmental

measurements

.

The lower part of the diagram Indicates that while environmental control is important, it is only one of the products of

environmental analysis. Many areas of industrial hygiene,

toxicology, and public health depend on measurements closely

similar to pollutant analysis. The presence of atmospheric

contaminants, whether or not they are pollutants, has important

implications in weather and climatology studies, on the

84

II
stability of materials , and on ecological relations. There

are many conflicting opinions In these areas that may have

been generated by poor analytical data, and undoubtedly would

be clarified by Improved environmental analysis.

The diagram points out that environmental science seeks

access to analytical measurements through the Interpretation

route, that Is by posing questions that analysis will answer.

It also suggests that analytical data properly Interpreted

can provide Input Into environmental science.

The diagram puts standard reference materials In the center

because they provide a means to Interrelate and verify the

adequacy of each step in the analytical cycle. There are

several laudable efforts In progress or proposed to provide

better analytical methodology. The validity of their conclusions would be enhanced if the experimental design Included

the use of Standard Reference Materials required for method

verification and/or calibration. Because of their intrinsic

nature, most methods not only need, but require standards to

verify their accuracy and Insure their reliability.

2 . Sampling

This step is an important part of every air pollutant

analysis and may be most difficult to Implement. Not only

must one know what to sample, but how and when it should be

done. The sampling technique must be such as to provide an

adequate and representative sample. Furthermore, it must

maintain the integrity of the sample up to the time of

analytical measurement. When a delay is necessary between

sampling and analysis, special precautions to maintain

stability of a sample may be required. In this event, one

technique that may be used is to react the sample with a reagent to produce a substance which is stable and can be

measured subsequently. Traps, liquid impingers, and absorbers

need to be designed for specific purposes. Gas samples may be

collected in glass vessels, in tanks of selected materials or

85
with special linings, or in plastic bags. Samples collected

on filters need to be interpreted on the basis of pore size

and filter composition, for example. Electrostatic and thermal

precipitators may be used but the possibility of chemical

alteration of some constituents of the sample is an important

consideration. The validity of the sampling technique needs

to be verified in every situation.

3

.

Physical Analysis

Techniques included in this classification have to do

with particulate analysis. The total atmospheric burden of

particulates, the measurement of size and size-distribution,

and the resulting modification of the atmosphere including

light obscuration, fall-out on material and vegetation, and

alteration of the esthetic aspects of the landscape are some

of the areas related to such measurements.

The importance of relating the physical analysis with the

chemical analysis is great, indeed, since an understanding of

the adverse effects of many particulate pollutants depends on

a knowledge of both size and composition. Thus, the physical

analysis may dictate the sampling technique. The intimate

relationship of physical analysis with other steps of the

analytical system is at once obvious.

4. Metrology

Analytical measurements are typically related to a

definite amount of total sample and expressed in concentration

units. Often a preconcentration step is involved in which the

final determination is related to a specified volume. Accordingly, measurement of rates of flow and cross-sectional areas

may be required. Flow meters, limiting orifices, syringes,

and gas burettes are some of the equipment for which calibration is required in such instances.

5. Chemical Analysis

This is the most obvious analytical step for which a variety of techniques are often available. Such methods may

86
be entirely wet chemical, partially wet chemical, or entirely

Instrumental. For the purpose of this discussion, all of

these are Included In the above heading. A survey of the

literature will show that many methods have been described and

used for a given analysis with varying degrees of success.

And yet, authoritative books and consultations with practlcloners

In the field Indicate that better methods are urgently needed.

Part of the explanation of the above mentioned situation

is related to the basic philosophy of air pollutant analysis.

One school takes the "Least Common Denominator" approach.

Methods should be as simple as possible, requiring a minimum

of equipment, investment, and expertise. Another segment of

technologists feel that devices similar to the familiar radiation monitor badges are needed to provide simple integrated

exposure indicators. Such devices, if simple and inexpensive,

would provide a wide base of monitoring at a "requisite level

of precision"

.

On the other hand, others demand sophisticated equipment

and are willing to pay a high price for apparatus and personnel to operate it. They feel that the high degree of reliability of the data would compensate for the problem of a more

limited number of data acquisition centers.

The presently-used methodology appears to be a balance

between these extreme points of view with simplicity playing

a dominant influential role. Environmental scientists and

engineers have been working on limited budgets and have had

to be "practical". There is no doubt that the recent Interest

in air pollution is pushing air quality standards to more

strigent limits and these will severely tax present analytical

capability. The need to continuously monitor pollutants, to

observe both short and long-term trends, and to predict

incidents is well recognized. The need to make measurements

in remote locations and to telemeter or otherwise transmit

data to control centers will forge a new technology in

pollution analysis.

87
B. State of the Art of Chemical Analysis

The general state-of-the-art of elemental analysis is much

improved in recent years. Detection limits for many of the

elements have been pushed down to parts-per-billion levels

and lower, with absolute amounts of as little as 10,000 atoms

having been reported as detectable in special situations.

Such detection limits are, of course, seldom achieved and are

perhaps unnecessary in pollution analytical applications.

However, highly sensitive methods are very desirable because

they provide the capability for short-time monitoring or

minimize the amount of sample required. Also, there is every

reason to believe that future air quality standards will be

more stringent than those of the present time. Accordingly,

the search for better and more sensitive methods is expected

to be an active area of research in the foreseeable future.

The state-of-the-art of proximate analysis, that is the

identification and determination of specific radicals or

compounds is less advanced. Detectors or sensors are often

not sufficiently sensitive to the small differences between

species present or to differentiate them from the matrix, so

that separation techniques must be used. Indeed some of the

most successful analytical techniques employ non-discriminatory

but sensitive sensors, with reliance on the known parameters

of the separator. Gas chromatography is a prime example of

such techniques. By combining more specific identification

techniques with highly efficient separation procedures.

Improved measurement techniques should result.

It would appear from analogy with other problems, that

the basic scientific knowledge is already available to solve

or ameliorate many of the analytical problems now facing

environmental science. What then is responsible for the present

relatively poor state-of-the-art of environmental analysis?

The answer for this will be found In the following discussion.
Referring back to Figure 15, this two-dimensional diagram

may be expanded In the plane of the paper to provide an almost

unlimited series of rings, each for a given analytical

situation. In fact, one can conceive of an annulus with cross

section equivalent to the ring of Figure 15 . Similar rings

could be sliced from the annulus to describe water analysis

and steel analysis, for example. Each ring would Include Its

own particular sub-units In each step, which may be common

to other rings or may be dlstlngulshably different. As a discipline (ring) stabilizes, new sub-steps are absorbed and

old ones are rejected to provide a technology consistent with

the requirements of the discipline.

The word requirement Is the key to the situation. Until

only recently, there has been little recognition of need and

hence, there has been only limited support for research to

develop analytical methods specifically suited for environmental

analysis. Rather, techniques have been borrowed from other

disciplines. Except In research establishments, measurements

predominantly have been made by technicians or by engineers

with little feel for analysis, and by the use of methods

selected largely with economic considerations In mind. Moreover, there has been little Incentive for research analysts

to enter or contribute to the field, and Instrument manufacturers have not seen a market which would stimulate the

development of sophisticated Instruments. The present concern

about the environment has now made this a glamour field and

with the availability of funding, new developments can be

expected to emerge to greatly change the situation. There are

still many problem areas and general and specific suggestions

where contributions can be made are given In a succeeding

section.

C . State of the Art of Standard Reference Materials

Standard reference materials for the evaluation of methods

or the verification of their use In a given environmental

89
analytical situation are almost nonexistent. Recognizing the

general need for such materials, the Analytical Chemistry

Division made proposals to the Office of Standard Reference flW

Materials which have resulted in two sets of standard reference

materials which are nearing completion:

Hydrocarbon in Air—4 standards:

1, lOj lOOj and 1000 ppm respectively

Carbon Monoxide in Air—6 standards:

10, 50, 100, 300, 500, and 1000 ppm respectively.

These materials should provide a means for standardizing

analytical data for these important measurements. However,

because of the limited resources available at NBS for pollution

standards work, and the fact that they were prepared in parallel

with other efforts, a period of almost two years was involved

in their certification. Obviously, a task force devoted to

such standards would be required if a significant output

would result. In addition to those mentioned above, NBS

issues several other Standard Reference Materials with air

pollution relevance. These are listed in Table 37.

A NAPCA sponsored project at NBS has been concerned with

a study of the feasibility of permeation tubes as analytical

standards for SOp determination. This work has established

the degree of confidence that can be ascribed to such devices,

and a project has now been established in the Office of

Standard Reference Materials to supply such tubes as Standard

Reference Materials early in FY 1971.

A serious obstacle to the pollutant standards program is

that the need for such materials is not generally recognized.

As a result, meaningful intercomparlson of analytical methods

is impossible, due to lack of adequate test materials. Moreover, analytical results, in compliance questions, for example,

may be subject to equivocation from two points: (1) validity

of method, and (2) validity of application.

90
Because of the nature of atmospheric analysis, the present

state-of-the-art demands that both a standard method and a standard reference material be specified. If NBS Is to

provide such materials, a way must be found to expand Its

effort In this activity above the present level.

Table 37. Standard reference materials related to

environmental analysis

SRM I6OI-I603 Carbon dioxide In nitrogen containing 308,

346, and 384 ppm CO^, respectively.

SRM 1604-1608 Containing 3, 10, 112, 212, and 978 ppm oxygen

In nitrogen, respectively.

SRM 1609 Air with oxygen content certified at atmospheric

level.

SRM 1610-1613 Containing 1, 10, 100, and 1000 ppm methane In

air, respectively.

SRM 1616-1620 Containing 10, 50, 100, 300, 500, and 1000 ppm

CO In air, respectively.

SRM 1621, 1622 Residual fuel oils, containing 1.05 and 2.14^

sulfur, respectively.

SRM 1800 Mlcrostandard Ion-exchange beads provide

elemental standards at the microgram to nanogram

level.

D. Analytical Methods for Specific Pollutants

The pollutants of the atmosphere may be classified as

gases or particulates. Actually the latter might better be

termed as aerosols since they consist of liquid droplets and

solid particles, often colloldally dispersed In the air.

The gaseous materials ordinarily determined, either

frequently or Infrequently, are listed In Table 38. The kinds

of measurements made for particulates are summarized In Table

39. Measurement of total particulates - mass per unit volume

91
of air - is most frequently made, while chemical analysis is

ordinarily reserved for selected samples.

For several years, the atmosphere has been under continuous

surveillance by NAPCA's CAMP - Continuous Air Monitoring Program. This activity consists of stations that continuously

determine the following: SO , N0„ , MO, CO, total oxidant, total

hydrocarbons, total particulates. These stations, while limited

in number, are located in places where municipal or state programs are active and with which they enjoy a degree of cooperation.

NAPCA's National Air Sampling Network collects samples

taken at about 123 stations in a systematic manner and analyzes

them at their headquarters, presently at Cincinnati. This

system appears to work reasonably well, but there would seem

to be problems concerned with stabilizing samples during the

period between collection and analysis.

Municipal air quality centers, notably in the larger

cities, have been in existence for several years. The State

of California has been very active, and there is a good

distribution of monitors throughout the state. In all of the

above, the programs have good parallelism with CAMP.

The industrial situation is sporadic. Major companies

monitor their facilities, especially their emission sources,

such as stacks for example. Many power companies analyze

their fuels or buy on tight specifications. The increased

attention being given to such activities is encouraging.

Automobile manufacturers have major engineering programs

for reduction of automotive emissions. As a consequence, they

have laboratories to measure such emissions under various

operating conditions and their findings have made important

contributions to the literature. These companies have

understandingly , been concerned about the production of smog

and several have analytical laboratories dedicated to the

study of this problem.

92

II
Table 38. Analysis of gaseous pollutants.

Frequently Determined Infrequently Determined

Oxides of sulfur - SO Hydrogen sulfide - H„S

Nitric oxide - NO Mercaptans - R-SH

Nitrogen dioxide - NO^ Hydrogen fluoride - HP

Carbon monoxide - CO Peroxyacetyl Nitrate - (PAN)

Total hydrocarbons - Aldehydes

Methane - CH^ Olefins

Total oxidants - (0^) Ammonia

Specific organic - compounds

Table 39* Particulate characterization.

Total particulates

Size distribution

Specific fraction determination

Specific element determination

Specific substance determination

The complexity of atmospheric analysis can be expected to

increase with the proposed publication by NAPCA of an impressive

number of Air Quality Criteria Documents. The expected order of

appearance of the documents is given in Table 4o. Since the

tolerance levels for many of these pollutants may be in the

range of a few micrograms-per-cubic meter, their monitoring

will involve highly sophisticated trace analysis which would

seem to be beyond the level of capability reasonably to be

expected from most of the present air quality stations.

Accordingly, a system of laboratories designed for such

determinations may be required.

93
Table 40. Expected schedule of appearance of NAPCA

air quality criteria documents.

Year Pollutants

1969 Sulfur oxides, particulates

1970 Carbon monoxide, hydrocarbons, photochemical

oxidants

1971 Fluoride, lead, nitrogen oxides, polynuclear

organics, asbestos, beryllium

1972 Chlorine, hydrogen chloride, odors, arsenic,

cadmium

1973 Copper, manganese, nickel, vanadium, zinc

197^ Barium, boron, chromium, mercury, selenium

1975 Pesticides, radioactive materials

1 . Gaseous Pollutants

The gaseous pollutants presently determined are listed in

Table 38. The methods used will be found in several easily

accessible reference works [25-28], to which the reader is

referred for details. In general, these methods are essentially

nonspecific and depend to a large extent on redox or acidimetric reactions which are colorimetrically measured.

Instrumental methods, especially electrochemical, are becoming

more popular but these, too, often suffer from interferences

so that the algebraic sum of pollutants having similar

properties is measured.

a. Sulfur Dioxide . The method of preference for

umpire determinations would appear to be the pararosaniline

(West-Gaeke) procedure which involves the formation of a redpurple pararosaniline methylsulfonic acid which is measured

colorimetrically [291. This procedure is suitable for SOp

concentrations in the range of 0.005 to 5 ppm and is very

selective but it is time consuming. However, the procedure

may be automated.

94
other methods [30] such as conductlmetry , tltrimetry,

turbidimetry , and iodimetry are in use but they lack specificity. A gas chromatographic method [1] has been recently

proposed which may be the forerunner of a new lot of specific

instrumental methods. A simple integrative method based on

the rate of sulfation of lead peroxide coated on a cylindrical

base,' and dubbed the "sulfur candle" gives ^ a measure of SO

X

exposure levels and is used in a number of countries.

b. Hydrogen Sulfide . This gas becomes an odor

nuisance at the 0.1 ppm level or less and is ordinarily

present well below this concentration. The method presently

used for its estimation consists in absorption in an alkaline

suspension of cadmium hydroxide contained in an impinger,

reaction with a mixture of p-aminodimethylaniline , ferric

chloride, and chloride ion to yield methylene blue which is

measured colorimetrically [31]. Gas chromatography is a promising technique for hydrogen sulfide determination [1].

c. Nitrogen Oxides . Nitrogen dioxide is best

measured by a method developed by Saltzman [32], based on the

Greiss-Ilosvay reaction. The N0„ is collected in the absorbini

reagent consisting of sulfanilic acid, glacial acetic acid,

and N-(l-napthyl)-ethylenediamine dihydrochloride with the

production of a pink-colored dye complex by the diazotization

reaction. The method is useful over the range from a few

parts per billion to about 5 ppm. It is also applicable to

the determination of nitric oxide, in which case it is

oxidized to NOp for subsequent determination.

The method is free from interferences from other nitrogen

compounds, and a 5-fold excess of ozone or a 10-fold excess

of SO causes negligible problems. The most serious problem

appears to be the standardization. It has been empirically

observed that 1 mole of N0„ produces the same amount of color

as 0.72 mole of sodium nitrite which ordinarily serves as the

standard; but this factor does not have universal acceptance.

95
The availability of an SRM such as a certified NOp permeation

tube would appear to be a more satisfactory method of calibration.

The method has been semi-automated with commercially

available instrumentation.

d. Ozone and Oxidants . Ozone and oxidants are

determined because they serve as indices of eye irritants and

plant-damaging pollution levels. The deleterious effects of

such oxidants on materials such as rubber, for example, are

also of importance. Oxidants are frequently determined by

iodimetric procedures in which the absorbant potassium iodide

solution is either buffered at the neutral point, or is made

alkaline to eliminate SOp interference. The latter modification provides stable containment fot* future determination

in the laboratory.

Both methods are useful in the range of a few parts per

hundred million to about 20 ppm of oxidant. Ozone, chlorine,

hydrogen peroxide, organic peroxides, and other oxidants

provide positive interferences, while reductants including

reducing dust cause low results.

Two methods [33j3^] have been recommended for determination

of total oxidants (ozone), in which the iodine produced is

electrochemically reduced. That developed by Mast (and so

called) impresses a potential across an electrolytic cell and

the amperometric current, proportional to the oxidant-produced

iodine, is measured. In the galvanic method of Hersch, the

cell is constructed so that spontaneous reduction of the

iodine occurs when the cell is shorted, and the current

measurement again is related to the oxidant content of the

sample. Such methods are essentially continuous, but suffer

from the interferences common to all iodimetric procedures.

An ozone analyzer based on the chemiluminescent reaction

of 0^ with an organic dye [1, 35] appears to be highly specific.

In this technique, a disk coated with Rhodamine B adsorbed on

silica gel is exposed to the ozone-containing air and the

96
resultant emission is detected by a phototube. The current

generated is proportional to the mass of ozone per unit time

flowing over the disk. The technique appears to be specific,

precise, and has sensitivity comparable with the methods

above described but yields significantly higher values.

Fundamental studies and better standardization techniques

would appear to be needed to clear up the -problem.

Several additional chemical methods for the determination

of ozone should be mentioned. The Bravo-Lodge technique

consists in the ozonolysis of 4-4' dimethylstilbene to produce

anisaldehyde which is determined, spectrophotometrically [36].

The chief objection to this method is that it is carried out

in a very corrosive solvent. Hauser and Bradley [37] have

described a specific ozone technique using l,2-di-(4 pyridyl)

ethylene as the absorbing medium and colorimetric analysis

of the resulting aldehyde. A trans-butene-2 gas phase titration

method has been described which involves reaction of the air

sample with this hydrocarbon. This reactive olefin selectively

removes the ozone which is determined from decrease in the

hydrocarbon concentration [38].

One of the earliest techniques used to identify ozone

in ambient air is based on the rapid cracking of stre-ssed

rubber bands [39]. This technique is useful for survey work

but is hardly quantitative.

e . Volatile Fluorides and Hydrogen Fluoride . Volatile fluorides in the atmosphere are determined by absorption of the sample in an impinger, distillation to separate the

fluoride from interferences, and measurement by a titrimetric

or spectrophotometric procedure. The same process may be

modified to determine the fluoride content of plant tissue,

for example. Direct titration can be used to determine 0.05

to 10 mg of fluoride in a total sample, while the spectrophotometric method has a detection limit of 0.015 yg of

fluoride.

97
Many ions interfere with the method but the most likely

ones are aluminum, iron, phosphate, and sulfate. Distillation,

diffusion, ion-exchange, or extraction procedures may be

required to eliminate such problems [^0].

It would appear that ion-selective electrodes would

provide improved measurement techniques for fluorides. Such

electrodes have been found to be advantageous in measurement

of corresponding fluoride levels in other substances and the

methods need only be reduced to practice in the pollution

field to be useful.

f. Carbon Monoxide . Carbon monoxide may be

determined by a method in which it reacts with an alkaline

solution of the silver salt of p-sulfaminobenzoic acid to form

a colloidal silver suspension which is measured spectrophotometrically [4l]. The minimum detectable limit is 5 ppm of CO.

Acetylene, olefins, H^S, and aldehydes in high concentration

interfere but may be removed by passage of the air through a

silica gel filter containing RgSOi,.

Carbon monoxide is widely determined by the non-dispersive

infrared method [42]. Measurements can be made with good

reliability down to 1 or 2 ppm. However, the response is

generally non-linear and carbon dioxide, water vapor, and

hydrocarbons can provide interferences.

Gas chromatography is emerging as an important tool for

CO determination and for simultaneous determination of hydrocarbons as well [43]. The method includes a catalytic reduction

system that quantitatively converts CO to CHk and a flame

ionization detector for measurement. Both CO and CE^ can be

determined between concentrations of 0.010 to 200 ppm by

suitable sequencing of the sample.

g. Hydrocarbons . Atmospheric hydrocarbons may be

determined by various gas chromatographic methods. Total

hydrocarbons can be measured with a flame ionization detector

and the result reported as a methane-equivalent. Passage of

98
the gas through a chromatographic column can be used to

separate Individual hydrocarbons for their Individual determination [44]. Hydrocarbon contents down to 0.01 ppm by volume

can be directly measured, while a freeze-trap can be employed

to concentrate the sample, thereby extending the detection

limit to 0.1 ppb.

h. Other Pollutants . Methods have been described

for a number of other gaseous pollutants Including chlorine,

hydrogen chloride, cyanides, and formaldehyde. Discussion of

these will be found In references [25-28].

1. Other Techniques . Mass spectrometry has been

used with considerable success as a research tool for air

pollution studies. Samples may be collected by a cold trap,

for example, for laboratory Investigation of pollution problems.

The analytical mass spectrometer Is unique among gas

analysis Instruments In that It has the potential ability of

performing seml-quantitatlve analyses of the total gaseous

pollutant fraction of the atmosphere. It Is probably the only

analytical Instrument which obtains a signal from every gaseous

species present In the sample. This fact, however. Is also

one of the biggest shortcomings of the method because the

amount of data received from a single unfractlonated sample

may be so great as to prevent Interpretation. Methods have

been described which either allow a fairly accurate qualitative

interpretation as to the identification of the individual

species or allow determination of the amounts of various

classes of substances. For example, it is possible to determine

what portion of the atmospheric pollution is due to traffic

gases and what portion is due to industrial pollution.

Application of special techniques and advanced instrumentation such a fractional distillation, chromatographic

separation and high resolution mass spectrometry should allow

further refinements of the technique.

99
Coulometry is another promising technique which is finding

increased use, especially in SOp determinations. It may well

be the most important means for short time-scale calibration

of SOp permeation tubes [45].

Gas chromatography has already been mentioned, and it

should be systematically studied for its applicability to

pollutant measurements. More selective detectors based on

radio-frequency excitation, for example, would appear to be

very promising and should be investigated.

The electron-impact spectrometer developed in IBS [46]

has very interesting possibilities for adaptation as a gas

analytical tool provided its sensitivity can be increased.

2 , Particulate Pollutants

Particulates may be discrete and reasonably homogeneous

pieces of matter, solid or liquid, crystalline or amorphous,

or they may be such materials on which other liquids, solids,

or gases are attached or adsorbed. Their analysis is becoming

increasingly important. The kinds of analyses required are

shown in Table 4o.

a. Dustfall and Sootfall . The amount of dust

that settles from the atmosphere is an important index of air

pollution. Most of the particles Involved will range in size

from approximately 1 to 200 ym [47] with predominance in the

upper range.

Fallout is the most obvious type of pollution, except for

odors, lacrymators, and of course, smoke. Dust is collected

in buckets over a long period of time. Care is exercised to

eliminate obvious foreign matter. For example, a bird ring

is Installed to provide a preferred spot for their inevitable

roosting with minimization of accumulation of droppings in

the bucket. Bugs are picked out, as are also leaves. The

total collection is weighed and expressed as milli2 2 grams/cm /month or tons/mile /month, e.g. It is obvious that

such methods must be standardized and the procedures generally

100
accepted if the measurements are to achieve any degree of

comparability

.

It Is often desirable to chemically analyze the dust

collected as outlined above. A simple separation into water

soluble, water insoluble, and benzene soluble fractions,

respectively, can give interesting information on the general

nature of a collection. More information can be obtained by

chemical analysis for metallic elements such as lead, cadmium,

iron, calcium, and sodium, for ^xample, and such anions as

chloride, fluoride, nitrate, carbonate, and sulfate. The

classical techniques of spectrophotometry, polarography , and

atom.ic absorption spectroscopy are generally used for the

analyses mentioned above. Spectrochemical analysis is also

used extensively. Neutron activation analysis has recently

been used for elemental analysis. Free carbon may be determined

to indicate soot fall, specific inorganic compounds or materials

such as asbestos fibers may be looked for, and specific

organic compounds may be Isolated. Biological debris such as

pollen grains may be sought although such counts are usually

made by other procedures [48],

b. Air-borne Particulates . Air-borne particulates

are collected by filtration, impaction, impingement, centrifugatlon, and electrostatic or thermal precipitation [^9]. The

particle size ranges from 0.01 ym to 100 ym with predo.minance

in the lower range [50].

Collection by filtering may use a relatively open-pored

filter of paper or fiber-glass through which the air is drawn

at a rapid rate. Such a "High-Vol" sample may be weighed as a

measure of total particulates and/or the deposit may be

analyzed as outlined below. The variability of such filters

appears to provide problems in the quantitative evaluation

of samples collected by this technique so that standard

filtering media are urgently needed [51]. Low velocity but

highly efficient filters such as Millipore, for example, may

101
be used and the collected material analyzed. Such filters

show reduced flow rates as the sampling time increases, due to ' clogging of pores, so that care needs to be exercised to measure

the total volume of air flow during a collection period. The |

use of a limiting orifice helps to provide a reasonable constant

flow during the sampling period.

Chemical analysis of filter-collected samples may be

carried out as discussed above. Because of uncertainties in

the size ranges of particles collected, the exact relation

between the analysis of a "High-Vol" sample and that of the

particulates in the atmosphere is open to question. It appears

that the removal of the sample from the filter media offers

some problems and that contamination from the filter media

must be considered.

No attempts appear to have been made to obtain complete

analyses of material collected by a "High-Vol" sampler. While

much analytical data are available, a material accountability

of only about 35 percent is ordinarily achieved [52]. Detailed

and complete compositional Information of samples systematically

collected at selected locations and at definite time intervals

will become very important as air quality standards for

particles become more specific.

Polluted air may contain a large number of organic particulate compounds, arising from incomplete combustion processes.

Secondary reactions in the air account for still additional

compounds. It is important to determine composition as a

function of size and to know whether or not specific compounds

are adsorbed or attached to other particulates. Particles in

the range of 0.2 to 3 ym are of special Interest since they

are said to be most lung damaging [53].

Organic particulates are best collected on filters since

electrostatic or thermal precipitation may alter them. Also,

impactors may shatter them or otherwise change their physical

nature. Since these materials may be bio-active, protection

102
from sun and rain during collection and from actinic light

during analysis may be required.

Analysis of organic particulate material is almost

invariably done by laboratory methods on selected samples [5^].

Microscopic or electron-microscopic examinations may be made,

followed by separation using the techniques of modern organic

analysis, such as extraction, and the chromatographic techniques

designated as thin- layer, liquid, and column, respectively.

Identification of components and their quantitative determination may be accomplished by use of mass spectrometry, gas

chromatography, NMR, and infrared or ultraviolet spectrometry.

Such techniques are costly and time-consuming so that analyses

must be restricted to special samples.

The complexities of the methodology required for organic

particulate analyses are illustrated by consideration of the

methods for determination of polynuclear aromatic hydrocarbons

assembled by the Intersociety Subcommittee and recently published [55]. In brief, the procedure consists in extraction

from the "High-Vol" fiber glass filter with benzene in a Soxhlet extractor. This organic fraction is further separated

into 30-40 sub-fractions by means of column chromatography on

alumina, using increasing amounts of diethyl ether in pentane

as the eluent . Each of these sub-fractions is dried, dissolved

in pentane, and spectrophotometrically analyzed. Fluorimetric

analysis is used in other cases. Microgram quantities of the

following compounds have been determined in this way:

anthracene; phenanthrene; f luoranthrene; pyrene; benz [a]

anthracene; chrysene; benzo [a] pyrene; benzo [e] pyrene;

perylene; benzo [g,h,i] perylene, anthanthrene; and coronene.

A complete analysis takes at least two days in the hands of an

experienced analyst.

One of the methods described in the series cited above

is a microtechnique utilizing alumina thin-layer chromatography.

About 3 ng of benzo [a] pyrene can be detected. Because of the

103
sensitivity, the laboratory air must be very clean. Cigarette

smoking cannot be allowed since it contributes heavily to the

background and lessens the sensitivity.

It is clear from the above that detailed information on

the composition of organic particulates is an exhausting task.

Accordingly, more rapid and/or automated methods are urgently

needed. The recently developed technique of liquid chromatography appears to be a promising tool for such determinations

and should be investigated.

3 . Analysis of Single Particles

The identification of single particles offers valuable

information in a number of situations. It provides important

clues to the origin of particulate contaminants, perhaps to

pinpoint an emission source. Since chemical methods provide

information on the total sample, and some size ranges are more

important than others, a gross analysis leaves many unanswered

questions

.

One of the important techniques for particle identification

is optical microscopy. Particles with a minimum dimension of

1 ym can be observed with optical microscopes. The morphology,

color, and general appearance can be very revealing to the

trained microscopist . The Particle Atlas [56] contains pictures

of literally scores of particles as observed under the microscope and is especially helpful for identification of environmental samples. The optical properties of crystalline material

offer means of determination of composition and simple counting

of selected species can provide concentration information.

Sensitive chemical tests may be made on the microscope stage

for qualitative confirmation of composition. Microscopy is

valuable for the selective removal of individual particles from

a sample for examination by other techniques.

The electron probe microanalyzer is very useful for

quantitative analysis of small samples, hence it should find

increasing use for particulate analysis. Present models have

104
beam diameters of the order of 0.3 ym and further reduction

of the beam size Is to be expected. However, It Is possible

to obtain useful signals from particles smaller than the beam

diameter If they are suitably Isolated. The Ion-probe microanalyzer has a sensitivity about 100 times greater than the

electron probe Instrument and hence, would appear to have

greatly expanded capabilities for particulate analysis.

X-ray diffraction can be used to Identify actual compounds

and phases for particulates greater than 2 ym In size. Powder

patterns of dust samples can be prepared and compared with

those of raw materials and with waste from a plant suspected of

being an emission source. It should be possible to Identify

such compounds as solid sulfates and nitrates formed In

atmospheric reactions, for example.

Mlcrochemlcal analysis has made Important advances In

recent years so that the chemical composition of single

particles. Isolated by microscopic means, can be determined

In some cases. The techniques of spectrophotometry and

electrochemistry have special promise In such analyses.

E. Summary

A review such as the present chapter, emphasizes the fact

that air pollutant analysis Is not a new field and Indeed Is

a well established science. However, the recent high Intensity

of Interest In this subject and the concern for atmospheric

Improvement Is making Increasing demands on the analytical

chemist. More stringent limits for air quality are coupled

with demands for rapid and reliable measurements at low cost.

Continuous monitoring methods tied In with data aqulsltlon

systems are also needed. These requirements can only be met

by a new breed of Instrumental techniques. However, many

of the classical methods will remain and need to be Improved

for referee or umpire analyses.

105
The fact that new and unevaluated methods are appearing

and will be used by technicians rather than trained analysts

makes two programs urgent. The first of these concerns method

evaluation to identify the superior ones as well as those that

are inferior. The National Air Pollution Control Administration

has such a program in operation to establish referee methods.

The American Society for Testing and Materials is also planning

an effort of this kind.

The second program concerns the development of a wide

variety of standard reference materials to standardize air

pollutant measurements. A modest effort in this direction is

already being made at NBS which it is proposed to expand.

Because many of the substances measured are reactive or unstable,

new concepts of standards , including means to reliably generate

such standards as needed, will have to be developed.

In the area of particulates, there is a generally expressed

need for a readily available research material that all workers

in the field may use for intercomparison of their measurements

and techniques. The National Bureau of Standards intends to

collect a large sample of particulate matter from the atmosphere,

to characterize it as fully as possible, and to make it available to environmental analysts. Such a Standard Reference

Material should do much to up-grade the science of air pollutant

analysis and aid in producing compatible analytical measurements

required to insure air quality control.

(J. K. Taylor)

106
5. PERSONNEL AND ACTIVITIES

A. Personnel Listing

John K. Taylor, Section Chief

Carolyn E. Smith, Secretary

Gas Analysis —

Ernest E. Hughes

Julian M . Ives

Gayl Silver (Guest Worker)

Polarography --

E. June Malenthal

Microscopy and Mlcrochemlstry -- Rolf A. Paulson

William P. Schmidt

B. Publications

1. J. K. Taylor, Editor, "Mlcrochemlcal Analysis Section:

Summary of Activities July I968 to June I969", NBS Technical

Note 505, October I969.

2. J. Knoeck and J. K. Taylor, "Aqueous Boric AcldBorate-Mannltol Equilibria", Anal. Chem. , 4^, 1730 (I969).

3. J. Knoeck, "Vibrational Spectrometrlc and Electrochemical Evidence for Lanthanum ( III)-Nltrate Complexes In

Aqueous Solution". Anal. Chem., 4_1, 2069 (I969).

4. D. H. Freeman, L. A. Currle, E. C. Kuehner, H. D. Dixon

and R. A. Paulson, "Development and Characterization of IonExchange Bead Mlcrostandards" , Anal. Chem. 4_2, 203 (1970).

5. L. Machta and E. E. Hughes, "Atmospheric Oxygen, I967

to 1970", Science 168_, 1582 (1970).

C. Talks

1. J. K. Taylor, "Electrochemical Methods for Trace

Analysis", Staten Island Subsection, New York Section,

American Chemical Society, Staten Island, New York, October

21, 1969.

107
2. J. K. Taylor, "Man and His Environment". Washington

Academy of Sciences, Georgetown University, October 26, I969.

3. J. K. Taylor, "Electrochemical Analysis at the National

Bureau of Standards", The Technion University, Haifa, Israel,

November 18, I969.

4. J. K. Taylor, "Electrochemical Analysis at the National

Bureau of Standards", University of Geneva, Switzerland,

November 21, I969.

5. J. K. Taylor, "Recent Advances in Electrochemical

Analysis", University of Ghent, Ghent, Belgium, November 26, I969

6. J. K. Taylor, "High Precision Coulometric Analysis",

EURATOM Central Bureau for Nuclear Measurements, Geel, Belgium,

November 27, I969.

7. J. K. Taylor, "Electrochemical Analysis at the National

Bureau of Standards", Imperial College, University of London,

London, England, November 28, I969.

8. J. K. Taylor, "High Precision Coulometric Analysis",

Atomic Energy Research Establishment, Harwell, England,

December 1, 19 69.

9. J. K. Taylor, "General Problems of Air Pollutant

Analysis", University of Florida, Gainsville, Florida,

May 6, 1970.

10. J. K. Taylor, "Relations of Electricity and Chemistry",

John F. Kennedy High School, Rockville, Maryland, October 20,

1969.

11. J. K. Taylor, "The Chemical Analysis of Air Pollutants",!

NBS-NIH Symposium, National Bureau of Standards, Gaithersburg,

Maryland, March 10, 1970.

12. J. K. Taylor, "Relations of Electricity and Chemistry",

Washington Irving Intermediate School, Springfield, Virginia,

March 18, 1970.

13. J. K. Taylor, "Relations of Electricity and Chemistry",

High Point High School, Beltsville, Maryland, April 24, 1970.

14. J. K. Taylor, "Careers in Chemistry", Central High

School, Capitol Heights, Maryland, May 15, 1970.

108
15. J. K. Taylor, "What is Chemistry?", Holy Cross

Elementary School, Garrett Park, Maryland, May 22, 1970.

16. J. K. Taylor, "State-of-the-Art of Air Pollutant

Analysis", Division 310.00 Scientific Discussion, April 8, 1970.

17. J. K. Taylor, "Standards for Air Pollution Analysis",

NAPCA Standards Advisory Committee Meeting, Berkeley,

California, April 1, 1970.

D . Committee Activities

J. K. Taylor

Service Analysis Coordinator, Analytical Chemistry Division

Member, Review Board, Science Book List, American Association

for the Advancem.ent of Science

Elected member. Council of the American Chemical Society (ACS)

Secretary, Council Committee on Chemical Education, American

Chemical Society

Member, Panel on Chemistry, Civil Service Board of Examiners

Member, Board of Managers, Chemical Society of V/ashington

Member, Advisory Committee, Laboratory Guide, American Chemical

Society

Chairman, Chemical Education Topical Group, Chemical Society

of Washington

Chairman, Chemical Education Committee, Chemical Society of

Washington

Member, ISO/TC 48 Laboratory Glassware and Related Apparatus

Member, Council, Electroanalytical Group, Society for Analytical

Chemistry

Vice Chairman, NBS Air Pollution Study Group

Member, Advisory Panel, NBS Measurements for Air Quality Program

Member, Advisory Panel, Chemical Technology Journal

Member, Visiting Committee, GSA National Laboratory

R. A. Paulson

Member, Service Analysis Committee, Analytical Chemistry

Division, NBS

109
Collaborator J Committee for Study of Microchemical Methods,

Association of Official Agricultural Chemists

W. P. Schmidt

Collaborator, Committee for Study of Microchemical Methods,

Association of Official Agricultural Chemists

Collaborator, Carbon, Hydrogen and Nitrogen Methods, Commission

on Microchemical Techniques, lUPAC

E. June Maienthal

NBS Reporter for Capital Chemist, Chemical Society of

Washington.

Editor, Analytical Chemistry Division Newsletter, NBS.

Chairman, Liaison Committee, Chemical Society of Washington

E. Award

John K. Taylor - Chemical Society of Washington

Service Award for 1969s December 11, 1969

F. Standard Reference Materials Analyses

Material

Microstandard Particles

Bilirubin

Glucose

Special Steels

SRM 1261

SRM 1264

SRM 1265

SRM 361

SRM 365

Lead-Base Bearing

Metal SRM 1132

Glass

Trace-element Standards

Orchard Leaves

Analyst Determinat ion T echnique

RAP Density M,G

Elemental Analysis

WPS Elemental Analysis M,G

Ash

RAP C1,S0^ M

EJM Bi, Pb, Te P

EJM Bi, Pb, Te P

EJM Ti P

EJM Bi, Pb, Te P

EJM Ti P

EJM Sb P

EJM Fe, Ti, Ni P

RAP;

WPS; N,P M,G

EJM Al, Bi, Fe, Pb P

110
Analyst Determinat Ion Technique

RAP;

WPS N,P M,G

WPS Purity Misc.

WPS Purity Misc.

JMI;

EEH

CH^ cont ent MS, GC.

Material

Urea Mlcrochemlcal Standard

SRM 2l4l

Borax SRM l87b

Disodlum Phosphate

SRM 18611c

Hydrocarbon In Air

SRM 1610

SRM 1611

SRM 1612

SRM 1613

Potassium Chloride

SRM , WPS Purity Misc.

Sodium Chloride WPS Purity Misc.

Key to Analysts Key to Technique

EJM - E. June Malenthal G - Gravlmetry

RAP - Rolf A. Paulson M - Mlcrochemlcal

WPS - William P. Schmidt P - Polarographic

111
6. REFERENCES

R. K. Stevens and A. E. O'Keefe, Anal. Chem. ^,

1^3A (1970).

A. E. O'Keffe and G. C. Ortmann, Anal. Chem., 38_,

760 (1966).

F. P. Scaringelll, S. A. Frey and B. E. Saltzman,

AIHA Journal No. 28, 260 (1967).

S. S. Brady and J. E. Chaney, J. Gas Chromatog. , 4_,

42 (1966).

W. B. Campbell and 0. Maass, Can: J. Res., 2, 42 (1930).

C. E. Maass and 0. Maass, JACS, 50, 1352 (1928).

Dalsaburo Murakami and Nlichiro Tokura, Bull. Chem. Soc.

Jap., 31, 431 (1958).

F. A. Cotton and G. Wilkinson, "Advanced Inorganic

Chemistry", Interscience, (I962) p. 423.

F. A. Quinn, Jr., D. E. Roberts and R. N. Work, J.

Appl. Phys., 2_2, IO85 (1951).

E. E. Hughes, Environ. Sci. Tech., 2, 201 (I968).

M. Shepherd, J. Res. NBS, 26_, 351 (1941).

J. K. Taylor, Editor, NBS Technical Note 505,

October I969.

[13] J. K. Taylor, Editor, NBS Technical Note 455,

October I968.

[14] L. Machta and E. E. Hughes, Science, 168, I582 (1970).

[15] R. Stromberg, et.al.. In preparation.

[16] F. A. Pohl, Mikrochim. Ichnoanal. Acta., I963 , 855.

[17] E. J. Maienthal and J. K. Taylor, Anal. Chem., 31,

1516 (I965).

[18] Official Methods of Analysis of the Association of

Official Agricultural Chemists, 10th. Edition, I965,

Page 744.

[19] Ibid, page 747.

[20] Al Steyermark "Quantitative Organic Microanalysis",

2nd. Edition, page 354 Academic Press I96I.

s 112

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[22] Raleigh Gilchrist, J. Res. NBS, 20, 754 (I938).

[23] J. K. Thorne, Cleveland Refractory Metals, Private

Communication.

[24] R. L. Nuttall, A. H. Laufer, M. V. Kilday, Enthalphy

of Formation of Ketene. In press.

[25] A. C. Stern, Editor, "Air Pollution", Academic Press,

New York (I968)

.

[26] M. Katz, "Measurement of Air Pollutants", World Health

Organization, Geneva, Switzerland (I969).

[27] P. L. Magill, F. R. Holdero and C. Ackley, Editors,

"Air Pollution Handbook", McGraw-Hill, New York (1956).

[28] Intersociety Methods, in Health Lab. Science, 6_,

April (1969)5 J_, January (1970).

Health Lab. Science 7, 4 (1970).

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Vol. II, p. 53, Academic Press, New York (I968).

M. S. Budd and H. H. Bewick, Anal. Chem. 24_, 1536

(1952).

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325 (I962).

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(1963).

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H. A. Bravo and J. P. Lodge, Jr., Anal. Chem., 36

,

671 (1964).

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(1967).

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[39] T. Vega and C. Seymour, J. Air Pollution Control Assoc,

11, 28 (I96I).

[40] Health Lab. Science 6, 64 (I969).

[41] Health Lab. Science 7, 75 (1970).

113
[42]

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A147 (1970).

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707 (1969).

C. E. Kuyattj Proc. Tenth Symp. of Electronics and Laser

Beam Technology, NBS (I969).

P. W. West, in "Air Pollution", A. C. Stern, Editor,

Vol. II, p. 148, Academic Press, New York (I968).

J. M. Sheldon, R. E. Lovell and K. P. Matthews, Manual

of Clinical Allergy, W. B. Saunders Co., Philadelphia,

Pennsylvania (1953).

[49] E. R. Hendrickson, in "Air Pollution", A. E. Stern,

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[50] P. W. West, in "Air Pollution", A. C. Stern, Editor,

Vol. II, p. 151, Academic Press, New York (I968).

[51] Private communication

[52] A. P. Altshuller, NAPCA, private communication.

[53] P. Kotin, Cancer Res. 16_, 375 (1956).

[54] E. Sawicki, NAPCA, private communication,

[55] Health Lab. Science, 7, 31, 45, 56, 60, 68 (1970).

[56] W. C. McCrone, R. G. Draftz and J. G. Delby, "The

Particle Atlas", Ann Arbor Publishers (I967).

114
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NBS TECHNICAL PUBLICATIONS

PERIODICALS

JOURNAL OF RESEARCH reports National Bureau of Standards research and development in

physics, mathematics, chemistry, and engineering.

Comprehensive scientific papers give complete details

of the work, including laboratory data, experimental

procedures, and theoretical and mathematical analyses. Illustrated with photographs, drawings, and

charts.

Published in three sections, available separately: • Physics and Chemistry

Papers of interest primarily to scientists working in these fields. This section covers a broad range of

physical and chemical research, with major emphasis

on standards of physical measurement, fundamental

constants, and properties of matter. Issued six times

a year. Annual subscription: Domestic, $9.50; foreign, $11.75*. • Mathematical Sciences

Studies and compilations designed mainly for the mathematician and theoretical physicist. Topics in mathematical statistics, theory of experiment design,

numerical analysis, theoretical physics and chemistry, logical design and programming of computers

and computer systems. Short numerical tables. Issued quarterly. Annual subscription: Domestic,

$5.00; foreign, $6.25*. • Engineering and Instrumentation

Reporting results of interest chiefly to the engineer

and the applied scientist. This section includes many

I of the new developments in instrumentation resulting

j from the Bureau's work in physical measurement,

II data processing, and development of test methods.

i It will also cover some of the work in acoustics,

j applied mechanics, building research, and cryogenic

engineering. Issued quarterly. Annual subscription:

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, TECHNICAL NEWS BULLETIN

The best single source of information concerning the Bureau's research, developmental, cooperative and

publication activities, this monthly publication is designed for the industry-oriented individual whose

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NONPERIODICALS

Applied Mathematics Series. Mathematical tables, manuals, and studies. Building Science Series. Research results, test methods, and performance criteria of building materials, components, systems, and structures. Handbooks. Recommended codes of engineering

and industrial practice (including safety codes) de- veloped in cooperation with interested industries,

professional organizations, and regulatory bodies. Special Publications. Proceedings of NBS conferences, bibliographies, annual reports, wall charts,

pamphlets, etc. Monographs. Major contributions to the technical

literature on various subjects related to the Bureau's

scientific and technical activities. National Standard Reference Data Series.

NSRDS provides quantitative data on the physical

and chemical properties of materials, compiled from

the world's literature and critically evaluated. Product Standards. Provide requirements for sizes, types, quality and methods for testing various industrial products. These standards are developed cooperatively with interested Government and industry groups

and provide the basis for common understanding of product characteristics for both buyers and sellers. Their use is voluntary.

Technical Notes. This series consists of communications and reports (covering both other agency and

NBS-sponsored work) of limited or transitory interest. Federal Information Processing Standards Publications. This series is the official publication within

the Federal Government for information on standards

adopted and promulgated under the Public Law

89-306, and Bureau of the Budget Circular A-86

entitled. Standardization of Data Elements and Codes

in Data Systems.

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