NBSIR 74-439

Preparation of Reference Materials for

Stationary Source Emission Analysis:

Beryllium

T. C. Rams. C. D. Olson, R. A. Velapoldi. S. A. Wicks, 0. Menis.

and J. K. Taylor

National Bureau of Standards

Department of Commerce

Washington, D. C. 20234

March 1974

Final Report

Prepared for The Environmental Protection Agency

Office of Research and Monitoring

Research Triangle Park. North Carolina 27711

NBSIR 73-439

PREPARATION OF REFERENCE MATERIALS FOR

STATIONARY SOURCE EMISSION ANALYSIS:

BERYLLIUM

T. C. Rains, C. D. Olson, R. A. Velapoldi, S. A. Wicks, 0. Menis,

and J. K. Taylor

National Bureau of Standards

Department of Commerce

Washington, D. C. 20234

March 1974

Final Report

Prepared for The Environmental Protection Agency

Office of Research and Monitoring

Research Triangle Park, North Carolina 27711

U. S. DEPARTMENT OF COMMERCE. Frederick B. Dent. Secretary

NATIONAL BUREAU OF STANDARDS, Richard w. Roberts. Director

Preparation of Reference Materials for

Stationary Source Emission Analysis: Beryllium

ABSTRACT

Techniques are described for the preparation of

reference materials useful for evaluating the accuracy

and precision of analytical methods for measurement of

beryllium emissions from stationary sources. These

reference materials consist of membrane filters upon

which are deposited microgram quantities of high-fired

beryllium oxide and ampoules containing soluble beryllium

and suspended beryllium oxide. Methods for measurement

of the beryllium content of such materials by atomic

absorption spectrometry and by spectrofluorimetry

are described.

1. INTRODUCTION

This report describes work done to prepare reference

materials for evaluating analytical methods in the measurement of beryllium emissions from stationary sources. In

National Emission Standards for Hazardous Air Pollutants (1)

,

beryllium is identified as a hazardous material and a reference method, Method 104, is designated for its measurement. A specific objective of the work described in the

present report is to provide reference materials for use in the

evaluation of Method 104 by collaborative interlaborat ory testing.

In Method 104, beryllium emissions are i sokine tically

sampled from the source and the collected sample is digested

in an acid solution and analyzed by atomic absorption spectrometry. A sampling train containing both a filter and liquid

impingers is used. The critical steps that affect the accuracy

and precision of the analysis are considered to be the calibration of the atomic absorption instrument, the dissolution

of the particulate material, and the measurement of the resulting solutions. It was decided that three types of reference

samples were needed, namely a filter sample, a slurry representing washings from a probe, and a soluble sample of beryllium. The filter sample and slurry were to be prepared from

high-fired beryllium oxide to evaluate the dissolution step
in the measurement. Three filter samples containing approximately 3, 7, and 15 ug , respectively, of the oxide were to be

prepared while similar sets of slurries and soluble samples

also were required.

2. PREPARATION OF REFERENCE MATERIALS

2 . 1 Materials Used

Samples of high-fired beryllium oxide were kindly furnished

by the National Beryllia Corporation. The material consisted

of finely ground powder with a particle size of less than 5 ym.

The analysis of the material showed a BeO assay of >99 percent.

Solutions of beryllium were prepared as described later

from high-purity beryllium metal (>99.9 percent) regularly used

in this laboratory as an analytical standard.

Water and acids, prepared in the Analytical Chemistry

Division and regularly used for trace elemental analysis, were

used for the preparation of solutions and in the confirmatory

analysis of the reference materials.

2 . 2 Preliminary Experiments

In an initial study, 40 mg of high-fired beryllium oxide

were dispersed in 200 ml of various supporting media and evaluated

for uniformity of particle size and reproducibility of sampling.

The material formed large particles or clotlets that quickly

settled to the bottom of the containing vessel in the various

supporting media. To overcome this difficulty, the samples were

treated with ultrasonic radiation which dispersed the large

particles or conglomerates. Addition of 0.5 percent gum

tragacanth was found to be beneficial in that the fine material

would remain suspended for many hours. For the final preparation of the filter reference samples, an aliquot of the suspended

BeO could be transferred to a membrane filter and dried.

For the aqueous solutions, a 0.01 percent solution of highpurity beryllium metal in 0.5 N HC1 was prepared. Dilutions

of this master stock solution were made as needed to give the

final desired concentration. The final reference samples could

be prepared by transferring an aliquot with an automatic pipet

to a 2 -ml ampoule.

2 . 3 Soluble Beryllium Reference Samples

A O.'Ol percent beryllium solution was prepared by dissolving 100 mg of high-purity metal in HC1. To prevent any

2
loss of material during dissolution, the sample was transferred

to a Teflon beaker and covered with water. Then, 5 ml of acid

was added dropwise and heated gently until solution occurred.

The solution was transferred to a liter flask and diluted to

the calibrated volume with 0.5 N HC1. Aliquots of the master

stock solution were taken to give final concentrations of 1.5,

3.8 and 8.0 ug/ml in 0.25 N HC1

The 2 -ml ampoules were washed, rinsed in distilled water

and dried in an oven. An automatic delivery pipet was adjusted

to deliver approximately 2.0 ml of solution to an ampoule. A

series of ampoules were filled to contain nominaly 3.0, 7.6

and 16 yg of beryllium, and flame sealed.

2 . 4 Particulate Beryllium Samples

Two types of particulate samples were prepared. One

consisted of the material deposited on a membrane filter. The

second consisted of a suspension of the oxide in dilute acid.

Samples of 8.1, 20.8, and 40.4 mg of high-fired beryllium

oxide were transferred to 250 ml bottles. The samples were

diluted to 50 ml with water and then treated with ultrasonic

radiation for 10 minutes.

A one percent solution of gum tragacanth was prepared by

dissolving one gram of material in warm water. To remove any

insoluble residue, the solution of gum tragacanth was filtered

under reduced pressure through quartz wool. An equal volume

f S 0 ml) of the filtered gum tragacanth was added to each slurry

of beryllium oxide and mixed thoroughly with a Teflon coated

stirring bar and a magnetic stirrer.

For the filter samples, a 100 ul aliquot was transferred

with an automatic pipet to a membrane filter, type MF-AA (mixed

ester of cellulose) 55 mm diameter, mean pore size of 0.8 ym,

white, plain and air dried. The dried samples were then transferred to plastic petri dishes to serve as containers for each

individual filter.

2 . 5 Suspended Beryllium Oxide Samples

Suspended beryllium oxide samples were prepared by transferring 100 yl of suspended particles (2.4.1) to previously

cleaned 2 -ml ampoules. Then two ml of distilled water was

added with the automated pipet, and the ampoules were flame

sealed

3. CONFIRMATORY ANALYSIS

The reference materials were analyzed by two techniques,

atomic absorption spectrometry and spectrof luorimetry

3
3 . 1 Dissolution of High- Fired Beryllium Oxide

The procedure used to dissolve the suspended solids and

filter samples was a modification of that described in the

Federal Register (1). An individual filter was removed with

tweezers from the plastic petri dish and transferred to a clean

30 ml beaker. Then 2 ml of HN0 3 , 1 ml of HC10- and 1 ml of

FJ 2 SO,( were added followed by digestion on a hot plate at approximately 80°C for 30 minutes. The temperature of the hot plate

was then increased and the samples were evaporated to 0.5 ml.

After allowing the samples to cool, the sides of the beaker

were rinsed with water and the sample was transferred to a 10-ml volumetric flask and diluted to the calibrated volume

with water.

Before transferring, each ampoule was examined. If liquid

was present in the top or neck of the ampoule, the ampoule was

tapped gently until the top was free of solution. The top was

carefully snapped from the body of the ampoule. The slurry

was transferred from the ampoule to a 30-ml beaker with a disposable Pasteur capillary pipet. To ensure a quantitative

transfer of sample, the top and body of the ampoule were rinsed

with five -0.5 ml portions of 6 N HC1. Then 2 ml of HN0 3 and

I ml of fI 2 SOit were added and the samples were digested as deser: bed above

3 . 2 Atomi c Absorbtion Spect rome tri c Analysis

The procedure used for analysis of the beryllium content

of the reference solutions is described in the following sections.

3.2.1. Preparation of Standard Solutions

Beryllium, 10.00 mg Be/ml - Dissolve l.OOOg of high-purity

beryllium metal in 25 ml of 2 N HC1 . Transfer the solution to

a 100-ml volumetric flask and cTilute to the calibrated volume

with water. Prepare appropriate dilutions from this stock solution as needed in 5 percent H 2 S0 4 .

3.2.2 Preparation of Calibration Curve and Measurement of Beryllium

Concent rat i ons

Prepare a series of standard beryllium solutions in 5 percent

II 2 SQ [t . (NOTE: The concentration of standards will depend upon

the level of beryllium in the unknown. For the 3, 8 and 16 yg

levels of beryllium, standards were prepared containing 0.2, 0.3,

4
and 0.4; 0.6, 0.8 and 1.0; 1.0, 1.5 and 2.0 yg Be/ml, respect! ve 1)

Turn on the electronics of the atomic absorption instrument

and allow the beryllium hollow-cathode lamp to warm-up for 15

minutes. Set the wavelength control to 2348 A and adjust the

output of the amplifier so that the readout is 100 percent

transmission or 0.000 absorbance. Install a 5-cm single-slot

head on the burner. Light the burner using air-acetylene gas

and then convert to a nitrous oxide -ace tylene flame using the

recommended procedure by the burner manufacturer. Adjust the

acetylene flow rate until the pink plume is 3 . 8 mm (1 1/2 in.)

in height. Nebulize water into the flame for 15 minutes to

permit the instrument and burner to stabilize. Nebulize the

highest of the three beryllium standards into the flame. Adjust

the absorbance to read 0.500 or greater using scale expansion.

Then nebulize the lower standard solutions into the flame and

record the absorbance. Nebulize water between each standard

solution. Repeat the nebulization of standards and water until

the absorbance reading for a standard solution does not deviate

by more than ±0.5 percent. Nebulize the unknown solutions and

record the absorbance. Repeat the nebulization of a standard

solution between each unknown and record the absorbance.

To check for molecular absorption or scattered radiation,

remove the beryllium hoi low- cathode lamp and insert a rhenium

hoi low- cathode lamp. Set the wavelength control to 2365 K and

adjust the output of the amplifier to read 100 percent transmission or 0.000 absorbance. (NOTE: Do not adjust burner

height, oxidant-fuel ratio, slit width or scale expansion).

Nebulize the unknown solution as well as a standard solution and

record the absorbance. Subtract the absorbance obtained at

2365 A from the values obtained at 2348 A. (NOTE: A continuum

source or a double-beam instrument with background correction

capabilities may be substituted.)

Plot on rectilinear graph paper the net absorbance of the

beryllium standard solutions as the ordinate versus the concentration of the standards, ug/ml, as the abscissa and determine

the beryllium concentration of the unknown solution. If a computer is available, determine the concentration of the

unknown samples using a least square fit on the computer.

3.2.3 Results and Discussion

The analytical results obtained by atomic absorption

spectrometry are summarized in column 3 of Table 1. Atomic

absorption spectrometry is a simple and relatively sensitive

analytical technique for the determination of beryllium.

5
The sensitivity of the method for aqueous solutions is 0.03

ug/ml/1 percent absorption. A detection limit of 0.002 ug/ml

is obtainable under ideal instrumental conditions. Extensive

studies of chemical interferences in atomic absorption have

been reported (2-6). At concentration ratios greater than

1000:1 Al , Mg and Si are reported to suppress the absorption

of beryllium. However, these interferences can be corrected

by the method of standard addition. In the presence of

mineral acids the absorbance of beryllium may be enhanced. To

eliminate this possibility, standard solutions of beryllium

were prepared in the same acid medium as the unknowns (5 percent

H2S0 4 ). Because of the high ionization potential of beryllium

(9.32 eV) , no ionization interference would be expected in a nitrous ox i de - ace ty lene flame, nor was any found in the studies

conducted

.

3 . 3 Fluor i me trie Analysis

The basic fluorimetric methodology used was a combination

of procedures reported by Kirkbright, et al (7) and Burke and

Christopher (8) .

3.3.1 Experimental Details :

A. Instrumentation : A spectrof luor imeter with excitation and

emission monochroma tor s wasused: a =373nm, X = 460 nm.

ex ' em

B. Reagents : Reagent - grade materials were used unless otherwise specified

.

1. Beryllium Standards : Dissolve 0.1000 g Be metal in

2 ml dilute HC1 (1:4, HC1:H 2 0, v:v). Care should be taken with

the dissolution since foaming occurs. Heat the solution

(~"50°C) until dissolution occurs, add 5 ml cone. HC10i+, and

continue heating the solution at elevated temperatures until

fumes of HCIO4 are observed. Quantitatively rinse the solution

into a one liter volumetric flask, add 5 ml cone. HC10 4 and

dilute to the calibrated volume, giving a Be stock solution of

100 ijg/ml in HClOi* with a pH - 1 . Dilutions are made as

necessary to give a working solution of 1 ug/ml Be in ~1 percent

HClOit. A fresh working solution is prepared daily.

_ 3 2. Stock Ligand : (Sodium 2 - hydroxy- 3 -naphthoat e , 2x10 M)

.

Dissolve 0.376 g of the free acid (2-hydroxy-3-naphthoic acid)

in a one liter volumetric flask by adding a molar equivalent of

NaOH and 950 ml H 2 0. Stir until dissolved, adjust the pH to 7.5

with dilute NaOH (or dilute HClOt* ) and dilute to the calibrated

volume. Dilute 50 ml of this stock solution to 500 ml using

dilute NaOH (pH = 7.5) to give a working solution of 2xlO" 4 M in

sodium 2-hydroxy-3-naphthoate. In the actual beryllium analysis,

a minimum of 50-fold mole excess of ligand to Be is required (7).

6
3. Buffer, pH 7.5: Dilute 50 ml cone. NH^OH to 800 ml in

a large beaker. Add acetic acid (~42 ml) until a pH of 7.5 is

obtained (use pH meter) . Transfer this solution quantitatively

to a one liter volumetric flask and dilute to the calibrated

volume with water.

4. Masking Agent : [Ca 2+ /CDTA (1 , 2 -diaminocyclohexanetetraacetic ac id) J

a. Add 3.7 g Ca_(OH) 2 to 450 ml H 2 0 and 2 ml HC10, and

stir until dissolved. Adjust the pH to 5.0 with dilute HCIO^

(pH meter) and dilute to 500 ml yielding a solution that is

10" X M in Ca 2

.

b. Add dilute NaOH to 6.925 g CDTA and 150 ml H 2 0

in a 200 ml volumetric flask until CDTA dissolves and a pH

of 7.5 is obtained. Dilute to the calibrated volume giving

a solution that is 10" l M in CDTA.

c. [Ca 2+ /CDTA]: Add 125 ml Ca

2+ solution to 30 ml

CDTA solution in a 500 ml volumetric flask and dilute to the

calibrated volume with water.

5. pH Indicator, pH Range 7-8 : Prepare a 0.01 - 0.1 percent phenol red solution in ethanol. Place in a dropping bottle.

3.3.2 Procedure : Take appropriate sample volumes such that the

amount oi Be in this volume is between 0.1 and 0.2 ug. Prepare

calibration standards at the 0.10, 0.15 and 0.20 g Be levels

in the same manner as the sample. (Add an equivalent amount of

acid that will make the standards and the sample equivalent in

solvent acidity.) Dilute to ~70 ml with water. In the analytical procedure, run the standards, blank, samples and standards

in that order.

Add 5 ml Ca

2+ /CDTA solution and 2 drops (~0.1 ml) phenol

red indicator solution to the ~70 ml of samples or standards

from the pre-analysis preparation and shake for 5 s. Adjust

the pH to 7.5 with 6 N NH^OH (solution turns pink). Minimize

excess NH^OH so that B~e hydrolysis does not occur . Immediately

add 5 ml buffer and 5 ml ligand. Shake for 20 s, allow to

stand 5 min (timed using stopwatch) and read fluorescence

intensity using excitation wavelength of 373 nm and emission

wavelength of 460 nm. Determine unknown Be concentration by

plotting the net fluorescence intensity versus concentration

for the Be standards and interpolating the values for the

unknown Be samples. The analytical values obtained by

spectrof luor imetr ic analysis are summarized in column 4 of

Table 1.

7
4 . SUMMARY

Three types of reference materials have been prepared in

this investigation, each type providing three levels of

beryllium content. The samples are believed to simulate

typical samples obtained during measurement of beryllium from

a stationary source.

The samples are identified as follows:

Identification No. Type

0

- - 050 Filter, blank

100 - - 150 Filter

,

BeO

200 - 250 Filter, BeO

300 - 350 Filter, BeO

400 -

- 450 Ampoule

,

suspended BeO

500 -

• 550 Ampoule

,

suspended BeO

600 - 650 Ampoule

,

suspended BeO

700 -• 750 Ampoule

,

soluble Be in 0. 25 M HC1

800 - 850 Ampoule

,

soluble Be in 0. 25 M HC1

900 -• 950 Ampoule

,

soluble Be in 0. 25 M HC1

Each filter should be treated as an individual sample and

should be used in its entirety. Solution may be achieved by

dissolving in HNO3, HC10i» , and H^SO^. as described in the

Federal Register (1) (See also Section 3.1 of this report).

Ampoule samples should also be used in their entirety and

treated in the following manner. Each ampoule is prescored.

Check to see if the top or neck is free of solution. If liquid

is present in this portion, shake or gently tap the ampoule

until the top is free of solution. Then, gently snap the top

from the body. Transfer the sample (slurry or solution) to a beaker or volumetric flask, using a disposable Pasteur Capillary

pipet. Rinse the ampoule with mineral acid and proceed with

the analysis.

The analytical results obtained by the two measurement

techniques are summarized in Table 1. Each analyst took care

to optimize his calibrations and measurements. The standard

deviations tabulated represent both the analytical error and

any inhomogeneity of the samples.

The results obtained by the two techniques are in agreement

within the 95 percent confidence interval for each. The somewhat larger standard deviations found for the fluorimetric

measurements are probably due to the extra chemical steps

involved in this procedure. The experimental problems can be

minimized and research is in progress to improve this method.

8
After consideration of the measurement problems concerned

with each technique, the results obtained by atomic absorption

spectrometry are recommended as the assay levels for the

reference samples. The fluorimetric measurements are considered

to be confirmation of these values and provide an independent

check for any systematic bias.

5. REFERENCES

1. Federal Register, Vol. 38, No. 66, Friday, April 6, 1973,

pp 8820-8850.

2. B. Fleet, K. V. Liberty, and T. S. West, Talanta, 17,

203 (1970).

3. W. T. Elwell and J. A. G. Gidley, Atomic Absorption

Spectrometry , 2nd ed., Pergamon Press , Oxford , 1966.

4. M. D. Amos and J. B. Willis, Spectrochim. Acta, 2_2, 1325

(1966).

5. T. V. Ramakrishna, P. W. West, and J. W. Robinson, Anal.

Chim. Acta, 3^, 81 (1967)

.

6. J. A. Dean and T. C. Rains, eds., Flame Emission and

Atomic Absorption Spectrometry , VoT! 3, Applications,

Dekker , New York, 1974 (in press)

.

7. G. F. Kirkbright, T. S. West and C. Woodward, Anal. Chem.

31 , 137 (1965) .

8. R. W. Burke and D. Christopher, NBS Tech. Note 454 (1968).

9
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NBS-1 14A (rev. 7-73)

U.S. DEPT. OF COMM. j. PUBLICATION OR REPORT NO. 2. Gov't Accession

BIBLIOGRAPHIC DATA No sheet NBSIR 74-439

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Preparation of Reference Materials for Stationary

Source Emission Analysis: Beryllium

5. Publication Date March 1974

6. Performing Organization Code

7- AUTH0R(S) T. C. Rains, CD. Olson, R. A. Velapoldi, —— S.A. Wicks. 0. Menis. and J.K. Taylor 1

8. Performine Organ. Report No. NBSIR 74-439

9. PERFORMING ORGANIZATION NAME AND ADDRESS 7

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

The F.nvi rorm^nf ?1 pTntprt i on Aupti rv Division of Atmospheric Surveilance

Research Triangle Park, N.C. 27711

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less {actual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) Techniques are described for the preparation of reference materials

useful for evaluating the accuracy and precision of analytical methods

for measurement of beryllium emissions from stationary sources. These

reference materials consist of membrane filters upon which are deposited

microgram quantities of high-fired beryllium oxide and ampoules containing soluble beryllium and suspended beryllium oxide. Methods for

measurement of the beryllium content of such materials by atomic

absorption spectrometry and by spectrofluorimetry are described.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Air pollution; atomic absorption spectrometry; beryllium; chemical

analysis; fluorimetric analysis.

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