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Bromine

OSHA Method ID-108 Backup | Revised April 1990

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These procedures were designed and tested for internal use by OSHA personnel. Mention of any company name or commercial product does not constitute endorsement by OSHA.

Introduction

The general procedure for collection and analysis of bromine (Br2) air samples is described in OSHA method no. ID-108 (10.1). Briefly, Br2 is collected in a midget fritted glass bubbler (MFGB) containing a buffer (0.0030 M NaHCO3 / 0.0024 M Na2CO3) collection solution. In this basic solution, Br2 disproportionates to produce bromide (Br-) and bromate (BrO3-) (10.2) which can be determined by ion chromatography (IC). This method has been evaluated using 30-L, 60-min samples. The concentrations tested were near the OSHA Time Weighted Average (TWA) Permissible Exposure Limit (PEL) of 0.1 ppm.

  1. Experimental Protocol

    The evaluation consisted of the following experiments or discussions:

    • 1. Analysis of a total of 18 spiked samples.
    • 2. Analysis of a set of 18 samples which were taken from dynamically generated test atmospheres.
    • 3. Determination of the collection efficiency and the breakthrough when using MFGB.
    • 4. Storage stability tests for six samples collected at the PEL.
    • 5. Determination of the detection limit of the method.
    • 6. Comparison of methods.
    • 7. Assessment of the precision and accuracy of the method.
    • 8. Conclusions - including a discussion of changes in the PEL since this evaluation was performed.
  2. Analysis

    Samples (six samples at each of three test levels) were prepared by spiking appropriate amounts of standardized Br2 into collection solutions. The spiked samples were prepared and analyzed to determine analytical precision and accuracy.

    Procedure: Samples were prepared by adding known amounts of a standardized stock Br2 solution to 10 mL of collection solution. The spikes consisted of 17.8, 35.5, and 71.1 µg of Br2, which corresponded to about 0.5, 1, and 2 times the PEL if sampling at 0.5 L/min for 60 min.

    1. Standardization of Br2 stock solution:

      A Br2 stock solution was prepared from a Br2 permeation tube by bubbling the Br2 vapor through a collection solution for a given period of time. This stock solution was then analyzed by IC. The concentration of the stock solution was 35.57 µg/mL as Br2 (29.64 µg/mL as Br-).

    2. Three sets of spiked samples were prepared by adding 0.5, 1.0, and 2.0 mL, respectively, of the Br2 stock solution into 10-mL volumetric flasks and diluted to volume with collection solution. Each set consisted of 6 samples.
    3. The analytical procedure described in OSHA method no. ID-108 (10.1) was followed.

    Results: The results of the analytical experiment are presented in Table 1. The overall analytical recovery was 98.3% which does not indicate a need for an analytical correction factor.

  3. Sampling and Analysis

    Procedure: A standard generator [Model 350, Analytical Instrument Development Inc. (AID), Avondale, PA] containing Br2 permeation tubes (from AID) was used as the source for generating dynamic test atmospheres of Br2. A sampling manifold, constructed from glass and Teflon, was attached to the generator. Samples (6 samples at each of the three test levels) were collected from the manifold using concentrations of 0.5, 1, and 2 times the OSHA TWA PEL (0.1 ppm).

    1. The permeation rate of the Br2 permeation tubes was determined by measuring their respective weight loss at a constant temperature of 30°C ± 0.1°C over a given period of time. The permeation rates are shown in Table 2. Two different sizes of permeation tubes were used.
    2. The flow rates of the diluent air and saturated gas stream of bromine from the generator were measured with a soap bubble flow meter to determine the concentration of the generated gas.
    3. Three sets of six samples were collected individually at about 0.05, 0.1, and 0.2 ppm Br2. Samples were collected using personal sampling pumps at a sample flow rate of about 0.5 L/min for 60 min.

    Results: The results of sampling and analysis are shown in Table 3. Known (Taken) concentrations listed were calculated from the permeation tube weight loss and flows of Br2 gas and diluent air.

  4. Collection Efficiency (CE) and Breakthrough

    Procedure - CE: Two MFGBs containing 10 mL of collection solution were connected in series. Six of these series samples were collected at a concentration of 0.2 ppm for 60 min at 0.5 L/min. The amount of Br2 vapor collected in each MFGB was then measured.

    Results: The CE of the first MFGB was calculated by dividing the amount of Br2 collected in the first MFGB by the total amount of Br2 collected in the first and second MFGB. The results are reported in Table 4. The CE was 100%.

    Procedure - Breakthrough: Two MFGBs in series, as mentioned above, were prepared. Three of these series samples were taken at 0.2 ppm. A flow rate of 0.5 L/min and sampling times of 60, 120, and 240 min were used.

    Results: Breakthrough was calculated by dividing the amount of Br2 collected in the second MFGB by the total amount of Br2 collected in the first and second MFGBs. The results are given in Table 5. The breakthrough was 2.4% after 240 min.

  5. Storage Stability

    A study was conducted to assess the storage stability of collected Br2 in the collection solution.

    Procedure: Six samples were generated as described in Section 3. The samples were transferred into 10-mL volumetric flasks. These flasks were then tightly closed and stored on top of a lab bench at normal laboratory temperatures. The samples were analyzed after 1, 5, 15, and 30 day storage periods.

    Results: The results of the storage stability study are shown in Table 6. These results indicate that samples may be stored under normal laboratory conditions for a period of at least 30 days.

  6. Detection Limit

    Procedure: Samples containing small amounts of Br- were prepared in the collection solution and then analyzed by IC. The Rank Sum Test was used for the determination of the qualitative detection limit. The test is a non-parametric or a distribution-free test. The quantitative limit was determined by examining the variation (CVs) in results of these samples.

    Results: The results of the Rank Sum Test are shown in Table 7. As shown, the qualitative detection limit as Br2 is 0.02 µg/mL (99% confidence level). The quantitative limit is 0.09 µg/mL as Br2, or 0.9 µg in a 10 mL sample volume. This corresponds to 0.005 ppm Br2 for a 30-L air volume. The CV at this level was about 0.11.

  7. Analytical Method Comparison

    The previous ion specific electrode (ISE) procedure (10.3) used by OSHA was chosen as the reference analytical method to which the results of the IC method were compared.

    1. Analytical procedure for ISE (10.3)
      1. A low level ionic strength adjuster (ISA) was prepared by diluting 20 mL ISA (5 M sodium nitrate) to 100 mL with deionized water.
      2. Three sets of spiked samples were prepared by adding 5, 10, and 20 mL, respectively, of Br2 stock solution, 1 mL of ISA, and 50 µL of concentrated nitric acid into 100-mL volumetric flasks and then diluting to volume with collection solution. These samples corresponded to 1.78, 3.56, and 7.11 µg/mL Br- and were compared to those samples prepared in Section 2.2.
      3. Two different concentrations of Br- standards were prepared from potassium bromide to check the slope (-58.0 mV) of the ISE.
      4. Samples were analyzed using an Orion model 94-35A specific ion electrode and an Orion Model 901 millivolt meter.
    2. Results: The comparison data of the ISE reference and IC methods are shown in Table 8.
    3. Discussion: In basic solution, Br2 disproportionates to produce Br- and BrO3- according to the following equation (10.2):

      3Br2 + 6OH- ----> 5Br- + BrO3- + 3H2O (basic solution)

      The mole ratio of Br2 per Br- is 1.2. As the pH is lowered, Br- and BrO3- may react with each other to gradually convert back to Br2 according to the following equation (10.4):

      BrO3- + 5Br- + 6H+ ----> 3Br2 + 3H2O (acidic solution)

      Results of Br2 concentration obtained from the ISE were much lower than that from the IC, which was likely due to the change in pH after nitric acid is added. Therefore, results obtained from IC analysis are more accurate and reliable than ISE results.

  8. Precision and Accuracy

    The data, based on the NIOSH statistical protocol (10.5), are presented in Tables 1 and 3. The pooled coefficients of variation for spiked (CV1 [pooled]) and generated (CV2 [pooled]) samples and the overall CVT (pooled) are:

    CV1 (pooled) = 0.040, CV2 (pooled) = 0.065, CVT (pooled) = 0.067

    The bias was -0.056 and overall error was ±19%. Overall error was calculated as:
    OEi = ± [|mean biasi| + 2CVi] x 100%
    where i is the respective sample pool being examined.

  9. Conclusions

    The analytical, sampling and analytical, collection efficiency, breakthrough, storage stability, and detection limit experiments displayed acceptable data. A negative bias was noted for the sampling and analysis experiment conducted at two times the TWA PEL; however, the collection efficiency experiment at this concentration indicated no Br2 was passing into the next bubbler.

    The MFGB sampling and IC analytical method for Br2 has shown to be an acceptable alternative to determining compliance with the OSHA PEL of 0.1 ppm (TWA). The ability of the method to determine compliance to the STEL of 0.3 ppm Br2 is dependent on the detection limit and potential breakthrough at this concentration. A detection limit of 0.9 µg or 0.018 ppm Br2 (15-min sample, 7.5-L total air volume) is more than adequate for STEL measurements. Breakthrough was not evident at 60 to 120 min and was only 2.4% at a 240-min sampling time (0.2 ppm concentration). Breakthrough is not expected to occur at 0.3 ppm for a 15-min sampling time. Therefore, it is recommended to sample for TWA or STEL samples at 0.5 L/min as demonstrated in this method.

  10. References
    1. Occupational Safety and Health Administration Technical Center: Bromine in Workplace Atmospheres
      by J. Ku (USDOL/OSHA-SLTC Method No. ID-108). Salt Lake City, UT. Revised 1990.
    2. Cotton, F.A. and G. Wilkinson: Advanced Inorganic Chemistry -- A Comprehensive Text. 2nd rev. ed.
      New York: Interscience Publishers, 1966. pp. 569-570.
    3. Orion Research Incorporated: Instruction Manual, Halide Electrodes, Model 94-35. Cambridge, MA:
      Orion Research Incorporated, 1982.
    4. Blaedel, W.J. and V.W. Meloche: Elemental Quantitative Analysis -- Theory and Practice. 2nd ed. New
      York: Harper and Row, Publishers, 1963. p. 854.
    5. National Institute for Occupational Safety and Health: Documentation of the NIOSH Validation Tests
      by D. Taylor, R. Kupel and J. Bryant (DHEW/NIOSH Pub. No. 77-185). Cincinnati, OH: National Institute for Occupational Safety and Health, 1977.

 

Table 1
Analysis - Bromine

-------- 0.5 x PEL* --------

--------- 1 x PEL* ---------

--------- 2 x PEL* ---------

µg**
Taken

µg
Found

AMR

µg**
Taken

µg
Found

AMR

µg**
Taken

µg
Found

AMR

17.8

18.9

1.062

35.5

34.2

0.963

71.1

73.4

1.032

17.8

19.3

1.084

35.5

33.6

0.946

71.1

72.5

1.020

17.8

17.2

0.966

35.5

33.0

0.930

71.1

72.5

1.020

17.8

17.0

0.955

35.5

33.8

0.952

71.1

69.8

0.982

17.8

16.6

0.933

35.5

34.5

0.972

71.1

69.8

0.982

17.8

17.0

0.955

35.5

33.8

0.952

71.1

69.6

0.979

 
N

6

6

6

Mean

0.993

0.953

1.003

Std Dev

0.064

0.014

0.024

CV1

0.064

0.015

0.024

 

CV1 (pooled) = 0.040 * TWA PEL of 0.1 ppm ** µg Found and Taken are reported as Br2 AMR = Analytical Method Recovery = µg Found/µg Taken

 

Table 2
Permeation Rates for Bromine Tubes at 30°C

Tube Size

Time Elapsed
(min)

Weight Loss
(µg)

Permeation Rate
(µg/min)

Large

20,080

36,080

1.797

Large

13,260

24,150

1.821

Large

44,643

79,940

1.793

Small

44,644

38,980

0.873

 

The average large-size tube permeation rate for Br2 was 1.803 µg/min.

The small-size tube permeation rate for Br2 was 0.873 µg/min.

 

Table 3
Sampling and Analysis - Bromine

Test Level

------------------------ Found ----------------------

Taken

 

µg

L Air

mg/m3

ppm

ppm

Recovery (%)

0.5 x PEL

6.2

20.6

0.301

0.046

0.052

88.5

 

11.9

41.8

0.285

0.044

0.052

84.6

 

15.5

42.4

0.366

0.056

0.052

107.7

 

13.1

36.4

0.360

0.055

0.052

105.8

 

12.5

37.7

0.332

0.051

0.052

98.1

 

11.5

35.8

0.321

0.049

0.052

94.2

 
  N

6

 
  Mean

0.050

 

96.5

  Std Dev

0.005

 
  CV2

0.100

 
 
1 X PEL

18.5

27.9

0.663

0.101

0.107

94.4

 

18.9

27.2

0.695

0.106

0.107

99.1

 

21.7

30.4

0.714

0.109

0.107

101.9

 

22.2

28.6

0.776

0.119

0.107

111.2

 

20.8

28.6

0.727

0.111

0.107

103.7

 

20.8

29.5

0.705

0.108

0.107

100.9

 
  N

6

 
  Mean

0.109

 

101.6

  Std Dev

0.006

 
  CV2

0.055

 
 
2 x PEL

51.1

45.8

1.116

0.171

0.205

83.4

 

51.1

46.2

1.106

0.169

0.205

82.4

 

51.1

45.5

1.173

0.179

0.205

87.3

 

51.1

46.2

1.106

0.169

0.205

82.4

 

53.4

46.2

1.156

0.177

0.205

86.3

 

50.2

43.4

1.157

0.177

0.205

86.3

 
  N

6

 
  Mean

0.172

 

84.7

  Std Dev

0.004

 
  CV2

0.023

 
 
Results are reported as Br2
CV2 (pooled)

=   0.065

CVT (pooled)

=   0.067

Bias

=   -0.056

 
Overall Error

=   ±19%

 

 

Table 4
Collection Efficiency - Bromine

Sample No.

ppm found
lst Bubbler

ppm found
2nd bubbler

Collection
Efficiency (%)

1

0.171

ND

100.0

2

0.169

ND

100.0

3

0.172

ND

100.0

4

0.169

ND

100.0

5

0.177

ND

100.0

6

0.175

ND

100.0

7

0.177

ND

100.0

 

Average

100.0%

 

ND   =   0.02 µg/mL or 0.001 ppm (30 L air volume)

 

Table 5
Breakthrough - Bromine

Sampling
Time, min

µg found
lst bubbler

µg found
2nd bubbler

% Breakthrough

60

39.4

ND

0

120

76.2

ND

0

240

140

3.3

2.4

 

ND = 0.02 µg/mL

 

Table 6
Stability Test - Bromine

 

----------------------- Found ---------------------

Taken

Sample No.

µg

L Air

mg/m3

ppm

ppm

% Recovery

1 Day

 

1

18.500

27.900

0.663

0.101

0.107

94.4

2

18.900

27.200

0.695

0.106

0.107

99.1

3

21.700

30.400

0.714

0.109

0.107

101.9

4

22.200

28.600

0.776

0.119

0.107

111.2

5

20.800

28.600

0.727

0.111

0.107

103.7

6

20.800

29.500

0.705

0.108

0.107

100.9

 

  N

6

 
  Mean

0.109

 

101.9

  Std Dev

0.006

 
  CV

0.055

 

 

5 Days

 

1

18.800

27.900

0.674

0.103

0.107

96.3

2

19.300

27.200

0.710

0.109

0.107

101.9

3

21.600

30.400

0.711

0.109

0.107

101.9

4

22.100

28.600

0.773

0.118

0.107

110.3

5

22.100

28.600

0.77

0.118

0.107

110.3

6

21.600

29.500

0.732

0.112

0.107

104.7

 

  N

6

 
  Mean

0.112

 

104.2

  Std Dev

0.006

 
  CV

0.054

 

 

15 Days

 

1

18.100

27.900

0.649

0.099

0.107

92.5

2

18.500

27.200

0.680

0.104

0.107

97.2

3

20.500

30.400

0.674

0.103

0.107

96.3

4

22.100

28.600

0.773

0.118

0.107

110.3

5

20.900

28.600

0.731

0.112

0.107

104.7

6

21.300

29.500

0.722

0.110

0.107

102.9

 

  N

6

 
  Mean

0.108

 

100.7

  Std Dev

0.007

 
  CV

0.065

 

 

30 Days

 

1

15.300

27.900

0.548

0.084

0.107

78.5

2

15,700

27.200

0.577

0.088

0.107

82.2

3

17.400

30.400

0.572

0.088

0.107

82.2

4

19.800

28.600

0.692

0.106

0.107

99.1

5

19.100

28.600

0.668

0.102

0.107

95.3

6

19.900

29.500

0.675

0.103

0.107

96.3

 

  N

6

 
  Mean

0.095

 

88.9

  Std Dev

0.010

 
  CV

0.105

 
 

All results are reported as Br2

 

Table 7
Bromine Detection Limit - Rank Sum Test (Nstandard = Nblank = 6)

Rank

                0.02 µg/mL*

1

                0 RB1

2

                0 RB1

3

                0 RB1

4

                0 RB1

5

                0 RB1

6

                RB1

7

                33552 Std

8

                39064 Std

9

                41328 Std

10

                49403 Std

11

                52619 Std

12

                84583 Std
 
Rb =   21
Confidence Level =   99.99%
Detection Limit =   0.02 µg/mL as Br2
* Measured by peak areas
RB1 =   Reagent Blank
Std =   Standard, 0.02 µg/mL (as Br2)

Standards having a concentration of 0.01 µg/mL (as Br2) gave no response.

 

Table 8
Comparison of Analytical Methods for BromineIon Specific Electrode vs. Ion Chromatography

 

Ion Specific Electrode

-Ion Chromatography--

µg taken

µg found

AMR

µg found

AMR

0.5 x PEL*

 

17.8

16.4

0.921

18.9

1.062

17.8

16.6

0.933

19.3

1.084

17.8

16.4

0.921

17.2

0.966

17.8

16.9

0.949

17.0

0.955

17.8

16.8

0.944

16.6

0.933

17.8

17.4

0.978

17.0

0.955

 
  N

6

 

6

  Mean

0.941

 

0.993

  Std Dev

0.021

 

0.064

  CV

0.023

 

0.064

1 x PEL*

 

35.5

32.0

0.901

34.2

0.963

35.5

31.8

0.896

33.6

0.946

35.5

31.9

0.899

33.0

0.930

35.5

29.5

0.831

33.8

0.952

35.5

28.4

0.800

34.5

0.972

35.5

30.0

0.845

33.8

0.952

 
  N

6

 

6

  Mean

0.862

 

0.953

  Std Dev

0.043

 

0.014

  CV

0.050

 

0.015

2 x PEL*

 

71.1

58.3

0.820

73.4

1.032

71.1

57.8

0.813

72.5

1.020

71.1

57.8

0.813

72.5

1.020

71.1

57.7

0.812

69.8

0.982

71.1

57.6

0.810

69.8

0.982

71.1

57.7

0.812

69.6

0.979

 
  N

6

 

6

  Mean

0.813

 

1.003

  Std Dev

0.003

 

0.024

  CV

0.004

 

0.024

 
All results are reported as Br2
AMR   =   Analytical Method Recovery   =   µg taken/µg found
* TWA PEL of 0.1 ppm
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