ARSENIC BACKUP DATA REPORT
(ID-105)
Introduction
The general procedure
for the collection and analysis of arsenic exposures is given
in OSHA Method ID-105 (6.1.). This method was evaluated in
1981-2 and concerns arsenic on mixed-cellulose
ester (MCE) filters. Collection or recovery of arsenic species
using other types of sampling media can be found in references
6.2. and 6.3.
This back-up data report consists of the
following sections:
(1) Determination of the
precision and accuracy
(2) Determination of other
metals compatible with the arsenic sample preparation
procedure
(3) Determination of the compatibility of
arsenic with the ICP digestion procedure
(4)
Determination of detection limits
(5) Conclusions
1. Precision and
Accuracy
Procedure: Quality control
samples were independently prepared in the laboratory by
using microliter spikes of arsenic-containing solutions on
MCE filters. The solutions either were prepared from arsenic
trioxide in weak solutions of nitric acid? or sodium
hydroxide/sulfuric acid. These samples were analyzed by
different chemists within the OSHA
laboratory.
Results: Previous and recent
quality control samples (6.4.) containing arsenic in the
approximate range of 0.5 to 4 times the OSHA PEL (assuming
960-L air volumes), gave the following data:
|
Sample
Set #1 |
Sample
Set #2 |
|
| Bias |
-0.024 |
+0.004 |
| CV |
0.097 |
0.10 |
| Overall
analytical error |
±21.8% |
±20.0% |
| Analysis
period |
2/1982-4/1982 |
1/1989-12/1990 |
| N |
78 |
100 |
| Analytical
technique |
HGA/D2 |
HGA/LD2 (5%)
HGA/ZL (95%) |
| Where: |
|
| HGA/D2 |
= |
Heated Graphite
Atomizer with deuterium arc background
correction |
| HGA/LD2 |
= |
Heated Graphite
Atomizer/L'vov Platform with deuterium arc
background correction. |
| HGA/ZL |
= |
Heated Graphite
Atomizer with Zeeman/L'vov
Platform |
Approximately 95% of the samples from set #2
were analyzed using the HGA Zeeman/L'vov platform approach
mentioned in this method. The remaining samples were
analyzed with a HGA/L'vov platform and deuterium arc
background correction only. A significant difference in
results was not noted.
2. Other Analytes
Compatible with the Arsenic Procedure
The
potential for analyzing other metals beside arsenic using
OSHA Method ID-105 was verified by the four experiments
discussed below. For all elements analyzed below, the
analytical parameters listed in Appendix II of the method
(6.1.) were used.
2.1. Recovery of Cd, Cu, Fe, Zn
using Sample Preparation for Arsenic
(ID-105):
Procedure: Using spiked MCE
filters, the above metals were analyzed at concentrations
of 0.5, 1, and 2 times their respective PELs (the PELs
were taken from the 29 CFR 1910.1000, Tables Z-1 and Z-2)
based on a 500-L air volume and 25-mL dilution volume.
Thirty-six samples of each metal were analyzed, twelve at
each PEL level. Of the twelve, six were digested using the
procedure listed in OSHA Method no. ID-121 (6.5.), and six
using the arsenic procedure (with nickel
spikes).
Recovery data from samples prepared using
OSHA method no. ID-121 were averaged, and the average
values were taken as the theoretical values for each
level.
Results: The analytical method
recovery (AMR), standard deviation (Std Dev) and
coefficient of variation (CV1)
is presented in Table 1 for each set of six samples
digested by the arsenic procedure.
2.2.
Interference Effects of Cd, Cu, Fe, and Zn in the Analysis
of Arsenic:
Procedure: From the above
recovery study, 15-mL aliquots of the metal solutions at 2
times the PEL were used. To each aliquot a 100 µL spike of
100 µg/mL arsenic was added. The 10-µg arsenic spike was
equivalent to 2 times the arsenic PEL (500-L air sample).
Six 15-mL aliquots of diluting solution used in the
arsenic procedure were also spiked, to be used as
controls. For each set, a 15-mL aliquot of unspiked
diluting solution was used as a blank.
All samples
were then analyzed by AAS-HGA for arsenic. Two of the
samples in each set were analyzed
twice.
Results: The analytical method
recovery (AMR), coefficient of variation (CV), and
standard deviation (Std Dev) for arsenic in the presence
of another metal is shown in Table 2.
2.3. Recovery
of Metallic Lead - Quality Control (QC)
Data:
During the period from February to April
1982, 78 lead and arsenic QC samples were analyzed. These
QC samples contained 20 to 40 µg of lead per sample. The
mean recovery for the lead analysis was 0.984, the CV was
0.041, and overall analytical error was ±9.8%. [Note:
Recent (6.4.) QC samples (from Jan. 1990 to Dec. 1990, n =
24) gave a mean recovery of 1.011, a CV of 0.091, and an
overall analytical error of ±19.3%.]
2.4. Recovery
of Pb from Lead Oxide (PbO2),
Lead Sulfate (PbSO4), and Lead
Sulfide (PbS):
Procedure: Eight samples of
each compound were weighed out, approximately 10 mg each,
into Phillips beakers. A 1,000 µg spike of arsenic from a
stock solution was added to each sample. The samples were
then digested according to the arsenic sample preparation
procedure and diluted to 100 mL. The samples were analyzed
for lead by atomic absorption using parameters listed in
Appendix II of the method (6.1.).
Results:
The recovered lead was compared to the theoretical lead
content for the particular compound as a test (AMR) of the
digestion procedure for these compounds. As shown,
recoveries were adequate using this digestion
procedure:
|
| Lead |
|
| Compound |
AMR |
Std Dev |
CV1 |
|
PbO2
PbSO4
PbS |
1.072
1.069
1.018 |
0.021
0.019
0.008 |
0.019
0.018
0.008 |
|
3. Arsenic in Samples Prepared by OSHA
Method ID-125 (6.6.)
3.1. The purpose of this experiment was
to determine if the arsenic spiked onto MCE filters could
be recovered after using the sample preparation suggested
in OSHA method ID-125 (6.6.). This is an ICP method which
used 4%
H2SO4
and 4% HCl as the acid matrix for analysis [Note: The
current ICP methods use
4%H2SO4/8%
HCl or 4% HNO3/32% HCl (6.7.,
6.8.)].
3.2. Procedure: Six filters each
were spiked at 0.1, 0.5, 1, and 2 times the OSHA PEL for
arsenic. These calculations were based on a 480-L air
sample. These filters were digested using the procedure
mentioned in reference 6.6. and then diluted to a 50-mL
solution volume. The solutions were analyzed using the
arsenic standards prepared as mentioned in Section 6.5 of
the method (6.1.). A 10-µL sample injection was used and
an overlay (10-µL injection of 1,000 µg/mL Ni solution) as
a matrix modifier was added to each sample or standard. A
Model 5100 Zeeman HGA (Perkin-Elmer, Norwalk, CT) and the
parameters mentioned in Appendix I of the method (6.1.)
were used for the arsenic analysis.
3.3.
Results: The recoveries for arsenic are shown in
Table 3. Arsenic is not lost when using the OSHA method
ID-125 digestion. In addition, arsenic in this matrix (4%
H2SO4/4%
HCl) can be analyzed using arsenic standards prepared in a
4% HNO3/200 µg/mL Ni matrix and
a Perkin-Elmer Model 5100 Zeeman HGA.
Note: After this study was performed, the ICP
digestion was changed to facilitate solubility of large
amounts of Pb. The digestion now uses 4%
H2SO4/8%
HCl (6.7.). Quality control samples analyzed using the new
acid matrix did not appear to give significantly different
results than those shown in Table 3. In addition, another
acid matrix (4% HNO3/32% HCl) is
now used to digest any samples taken from solder
operations (6.8.). This matrix has not been tested for
suitability with arsenic.
4. Detection Limits
(6.9.)
This study was undertaken to determine the
detection limit for the analysis of arsenic by AAS-HGA using
the analytical procedure and equipment mentioned in method
ID-105 (6.1.). The detection limit determination was
performed in 1990.
4.1. Dilute solutions of arsenic
were prepared by serial dilution of stock solutions as
mentioned below. Five different concentration levels were
prepared and six standard solutions at each concentration
were used. The concentrations were selected near the
assumed detection limit. Three different analyses of the
standards were performed. Two blank solutions prepared on
different dates were analyzed three times each for each
analysis.
Standard
Preparation
| Concn (µg/mL
As) |
Method of
Preparation |
|
| Blank |
Diluting Solution |
| 0.0025 |
5 mL of 0.05 µg/mL As
diluted to 100 mL |
| 0.005 |
5 mL of 0.1 µg/mL As
diluted to 100 mL |
| 0.01 |
10 mL of 0.1 µg/mL As
diluted to 100 mL |
| 0.02 |
20 mL of 0.1 µg/mL As
diluted to 100 mL |
| 0.05 |
5 mL of 1 µg/mL As
diluted to 100 mL |
The arsenic source was 1,000 µg/mL stock
solution [RICCA Chemical Company, Arlington, TX) lot
#E264, expiration date 1/24/91]. The 0.05 to 1 µg/mL
standards were prepared using serial dilution of the stock
solution. All standards were diluted with diluting
solution [Section 6.3.7. of the method
(6.1.)].
4.2. Results: Using a least-squares
regression program (linear fit and not forcing zero), the
slope for the data from each analysis was determined.
Because the solution containing the 0.0025 µg/mL As
standard was not detectable under the conditions used, its
readings were omitted from the calculations. For
calculational purposes, all absorbance readings were
multiplied by 100. The qualitative (Qual) and quantitative
(Quant) detection limits (DL) were calculated using the
International Union of Pure and Applied Chemistry (IUPAC)
method (6.10.).
Calculated Values
|
1 |
2 |
3 |
|
| Slope |
945.2991 |
1536.5812 |
1553.9398 |
| Blank Std
Dev |
1.3291601 |
1.3662601 |
1.5055453 |
| Qual DL |
0.004
µg/mL |
0.003
µg/mL |
0.003
µg/mL |
| Quant DL |
0.014
µg/mL |
0.0089
µg/mL |
0.0097
µg/mL |
Detection limits are calculated using the
following equation:
| DL =
|
(Blank
Std Dev)(k)
Slope |
| Where: |
k |
= |
3 for the Qual DL |
|
k |
= |
10 for the Quant
DL |
The average detection limits of the three
analyses using the current analytical parameters
are:
| qualitative: |
0.003 µg/mL |
| quantitative: |
0.01
µg/mL |
5. Conclusions
The evaluation
shows analytical method ID-105 to be precise and accurate,
and has sufficient sensitivity for arsenic. The experiments
in Section 3. display the capability of using OSHA ID-105
for the digestion and analysis of Cd, Cu, Fe, Pb, and Zn
along with arsenic. Arsenic is also compatible and
analyzable with other elements when using the ICP digestion
procedure found in reference 6.7.
6.
References
6.1. Occupational Safety and Health
Administration Technical Center: Arsenic in
Workplace Atmospheres (USDOL/OSHA-SLTC Method No.
ID-105). Salt Lake City, UT. Revised 1991.
6.2.
Costello, R.J., P.M. Eller, and R.D. Hull:
Measurement of Multiple Inorganic Arsenic Species. Am.
Ind. Hyg. Assoc. J. 44(1): 21-28
(1983).
6.3. Occupational Safety and Health
Administration Analytical Laboratory: As on FWSB
filters by ICP digest by C. Merrell. Salt Lake City,
UT. 1989 (unpublished).
6.4. Occupational Safety
and Health Administration Technical Center: OSHA
Laboratory Quality Control Division Data by B.
Babcock. Salt Lake City, UT. 1991
(unpublished).
6.5. Occupational Safety and
Health Administration Technical Center: Metal and
Metalloid Particulate in Workplace Atmospheres (Atomic
Absorption) (USDOL/OSHA-SLTC Method No. ID-121). Salt
Lake City, UT. Revised 1991.
6.6. Occupational
Safety and Health Administration Analytical
Laboratory: OSHA Analytical Methods Manual
(USDOL/OSHA-SLTC Method No. ID-125). Cincinnati, OH:
American Conference of Governmental Industrial Hygienists
(Publication. No. ISBN: 0-936712-66-X). 1985.
6.7.
Occupational Safety and Health Administration Technical
Center: Metal and Metalloid Particulate in
Workplace Atmospheres (ICP) by J. Septon
(USDOL/OSHA-SLCAL Method No. ID-125G). Salt Lake City, UT.
Revised 1991.
6.8. Occupational Safety and
Health Administration Technical Center: ICP
analysis of metal/metalloid particulates from solder
operations by D.C. Cook (USDOL/OSHA-SLTC Method No.
ID-206). Salt Lake City, UT. 1991.
6.9.
Occupational Safety and Health Administration Technical
Center: As Detection Limit Study by J. Rima.
Salt Lake City, UT. 1991 (unpublished).
6.10.
Long, G.L. and J.D. Winefordner: Limit of Detection
-- A Closer Look at the IUPAC Definition. Anal.
Chem. 55: 712A-724A (1983).
Table 1
Recovery of Cd, Cu, Fe,
Zn Using Arsenic Sample Preparation
|
| Metal |
PEL Level* |
AMR |
Std Dev |
CV1 |
|
Cd
Cd
Cd
Cu
Cu
Cu
Fe
Fe
Fe
Zn
Zn
Zn |
0.5
1
2
0.5
1
2
0.5
1
2
0.5
1
2 |
0.990
1.002
0.997
1.003
1.001
0.995
0.971
0.960
0.982
0.965
0.997
0.998 |
0.007
0.014
0.010
0.015
0.015
0.010
0.009
0.007
0.020
0.010
0.018
0.020 |
0.007
0.014
0.008
0.015
0.015
0.014
0.009
0.008
0.020
0.011
0.018
0.018 |
|
Table 2
Recoveries for Arsenic
in the presence of Cd, Cu, Fe, And Zn
|
| Sample set |
AMR (for arsenic) |
CV |
Std Dev |
|
Controls
Cd
(2 X PEL*)
Cu (2 X PEL*)
Fe (2 X PEL*)
Zn (2 X
PEL*) |
0.962
0.997
1.003
1.001
1.020 |
0.055
0.028
0.057
0.037
0.038 |
0.053
0.027
0.057
0.037
0.038 |
|
| AMR = Analytical
Method Recovery |
| * PEL used are
the Transitional
Limits |
Table 3
Arsenic Recoveries
Using OSHA Method No. ID-125 Digestion
|
| X PEL* |
Found
(µg/mL) |
Theor
(µg/mL) |
Found
Theor |
|
0.1
0.1
0.1
0.1
0.1
0.1
0.5
0.5
0.5
0.5
0.5
0.5
1
1
1
1
1
1
2
2
2
2
2
2 |
0.012
0.011
0.012
0.010
0.011
0.010
0.046
0.049
0.046
0.047
0.046
0.047
0.096
0.098
0.092
0.098
0.094
0.101
0.187
0.191
0.221
0.193
0.188
0.189 |
0.01
0.01
0.01
0.01
0.01
0.01
0.05
0.05
0.05
0.05
0.05
0.05
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2 |
1.200
1.100
1.200
1.000
1.100
1.000
0.920
0.980
0.920
0.940
0.920
0.940
0.960
0.980
0.920
0.980
0.940
1.010
0.935
0.955
1.105
0.965
0.940
0.945 |
Average =
1.100
Std Dev = 0.082
Average
= 0.937
Std Dev =
0.021
Average = 0.965
Std Dev
= 0.029
Average = 0.974
Std
Dev = 0.059 |
|
| * Arsenic PEL of
0.01 mg/m3. Amounts used for
spikes are calculated assuming a 480-L air sample and
50-mL dilution
volume. |
Table 4
Detection Limits -
Standard Absorbance Readings
|
-----------------------------Analysis---------------------------------- |
|
1 |
2 |
3 |
µg/mL
0.0025
0.005
0.01
0.02
0.05
Blanks
|
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
A
B
C
D
E
F
|
-0.004
0.000
0.002
0.002
-0.003
0.001
0.005
0.002
0.004
0.005
0.005
0.005
0.011
0.009
0.007
0.005
0.010
0.010
0.014
0.018
0.020
0.020
0.015
0.017
0.049
0.045
0.050
0.042
0.048
0.046
0.002
-0.001
-0.001
-0.001
-0.001
-0.001
|
-0.001
0.004
-0.001
0.006
0.001
0.001
0.010
0.008
0.009
0.010
0.007
0.005
0.016
0.019
0.016
0.017
0.012
0.016
0.029
0.033
0.029
0.033
0.031
0.027
0.078
0.077
0.080
0.075
0.079
0.075
0.000
0.000
-0.002
0.001
-0.002
0.001 |
0.000
0.000
-0.001
-0.002
-0.001
-----
0.005
0.011
0.007
0.009
0.006
0.007
0.015
0.015
0.013
0.013
0.012
-----
0.029
0.029
0.031
0.030
0.026
0.028
0.078
0.077
0.078
0.075
0.076
-----
-0.002
0.000
0.001
0.001
-0.002
-0.002
|
| The
six standards at each concentration are labeled A
through F. Two blank solutions were analyzed three times
each. |
| | |
|
|
