WAC 296-62-07449
Appendix E -- Cadmium in workplace
atmospheres.
Method number: ID-189 (OSHA); (ICP/MS) 0009 (WISHA)
Matrix: Air
WISHA permissible exposure limits: 5 µg/m3 (TWA), 2.5
µg/m3 (action level TWA)
Collection procedure: A known volume of air is drawn
through a 37-mm diameter filter cassette containing a 0.8 µm
mixed cellulose ester membrane filter (MCEF).
Recommended air volume: 960 L
Recommended sampling rate: 2.0 L/min
Analytical procedure: Air filter samples are digested
with nitric acid. After digestion, a small amount of
hydrochloric acid is added. The samples are then diluted to
volume with deionized water and analyzed by either flame
atomic absorption spectroscopy (AAS) or flameless atomic
absorption spectroscopy using a heated graphite furnace
atomizer (AAS-HGA).
Detection limits:
Qualitative: 0.2 µg/m3 for a 200 L sample by Flame AAS,
0.007 µg/m3 for a 60 L sample by AAS-HGA
Quantitative: 0.70 µg/m3 for a 200 L sample by Flame AAS,
0.025 µg/m3 for a 60 L sample by AAS-HGA
Precision and accuracy: (Flame AAS Analysis and AAS-HGA
Analysis):
Validation level: 2.5 to 10 µg/m3 for a 400 L air vol,
1.25 to 5.0 µg/m3 for a 60 L air vol CV1 (pooled): 0.010,
0.043
Analytical bias: +4.0%, -5.8%
Overall analytical error: ±6.0%, ±14.2%
Method classification: Validated Date: June, 1992
Inorganic Service Branch II, OSHA Salt Lake Technical
Center, Salt Lake City, Utah Commercial manufacturers and
products mentioned in this method are for descriptive use only
and do not constitute endorsements by USDOL-OSHA. Similar
products from other sources can be substituted.
(1) Introduction.
(a) Scope.
This method describes the collection of airborne
elemental cadmium and cadmium compounds on 0.8 µm mixed
cellulose ester membrane filters and their subsequent analysis
by either flame atomic absorption spectroscopy (AAS) or
flameless atomic absorption spectroscopy using a heated
graphite furnace atomizer (AAS-HGA). It is applicable for
both TWA and action level TWA permissible exposure level (PEL)
measurements. The two atomic absorption analytical techniques
included in the method do not differentiate between cadmium
fume and cadmium dust samples. They also do not differentiate
between elemental cadmium and its compounds.
(b) Principle.
Airborne elemental cadmium and cadmium compounds are
collected on a 0.8 µm mixed cellulose ester membrane filter
(MCEF). The air filter samples are digested with concentrated
nitric acid to destroy the organic matrix and dissolve the
cadmium analytes. After digestion, a small amount of
concentrated hydrochloric acid is added to help dissolve other
metals which may be present. The samples are diluted to
volume with deionized water and then aspirated into the
oxidizing air/acetylene flame of an atomic absorption
spectrophotometer for analysis of elemental cadmium. If the
concentration of cadmium in a sample solution is too low for
quantitation by this flame AAS analytical technique, and the
sample is to be averaged with other samples for TWA
calculations, aliquots of the sample and a matrix modifier are
later injected onto a L'vov platform in a pyrolytically-coated
graphite tube of a Zeeman atomic absorption
spectrophotometer/graphite furnace assembly for analysis of
elemental cadmium. The matrix modifier is added to stabilize
the cadmium metal and minimize sodium chloride as an
interference during the high temperature charring step of the
analysis subsection (5)(a) and (b) of this section.
(c) History.
Previously, two OSHA sampling and analytical methods for
cadmium were used concurrently WAC 296-62-07449 (5)(c) and
(d). Both of these methods also required 0.8 µm mixed
cellulose ester membrane filters for the collection of air
samples. These cadmium air filter samples were analyzed by
either flame atomic absorption spectroscopy (subsection (5)(c)
of this section) or inductively coupled plasma/atomic emission
spectroscopy (ICP-AES) (subsection (5)(d) of this section). Neither of these two analytical methods have adequate
sensitivity for measuring workplace exposure to airborne
cadmium at the new lower TWA and action level TWA PEL levels
when consecutive samples are taken on one employee and the
sample results need to be averaged with other samples to
determine a single TWA. The inclusion of two atomic
absorption analytical techniques in the new sampling and
analysis method for airborne cadmium permits quantitation of
sample results over a broad range of exposure levels and
sampling periods. The flame AAS analytical technique included
in this method is similar to the previous procedure given in
the General Metals Method ID-121 (subsection (5)(c) of this
section) with some modifications. The sensitivity of the
AAS-HGA analytical technique included in this method is
adequate to measure exposure levels at 1/10 the action level
TWA, or lower, when less than full-shift samples need to be
averaged together.
(d) Properties (subsection (5)(e) of this section).
Elemental cadmium is a silver-white, blue-tinged,
lustrous metal which is easily cut with a knife. It is slowly
oxidized by moist air to form cadmium oxide. It is insoluble
in water, but reacts readily with dilute nitric acid. Some of
the physical properties and other descriptive information of
elemental cadmium are given below:
| CAS No . . . . . . . . . . . . |
7440-43-9 |
| Atomic Number . . . . . . . . . . . . |
48 |
| Atomic Symbol . . . . . . . . . . . . |
Cd |
| Atomic Weight . . . . . . . . . . . . |
112.41 |
| Melting Point . . . . . . . . . . . . |
321°C |
| Boiling Point . . . . . . . . . . . . |
765°C |
| Density . . . . . . . . . . . . |
8.65 g/mL (25°C) |
The properties of specific cadmium compounds are
described in reference subsection (5)(e) of this section.
(e) Method performance.
A synopsis of method performance is presented below. Further information can be found in subsection (4) of this
section.
(i) The qualitative and quantitative detection limits for
the flame AAS analytical technique are 0.04 µg (0.004 µg/mL)
and 0.14 µg (0.014 µg/mL) cadmium, respectively, for a 10 mL
solution volume. These correspond, respectively, to 0.2 µg/m3
and 0.70 µg/m3 for a 200 L air volume.
(ii) The qualitative and quantitative detection limits
for the AAS-HGA analytical technique are 0.44 ng (0.044 ng/mL)
and 1.5 ng (0.15 ng/mL) cadmium, respectively, for a 10 mL
solution volume. These correspond, respectively, to 0.007
µg/m3 and 0.025 µg/m3 for a 60 L air volume.
(iii) The average recovery by the flame AAS analytical
technique of 17 spiked MCEF samples containing cadmium in the
range of 0.5 to 2.0 times the TWA target concentration of 5
µg/m3 (assuming a 400 L air volume) was 104.0% with a pooled
coefficient of variation (CV1) of 0.010. The flame analytical
technique exhibited a positive bias of +4.0% for the validated
concentration range. The overall analytical error (OAE) for
the flame AAS analytical technique was ±6.0%.
(iv) The average recovery by the AAS-HGA analytical
technique of 18 spiked MCEF samples containing cadmium in the
range of 0.5 to 2.0 times the action level TWA target
concentration of 2.5 µg/m3 (assuming a 60 L air volume) was
94.2% with a pooled coefficient of variation (CV1) of 0.043. The AAS-HGA analytical technique exhibited a negative bias of
-5.8% for the validated concentration range. The overall
analytical error (OAE) for the AAS-HGA analytical technique
was ±14.2%.
(v) Sensitivity in flame atomic absorption is defined as
the characteristic concentration of an element required to
produce a signal of 1% absorbance (0.0044 absorbance units). Sensitivity values are listed for each element by the atomic
absorption spectrophotometer manufacturer and have proved to
be a very valuable diagnostic tool to determine if
instrumental parameters are optimized and if the instrument is
performing up to specification. The sensitivity of the
spectrophotometer used in the validation of the flame AAS
analytical technique agreed with the manufacturer
specifications (subsection (5)(f) of this section); the 2
µg/mL cadmium standard gave an absorbance reading of 0.350
abs. units.
(vi) Sensitivity in graphite furnace atomic absorption is
defined in terms of the characteristic mass, the number of
picograms required to give an integrated absorbance value of
0.0044 absorbance-second (subsection (5)(g) of this section). Data suggests that under stabilized temperature platform
furnace (STPF) conditions (see (f)(ii) of this subsection),
characteristic mass values are transferable between properly
functioning instruments to an accuracy of about twenty percent
(subsection (5)(b) of this section). The characteristic mass
for STPF analysis of cadmium with Zeeman background correction
listed by the manufacturer of the instrument used in the
validation of the AAS-HGA analytical technique was 0.35 pg. The experimental characteristic mass value observed during the
determination of the working range and detection limits of the
AAS-HGA analytical technique was 0.41 pg.
(f) Interferences.
(i) High concentrations of silicate interfere in
determining cadmium by flame AAS (subsection (5)(f) of this
section). However, silicates are not significantly soluble in
the acid matrix used to prepare the samples.
(ii) Interferences, such as background absorption, are
reduced to a minimum in the AAS-HGA analytical technique by
taking full advantage of the stabilized temperature platform
furnace (STPF) concept. STPF includes all of the following
parameters (subsection (5)(b) of this section):
(A) Integrated absorbance;
(B) Fast instrument electronics and sampling frequency;
(C) Background correction;
(D) Maximum power heating;
(E) Atomization off the L'vov platform in a pyrolytically
coated graphite tube;
(F) Gas stop during atomization;
(G) Use of matrix modifiers.
(g) Toxicology (subsection (5)(n) of this section).
Information listed within this section is synopsis of
current knowledge of the physiological effects of cadmium and
is not intended to be used as the basis for WISHA policy. IARC classifies cadmium and certain of its compounds as Group
2A carcinogens (probably carcinogenic to humans). Cadmium
fume is intensely irritating to the respiratory tract. Workplace exposure to cadmium can cause both chronic and acute
effects. Acute effects include tracheobronchitis,
pneumonitis, and pulmonary edema. Chronic effects include
anemia, rhinitis/anosmia, pulmonary emphysema, proteinuria and
lung cancer. The primary target organs for chronic disease
are the kidneys (noncarcinogenic) and the lungs
(carcinogenic).
(2) Sampling.
(a) Apparatus.
(i) Filter cassette unit for air sampling: A 37-mm
diameter mixed cellulose ester membrane filter with a pore
size of 0.8 µm contained in a 37-mm polystyrene two- or
three-piece cassette filter holder (part no. MAWP 037 A0,
Millipore Corp., Bedford, MA). The filter is supported with a
cellulose backup pad. The cassette is sealed prior to use
with a shrinkable gel band.
(ii) A calibrated personal sampling pump whose flow is
determined to an accuracy of ±5% at the recommended flow rate
with the filter cassette unit in line.
(b) Procedure
(i) Attach the prepared cassette to the calibrated
sampling pump (the backup pad should face the pump) using
flexible tubing. Place the sampling device on the employee
such that air is sampled from the breathing zone.
(ii) Collect air samples at a flow rate of 2.0 L/min. If
the filter does not become overloaded, a full-shift (at least
seven hours) sample is strongly recommended for TWA and action
level TWA measurements with a maximum air volume of 960 L. If
overloading occurs, collect consecutive air samples for
shorter sampling periods to cover the full workshift.
(iii) Replace the end plugs into the filter cassettes
immediately after sampling. Record the sampling conditions.
(iv) Securely wrap each sample filter cassette end-to-end
with a sample seal.
(v) Submit at least one blank sample. With each set of
air samples. The blank sample should be handled the same as
the other samples except that no air is drawn through it.
(vi) Ship the samples to the laboratory for analysis as
soon as possible in a suitable container designed to prevent
damage in transit.
(3) Analysis.
(a) Safety precautions.
(i) Wear safety glasses, protective clothing and gloves
at all times.
(ii) Handle acid solutions with care. Handle all cadmium
samples and solutions with extra care (see subsection (1)(g)
of this section). Avoid their direct contact with work area
surfaces, eyes, skin and clothes. Flush acid solutions which
contact the skin or eyes with copious amounts of water.
(iii) Perform all acid digestions and acid dilutions in
an exhaust hood while wearing a face shield. To avoid
exposure to acid vapors, do not remove beakers containing
concentrated acid solutions from the exhaust hood until they
have returned to room temperature and have been diluted or
emptied.
(iv) Exercise care when using laboratory glassware. Do
not use chipped pipets, volumetric flasks, beakers or any
glassware with sharp edges exposed in order to avoid the
possibility of cuts or abrasions.
(v) Never pipet by mouth.
(vi) Refer to the instrument instruction manuals and SOPs
(subsection (5)(h) and (i) of this section) for proper and
safe operation of the atomic absorption spectrophotometer,
graphite furnace atomizer and associated equipment.
(vii) Because metallic elements and other toxic
substances are vaporized during AAS flame or graphite furnace
atomizer operation, it is imperative that an exhaust vent be
used. Always ensure that the exhaust system is operating
properly during instrument use.
(b) Apparatus for sample and standard preparation.
(i) Hot plate, capable of reaching 150°C, installed in an
exhaust hood.
(ii) Phillips beakers, 125 mL.
(iii) Bottles, narrow-mouth, polyethylene or glass with
leakproof caps: used for storage of standards and matrix
modifier.
(iv) Volumetric flasks, volumetric pipets, beakers and
other associated general laboratory glassware.
(v) Forceps and other associated general laboratory
equipment.
(c) Apparatus for flame AAS analysis.
(i) Atomic absorption spectrophotometer consisting of
a(an):
Nebulizer and burner head; pressure regulating devices
capable of maintaining constant oxidant and fuel pressures;
optical system capable of isolating the desired wavelength of
radiation (228.8 nm); adjustable slit; light measuring and
amplifying device; display, strip chart, or computer interface
for indicating the amount of absorbed radiation; cadmium
hollow cathode lamp or electrodeless discharge lamp (EDL) and
power supply.
(ii) Oxidant: Compressed air, filtered to remove water,
oil and other foreign substances.
(iii) Fuel: Standard commercially available tanks of
acetylene dissolved in acetone; tanks should be equipped with
flash arresters.
| Caution: |
Do not use grades of acetylene containing solvents other than acetone because they may damage the PVC tubing used in
some instruments. |
(iv) Pressure-reducing valves: Two gauge, two-stage
pressure regulators to maintain fuel and oxidant pressures
somewhat higher than the controlled operating pressures of the
instrument.
(v) Exhaust vent installed directly above the
spectrophotometer burner head.
(d) Apparatus for AAS-HGA analysis.
(i) Atomic absorption spectrophotometer consisting of
a(an):
Heated graphite furnace atomizer (HGA) with argon purge
system pressure-regulating devices capable of maintaining
constant argon purge pressure; optical system capable of
isolating the desired wavelength of radiation (228.8 nm);
adjustable slit; light measuring and amplifying device;
display, strip chart, or computer interface for indicating the
amount of absorbed radiation (as integrated absorbance, peak
area); background corrector: Zeeman or deuterium arc. The
Zeeman background corrector is recommended; cadmium hollow
cathode lamp or electrodeless discharge lamp (EDL) and power
supply; autosampler capable of accurately injecting 5 to 20 µL
sample aliquots onto the L'vov Platform in a graphite tube.
(ii) Pyrolytically coated graphite tubes containing
solid, pyrolytic L'vov platforms.
(iii) Polyethylene sample cups, 2.0 to 2.5 mL, for use
with the autosampler.
(iv) Inert purge gas for graphite furnace atomizer:
Compressed gas cylinder of purified argon.
(v) Two gauge, two-stage pressure regulator for the argon
gas cylinder.
(vi) Cooling water supply for graphite furnace atomizer.
(vii) Exhaust vent installed directly above the graphite
furnace atomizer.
(e) Reagents. All reagents should be ACS analytical
reagent grade or better.
(i) Deionized water with a specific conductance of less
than 10 µS.
(ii) Concentrated nitric acid, HNO3.
(iii) Concentrated hydrochloric acid, HCl.
(iv) Ammonium phosphate, monobasic, NH4H2PO4.
(v) Magnesium nitrate, Mg(NO3)2 • 6H2O.
(vi) Diluting solution (4% HNO3, 0.4% HCl): Add 40 mL
HNO3 and 4 mL HCl carefully to approximately 500 mL deionized
water and dilute to 1 L with deionized water.
(vii) Cadmium standard stock solution, 1,000 µg/mL: Use
a commercially available certified 1,000 µg/mL cadmium
standard or, alternatively, dissolve 1.0000 g of cadmium metal
in a minimum volume of 1:1 HCl and dilute to 1 L with 4% HNO3. Observe expiration dates of commercial standards. Properly
dispose of commercial standards with no expiration dates or
prepared standards one year after their receipt or preparation
date.
(viii) Matrix modifier for AAS-HGA analysis: Dissolve
1.0 g NH4H2PO4 and 0.15 g Mg(NO3)2 • 6H2O in approximately 200 mL
deionized water. Add 1 mL HNO3 and dilute to 500 mL with
deionized water.
(ix) Nitric Acid, 1:1 HNO3/DI H2O mixture: Carefully add
a measured volume of concentrated HNO3 to an equal volume of DI
H2O.
(x) Nitric acid, 10% v/v: Carefully add 100 mL of
concentrated HNO3 to 500 mL of DI H2O and dilute to 1 L.
(f) Glassware preparation.
(i) Clean Phillips beakers by refluxing with 1:1 nitric
acid on a hot plate in a fume hood. Thoroughly rinse with
deionized water and invert the beakers to allow them to drain
dry.
(ii) Rinse volumetric flasks and all other glassware with
10% nitric acid and deionized water prior to use.
(g) Standard preparation for flame AAS analysis.
(i) Dilute stock solutions: Prepare 1, 5, 10 and 100
µg/mL cadmium standard stock solutions by making appropriate
serial dilutions of 1,000 µg/mL cadmium standard stock
solution with the diluting solution described in (e)(vi) of
this subsection.
(ii) Working standards: Prepare cadmium working
standards in the range of 0.02 to 2.0 µg/mL by making
appropriate serial dilutions of the dilute stock solutions
with the same diluting solution. A suggested method of
preparation of the working standards is given below.
Working
standard
(µg/mL) |
Std
solution
(µg/mL) |
Aliquot
(mL) |
Final vol.
(mL) |
| 0.02 |
1 |
10 |
500 |
| 0.05 |
5 |
5 |
500 |
| 0.1 |
10 |
5 |
500 |
| 0.2 |
10 |
10 |
500 |
| 0.5 |
10 |
25 |
500 |
| 1 |
100 |
5 |
500 |
| 2 |
100 |
10 |
500 |
Store the working standards in 500-mL, narrow-mouth
polyethylene or glass bottles with leak proof caps.
Prepare every twelve months.
(h) Standard preparation for AAS-HGA analysis.
(i) Dilute stock solutions: Prepare 10, 100 and 1,000
ng/mL cadmium standard stock solutions by making appropriate
ten-fold serial dilutions of the 1,000 µg/mL cadmium standard
stock solution with the diluting solution described in (e)(vi)
of this subsection.
(ii) Working standards: Prepare cadmium working
standards in the range of 0.2 to 20 ng/mL by making
appropriate serial dilutions of the dilute stock solutions
with the same diluting solution. A suggested method of
preparation of the working standards is given below.
Working
standard
(ng/mL) |
Std
solution
(ng/mL) |
Aliquot
(mL) |
Final vol.
(mL) |
| 0.2 |
10 |
2 |
100 |
| 0.5 |
10 |
5 |
100 |
| 1 |
10 |
10 |
100 |
| 2 |
100 |
2 |
100 |
| 5 |
100 |
5 |
100 |
| 10 |
100 |
10 |
100 |
| 20 |
1,000 |
2 |
100 |
Store the working standards in narrow-mouth
polyethylene or glass bottles with leakproof caps.
Prepare monthly.
(i) Sample preparation.
(i) Carefully transfer each sample filter with forceps
from its filter cassette unit to a clean, separate 125-mL
Phillips beaker along with any loose dust found in the
cassette. Label each Phillips beaker with the appropriate
sample number.
(ii) Digest the sample by adding 5 mL of concentrated
nitric acid (HNO3) to each Phillips beaker containing an air
filter sample. Place the Phillips beakers on a hot plate in
an exhaust hood and heat the samples until approximately 0.5
mL remains. The sample solution in each Phillips beaker
should become clear. If it is not clear, digest the sample
with another portion of concentrated nitric acid.
(iii) After completing the HNO3 digestion and cooling the
samples, add 40 µL (2 drops) of concentrated HCl to each air
sample solution and then swirl the contents. Carefully add
about 5 mL of deionized water by pouring it down the inside of
each beaker.
(iv) Quantitatively transfer each cooled air sample
solution from each Phillips beaker to a clean 10-mL volumetric
flask. Dilute each flask to volume with deionized water and
mix well.
(j) Flame AAS analysis.
Analyze all of the air samples for their cadmium content
by flame atomic absorption spectroscopy (AAS) according to the
instructions given below.
(i) Set up the atomic absorption spectrophotometer for
the air/acetylene flame analysis of cadmium according to the
SOP (subsection (5)(h) of this section) or the manufacturer's
operational instructions. For the source lamp, use the
cadmium hollow cathode or electrodeless discharge lamp
operated at the manufacturer's recommended rating for
continuous operation. Allow the lamp to warm up ten to twenty
minutes or until the energy output stabilizes. Optimize
conditions such as lamp position, burner head alignment, fuel
and oxidant flow rates, etc. See the SOP or specific
instrument manuals for details. Instrumental parameters for
the Perkin-Elmer Model 603 used in the validation of this
method are given in subsection (6) of this section.
(ii) Aspirate and measure the absorbance of a standard
solution of cadmium. The standard concentration should be
within the linear range. For the instrumentation used in the
validation of this method a 2 µg/mL cadmium standard gives a
net absorbance reading of about 0.350 abs. units (see
subsection (1)(e)(v) of this section) when the instrument and
the source lamp are performing to manufacturer specifications.
(iii) To increase instrument response, scale expand the
absorbance reading of the aspirated 2 µg/mL working standard
approximately four times. Increase the integration time to at
least three seconds to reduce signal noise.
(iv) Autozero the instrument while aspirating a deionized
water blank. Monitor the variation in the baseline absorbance
reading (baseline noise) for a few minutes to insure that the
instrument, source lamp and associated equipment are in good
operating condition.
(v) Aspirate the working standards and samples directly
into the flame and record their absorbance readings. Aspirate
the deionized water blank immediately after every standard or
sample to correct for and monitor any baseline drift and
noise. Record the baseline absorbance reading of each
deionized water blank. Label each standard and sample reading
and its accompanying baseline reading.
(vi) It is recommended that the entire series of working
standards be analyzed at the beginning and end of the analysis
of a set of samples to establish a concentration-response
curve, ensure that the standard readings agree with each other
and are reproducible. Also, analyze a working standard after
every five or six samples to monitor the performance of the
spectrophotometer. Standard readings should agree within ±10
to 15% of the readings obtained at the beginning of the
analysis.
(vii) Bracket the sample readings with standards during
the analysis. If the absorbance reading of a sample is above
the absorbance reading of the highest working standard, dilute
the sample with diluting solution and reanalyze. Use the
appropriate dilution factor in the calculations.
(viii) Repeat the analysis of approximately ten percent
of the samples for a check of precision.
(ix) If possible, analyze quality control samples from an
independent source as a check on analytical recovery and
precision.
(x) Record the final instrument settings at the end of
the analysis. Date and label the output.
(k) AAS-HGA analysis.
Initially analyze all of the air samples for their
cadmium content by flame atomic absorption spectroscopy (AAS)
according to the instructions given in (j) of this subsection.
If the concentration of cadmium in a sample solution is less
than three times the quantitative detection limit (0.04 µg/mL
(40 ng/mL) for the instrumentation used in the validation) and
the sample results are to be averaged with other samples for
TWA calculations, proceed with the AAS-HGA analysis of the
sample as described below.
(i) Set up the atomic absorption spectrophotometer and
HGA for flameless atomic absorption analysis of cadmium
according to the SOP (subsection (5)(i) of this section) or
the manufacturer's operational instructions and allow the
instrument to stabilize. The graphite furnace atomizer is
equipped with a pyrolytically coated graphite tube containing
a pyrolytic platform. For the source lamp, use a cadmium
hollow cathode or electrodeless discharge lamp operated at the
manufacturer's recommended setting for graphite furnace
operation. The Zeeman background corrector and EDL are
recommended for use with the L'vov platform. Instrumental
parameters for the Perkin-Elmer Model 5100 spectrophotometer
and Zeeman HGA-600 graphite furnace used in the validation of
this method are given in subsection (7) of this section.
(ii) Optimize the energy reading of the spectrophotometer
at 228.8 nm by adjusting the lamp position and the wavelength
according to the manufacturer's instructions.
(iii) Set up the autosampler to inject a 5-µL aliquot of
the working standard, sample or reagent blank solution onto
the L'vov platform along with a 10-µL overlay of the matrix
modifier.
(iv) Analyze the reagent blank (diluting solution,
(e)(vi) of this subsection) and then autozero the instrument
before starting the analysis of a set of samples. It is
recommended that the reagent blank be analyzed several times
during the analysis to assure the integrated absorbance (peak
area) reading remains at or near zero.
(v) Analyze a working standard approximately midway in
the linear portion of the working standard range two or three
times to check for reproducibility and sensitivity (see
subsection (1)(e)(v) and (vi) of this section) before starting
the analysis of samples. Calculate the experimental
characteristic mass value from the average integrated
absorbance reading and injection volume of the analyzed
working standard. Compare this value to the manufacturer's
suggested value as a check of proper instrument operation.
(vi) Analyze the reagent blank, working standard, and
sample solutions. Record and label the peak area (abs-sec)
readings and the peak and background peak profiles on the
printer/plotter.
(vii) It is recommended the entire series of working
standards be analyzed at the beginning and end of the analysis
of a set of samples. Establish a concentration-response curve
and ensure standard readings agree with each other and are
reproducible. Also, analyze a working standard after every
five or six samples to monitor the performance of the system. Standard readings should agree within ±15% of the readings
obtained at the beginning of the analysis.
(viii) Bracket the sample readings with standards during
the analysis. If the peak area reading of a sample is above
the peak area reading of the highest working standard, dilute
the sample with the diluting solution and reanalyze. Use the
appropriate dilution factor in the calculations.
(ix) Repeat the analysis of approximately ten percent of
the samples for a check of precision.
(x) If possible, analyze quality control samples from an
independent source as a check of analytical recovery and
precision.
(xi) Record the final instrument settings at the end of
the analysis. Date and label the output.
(l) Calculations.
| Note: |
Standards used for HGA analysis are in ng/mL. Total amounts of cadmium from calculations will be in ng (not µg)
unless a prior conversion is made. |
(i) Correct for baseline drift and noise in flame AAS
analysis by subtracting each baseline absorbance reading from
its corresponding working standard or sample absorbance
reading to obtain the net absorbance reading for each standard
and sample.
(ii) Use a least squares regression program to plot a
concentration-response curve of net absorbance reading (or
peak area for HGA analysis) versus concentration (µg/mL or
ng/mL) of cadmium in each working standard.
(iii) Determine the concentration (µg/mL or ng/mL) of
cadmium in each sample from the resulting
concentration-response curve. If the concentration of cadmium
in a sample solution is less than three times the quantitative
detection limit (0.04 µg/mL (40 ng/mL) for the instrumentation
used in the validation of the method) and if consecutive
samples were taken on one employee and the sample results are
to be averaged with other samples to determine a single TWA,
reanalyze the sample by AAS-HGA as described in (k) of this
subsection and report the AAS-HGA analytical results.
(iv) Calculate the total amount (µg or ng) of cadmium in
each sample from the sample solution volume (mL):
| W=(C)(sample vol, mL)(DF) |
| Where: |
W=Total cadmium in sample |
|
C=Calculated concentration of cadmium |
|
DF=Dilution Factor (if applicable) |
(v) Make a blank correction for each air sample by
subtracting the total amount of cadmium in the corresponding
blank sample from the total amount of cadmium in the sample.
(vi) Calculate the concentration of cadmium in an air
sample (mg/m3 or µg/m3) by using one of the following
equations:
| mg/m3=Wbc/(Air vol sampled, L) |
|
or |
|
| µg/m3=(Wbc)(1,000 ng/µg)/(Air vol sampled, L) |
| Where: |
Wbc=blank corrected total µg cadmium in the sample. (1µg=1,000 ng) |
(4) Backup data.
(a) Introduction.
(i) The purpose of this evaluation is to determine the
analytical method recovery, working standard range, and
qualitative and quantitative detection limits of the two
atomic absorption analytical techniques included in this
method. The evaluation consisted of the following
experiments:
(A) An analysis of twenty-four samples (six samples each
at 0.1, 0.5, 1 and 2 times the TWA-PEL) for the analytical
method recovery study of the flame AAS analytical technique.
(B) An analysis of eighteen samples (six samples each at
0.5, 1 and 2 times the action level TWA-PEL) for the
analytical method recovery study of the AAS-HGA analytical
technique.
(C) Multiple analyses of the reagent blank and a series
of standard solutions to determine the working standard range
and the qualitative and quantitative detection limits for both
atomic absorption analytical techniques.
(ii) The analytical method recovery results at all test
levels were calculated from concentration-response curves and
statistically examined for outliers at the ninety-nine percent
confidence level. Possible outliers were determined using the
Treatment of Outliers test (subsection (5)(j) of this
section). In addition, the sample results of the two
analytical techniques, at 0.5, 1.0 and 2.0 times their target
concentrations, were tested for homogeneity of variances also
at the ninety-nine percent confidence level. Homogeneity of
the coefficients of variation was determined using the
Bartlett's test (subsection (5)(k) of this section). The
overall analytical error (OAE) at the ninety-five percent
confidence level was calculated using the equation (subsection
(5)(l) of this section):
OAE=±[|Bias|+(1.96)(CV1(pooled))(100%)]
(iii) A derivation of the International Union of Pure and
Applied Chemistry (IUPAC) detection limit equation (subsection
(5)(m) of this section) was used to determine the qualitative
and quantitative detection limits for both atomic absorption
analytical techniques:
| Cld=k(sd)/m |
(Equation 1) |
|
| Where: |
Cld=the smallest reliable detectable concentration an
analytical instrument can determine at a given
confidence level. |
|
k=3 for the Qualitative Detection Limit at the
99.86% Confidence Level |
|
=10 for the Quantitative Detection Limit at the
99.99% Confidence Level. |
|
sd=standard deviation of the reagent blank (Rbl)
readings. |
|
m=analytical sensitivity or slope as calculated by
linear regression. |
(iv) Collection efficiencies of metallic fume and dust
atmospheres on 0.8-µm mixed cellulose ester membrane filters
are well documented and have been shown to be excellent
(subsection (5)(k) of this section). Since elemental cadmium
and the cadmium component of cadmium compounds are
nonvolatile, stability studies of cadmium spiked MCEF samples
were not performed.
(b) Equipment.
(i) A Perkin-Elmer (PE) Model 603 spectrophotometer
equipped with a manual gas control system, a stainless steel
nebulizer, a burner mixing chamber, a flow spoiler and a 10 cm
(one-slot) burner head was used in the experimental validation
of the flame AAS analytical technique. A PE cadmium hollow
cathode lamp, operated at the manufacturer's recommended
current setting for continuous operation (4 mA), was used as
the source lamp. Instrument parameters are listed in
subsection (6) of this section.
(ii) A PE Model 5100 spectrophotometer, Zeeman HGA-600
graphite furnace atomizer and AS-60 HGA autosampler were used
in the experimental validation of the AAS-HGA analytical
technique. The spectrophotometer was equipped with a PE
Series 7700 professional computer and Model PR-310 printer. A
PE System 2 cadmium electrodeless discharge lamp, operated at
the manufacturer's recommended current setting for modulated
operation (170 mA), was used as the source lamp. Instrument
parameters are listed in subsection (7) of this section.
(c) Reagents.
(i) J.T. Baker Chem. Co. (Analyzed grade) concentrated
nitric acid, 69.0-71.0%, and concentrated hydrochloric acid,
36.5-38.0%, were used to prepare the samples and standards.
(ii) Ammonium phosphate, monobasic, NH4H2PO4 and magnesium
nitrate hexahydrate, Mg(NO3)2.6 H2O both manufactured by the
Mallinckrodt Chem. Co., were used to prepare the matrix
modifier for AAS-HGA analysis.
(d) Standard preparation for flame AAS analysis.
(i) Dilute stock solutions: Prepared 0.01, 0.1, 1, 10
and 100 µg/mL cadmium standard stock solutions by making
appropriate serial dilutions of a commercially available 1,000
µg/mL cadmium standard stock solution (RICCA Chemical Co.,
Lot# A102) with the diluting solution (4% HNO3, 0.4% HCl).
(ii) Analyzed standards: Prepared cadmium standards in
the range of 0.001 to 2.0 µg/mL by pipetting 2 to 10 mL of the
appropriate dilute cadmium stock solution into a 100-mL
volumetric flask and diluting to volume with the diluting
solution. (See subsection (3)(g)(ii) of this section).
(e) Standard preparation for AAS-HGA analysis.
(i) Dilute stock solutions: Prepared 1, 10, 100 and
1,000 ng/mL cadmium standard stock solutions by making
appropriate serial dilutions of a commercially available 1,000
µg/mL cadmium standard stock solution (J.T. Baker Chemical
Co., Instra-analyzed, Lot# D22642) with the diluting solution
(4% HNO3, 0.4% HCl).
(ii) Analyzed standards: Prepared cadmium standards in
the range of 0.1 to 40 ng/mL by pipetting 2 to 10 mL of the
appropriate dilute cadmium stock solution into a 100-mL
volumetric flask and diluting to volume with the diluting
solution. (See subsection (3)(h)(ii) of this section).
(f) Detection limits and standard working range for flame
AAS analysis.
(i) Analyzed the reagent blank solution and the entire
series of cadmium standards in the range of 0.001 to 2.0 µg/mL
three to six times according to the instructions given in
subsection (3)(j) of this section. The diluting solution (4%
HNO3, 0.4% HCl) was used as the reagent blank. The integration
time on the PE 603 spectrophotometer was set to 3.0 seconds
and a four-fold expansion of the absorbance reading of the 2.0
µg/mL cadmium standard was made prior to analysis. The 2.0
µg/mL standard gave a net absorbance reading of 0.350 abs.
units prior to expansion in agreement with the manufacturer's
specifications (subsection (5)(f) of this section).
(ii) The net absorbance readings of the reagent blank and
the low concentration Cd standards from 0.001 to 0.1 µg/mL and
the statistical analysis of the results are shown in Table 1. The standard deviation, sd, of the six net absorbance readings
of the reagent blank is 1.05 abs. units. The slope, m, as
calculated by a linear regression plot of the net absorbance
readings (shown in Table 2) of the 0.02 to 1.0 µg/mL cadmium
standards versus their concentration is 772.7 abs.
units/(µg/mL).
(iii) If these values for sd and the slope, m, are used
in Eqn. 1 ((a)(ii) of this subsection), the qualitative and
quantitative detection limits as determined by the IUPAC
Method are:
| Cld= |
(3)(1.05 abs. units)/(772.7 abs. units/(µg/mL))= 0.0041
µg/mL for the qualitative detection limit. |
| Cld= |
(10)(1.05 abs. units)/(772.7 abs. units/µg/mL)) =0.014
µg/mL for the quantitative detection limit. |
The qualitative and quantitative detection limits for the
flame AAS analytical technique are 0.041 µg and 0.14 µg
cadmium, respectively, for a 10 mL solution volume. These
correspond, respectively, to 0.2 µg/m3 and 0.70 µg/m3 for a 200
L air volume.
(iv) The recommended Cd standard working range for flame
AAS analysis is 0.02 to 2.0 µg/mL. The net absorbance
readings of the reagent blank and the recommended working
range standards and the statistical analysis of the results
are shown in Table 2. The standard of lowest concentration in
the working range, 0.02 µg/mL, is slightly greater than the
calculated quantitative detection limit, 0.014 µg/mL. The
standard of highest concentration in the working range, 2.0
µg/mL, is at the upper end of the linear working range
suggested by the manufacturer (subsection (5)(f) of this
section). Although the standard net absorbance readings are
not strictly linear at concentrations above 0.5 µg/mL, the
deviation from linearity is only about ten percent at the
upper end of the recommended standard working range. The
deviation from linearity is probably caused by the four-fold
expansion of the signal suggested in the method. As shown in
Table 2, the precision of the standard net absorbance readings
are excellent throughout the recommended working range; the
relative standard deviations of the readings range from 0.009
to 0.064.
(g) Detection limits and standard working range for
AAS-HGA analysis.
(i) Analyzed the reagent blank solution and the entire
series of cadmium standards in the range of 0.1 to 40 ng/mL
according to the instructions given in subsection (3)(k) of
this section. The diluting solution (4% HNO3, 0.4% HCl) was
used as the reagent blank. A fresh aliquot of the reagent
blank and of each standard was used for every analysis. The
experimental characteristic mass value was 0.41 pg, calculated
from the average peak area (abs-sec) reading of the 5 ng/mL
standard which is approximately midway in the linear portion
of the working standard range. This agreed within twenty
percent with the characteristic mass value, 0.35 pg, listed by
the manufacturer of the instrument (subsection (5)(b) of this
section).
(ii) The peak area (abs-sec) readings of the reagent
blank and the low concentration Cd standards from 0.1 to 2.0
ng/mL and statistical analysis of the results are shown in
Table 3. Five of the reagent blank peak area readings were
zero and the sixth reading was 1 and was an outlier. The near
lack of a blank signal does not satisfy a strict
interpretation of the IUPAC method for determining the
detection limits. Therefore, the standard deviation of the
six peak area readings of the 0.2 ng/mL cadmium standard, 0.75
abs-sec, was used to calculate the detection limits by the
IUPAC method. The slope, m, as calculated by a linear
regression plot of the peak area (abs-sec) readings (shown in
Table 4) of the 0.2 to 10 ng/mL cadmium standards versus their
concentration is 51.5 abs-sec/(ng/mL).
(iii) If 0.75 abs-sec (sd) and 51.5 abs-sec/(ng/mL) (m)
are used in Eqn. 1 ((a)(iii) of this subsection), the
qualitative and quantitative detection limits as determined by
the IUPAC method are:
| Cld= |
(3)(0.75 abs-sec)/(51.5 abs-sec/(ng/mL)= 0.044 ng/mL for
the qualitative detection limit. |
| Cld= |
(10)(0.75 abs-sec)/(51.5 abs-sec/(ng/mL)= 0.15 ng/mL for
the quantitative detection limit. The qualitative and
quantitative detection limits for the AAS-HGA analytical
technique are 0.44 ng and 1.5 ng cadmium, respectively,
for a 10 mL solution volume. These correspond,
respectively, to 0.007 µg/m3 and 0.025 µg/m3 for a 60 L
air volume. |
(iv) The peak area (abs-sec) readings of the Cd standards
from 0.2 to 40 ng/mL and the statistical analysis of the
results are given in Table 4. The recommended standard
working range for AAS-HGA analysis is 0.2 to 20 ng/mL. The
standard of lowest concentration in the recommended working
range is slightly greater than the calculated quantitative
detection limit, 0.15 ng/mL. The deviation from linearity of
the peak area readings of the 20 ng/mL standard, the highest
concentration standard in the recommended working range, is
approximately ten percent. The deviations from linearity of
the peak area readings of the thirty and forty ng/mL standards
are significantly greater than ten percent. As shown in Table
4, the precision of the peak area readings are satisfactory
throughout the recommended working range; the relative
standard deviations of the readings range from 0.025 to 0.083.
(h) Analytical method recovery for flame AAS analysis.
(i) Four sets of spiked MCEF samples were prepared by
injecting 20 µL of 10, 50, 100 and 200 µg/mL dilute cadmium
stock solutions on 37 mm diameter filters (part No. AAWP 037
00, Millipore Corp., Bedford, MA) with a calibrated
micropipet. The dilute stock solutions were prepared by
making appropriate serial dilutions of a commercially
available 1,000 µg/mL cadmium standard stock solution (RICCA
Chemical Co., Lot # A102) with the diluting solution (4% HNO3,
0.4% HCl). Each set contained six samples and a sample blank.
The amount of cadmium in the prepared sets were equivalent to
0.1, 0.5, 1.0 and 2.0 times the TWA PEL target concentration
of 5 µg/m3 for a 400 L air volume.
(ii) The air-dried spiked filters were digested and
analyzed for their cadmium content by flame atomic absorption
spectroscopy (AAS) following the procedure described in
subsection (3) of this section. The 0.02 to 2.0 µg/mL cadmium
standards (the suggested working range) were used in the
analysis of the spiked filters.
(iii) The results of the analysis are given in Table 5. One result at 0.5 times the TWA PEL target concentration was
an outlier and was excluded from statistical analysis. Experimental justification for rejecting it is that the
outlier value was probably due to a spiking error. The
coefficients of variation for the three test levels at 0.5 to
2.0 times the TWA PEL target concentration passed the
Bartlett's test and were pooled.
(iv) The average recovery of the six spiked filter
samples at 0.1 times the TWA PEL target concentration was
118.2% with a coefficient of variation (CV1) of 0.128. The
average recovery of the spiked filter samples in the range of
0.5 to 2.0 times the TWA target concentration was 104.0% with
a pooled coefficient of variation (CV1) of 0.010. Consequently, the analytical bias found in these spiked sample
results over the tested concentration range was +4.0% and the
OAE was ±6.0%.
(i) Analytical method recovery for AAS-HGA analysis.
(i) Three sets of spiked MCEF samples were prepared by
injecting 15 µL of 5, 10 and 20 µg/mL dilute cadmium stock
solutions on 37 mm diameter filters (part no. AAWP 037 00,
Millipore Corp., Bedford, MA) with a calibrated micropipet. The dilute stock solutions were prepared by making appropriate
serial dilutions of a commercially available certified 1,000
µg/mL cadmium standard stock solution (Fisher Chemical Co.,
Lot# 913438-24) with the diluting solution (4% HNO3, 0.4% HCl).
Each set contained six samples and a sample blank. The
amount of cadmium in the prepared sets were equivalent to 0.5,
1 and 2 times the action level TWA target concentration of 2.5
µg/m3 for a 60 L air volume.
(ii) The air-dried spiked filters were digested and
analyzed for their cadmium content by flameless atomic
absorption spectroscopy using a heated graphite furnace
atomizer following the procedure described in subsection (3)
of this section. A five-fold dilution of the spiked filter
samples at 2 times the action level TWA was made prior to
their analysis. The 0.05 to 20 ng/mL cadmium standards were
used in the analysis of the spiked filters.
(iii) The results of the analysis are given in Table 6. There were no outliers. The coefficients of variation for the
three test levels at 0.5 to 2.0 times the action level TWA PEL
passed the Bartlett's test and were pooled. The average
recovery of the spiked filter samples was 94.2% with a pooled
coefficient of variation (CV1) of 0.043. Consequently, the
analytical bias was -5.8% and the OAE was ±14.2%.
(j) Conclusions.
The experiments performed in this evaluation show the two
atomic absorption analytical techniques included in this
method to be precise and accurate and have sufficient
sensitivity to measure airborne cadmium over a broad range of
exposure levels and sampling periods.
(5) References.
(a) Slavin, W. Graphite Furnace AAS -- A Source Book;
Perkin-Elmer Corp., Spectroscopy Div.: Ridgefield, CT, 1984;
p. 18 and pp. 83-90.
(b) Grosser, Z., Ed.; Techniques in Graphite Furnace
Atomic Absorption Spectrophotometry; Perkin-Elmer Corp.,
Spectroscopy Div.: Ridgefield, CT, 1985.
(c) Occupational Safety and Health Administration Salt
Lake Technical Center: Metal and Metalloid Particulate in
Workplace Atmospheres (Atomic Absorption) (USDOL/OSHA Method
No. ID-121). In OSHA Analytical Methods Manual 2nd ed. Cincinnati, OH: American Conference of Governmental
Industrial Hygienists, 1991.
(d) Occupational Safety and Health Administration Salt
Lake Technical Center: Metal and Metalloid Particulate in
Workplace Atmospheres (ICP) (USDOL/OSHA Method No. ID-125G). In OSHA Analytical Methods Manual 2nd ed. Cincinnati, OH:
American Conference of Governmental Industrial Hygienists,
1991.
(e) Windholz, M., Ed.; The Merck Index, 10th ed.; Merck &
Co.: Rahway, NJ, 1983.
(f) Analytical Methods for Atomic Absorption
Spectrophotometry, The Perkin-Elmer Corporation: Norwalk, CT,
1982.
(g) Slavin, W., D.C. Manning, G. Carnrick, and E.
Pruszkowska: Properties of the Cadmium Determination with the
Platform Furnace and Zeeman Background Correction. Spectrochim. Acta 38B:1157-1170 (1983).
(h) Occupational Safety and Health Administration Salt
Lake Technical Center: Standard Operating Procedure for
Atomic Absorption. Salt Lake City, UT: USDOL/OSHA-SLTC, In
progress.
(i) Occupational Safety and Health Administration Salt
Lake Technical Center: AAS-HGA Standard Operating Procedure. Salt Lake City, UT: USDOL/OSHA- SLTC, In progress.
(j) Mandel, J.: Accuracy and Precision, Evaluation and
Interpretation of Analytical Results, The Treatment of
Outliers. In Treatise On Analytical Chemistry, 2nd ed.,
Vol.1, edited by I. M. Kolthoff and P. J. Elving. New York:
John Wiley and Sons, 1978. pp. 282-285.
(k) 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.
(l) Occupational Safety and Health Administration
Analytical Laboratory: Precision and Accuracy Data Protocol
for Laboratory Validations. In OSHA Analytical Methods Manual
1st ed. Cincinnati, OH: American Conference of Governmental
Industrial Hygienists (Pub. No. ISBN: 0-936712-66-X), 1985.
(m) Long, G.L. and J.D. Winefordner: Limit of
Detection -- A Closer Look at the IUPAC Definition. Anal.Chem.
55:712A-724A (1983).
(n) American Conference of Governmental Industrial
Hygienists: Documentation of Threshold Limit Values and
Biological Exposure Indices. 5th ed. Cincinnati, OH:
American Conference of Governmental Industrial Hygienists,
1986.
Table 1 -- Cd Detection Limit Study
[Flame AAS Analysis]
STD (µg/mL) |
Absorbance
reading at
228.8 nm |
Statistical
analysis |
| Reagent blank |
5 |
2 |
n=6. |
|
4 |
3 |
mean=3.50. |
|
4 |
3 |
std dev=1.05. |
|
|
|
CV=0.30. |
| 0.001 |
6 |
6 |
n=6. |
|
2 |
4 |
mean=5.00. |
|
6 |
6 |
std dev=1.67. |
|
|
|
CV=0.335. |
| 0.002 |
5 |
7 |
n=6. |
|
7 |
3 |
mean=5.50. |
|
7 |
4 |
std dev=1.76. |
|
|
|
CV=0.320. |
| 0.005 |
7 |
7 |
n=6. |
|
8 |
8 |
mean=7.33. |
|
8 |
6 |
std dev=0.817. |
|
|
|
CV=0.111. |
| 0.010 |
10 |
9 |
n=6. |
|
10 |
13 |
mean=10.3. |
|
10 |
10 |
std dev=1.37. |
|
|
|
CV=0.133. |
| 0.020 |
20 |
23 |
n=6. |
|
20 |
22 |
mean=20.8. |
|
20 |
20 |
std dev=1.33. |
|
|
|
CV=0.064. |
| 0.050 |
42 |
42 |
n=6. |
|
42 |
42 |
mean=42.5. |
|
42 |
45 |
std dev=1.22. |
|
|
|
CV=0.029. |
| 0.10 |
|
84 |
n=3. |
|
|
80 |
mean=82.3. |
|
|
83 |
std dev=2.08. |
|
|
|
CV=0.025. |
Table 2 -- Cd Standard Working Range
Study
[Flame AAS Analysis]
| STD (µg/mL) |
Absorbance
reading at
228.8 nm |
Statistical
analysis |
| Reagent blank |
5 |
2 |
n=6. |
| |
4 |
3 |
mean=3.50. |
|
4 |
3 |
std dev=1.05. |
|
|
|
CV=0.30. |
| 0.020 |
20 |
23 |
n=6. |
|
20 |
22 |
mean=20.8. |
|
20 |
20 |
std dev=1.33. |
| 0.050 |
42 |
42 |
n=6. |
|
42 |
42 |
mean=42.5. |
|
42 |
45 |
std dev=1.22. |
|
|
|
CV=0.029. |
| 0.10 |
|
84 |
n=3. |
|
|
80 |
mean=82.3. |
|
|
83 |
std dev=2.08. |
|
|
|
CV=0.025. |
| 0.20 |
|
161 |
n=3. |
|
|
161 |
mean=160.0. |
|
|
158 |
std dev=1.73. |
|
|
|
CV=0.011. |
| 0.50 |
|
391 |
n=3. |
|
|
389 |
mean=391.0. |
|
|
393 |
std dev=2.00. |
|
|
|
CV=0.005. |
| 1.00 |
|
760 |
n=3. |
|
|
748 |
mean=753.3. |
|
|
752 |
std dev=6.11. |
|
|
|
CV=0.008. |
| 2.00 |
|
1416 |
n=3. |
|
|
1426 |
mean=1414.3. |
|
|
1401 |
std dev=12.6. |
|
|
|
CV=0.009. |
Table 3 -- Cd Detection Limit Study
[AAS-HGA Analysis]
| STD (ng/mL) |
Peak area
readings
x 103 at
228.8 nm |
Statistical
analysis |
| Reagent blank |
0 |
0 |
n=6. |
| |
0 |
1 |
mean=0.167. |
| |
0 |
0 |
std dev=0.41. |
| |
|
|
CV=2.45. |
| 0.1 |
8 |
6 |
n=6. |
| |
5 |
7 |
mean=7.7. |
| |
13 |
7 |
std dev=2.8. |
| |
|
|
CV=0.366. |
| 0.2 |
11 |
13 |
n=6. |
| |
11 |
12 |
mean=11.8. |
| |
12 |
12 |
std dev=0.75. |
| |
|
|
CV=0.064. |
| 0.5 |
28 |
33 |
n=6. |
| |
26 |
28 |
mean=28.8. |
| |
28 |
30 |
std dev=2.4. |
| |
|
|
CV=0.083. |
| 1.0 |
52 |
55 |
n=6. |
| |
56 |
58 |
mean=54.8. |
| |
54 |
54 |
std dev=2.0. |
| |
|
|
CV=0.037. |
| 2.0 |
101 |
112 |
n=6. |
| |
110 |
110 |
mean=108.8. |
| |
110 |
110 |
std dev=3.9. |
| |
|
|
CV=0.036. |
Table 4 -- Cd Standard Working Range Study
[AAS-HGA Analysis]
| STD (ng/mL) |
Peak area
readings
x 103 at
228.8 nm |
Statistical
analysis |
| 0.2 |
11 |
13 |
n=6. |
|
11 |
12 |
mean=11.8. |
|
12 |
12 |
std dev=0.75. |
|
|
|
CV=0.064. |
| 0.5 |
28 |
33 |
n=6. |
|
26 |
28 |
mean=28.8. |
|
28 |
30 |
std dev=2.4. |
|
|
|
CV=0.083. |
| 1.0 |
52 |
55 |
n=6. |
|
56 |
58 |
mean=54.8. |
|
54 |
54 |
std dev=2.0. |
|
|
|
CV=0.037. |
| 2.0 |
101 |
112 |
n=6. |
|
110 |
110 |
mean=108.8. |
|
110 |
110 |
std dev=3.9. |
|
|
|
CV=0.036. |
| 5.0 |
247 |
265 |
n=6. |
|
268 |
275 |
mean=265.5. |
|
259 |
279 |
std dev=11.5. |
|
|
|
CV=0.044. |
| 10.0 |
495 |
520 |
n=6. |
|
523 |
513 |
mean=516.7. |
|
516 |
533 |
std dev=12.7. |
|
|
|
CV=0.025. |
| 20.0 |
950 |
953 |
n=6. |
|
951 |
958 |
mean=941.8. |
|
949 |
890 |
std dev=25.6. |
|
|
|
CV=0.027. |
| 30.0 |
1269 |
1291 |
n=6. |
|
1303 |
1307 |
mean=1293. |
|
1295 |
1290 |
std dev=13.3. |
|
|
|
CV=0.010. |
| 40.0 |
1505 |
1567 |
n=6. |
|
1535 |
1567 |
mean=1552. |
|
1566 |
1572 |
std dev=26.6. |
|
|
|
CV=0.017. |
Table 5 -- Analytical Method Recovery
[Flame AAS Analysis]
| Test
level |
0.5x |
1.0x |
|
|
2.0x
|
|
µg
taken |
µg
found |
Percent
rec. |
µg
taken |
µg
found |
Percent
rec. |
µg
taken |
µg
found |
Percent
rec. |
| |
|
|
|
|
|
|
|
|
| 1.00 |
1.0715 |
107.2 |
2.00 |
2.0688 |
103.4 |
4.00 |
4.1504 |
103.8 |
| 1.00 |
1.0842 |
108.4 |
2.00 |
2.0174 |
100.9 |
4.00 |
4.1108 |
102.8 |
| 1.00 |
1.0842 |
108.4 |
2.00 |
2.0431 |
102.2 |
4.00 |
4.0581 |
101.5 |
| 1.00 |
*1.0081 |
*100.8 |
2.00 |
2.0431 |
102.2 |
4.00 |
4.0844 |
102.1 |
| 1.00 |
1.0715 |
107.2 |
2.00 |
2.0174 |
100.9 |
4.00 |
4.1504 |
103.8 |
| 1.00 |
1.0842 |
108.4 |
2.00 |
2.0045 |
100.2 |
4.00 |
4.1899 |
104.7 |
| |
n= |
5 |
6 |
6 |
|
| mean= |
107.9 |
101.6 |
103.1 |
| std dev= |
0.657 |
1.174 |
1.199 |
| CV1= |
0.006 |
0.011 |
0.012 |
| CV1 |
|
|
|
| (pooled)= |
0.010 |
|
|
*Rejected as an outlier -- this value did not pass the
outlier T-test at the 99% confidence level.
| Test level 0.1x |
taken |
µg
found |
µg
rec.
|
Percent |
| 0.200 |
0.2509 |
125.5 |
|
| 0.200 |
0.2509 |
125.5 |
|
| 0.200 |
0.2761 |
138.1 |
|
| 0.200 |
0.2258 |
112.9 |
|
| 0.200 |
0.2258 |
112.9 |
|
| 0.200 |
0.1881 |
94.1
|
|
|
n= |
6 |
|
|
mean= |
118.2 |
|
|
std dev= |
15.1 |
|
|
CV1= |
0.128 |
|
Table 6 -- Analytical Method Recovery
[AAS-HGA analysis]
| Test
level |
0.5x |
1.0x |
|
2.0x |
|
| ng
taken |
ng
found |
Percent
rec. |
ng
taken |
ng
found |
Percent
rec. |
ng
taken |
ng
found |
Percent
rec. |
| |
|
|
|
|
|
|
|
|
| 75 |
71.23 |
95.0 |
150 |
138.00 |
92.0 |
300 |
258.43 |
86.1 |
| 75 |
71.47 |
95.3 |
150 |
138.29 |
92.2 |
300 |
258.46 |
86.2 |
| 75 |
70.02 |
93.4 |
150 |
136.30 |
90.9 |
300 |
280.55 |
93.5 |
| 75 |
77.34 |
103.1 |
150 |
146.62 |
97.7 |
300 |
288.34 |
96.1 |
| 75 |
78.32 |
104.4 |
150 |
145.17 |
96.8 |
300 |
261.74 |
87.2 |
| 75 |
71.96 |
95.9 |
150 |
144.88 |
96.6 |
300 |
277.22 |
92.4 |
| |
n= |
6 |
6 |
6 |
|
|
| |
mean= |
97.9 |
94.4 |
90.3 |
|
|
| |
std dev= |
4.66 |
2.98 |
4.30 |
|
|
| |
CV1= |
0.048 |
0.032 |
0.048 |
|
|
| |
CV1 |
|
|
|
|
|
| |
(pooled)= |
0.043 |
|
|
|
|
(6) Instrumental Parameters for Flame AAS Analysis
Atomic Absorption Spectrophotometer
(Perkin-Elmer Model 603)
Flame: Air/Acetylene—lean, blue
Oxidant Flow: 55
Fuel Flow: 32
Wavelength: 228.8 nm
Slit: 4 (0.7 nm)
Range: UV
Signal: Concentration (4 exp)
Integration Time: 3 sec
(7) Instrumental Parameters for HGA Analysis
Atomic Absorption Spectrophotometer
(Perkin-Elmer Model 5100)
Signal Type: Zeeman AA
Slitwidth: 0.7 nm
Wavelength: 228.8 nm
Measurement: Peak Area
Integration Time: 6.0 sec
BOC Time: 5 sec BOC=Background Offset
Correction. Zeeman Graphite Furnace
(Perkin-Elmer Model HGA-600)
Step
|
Ramp
time
(sec)
|
Hold
time
(sec)
|
Temp.
(°C)
|
Argon
flow
(mL/
min)
|
Read
(sec)
|
| 1) Predry |
5 |
10 |
90 |
300 |
|
| 2) Dry |
30 |
10 |
140 |
300 |
|
| 3) Char |
10 |
20 |
900 |
300 |
|
| 4) Cool Down |
1 |
8 |
30 |
300 |
|
| 5) Atomize |
0 |
5 |
1600 |
0 |
-1 |
| 6) Burnout |
1 |
8 |
2500 |
300 |
|
[Statutory Authority: Chapter 49.17 RCW. 93-21-075 (Order
93-06), § 296-62-07449, filed 10/20/93, effective 12/1/93;
93-07-044 (Order 93-01), § 296-62-07449, filed 3/13/93,
effective 4/27/93.]
NOTES:
Reviser's note: The brackets and enclosed material in the text of the
above section occurred in the copy filed by the agency.