California Code of Regulations › Title 8 - Industrial Relations › Division 1 - Department of Industrial Relations › Chapter 4 - Division of Industrial Safety › Subchapter 7 - General Industry Safety Orders › Group 16 - Control of Hazardous Substances › Article 110 - Regulated Carcinogens › Appendix E - Cadmium in Workplace Atmospheres

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
Method Number: ID-189
Matrix: Air
OSHA 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 AAS-HGA
						  Analysis
Validation Level: 2.5 to 10
						  µg/m3 for a 60 L air vol 1.25 to 5.0
						  µg/m3 for a 400 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
1.1. 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.
1.2. 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 (5.1., 5.2.).
1.3. History
Previously, two OSHA sampling and analytical methods
						  for cadmium were used concurrently (5.3., 5.4.). 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 (5.3.) or inductively coupled plasma/atomic
						  emission spectroscopy (ICP-AES) (5.4.). 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 (5.3.) 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.
1.4. Properties (5.5.)
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 5.5.
1.5. Method Performance
A synopsis of method performance is presented below.
						  Further information can be found in Section
						  4.
1.5.1. 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.
1.5.2. 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.
1.5.3. 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%.
1.5.4. 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%.
1.5.5. 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 (5.6.); the 2 µg/mL cadmium standard gave an absorbance
						  reading of 0.350 abs. units.
1.5.6. 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 (5.7.). Data suggests that under Stabilized Temperature
						  Platform Furnace (STPF) conditions (see Section
						  1.6.2.), characteristic mass values
						  are transferable between properly functioning instruments to an accuracy of
						  about 20% (5.2.). 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.
1.6. Interferences
1.6.1. High concentrations of silicate interfere in
						  determining cadmium by flame AAS (5.6.). However, silicates are not
						  significantly soluble in the acid matrix used to prepare the samples.
1.6.2. 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 (5.2.):
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.
1.7. Toxicology (5.14.)
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 OSHA 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 (non-carcinogenic)
						  and the lungs (carcinogenic).
2. Sampling
2.1. Apparatus
2.1.1. 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.
2.1.2. 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.
2.2. Procedure
2.2.1. 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.
2.2.2. 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.
2.2.3. Replace the end plugs into the filter cassettes
						  immediately after sampling. Record the sampling conditions.
2.2.4. Securely wrap each sample filter cassette
						  end-to-end with an OSHA Form 21 sample seal.
2.2.5. 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.
2.2.6. Ship the samples to the laboratory for analysis
						  as soon as possible in a suitable container designed to prevent damage in
						  transit.
3. Analysis
3.1. Safety Precautions
3.1.1. Wear safety glasses, protective clothing and
						  gloves at all times.
3.1.2. Handle acid solutions with care. Handle all
						  cadmium samples and solutions with extra care (see Sect. 1.7.). 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.
3.1.3. 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.
3.1.4. 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.
3.1.5. Never pipet by mouth.
3.1.6. Refer to the instrument instruction manuals and
						  SOPs (5.8., 5.9.) for proper and safe operation of the atomic absorption
						  spectrophotometer, graphite furnace atomizer and associated equipment.
3.1.7. 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.
3.2. Apparatus for Sample and Standard
						  Preparation
3.2.1. Hot plate, capable of reaching 150° C,
						  installed in an exhaust hood.
3.2.2. Phillips beakers, 125 mL.
3.2.3. Bottles, narrow-mouth, polyethylene or glass
						  with leakproof caps: used for storage of standards and matrix modifier.
3.2.4. Volumetric flasks, volumetric pipets, beakers
						  and other associated general laboratory glassware.
3.2.5. Forceps and other associated general laboratory
						  equipment.
3.3. Apparatus for Flame AAS Analysis
3.3.1. 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.
3.3.2. Oxidant: compressed air, filtered to remove
						  water, oil and other foreign substances.
3.3.3. 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.
3.3.4. 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.
3.3.5. Exhaust vent installed directly above the
						  spectrophotometer burner head.
3.4. Apparatus for AAS-HGA Analysis
3.4.1. 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.
3.4.2. Pyrolytically-coated graphite tubes containing
						  solid, pyrolytic L'vov platforms.
3.4.3. Polyethylene sample cups, 2.0 to 2.5 mL, for use
						  with the autosampler.
3.4.4. Inert purge gas for graphite furnace atomizer:
						  compressed gas cylinder of purified argon.
3.4.5. Two gauge, two-stage pressure regulator for the
						  argon gas cylinder.
3.4.6. Cooling water supply for graphite furnace
						  atomizer.
3.4.7. Exhaust vent installed directly above the
						  graphite furnace atomizer.
3.5. Reagents
All reagents should be ACS analytical reagent grade or
						  better.
3.5.1. Deionized water with a specific conductance of
						  less than 10 µS.
3.5.2. Concentrated nitric acid,
						  HNO3.
3.5.3. Concentrated hydrochloric acid, HCl.
3.5.4. Ammonium phosphate, monobasic,
						  NH4H2PO4.
3.5.5. Magnesium nitrate,
						  Mg(NO3)2.
3.5.6. 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.
3.5.7. 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.
3.5.8. Matrix modifier for AAS-HGA analysis: Dissolve
						  1.0 g
						  NH4H2PO4
						  and 0.15 g Mg(NO3)2 in
						  approximately 200 mL deionized water. Add 1 mL HNO3 and
						  dilute to 500 mL with deionized water.
3.5.9 Nitric Acid, 1:1 HNO3/DI
						  H2O mixture: Carefully add a measured volume of
						  concentrated HNO3 to an equal volume of DI
						  H2O.
3.5.10. Nitric acid, 10% v/v: Carefully add 100 mL of
						  concentrated HNO3 to 500 mL of DI
						  H2O and dilute to 1 L.
3.6. Glassware Preparation
3.6.1. 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.
3.6.2. Rinse volumetric flasks and all other glassware
						  with 10% nitric acid and deionized water prior to use.
3.7. Standard Preparation for Flame AAS Analysis
3.7.1. 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 Section
						  3.5.6.
3.7.2. 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.
3.8. Standard Preparation for AAS-HGA Analysis
3.8.1. 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 Section
						  3.5.6.
3.8.2. 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
									 (µg/mL)
Std Solution
									 (µg/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
2
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.
3.9. Sample Preparation
3.9.1. 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.
3.9.2. 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.
3.9.3. After completing the HNO3
						  digestion and cooling the samples, add 40 L (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.
3.9.4. 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.
3.10. 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.
3.10.1. Set up the atomic absorption spectrophotometer
						  for the air/acetylene flame analysis of cadmium according to the SOP (5.8.) 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 10 to 20 min 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 Appendix A.
3.10.2. 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 Section
						  1.5.5.) when the instrument and the
						  source lamp are performing to manufacturer specifications.
3.10.3. 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 3 seconds
						  to reduce signal noise.
3.10.4. 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.
3.10.5. 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.
3.10.6. 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.
3.10.7. 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.
3.10.8. Repeat the analysis of approximately 10% of the
						  samples for a check of precision.
3.10.9. If possible, analyze quality control samples
						  from an independent source as a check on analytical recovery and
						  precision.
3.10.10. Record the final instrument settings at the
						  end of the analysis. Date and label the output.
3.11. 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 Section
						  3.10. 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.
3.11.1. Set up the atomic absorption spectrophotometer
						  and HGA for flameless atomic absorption analysis of cadmium according to the
						  SOP (5.9.) 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 Appendix B.
3.11.2. 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.
3.11.3. 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.
3.11.4. Analyze the reagent blank (diluting solution,
						  Section 3.5.6.) 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.
3.11.5. 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 Sections
						  1.5.5. and 1.5.6.) 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.
3.11.6. 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.
3.11.7. 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.
3.11.8. 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.
3.11.9. Repeat the analysis of approximately 10% of the
						  samples for a check of precision.
3.11.10. If possible, analyze quality control samples
						  from an independent source as a check of analytical recovery and
						  precision.
3.11.11. Record the final instrument settings at the
						  end of the analysis. Date and label the output.
3.12. 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.
3.12.1. 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.
3.12.2. 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.
3.12.3. 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 Section
						  3.11. and report the AAS-HGA
						  analytical results.
3.12.4. 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)
3.12.5. 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.
3.12.6. 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
4.1. Introduction
4.1.1. 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:
1. An analysis of 24 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.
2. An analysis of 18 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.
3. 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.
4.1.2. The analytical method recovery results at all
						  test levels were calculated from concentration-response curves and
						  statistically examined for outliers at the 99% confidence level. Possible
						  outliers were determined using the Treatment of Outliers test (5.10.). 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 99% confidence level. Homogeneity of the coefficients of variation
						  was determined using the Bartlett's test (5.11.). The overall analytical error
						  (OAE) at the 95% confidence level was calculated using the equation
						  (5.12.):
OAE = ±[|Bias| +
						  (1.96)(CV1 (pooled)) (100%)]
4.1.3. A derivation of the International Union of Pure
						  and Applied Chemistry (IUPAC) detection limit equation (5.13.) 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
k = 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.
4.1.4. 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 (5.11.). Since elemental
						  cadmium and the cadmium component of cadmium compounds are nonvolatile,
						  stability studies of cadmium spiked MCEF samples were not performed.
4.2. Equipment
4.2.1. 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 Appendix A.
4.2.2. 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 Appendix B.
4.3. Reagents
4.3.1. 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.
4.3.2. Ammonium phosphate, monobasic,
						  NH4H2PO4
						  and magnesium nitrate, Mg(NO3)2,
						  both manufactured by the Mallinckrodt Chem. Co., were used to prepare the
						  matrix modifier for AAS-HGA analysis.
4.4. Standard Preparation for Flame AAS Analysis
4.4.1. 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).
4.4.2. 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 Section
						  3.7.2.)
4.5. Standard Preparation for AAS-HGA Analysis
4.5.1. 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).
4.5.2. 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 Section
						  3.8.2.)
4.6. Detection Limits and Standard Working Range for
						  Flame AAS Analysis
4.6.1. 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 Section
						  3.10. 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 (5.6.).
4.6.2. 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 I. 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 II) of the 0.02 to 1.0µg/mL cadmium
						  standards versus their concentration is 772.7 abs. units/(µg/mL).
4.6.3. If these values for sd and the slope, m, are
						  used in Eqn. 1 (Sect. 4.1.3.), 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.
4.6.4. 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 II. 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
						  (5.6.). Although the standard net absorbance readings are not strictly linear
						  at concentrations above 0.5 µg/mL, the deviation from linearity is only
						  about 10% 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 II, 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.
4.7. Detection Limits and Standard Working Range for
						  AAS-HGA Analysis
4.7.1. 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 Section
						  3.11. 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 20% with the characteristic mass value, 0.35 pg, listed by the
						  manufacturer of the instrument (5.2.).
4.7.2. 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 III. 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 IV) of the 0.2 to 10
						  ng/mL cadmium standards versus their concentration is 51.5
						  abs-sec/(ng/mL).
4.7.3. If 0.75 abs-sec (sd) and 51.5 abs-sec/(ng/mL)
						  (m) are used in Eqn. 1 (Sect. 4.1.3.), 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.
4.7.4. 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 IV. 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 10%. The deviations from linearity of the peak
						  area readings of the 30 and 40 ng/mL standards are significantly greater than
						  10%. As shown in Table IV, 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.
4.8. Analytical Method Recovery for Flame AAS
						  Analysis
4.8.1. Four sets of spiked MCEF samples were prepared
						  by injecting 20 L 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.
4.8.2. The air-dried spiked filters were digested and
						  analyzed for their cadmium content by flame atomic absorption spectroscopy
						  (AAS) following the procedure described in Section
						  3. The 0.02 to 2.0 µg/mL
						  cadmium standards (the suggested working range) were used in the analysis of
						  the spiked filters.
4.8.3. The results of the analysis are given in Table
						  V. 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.
4.8.4. 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%.
4.9. Analytical Method Recovery for AAS-HGA
						  Analysis
4.9.1. 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.
4.9.2. 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
						  Section 3. 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.
4.9.3. The results of the analysis are given in Table
						  VI. 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%.
4.10. 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:
5.1. Slavin, W.
Graphite Furnace AAS - A Source
						  Book
; Perkin-Elmer Corp., Spectroscopy Div.: Ridgefield, CT , 1984; p.
						  18 and pp. 83-90.
5.2. Grosser, Z., Ed.;
Techniques in Graphite
						  Furnace Atomic Absorption Spectrophotometry
; Perkin-Elmer Corp.,
						  Spectroscopy Div.: Ridgefield, CT, 1985.
5.3. 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.
5.4. 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.
5.5. Windholz, M., Ed.;
The Merck
						  Index
, 10th ed.; Merck & Co.: Rahway, NJ, 1983.
5.6.
Analytical Methods for Atomic Absorption
						  Spectrophotometry
, The Perkin-Elmer Corporation: Norwalk, CT,
						  1982.
5.7. 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).
5.8. Occupational Safety and Health Administration Salt
						  Lake Technical Center:
Standard Operating Procedure for Atomic
						  Absorption
. Salt Lake City, UT: USDOL/OSHA-SLTC, In progress.
5.9. Occupational Safety and Health Administration Salt
						  Lake Technical Center:
AAS-HGA Standard Operating Procedure
.
						  Salt Lake City, UT: USDOL/OSHA-SLTC, In progress.
5.10. 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.
5.11. 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.
5.12. 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.
5.13. Long, G.L. and J.D. Winefordner: Limit of
						  Detection --A Closer Look at the IUPAC Definition.
Anal.Chem.
						  55
:712A-724A (1983).
5.14. 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 I
Cd Detection Limit Study (Flame AAS
						  Analysis)
STD
									 (
µ
g/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 II
Cd Standard Working Range Study (Flame AAS
						  Analysis)
STD
Absorbance Reading
									 (
µ
g/mL)
Statistical at 228.8 nm
									 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
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
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 III
Cd Detection Limit Study (AAS-HGA
						  Analysis)
STD
Peak Area Readings
									 (ng/mL)
Statistical x
									 10
3 at 228.8 nm 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 IV
Cd Standard Working Range Study (AAS-HGA
						  Analysis)
STD
Peak Area Readings
									 (ng/mL)
Statistical x
									 10
3 at 228.8 nm 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 V
Analytical Method Recovery (Flame AA
						  Analysis)
Test
								  Level
0.5x
1.0x
2.0x
µ
g
								  Taken
µ
g
								  Found
% Rec.
µ
g
								  Taken
µ
g Found
%
								  Rec.
µ
g Taken
µ
g
								  Found
% 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
µ
g
								  Taken
µ
g
								  Found
% Rec.
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 VI
Analytical Method Recovery (Flame AA
						  Analysis)
Test Level
0.5x
1.0x
2.0x
ng
								  Taken
ng Found
%
								  Rec.
ng Taken
ng
								  Found
% Rec.
ng
								  Taken
ng Found
%
								  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