Lead by GFAAS (7105)
LEAD by GFAAS
Pb
MW:
7105
207.19 (Pb); CAS: 7439-92-1 (Pb); RTECS: 223.19 (PbO) 1317-36-8 (PbO)
METHOD: 7105, Issue 2
OF7525000 (Pb) OG1750000 (PbO)
EVALUATION: PARTIAL
OSHA : 0.05 mg/m3 NIOSH: <0.1 mg/m3; blood Pb 60 µg/100 g ACGIH: 0.05 mg/m3
PROPERTIES:
Issue 1: 15 August 1990 Issue 2: 15 August 1994 soft metal; d 11.3 g/cm3; MP 327.5 C valences +2, +4 in salts
SYNONYMS: elemental lead and lead compounds except alkyl lead
SAMPLING SAMPLER:
FILTER (0.8-µm cellulose ester membrane)
FLOW RATE:
1 to 4 L/min
VOL-MIN: -MAX:
1 L @ 0.05 mg/m3 1500 L
SHIPMENT:
MEASUREMENT TECHNIQUE:
ATOMIC ABSORPTION SPECTROPHOTOMETER, GRAPHITE FURNACE
ANALYTE:
lead
ASHING:
conc. HNO3, 3 mL; 30% H2O2; 1 mL; 140 C
routine FINAL SOLUTION: 10 mL 5% HNO3
SAMPLE STABILITY:
stable
WAVELENGTH:
283.3 nm
FIELD BLANKS:
2 to 10 field blanks per set
GRAPHITE TUBE:
pyrolytic coated
INJETION:
20 µL + 10 µL matrix modifier, DRY: 110 C, 70 sec; CHAR: 800 C, 30 sec; ATOMIZE: 1800 C, 5 sec.
ACCURACY
RANGE STUDIED:
not studied
BIAS:
not determined
OVERALL PRECISION ( ACCURACY:
rT):
not determined not determined
BACKGROUND CORRECTION: D2, H2, or Zeeman CALIBRATION:
Pb2+ in 5% HNO3
RANGE
0.05 to 100 µg per sample [1]
ESTIMATED LOD:
0.02 µg per sample [1]
PRECISION ( r):
0.049 [1]
APPLICABILITY: The working range is 0.002 to >1 mg/m3 for a 200-L air sample. If high concentrations are expected, the samples should be analyzed by flame AAS. The method is applicable to elemental lead, including Pb fume, and all other aerosols containing lead. This is an elemental analysis, not compound specific. Aliquots of the sample may be analyzed separately for additional elements.
INTERFERENCES: Use D2 or H2 continuum or Zeeman background correction to control molecular absorption. High concentrations of calcium, sulfate, carbonate, sulfate, carbonate, phosphate, iodide, fluoride, or acetate can be offset by an additional sample treatment step.
OTHER METHODS: This revises and replaces P&CAM 214 (2). Method 7300 (ICP-AES) is an alternate analytical method. Method 7505 is specific for lead sulfide by X-ray diffraction. Method 7082 is a flame AAS method, with a higher working range.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition LEAD by GFAAS: METHOD 7105, Issue 2, dated 15 August 1994 - Page 2 of 4 EQUIPMENT: REAGENTS: 1. Sampler: Cellulose ester membrane filter, 1. Nitric acid, conc.* 0.8-µm, 37-mm, in 2-piece cassette. 2. Nitric acid, 5% (v/v). Add 50 mL conc. HNO3 2. Personal sampling pump, 1 to 4 L/min, with to 500 mL water; dilute to 1 L. flexible connecting tubing. 3. Hydrogen peroxide, 30% H2O (w/w), reagent 3. Atomic absorption spectrophotometer with grade.* graphite furnace atomizer and background 4. Calibration stock solution, 1000 µg/mL Pb. correction. Commercial standard or dissolve 1.00 g Pb 4. Lead hollow cathode lamp or electrode metal in minimum volume of HNO3 and dilute dischargeless lamp. to 1 L with 1% (v/v) HNO3. Store in a 5. Regulators, two-stage, for Argon. polyethylene bottle. 6. Beakers, Phillips, 125-mL, or Griffin, 50-mL 5. Matrix Modifier. Place 0.2 g NH4H2PO4 and with watchglass covers.** 0.3 g Mg(NO3)2 in a 100-mL volumetric flask. 7. Volumetric flasks, 10- and 100-mL.** Add 2 mL conc. HNO3 and bring to volume 8. Assorted volumetric pipets as needed.** with distilled or deionized water. 9. Hotplate, surface temperature 140 C. 6. Argon, prepurified. 7. Distilled or deionized water. 10. Bottles, polyethylene, 100-mL.
- See SPECIAL PRECAUTIONS.
- Clean all glassware with conc. nitric acid and
rinse thoroughly with distilled or deionized water before use.
SPECIAL PRECAUTIONS: Concentrated nitric acid is an irritant and may burn skin. Perform all acid digestions in a fume hood. Hydrogen peroxide is a strong oxidizing agent, a strong irritant, and corrosive to the skin. Wear gloves and eye protection.
SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. 2. Sample at an accurately known flow rate between 1 and 4 L/min for up to 8 h for a total sample size of 1 to 1500 L for TWA measurements. Do not exceed a filter loading of ca. 2 mg total dust. SAMPLE PREPARATION:
3. 4. 5. 6. 7. 8.
NOTE: Some matrices, especially bulk samples containing epoxy-based paint, may require a different digestion procedure for complete recovery of lead. See the Appendix of Method 7082 (Lead by Flame AAS) for a microwave digestion procedure which can be used for this purpose. Open the cassette filter holders and transfer the samples and blanks to clean beakers. Add 3 mL conc. HNO3, and 1 mL 30% H2O2 and cover with a watchglass. Start reagent blanks at this step. Heat on 140 C hotplate until volume is reduced to about 0.5 mL. Rinse the watchglass and walls of the beaker with 3 to 5 mL 5% HNO 3. Allow the solution to evaporate to 0.5 mL. Cool each beaker. Transfer the solution quantitatively to a 10-mL volumetric flask and dilute to volume with distilled water.
CALIBRATION AND QUALITY CONTROL: 9. Prepare a series of six working standards covering the range 0.002 to 0.1 µg/mL Pb (0.02 to 1.0 µg Pb per sample). a. Add aliquots of calibration stock solution to 100-mL volumetric flasks. Dilute to volume with 5% HNO3. Store the working standards in polyethylene bottles and prepare fresh weekly. b. Analyze the working standards together with the blanks and samples (steps 12 through 14). c. Prepare a calibration graph of absorbance vs. solution concentration (µg/mL). 10. Analyze a standard for every 10 samples to check for instrument drift. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition LEAD by GFAAS: METHOD 7105, Issue 2, dated 15 August 1994 - Page 3 of 4 11. Check recoveries with at least one spiked media blank per 10 samples. NOTE: Perform a matrix spike of a sample occasionally to check for matrix interferences. If an adequate recovery is not obtained (85 to 115%), an alternate method of analysis should be used, such as flame AAS or ICP. MEASUREMENT: 12. Set spectrophotometer as specified by the manufacturer and to conditions on page 7105-1. NOTE: An alternate wavelength is 217.0 nm [3]. Analyses at 217.0 nm have slightly greater sensitivity, but poorer signal-to-noise ratio compared to 283.3 nm. Also, non-atomic absorption is significantly greater at 217.0 nm, making the use of D 2 or H2 continuum, or Zeeman background correction mandatory at that wavelength. 13. Add matrix modifier to samples and standards in proper ratio of 2 to 1 (sample or standard to matrix modifier). 14. Analyze standards, samples, and blanks. Record absorbance readings. NOTE: If the absorbance value for the sample is above the linear range of the standards, dilute with 5% HNO3, reanalyze, and apply the appropriate dilution factor in the calculations. CALCULATIONS: 15. Using the measured absorbances, calculate the corresponding concentrations (µg/mL) of lead in the sample, Cs, and average media blank, Cb, from the calibration graph. 16. Using the solution volumes (mL) of the sample, V s, and media blanks, Vb, calculate the concentration, C (mg/m3), of lead in the air volume sampled, V (L):
C
CsVs
CbVb V
, mg/m 3.
EVALUATION OF METHOD: Method P&CAM 214 [2], issued on 1/29/76, was based on a method for metal pollutants in water [4]. Air sampling and digestion procedures followthose in Method 7082. The analytical procedure was evaluated by DataChem Laboratories in 1990 [1]. The LOD was determined at 0.02 µg per sample, with a LOQ of 0.05 µg per sample. The precision of the measurement procedure was 0.049. The overall precision, bias, and accuracy of the method were not determined. The reagents for digesting various lead species are given below: Species
Digestion Method
Pb metal Pb metal Pb PbS PbO2 PbO2 Pb in paint* Pb in paint*
HNO3 only HNO3 + H2O2 HNO3 only HNO3 only HNO3 only HNO3 + H2O2 HNO3 only HNO3 + H2O2
- Standard Reference Material #1579, U.S. National
Institute of Standards and Technology.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition LEAD by GFAAS: METHOD 7105, Issue 2, dated 15 August 1994 - Page 4 of 4
REFERENCES: [1] [2] [3] [4]
Backup Data Report for Method 7105 submitted to NIOSH by DataChem Laboratories, NIOSH (Unpublished, September, 1990). NIOSH Manual of Analytical Methods, 2nd. ed., V. 1, P&CAM 214, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-157-A (1977). Analytical Methods for Atomic Absorption Spectrophotometry, Perkin-Elmer Corporation (1976). Fernandez, F.J. and D.C. Manning. Atomic Absorbtion Analyses of Metal Pollutants in Water Using a Heated Graphite Atomizer,Atomic Absorption Newsletter 10, 65 (1971).
METHOD REVISED BY: James B. Perkins, Brent E. Stephens, and Michael P. Beesley, DataChem Laboratories, Salt Lake City, UT.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition