Page:NIOSH Manual of Analytical Methods - 7082.pdf/2

 LEAD by Flame AAS: Method 7082, Issue 2, dated 15 August 1994 - Page 2 of 7 REAGENTS: EQUIPMENT: 1. Nitric acid, conc.* 1. Sampler: Cellulose ester filter, 0.8- m 2. Nitric acid, 10% (v/v). Add 100 mL conc. pore size, 37-mm diameter, in cassette HNO3 to 500 mL water; dilute to 1 L. filter holder. 3. Hydrogen peroxide, 30% H2O2 (w/w), 2. Personal sampling pump, 1 to 4 L/min, with reagent grade.* flexible connecting tubing. 4. Calibration stock solution, 1000 µg/mL Pb. 3. Atomic Absorption Spectrophotometer with Commercial standard or dissolve 1.00 g Pb an air-acetylene burner head and metal in minimum volume of (1+1) HCl and background correction. dilute to 1 L with 1% (v/v) HCl. Store in a 4. Lead hollow cathode lamp or electrode polyethylene bottle. Stable one year. dischargeless lamp. 5. Air, compressed, filtered. 5. Regulators, two-stage, for air and 6. Acetylene acetylene. 7. Distilled or deionized water. 6. Beakers, Phillips, 125-mL, or Griffin, 50-mL with watchglass covers.** 7. Volumetric flasks, 10- and 100-mL.** 8. Assorted volumetric pipets as needed.** See SPECIAL PRECAUTIONS. 9. Hotplate, surface temperature 140 C. 10. Bottles, polyethylene, 100-mL.

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. 2.

Calibrate each personal sampling pump with a representative sampler in line. Sample at an accurately known flow rate between 1 and 4 L/min for up to 8 h for a total sample size of 200 to 1500 L for TWA measurements. Do not exceed a filter loading of ca. 2 mg total dust.

SAMPLE PREPARATION: NOTE 1:

The following sample preparation gave quantitative recovery (see EVALUATION OF METHOD) [4]. Steps 4 through 9 of Method 7300 or other quantitative ashing techniques may be substituted, especially if several metals are to be determined on a single filter. NOTE 2: The Appendix gives a microwave digestion procedure which may be necessary for complete recovery of lead from some matrices, especially epoxy-based paint. 3. Open the cassette filter holders and transfer the samples and blanks to clean beakers. 4. Add 3 mL conc. HNO3, and 1 mL 30% H2O2 and cover with a watchglass. Start reagent blanks at this step. NOTE: If PbO2 is not present in the sample, the 30% H 2O2 need not be added [2,4]. 5. Heat on 140 C hotplate until volume is reduced to about 0.5 mL. 6. Repeat two more times using 2 mL conc. HNO 3 and 1 mL 30% H2O2 each time. 7. Heat on 140 C hotplate until ca. 0.5 mL liquid remains. 8. When sample is dry, rinse the watchglass and walls of the beaker with 3 to 5 mL 10% HNO 3. Allow the solution to evaporate to dryness. 9. Cool each beaker and dissolve the residues in 1 mL conc. HNO 3. 10. Transfer the solution quantitatively to a 10-mL volumetric flask and dilute to volume with distilled water.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition