Page:NIOSH Manual of Analytical Methods - 7030.pdf/2

 ZINC and compounds, as Zn: METHOD 7030, Issue 2, dated 15 August 1994 - Page 2 of 3 REAGENTS:

EQUIPMENT:

1. Nitric acid, conc. 2. Nitric acid, 1% (v/v). Add 10 mL conc. HNO3 to 500 mL water; dilute to 1 L. 3. Calibration stock solution, 1000 µg/mL Zn. Commercial standard or dissolve 1.00 g Zn metal in minimum volume of (1+1) HCl; dilute to 1 L with 1% (v/v) HNO3. 4. Air, filtered. 5. Acetylene. 6. Distilled or deionized water.



See SPECIAL PRECAUTIONS.

1. Sampler: cellulose ester membrane filter, 0.8-µm pore size, 37-mm diameter; in cassette filter holder. 2. Personal sampling pump, 1 to 3 L/min, with flexible connecting tubing. 3. Atomic absorption spectrophotometer with air-acetylene burner head and zinc hollow cathode lamp or electrodeless discharge lamp. 4. Regulators, 2-stage, for air and acetylene. 5. Beakers, Phillips, 125-mL, or Griffin, 50-mL, With watchglass covers.* 6. Volumetric flasks, 100-mL.* 7. Micropipets, 1 to 100 µL.* 8. Hotplate, surface temperature 140 °C.

Clean with conc. HNO3 and rinse thoroughly with distilled or deionized water before use.

SPECIAL PRECAUTIONS: Perform all acid digestions in a fume hood.

SAMPLING: 1. 2.

Calibrate each personal sampling pump with a representative sampler in line. Sample at an accurately known flow rate between 1 and 3 L/min for a sample size of 2 to 400 L. Do not exceed a filter loading of ca. 2 mg total dust.

SAMPLE PREPARATION: NOTE: The following sample preparation gave quantitative recovery (see EVALUATION OF METHOD). 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. 3. Open the cassette filter holders and transfer the samples and blanks to clean beakers. 4. Add 6 mL conc. HNO3 and cover with a watchglass. Start reagent blanks at this point. 5. Heat on hotplate (140 °C) until sample dissolves and a slightly yellow solution is produced. Add additional acid as needed to completely destroy organic material. 6. When the sample solution is clear, remove watchglass and rinse into the beaker with 1% HNO3. 7. Place the beakers on the hotplate and allow to go to near dryness (ca. 0.5 mL liquid remaining). 8. Rinse walls of beaker with 10 mL 10% HNO3. Reheat 5 min to dissolve the residue, then allow to air cool. 9. Transfer the solution quantitatively to a 100-mL volumetric flask and dilute to volume with distilled or deionized water. NOTE: Dilute to a smaller volume, e.g., 10 mL, if required for sensitivity of analysis for other metals in the sample.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94