Page:NIOSH Manual of Analytical Methods - 7020.pdf/2

 CALCIUM and compounds, as Ca: METHOD 7020, Issue 2, dated 15 August 1994 - Page 2 of 4 REAGENTS:

EQUIPMENT:

1. Nitric acid, conc. 2. Hydrochloric acid, conc. 3. Hydrochloric acid, 5% (v/v). Add 50 mL conc. HCl to 500 mL water; dilute to 1 L. 4. Calibration stock solution, 1000 µg Ca/mL. Commercially available or add 50 mL deionized water and minimum volume of HCl (20 mL) to dissolve 2.498 g CaCO 3. Dilute to 1 L with deionized water. 5. Cs solution, 50 mg/mL. Dissolve 73.40 g CsNO 3 in water to make 1 L solution. 6. La solution, 50 mg/mL. Dissolve 156 g La(NO 3)3·6H 2O in water to make 1 L solution. 7. Distilled or deionized water. 8. Air, filtered. 9. Acetylene. 10. Perchloric acid, 60% w/v.

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 an air-acetylene burner head and calcium hollow cathode lamp. 4. Regulators, 2-stage, for air and acetylene. 5. Beakers, Phillips, 125-mL, or Griffin, 50-mL, with watchglass covers.* 6. Volumetric flasks, 25- and 100-mL.* 7. Micropipets, 5 to 500 µL.* 8. Hotplate, surface temperature 140 and 400 °C.



See SPECIAL PRECAUTIONS.

Clean with conc. HNO 3 and rinse thoroughly with distilled or deionized water before use.

SPECIAL PRECAUTIONS: Perform all perchloric acid digestions in a perchloric acid 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 total sample size of 20 to 400 L. Do not exceed 2 mg total dust loading on the filter.

SAMPLE PREPARATION:

3. 4. 5. 6. 7. 8. 9. 10. 11.

12.

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. Open the cassette filter holders and transfer the samples and blanks to separate clean beakers. Add 5 mL conc. HNO 3 and cover with a watchglass. Start reagent blanks at this point. Heat on hotplate (140 °C) until most of the acid has evaporated. Add 2 mL conc. HNO 3 and 1 mL 60% HClO 4. Heat on 400 °C hotplate until dense fumes of perchloric acid appear. Remove watchglass and rinse into the beaker with distilled water. Place the beakers on the 400 °C hotplate and allow to go to dryness. Cool each beaker and dissolve the residues in 5 mL 5% HCl. Transfer the solution quantitatively to a 100-mL volumetric flask containing 2 mL of 50 mg/mL Cs solution and 2 mL of 50 mg/mL La solution. NOTE: Dilute to a smaller volume (e.g., 10 mL) with proportionally less Cs and La if required for sensitivity of analysis for other metals in the sample. Dilute to volume with 5% HCl.

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