Page:NIOSH Manual of Analytical Methods - 7013.pdf/2

 ALUMINUM and compounds, as Al: METHOD 7013, Issue 2, dated 15 August 1994 - Page 2 of 3 REAGENTS:

EQUIPMENT:

1. Nitric acid, conc. 2. Nitric acid, 10% (v/v). Add 100 mL conc. HNO 3 to 500 mL water; dilute to 1 L. 3. Calibration stock solution, 1000 µg Al/mL. Commercially available or dissolve 1.000 g Al wire in minimum volume of (1+1) HCl using small drop of Hg as catalyst. Dilute to 1 L with 1% (v/v) HCl. 4. Cs solution, 50 mg/mL. Dissolve 73.40 g CsNO 3 in 100 mL water; dilute to 1 L. 5. Nitrous oxide. 6. Acetylene. 7. Distilled or deionized water.

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 a nitrous oxide-acetylene burner head and aluminum hollow cathode lamp. 4. Regulators, two-stage, for N 2O and acetylene. 5. Beakers, Phillips, 125-mL, or Griffin, 50-mL, with watchglass covers.* 6. Volumetric flasks, 10- and 100-mL.* 7. Micropipets, 5 to 500 µL.* 8. Hotplate, surface temperature 100 to 140 °C.

Clean with conc. nitric acid 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 total sample size of 10 to 400 L. Do not exceed 2 mg total dust loading on the filter.

SAMPLE PREPARATION: NOTE: Alumina (Al 2O 3) will not be dissolved by this procedure. Lithium borate fusion is necessary to dissolve alumina. The following sample preparation gave quantitative recovery for soluble aluminum compounds (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 cassettes and transfer the samples and blanks to separate clean beakers. 4. Add 6 mL conc. HNO 3 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 acid as needed to completely destroy organic material. 6. When the sample solution is clear, remove watchglass and rinse into the beaker with 10% HNO 3. 7. Place the beakers on a hotplate and allow to go to a small liquid volume (ca. 0.5 mL). 8. When sample is dry, rinse walls of beaker with 3 to 5 mL 10% HNO 3. Reheat for 5 min to dissolve the residue, then allow to air cool. 9. Transfer the solution quantitatively to a 10-mL volumetric flask containing 0.2 mL 50 mg/mL Cs solution. Dilute to volume with 10% HNO 3. NOTE: If vanadium or sulfuric acid are present, add 1% (w/w) La as a releasing agent [1,3].

CALIBRATION AND QUALITY CONTROL: 10.

Add known amounts, covering the range 0 to 500 mg Al per sample, of calibration stock solution to 100-mL volumetric flasks containing 2.0 mL 50 mg/mL Cs solution and dilute to volume with NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94