Page:NIOSH Manual of Analytical Methods - 7901.pdf/2

 ARSENIC TRIOXIDE, as As: METHOD 7901, Issue 2, dated 15 August 1994 - Page 2 of 4 EQUIPMENT:

REAGENTS: 1. 2. 3. 4. 5.

6.

7. 8.

Nitric acid, conc. Nitric acid, 1% (v/v). Dilute 10 mL conc. HNO 3 to 1 L with distilled or deionized water. Hydrogen peroxide, 30% (w/w). Ni2+ in 1% HNO 3, 1000 µg/mL. Dilute 4.95 g Ni(NO 3)2 to 1 L with 1% HNO 3. Calibration stock solution*, 1000 µg As/mL, commercially available, or dissolve 1.320 g primary standard As 2O 3 in 25 mL 20% (w/v) KOH. Neutralize with 20% (v/v) HNO 3 to a phenolphthalein endpoint. Dilute to 1 L with 1% HNO 3. 1 M Na 2CO 3:glycerol solution, 20:1. Dissolve 9.5 g sodium carbonate in 100 mL distilled or deionized water. Add 5 mL pure glycerol. Distilled or deionized water. Argon.

1.



3.

See Special Precautions

2.

4. 5. 6. 7. 8. 9.

Sampler: Cellulose ester membrane filter, 0.8-µm pore size, 37-mm diameter, and cellulose backup pad in cassette filter holder treated as follows: a. Remove inlet plug from the loaded cassette. b. Add 250 µL 20:1 Na 2CO 3:glycerol solution with a micropipet directly onto filter (wet entire surface). c. Attach to vacuum source and draw 30 to 60 L clean air through the filter. d. Let dry overnight or dry 8 h @ 120 °C. Replace the inlet plug. e. Use within one week. Personal sampling pump, 1 to 3 L/min, with flexible connecting tubing. NOTE: The treated filter has a high pressure drop; a personal sampling pump with flow rate control is required. Atomic absorption spectrophotometer with graphite furnace atomizer, arsenic electrodeless discharge lamp, and background correction. Regulator, two-stage for argon. Beakers, Phillips, 125-mL, or Griffin, 50-mL with watchglass covers.* Volumetric flasks, 10-mL.* Assorted volumetric pipets as needed.* Hotplate, surface temperature to 150 °C. Steambath.

Clean all glassware with conc. nitric acid and rinse thoroughly with distilled or deionized water before use.

SPECIAL PRECAUTIONS: Arsenic is a carcinogen [6]. Handle appropriately. Perform all 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 30 to 1000 L. Do not exceed a filter loading of ca. 2 mg total dust.

SAMPLE PREPARATION: 3. 4. 5.

Transfer both the treated filter and backup pad to a clean beaker. Add 15 mL conc. HNO 3 and cover with a watchglass. NOTE: Start reagent blanks at this step. Heat on a 150 °C hotplate until the liquid volume is reduced to about 1 mL.

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