Page:NIOSH Manual of Analytical Methods - 7056.pdf/2

 BARIUM, soluble compounds: METHOD 7056, Issue 2, dated 15 August 1994 - Page 2 of 3 REAGENTS:

EQUIPMENT:

1. 2. 3. 4. 5.

Water, distilled or deionized. Nitric acid (HNO 3), conc.* Hydrochloric acid (HCl), conc.* Sodium chloride (NaCl). 5% HCl (v/v)/1.1 mg/mL Na +: Dilute 5 mL conc. HCl and 0.28 g NaCl to 100 mL with deionized water. 6. Calibration stock solution, 1000 µg Ba/mL. Commercially available or dissolve 1.437 g BaCO 3 in minimum volume of (1+1) HCl and dilute to 1 L with 1% (v/v) HCl. 7. Nitrous oxide, 98%. 8. Acetylene, 99.6%.



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 4 L/min, with flexible connecting tubing. 3. Atomic absorption spectrophotometer with nitrous oxide-acetylene burner head and barium hollow cathode lamp. NOTE: Background correction (e.g., D 2 or H 2 lamp) needed for samples with >0.1% (w/v) Ca 2+. 4. Regulators, two-stage, for nitrous oxide and acetylene. 5. Beakers, Phillips, 125-mL, or Griffin, 50-mL, with watchglass covers.* 6. Volumetric flasks, 10- and 100-mL.* 7. Pipets, 4- to 400-µL, and 5-mL. 8. Hotplate, surface temperature 140 °C. 9. Forceps or tweezers, plastic-tipped. 10. Centrifuge, and centrifuge tubes, 50-mL.

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

SPECIAL PRECAUTIONS: Nitric and hydrochloric acids are corrosive liquids. Wear protective clothing and work in a fume head. 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 a sample size of 50 to 2000 L. Do not exceed a filter loading of ca. 2 mg total dust.

SAMPLE PREPARATION: 3. 4. 5. 6. 7. 8. 9. 10.

Open cassette filter holders and transfer samples and blanks to clean beakers. Add 10 mL boiling distilled water. Let stand 10 min with occasional swirling. Decant extract to a centrifuge tube. Wash filter and beaker twice with ca. 2 mL hot distilled water and add to centrifuge tube. Repeat extraction and washing (steps 4 and 5), adding the solutions to the centrifuge tube. Remove filter with forceps and rinse with stream of hot distilled water into centrifuge tube. Rinse original beaker three times with ca. 2 mL hot distilled water and add to centrifuge tube. Centrifuge and decant the solution to a second beaker. Add three drops conc. HCl to sample and evaporate until ca. 0.5 mL liquid remains. Cool each beaker. Pipet 5.0 mL 5% HCl/1.1 mg/mL Na + solution into each beaker. Swirl to dissolve residue.

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