Page:NIOSH Manual of Analytical Methods - 5022.pdf/2

 ARSENIC, organo-: METHOD 5022, Issue 2, dated 15 August 1994 - Page 2 of 6 REAGENTS: 1. 2. 3.

4. 5. 6.

7.

8.

9.

EQUIPMENT:

Deionized water. Hydrochloric acid, conc. Eluent A (2.4 m M HCO -3/1.9 mM CO 32-/1.0 mM B4O 72-). Dissolve 0.8067 g NaHCO 3, 0.8055 g Na 2CO 3, and 1.5257 g Na 2B4O 7 10H 2O in 4 L deionized water. Eluent B (5 m M B4O 72-). Dissolve 7.6284 g Na 2B4O 7 10H 2O in 4 L deionized water. Potassium persulfate solution,* K 2S2O 8, saturated in 15% (v/v) HCl. Sodium borohydride, 1% NaBH 4 (w/v) in 0.2% KOH (w/v). Add 5 g NaBH 4 and 1 g KOH to deionized water; dilute to 500 mL. Prepare fresh weekly. Stock standards, 1000 µg As/mL: a. Methylarsonic acid.* Dissolve 0.9341 g CH 3AsO 3H2 (Ansul Co., Weslaco, TX), in deionized water; dilute to 500 mL. b. Dimethylarsenic acid.* Dissolve 0.9210 g (CH 3)2AsO 2H (Ansul Co.) in deionized water; dilute to 500 mL. c. p-Aminophenylarsonic acid.* Dissolve 1.4485 g p-H2NC 6H4AsO 3H2 in 5 mL 1 N NaOH. Dilute to 500 mL with deionized water. Protect from light. d. Arsenic trioxide.* Dissolve 0.6602 g As 2O 3 in 5 mL 1 N NaOH. Dilute to 500 mL with deionized water. e. Arsenic pentoxide.* Dissolve 0.7669 g As 2O 5 in 5 mL 1 N NaOH. Dilute to 500 mL with deionized water. Calibration stock solution, 1 µg/mL mixed analyte. Dilute 0.1 mL of each stock standard (REAGENTS, 7.) with Eluent A in a 100-mL volumetric flask. Prepare fresh daily. Argon.



See SPECIAL PRECAUTIONS

1. Sampler: PTFE polyethylene-backed membrane filter, 1-µm pore size (MilliporeType FA or equivalent), 37-mm diameter with backup pad; in cassette filter holder. 2. Personal sampling pump, 1 to 3 L/min, with flexible connecting tubing. 3. Ion chromatograph with suppressor and detector bypassed. Route column effluent via Microbore PTFE tubing (0.3-mm ID x 0.6-mm OD, Dionex) directly into arsine generator (Figure 1). 4. Syringes, plastic, 10-mL, with male luer fittings. 5. Arsine generator: proportioning pump with flow-rated pump tubes and 1.5-mm ID x 3-mm OD manifold mixing coils, 5-turn and 20-turn (Technicon or equivalent), 1.5-mm ID x 3.5-mm OD glass "T" connectors; gas-liquid separator and expansion chamber (Figure 2); 1 m of 1/4" OD PTFE tubing; three PTFE 1/4" ID Swagelok fittings; and rotometer (100 to 900 mL/min). 6. Atomic absorption spectrophotometer (reciprocal linear UV dispersion 0.65 nm/mm); As electrodeless discharge lamp and power supply; and atomization cell (16-cm x 13-mm ID windowless quartz tube with 18-cm x 4-mm ID inlet tube fused in the center), wound with Nichrome wire (14 Ω/m, spaced 2 to 3 mm between turns and wrapped with heat resistant tape) (Figure 3). Temperature in the cell is measured by a thermocouple (800 °C). Mount the cell on top of a single-slot AAS burner head and align with burner alignment controls. 7. Beakers, 50-mL.* 8. Ultrasonic waterbath. 9. Volumetric flasks, 10-, 100- and 500-mL. 10. Pipets, 25-µL and 0.1- to 1-mL.

Soak all glassware in mild detergent, rinse with deionized water, 10% HNO 3, and deionized water.

SPECIAL PRECAUTIONS: Potassium persulfate is a powerful oxidizing agent. Arsine gas is extremely toxic and can be fatal. The arsenic compounds used in the stock standards are poisonous [3].

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