Page:NIOSH Manual of Analytical Methods - 1002.pdf/2

 β-CHLOROPRENE: METHOD 1002, Issue 2, dated 15 August 1994 - Page 2 of 4 REAGENTS: 1. 2.

3. 4. 5.

6. 7. 8.

EQUIPMENT:

Carbon disulfide, chromatographic quality.* Chloroprene*, freshly distilled from xylene solution at reduced pressure; BP = 31 °C at 354 mm Hg (47 kPa). n-Pentane, reagent grade. n-Hexane, reagent grade. Calibration stock solution, 47.9 mg/mL. Deliver 0.500 mL (0.479 g at 20 °C) freshly distilled chloroprene from a delivery pipet under the surface of pentane in a partially filled 10-mL volumetric flask. Dilute to the mark with pentane. Stable one day at -15 °C. Nitrogen, purified. Hydrogen, prepurified. Air, filtered.



See SPECIAL PRECAUTIONS.

1. Sampler: glass tube, 7 cm long, 6-mm OD, 4mm ID, flame-sealed ends, containing two sections of activated (600 °C) coconut shell charcoal (front = 100 mg; back = 50 mg) separated by a 2-mm urethane foam plug. A silylated glass wool plug precedes the front section and a 3-mm urethane foam plug follows the back section. Pressure drop across the tube at 1 L/min airflow must be less than 3.4 kPa. Tubes are commercially available. 2. Personal sampling pump, 0.01 to 0.1 L/min, with flexible connecting tubing. 3. Gas chromatograph, FID, integrator and column (page 1002-1). 4. Micro-distillation apparatus for vacuum distillation of chloroprene. 5. Vials, 2-mL, glass with PTFE-lined septa and crimp seals. 6. Syringe, 10-µL, readable to 0.1 µL. 7. Volumetric flasks, 10-mL. 8. Pipets, 1-mL, graduated in 0.1 mL, with pipet bulb.

SPECIAL PRECAUTIONS: Carbon disulfide is toxic and flammable. Work with it only in a hood. Chloroprene incompatibilities by contact with oxidizers (e.g., peroxides) may cause polymerization with evolution of heat and rupture of containers. Chloroprene attacks some plastics, rubber, and coatings. It will autoxidize very rapidly, even at 0 °C, producing an unstable peroxide (mixed 1,2- and 1,4-addition copolymer with oxygen) which catalyzes exothermic polymerization. Therefore, immediately after distilling, store at -15 °C.

SAMPLING: 1. 2. 3. 4.

Calibrate each personal sampling pump with a representative sampler in line. Break the ends of the sampler immediately before sampling. Attach sampler to personal sampling pump with flexible tubing. Sample at an accurately known flow rate between 0.01 and 0.1 L/min for a total sample size of 1.5 to 8 L. Cap the samplers with plastic (not rubber) caps and pack securely for shipment.

SAMPLE PREPARATION: 5. 6. 7.

Place the front and back sorbent sections of the sampler tube in separate vials. Discard the glass wool and foam plugs. Add 1.0 mL CS 2 to each vial. Attach crimp cap to each vial. Allow to stand 30 min with occasional agitation. Decant the liquid into a clean vial. NOTE 1: Desorbed samples are unstable in the presence of charcoal, losing significant amounts over several hours.

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