Page:NIOSH Manual of Analytical Methods - 3704.pdf/2

 PERCHLOROETHYLENE (portable GC) in exhaled breath and air: METHOD 3704, Issue 1, dated 15 January 1998 - Page 2 of 5

EQUIPMENT

REAGENTS:

1. Sampler: air bags, Tedlar™, 1-L, or other 1. Perchloroethylene*in air, commercial mixed gas appropriate size. standards, or liquid perchloroethylene. 2. Drying tube for exhaled breath sampling. 2. Air, ultra-pure, or Nitrogen, purified. Plastic tubing, ca. 1-cm ID, containing 3. Dry-Rite™ desiccant, indicating or equivalent. approximately 5 g indicating Dry-Rite, held in place with glasswool plugs. 3. Personal sampling pump, 0.02 to 5 L/min, or other rate suitable for filling sample bag, with flexible connecting tubing. 4. Tubing, PTFE, ca. 6 ft. length. 5. Portable gas chromatograph (GC), with photoionization detector, preferably with gas sampling loop, column (p. 3704-1), and (if appropriate) strip chart recorder. 6. Syringes, gas tight, various sizes appropriate to the GC. NOTE: To reduce the possibility of contamination, use separate, previously unused syringes for working standards and samples. Test syringes for contamination occasionally by filling them with clean air and analyzing the contents.
 * See SPECIAL PRECAUTIONS

SPECIAL PRECAUTIONS: Perchloroethylene is a suspect carcinogen as well as an irritant to the eyes, nose, and skin. Wear appropriate protective clothing. Shipment of compressed gases must comply with 49 CFR 171-177 regulations regarding shipment of hazardous materials.

SAMPLING AND MEASUREMENT: 1. Start GC instrument and allow to warm up according to manufacturer's instructions. Select sampling mode. NOTE: A straight baseline should be attained at the highest sensitivity likely to be used. 2. Spot Sample. Draw air sample into the gas sampling loop of the GC with the on-board sampling pump, if supplied. Alternatively, inject an aliquot of air to be sampled into the GC with a gas-tight syringe. NOTE: A large contributor to random error in the method is imprecision of replicate injections. To improve precision: (1) use a gas sampling loop for injections, if available; (2) make at least three replicate determinations per sample; (3) use an injection volume large enough to be precisely readable, and consistent with that used in calibration. 3. Integrated Air Sample. a. Evacuate a clean sample bag using the inlet port of a personal sampling pump. NOTE: To reduce memory effects and contamination, use only previously unused sample bags. Alternatively, purge used bags at least twice with clean air, then fill with clean air and analyze for perchloroethylene (step 6). b. Attach sample bag to outlet port of a personal sampling pump with a minimum length of flexible tubing. To the inlet port of the pump, attach a length of PTFE tubing sufficient to reach the desired site. When sample size is small, a rubber squeeze bulb may be used in place of a personal sampling pump. In either case, flush tubing and pump/bulbwith sample air prior to, and clean air subsequent to, sample collection. NOTE: Tygon™ tubing has been shown to adsorb some materials in complex hydrocarbon mixtures and to off gas during latersample collection causing an increase in hydrocarbon NIOSH Manual of Analytical Methods (NMAM), Fourth Edition