Page:NIOSH Manual of Analytical Methods - 3702.pdf/2

 ETHYLENE OXIDE: METHOD 3702, Issue 2, dated 15 August 1994 - Page 2 of 4 REAGENTS: 1. 2. 3.

EQUIPMENT:

Uncontaminated air for preparation of standards and purging samplers. Carrier gas, air, ultra-pure.* Ethylene oxide (EtO) for standards, pure or in known concentration (i.e., 88/12 Freon 12/EtO mixture).* NOTE: Commercial sterilant mixtures are sold on a weight/weight ratio. An 88/12 mixture is 27% EtO by volume.



See SPECIAL PRECAUTIONS.

1. Portable gas chromatograph (GC) with photoionization detector, column (page 3702-1), and (if appropriate) portable strip chart recorder or integrator, and battery chargers, regulators, and other peripherals necessary for individual instruments. 2. Personal sampling pump, 0.02 to 4 L/min or other rate suitable for filling bag, with flexible connecting tubing. 3. Syringes, gas-tight (0.01 to 1-mL, 1-L), for standards preparation, sample collection and sample injection. 4. Bags, inert plastic (e.g., aluminized polyester or Tedlar), 2- to 20-L, for standard preparation, and (if needed) sample collection. NOTE: Care must be taken to assure that the pump, bag, and tubing are all inert and impermeable to the analyte (step 3).

SPECIAL PRECAUTIONS: Ethylene oxide is flammable. Shipment of compressed calibration gas and carrier gas must comply with 49 CFR regulations on shipment of hazardous materials. SAMPLING: 1.

Collect samples by one of the following methods: NOTE: Other techniques such as liquid displacement or use of an evacuated vessel may be adaptable to this method but have not been evaluated. a. Draw air directly into a syringe. Collect syringe samples by first purging a gas-tight syringe several times with clean air to remove any residual ethylene oxide from previous samples, then draw air into the syringe at the time and location of interest. NOTE: This technique requires less equipment and also has the advantage of allowing for a grab sample. It is not easily applied to TWA measurements. Since this is a one-time analysis, the concentration of the sample must be estimated in advance so that the proper size sample can be collected. An injection volume as small as ten microliters can be used if the concentration is expected to be several hundred ppm, while a 1.0- mL syringe is more appropriate if a concentration on the order of 0.01 ppm is expected. b. Bag samples for TWA. (1) Evacuate the sampling bag. (2) Allow the pump to be purged with sample air before opening the valve on the sampling bag. Collect bag sample by using pump to pull air from a point of interest and push it into the bag. NOTE: This technique can obtain a sample in a relatively short time (e.g., at 4 L/min, a few seconds sampling time will yield the fraction of a liter necessary for several replicate analyses). By selecting a low flow rate and larger bag (i.e., 10 mL/min flow and 5 L bag), an 8-h TWA sample can be obtained. A few mL will allow for replicate injections of 1 mL or less, although in practice several hundred mL to 1 L is a more reasonable minimum. The maximum volume is limited only by the size of bags available and space in which to store them.

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