The development and evaluation of a hydrobromic acid-coated sampling tube for measuring occupational exposures to ethylene oxide

A new sampling method is described for the measurement of ethylene oxide (Rt0) exposures in the workplace. This sampling method uses a hydrobromic acid-treated charcoal tube to collect Et0 as its 2-bromethanol reaction product. Because 2-bromoethanol is less volatile and less reactive than Et0, improved sampling capacity and sample stability are observed with this method over the collection of Et0 on untreated charcoal. Sample analysis is performed by gas chromatography with electron capture detection (GC/ECD) following desorption with dimethylformamide and derivatization of the 2-bromoethanol reaction product with heptafluorobutyrylimidazole (HFBI) The direct analysis of 2-bromoethanol by GC/ECD was not reproducible, and this effect was attributed to the presence of excess hydrobromic acid (HBr) in the sample. This matrix effect was eliminated by the formation of the heptafluorobutyrate ester, a water-insoluble derivation of 2-bromoethanol, which was extracted into iso-octane for analysis. This analytical scheme is very sensitive and has been used to monitor Et0 at the 0.1 ppm level in the laboratory. An average recovery of 96% was obtained for short-term samples (15 minutes) collected from a 5 ppm test atmosphere at 23° and 80% relative humidity. Similar high recoveries were obtained for 4-hour samples collected at a sampling rate of 0.1 to 16 ppm Et0 at high humidity (80%) and ambient temperature (22-25°C). Samples collected under these same conditions and sorted for a minimum of two weeks resulted in average recoveries that ranged from 84% to 10%. Average recoveries of 97% were obtained for 2 ppm air samples collected at low humidity with not storage; however, storage of these samples at 22-25°C resulted in an approximate loss of 5% per week. A field comparison study of samples obtained from a hospital sterilization facility using the test method and the Qazi-Ketchum sample method resulted in a correlation for paired samples of 0.99 over a concentration range of 0.3 to 7.0 ppm Et0. The resulting data indicated that this sampling and analytical method is a convenient accurate, and reliable means of monitoring Et0 exposure in the workplace.