Recently, anxieties about toxicity of residual ethylene oxide (EO) in medical devices have been increasing. In response to this, FDA submitted a proposal to regulate EO residual limit in 1978.Investigations on the various conditions for gas liquid chromatographical determination of EO in plastics or fibers were performed along with the regulation.As a result, we recommend to use the following method.25% flexol 8N8 coated on chromosorb WAW is used for column packing for the sake of better resolution. Residual EO is to be extracted by ethanol at 50° to 70℃ for 3 hours, using propylene oxide for internal standard, and 100-1000μl of the gasous phase is to be injected to the column. In this head space method, detection limit of EO was 0.05μg/ml.The amount of residual EO varied according to the sampling site.An obvious difference between polyvinyl chloride tube and silicone tube in absorption and dissipation was obtained.In case of polyvinyl chloride tube, it took more than 7 days to decrease residual EO to 25 ppm, whereas it was only one day in silicone tube.

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Adsorption and dissipation of ethylene oxide (EO) in surgical latex rubber glove, natural and synthetic rubber sheets were investigated.Dissipation of EO adsorbed in the surgical latex rubber glove with 0.24mm thickness was unexpectedly fast, and in one hour, its residual amount of EO was reduced to 100ppm at room temperature (25℃). However, in case of the glove with the same material as the above, but with 1.3mm thickness, it took more than 24 hours for its EO residual to be decreased to 100ppm.Experiments on EO dissipation of various kinds of rubber sheets, 4 latex rubbers and 14 synthetic rubbers, were conducted. Amongst all the sheets, the fastest dissipation of EO was observed from silicone, latex, isoprene and butadiene rubbers. The next was from ethylene-propylene-butadiene rubber. On the other hand, butyl and acrylo-nitrile-butadiene rubbers showed the slowest dissipation. The result proved that the dissipation of EO was closely related to oxgen permiability of rubber.The most effective factor to remove EO residua from the devices was heating. With regard to those devices with complicated structure such as blood circulating system, ventilation was also effective in combination with heating. Aerator should be used under the temperature between 50° and 60℃, and 3-8 cycle ventilation per minute.By using the aerator, dissipation was shortened by 1/4-1/10,compared with standing condition under room temperature.

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Methods by gas chromatographic determination for ethylene oxide (EO), ethylene chlorohydrin (ECH) and ethylene glycol (EG) in aquous solution were investigated, and the convertions from EO to ECH and EG in various conditions were examined.The results are as follows;EO was not easily converted to ECH or EG in aquous state at 40℃ for 5 hours, resulting in only a few percent of EO convertion to ECH or EG.When saline solution was circulated into blood tubing of an artificial kindey adsorbed 150 μg/g of EO, which was made by polyvinyl chloride resin, maximum concentration of extracted EO (40μg/ml) in saline solution was obtained after 6 hours. The ratio of extracted amount of EO against the total amount of in the tubing was about 60% in this case.In case that the amount of residual EO was relatively small such as 40 μg/g, extracted EO was 3.4μg/ml and extraction ratio was remarkably reduced to 20%.When horse serum was circulated into the tubing in the same manner as the above, the investigation result suggests that a part of extracted EO is combined with protein in the serum.

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