| Abstract: | Studies of the performance of a technique for the assessment of occupational exposure to methanol vapor were completed. This air sampling technique utilized carbon molecular sieve contained in a stainless steel tube for the collection of methanol vapor from controlled test atmospheres. The test atmospheres were generated by means of a dynamic, all-glass system which utilized a syringe drive to introduce methanol into an air stream of known temperature and humidity. The sampling period for all samples was 120 minutes. The test atmosphere was drawn through the tube by means of a battery-powered air sampling pump which could be fitted with various flow-limiting orifices. In preliminary studies at test conditions of 95% RH at 35° C, and 400 ppm methanol, a sampling flow rate of 20 mL/min (established by means of limiting orifices) was the maximum flow which did not produce more than 5% breakthrough; this sampling flow rate was used in all subsequent parts of the research. The collection tubes were desorbed with 250° C nitrogen in a programmed thermal desorber, and the amount of desorbed methanol vapor was determined through gas chromatography-flame ionization detection. The analytical instrumentation was calibrated by direct injection of methanol into the inlet of the programmed thermal desorber. Next studies were conducted to assess the performance of the technique under conditions of varying temperature, humidity, and methanol concentration. These investigations demonstrated that the methanol concentration, partial pressure of water vapor, and the interaction of temperature with partial pressure of water vapor had a significant effect upon the recovery, while breakthrough was significantly affected by the partial pressure of water vapor and the interaction of temperature with the partial pressure of water vapor. In general, the data suggest that the sampling flow rate should be increased to 50-100 mL/min if the anticipated methanol concentration is less than 50 ppm and that breakthrough occurred only under conditions of high heat and humidity when the methanol concentration was 800 ppm... |
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