An estimation of the sublimation rate of o-phthalodinitrile and acrylamide during filter sampling.

pan Association for Working Environment Measurement. The vapor pressures of these substances have been determined to be 2.5 •~ 10 mmHg for o-phthalodinitrile at 26•Ž, and 5 •~ 10-3 mmHg for acrylamide at 25•Ž, using the vapor saturation method.3) Due to sublimation on the filter, however, filter sampling of these substances may yield a lower value than their actual environmental concentration. The present work was designed to estimate the amount of a sample lost by sublimation during the sampling process. A specific amount of test sample dissolved in methanol was applied as a sample to main filter through which prefiltered dust-free air was then drawn for 1 to 12 min. All the methanol vehicle was evaporated within the first few minutes. Air flow was controlled to within the range from 29.5 to 30.5 //min. Filters used were of either Teflon impregnated glass fiber type T60A20 or glass fiber type GA100, both with a diameter of 47 mm. A back-up filter was used in order to recover any of the sample escaping through the filter as particles. When T60A20 was used, two filter sheets were used together, to apply 100 ƒÊl of methanol solution. Immediately after the air stream was stopped, the residual test substance on the main and back-up filters were extracted together with 5 ml of methanol. The conectnartion of the sample in the extract was determined by HPLC. The air flow experiment was carried out in an air-conditioned room at 22 to 23•Ž, and