GAS-CHROMATOGRAPHY OF 4,4'-DIPHENYLMETHANE DIISOCYANATE IN THE WORKPLACE ATMOSPHERE

A sensitive gas chromatographic procedure for the determination of 4,4 '-diphenylmethane diisocyanate concentration in air is described. Trap s containing 20-40-mesh silica gel coated with phosphoric acid are use d. After the aspiration of the air, the silica gel is eluted with sodi um hydroxide in methanol. The amine formed is then separated with a ga s chromatograph and measured with a nitrogen-phosphorus detector. This can be performed in 7 min. Virtually no breakthrough occurs if an air concentration of up to 128 nmol in 20 1 is sampled. The detection lim it based on a 20-1 air sample is 0.7 mu g/m(3). Complete analysis requ ires about 30 min. The method was used to determine the concentration of 4,4'-diphenylmethane diisocyanate in working environments during sp raying operations.