Trace analysis of airborne 1,6-hexamethylenediisocyanate and the related aminoisocyanate and diamine by glass capillary gas chromatography.

A capillary gas chromatographic method was developed for the analysis of complex air mixtures of 1,6-hexamethylenediisocyanate, 1,6-hexamethyleneaminoisocyanate and 1,6-hexamethylenediamine. The method is based on derivatization in the sampling step of the reactive isocyanate groups to corresponding urethane groups by the alkaline ethanolic solvent and a subsequent derivatization of remaining amino groups to amide groups with heptafluorobutyric acid anhydride. The overall procedure, including sampling, gave a linear response at air concentrations of 3-300 micrograms/m3 for 1,6-hexamethylenediisocyanate with a precision of ca. 4% at 15 micrograms/m3 and a detection limit of ca. 0.2 microgram/m3 using nitrogen selective detection. In a field measurement of air concentrations in welding work on lacquered metal parts at a motor-car workshop, concentrations of 1,6-hexamethylenediisocyanate above 600 micrograms/m3 were found. Also 1,6-hexamethyleneaminoisocyanate and 1,6-hexamethylenediamine were found at concentrations of the order of 15% of the 1,6-hexamethylenediisocyanate concentration.