Capillary gas chromatographic method for the determination of complex mixture of isocyanates and amines

Abstract

A capillary gas chromatographic method using nitrogen-selective detection was developed for the analysis of complex mixtures of isocyanates and amines in air. The isocyanate group was converted directly in the air sampling step into urethane by reaction with ethanol using potassium hydroxide as a catalyst. The amine group was converted into an amide using pentafluoropropionic anhydride in an extractive derivatization procedure. The complex pattern of air pollutants after thermal degradation of a polyurethane polymer, based on toluene diisocyanate (TDI) and 3,3′-dichloro-4,4′-diaminodiphenylmethane (MOCA), was investigated. Substantial amounts of amines, isocyanates and aminoisocyanates, molecules containing both an amine and an isocyanate group, were found. Consideration must be given to these findings when using current methods for isocyanate and amine determination. The detection limits for isocyanates, amines and aminoisocyanates, essentially depending on the nitrogen content of the molecule, were about equal and in the order of 40–80 fmol.