Simultaneous determination of amines and isocyanates in working atmospheres by gas-liquid chromatography.

A gas-liquid chromatographic method has been developed which permits trace analysis in a single run of amines and isocyanates occurring in relative concentrations of the order of 10,000:1. The amines were determined as free amines after alkalization of the sample and an extractive enrichment into toluene. The isocyanates were hydrolyzed to the corresponding amines during sampling in dilute sulphuric acid. This method gives the total isocyanate concentration. The use of a nitrogen sensitive detector and an alkali-treated packing, Pennwalt 223 with 4% KOH, are important prerequisites. Chromatographic parameters such as column liquid loading, injector impregnation and injector temperature were examined. Good separation between 2,4- and 2,6-toluenediamine isomers was obtained. The enrichment step was studied with respect to the degree of alkalization and to interferences from another amine present in large excess. The method was tested in the working atmospheres of two polyurethane foam factories. The substances determined were N-methylmorpholine, 1,4-diazabicyclo[2,2,2]octane and 2,4- and 2,6-toluenediisocyanates.