Improved Method for Determination of Traces of Isocyanates in Working Atmospheres by High Performance Liquid Chromatography

Abstract

Isocyanates common in industrial environments were converted to urea derivatives by reaction with N-4-nitrobenzyl-N-n-propylamine. The urea derivatives were analyzed by high performance liquid chromatography on a bonded octadecylsilyl phase using isocratic elution with acetonitrile-water 75:25 v/v. The water phase contained 1% triethylamine and was adjusted to pH 3.0 with phosphoric acid. The method was applied to toluene 2,4- and 2,6-diisocyanate (2,4- and 2,6-TDI), hexamethylene diisocyanate (HDI), 4,4′-diphenylmethane diisocyanate (MDI) and Desmodur N 75 (DN 75). Comparison with previous liquid chromatographic methods shows that the elution time is about halved and the detection limits about five times lower in our case.