Spectrophotometric determination of common aromatic diisocyanates using 4-nitrobenzenediazonium tetrafluoroborate in dimethyl sulphoxide

Abstract

Monomeric aromatic diisocyanates react with a solution of 4-nitrobenzenediazonium tetrafluoroborate in dimethyl sulphoxide (DMSO) to yield characteristically coloured products. Detection limits for toluene-2,4-diyl diisocyanate and 4,4′-methylenebis(phenyl isocyanate) dissolved in DMSO are 1.0 and 0.8 µg ml^–1, respectively. Use of a polar aprotic solvent (DMSO) retards the decomposition of the diazonium indicator and increases the number of different diisocyanate formulations that can be analysed.