Determination of complex mixtures of airborne isocyanates and amines. Part 2. Toluene diisocyanate and aminoisocyanate and toluenediamine after thermal degradation of a toluene diisocyanate–polyurethane

Abstract

An LC–MS method is presented for the determination of thermal decomposition products of polyurethane. The method is based on the collection of air samples in midget impinger flasks containing 0.01 mol l^–1 dibutylamine (DBA) dissolved in toluene. DBA reacts with isocyanates to give urea derivatives. The amines simultaneously collected were derivatized with ethyl chloroformate (ET) to give urethane derivatives. Two isomers of toluene diisocyanate (2,4-and 2,6-TDI), toluene-2,4-and-2,6-diamine (TDA), three isomers of toluene aminoisocyanates and oligomers with two and three aromatic rings were determined in air containing thermal decomposition products of TDI–polyurethane. LC with gradient elution, at 0.5 ml min^–1 starting with acetonitrile–water (46 + 54) and ending after 14 min with acetonitrile–water (77.5 + 22.5) and atmospheric pressure ionization monitoring of positive ions demonstrated highly sensitive and selective determinations. Quantification was performed by monitoring the molecular ion [M + 1]⁺ of TDI–DBA and TDA–ET derivatives. The instrumental detection limit was 1 nmol l^–1 of TDI–DBA and 2 nmol l^–1 of TDA–ET. Linear calibration curves were obtained and the correlation coefficient was 0.9981–0.9996 for 50–500 nmol l^–1(n= 14). The over-all precision for samples spiked at a concentration of 500 nmol l^–1 of 2,4-and 2,6-TDA–ET and 2,4-and 2,6-TDI–DBA was 1.7, 1.6, 1.8 and 1.9%(n= 11), respectively.