Aerosols of Isocyanates, Amines and Anhydrides

This thesis presents methods for air sampling and determination of isocyanates, amines, aminoisocyanates and anhydrides. These organic compounds are generated during production or thermal degradation of polymers such as polyurethane (PUR) or epoxy. Isocyanates, amines and anhydrides are airway irritants known to cause occupational asthma. Some of the isocyanates and diamines are listed as human carcinogens. Isocyanates and anhydrides are reactive and needs to be immediately derivatized during sampling. Methods have been developed for determination of airborne isocyanates and aminoisocyanates using di-n-butylamine (DBA) as the reagent to form stable urea derivatives. Anhydrides were derivatized with DBA to stable amide derivatives. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) enabled instrumental detection limits as low as 10 attomoles. Methods for preparation and characterization of reference solutions of technical grade isocyanates, aminoisocyanates and anhydrides are presented. A nitrogen-selective LC-detector enabled the quantification of the DBA-derivatives. A novel sampler is presented. The sampler consists of a denuder in series with a three-stage cascade impactor and an end filter. The sampler made it possible to reveal the distribution of isocyanates between gas and different particle size fractions. During thermal degradation of PUR, isocyanates were associated to particle size fractions (<1 μm) that may penetrate to the lower airways. The distribution during 8 minutes changes noticeably. Gas phase toluene diisocyanates (TDI) and methylene diphenyl diisocyanate (MDI) become associated to small particles (<1 μm). Many workers are exposed to this kind of aerosol. As a reference method air-sampling was performed using an impinger filled with di-n-butylamine (DBA) in toluene, connected in series with a glass fiber filter. There was a good agreement between the denuder impactor sampler and the reference method.