DETERMINATION OF COMPLEX-MIXTURES OF AIRBORNE ISOCYANATES AND AMINES .1. LIQUID-CHROMATOGRAPHY WITH ULTRAVIOLET DETECTION OF MONOMERIC AND POLYMERIC ISOCYANATES AS THEIR DIBUTYLAMINE DERIVATIVES

An LC-UV method using dibutylamine (DBA) as derivatization reagent for airborne monomeric and polymeric isocyanates is presented, Isocyanate s were collected in impingers containing 0.01 mol l(-1) DBA in 10 mi o f toluene, Stable isocyanate-DBA (urea) derivatives were rapidly forme d in the sampling solution and the reaction was completed within 10 s, After evaporation of the solvent and excess reagent, the urea derivat ives were analysed using reversed-phase LC-UV at 240 nm, Linear calibr ation graphs were obtained for toluene 2,4- and 2,6-diisocyanate (TDI) and methylene diphenyl-4,4'-diisocyanate (MDI) in the range 0.4-20 nm ol ml(-1). The overall precision for a DBA solution spiked at concentr ations of 540 mu g l(-1) of 2,4-TDI, 540 mu g l(-1) of 2,6-TDI and 520 mu g l(-1) of 4,4'-MDI were found to be 1.1, 5.0 and 3.0% (n = 6); re spectively, The detection limit was 0.5-0.8 mu g m(-3) for a 151 air s ample, Ratio chromatograms between lambda(1) = 240 nm and lambda(2) = 254 nm demonstrated an increased selectivity, Interferences from morph oline, ethanol, phenol, toluene-2,4- and 2,6-diamine, 4,4'-methylenedi aniline and water were studied by spiking the sampling solution with 6 .2 mu mol of each chemical, corresponding to an air concentration of 1 0 ppm, No losses of the urea derivatives were found, Air samples of TD I were simultaneously collected with impingers containing 9-(N-methyla minomethyl)anthracene (n = 10) and DBA (n = 10), No significant differ ences between the results obtained with the two methods were observed, Sampling of isocyanates in the work environment based on derivatizati on with DBA was demonstrated to be a robust method, DBA is especially well suited for the determination of complex mixtures of airborne isoc yanates.