DETERMINATION OF COMPLEX-MIXTURES OF AIRBORNE ISOCYANATES AND AMINES - PART 5 - DETERMINATION OF LOW-MOLECULAR-WEIGHT ALIPHATIC ISOCYANATESAS DIBUTYLAMINE DERIVATIVES

A method is presented for the determination of low molecular weight al iphatic isocyanates, methyl isocyanate (MIC), ethyl isocyanate (EIC), propyl isocyanate (PIC) and butyl isocyanate (BIC), as their dibutylam ine (DBA) derivatives. The method is based on sampling in midget impin ger flasks containing 10 ml of 0.01 mol l(-1) DBA in toluene (as in Pa rts 1-4 in this series). The samples are analysed using liquid chromat ography-electrospray mass spectrometry (LC-ESP-MS) or gas chromatograp hy-mass spectrometry using chemical ionisation with ammonia, monitorin g positive ions (GC-PCI), Quantification was effected by monitoring th e molecular ions MH+. Aliquots of 10 ml of toluene, solutions containi ng 0.01 mol l(-1) DBA were spiked with 0.03-0.85 mu g Of MIC-, EIC-, P IC- and BIC-DBA, The correlation coefficients for LC-ESP-MS were in th e range 0.9952-0.9999 (n = 14). The repeatability (RSD) was in the ran ge 0.37-1.2% (0.12-0.34 mu g ml(-1), n = 10), The instrumental detecti on limit for MIC was about 15 mu g l(-1), which corresponds to about 0 .5 mu g m(-3) in a 15 l air sample. The correlation coefficients for G C-PCI were in the range 0.9913-0.9990. The repeatability (RSD) was in the range 1.1-4.9% (0.12-0.34 mu g ml(-1), n = 10), The instrumental d etection Limit for MIC was about 0.2 mu g l(-1), which corresponds to about 0.05 mu g m(-3) in a 15 l air sample. Using electron ionisation, the instrumental detection limit for MIC was about 10 mu g l(-1). No derivatisation reaction losses were seen when the derivatization react ion between PIC and DBA took place in the presence of morpholine, prop ylamine, ethanol, phenol and water. When mineral wool with a phenol-fo rmaldehyde-urea resin was thermally degraded, 0.1% m/m of MIC was rele ased, In air samples taken on top of a new electric oven insulated wit h mineral wool, MIC was found in the range 0.13 mg m(-3). No MIC in ai r was found from a pre-heated oven.