RESUMEN
The application of tryptamine to derivatize airborne isocyanates has been evaluated and adopted by the National Institute for Occupational Safety and Health (NIOSH) as the latest isocyanates regulatory method (Method 5522) in the USA. Method 5522 uses dimethyl sulfoxide (DMSO) as the impinger solvent in which tryptamine is dissolved to sample isocyanates for analysis. Since DMSO is both extremely hygroscopic and corrosive, it is not a satisfactory solvent for impinger air sampling of isocyanates. The high boiling and freezing points also present some distinct drawbacks. In a search for a suitable impinger solvent, the efficiencies of various solvents, which all were potentially more suitable for sampling isocyanates viz., N,N'-dimethylformamide, butyl acetate, isobutyl acetate, sec-butyl acetate, tert-butyl acetate and octane, were investigated. Simulated air sampling was conducted on two commonly used isocyanates in industry, hexamethylene diisocyanate (HDI) and toluene diisocyanate (TDI), which were vaporized and sampled into impingers containing dissolved tryptamine. Butyl acetate and octane were found to be most suitable for using as impinger solvents. Recoveries of isocyanates at two concentration levels of HDI and TDI were 93.4-108% in comparison with those of using DMSO.
Asunto(s)
Contaminantes Ocupacionales del Aire/análisis , Isocianatos/análisis , Triptaminas , Cromatografía Líquida de Alta Presión , Dimetilsulfóxido , Estudios de Evaluación como Asunto , SolventesRESUMEN
An analytical method for monitoring 4,4'-methylenebis(2-chloroaniline) (MOCA) in urine was developed. The MOCA extract from a urine sample was derivatized with pentafluoropropionic anhydride and subsequently cleaned-up via TLC before being analysed by a gas chromatograph equipped with an electron capture detector. Heptafluorobutyric anhydride derivatized MOCA was used as the internal standard during quantification. The method showed that the analytical interferences are effectively minimized by using the TLC technique for sample clean-up. Recoveries of spiked MOCA in urine at levels of 7.5, 22 and 62.5 micrograms dm-3 were all over 90% with the limit of detection determined to be 1 microgram dm-3. Confirmation of MOCA in a urine sample was performed by using a gas chromatograph mass spectrometer in negative-ion chemical ionization mode.
Asunto(s)
Metilenobis (cloroanilina)/aislamiento & purificación , Cromatografía en Capa Delgada/métodos , Cromatografía de Gases y Espectrometría de Masas/métodos , Humanos , Indicadores y Reactivos , Sensibilidad y EspecificidadRESUMEN
Determination of total airborne isocyanates using tryptamine as the derivatising agent was investigated. Tryptamine derivatised isocyanates were analysed by reversed-phase high-performance liquid chromatography (HPLC). The column was equipped with dual detectors of fluorescence emission and amperometric oxidation. The characteristics of fluorescence emission and amperometric oxidation of tryptamine were retained even after its reaction with isocyanates. With this unique behaviour, all tryptamine derivatised isocyanates can be quantified using HPLC by employing a single, pure derivative, such as tryptamine derivatised hexamethylene diisocyanate as the calibration standard. This is especially important for analysing polymeric isocyanates when identical calibration standards are not always available. The applicability of this method for air sampling was evaluated by comparison with the established method of Bagon et al. involving 1-(2-methoxyphenyl)piperazine. Simulation of air sampling was performed in a Test Atmosphere Generation System by the vaporisation of toluene diisocyanate. Satisfactory results were obtained, indicating the applicability of this technique for the determination of total airborne isocyanates.