An air-sampling method employing denuders coated inside with a chemisorptive stationary phase has been evaluated for analysis of the hazardous gaseous 2,4 and 2,6 isomers of toluene diisocyanate (TDI). The denuder stationary phase consisted of polydimethylsiloxane (SE-30) to which dibutylamine (DBA) was added as a reagent for derivatization of TDI. The accuracy and precision of sampling by means of denuders were shown to differ only slightly from those of the established impinger method. The denuder method was, however, also shown to be suitable for long-term measurements (up to 8 h). The limit of determination (LOD) of the method, including LC-APCI-MS-MS analysis, was found to be 1.9 microg m(-3) and 1.2 microg m(-3) for 2,4- and 2,6-TDI, respectively, for short-term measurements (15 min). Significant lower LOD was obtained for long-term measurements. This is well below the Occupational Safety and Health Administration (OSHA) 8-h TWA (time-weighted average) exposure limit, which is 40 microg m(-3) for the sum of the TDI isomers. The denuder method was also found to be robust and easy to handle. The samplers can be prepared several days before sampling with no loss in performance. The contents of denuders should, on the other hand, be extracted immediately after sampling to prevent degradation of the isocyanate derivatives formed.

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A system has been constructed and evaluated for generating aerosols from combustion or pyrolysis of various cross-linked polymers. The system consists of an aerosol generator and an aerosol chamber with a sampling compartment designed for various samplers and sampling probes. A geared electric motor assembly is used to lower a polymer strip into the controlled atmosphere of a quartz-lined furnace. The polymer used in this investigation was a polyurethane foam (PUF) based on toluene diisocyanate (TDI). Combustion of the PUF was conducted in filtered air at a temperature of 300 degrees C. The particle number concentration of the generated aerosol was measured by light scattering in the particle size range from 0.1 micron to greater than 5 microns. Air samples were collected periodically in impinger flasks using dibutylamine (DBA) in toluene as derivatization reagent. The TDI-DBA derivatives from the impinger samples were analyzed with high performance liquid chromatography. The aerosol generating system was found to generate a stable, reproducible, and predictable concentration of particles and TDI monomer. Three partial least squares models were created to evaluate the generator. The investigated responses were the TDI concentration, the particle number concentration, and the stability of the particle number concentration during the generating process. The factor with most impact on the concentrations of the generated aerosol was found to be the interaction between linear feeding rate of the polymer strip and the flow rate of combustion gas. For stability the linear feeding rate was the most important.