Comparison of denuder and impinger sampling for determination of gaseous toluene diisocyanate (TDI)

Abstract

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.

A chemosorptive cylindrical denuder designed for personal exposure measurements of isocyanates–evaluation on generated aerosols of 4,4′-methylenediphenyl diisocyanate

“…The study was applied to generated aerosols of the highly reactive 4,4 0 -MDI, and the performance of the system was evaluated in the laboratory by comparison with impinger sampling. In two earlier studies, the denuder tube has been evaluated, without the filter assembly, for sampling vapour of toluene diisocyanate (TDI) isomers 20 and a mixture of TDI, hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI) vapour. 21 Experimental Chemicals Toluene (499.8%), acetonitrile (499.7%) and dichloromethane (for organic trace analysis) were purchased from Merck (Darmstadt, Germany), toluene (analytical grade) from Scharlau Chemie (Barcelona, Spain) and pentane (analytical reagent) from Lab-Scan Ltd (Dublin, Ireland).…”

“…The generating apparatus was the same as that used for TDI in an earlier study. 20 According to results obtained using the impinger system, the concentration generated was 0.3 mg m À3 (CV ¼ 14%, n ¼ 3). Both the denuder and the impinger were connected to a filter.…”

Evaluation of denuder sampling for a mixture of three common gaseous diisocyanates

“…The generation chamber used has been described earlier [22]. The atmosphere generated was approximately 24 µg m -3 (3 ppbv) of gaseous TDI, 38 µg m -3 (5 ppbv) of gaseous HDI and 17 µg m -3 (2 ppbv) of gaseous IPDI, giving a total of 79 µg m -3 (10 ppbv) of isocyanates.…”

“…4 mm) is somewhat smaller compared to the annular denuder sampler used by Rando et al (240 mm, 24 mm). We have previously described and evaluated this method for gaseous toluene diisocyanate (TDI) [22]. In this study the evaluation is expanded to include a mixture of three common gaseous diisocyanates, TDI, hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), at individual concentrations near or slightly lower than the 8-hour Swedish OEL of 5 ppbv (34-46 µg m -3 ).…”

Aprimoramento do poliuretano a base de óleo de mamona na manufatura de Madeira Laminada Colada (MLC) de Cupressus lusitanica, Corymbia maculata e Hevea brasiliensis

“…(6) R52, R53 -Nocivo para os organismos aquáticos Nordqvist (2001) Figura 10 -Tipos de emendas longitudinais (a) emenda de topo, (b) emenda bisselada, (c) emenda dentada horizontal e (d) emenda dentada vertical Fonte: Macedo (1996) Figura 11 -Exemplo de emenda dentada (finger-joint) utilizada em MLC (d) Colagem das peças: O processo de colagem, tipo de adesivo, pressão são fatores que podem interferir na qualidade e durabilidade do produto final. Os principais tipos de adesivos utilizados são fenol-formaldeido e resorcinolformaldeído.…”