RESUMEN
To assess worker isocyanate exposures in a variety of processes involving the manufacture and use of surface coatings, polyurethane foams, adhesives, resins, elastomers, binders, and sealants, it is important to be able to measure airborne reactive isocyanate-containing compounds. Choosing the correct methodology can be difficult. Isocyanate species, including monomers, prepolymers, oligomers, and polyisocyanates, are capable of producing irritation to the skin, eyes, mucous membranes, and respiratory tract. The most common adverse health effect is respiratory sensitization, and to a lesser extent dermal sensitization and hypersensitivity pneumonitis. Furthermore, isocyanate species formed during polyurethane production or thermal degradation may also produce adverse health effects. Isocyanate measurement is complicated by the fact that isocyanates may be in the form of vapors or aerosols of various particle size; the species of interest are reactive and therefore unstable; few pure analytical standards exist; and high analytical sensitivity is needed. There are numerous points in the sampling and analytical procedures at which errors can be introduced. The factors to be considered for selecting the most appropriate methodology for a given workplace include collection, derivatization, sample preparation, separation, identification, and quantification. This article discusses these factors in detail and presents a summary of method selection criteria based on the isocyanate species, its physical state, particle size, cure rate, and other factors.
Asunto(s)
Contaminantes Ocupacionales del Aire/análisis , Monitoreo del Ambiente/métodos , Isocianatos/análisis , Cromatografía de Gases/métodos , Humanos , Hipersensibilidad/etiología , Isocianatos/efectos adversos , Isocianatos/química , Concentración Máxima Admisible , National Institute for Occupational Safety and Health, U.S. , Estados UnidosRESUMEN
An approach to sampling and analysis for total isocyanates (monomer plus any associated oligomers of a given isocyanate) in workplace air has been developed and evaluated. Based on a method developed by the Occupational Health Laboratory, Ontario Ministry of Labour, Ontario, Canada, isocyanates present in air are derivatized with a fluorescent reagent, tryptamine, in an impinger and subsequently analyzed via high-performance liquid chromatography (HPLC) with fluorescence detection. Excitation and emission wavelengths are set at 275 and 320 nm, respectively. A modification to the Ontario method was made in the replacement of the recommended impinger solvents (acetonitrile and 2,2,4-trimethylpentane) with dimethyl sulfoxide (DMSO). DMSO has the advantages of being compatible with reversedphase HPLC and not evaporating during sampling, as do the more volatile solvents used in the Ontario method. DMSO also may dissolve aerosol particles more efficiently during sampling than relatively nonpolar solvents. Several formulations containing diisocyanate prepolymers have been tested with this method in the laboratory. This method has been issued as National Institute for Occupational Safety and Health (NIOSH) Method 5522 in the first supplement to the fourth edition of the NIOSH Manual of Analytical Methods. This method is recommended for area sampling only due to possible hazards from contact with DMSO solutions containing isocyanate derivatives. The limits of detection are 0.1 microgram/sample for 2,4-toluene diisocyanate, 0.2 microgram/sample for 2,6-toluene diisocyanate, 0.3 microgram/sample for methylene bisphenyl diisocyanate, and 0.2 microgram/sample for 1,6-hexamethylene diisocyanate.
Asunto(s)
Contaminantes Ocupacionales del Aire/análisis , Cromatografía Líquida de Alta Presión/métodos , Monitoreo del Ambiente/métodos , Isocianatos/análisis , Exposición Profesional/análisis , Lugar de Trabajo , Calibración , Dimetilsulfóxido , Humanos , Reproducibilidad de los Resultados , SolventesRESUMEN
A recent analysis for total isocyanates in air using National Institute for Occupational Safety and Health Method 5521 presented difficulties in the identification of an oligomeric isocyanate species. Two problems were encountered during the analysis. A false negative response in the high performance liquid chromatography chromatogram was encountered in a majority of the field samples. An anomalous peak served to give a false positive in some of the field blanks and in some of the field samples. Through supplementing the ratio criterion of Method 5521 using the complete UV absorption spectrum from a photodiode array (PDA) UV detector, the two peaks were successfully identified. However, this need for additional data to identify an oligomeric isocyanate species raises the question of whether the ratio criterion of Method 5521 allows the qualitative identification of isocyanate oligomers.