Development of a new approach for total isocyanate determination using thereagent 9-anthracenylmethyl 1-piperazinecarboxylate

Diisocyanates and polyisocyanates are widely used in the manufacture of pol yurethane materials and coatings. Exposure to airborne isocyanate species i s known to cause respiratory disorders. Measurement of isocyanate exposure levels has traditionally involved collection and derivatization of isocyana te species in an air sample followed by reversed-phase HPLC analysis. HPLC analysis of isocyanate samples is complicated for several reasons. Air samp les may contain isocyanate species of very different reversed-phase retenti on (e.g., monomeric and polymeric isocyanates) and some species may not eve n be chromatographable. Also, pure analytical standards are available only for monomeric isocyanates, so non-monomeric isocyanate species are typicall y quantified based on the response of monomer standards, which assumes that the non-monomeric species have the same response factor as the monomer. Fi nally, the analysis of the raw chromatographic data containing many peaks i s labor intensive. The method described here would circumvent many of the l imitations of traditional methods. In this method, isocyanate species are d erivatized with 9-anthracenylmethyl 1-piperazinecarboxylate (PAC) upon coll ection. At this point, a portion of the sample can be analyzed for individu al components of interest (such as monomers) and/or a portion can be treate d with a reagent that converts all PAC derivatives to a single analyte. Qua ntification of this analyte gives a measure of total isocyanate group. This paper examines the reactivity of PAC, the separation of PAC derivatives fr om excess PAC reagent, the conversion of PAC derivatives to a single analyt e and the HPLC determination of this analyte and PAC derivatives of several monomeric isocyanates.