Application of tryptamine as a derivatizing agent for airborne isocyanate determination. Part 4. Evaluation of major high-performance liquid chromatographic methods regarding airborne isocyanate determination with specific investigation of the competitive rate of derivatization

Abstract

Several amines were investigated to determine their competitive rates in the derivatization of isocyanates. The amines studied included N-(p-nitrobenzyl)-N-propylamine, 1-(2-pyridyl)piperazine, 1-(2-methoxyphenyl)piperazine, N-ω-methyl tryptamine and tryptamine. Phenyl isocyanate, which might find application in future studies on sampling isocyanate vapour on solid absorbents, because it possesses a much higher vapour pressure than any of the industrially used isocyanates, was employed as the reference isocyanate. This approach was adopted because only the relative, rather than actual, rates of derivatization were of interest. By comparing the significant features of the methods for the determination of isocyanates using high-performance liquid chromatographic techniques, it was concluded that the proposed method, which uses tryptamine (and possibly N-ω-tryptamine), was the most promising for practical application. The theoretical background of the proposed method was based on the isolation of a selected π-system in a derivative for specific detection. This approach should be applicable to other areas involving analysis with chromatographic techniques. The competitive rate study has also provided a better assessment in selecting a particular amine for further research in personal sampling of isocyanates on amine-coated solid absorbents.