Evaluation of tryptamine in an impinger and on XAD-2 for the determination of hexamethylene-based isocyanates in spray-painting operations

Tryptamine was evaluated as a reagent for derivatizing hexamethylene diisocyanate (HDI) monomer and oligomers during actual spray-painting operations. In one side-by-side sampling study, an impinger filled with 1-(2-methoxyphenyl)piperazine in toluene was compared with a second impinger filled with tryptamine in dimethyl sulfoxide (DMSO). The amount of HDI monomer obtained was below the limit of quantification for both impingers. The amount of HDI oligomer obtained when using 1-(2-methoxyphenyl)piperazine in toluene was comparable to the amount obtained when using an impinger filled with tryptamine in DMSO. In a second side-by-side sampling study, a tryptamine-coated XAD-2 resin was used as a sorbent. The relative collection efficiency of the tryptamine-coated XAD-2 resin was on average 60% of the value obtained using an impinger filled with tryptamine in DMSO. The results indicate that using an impinger filled with tryptamine in DMSO gives higher concentrations of isocyanate than a tryptamine-coated XAD-2 sorbent for HDI monomer and oligomer.