Diisocyanates (DIs) are widely used industrially. Measuring the total reactive isocyanate group (TRIG) is important because the isocyanate group (-NCO) is considered responsible for inducing sensitization. However, practical and cost-effective methods for occupational exposure measurement are limited due to the high reactivity of the -NCO and the complex composition and distribution of TRIG in workplace air. This study evaluated a method using 1-(2-methoxyphenyl) piperazine (MOPIP) as a derivatization reagent in an LC-UV/FLD analytical system. Hexamethylene diisocyanate (HDImono), 4,4′-diphenylmethane diisocyanate (MDImono) monomers, and a mixture of HDI oligomers (HDITRIG) were selected as model compounds. The results revealed that the response ratios of the two detectors (UV280/242 nm and UV242 nm/FLD) of HDImono are useful indicators for identifying HDITGIG. Using MOPIP-impregnated filters (MOPIP-GFF), HDImono, MDImono, and HDITRIG can be measured in the ranges of 20 to 20,000, 12 to 24,500 and 92 to 9,200 ng/filter, respectively. Furthermore, the MOPIP-GFF and DI samples were relatively stable at both 4℃ and room temperature. Overall, this method exhibited good reliability over a wide concentration range for airborne HDImono, MDImono, and HDITRIG. Moreover, it is more convenient for field investigations than other methods, using a stable, readily available derivatization reagent and conventional UV and fluorescence detectors.
Zhang et al. (Thu,) studied this question.