Development of a novel derivatization reagent for the sampling and analysis of total isocyanate group in air and comparison of its performance with that of several established reagents.

R P Streicher, J E Arnold, M K Ernst, C V Cooper

Index: Am. Ind. Hyg. Assoc. J. 57(10) , 905-13, (1996)

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Abstract

Analytical reference standards generally are not available for non-monomeric isocyanate species, making accurate identification and quantitation by high-performance liquid chromatography (HPLC) difficult. A successful derivatizing reagent must react rapidly with all isocyanate groups, the derivatized isocyanate must be detectable selectively and at very low levels, and the detector used for quantitation must give a response proportional to the number of derivatized isocyanate groups present. A novel derivatizing reagent, 1-(9-anthracenylmethyl)piperazine (MAP), was prepared in an attempt to achieve these goals. Derivatives were prepared by reacting five mono- and difunctional isocyanates with MAP and three other established isocyanate derivatizing reagents. These reagents included 1-(2-methoxyphenyl)piperazine (MOPP),9-(methylaminomethyl)anthracene (MAMA), and tryptamine (TRYP). The relative reactivities of MAP, MOPP, TRYP, and MAMA with phenyl isocyanate were found to be 100, 88, 30, and 25, respectively. Average molar absorptivities at the absorbance maxima +/- compound-to-compound variabilities were, for MAP: 1.47 x 10(5) +/- 3.50%; MAMA: 1.38 x 10(5) +/- 7.07%: and TRYP: 3.98 x 10(4) +/- 13.1%. Average fluorescence responses were, for MAP: 100 +/- 32.6%; MAMA: 41.0 +/- 58.8%; and TRYP: 2.27 +/- 15.6%. A comparison of MAP and MOPP ureas by HPLC/ultraviolet (UV)/electrochemical (EC) gave average responses for UV, EC, and EC/UV for MAP: 117 +/- 7.3%, 52.1 +/- 6.6%, and 0.447 +/- 10.7%, respectively; for MOPP: 24.3 +/- 62.5%, 76.7 +/- 28.5%, and 4.28 +/- 59.1%, respectively. The favorable performance of MAP warrants its further study as a reagent for the determination of total isocyanate group in air.