Evaluation of 9-Methylamino-Methylanthracene as a Chemical Label for Total Reactive Isocyanate Group: Application to Isocyanate Oligomers, Polyurethane Precursors, and Phosgene

9-Methylamino-methylanthracene (MAMA) is a secondary amine compound which can be used for derivatization and quantitation of isocyanate compounds by HPLC with detection by fluorescence and ultra-violet light absorbance The compound has potential as a chemical label for determination of airborne total reactive isocyanate group (TRIG) compounds arising from partially polymerized polyurethanes and thermal decomposition products of fully cured polyurethanes Six isocyanate oligomers and polyurethane precursors based on methylene-bis-(phenylisocyanate) (MDI), 1,6-hexamethylene-diisocyanate (HDI), and 2,4- and 2,6-toluenediiosocyanate (TDI) were assayed for isocyanate content using MAMA reagent After reaction of isocyanate with MAMA, the urea derivatives were analyzed by reversed phase HPLC using three detection / quantitation modes: fluorescence with excitation at 245 nm and emission at 414 nm, UV absorbance at 245 nm and UV absorbance at 370 nm. The ratio of absorbance at 245 nm and at 370 nm identified multiple peaks originating from isocyanate-containing compounds in each sample. The total amount of TRIG in each sample was then quantitated by absorbance of these peaks at both of the UV wavelengths. For the test samples, observed recoveries of TRIG by MAMA-HPLC assay ranged from 96 to 105%, in comparison to a reference titration assay. The technique was also evaluated for chemical interference from phosgene gas. A single compound was found after reaction of MAMA with phosgene which responded as two equivalents of TRIG.