Selective Detection of Carcinogenic Aromatic Diamines in Aqueous Solutions Using 4-(N-Chloroformylmethyl-N-methylamino)-7-nitro-2,1,3-benzoxadiazole (NBD-COCl) by HPLC.

Reaction conditions for the selective derivatization of three types of aromatic diamines without clean-up in an aqueous solution using 4-(N-chloroformylmethyl-N-methylamino)-7-nitro-2,1,3-benzoxadiazole (NBD-COCl) have been developed for simple, fast, and selective analysis by HPLC. The aromatic amines were derivatized to give di-NBD-CO-aromatic amines at 35°C for 5 min in a buffer solution at pH 5 containing a low acetonitrile concentration (0 - 400 ng/mL, n = 5, r >0.998). The retention times of these di-NBD-CO-aromatic amines were <5 min. Sample solutions containing aromatic amines, phenols, and an aliphatic amine were also prepared. Under the optimized reaction conditions (i.e., low acetonitrile content and acidic conditions), no derivatization of the phenols and the aliphatic amine was observed. These were related to the differences in the pKa values of the target substances, the organic solvent concentration, and the reaction solution pH. For the model system, a sulfuric acid-impregnated filter was spiked with the aromatic amines, phenols, and aliphatic amine prior to extraction, derivatization, and measurement by HPLC. Only aromatic amines were detected quantitatively, with no other compounds being observed.