Postcolumn photolysis of pesticides for fluorometric determination by high-performance liquid chromatography

A high-performance liquid chromatography postcolumn reaction detector that employs UV photolysis with an optional reaction by using o-phthalaldehyde-2-mercaptoethanol (OPA-MERC) followed by fluorescence detection was found to be useful for several classes of pesticides. In the presence of the OPA-MERC reagent, most carbamates, carbamoyl oximes, carbamothioic acids, and substituted ureas gave a sensitive response while the response of dithiocarbamates, phenylamides, and phenylcarbamates varied. The response of most of the pesticides tested was significantly affected by the solvent used. Method detection limits for aldicarb sulfoxide, aldicarb, propoxur, thiram, and neburon in ground water were 2.5, 2.3, 3.3, 3.8, and 2.0 ..mu..g/L, respectively. In the absence of OPA-MERC reagent, several of the substituted aromatic compounds also gave strong fluorescence after photolysis. This detector is applicable to a broad range of nitrogenous pesticides.