Liquid Chromatographic Residue Analysis of Carbaryl Based on a Post-Column Catalytic Reactor Principle and Fluorigenic Labelling

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Abstract
A method is described for the residue analysis of carbaryl in polluted water samples. The technique is based on catalytic hydrolysis of the carbaryl on anion exchangers followed by fluorescence detection of the α-naphthol or the OPA derivative of the methyl amine. A low cost 200 mesh Amberlite strong anion exchanger can be used for this purpose when coupled to the OPA reaction detector. Combining this approach with on-line preconcentration and clean-up on an 3P-18 loaded precolumn can provide a powerful tool for automated residue analysis of carbaryl (and other N-methyl carbamates) in polluted water sources. Recoveries in the order of 100% are reported. The reproducibility of the technique is better than 2% rel. st. dev. Detection limits are 0.4–2 ng per injection for carbaryl depending on the system and linearity of response is more than two orders of magnitude with r = 0.9998. The selectivity and sensitivity of this method permits residue analysis at the sub ppb concentration level in heavily polluted water samples. Data on hydrolysis yields and band broadening as a function of residence time and temperature in the reactor are given.