Optimization of the postcolumn hydrolysis reaction on solid phases for the routine high-performance liquid chromatographic determination of N-methylcarbamate pesticides in food products.
Various solid-phase materials were evaluated as catalysts for the postcolumn hydrolysis of N-methylcarbamate pesticides in a high-performance liquid chromatographic (HPLC) method for food products. Inexpensive magnesium oxide has been used for the first time in HPLC as a very efficient catalyst and as a good alternative for, e.g., expensive anion-exchange resins. The reaction mechanism and kinetics were studied through measurement of the reaction band broadening, which depends on the stationary phase, mobile phase composition and flow-rate, and reaction temperature. Also, relationships between carbamate structure and reactivity were examined. The usefulness of the optimized postcolumn system was thoroughly tested by application to crop sample analysis during an extended period of time. The range of application of the solid-phase reaction was extended to 22 carbamate pesticides and ten of their metabolites. For crop sample analysis, limits of determination in the range 1-10 ppb were obtained.