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Multi‐residue analysis of N‐methylcarbamate pesticides and their hydrolytic metabolites in environmental waters by use of solid‐phase extraction and micellar electrokinetic chromatography

A method for the simultaneous separation and determination of N‐methylcarbamate pesticides and their hydrolytic metabolites by micellar electrokinetic chromatography (MEKC) was developed. A mixture of five pesticides (carbaryl, propuxur, carbofuran, aminocarb, and methiocarb) and their corresponding phenols was studied to optimize the separation of its components in terms of various electrophoretic parameters such as buffer type, pH and concentration, sodium dodecyl sulfate concentration, injection conditions, and applied voltage. Excellent separation of all ten analytes was achieved within about 20 min. The optimized method was used for determinations in environmental water samples. Sample volumes of 250 mL were first preconcentrated in the pesticides and metabolites by passage through a LiChrolut EN sorbent column and then further enriched by on‐column stacking. Dynamic ranges of 40 ng/L — 6 μg/L, limits of detection at the nanogram‐per‐liter level, and relative standard deviations from 2.6 to 7.4% were obtained. The proposed method surpasses high‐performance liquid chromatography (HPLC) in separation efficiency. In fact, it provides more expeditious separations and allows more flexible adjustment of the selectivity. Also, it enables the quantification for the analytes studied in this work with decreased limits of detection.