Solid-phase extraction for the determination of dimethoate in environmental water and soil samples by Micellar Electrokinetic Capillary Chromatography (MEKC)

A micellar electrokinetic chromatography (MEKC) procedure has been developed for the analysis of dimethoate (DM) in environmental water and soil samples, using solid phase extraction (SPE) as a clean-up and pre-concentration technique to improve selectivity and DM detection limits. The limit of quantification (LOQ) was 1 mug/mL for direct injection and 3 ng/mL after the SPE pre-concentration procedure. Within-run and between-day reproducibility studies performed at 0.02, 0.05, and 0.2 mug/mL indicated that the procedure was indeed reproducible. Quantification was by UV detection at 200 run. The capillary electrophoresis (CE) method proposed uses sodium borate 100 mM with sodium dodecyl sulfate 50 mM, pH 8.4 as a buffer. The method was simple and fast, with good recoveries, which on average ranged from 82 to 92% with a relative standard deviation of 7% or less for water and soil samples fortified at 10, 20, 30, and 300 ng/mL. Our results show CE to be a powerful analytical tool for the determination of DM in environmental water and soil samples.