Optimization of solid-phase extraction and solid-phase microextraction for the determination of alpha- and beta-endosulfan in water by gas chromatography-electron-capture detection.

Abstract

Water contamination due to the wide variety of pesticides used in agriculture practices is a global environmental pollution problem. The 98/83/European Directive requires to measure residues of pesticides at a target concentration of 1.0 microg/l in surface water and 0.1 microg/l in drinking water. In order to reach the level of detection required, efficient extraction techniques are required. Although solid-phase extraction (SPE) is the most common technique for isolation and concentration of pesticides from water, solid-phase microextraction (SPME) is being increasingly applied for this purpose. In this study, a direct-SPME procedure has been developed for the determination of alpha-endosulfan and beta-endosulfan in waters; experimental parameters such as selection of SPME coating, effect of temperature, effect of salt addition, optimization of the sample volume, adsorption and desorption profiles and desorption temperature were studied and optimized. Analytical parameters such as linearity, precision, detection and quantitation limits, and matrix effects for SPE and SPME methods were evaluated for comparison purposes with the aim of selecting the most appropriate for a certain application. Both extraction techniques, SPE and SPME, were followed by gas chromatography with electron-capture detector.