Dispersive liquid-liquid microextraction method based on solidification of floating organic drop for extraction of organochlorine pesticides in water samples

A new simple and rapid dispersive liquid-liquid microextraction method has been developed for the extraction and analysis of organochlorine pesticides (OCPs) in water samples. The method is based on the solidification of a floating organic drop (DLLME-SFO) and is combined with gas chromatography/electron capture detection (GC/ECD). Very little solvent is required in this method. The disperser solvent (200 mu L acetonitrile) containing 10 mu L hexadecane (HEX) is rapidly injected by a syringe into the 5.0 mL water sample. After centrifugation, the fine HEX droplets (6 +/- 0.5 mu L) float at the top of the screw-cap test tube. The test tube is then cooled in an ice bath. After 5 min, the HEX solvent solidifies and is then transferred into a conical vial, where it melts quickly at room temperature, and 1 mu L of it is injected into a gas chromatograph for analysis. Under optimum conditions, the enrichment factors and extraction recoveries are high and range between 37-872 and 82.9-102.5%, respectively. The linear range is wide (0.025-20 mu gL(-1)), and the limits of detection are between 0.011 and 0.11 mu gL(-1) for most of the analytes. The relative standard deviation (RSD) for 1 mu gL(-1) of OCPs in water was in the range of 5.8-8.8%. The performance of the method was gauged by analyzing samples of lake and tap water. (C) 2009 Elsevier B.V. All rights reserved.