Improved Homogeneous Liquid-Liquid Extraction Combined with GC-ECD for the Determination of Organochlorinated Pesticides in Water

In this study, improved homogeneous liquid-liquid extraction (HLLE), equipped with GC-ECD has been developed for the extraction and determination of organochlorinated pesticides (OCPs) in water. The phase separation phenomenon occurred by temperature in a ternary solvent (water/methanol/chloroform) system. Several factors influencing the extraction efficiency were investigated and optimized with orthogonal array design. Furthermore, in this study, for the first time, before immiscible organic phase formation, different volumes of deionized water were subjected to homogeneous solution to investigate the effect of this factor on the extraction performance of HLLE. Optimal results were as follows: volume of the extracting solvent (chloroform), 50 mu L; volume of the consolute solvent (methanol), 1.2 mL; volume of the sample, 2.5 mL; volume of the deionized water, 0.5 mL; time of centrifuge, 7 min. Under the optimum conditions, repeatability was obtained by spiking OCPs at concentration level of 20 mu g L-1, the RSDs varied between 4.8 and 10.7% (n = 4). The limits of detection of 0.02-0.12 mu g L-1 were obtained for the OCPs. Enrichment factors and the extraction percent of the studied compounds were in the range of 240-300 and 69.2-84.0%, respectively. Finally, the results of the proposed HLLE method were compared with the same HLLE method without addition of deionized water. The results indicated that the proposed method has higher enrichment factors and lower detection limits.