Determination of Organochlorine Pesticides in Aqueous Samples Using Dispersive Liquid-Liquid Microextraction

Background: Organochlorine pesticides (OCPs) have been used worldwide in agriculture because of their low prices and effectiveness against insects. However, their rates of chemical and biological degradation are slow. OCPs are still widely detected in the environment and in organisms. Therefore, it is necessary to develop sensitive and accurate methods to investigate the amounts of OCPs in environmental samples. Objective: We present herein two liquid phase microextraction methods, namely shaker-assisted (SADLLME) and surfactant-assisted dispersive liquid liquid microextraction (SDLLME), for the determination of organochlorine pestcides in water samples. Method: Gas chromatography coupled with an electron capture detector (GC-ECD) was employed. Various factors that affect extraction efficiency, such as the type and volume of the extraction solvent, salt addition, the type and volume of surfactant solution in SDLLME, and the effect of shaking time in SADLLME, have been evaluated. Results: Under the optimized conditions, the enrichment factors ranged from 948 to 2241 for SADLLME and from 695 to 1656 for SDLLME. The linear range was from 7 to 5000 ng L-1 and the limit of detection (LOD) ranged from 1.4 to 3.1 ng L-1 for SADLLME. The linear range was from 5 to 1000 ng L-1 and the limit of detection (LOD) ranged from 1.6 to 2.1 ng L-1 for SDLLME. The absolute recoveries and relative recoveries were 19.8-49.3% and 80.8-110% for river water, 19.6-47.8% and 76.9-116% for lake water, and 15.3-46.9% and 77.5-102% for irrigating water, by SADLLME and SDLLME respectively. Conclusion: These methods, employing minimal amounts of extraction solvent and surfactant solution, could be used to accomplish efficient extraction in 3 min and achieved high enrichment factors. For the analysis of environmental samples, they were both successfully applied to the preconcentration of trace OCPs in water samples.