Dispersive liquid–liquid microextraction followed by high-performance liquid chromatography for the determination of three carbamate pesticides in water samples

Abstract

A simple, rapid and efficient method, dispersive liquid–liquid microextraction (DLLME) in conjunction with high-performance liquid chromatography (HPLC), has been developed for the determination of three carbamate pesticides (methomyl, carbofuran and carbaryl) in water samples. In this extraction process, a mixture of 35 µL chlorobenzene (extraction solvent) and 1.0 mL acetonitrile (disperser solvent) was rapidly injected into the 5.0 mL aqueous sample containing the analytes. After centrifuging (5 min at 4000 rpm), the fine droplets of chlorobenzene were sedimented in the bottom of the conical test tube. Sedimented phase (20 µL) was injected into the HPLC for analysis. Some important parameters, such as kind and volume of extraction and disperser solvent, extraction time and salt addition were investigated and optimised. Under the optimum extraction condition, the enrichment factors and extraction recoveries ranged from 148% to 189% and 74.2% to 94.4%, respectively. The methods yielded a linear range in the concentration from 1 to 1000 µg L⁻¹ for carbofuran and carbaryl, 5 to 1000 µg L⁻¹ for methomyl, and the limits of detection were 0.5, 0.9 and 0.1 µg L⁻¹, respectively. The relative standard deviations (RSD) for the extraction of 500 µg L⁻¹ carbamate pesticides were in the range of 1.8–4.6% (n = 6). This method could be successfully applied for the determination of carbamate pesticides in tap water, river water and rain water.

Keywords:

• dispersive liquid–liquid microextraction
• high-performance liquid chromatography
• carbamate pesticides
• water samples

Acknowledgements

This work was supported by the Henan Natural Science Foundation (No. 0511022400) and the Key Project of Henan Province (No. 0422031200).