Determination of thiophanate-methyl and chlorotoluron in water samples by improved single-drop microextraction coupled with high-performance liquid chromatography

Abstract An improved single-drop microextraction method for the determination of thiophanate-methyl and chlorotoluron in water samples was developed, with analysis by high-performance liquid chromatography-ultraviolet detection (HPLC-UV). Several parameters such as solvent type, salt concentration, stirring rate, extraction time, pH and organic drop volume were investigated. The optimum experimental conditions found were: 20 µL 1-octanol, 10% (w/v) NaCl, 600 rpm stirring rate, 40 min extraction time, neutral sample pH and 5 mL water sample. Under the optimum conditions, the enrichment factors were 45.3 and 107.0 folds for thiophanate-methyl and chlorotoluron, respectively. The method exhibited a wide linear range (1–100 µg L−1), reasonable detection limits (0.35 µg L−1) and suitable repeatability (RSD < 9.6%) for both analytes. The proposed method was validated with three real water samples fortified at two levels, and reasonable spiked recoveries were achieved in the range of 84.0% ∼ 110.3%. The experimental results indicated that the improved SDME was a simple, reliable and convenient technique and could easily be used for the enrichment of other pollutants. Keywords: improved single-drop microextractionHPLC-UVthiophanate-methylchlorotoluron Acknowledgement This work was jointly supported by the State High Tech Development Plan (2006AA06Z424), the Creative Talented Person's Fund of Henan Province (High Teach [2005]-126) and grants from the Henan Key Laboratory for Environmental Pollution Control.