Use of Continuous-Flow Microextraction and Liquid Chromatography for Determination of Phoxim in Water Samples

A novel liquid-phase microextraction method, continuous-flow microextraction (CFME), combined with high-performance liquid chromatography and variable-wavelength detection, has been used for determination of phoxim in water samples. Extraction is conducted in a home-made glass chamber. A 3-μL drop of n-hexane is injected into the chamber by means of a microsyringe and held at the outlet tip of a PTFE connecting tube. The sample solution flows through the extraction glass chamber, past the tube, and the solvent drop interacts continuously with the sample solution and extraction proceeds simultaneously. The effects of different extraction solvents, solvent drop volume, sample flow rate, extraction time, and addition of salt on extraction efficiency were studied. Under the optimum extraction conditions a linear calibration plot, correlation coefficient (R2) 0.9988, was obtained for phoxim in the concentration range 0.01 to 10 μg mL−1. The limit of detection (LOD) was 5 ng mL−1 and the relative standard deviation (RSD) at the 100 ng mL−1 level was 4.1%. Lake water and tap water samples were successfully analyzed by use of the proposed method.