Ultrasound-assisted dispersive liquid–liquid microextraction combined with ion mobility spectrometry for the simultaneous preconcentration and determination of dimethoate and chlorpyrifos in fruit, vegetable, and water samples

A rapid, sensitive, and reliable method based on ultrasound- assisted dispersive liquid–liquid microextraction followed by ion mobility spectrometry analysis (UA-DLLME-IMS) is reported for the preconcentration and determination of chlorpyrifos and dimethoate in food and water. The sample pH, volume of dichloromethane (extraction solvent), sonication, and centrifuge time, salt effect and sample volume were individually optimized. Under the optimum conditions, the calibration curves were linear from 5 to 200 µg L−1 and 3 to 280 µg L−1. Limits of detection (LOD) of 1.3 and 0.8 µg L−1 were obtained for chlorpyrifos and dimethoate, respectively. The relative standard deviations at 20 μg L−1 (n = 5) for intra- and inter-day precision were 2.8% and 3.9% for chlorpyrifos and 4.1% and 4.6% for dimethoate, respectively. The procedure was validated for the determination of chlorpyrifos and dimethoate in food and water samples.