Simultaneous separation and preconcentration of phosalone and chlorpyrifos in fresh vegetables using ultrasound-assisted dispersive liquid–liquid microextraction and high performance liquid chromatography

Abstract

The pesticide residues in agricultural products and foods have become a serious concern. A simple, inexpensive, reliable and environmentally friendly method based on ultrasound-assisted dispersive liquid–liquid microextraction and the solidification of floating organic drops (UA-DLLME-SFO) followed by high performance liquid–liquid chromatography-ultraviolet detection (HPLC-UV) was developed for the simultaneous determination of phosalone and chlorpyrifos in fresh vegetables. Samples were homogenized and the extraction of the target analytes with acetone was carried out assisted by sonication. No clean-up or evaporation was required after extraction. Pre-concentration of the analytes from the acetone extract was done using a DLLME-SFO technique. 1-Undecanol was added in a micro-level volume as an extraction solvent in the DLLME-SFO procedure. Some effective parameters on extraction were studied and optimized. Under the optimum conditions, recoveries for different vegetables are in the range of 68–88%. The calibration graphs are linear in the range of 5–800 μg kg⁻¹ and limit of detection (LOD) values are in the range of 2–8 μg kg⁻¹. The repeatability (intra-day) and reproducibility (inter-day) for 50 μg kg⁻¹ of phosalone and 200 μg kg⁻¹ of chlorpyrifos in vegetables are in the range of 4.5–7.8% and 5.1–9.0%, respectively (n = 5). The method allowed the determination of OPPs in fruit and vegetables at lower concentrations than the migration limits established by the European Union. The obtained results show that UA-DLLME-SFO combined with HPLC-UV is a fast and simple method for the determination of pesticides and herbicides in fresh vegetables.