Determination of organophosphorus pesticides in wastewater samples using vortex-assisted dispersive liquid–liquid microextraction with liquid chromatography–mass spectrometry

Abstract

A simple and rapid method for determination of azinphos-methyl, parathion-methyl and ethoprofos, group of organophosphorus pesticides in wastewater matrices, is presented. A chemometric approach for the optimisation of vortex-assisted dispersive liquid–liquid microextraction experimental conditions prior to liquid chromatography–mass spectrometry detection was applied. In this method, a high-density organic solvent (chloroform) was used as the extractant, with acetone as the disperser solvent. Vortexing was applied prior to centrifugation for phase separation of the organic phase (sedimented layer of extractant) and the aqueous layer. A two-level full factorial design (24) was employed initially for the screening process, and final optimisation of the significant parameters was performed using response surface methodology based on central composite design. The method performance characteristics investigated included linear dynamic range (LDR, 5–100 µg L−1) with a good correlation coefficient (> 0.999). The method precision expressed as intra-day and inter-day relative standard deviation (%RSD) was in the range of 7.8–8.2% and 8.1–9.4%, respectively. The influence of matrix was found to be negligible with recoveries ranging from 99.9 to 106.7%. The proposed method was then applied in real wastewater samples. Extraction recoveries performed at two spiking levels (25 and 100 µg L−1) in untreated (influent) and treated (effluent) wastewater matrices ranged between 94.95 and 119.47%.