Development of a New Magnetic Dispersive Solid-Phase Microextraction Coupled with GC-MS for the Determination of Five Organophosphorus Pesticides from Vegetable Samples

Abstract

A magnetic dispersive solid-phase microextraction procedure (MDμ-SPE) was developed to extract organophosphorus pesticides (OPP), including ethion, chlorpyrifos, diazinon, malathion, and fenitrothion, from vegetable samples before their analysis with gas chromatography/mass spectroscopy (GC/MS). Magnetic graphene@Fe3O4@SiO2@TiO2 nanocomposites were synthesized as a unique sorbent using the sol-gel and co-precipitation procedures. The ability of the prepared sorbent to extract the analytes was compared with several other sorbents. Effective factors in the MDμ-SPE method were thoroughly optimized by one factor at a time and the experimental design approach. Under the optimum condition of the OPP determination, the calibration curves were linear over a wide range of analyte concentrations with the correlation coefficient (R2) between 0.995 and 0.9986. Besides, the method showed high preconcentration factors (PF ≥ 217) and suitable relative standard deviations (RSD ≤ 4.73). Limit of detections (LODs) and limit of quantitations (LOQs) were in the range of 0.06-1.49 and 0.2-4.96 ng mL−1 for water sample analysis, respectively. Application of the method for the determination of the analytes in real samples such as tomato and lettuce samples indicated the method is proper for the OPP measurement in the vegetable samples with a recovery percentage between 93.89 and 106.67% and a relative standard deviation of less than 5.77%. The procedure for the residue determination of organophosphorus pesticides has various advantages such as no need for centrifugation step to the sorbent separation, low sorbent and sample solution consumption, high sensitivity, and low analysis time.