monocrotophos and dimethoxon

This article presents a novel application of dispersive microextraction based on "magnetic water" (m-water) for the purification of organophosphorus pesticides (methamidophos, omethoate, monocrotophos) from cold-pressed vegetable oils. In the present study, a trace amount of water (extractant) was adsorbed on bare Fe₃O₄ by hydrophilic interaction to form m-water. Rapid extraction can be achieved while the m-water is dispersed in the sample solution with the aid of a vigorous vortex. After extraction, the analyte-adsorbed m-water can be readily isolated from the sample solution by a magnet, which could greatly simplify the operation and reduce the whole pretreatment time. Several parameters affecting the extraction efficiency were investigated, and under the optimized conditions, a simple and effective method for pesticide analysis was established by coupling with gas chromatography/mass spectrometry (GC/MS). The linearity range of the proposed method was 2-100 ng/g with satisfactory correlation coefficients (R) of 0.9997-0.9998, and the limits of quantification (LOQ) for the target compounds were in the range of 0.70-1.27 ng/g. In addition, the reproducibility was obtained by evaluating the intra- and interday precisions with relative standard deviations (RSDs) less than 7.2% and 6.5%, respectively. Finally, the established "magnetic water" microextraction method was successfully applied for the determination of pesticide residues in several kinds of cold-pressed vegetable oils.

Topics: Analytic Sample Preparation Methods; China; Dimethoate; Food Contamination; Food Inspection; Gas Chromatography-Mass Spectrometry; Liquid Phase Microextraction; Magnetic Phenomena; Monocrotophos; Organophosphorus Compounds; Organothiophosphorus Compounds; Pesticide Residues; Pesticides; Plant Oils; Water

A method combining hydrophilic interaction liquid chromatography (HILIC) with tandem mass spectrometry (MS/MS) was developed for the determination of polar organophosphorus pesticides (OPPs; acephate, methamidophos, monocrotophos, omethoate, oxydemeton-methyl, and vamidothion) in water samples. To extract the polar OPPs and minimize matrix effects from the water sample, an activated carbon cartridge was used for pretreatment. After pretreatment of the water sample, the eluate from the activated carbon cartridge was directly injected into the HILIC/MS/MS system. The OPPs were separated on an Atlantis HILIC silica column by isocratic elution with a mixture of acetonitrile, isopropanol, and ammonium formate buffer as a mobile phase, and they were detected by positive electrospray ionization MS/MS in the selected reaction monitoring mode. The method was validated at 0.05, 0.5, and 5 microg/L levels in water samples, and the recoveries of polar OPPs were between 76.4 and 98.6%. The limits of detection were between 0.13 and 1.0 pg on-column, and the limits of quantification were between 0.43 and 3.4 pg on-column. The method can be applied to the determination of trace amounts of OPPs in environmental water samples.

Topics: 2-Propanol; Acetonitriles; Buffers; Chromatography, Liquid; Dimethoate; Formates; Molecular Structure; Monocrotophos; Organothiophosphorus Compounds; Pesticides; Phosphoramides; Reference Standards; Reproducibility of Results; Sensitivity and Specificity; Solvents; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry; Water