title: Dispersive microextraction based on "magnetic water" coupled to gas chromatography/mass spectrometry for the fast determination of organophosphorus pesticides in cold-pressed vegetable oils.
abstract: 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.
authors.affiliation: Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), Department of Chemistry, Wuhan University , Wuhan 430072, People's Republic of China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhao
authors.forename: Qian
authors.initials: Q
authors.lastname: Lu
authors.forename: Qiong-Wei
authors.initials: QW
authors.lastname: Yu
authors.forename: Yu-Qi
authors.initials: YQ
authors.lastname: Feng
mesh_terms: D053000:Analytic Sample Preparation Methods; D002681:China; D004117:Dimethoate / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry; D005506:Food Contamination; D005513:Food Inspection / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry; D059627:Liquid Phase Microextraction; D060328:Magnetic Phenomena; D008999:Monocrotophos / Q000032:analysis / Q000737:chemistry; D009943:Organophosphorus Compounds / Q000032:analysis* / Q000737:chemistry; D009946:Organothiophosphorus Compounds / Q000032:analysis / Q000737:chemistry; D010573:Pesticide Residues / Q000032:analysis* / Q000737:chemistry; D010575:Pesticides / Q000032:analysis* / Q000737:chemistry; D010938:Plant Oils / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D009943:Organophosphorus Compounds; D009946:Organothiophosphorus Compounds; D010573:Pesticide Residues; D010575:Pesticides; D010938:Plant Oils; D014867:Water; C002302:dimethoxon; D008999:Monocrotophos; C014655:methamidophos; D004117:Dimethoate