Determination of 19 Organophosphorus Pesticide Residues in Green Tea by Magnetic Solid Phase Extraction Combined with Ultra High Performance Liquid Chromatography Tandem Mass Spectrometry

Magnetic graphene (Fe₃O₄@G) was synthesized as a magnetic solid phase extractor for the extraction and enrichment of organophosphorus pesticides in green tea by chemical coprecipitation method. Based on this, ultra high performance liquid chromatography tandem mass spectrometry method was developed for the determination of 19 organophosphorus pesticide residues in green tea. 40 mg adsorbent and 4 g sodium chloride were used in this experiment with the pH of sample solution at 7 for 20 min extraction time, 3.0 mL acetone desorption. The result showed that the prepared Fe₃O₄@G material had good stability and reusability with the linear correlation coefficients greater than 0.999 in the range of 5～500 μg/L. The limits of detection (LOD) and the limits of quantitation (LOQ) were 5.0～6.0 μg/kg and 15.0～20.0 μg/kg, respectively. The recoveries were between 61.2% and 94.9% with the relative standard deviations (RSD, n=6) in the range of 2.6%～10.2% when the samples were labeled at 20.0, 40.0 and 200.0 μg/kg. This method was safe and economy with a wide application range, easier control of pretreatment, less amount of organic solvent and reusable materials, which has a good application prospect in the enrichment and separation of pesticides in tea by the magnetic dispersion solid phase extraction technology.