Simultaneously Detection of 10 Organophosphorus Pesticides Residues in Tea by Sin-QuEChERS with UPLC-MS/MS

Based on the characteristics of tea samples, a method was established for simultaneously detection of 10 organophosphorus pesticides residues (dimethoate, omethoate, phosemet, malathion, dipterex, dichlorovos, quinalphos, demeton, methamidophos, monocrotophos). In this method, a novel pretreatment method of Sin-QuEChERS was used for extraction and purification, and ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) technology was used for detection. In view of the strong matrix effect of tea samples and the characteristics of organophosphorus pesticide decomposition with heat, a packing column filled with PSA, C18, carbon multiwalled nanotubes (CMWNTs) was applied in the Sin-QuEChERS methods. After an ordinary extraction by acetonitrile, vortex oscillation and centrifugation, the purification of chlorophyll, lutein and tea polyphenols in tea leaves was processed with a simple pressing of the Sin-QuEChERS packing column. The purified solution can be directly injected into the detector. This Sin-QuEChERS method can improve the removal effect of matrix interference by SPE, improve the purification effect of pigments, lipids and some sugar sterols, and reduce the interference of chromatogram. Compared with other extraction and purification methods, it has the advantages of simple operation, obvious purification effect on impurities, less adsorption on pesticides and accurate results, and can greatly shorten the analysis time. At the same time, because this method does not involve heating and other links, it is suitable for temperature decomposition of organophosphorus pesticides extraction and purification operation, and is able to improve the accuracy of organophosphorus pesticides detection results. In the optimized Sin-QuEChERS methods and UPLC-MS/MS detection conditions, the preprocessing time can be controlled within 10 min, so that the analysis time of a sample can be completed within the 0.5 h. The linear range of 10 organophosphorus pesticides is 1-500 μg/L. The limit of detection (LOD) is 0.08-1.38 μg/kg, and the limit of quantity (LOQ) is 0.27-4.60 μg/kg. The recoveries are 71.6%-115.0% and RSDs of different spiking levels are less than 14.5%. Compared with the traditional sample pretreatment method, the new developed method has the advantages of simple operation, time saving, good universality and high sensitivity with the premise of ensuring repeatability. The method was applied for the detection of organophosphorus pesticides in standard addition of blank tea samples and 20 kinds of tea, which proved the feasibility and importance of the method. This method provides a new way to evaluate the quality and safety of tea more quickly, simply, cheaply and accurately.