Rapid Analysis of Residues of 186 Pesticides in Hawk Tea Using Modified QuEChERS Coupled with Gas Chromatography Tandem Mass Spectrometry.

In this work, the QuEChERS method was modified and evaluated for the determination of 186 pesticides from caffeine-free and fatty hawk tea prior to their gas chromatography tandem mass spectrometry analysis for the first time. The results showed that the combination of MgSO4 + PSA + MWCNTs plus EMR-Lipid provided the lowest matrix effect and best recovery; 117 of 186 pesticides manifested weak matrix effects. Thus, for accurate quantification, it is necessary to use matrix-matched calibration curves to compensate for the matrix effect. At the spiked level of 0.1 mg/kg, the average recoveries of 184 pesticides were in the range of 70-120% and the RSDs were 0.3-14.4% by the modified method. Good linearity was shown for 186 analytes at concentration of 0.01 mg/L~0.4 mg/L, and the correlation coefficients exceeded 0.99 for 182 pesticides. The detection limits of 186 pesticides by the modified QuEChERS method were 0.001-0.02 mg/kg, and the limits of quantification (LOQ) were 0.005 mg/kg~0.05 mg/kg. The necessity of solvent exchange is also explained in this work. The successful application of the modified QuEChERS in real samples proved that this method could be one of the routine options for analysis of herbal tea.

Determination of 52 hidden chemical pesticides in biopesticide products by GC-MS/MS and LC-MS/MS.

Addition of chemical pesticides in biopesticides are expected to be common, due to effect of pest control during plant protection. These hidden chemical pesticides may cause various food safety problems if consumed. The purpose of our study was to develop a method to determine 52 hidden chemical pesticides in three formulation biopesticide products. Optimizations of different parameters, such as the instrument analysis condition for target, the extraction, and the composition of clean-up materials were carried out. The developed method used acetonitrile as an extraction solvent for all biopesticide formulations. The composition of adsorbents was based on QuEChERS, called QuSEL which was a needle filter head, containing PSA, GCB, and MgSO4. Fifty-two chemical pesticides residues were then analyzed by GC-MS/MS and LC-MS/MS. The present results showed good linearity by correlation coefficients of more than 0.99 for all analyses. The LOQ ranged from 5.0 to 20.0 µg kg-1. Recoveries of 32 chemical pesticides ranged from 71.9% to 118.4% at the spiked level of 10, 50, and 100 µg kg-1, and 20 chemical pesticides ranged from 75.3% to 119.8% at the spiked level of 5, 25, and 50 µg kg-1. The developed method was applied for biopesticide products, and 9 samples were positive in 20 samples.