Simultaneous determination of fenobucarb, tetramethylthiuram disulfide and quinalphos pesticide residues in vegetables by UPLC-MS/MS
Abstract
A reversed-phase LC-MS-MS method was developed for simultaneous determination of Fenobucarb (FCB), Tetramethylthiuram disulfide (THI) and Quinalphos (QNP) in vegetables. The procedure was optimizedas: Column - UPLC Kinetex Phenyl - Hexyl (50 mm x 2.1 mm x 1.7 µm), Mobile phase - MeOH: formic acid 0.1 %, in gradient mode; Flow rate - 0.2 ml/min, Injection volume - 10μl. Electrospray ionization source was operated in positive mode and multi reaction monitoring (MRM) mode with the transition of m/z 208.21 " 94.95, m/z 240.99 " 88.06, m/z 299.19 "147.10 and m/z 327.20 " 76.99 for quantification of FCB, THI, and QNP and TPP (IS), respectively. By validation by the AOAC guideline, this method proved high specificity, sensitivity, and reliable, well meeting the requirements for wide linearity range (1 - 200ppb), high correlation coefficient (R2 > 0.9984), very good accuracy (recovery of 87.0 – 102.5 %), intra-day precision (RSD < 3.6 %), typical LOD, LOQ values of 0.01 - 0.13 ppb and 0.05 - 0.42 ppb for all the target pesticides. For practical application tests, 60 real vegetable samples were analyzed and 13.3 % were revealed to contain the investigated pesticide residues. Particularly, M-25 and M-36 samples found Quinalphos and Tetramethylthiuram disulfide in high levels (15.6 ppb and 12.7 ppb, respectively), much above the Vietnam Ministry of Health s MRLs.
