Determination of Residues of Nine Novel Pesticides in Plant-Derived Foods by QuEChERS Combined with Liquid Chromatography-Tandem Mass Spectrometry

A method for the simultaneous detection of the residues of nine novel pesticides in plant-derived foods was developed by quick, easy, cheap, effective, rugged, and safe (QuEChERS) pretreatment combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS). The pesticides included flutianil, ipflufenoquin, mandestrobin, pyriofenone, benzpyrimoxan, isocycloseram, pyflubumide, fluazaindolizine, tolpyralate. Samples were extracted with 1% formic acid in acetonitrile followed by salting-out and phase separation using anhydrous magnesium sulfate, sodium chloride and a mixture of sodium citrate and sodium dihydrogen citrate. The extracts were purified with a mixture of N-propyl-ethylenediamine (PSA), octadecyltrimethoxysilane (C₁₈) and graphitized carbon black (GCB). The chromatographic separation was accomplished on a T3 column (100 mm × 2.1 mm, 1.8 µm) by gradient elution using a mobile phase consisting of 5 mmol/L ammonium acetate solution (containing 0.1% formic acid) and acetonitrile. The detection was carried out in the multiple reaction monitoring (MRM) mode, and the quantification was performed using a matrix-matched standard curve. The results showed that the calibration curves for all analytes exhibited a good linear relationship in the tested concentration range (R² ≥ 0.995), the limit of quantification (LOQ) was 0.005 to 0.01 mg/kg. At three spiked levels of 0.005, 0.01 and 0.05 mg/kg, the average recoveries ranged from 73.9% to 118.1%, with relative standard deviation (RSD) ranging from 0.8% and 12.8% (n = 6). This method is rapid, accurate, sensitive, and suitable for simultaneous quantification of these novel pesticides in plant-derived foods.