Simultaneous determination of flonicamid and its metabolites in vegetables using QuEChERS and reverse-phase liquid chromatography-tandem mass spectrometry

This paper presents a rapid analytical method for the simultaneous determination of flonicamid and its metabolites N-(4-trifluoromethylnicotinoyl) glycine (TFNG), 4-trifluoromethylnicotinic acid (TFNA), and 4-trifluoromethylnicotinamide (TFNA-AM) in vegetables using QuEChERS by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Samples were extracted with acetonitrile. The extract was purified through QuEChERS method with primary secondary amine (PSA) and graphite carbon black (GCB). Then the extract was diluted with 0.1% formic acid in water, and analyzed by LC-MS/MS on a Waters Acquity BEH C18 column with methanol/0.1% formic acid in water as mobile phase with gradient elution. The linearity of the analytical response across the studied range of concentrations (0.20-500 μg/L) was excellent, obtaining correlation coefficients higher than 0.998. No significant matrix effects were observed. Recovery studies were carried out on spiked spinach and cucumber blank samples, at four concentration levels (0.01, 0.05, 0.50 and 2.0 mg/kg) performing six replicates at each level. Mean recoveries of 81.3-94.8% with CVs of 2.4-7.0% were obtained. The method demonstrated to be suitable for the simultaneous determination of flonicamid and its metabolites in vegetables.     

Simultaneous Determination of Flonicamid and its Metabolites in Tea by Liquid Chromatography–Tandem Mass Spectrometry

An analytical method was established to simultaneously quantify flonicamid and its metabolites 4-trifluoromethylnicotinic acid (TFNA), N-(4-trifluoromethylnicotinoyl) glycine (TFNG), and 4-trifluoromethylnicotinamide (TFNA-AM) in tea using orthogonal experimental design and liquid chromatography–tandem mass spectrometry (LC–MS/MS). Residues were extracted from the samples with acetonitrile containing 1% acetic acid and were purified with graphitized carbon black. The linearity of the method was excellent in the concentration range of 0.01–10?µg/mL, producing correlation coefficients greater than 0.996 for the target compounds. The limits of detection and quantification of all analytes in tea were 0.0013–0.013?mg/kg and 0.004–0.040?mg/kg, respectively. The average recoveries of flonicamid, TFNA, TFNG, and TFNA-AM ranged from 75.14 to 92.72%, with intra- and interday relative standard deviations of 1.07–9.75%. The proposed method was successfully applied to the terminal residue determination of flonicamid and its metabolites in dry tea processed from three field trials’ fresh samples. The determined total terminal residue concentrations of flonicamid 10?days after the last application at all three sites were below the maximum residue limit (MRL) set by the European Union (0.1?mg/kg) and the residues in all samples were lower than the MRL established by the United States Environmental Protection Agency (EPA) (8?mg/kg). This method may be used to meet the requirements for the determination of flonicamid and its metabolites that could provide guidance for establishing a MRL for flonicamid in tea in China.