Analysis of flonicamid and its metabolites in dried hops by liquid chromatography-tandem mass spectrometry

摘要

An analytical method was developed for the determination of the neo-nicotinoid insecticide flonicamid (N-cyanomethyl-4-trifluoromethylnicotinamide) and its metabolites N-(4-trifluoronicotinoyl) glycine (TFNG), 4-trifluoronicotinic acid TFNA), and 4-trifluoromethylnicotinamide (TFNA-AM) in dried hops. The method utilized C18 and polymeric solid phase extraction (SPE) column cleanups, liquid-liquid partitioning, and liquid chromatography (LC) with mass spectrometry (MS/MS). Method validation and concurrent recoveries from untreated dried hops ranged from 66 to 119% for all compounds over five levels of fortification (0.005, 0.02, 0.2, 2.0, and 4.0 ppm). Flonicamid-treated hop samples collected from three field sites had the following residues: flonicamid levels of 0.561-2.85 ppm, TFNA levels of 0.302-0.470 ppm, TFNA-AM levels of 0.038-0.177 ppm, and TFNG levels of 0.098-0.204 ppm. Untreated hop samples from all fields had residues < 0.005 ppm for flonicamid, TFNA, TFNA-AM, and TFNG. The limit of quantitation and limit of detection for all compounds were 0.005 and 0.0025 ppm, respectively.