Simultaneous determination of the proinsecticide flometoquin and its bioactive metabolite in plant-derived foodstuffs by modified QuEChERS coupled with UHPLC-MS/MS.

This study aimed to established a method based on modified QuEChERS with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) for the simultaneous determination of a novel quinolone proinsecticide flometoquin and its bioactive metabolite O-deacylated-flometoquinin plant-derived foodstuffs (sweet orange, lemon, spinach, green pepper, and tea). Maximal extraction efficiency for both target analytes across all matrices was achieved using acetonitrile containing 2% formic acid, yielding satisfactory recoveries (87%-92%). The dispersive solid-phase extraction cleanup, multi-walled carbon nanotubes (MWCNTs, 10-20 nm outer diameter, 5 mg) were exclusively employed as the sorbent. This specific configuration was determined to provide maximal cleanup efficacy following a systematic evaluation against traditional sorbents (PSA and GCB), effectively removing pigments while maintaining acceptable analyte recovery. The limit of quantification (LOQ) of both two target compounds was 10 μg/kg. The mean recoveries at four spiked levels (10, 100, 1000 and 5000 μg/kg) from different matrices ranged from 79% to 109%, with all relative standard deviations (RSDs) values below 4%. Matrix effect (ME) was observed for the two target analytes across the tested matrices. Specifically, flometoquin exhibited weak MEs across all matrices, with values ranging from -10% to -2%. Conversely, O-deacylated-flometoquin showed pronounced signal suppression (from -48% to -26%) in sweet orange, lemon, and green pepper, whereas only weak effects were observed in spinach (-19%) and tea (-18%). Validation results confirm the method's suitablity for routine monitoring of flometoquin and its bioactive metabolite O-deacylated-flometoquin residues in various plant-derived agricultural products.