A Novel “Mobile Phase Braking Drift Technique” Utilized for the Enantioselective Residual Analysis of Cyflumetofen and the Investigation of Its Enantiomeric Migration during Tea Growth, Processing, and Brewing

Cyflumetofen (CYF) enantiomers were first separated by reversed-phase liquid chromatography. The enantioselectivity during tea growth, processing, and brewing was studied by a reversed-phase ultrahigh performance liquid chromatography tandem mass spectrometry (RP-UHPLC-MS/MS) method. The linearity ranges of CYF enantiomers in different matrix-matched calibration curves were from 0.0025 to 1.0 mg/L, with satisfactory correlation coefficients (R² ≥ 0.9985). The average recoveries of (+)-CYF and (−)-CYF were 76.3–116.9 and 82.9–116.9%, respectively. The limits of quantification (LOQs) for the two enantiomers were 2.5 μg/kg in fresh tea leaves and tea, and 0.25 μg/L in tea infusion. The dissipation half-life (t_1/2) of (+)-CYF and (−)-CYF during fresh tea growth was 1.04 days and 1.23 days, respectively. After processing the fresh tea leaves into green tea (black tea), the processing factors (PFs) of (+)-CYF and (−)-CYF were 0.15–0.26 (0.18–0.61) and 0.11–0.26 (0.20–0.60), respectively. The total leaching rates (TLRs) of (+)-CYF and (−)-CYF from green tea (black tea) to tea infusion were 2.7% (4.2%) and 2.1% (4.9%). The enantiomeric fractions (EFs) of CYF migration during tea growth, processing, and brewing were 0.48–0.50, 0.44–0.56, and 0.47–0.57, respectively, indicating no enantioselectivity.