Plug-based online dilution strategy for achieving 11.6-fold sensitivity enhancement in UPLC-MS/MS analysis of 38...

In this study, an online ultrasensitive method was established for analyzing 38 veterinary drugs in beef by integrating ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) with a modified QuEChERS method through a fractionized sampling and stacking (FSS) interface. Large volumes of purified solution were fractionized, stacked, separated, and analyzed by the established FSS-UPLC-MS/MS system without significantly prolonging analysis time and causing overload problems. For all drugs, good linearities with R²≥0.9907 were observed as well as low limits of detection (LODs, 0.008∼0.5 μg·kg^-1) and quantitation (LOQs, 0.02∼1.8 μg·kg^-1). At three spiked levels (2, 50, and 100 μg·kg^-1), acceptable recoveries ranged from 64.9 % to 114.2 % with all RSD ≤14.0 %. Satisfactory enrichment folds (11.6 ± 2.2) were achieved without observing significant matrix effects (MEs≤±17.8 %). The fine hyphenation and good applicability of the method makes it a promising and powerful analytical tool in ultrasensitive analysis of multi-residue veterinary drugs at trace levels.