Simutanous Determination of 5 Anesthetic Residues in Fish by High Performance Liquid Chromatography-Tandem Mass Spectrometry with QuEChERS Extration

A method of high performance liquid chromatography-tandem mass spectrometry combined with QuEChERS extraction was developed for the simultaneous determination of 5 anesthetic residues, including benzocaine, lidocaine, procaine, pramocaine and tetracainein, in fish. 10 mL of acetonitrile and QuEChERS extraction reagent package (containing 4 g of MgSO₄ and 1 g of NaCl) were added to 5.000 g of sample, and the mixture was vortexed for 5 min, then centrifuged at 9 000 r·min^-1 for 4 min. 5 mL of the upper extract was added to QuEChERS purification reagent package (containing 150 mg of PSA and 150 mg of C₁₈), and the mixture was vortexed for 3 min, then centrifuged at 9 000 r·min^-1 for 4 min. A portion of the supernatant was taken and filtrated through a 0.22 μm organic filter, and 200 μL of the filtrate was mixted with 800 μL of 0.1% (φ) formic acid solution. A Thermo RP-MS column (150 mm×3 mm, 2.6 μm) was used as the stationary phase, and the mixture of acetonitrile and 0.1% formic acid solution was used as the mobile phase for gradient elution. Electrospray positive ion source and multi-reaction monitoring mode were selected for mass spectrometry analysis. Matrix effect was eliminated using matrix-matched standard solutions and external standard method was used for quantification. Linear relationships were found between peak areas and mass concentration of the 5 anesthetics in the same range of 5.0-100 μg·L^-1, and the detection limits (3S/N) were 0.05-0.3 μg·kg^-1. Values of recovery obtained by standard addition method were in the range of 71.0%-102%, and RSDs (n=6) were in the range of 1.8%-9.8%.