Abstract: A novel method for the determination of monoethylglycinexylidide (MEGX) （lidocaine metabolin） in serum using solid phase extraction (SPE) and capillary gas chromatography-mass spectrometry (GC-MS) was established. The serum sample was extracted with a CN-SPE column. An HP-5MS capillary column (15 m×0.25 mm×0.1 μm) was used. The initial temperature of the column was set at 100 ℃, held for 1 min, then raised to 200 ℃ at 40 ℃/min, and held at 200 ℃ for 0.5 min. The sample size was 2 μL, and the split ratio was set at 1∶1. The carrier gas was high purity helium with a flow rate of 1.0 mL/min. The monitoring ions for the determination were m/z 58 for MEGX and m/z 86 for procaine （internal standard）. The calibration curve of MEGX had good linear relationship in the range of 1.562-25 ng/mL (r=0.9981). The limit of detection was 0.5 ng/mL. The extraction recovery ranged from 80.1% to 85.7%. The method advanced the quantitative analysis of MEGX in serum by combining rapid and efficient SPE with specific and sensitive quantitation by GC-MS.

Key words: gas chromatography-mass spectrometry (GC-MS), lidocaine, metabolin, monoethylglycinexylidide, serum, solid phase extraction (SPE)