Abstract: A novel micellar electrokinetic chromatographic method with laser induced fluorescence detection after derivatization with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole(NBD-Cl) was developed for the determination of muscle relaxant drug baclofen (BAL). After optimization, baseline separation of the derivatives of BAL and gabapentin (internal standard) was obtained within 7 min in a running buffer (pH 9.75) composed of 15 mmol/L sodium borate, 20 mmol/L sodium dodecyl sulfate and 10% (v/v) acetonitrile. The separation voltage was 17.5 kV. The column temperature was 25 ℃. The samples were injected by a pressure of 3.45 kPa(0.5 psi) for 3 s. The method has a linear range of 0.025~25 mg/L for BAL with the correlation coefficient of 0.9999. The limit of detection (LOD, S/N=3) and the limit of quantification (LOQ, S/N=10) were 0.90 μg/L and 6.25 μg/L, respectively. The developed method was used for the analysis of BAL pharmaceutical preparation and urine samples spiked with BAL standard. The ranges of recovery were 101.6%~107.9% for BAL preparation and 107.0%~109.6% for urine samples. This method can be applied to the quality assessment of baclofen drug products, and provide supplementary means for the drug metabolism research of baclofen.

Key words: 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl), baclofen, micellar electrokinetic chromatography-laser induced fluorescence detection (MEKC-LIFD), capillary electrophoresis (CE), derivatization