Abstract: A new approach for the determination of methylephedrine hydrochloride(ME), thebaine, codeine phosphate(CP), and acetylcodeine(AC) was established by CE-ECL with ionic liquid(1-butyl-3-methylimidazolium tetrafluoroborate, BMIMBF₄). The conditions for the CE separation, ECL detection and the effect of ionic liquid(IL) were systematically investigated. Under the optimal conditions, the four analytes were well separated within 8 min using BMIMBF₄ as additive in the electrophoretic buffer. The concentration detection limits of ME, thebaine, CP, and AC were 2.1×10^-8, 1.4×10^-7, 6.3×10^-8, and 3.6×10^-8 mol/L(S/N=3), respectively. The limits of quantitation(LOQ, S/N=10) in real human urine samples were 7.6×10^-7 mol/L for ME, 3.6 ×10^-6 mol/L for thebaine, 6.5×10^-7 mol/L for CP, and 4.6×10^-7 mol/L for AC, respectively. The recoveries of four alkaloids at different levels in human urine samples were between 90.0% and 103.5%. The developed method was successfully applied to the determination of four drug alkaloids in human urine samples.

Key words: Capillary electrophoresis, Electrochemiluminescence detection, Drug alkaloids, Ionic liquid, Urine analysis