Determination of codeine, 6-methoxycodeine and thebaine using capillary electrophoresis with tris(2,2′-bipyridyl)ruthenium(II) chemiluminescence detection

A simple and robust capillary electrophoresis chemiluminescence detection system for the determination of codeine, 6-methoxycodeine and thebaine is described, based upon the reaction of these analytes with chemically generated tris(2,2′-bipyridyl)ruthenium(III) prepared in sulfuric acid (0.05 M). The reagent solution was contained in a glass detection cell which also held both the capillary and the cathode. The resultant chemiluminescence was monitored directly using a photomultiplier tube mounted flush against the base of the detection cell. The methodology, which incorporated a field amplification sample introduction procedure, realised detection limits (3σ baseline noise) of 5 × 10-8 M for both codeine and 6-methoxycodeine and 1 × 10-7 M for thebaine. The relative standard deviations of the migration times and the peak areas for the three analytes ranged from 2.2 up to 2.5% and 1.9 up to 4.6%, respectively.