Electrochemically generated Ru(bpy)33+-based chemiluminescence detection in micellar electrokinetic chromatography

Abstract

In situ generated Ru(bpy)33+-based chemiluminescence (CL) detection will be shown to be compatible with micellar electrokinetic chromatography (MEKC) providing significant advantages over other Ru3+ generation protocols. The CL reagent, Ru(bpy)32+ is continuously added post-capillary to avoid precipitating the anionic surfactant used to enhance the separation of neutral analytes. Ru(bpy)33+ is then electrochemically generated in situ at the interface between the separation capillary and the working electrode, where it can react with specific analytes, for example amines and amino acids to produce chemiluminescent emission. With this scheme, the critical micelle concentration is not exceeded in the detection zone, freeing the analyte to react with the Ru(bpy)33+ CL reagent. The separation and detection of various underivatized amines will be demonstrated using this methodology. For triethylamine, 70 000 plates per meter are demonstrated with MEKC providing a limit of detection (S/N=2) of 1.5 fmol of injected mass. The experimental approach used to improve the limit of detection while maintaining high separation efficiency will be evaluated and discussed.