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A nonaqueous capillary electrophoresis (NACE) method, coupled with either UV or electrospray mass spectrometry (ESI-MS), is described for the simultaneous analysis of seven beta-blockers. The same electrolyte, namely 25 mM ammonium formate and 1 M formic acid, was used with different investigated organic solvents. In addition to frequently used organic solvents such as methanol (MeOH) and acetonitrile (MeCN), formamide and its derivatives were investigated. Formamide (FA) and N-methylformamide (NMF) present several interesting physico-chemical properties, one of them being a high dielectric constant (e). Since FA and NMF possess a high UV cutoff, beta-blockers with an absorbance above 250 nm were selected as model compounds in order to compare NACE-UV and NACE-MS performances. FA and NMF showed different selectivity compared to water, MeOH or MeCN, and also demonstrated a higher efficiency in terms of the number of theoretical plates (especially NMF). To overcome their unfavorable optical properties, hyphenation with MS detection appears as a promising technique, thanks to its benefits in terms of selectivity, sensitivity and universality. The practical compatibility of FA and NMF with ESI-MS detection in combination with a sheath liquid configuration was demonstrated. In comparison to UV detection, sensitivity was increased, while a high efficiency was maintained. In addition, the low and stable generated currents observed were evidences for the successful hyphenation with ESI-MS. Hence, FA and NMF seemed to be promising alternatives in NACE-ESI-MS, either used as pure organic solvent or as a mixture with MeOH or MeCN.

On-line combination of partial filling capillary electrophoresis and electrospray ionization mass spectrometry was demonstrated for the simultaneous enantioseparation of tramadol and its main phase I metabolites. The partial filling technique was efficient at avoiding MS contamination by the chiral selector. Different experimental factors were investigated, including the chiral selector nature and concentration, plug length as well as the separation temperature. The best enantioseparation of the investigated compounds was achieved with a coated polyvinyl alcohol capillary and a 40 mM ammonium acetate buffer, pH 4.0, adding sulfobutyl ether beta-cyclodextrin (2.5 mg/ml) as the chiral selector. The charged cyclodextrin not only allowed enantioseparation of tramadol and its metabolites, but also improved the selectivity of compounds with the same molecular mass. Finally, CE-electrospray ionisation-MS was successfully applied to the stereoselective analysis of tramadol and its main metabolites in plasma after a simple liquid-liquid extraction.