title: Enantiomeric separation of clenbuterol by transient isotachophoresis-capillary zone electrophoresis-UV detection new optimization technique for transient isotachophoresis.
abstract: A method for the in-line preconcentration and enantioseparation of clenbuterol by transient isotachophoresis-capillary zone electrophoresis-UV absorbance detection (transient ITP-CZE-UV) has been developed. It implies the use of dimethyl-beta-cyclodextrin as chiral selector and the application of a hydrodynamic counterflow during the ITP step. ITP is used to focus the sample constituents prior to CE whereas a counterpressure counterbalances the electrophoretic migration of the compounds. The sample is then focused and kept stationary in the proximity of the capillary inlet before CZE separation, leading to an extended-volume ITP-CZE system. A new strategy for the fast optimization of the counterpressure has been developed which implies the measurement of the hydrodynamic and electrophoretic velocities of the analyte during ITP. The in-line preconcentration and enantioseparation of clenbuterol selected as model compound was optimized using this method. Salbutamol was chosen as internal reference in order to check the reproducibility of the method. A 173-nl volume of aqueous ample solution was injected which implies an improvement of the injection volume of about 16 and a resolution of 4.8 was obtained for the clenbuterol enantiomers. A concentration detection limit of 10(-6) mol/l was readily achieved for clenbuterol and salbutamol using only 3 min ITP preconcentration in in-line counterflow transient ITP-CZE-UV. Thanks to its fast optimization, the method is applicable to any enantioseparation by means of only five very short preliminary measurements.
authors.affiliation: Department of Analytical Pharmaceutical Chemistry, Institute of Pharmacy, University of Liege, Belgium.
authors.forename: B
authors.initials: B
authors.lastname: Toussaint
authors.forename: P H
authors.initials: PH
authors.lastname: Hubert
authors.forename: U R
authors.initials: UR
authors.lastname: Tjaden
authors.forename: J
authors.initials: J
authors.lastname: van der Greef
authors.forename: J
authors.initials: J
authors.lastname: Crommen
mesh_terms: D002976:Clenbuterol / Q000032:analysis*; D004586:Electrophoresis / Q000379:methods*; D019075:Electrophoresis, Capillary / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
chemical_list: D002976:Clenbuterol