Use of cyclodextrins in capillary electrophoresis: Resolution of tramadol enantiomers

Capillary;tone electrophoresis was successfully applied to the enantiomeric resolution of racemic tramadol. Both uncoated and polyacrylamide-coated ca pillaries were tested for method optimization using either negatively charg ed or native cyclodextrins (CD) added to the background electrolyte (BGE). The resolution was strongly influenced by the CD type and concentration as well as by the pH and the concentration of the BGE. Among the CDs tested, c arboxymethylated-beta-cyclodextrin allowed the baseline separation of trama dol enantiomers. After the method was optimized, it was validated in a coat ed capillary for enantiomeric analysis of tramadol enantiomers in pharmaceu tical formulation, including specificity and elution order, linearity, accu racy and precision, determination of limit of detection (LOD) and quantific ation (LOQ), enantiomeric purity linearity, freedom from interference, and stability of sample solutions. Precision at the target concentration was le ss than 2%, with an accuracy higher than 99%. Furthermore, the method was a ble to detect 0.3% and to quantify 1% of the minor enantiomer in the presen ce of the major one at the target value.