Determination of cis and trans isomers of tramadol hydrochloride by capillary zone electrophoresis.

Cis and trans isomers of tramadol hydrochloride were separated by capillary zone electrophoresis (CZE) in a fused-silica capillary with 40 mmol/L of borate as a carrier. The sample concentration-peak area plots were straight lines in the range 10-250 micrograms/mL for both isomers. Based on the electropherogram, the relationship between the structure of the two isomers and the elution order has been discussed. It is considered that the trans isomer has larger hydrodynamic radius than the cis isomer and lower electric charge density. The elution order can be predicted only according to the direction of electrophoresis and electroendo-osmotic flow. The technique was successfully applied to the industrial production and the research for utilization of industrial waste material.