LIQUID-CHROMATOGRAPHIC SEPARATION OF ZALCITABINE AND ITS STEREOISOMERS

A liquid chromatographic method capable of separating and quantitating the stereoisomers of zalcitabine has been developed and validated. Th e separation was achieved with an Astec Cyclobond I - RSP column and a mobile phase of 0.25% triethylamine in water adjusted to a pH of 6.5 with glacial acetic acid. All enantiomers were found to exhibit a line ar response in the range of 0.1-10% in the presence of 100% zalcitabin e. Precision of analysis was found to be less than 1.5% at a level of 1% relative to zalcitabine. The limit of detection for two of the thre e enantiomeric impurities was determined to be 0.05% relative to zalci tabine. The detection limit for the third was found to be 0.1%. This m ethod was successfully applied to the analysis of reference standards and several production scale batches. All of these materials were foun d to be stereochemically pure to a level of 99.8% or better.