HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC SEPARATION OF THE IMPURITIES IN A PHARMACEUTICAL RAW-MATERIAL WITH THE AID OF COMPUTER-SIMULATION

A complex pharmaceutical raw material was characterized by means of re versed-phase gradient elution. By varying gradient steepness and mobil e-phase pH, it was possible to optimize band spacing so as to separate 16 impurities or degradation products from the drug substance. Comput er simulation was useful in interpreting these complex chromatograms a nd determining the maximum number of peaks that could be separated in this way. A marginal separation of all 17 sample components could be o btained, but the resulting method was quite pH-sensitive and therefore not very rugged. As an alternative, a rugged method was developed tha t separates the drug substance from all other sample components. The p resent study also describes how present computer simulation software f or isocratic separation can be used to predict resolution for gradient elution runs as a function of pH.