Reversed-phase columns are widely used in assays based on high-performance liquid chromatography (HPLC). When such assays are repeated over time, it is often necessary to replace the column. In such cases, the selectivity of columns from different production batches may prove sufficiently variable to result in a failed separation. It is possible to compensate for differences in column selectivity by making small changes (adjustments) in separation conditions. The present paper describes an efficient procedure for choosing adjusted conditions and discusses its general applicability.

Two different stationary phases, carbon coated ZrO2 and C18 modified silica were compared. They show very different selectivity. The DryLab software was used to evaluate the different selectivities using a sample of triazine herbicides.

DryLab-Software was used to determine the optimum column temperature and mobile phase pH for the separationof mixtures of roxithromicin and related compounds.

Unusual experiments can provide surprisingly good analytical solutions. When developing chromatographic methods, analysts use in most cases a combination of experience and instinct to choose initial starting conditions. This is often followed by a period of trial-and-error optimization, until the desired method is achieved. The article illustrates, how the process of chromatographic method development can be improved using computer modelling and simulation.

A computer assisted method for the scale up of a column liquid chromatographic separation from the analytical to preparative scale is successfully proposed to make the up-scaling process easier and faster. The test sample consisting of six phenolic compounds was chromatographed on an analytical HPLC column using two different gradient runs. Based on the chromatographic data achieved from these initial analyses, elution behaviour of compounds could be simulated for alternative conditions using the DryLab program. A simulative replacement of the analytical column with a preparative scale medium pressure LC (MPLC) column allowed the determination of gradient profile to allow sufficient separation in the preparative scale. A test run carried out in suggested simulated conditions matched well with expected elution times. Furthermore, this upscaling procedure was successfully applied to a plant extract.

DryLab is used to optimize mobile phase and temperature after evaluating chromatograms of gradient elution separations performed automatically by column switching. The automated procedure was applied to more than three dozen substances (steroidal intermediates) with a time savings of more than a third.