Graphical method for the calculation of chromatographic performance in representing the trade-off between purity and recovery

A simple engineering framework that enables the rapid representation of the performance of liquid chromatographic separations is provided in this pape r. The fractionation diagram and its associated maximum purification factor versus product yield, and contamination index versus product yield diagram s, may be derived directly from chromatographic data. The fractionation dia gram plots the relative change in the cumulative fractional mass of product eluted with the corresponding fractional total mass eluted, while the maxi mum purification factor versus yield diagram shows the degree of trade-off between the levels of purity and recovery achieved in the chromatographic s tep, The minimum contamination index versus yield plot is especially suitab le for cases where the product and impurity are expressed in different unit s and shows how the extent of contaminant removal changes relative to produ ct yield. These diagrams are more straightforward and easily interpretable compared to the basic conventional chromatograms and enable investigation o f the degree of trade-off between purity and recovery for any set of operat ing conditions to be made. The approach is demonstrated for two different c hromatographic systems. In the first, a set of simulation results from a ve rified size exclusion model is used to demonstrate the approach for product recovery. In the second, a set of experimental results for the removal of endotoxin from DNA is used. This demonstrates a problem where the product a nd impurity content are measured by different assay techniques and are expr essed in different units, and also where the quality of process information is limited by the small number of fractions collected. The studies show ho w such an approach can help to identify the optimal operating conditions, i n terms of acceptable yield and desired level of contaminant removal, and t o redefine the location of product fractions needed to achieve these specif ications. (C) 2001 Elsevier Science B.V. All rights reserved.