UIC-2007-037 – New Representation of Countercurrent and Partition Chromatograms

Counter-current chromatography (CCC) is a high resolution separation technique useful for fractionating complex mixtures, such as natural product extracts, under very mild conditions based on their relative solubility in two immiscible phases. Cross-platform comparison of CCC chromatograms is essential for the calibration, quality control, trouble shooting, and test performance of instruments, as well as rapid development of new CCC/CPC (Counter-partition chromatography) columns. This is done by using different graphical plots, which provide an idea about the performance of different instruments. Currently, CCC chromatograms are plotted using retention volume or time on the x-axis, and distribution constant (Kd) on the secondary axis. However, the Kd, which is a function of both the retention volume of an analyte and the retention fraction of the stationary phase in the column is a more appropriate and reproducible value for the x-axis. The UIC inventors have devised a new mathematical and graphical method of representing countercurrent chromatograms, called the Reciprocal symmetric (ReS) plot and Reciprocal shifted symmetry (ReSS) plots. This new method overcomes the problem of representing the complete Kd (distribution constant) scale on a single plot, and provides a way of representing the entire Kd on the “x”-axis. The present invention provides a new mathematical and graphical approach to generate CCC/CPC chromatograms by representing the distribution ratio (Kd) values of all analytes in a CCC/CPC chromatogram, i.e, Kd values of 0 to ∞ on a single “x” axis, and obtain both the reciprocal symmetry (ReS) of CCC/CPC (“ReS plot) and shifted reciprocal symmetry (ReSS) plots, as and when required. Due to improved representation of peak shape across the whole polarity range of a CCC chromatogram, the ReSS plots are superior over Kd or retention volume plots. Moreover, in retention volume chromatograms, the peak shape of compounds eluting after Kd=1 tend to be elongated and distorted, when compared with GC or HPLC chromatograms. But the ReS plots of the present invention centered on the sweet spot of optimal resolution tend to minimize peak widths and provide more aesthetically pleasing plots. Nelson Grihalde grihalde@otm.uic.edu 312-996-4129