Development of the System Selectivity Cube

Abstract

The goal of chromatography is to separate components of a mixture. There are a number of different systems that can be used to achieve this, and each will separate the components to varying extents according to their chemical properties. The difficulty lies in that there are thousands of different systems available. We developed a three dimensional visualization tool that allows simultaneous comparison of systems in order to efficiently select a different combination to improve selectivity and successfully separate solutes. The model relies on linear solvation energy relationships (LSERs), which quantify the interaction abilities of systems. We compare two systems to one another by performing a linear regression on the coefficients of the LSER equation. According to this regression, we classify the relationship of two systems as identical, similar, or different based on the energetics of the systems that govern retention. The comparisons are then plotted in a three dimensional cube according to the slope, intercept, and correlation coefficient (r2) value of the regression. The position of the point corresponds to the energy relationship of the two systems. When using a system that does not adequately separate the components of a mixture, the cube makes it simple to visually select another system with a different energetic relationship, and thus one which might produce a better separation. This technique is applicable to all forms of chromatography, and has been implemented with 74 MEKC systems and 370 RPLC systems successfully.