Methodology of deconvolution of total solute retention on chemically modified stationary phases to structure specific contributions of bound compounds

摘要

The total solute retention by a chemically modified stationary phase (CMSP) has been shown several times to be a potential tool for studying the binding abilities of the bound compound. In this article, we present a methodology for the deconvolution of the total retention into structure-specific contributions. Three complementary silica-based CMSPs were prepared: 1) non-modified silica, 2) silica modified by syn-bis-Troger's base (a molecular tweezer) and 3) silica modified by anti-bis-Troger's base (a non tweezer molecule). These were characterized by elemental analysis and Raman spectroscopy, and used to assemble liquid chromatography (LC) columns. The total retention factors were estimated for electron deficient nitro-and cyano-derivatives of benzene in both normal and reverse elution modes. The total retention factor was considered to be the sum of structure-specific retention factors, each related to the affinity (the binding constant) of a specific structure (the binding site), and its content in the modified silica, as defined for weak-affinity chromatography (WAC). The obtained structure-specific contributions are in line with the binding studies of ligands in solution. They reveal details of the retention mechanism, suggesting a more suitable attachment of ligands, and expose the shortcomings of evaluations based solely on the total retentions.