Quantitative structure-retention relationship approach to prediction of linear solvation energy relationship coefficients

Linear free energy relationship as a tool for characterization of three teicoplanin-based chiral stationary phases under various mobile phase compositions

Teicoplanin, teicoplanin aglycon, and methylated teicoplanin aglycon chiral stationary phases (CSPs) have been compared on the basis of the regression coefficients calculated from the linear free energy relationship (LFER) equation. The parameters have been obtained from the measurements of a set of 34 structurally diverse solutes. Influence of mobile phase composition - variation of methanol (MeOH) content - on the participation of different interactions types in the retention mechanism has been evaluated. Retention of the various interaction forces in analytes differs with both the CSP and the mobile phase composition. Hydrophobic interactions play a major role in mobile phases for high buffer contents. The more hydrophobic the CSP, the more important are they in the retention mechanism. With increase of MeOH contents in the mobile phase the major role in the interaction mechanism is shifted to more polar forces in which basicity and dipolarity/polarizability dominate. Although the LFER model does not address chiral aspects, we have attempted to explore the importance of the individual interactions in chiral discrimination of amino acids and their N-tert-butyloxycarbonyl derivatives.

Comparative study of three teicoplanin-based chiral stationary phases using the linear free energy relationship model

Teicoplanin (T) is a macrocyclic glycopeptide that is highly effective as a chiral selector for enantiomeric separations. In this study, we used three teicoplanin-based chiral stationary phases (CSPs) - native teicoplanin, teicoplanin aglycon (TAG) and recently synthesized methylated teicoplanin aglycon (MTAG). In order to examine the importance of various interaction types in the chiral recognition mechanism the three related CSPs were evaluated and compared using a linear free energy relationship (LFER). The capacity factors of 19 widely different solutes, with known solvation parameters, were determined on each of the columns under the same mobile phase conditions used for the chiral separations. The regression coefficients obtained revealed the magnitude of the contribution of individual interaction types to the retention on the compared columns under those specific experimental conditions. Statistically derived standardized regression coefficients were used to evaluate the contribution of individual molecular interactions within one stationary phase. It has been concluded that intermolecular interactions of the hydrophobic type significantly contribute to retention on all the CSPs studied here. Other retention increasing factors are n- and pi-electron interactions and dipole-dipole or dipole-induced dipole ones, while hydrogen donating or accepting interactions are more predominant with the mobile phase than with the stationary phases. However, these types of interactions are not equally significant for all the CSPs studied.

Characterization of phosphorus-containing gas chromatographic stationary phases by linear solvation energy relationships

Linear solvation energy relationships allow the prediction of a variety of solubility interactions based on a set of descriptors found in the following equation: [equation: see text]. SP refers to an intrinsic thermodynamic property that can be found experimentally for a series of solutes. Phases containing phosphate, phosphite and phosphine functional groups were studied in this work. Coefficients obtained during this work, as well as those available for previously characterized phases, were correlated with molecular structural descriptors. When effects of non-phosphorus functional groups are estimated and subtracted out, hydrogen bond acceptor capability, a1, shows a positive trend when correlated with percent functional group. Correlation of the dipolarity/polarizability coefficient, s, with calculated atomic polarizability shows stationary phases group according to like functional groups. A similar correlation with dipole moment gives a trend of increasing dipole as s1 increases. Further quantitative structure-solubility relationship work is planned to better describe the contributions of inner shell and valence electrons to the chemical and physical properties of these compounds.