Development of quantitative structure-activity relationships for interpretation of the migration behavior of neutral platinum(II) complexes in microemulsion electrokinetic chromatography

Metal-ligand complexes present an important group of analytes in capillary electrophoresis (CE) utilized as an analytical tool for metal ion analysis, metal speciation studies, and characterization of metal complexes of pharmaceutical or industrial importance. In the majority of CE techniques but not yet in microemulsion electrokinetic chromatography (MEEKC), the migration behavior of metal complexes has been well described using the formalism of quantitative structure-activity relationships (QSARs). To fill this gap, a number of migration models, operating with the fundamental properties of analytes as molecular descriptors, were derived and tested for platinum(II) complexes with cyclohexanediamine and its alkylsubstituted derivatives as variable ligand. It was demonstrated that the complexes under examination are consistent with respect to the experimental versus calculated values of n-octanol-water partition coefficients (log P). Meaningful two-parametric regressions between the retention factors and the analyte structural descriptors, such as log P, molecular volumes or surface areas and dipole moments, were obtained. In addition, statistically significant correlations between k′ of the platinum(II) complexes and their theoretical binding energies onto a hydrophobic surface were established. The validity of the QSAR modeling approach allowed the authors to postulate that it can be applied to the investigation of binding phenomena for neutral metal complexes to a microdroplet pseudostationary phase.