Analysis of a solute polarity parameter in reversed-phase liquid chromatography on a linear solvation relationship basis

A study was made to correlate an overall solute polarity descriptor (p) with several molecular parameters: excess molar refraction (E), dipolarity/polarizability (S), effective hydrogen-bond acidity (A) and basicity (B), and McGowan volume (V), through the linear solvation model (p = c+eE+sS+aA +bB+ uV). The achieved values of p were introduced in a retention model developed previously for reversed-phase liquid chromatography (RPLC), which describes the retention according to the polarity contributions of solute, mobile phase and stationary phase. The retention behaviour (log k) of a solute in a given chromatographic system (i.e. column/organic solvent) is appropriately summarised by p, which in addition is useful to transfer retention data between solvents and/or columns. The model was tested with several sets globally including more than 200 compounds of different nature, which were eluted in acetonitrile- and methanol-water mobile phases. Satisfactory correlations were always found. When octanol-water partition coefficients (log P-o/w) were corrected with a term considering the solute acidity, good correlations were also observed between p and log P-o/w. The study shows that the retention at any mobile phase composition may be predicted using the five solvation descriptors, once characterised the polarity of the column with a small training set. Alternatively, log P-o/w, and hydrogen-bond acidity data can be used for these predictions. (C) 2004 Elsevier B.V. All rights reserved.