Polarity parameters of the Symmetry C18 and Chromolith Performance RP-18 monolithic chromatographic columns

A set of 12 compounds of different chemical nature has been established to characterise RPLC columns on the basis of a polarity retention model previously developed: log ⁡ k = ( log ⁡ k ) 0 + p ( P m N − P s N ) . This model allows the calculation of the retention factor (k) of any non-ionized compound using one parameter which describes the polarity of the solute (p), another one for the polarity of the mobile phase ( P m N ) and two more parameters for the characterisation of the stationary phase ((log k)0 and P s N ). The selected set of compounds allows the determination of (log k)0 and P s N of stationary phases and it has been used to characterise two commercial columns (Symmetry C18 from Waters and Chromolith Performance RP-18 monolithic from Merck). Column parameters, together with those of the mobile phase permit successful transfer of retention data between chromatographic systems. Prediction of retention of a variety of non-ionized analytes has been also successfully achieved using the column descriptors and p values of solutes from a previously established p data base.