Calculation of Abraham descriptors from experimental data from seven HPLC systems; evaluation of five different methods of calculationElectronic supplementary information (ESI) available: Tables S1 to S5. See http://www.rsc.org/suppdata/p2/b2/b206927j/

Abstract

Solvation equations have been obtained for seven high performance liquid chromatographic (HPLC) systems, generated in the reverse phase (RP) mode with fast gradient elution. A training set of 40 compounds was used for each system. The seven equations were then used to calculate Abraham descriptors for a completely separate 40-compound test set. In this way the three descriptors dipolarity/polarizability S, hydrogen bond acidity A, and hydrogen bond basicity B were obtained. Five different procedures were used to calculate the descriptors, (i) Microsoft ‘Solver’, (ii) a program that uses a set of three simultaneous equations, and which we denote as ‘TripleX’, (iii) a program similar to Solver that we denote as ‘Descfit’, (iv) a series of regression equations developed from compounds with known descriptors and (v) a series of modified regression equations. We show that RP-HPLC data for a given compound in seven systems can be used to calculate the three Abraham descriptors reliably. We compare descriptors, and errors in the method, with those obtained from water–solvent partition systems.