Prediction of the chromatographic behaviour for a series of diuretic compounds

The proportion of organic modifier and the pH of the acetonitrile-water mixtures used as mobile phases were optimized in order to separate a group of diuretic compounds covering a wide range of physyco-chemical properties. The Linear Solvation Energy Relationship (LSER) formalism based either on the multiparameter pi*, beta and alpha scales or the single solvent polarity parameter E-T(N), have been used to predict their chromatographic behaviour as a function of the percentage of acetonitrile in the eluent. Moreover, correlation established between retention and pH of the aqueous-organic mobile phases have been used to predict the chromatographic behaviour of the diuretic compounds studied as a function of the eluent pH. Linear correlation between the chromatographic retention and the E-T(N) polarity parameter of mobile phases containing different percentages of organic modifier has been obtained. Based on the knowledge of the acid-base dissociation constant the relation between retention and mobile phase pH has also been linearized. These relationships allowed an important reduction of the experimental retention data needed for developing a given separation and a great improvement in chromatographic optimization schemes.