A STUDY OF REVERSED-PHASE LIQUID-CHROMATOGRAPHIC CAPACITY FACTORS FOR N-ALKYLBENZAMIDES AND 5,5-DIALKYLBARBITURATES USING THE SOLVOPHOBIC THEORY AND MOLECULAR CONNECTIVITY

Reversed-phase liquid chromatography was used to establish quantitative relationships between structure and retention, and to investigate the use of the capacity factor as a relative measure of hydrophobicity for some N-alkylbenzamides and 5,5-dialkylbarbiturates.; Because the hydrophobic effect is so important to biological processes and also to the interaction of the solute and stationary phase, chromatographic retention data should have physico-chemical significance for the description of biological activity. The most desirable RPLC parameter for attempted quantitative structure-activity relationship (QSAR) correlations with biochemical data would be the capacity factor determined in pure water. This number can only be obtained directly for a relatively small number of solutes. The solvophobic theory of RPLC retention was used to predict chromatographic data which could not be measured directly.; The retention of several solutes reportedly used for determining the column void volume in RPLC was investigated. Based on the evidence presented, the injection of any detectable amount of sodium nitrate produces a good estimate of the column void volume in RPLC when buffered methanol eluents are used. In unbuffered aqueous methanol, the column void volume can be estimated by an injection of approximately 3 x 10('-6) moles or greater of sodium nitrate.; The molecular connectivity index is a topological index which quantitatively encodes structural information about a compound. Molecular connectivity indices have been calculated for the compounds reported in this study and are used to explain the effects of structure on retention.