Solute Retention in Column Liquid Chromatography. II. Optimization of Mobile-Phase Compositions

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Abstract
Retentions are reported for nine phenol solutes with a reverse-phase column packing and acidified aqueous mobile phases containing tetrahydrofuran, acetonitrile, and methanol additives. Plots of log(k'(M)) against additive volume fraction φ exhibit both positive and negative deviations from linearity. In contrast, plots of inverse capacity factor against φ are in every instance convex to the abscissa. The latter, as well as several systems comprising ionic solutes and/or solvents, are fitted exactly by a semi-empirical relation; however, only one of the fitted parameters appears to exhibit identifiable trends and then only very approximately so. It is deduced by simple inspection of the plots and without resorting to higher-component carriers, then verified experimentally, that the test mixture is completely separable with 30% methanol. Window diagrams of a, Sf, and Rs ordinates are used to identify alternative mobile phases and compositions in the instance that one of the solutes is present in large excess. The three methods of data reduction prove to be entirely equivalent since the solute capacity factors approach 10. When this is not the case, window diagrams constructed with the separation-factor parameter are said to be favored.