Resolution assessment and performance of several organic modifiers in hybrid micellar liquid chromatography

The performance of four criteria that measure the elementary resolution (modified selectivity, modified RS, peak purity, and orthogonal valley-to-peak ratio) was critically assessed using as global resolution function, the product of elementary measurements. The peak purities and valley-to-peak criteria yielded the best description of the overall separation according to the shape of the resolution surfaces compared to the peak arrangements in the chromatograms, the capability of defining unambiguously the composition regions of complete resolution, and the resolution achieved in the predicted optimums. Peak purities were used to compare the effect of five organic modifiers (1-propanol, 1-butanol, 1-pentanol, acetonitrile and tetrahydrofuran) on the separation quality of micellar mobile phases of sodium dodecyl sulphate (SDS). Acetonitrile, a common solvent in reversed should read reversed-phase liquid chromatography but scarcely used in micellar liquid chromatography, allowed the most satisfactory resolution in an extensive composition region with very small overlapping and sufficiently low retention times. The enhanced resolution was produced by the improved selectivity, and larger efficiencies and asymmetries of the chromatographic peaks.