Recommendations for the determination of selectivity in micellar electrokinetic chromatography

A general approach for characterizing selectivity in micellar electrokinetic chromatography based on the solvation parameter model is recommended. individual surfactants are characterized by their cohesion and capacity for polar interactions indicated as lone pair-lone pair electron attraction, dipole-type interactions, and hydrogen bond acidity and basicity. The statistical and chemical validity of the solvation parameter model requires that retention data are determined for a collection of 20-40 varied solutes with a wide range of retention factors and that clustering of values and cross-correlation among the solute descriptors are absent. Since micelles are interfacial solvents with properties that can vary with changes in their external environment (buffer composition, concentration, pH, temperature, etc.) a generic set of experimental conditions are recommended for the measurement of anionic surfactant selectivity under standard conditions. The system constants used to characterize surfactant selectivity are calculated for 12 common surfactants used in micellar electrokinetic chromatography. Of these surfactants sodium dodecyl sulfate, sodium cholate, lithium perfluorooctanesulfonate, sodium N-dodecanoyl-N-methyltaurine and tetradecyltrimethylammonium bromide are identified as providing a useful range of selectivity differences for methods development in micellar electrokinetic chromatography. (C) 1998 Elsevier Science B.V.