MODELING OF RETENTION BEHAVIOR OF SOLUTES IN MICELLAR LIQUID-CHROMATOGRAPHY

In micellar liquid chromatography (MLC), the resolution for a given mu lti-component mixture can be optimized by changing several variables, such as the concentrations of surfactant and organic modifier, the pH and temperature. However, this advantage can only be fully exploited w ith the development of mathematical models that describe the retention and the separation mechanisms. Several reports have appeared recently on the possibilities of accurately predicting the solute retention in MLC. Although the retention and selectivity may strongly change with varying concentrations of surfactant, organic modifier and/or pH, the observed changes are very regular, and are well described by simple mo dels. This characteristic enables a successful prediction of retention times and compensates the negative effect of the broad and tailed chr omatographic peaks obtained for some solutes when micellar eluents are used. An overview of the models proposed in the literature to describ e the retention behaviour in pure micellar eluents and micellar eluent s containing an organic modifier, at a fixed pH or at varying pH, is g iven. The equations derived permit the evaluation of the strength of m icelle-solute and stationary phase-solute interactions. The prediction of the retention based on molecular properties and the use of neural networks, together with the factors affecting the prediction capabilit y of the models (linearization of the equations, dead time, critical m icellar concentration, ionic strength and temperature) are commented o n. The strategies used for the optimization of resolution are also giv en. (C) 1997 Elsevier Science B.V.