ABSTRACT
I. INTRODUCTION /. 1. Use of an Optimization Strategy in Liquid Chromatography Chapter 5 showed how the presence of micelles in a Reversed-Phase Liquid Chromatographic (RPLC) system can provide a great variety of interactions (Fig. 5.1). In the micellar mobile phases, the solutes can remain outside the micelle associated with the polar head of the surfactant, can form a part of the outer palisade layer, or can penetrate into the micelle core. Also, the monomers of ionic surfactants can be adsorbed on alkyl-bonded stationary phases, mainly through hydrophobic interaction between the tail of the surfactant and the alkyl chains of the stationary phase. In this case, the charged head of the surfactant will remain in contact with the polar solution. Solutes can experience hydrophobic interactions with either nonpolar tails of the adsorbed surfactant and/or nonpolar bonded moieties of the stationary phase, and polar interactions with the ionic head of the adsorbed surfactant and free silanol groups on the stationary phase. Nonpolar solutes will only be affected by hydrophobic interactions with both micelles and stationary phase, but charged solutes will give rise to two distinct additional situations, according to the sign of their charge, which can be the same or opposite to the sign of the head of the surfactant and can, therefore, be repelled or attracted by the surfactant.
