DESCRIPTION OF THE RETENTION BEHAVIOR IN MICELLAR LIQUID-CHROMATOGRAPHY AS A FUNCTION OF PH, SURFACTANT AND MODIFIER CONCENTRATION

Micellar liquid chromatography permits the elution of solutes of diver se polarity. One of the most outstanding advantages of the technique i s its capability of predicting the retention with high accuracy, as a function of different experimental variables. The separation of a grou p of compounds is usually optimized by varying the concentrations of s urfactant and modifier in the mobile phase. The pH is, however, for ma ny solutes, a variable that should be considered in the description of their elution behaviour. A global model that takes into account, simu ltaneously, the concentrations of surfactant and modifier, and the pH as chromatographic variables, is proposed for ionizable solutes. The m ean relative errors obtained in the prediction of the retention of sev en compounds eluted with 81 mobile phases of sodium dodecyl sulphate ( SDS) and 1-propanol, using equations fitted with the experimental data measured in 9 to 12 mobile phases was, usually, lower than 6%. The ra nges of the variables considered were 0.05-0.15 M SDS, 0-0.08 (v/v) 1- propanol and pH 3-7.