Determination of critical micelle concentration of SDS in formamide by capillary electrophoresis

Using an organic solvent and a surfactant, the uncharged, hydrophobic p-ary lacetophenones have been separated by micellar electrokinetic chromatograph y. As an example, the effect of formamide containing sodium n-dodecyl sulfa te (SDS) on the separation has been studied. Separations of all selected un charged hydrophobic compounds were shown to be strongly dependent on the co ncentration of surfactant. It is suggested that if there is no micelle form ed in the formamide solvent, the uncharged hydrophobic compound cannot be s eparated even though in the presence of surfactant. The electro-migration o f solutes was considered zero. After micelle formation, the uncharged compo unds were partitioned between the micellar and the organic solvent phases. Neutral molecule partition in and out of micelles depends on the hydrophobi city of each analyte. Based on this suggestion the critical micelle concent rations of SDS, di-(ethylhexyl) sodium sulfosuccinate (AOT) and taurodexych olic acid sodium salt (STDC) in formamide were determined.