Adjusting selectivity in micellar electrokinetic capillary chromatography with 1,2-hexanediol

In this report, we introduce a new micelle modifier useful to alter selecti vity in micellar electrokinetic capillary chromatography (MECC). 1,2-Hexane diol acts as a class I organic modifier in that its effects are on the sodi um dodecyl sulfate (SDS) micellar rather than the surrounding aqueous phase . This characteristic allows 1,2-hexanediol to improve resolution when appl ied at concentrations as low as 20 mM (0.25% v/v) by altering the selectivi ty observed with SDS alone. The effects of 1,2-hexanediol on the critical m icelle concentration of SDS, electroosmotic flaw, electrophoretic mobility of the SDS micelle, and reproducibility are presented. 1,2-Hexanediol had l ittle impact on the migration time window at concentrations below 100 mM. c hanges in selectivity induced by 1,2-hexanediol for a large set of model co mpounds are presented. Analytes capable of forming hydrogen bonds tend to d ecrease their interactions with the micellar phase while nonhydrogen bondin g analytes increase their interactions. The usefulness of 1,2-hexanediol wa s demonstrated by examining its effects on the separation of dansylated ami no acids. Eighteen of twenty amino acids could be separated with a resoluti on greater than 1.6 within 1600 s using a combination of 1,2-hexanediol and isopropanol.