Explorations of alkyl polyols as "class I" organic modifiers to adjust selectivity in micellar electrokinetic capillary chromatography

In this study, we investigated a novel series of micelle modifiers useful t o alter selectivity in micellar electrokinetic capillary chromatography (ME KC). These modifiers were alkyl polyarcohols, including l-octanol, 1,2-octa nediol, 1,2,3-octanetriol, 1,2-hexanediol, and 1,2-butanediol, which act as class I organic modifiers in that their effects are on the sodium dodecyl sulfate (SDS) micelle rather than the surrounding aqueous phase, This chara cteristic allows the alkyl polyols to effect resolution when applied at con centrations as low as 20 mM (0.25% v/v) by altering the selectivity observe d with SDS without a modifier. The effects of the alkyl polyols on the crit ical micelle concentration of SDS, electroosmotic flow, and electrophoretic mobility of the SDS micelle are presented. These modifiers had little impa ct on the migration time window at the con centrations explored. Changes in selectivity induced by the alkyl polyols for a large set of model compound s are presented. Trends indicate that solutes capable of forming hydrogen b onds tend to decrease their interactions with the micellar phase while nonh ydrogen bonding solutes increase their interactions upon addition of the mo difiers. The solvation parameter model was used to characterize the induced changes in selectivity. This model suggests that even though the modifiers are structurally similar, each produced a unique set of system constants. It was also demonstrated that the addition of alkyl polyols improved the co rrelation between the partition coefficients of SDS and water to 1-octanol and water. The usefulness of the alkyl polyols was demonstrated by examinin g their effects on the separation of 11 priority phenols.