The effect of co‐surfactant‐modified micelles on chiral separations in EKC

Abstract

The use of chiral pseudostationary phases in EKC provides high efficiencies and excellent resolution for enantiomeric separations. The chiral pseudostationary phases of interest in this study are alcohol-modified ("swollen") micelles, in which a co-surfactant (medium chain-length alcohol) is added with the surfactant. In this study, the chiral surfactant, dodecoxycarbonylvaline (DDCV), along with the co-surfactant, 2-hexanol, has been prepared as swollen micelle in order to investigate the chiral separation of enantiomeric pairs. Three sets of experiments were investigated in which swollen micelle systems contained: chiral surfactant and racemic co-surfactant; chiral surfactant and chiral co-surfactant; and phase ratio increases, in which both chiral surfactant and chiral co-surfactant were employed. In the first two sets of experiments, co-surfactant concentration was held constant and the surfactant concentration was increased. In the third set of experiments, both surfactant and chiral surfactant concentrations were increased proportionally. The chromatographic figures of merit for each enantiomeric pair were investigated and compared with various chiral aggregate systems. In swollen micelle compositions using constant racemic 2-hexanol concentration, when DDCV concentration increased, enantioselectivity and resolution increased; whereas, efficiency remained constant for most of the test compounds. Compositions using constant S-2-hexanol concentration reached a maximum in all chromatographic figures of merit when DDCV concentration was increased from 2 to 3%. An increase in both surfactant and co-surfactant concentrations led to noisy baselines and chiral aggregates that were generally unstable in solution.

Separation of palonosetron stereoisomers by electrokinetic chromatography using sodium cholate as chiral selector: Comparison of separation modes and elucidation of migration orders

“…). Compared with the wide use of other surfactant‐based EKC modes, the use of cosurfactant‐modified MEKC in chiral separation is very few . The influence of cosurfactant butanol on the separation (Fig.…”

Advances in the enantioseparation of β‐blocker drugs by capillary electromigration techniques

“…Kojtari et al [116] developed a chiral MEKC method for the separation of atenolol and MT enantiomers using alcohol-modified micelles, as the chiral selector. Swollen micelles were prepared adding a chiral co-surfactant (2-hexanol) to the chiral surfactant dodecoxycarbonylvaline (DDCV).…”

MEKC as a powerful growing analytical technique

“…N ‐alkanoyl‐ L ‐amino acids, N ‐dodecoxycarbonyl amino acids, alkylglucoside chiral surfactants, tartaric acid‐based surfactants, and steroidal glucoside surfactants have been used as synthetic surfactants for MEKC separation 97. Dodecoxycarbonylvaline has also been used successfully as a chiral surfactant for MEKC 98–102. Furthermore, glucopyranoside monophosphate and monosulfate anionic surfactants have been reported in MEKC for the separation of enantiomers 103, 104.…”