Cationic gemini surfactants as pseudostationary phases in micellar electrokinetic chromatography. Part I: Effect of head group |
| |
Authors: | Cevdet Akbay Yatzka Hoyos Edward Hooper Hakan Arslan Syed AA Rizvi |
| |
Institution: | 1. Department of Natural Sciences, Fayetteville State University, Fayetteville, NC 28304, USA;2. Department of Chemistry, Faculty of Pharmacy, Mersin University, Mersin, TR 33169, Turkey;3. Department of Chemistry, Emory University, Atlanta, GA 30322, USA |
| |
Abstract: | Two cationic gemini surfactants with pyrrolidinium or alkyl ammonium head groups with but-2-yne spacers, but with the same length hydrocarbon chain have been characterized with respect to their aggregation behaviors and separation power as pseudostationary phases (PSPs) for micellar electrokinetic chromatography (MEKC). They were compared with a commonly used PSP, sodium dodecylsulfate (SDS). The results suggest that the head groups of the surfactants have some effect on physicochemical properties such as critical micelle concentration (CMC), C20, γCMC, partial specific volume, methylene selectivity and mobilities of the surfactants. CMC values of G1, G2 and SDS in pure water were found to be 0.82, 0.71, and 8.08 mM, respectively; they were reduced to 0.21, 0.11, and 3.0 mM when measured in 10 mM phosphate buffer at pH 7.0. G1 (αCH2=2.74) and G2 (αCH2=2.48) provided the most and the least hydrophobic environment, respectively. According to their partial specific volumes, geminis were found to have more flexible structures as compared with sodium dodecylsulfate. The effects of the head group structure were also characterized with the linear solvation energy relationship (LSER) model, which was able to evaluate the role of solute size, polarity/polarizability, and hydrogen bonding on retention and selectivity. The cohesiveness, hydrogen bond acidic and basic character of the surfactant systems were found to have the most significant influence on selectivity and MEKC retention of the gemini surfactants. It should be noted that with their large positive coefficient a values, G1 and G2 were found to be stronger HB acceptors than anionic and most of the cationic surfactants studied in the literature. |
| |
Keywords: | C20 CMC γCMC Cationic gemini surfactants HBA HBD MEKC NHB Partial specific volume Pseudostationary phase |
本文献已被 ScienceDirect 等数据库收录! |
|