title: Hydrogen-bond effect and ion-pair association in the separation of neutral calix[4]pyrroles by nonaqueous capillary electrophoresis.
abstract: A study on the migration behavior of four neutral macrocyclic compounds calix[4]pyrroles (C4Ps) by nonaqueous capillary electrophoresis (NACE) with tetrabutylammonium halide salts as background electrolyte (BGE) is described. Systematic studies were carried out with different BGE in acetonitrile (ACN) to elucidate the involved phenomena. The effect of BGE concentration on analytes effective mobilities mu eff,i was studied. Rough values of analytes absolute mobilities mu infinity,i were obtained by extrapolation of effective mobilities to zero ionic strength of BGE. Stokes radius of C4Ps in the form of C4PF(-) and C4PCl(-) was calculated. The complex constants of C4Ps with F(-) anion and Cl(-) anion and ion-pair association constants of each C4PF(-) and C4PCl(-) with tetrabutylammonium cations was evaluated and confronted. Hydrogen bonding effect is prerequisite in the separation; meanwhile ion-pair association which is intensified by steric hindrance effect plays an important role.
authors.affiliation: Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China.
authors.forename: Huaqiao
authors.initials: H
authors.lastname: Ma
authors.forename: Mina
authors.initials: M
authors.lastname: Luo
authors.forename: Shijun
authors.initials: S
authors.lastname: Shao
authors.forename: Xia
authors.initials: X
authors.lastname: Liu
authors.forename: Shengxiang
authors.initials: S
authors.lastname: Jiang
mesh_terms: D000097:Acetonitriles / Q000737:chemistry; D000465:Algorithms; D047250:Calixarenes / Q000302:isolation & purification*; D004573:Electrolytes; D019075:Electrophoresis, Capillary; D006860:Hydrogen Bonding; D007202:Indicators and Reagents; D011166:Porphyrins / Q000302:isolation & purification*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry
chemical_list: D000097:Acetonitriles; D004573:Electrolytes; D007202:Indicators and Reagents; D011166:Porphyrins; D000644:Quaternary Ammonium Compounds; C469811:calix(4)pyrrole; D047250:Calixarenes; C009405:tetrabutylammonium