title: ACE applied to the quantitative characterization of benzo-18-crown-6-ether binding with alkali metal ions in a methanol-water solvent system.
abstract: ACE was applied to the quantitative evaluation of noncovalent binding interactions between benzo-18-crown-6-ether (B18C6) and several alkali metal ions, Li(+), Na(+), K(+), Rb(+) and Cs(+), in a mixed binary solvent system, methanol-water (50/50 v/v). The apparent binding (stability) constants (K(b)) of B18C6-alkali metal ion complexes in the hydro-organic medium above were determined from the dependence of the effective electrophoretic mobility of B18C6 on the concentration of alkali metal ions in the BGE using a nonlinear regression analysis. Before regression analysis, the mobilities measured by ACE at ambient temperature and variable ionic strength of the BGE were corrected by a new procedure to the reference temperature, 25 degrees C, and the constant ionic strength, 10 mM. In the 50% v/v methanol-water solvent system, like in pure methanol, B18C6 formed the strongest complex with potassium ion (log K(b)=2.89+/-0.17), the weakest complex with cesium ion (log K(b)=2.04+/-0.20), and no complexation was observed between B18C6 and the lithium ion. In the mixed methanol-water solvent system, the binding constants of the complexes above were found to be about two orders lower than in methanol and about one order higher than in water.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10Prague 6, Czech Republic.
authors.forename: Sille
authors.initials: S
authors.lastname: Ehala
authors.forename: Emanuel
authors.initials: E
authors.lastname: Makrlík
authors.forename: Petr
authors.initials: P
authors.lastname: Toman
authors.forename: Václav
authors.initials: V
authors.lastname: Kasicka
mesh_terms: D000465:Algorithms; D001555:Benzene Derivatives / Q000737:chemistry*; D043844:Crown Ethers / Q000737:chemistry*; D019075:Electrophoresis, Capillary / Q000379:methods*; D007700:Kinetics; D008672:Metals, Alkali / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry*; D009994:Osmolar Concentration; D012044:Regression Analysis; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D001555:Benzene Derivatives; D043844:Crown Ethers; D008672:Metals, Alkali; D014867:Water; D000432:Methanol