ACE applied to the quantitative characterization of benzo-18-crown-6-ether binding with alkali metal ions in a methanol-water solvent system.
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.
Ehala
Sille
S
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10Prague 6, Czech Republic.
Makrlík
Emanuel
E
Toman
Petr
P
Kasicka
Václav
V
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*
D001555:Benzene Derivatives; D043844:Crown Ethers; D008672:Metals, Alkali; D014867:Water; D000432:Methanol