Determination of extraction constant,true partition coefficient and formation constant of ion-pair complexes of quaternary ammonium salts,tetrabutylammonium bromide and isopropamide iodide.with some organic anions by a solvent extraction technique |
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Authors: | CK Shim R Nishigaki T Iga M Hanano |
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Institution: | Faculty of Pharmaceutical Sciences. University of Tokyo. Hongo, Bunkyo-ku, Tokyo 113 Japan |
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Abstract: | A new method of determining the extraction constant (Ke, the true partition coefficient (TPC) and the formation constant (Kf) of ion-pairs, was developed by the solvent extraction technique. Ke and TPC were estimated from the reciprocals of the intercept and the slope of the regression line obtained by plotting in the following equation. where ATW] and BTW] are the total concentrations of the cationic compound A and that of the anionic compound B in the aqueous phase respectively, APC is the apparent partition coefficient of A, dA is the partition coefficient of cation A+. Kf, which is expressed by Ke/TPC, was then calculated. These constants were determined for the ion-pair extraction of tetrabutylammonium bromide and isopropamide iodide with 4 organic anions, i.e. benzoic acid, p-toluenesulfonic acid, salicylic acid and taurodeoxycholic acid. This new method might be applicable to other ion-pairs without further assumptions except that the molar ratio of the ion-pair formation be 1 : 1. |
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