A Semi-Empirical Spectrophotometric (SESp) Method for the Indirect Determination of the Ratio of Cationic Micellar Binding Constants of Counterions X- and Br- (K-X/K-Br)

作者：Khan Mohammad Niyaz^*; Yusof Nor Saadah Mohd; Razak Norazizah Abdul

来源：Journal of Oleo Science, 2013, 62(9): 695-708.

DOI：10.5650/jos.62.695

• Ion exchange constants
• Spectrophotometric determination
• Counterions
• Cationic interfaces
• Quantified counterion-affinity to ionic interfaces

The semi-empirical spectrophotometric (SESp) method, for the indirect determination of ion exchange constants (K-X(Br)) of ion exchange processes occurring between counterions (X- and Br-) at the cationic micellar surface, is described in this article. The method uses an anionic spectrophotometric probe molecule, N-(2-methoxyphenyl)phthalamate ion (1(-)), which measures the effects of varying concentrations of inert inorganic or organic salt (NavX, v = 1, 2) on absorbance, (A(ob)) at 310 nm, of samples containing constant concentrations of 1(-), NaOH and cationic micelles. The observed data fit satisfactorily to an empirical equation which gives the values of two empirical constants. These empirical constants lead to the determination of K-X(Br) (= K-X/K-Br with K-X and K-Br representing cationic micellar binding constants of counterions X and Br-). This method gives values of K-X(Br) for both moderately hydrophobic and hydrophilic X-. The values of K-X(Br), obtained by using this method, are comparable with the corresponding values of K-X(Br), obtained by the use of semi-empirical kinetic (SEK) method, for different moderately hydrophobic X. The values of K-X(Br) for X = Cl- and 2,6-Cl2C6H3CO2-, obtained by the use of SESp and SEK methods, are similar to those obtained by the use of other different conventional methods.

• 出版日期2013-9