SYNTHESIS OF ION ASSOCIATION REAGENTS POSSESSING CHARACTERISTIC LIGHT ABSORBING AND ITS USE IN ION ASSOCIATION IN AQUEOUS SOLUTION

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Novel ion association reagents were synthesized and investigated as analytical reagents for absorptiometric and fluorimetric determination of cationic and anionic ions in aqueous solutions. The reagents synthesized here possess the ability to change their visible light-absorbing characteristics when they react with pairing analyte ions to form ion associates. The change in the visible light absorption is due to the blue or red shift of the absorption maxima of the ion association reagents, which is considered to be a kind of "solvatochromism phenomenon". Such solvatocromism of the ion association reagents can occur when the reagents react with their pairing ions to form ion associates and change the micro-environment of the reagents from hydrophilic to hydrophobic field. Various kinds of solvatochromic ion association reagents were newly synthesized ; they are the analogues of phenylazo anions, triphenylmethane cations, diphenylaminate ions and phenylazoanilinium ions. Ion associability of these reagents were examined by spectrophotometry ; from the results obtained the factors affecting the ion associability were summarized. The reagents developed were applied to the spectrophotometric determination of hydrophobic pairing ions in aqueous solutions, and were also applied to the titrimetric method of ionic surfactants as an end-point indicator. The method for the analysis of ion association reactions in aqueous solutions was developed by using the accurate mobility measurement method, and was applied to the analysis of ion association equilibria in aqueous solutions. On the basis of the equilibrium constants obtained, the ion associability of the reagents and the factors affecting the ion associability, as well as the hydrophobicity of ions, were summarized. Such data demonstrate the importance of the ion association reaction in aqueous media as one of the fundamental reactions and the usefulness as an analytical reagent for the determination of hydrophobic anions.