Design of new ion association reagents having light absorption and thermo-dependence and analysis of ion association mechanism

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1) Xanthene dyes such as eosin and tetraiodofluorescein form 1 : 2 ion associates with quaternary ammonium ions at pH 7-9 ; however, the development of color in the organic solvent is poor. When a quaternary ammonium salt is added in the etractable 1 : 2 associate formed between a xanthene dye and a cinchona-alkaloid in the neutral media, a mixed ternary ion associate (1 : 1 : 1) is formed. Its extractability is enhanced due to the more bulky association formation. The ion association caused by addition of cinchona-alkaloids is unique. Eosin and tetraiodofluorescein are useful for the determination of trace amounts of quaternary ammonium salts.2) The slow redox reaction of cysteine with iron(III) in the presence of 1,10-phen is catalyzed by copper(II), producing an iron(II)-phen complex> The color development is applied to the determination of cysteine spectrophotometrically. The limit of detection(3σ) is 5 x 10^<-7> M and RSD is 0.4%. Many other amino acids do not interfere, however, … More reducing and oxidizing substances gave strong interferences. And also, a spectrophotometric method was developed for the simultaneous analysis of ascorbic acid and cysteine by flow injection system equipped with a double flow cell, which was installed in a double-beam spectrophotometer. Copper(II) greatly accelerated the reduction reaction of iron(III) with cysteine, while with ascorbic acid was little affected by copper(II). On the basis of the difference in the rate between the two reactions, both substances can be determined.3) Stepwise titrimetric method is developed for the simultaneous determination of pharmaceutical quaternary ammonium salts and aromatic amines. The method is based on the solvent extraction of R_4N and R_3NH with an ion association reagent, tetrabromophenolphthalein ethyl ester (TBPE). When the samples containing these compounds are titrated with tetrakis(4-fluorophenyl) borate or tetraphenylborate, the color in organic phase turned to blue, red-violet and yellow and the first end point and second end point were determined, respectively. Less