二塩基酸色素との会合体のサーモクロミズムを利用したキニーネの抽出吸光光度定量

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タイトル別名
  • Extraction-spectrophotometric determination of quinine using thermochromism of its diprotic acid dye complexes.
  • 2エンキサン シキソ ト ノ カイゴウタイ ノ サーモクロミズム オ リヨウシ

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Quinine cation (H·Q+) was extracted into organic solvents with diprotic acid dyes, such as bromophenol blue (BPB) and bromocresol green (BCG), to form a 2:1 ion-associate, (H·Q+)2·BPB2- or (H·Q+)2·BCG2-. These ion-associates exhibited characteristics of charge transfer complexes and showed reversible thermochromism. The ratio of decrease of absorbance to temperature change (ΔA/Δt) was in propotion to the quinine concentration in aqueous phase (ΔA=A20°C-A45°C, Δt=45°C-20°C), and a good linearity was obtained within a wide concentration range of quinine 0.43.0×10-5 M. BPB-quinine associate extracted into chloroform at pH 6.5 had an absorptionmaximum at 590 nm. Maximum absorbance wavelength of BCG-quinine associate at pH 7.2 was at 550 nm in 1, 2-dichloroethane and the calibration graph was linear throughout the concentration range of 1.05.0×10-5 M quinine. Procaine, ephedrine, eserine, papaverine, triethanolamine, and tetraethylammonium did not interfere with the quinine assay in 510 fold ratio. Neither diphenhydramine, chlorpheniramine, and dibucaine in 0.51.0 fold molar excess over 1.2×10-5 M quinine had influences. Consequently, this method was proved to be selective for quinine determination compared with other spectrophotometric methods. In addition, the absorbance of ion-associates increased with a decrease in temperature; that is, the absorbance at 10°C was 24% larger than that at 20°C. The increase in absorbance with cooling seemed to be due to the enhanced ion-association in the organic phase. This method can be applied to selective determination of quinine in tablets. Furthermore, sensitivity of the method can be increased by lowering temperature of ion-associates.

収録刊行物

  • 分析化学

    分析化学 34 (11), 695-700, 1985

    公益社団法人 日本分析化学会

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