Determination of small amounts of thallium (I) by quenching of fluorescence of uranyl ions.

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  • ウラン（ＶＩ）のけい光の消光によるタリウムの微量定量
  • ウラン 6 ノ ケイコウ ノ ショウコウ ニヨル タリウム ノ ビリョウ テイ

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The quenching of uranyl fluorescence by Tl (I) was applied to the thallium determination. Lifetime and intensity of uranyl fluorescence in the absence and presence of Tl(I) were investigated in various acid media. In phosphoric acid solution, the fluorescence lifetime is the longest, and its intensity is also the strongest among the acid solutions used in the present work. In phosphoric acid as well as in sulfuric acid, this quenching action, which is caused by a collisional deactivation between excited uranyl ion and Tl (I) ion and is diffusion-controlled process, obeys the following Stern-Volmer relation:<BR>Io/I-1=τo/τ-1=KC=τokqC, <BR>where I and τ are the fluorescence intensity and lifetime, and the subscript 0 refers to the absence of Tl(I), kq, C and K being the rate constant for the collisional deactivation process, the concentration of Tl(I) and the quenching constant, respectively. Tl(I) can be determined by using the plot of τo/τ- 1 (or Io/ I-1)against C as a working curve. As its slope(K) is equal to τokq, phosphoric acid was the most appropriate media for the determination of small amounts of Tl (I). Dependence of the quenching constant on the concentration of phosphoric acid and temperature was shown in Fig. 1. In the determination of Tl (I), measurement of the lifetime was made with solutions containing 10 mM uranyl sulfate and 1M phosphoric acid at 25°C. Under these conditions, the working curve was linear in the concentration range of T1 (I) between 0.2 to 400μM. A satisfactory precision was obtained for Tl (I) in the concentration range of 0.5 to 400μM. The sensitivity of this method is comparable to a sensitive absorptiometric method. In the present method, the temperature of the specimen must be kept constant, and Ag (I), Fe (II), (I), Sn (II) and halogen ions strongly interfere the determination by the strong quenching action. The interference with Fe (II), Hg (I) and Sn (II), however, can be eliminated by oxidizing them to the higher oxidation state.

Journal

  • BUNSEKI KAGAKU

    BUNSEKI KAGAKU 24 (4), 257-261, 1975

    The Japan Society for Analytical Chemistry

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