Analytical Sciences

Kinetic Determination of Lanthanum(III) by the Catalytic Effect on the Oxidation of Fluorescent Safranine Dyes with Potassium Bromate

Li SHENG, Zhihui ZHAO, Biquan SU, Caihong TAO, and Wangli JING

College of Chemical and Biological Engineering, Lanzhou Jiaotong University, 88 Anning West Road, Anning, Lanzhou, Gansu, 730070, China

Two simple and sensitive kinetic-fluorometric methods have been developed for the determination of lanthanum(III): fluorescence quenching generated by the oxidation of safranine T or phenosafranine with potassium bromate in an acetate buffer solution. The rate of the oxidation reaction is significantly accelerated after adding lanthanum(III). A good linearity between the relative fluorescence intensity and lanthanum(III) is observed in the range of both 0.04 – 2.0 and 4.0 – 16 μg/mL. The detection limits have been 3.6 × 10⁻³ and 0.334 μg/mL respectively. The accuracy and reliability of the methods are further validated by recovery studies via a standard-addition method, with percentage recoveries ranging from 98 to 102%. Comparing the results of two measured reaction systems, we find that the safranine T reaction system provides high sensitivity and a wider linear range. In consequence, we have chosen the safranine T system to detect sample water, and explored the reaction mechanism.

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