长光程薄层光谱电化学法测定茜素红S的快速化学反应参数

DETERMINATION OF PARAMETERS OF FAST CHEMICAL REACTION OF ALIZARIN RED S BY SPECTROELECTROCHEMICAL METHOD WITH LOPTLC

本文使用长光程薄层光谱电化学方法监测茜素红S的氧化产物与茜素红S形成分子间氢键的快速化学反应.求出该化学反应的热力学平衡常数为7.94×10~5 l.mol^(-1),动力学反应速率常数为426.6L.mol^(-1)·S^(-1),并从不同角度对实验结果进行讨论。

The rate constant of very fast chemical reaction generally can be measured byelectrochemical methods, but can not by the thin layer electrochemical methodsbecause of the influence of diffussion effect. Long optical path length thin layercell (LOPTLC) with large ratio of electrode area to solution volume can be used tomonitor the fast chemical reaction in situ with high sensitivity and accuracy. Itenables the absorption spectra to be measured without the influence of diffussioneffect. In the present paper, a fast chemical reaction of Alizain Red S (ARS) with itsoxidative state has been studied. The reaction equilibrium constant (K) under dif-ferent potentials can be determined by single step potential-absorption spectra inLOPTLC. An equilibrium constant of 7. 94×10~5l·mol^(-1) for the chemical reaction hasbeen obtained from the plot of lgK vs. (E-E_1~0'). Rate constant (k) under differentpotentials can be measured by single step potential-chronoabsorptiometry. A rateconstant of 426.6 l·mol^(-1)·s^(-1) for the chemical reaction has been obtained from theplot of lgK vs. (E-E_1~0') with (E-E_1~0')=0.