米非司酮的吸附伏安特性

Adsorptive Voltammetric Behavior of Mifepristone

在ｐＨ ７．０ Ｂｒｉｔｔｏｎ－Ｒｏｂｉｎｓｏｎ缓冲溶液中，米非司酮（Ｍｉｆｅｐｒｉｓｔｏｎｅ，ＲＵ486）在汞电极上有２个不可逆的线性扫描还原峰，峰电位分别为-1.23Ｖ和-1.68Ｖ（vs．SCE）。本文探讨了第一峰的电化学行为。该峰具有明显的吸附性，吸附粒子为ＲＵ486分子，测得饱和吸附量为1 ．０９ Ｘ １０－１０ ｍｏｌ／Ｌ，吸附系数ｐ= １ ．１０ Ｘ １０5 ，吸引因素ｙ= １ ．６７，吸附自由能－ ２８．７６ ｋＪ／ｍｏｌ，电子转移数 ｎ= ２，转移系数 ａ= ０．５８，表面电极反应的速率常数 ｋs = ０．１６ Ｓ-1，探讨了 ＲＵ486在汞电极上的还原机理。

In a supporting electrolyte containing B-R buffer solution at pH 7.0, two irre- versible reduction-peaks of Mifepristone(RU486) was found by linear-sweep voltammetry at Hg electrode, with the potentials Epc1=-1.23 V and Epc2=-1.68 V(vs. Ag/AgCl), re- spectively. This paper studied the electrochemistry of the first one emphatically. The peak shows adsorptive characteristics. The adsorbed species is most probably neutral molecule of RU486. The saturated adsorption amount of RU486 at Hg electrode is 1.09 X 10-10 mol/cm2. The adsorption coefficient β is 1. 10 X 105, the attraction factor γ is 1. 67 and the adsorption free energy is -28. 76 kJ/mol. The number of electrons transferred per RU486 molecule n is 2 and the transfer coefficient a of the irreversible adsorptive system of RU486 is 0. 58. The rate constant of surface electrode reaction k3 is 0. 16 s-1. The mechanism of electrochemical reduction of RU486 at Hg electrode is explored.