Zn(Ⅱ)-胆红素配合物的极谱研究

POLAROGRApHY STUDIES ON THE COMPLEX BETWEEN Zn(Ⅱ)AND BILIRUBIN

在pH=9的NH_3—NH_4Cl缓冲溶液中,Zn(Ⅱ)的还原电位为—1.27V.加入等摩尔的胆红素后,Zn(Ⅱ)的电位变为—1.23V.此现象说明,加入胆红素后,Zn(Ⅱ)在电极上还原的反应机理有所改变。紫外吸收曲线也证明Zn(Ⅱ)和胆红素间形成了配合物。用等摩尔系列法测定其组成,用极谱法测定其配位数及累积稳定常数,测得配合物组成为1∶1,配位数P为2,累积稳定常数为2.59×10^(11)。本工作还测试了Zn(Ⅱ)—胆红素配合物极谱波的性质,实验表明该波具有吸附性质。循环伏安曲线在阴极支及阳极支均有波,说明配合物的极谱波为可逆波。

The reduction potential of Zn(Ⅱ)is—1.27 V in NH_3-NH_1Cl buffer solu- tion(pH=9).When bilirubin is added,the potential is changed to—1.23 V.This phenomenon shows that the reactive mechanism of Zn(Ⅲ)reduced at the dropping mercury electrode is some-what changed.And the ultraviolet absorption curves prove that the complex is formed between Zn(Ⅱ)and Bilirubin.The component proportion of the complex is measured by isomole-series method.It is Zn(Ⅱ):BR=1:1.The coordination number(p)of the complex is 2 and its cu-mulative stabilizing constant(β_n)is 2.59×10~11,both determined by polarographic analysis.Experiments have also been conducted to determine the properties of the polarographic waves of thecomplex,and findings show the saves have adsorbability.From the cycle voltammetry curve it can been seen that the waves of the complex are present both at the cathode section and the anode section of the polarization curve,and this shows the polarographic waves of the complex are reversible ones.