去甲肾上腺素电极过程的圆二色谱电化学研究

In situ Circular Dichroism Spectroelectrochemical Study on the Redox Process of Norepinephrine 

现场圆二色薄层光谱电化学研究去甲肾上腺素的电化学氧化还原过程 .研究表明去甲肾上腺素 ( pH =7.0磷酸缓冲溶液中 )在玻碳电极上经历了不可逆的电化学氧化 ,且遵从后行化学反应 (EC)机理 ,去甲肾上腺素醌和去甲肾上腺素红的再还原遵从简单电子转移 (E)机理 .由双对数法获得去甲肾上腺素电化学氧化的式电位为E10’=0 .2 0V ,电子转移系数和电子转移数之积为αn =0 .38,标准复相电极反应常数k10 =1 .2× 1 0 -4 cm·s-1.去甲肾上腺素醌和去甲肾上腺素红的电化学还原反应参数分别为E2 0’=0 .2 5V ,αn =0 .37,k2 0 =4.4× 1 0 -5 cm·s-1和E3 0’=- 0 .2 5V ,αn =0 .33,k3 0 =1 .1× 1 0 -4 cm·s-1.

The redox process of norepinephrine in pH=7.0 phosphate buffer solution at glassy carbon electrode was studied by circular dichroism spectroelectrochemistry with a long optical path thin layer cell. The spectroelectrochemical data were analyzed with the double logarithm method. According to the double logarithsmic plot results, the mechanism of electrochemical oxidation of norepinephrine is an irreversible process with a subsequent chemical reaction (EC) to form a norepinephrinechrome. Both of norepinephrinequinone and norepinephrinechrome are followed E mechanisms. Some kinetic parameters about the electrochemical process, i.e. the electron transfer coefficient and number of electron transfered,αn= 0.38, the formal potential,E 1 0' = 0.20 V, the standard heterogenous electron transfer rate constant, k 1 0=1.2×10 -4 cm·s -1 for the oxidation of norepinephrine,αn=0.37, E 2 0' =0.25 V and k 2 0 =4.4×10 -5 cm·s -1 for the reduction of norepinephrinequnone and αn=0.33, E 3 0' =-0.25V and k 3 0=1.1×10 -4 cm·s -1 for the reduction of norpinephrinechrome, were also estimated.