Electrocatalytic oxidation and sensitive detection of estradiol at a carbon nanotube-modified electrode coated by nickle macrocyclic complex

Estradiol (estra-1,3,5(1 0)-triene-3, I7b-diol) is the most potent estrogen of a group of endogenous estrogen steroids produced by the ovary. Deficiency of estrogen will lead to menopause, accompanied by vascular instability, a rise in incidence of heart disease and an increasing rate of bone loss Therefore, quantitative detection of estrogen is vitally important so that an appropriate level of estrogen replacement can be administered for alleviation of menopausal symptoms or to prophylax heart disease and osteoporosis Electrochemistry offers a rapid and economical means of detection. However, passivation of electrode arising from adsorption of the oxidation product of estradiol (ie quinone) on an electrode is often encountered, leading to weak detection signals. In our work, we have immobilised carbon nanotubes, followed by a Ni(cyclam)* film on a glassy carbon electrode to minimise these problems during the voltammetric detection of estradiol Here, carbon nanotubes act as a barrier to protect the electrode from passivation and their increased surface area on the electrode will enhance the detection signal Further, Ni(cyclam) is used to catalyse the oxidation of the hydroxyl groups of estradiol The oxidation current will then be used to relate quantitatively to the amount of estradiol Furthermore, we use a two-level factorial design to identify the more significant experimental parameters affecting the detection signal of estradiol, followed by optimisation of the parameters to obtain an optimurn detection signal In this paper, evaluation of our technique in the detection of estradiol in real-life samples may also be reported. *cyclam = 1,4,8,11-tetraazacyclotetradecane