Development of electrochemical sensor based on modified electrode for the determination of estradiol and fenitrothion which have negative effects on the endocrine system

The long-term use of endocrine disrupting chemicals (EDCs) leads to the formation of certain types of cancer, disorders of the reproductive system and diseases such as obesity. Because of the high toxicity and stable structure of these chemicals, rapid and low concentration determinations are very important. In the scope of this thesis, it was aimed to develop electrochemical sensor based on modified electrode in order to realize rapid, sensitive, selective and easy determination of 17-β-estradiol and fenitrothion which are EDCs. Firstly, a nanocomposite consisting of fumed silica modified with cystamine self-assambled gold nanoparticles was synthesized. The synthesized nanocomposite was then mixed with graphene nanoribbons to obtain a homogeneous modification agent. The carbon paste electrode was modified with the prepared modification agent and a voltammetric method was proposed for 17-β-estradiol determination. With this relevant method, a very low detection limit (7,4 nM) was obtained for 17-β-estradiol. In the second part of the thesis, a nanocomposite prepared by reduction of graphene oxide on the fumed silica surface and it was used in the modification of glassy carbon electrode. The prepared modified electrode showed an electrocatalytic effect in the reduction of fenitrothion, thereby increasing the peak currents significantly. The use of prepared electrochemical sensors in real samples has been investigated. The results showed that both of the electrochemical sensor prepared in this study can be used safely in the proposed analysis. Keywords: Electrochemistry, Endocrine system disrupting chemicals, Sensor, Modified electrode.