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Chemistry LibreTexts

Introduction

The goal of this laboratory is to provide an application of oxidation and reduction reactions in the upper-level chemistry courses such as Analytical Chemistry. These reactions are very important in biological studies of neurotransmitters. Catecholamines are a class of neurotransmitters (1,2-dihydroxybenzenes), and their detection in the human body has been of great interest to neuroscientist. Catechol is secreted in the brain and altered levels have been associated with mental and such behavioral disorders as schizophrenia, attention deficient disorder, Alzheimer’s disease, Parkinson’s disease, eating disorders, epilepsy, amphetamine and cocaine addiction [1-6].

The presence of common interferents, such as ascorbic acid, may complicate catechol analysis. This experiment uses cyclic voltammetry to detect catechol in the presence of common interferents. Electrodes modified by the electrodeposition of the conducting poly (3-methylthiophene) film (P3MT) and the poly (2, 2-bithiophene) film (PBTP) electrode was studied as chemical sensors for catechol, which is of industrial and medicinal interest. The scope of the experiment involved optimizing the modified polymer poly (2, 2-bithiophene) electrode to detect catechol in the presence of ascorbic acid. Further studies can be expanded in this lab experiment by studying the modified surface with Scanning Electron Microscopy (SEM).

These modified poly (2,2-bithiophene) platinum electrodes are capable of decreasing the overpotential, and/or improving the reversibility of electrochemical processes for such compounds as catechol and the irreversible behavior of ascorbic acid. In addition, the development of electrochemical sensors using polymer coated electrode surfaces can improve the selectivity of such sensors for practical analysis of clinical and environmental samples. Modified electrode coatings offer the assurance of bringing higher selectivity and reduced fouling compared with the corresponding bare electrochemical sensor [7,8]. For example, Wanget al. [9] showed that a microelectrode array, each coated with a different polymer possessing a different analytical function (based on differences in size, porosity charge or polarity, etc), could be employed for simultaneous multi-species analyses. In contrast, modified electrodes based on the immobilization of redox mediators onto the electrode surface are also commonly used.

In the present work this paper will illustrate results that students have generated in an Analytical Chemistry course.