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Chemistry LibreTexts

Introduction

One of the first reactions one learns in general chemistry, inorganic chemistry, and organic chemistry are the oxidation and reduction reactions. These types of reactions are very important to biological molecules such as catecholamines. Catecholamines are a class of neurotransmitters (1,2- dihydroxybenzenes) that are involved in a wide variety of physiological processes [1-6]. These classes of neurotransmitters are secreted in the brain and altered levels have been associated with mental and behavioral disorders such as schizophrenia, attention deficient disorder, Alzheimer’s disease, Parkinson’s disease, eating disorders, epilepsy, amphetamine addiction, and cocaine addiction [4]. Voltammetric detection of catecholamines is affected by the presence of interferents such as ascorbic acid [7]. The ability to enhance catecholamine selectivity is of notable interest within electroanalytical research. Various techniques have been used previously [8-18], with modified electrodes becoming the most prevalent technique [19-22]. The rate and selectivity of an electrode can be controlled by deliberately modifying its surface chemically. The concept of electrode modification originated over three decades ago with work of several research groups [1-2, 22].

Chemical modification of the electrode surface with electroactive polymeric films, has gained wide popularity in the past due to the simplicity of altering the electrode surface [3]. Further, polymer films introduce additional active sites allowing electrochemical processes at their surfaces to be more pronounced than the electrochemical processes at unmodified surfaces. Polythiophenes stand out among the numerous research projects done on electrochemically conducting polymers. This attention has been focused on polythiophenes due to their process ability, environmental stability, thermal stability, and ease of fabrication [23]. In spite of this, during the course of developing polymeric films as chemical sensors, there have been hurdles impeding successful analysis of clinical and environmental samples. Within the developmental stages of the electrode lie the need to improve its stability and selectivity of clinical and environmental samples [3]. Vandaveer et al. have utilized redox cycling (cyclic voltgammetry) measurements of neurotransmitters in ultrasmall volumes with a self-contained microcavity device that showed improved response and sensitivity [24-25]. However, optimization needs to occur of the microcavity device to make it applicable to clinical practices to achieve the desirable detection limits of neurotransmitter (dopamine) in the presence of ascorbic acid without the complications encountered by Niwa et al. [22].

This lab experiment creates a challenging opportunity for the student. It requires the synthesis of a sonogel-carbon electrode (SGC, SG=Sonogel, C=Carbon) modified with nanostructured titanium oxide, and comparison to a bare SGC electrode (no titanium oxide on the bare sonogel carbon electrode) and a poly (3-methylthiophene) (P3MT) modified electrode. Their responses to detect catechol in the presence of common interferents were studied by cyclic voltammetry [26-27]. This experiment was designed to fit into three lab sessions where each session was four hours long. This lab was created for Project REEL, R=Research, E=Experiences, E=Enhance, and L= Learning (Research Experiences to Enhance Learning) and a pre-test and post-test were given to evaluate the students' gain in content from this lab experiment. All the figures shared in this article are student data obtained from Project REEL.