Recent Advantages on Mediator Based Chemically Modified Electrodes; Powerful Approach in Electroanalytical Chemistry

Background: Modified electrodes have advanced from the initial studies that were aimed at understanding electron transfer in films to applications in such areas as energy production and analytical chemistry. This review emphasizes the major classes of modified electrodes with mediators that are being explored for improving analytical methodology. Chemically modified electrodes (CMEs) have been widely used to counter the problems of poor sensitivity and selectivity faced at bare electrodes. We have briefly reviewed the organometallic and organic mediators that have been extensively employed to engineer adapted electrode surfaces for detection of different compounds. Also, the characteristics of the materials that improve the electrocatalytic activity of the modified surfaces are discussed. Objective: Improvement and promotion of pragmatic CMEs has generated a diversity of novel and probable strong detection prospects for electroanalysis. While the capability for handling the chemical nature of the electrode/solution interface accurately and creatively grows, it is predictable that different mediators-based CMEs could be developed in electrocatalytic activity and completely new applications be advanced.

Chemically Modified Electrodes in Electrochemical Drug Analysis

Electrode modification is a technique performed with different chemical and physical methods using various materials, such as polymers, nanomaterials and biological agents in order to enhance sensitivity, selectivity, stability and response of sensors. Modification provides the detection of small amounts of analyte in a complex media with very low limit of detection values. Electrochemical methods are well suited for drug analysis, and they are all-purpose techniques widely used in environmental studies, industrial fields, and pharmaceutical and biomedical analyses. In this review, chemically modified electrodes are discussed in terms of modification techniques and agents, and recent studies related to chemically modified electrodes in electrochemical drug analysis are summarized.

Voltammetry at Hexamethyl-P-Terphenyl Poly(Benzimidazolium) (HMT-PMBI)-Coated Glassy Carbon Electrodes: Charge Transport Properties and Detection of Uric and Ascorbic Acid

We describe the voltammetric behavior of an anion-exchange membrane, hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI). The anion-exchange properties of HMT-PMBI chemically modified electrodes were investigated using K4Fe(CN)6 and K2IrCl6 as redox probes. The permselectivity properties of HMT-PMBI chemically modified electrodes were ascertained using tris(2-2’)bipyridyl-ruthenium(II) chloride Ru(bpy)32+. Cyclic voltammetry and chronoamperometry were utilized to extract parameters such as the concentration of the redox mediators inside the films and the apparent diffusion coefficients. We found the concentration of K4Fe(CN)6 and K2IrCl6 redox species within HMT-PMBI-coated films to be on the order of 0.04–0.1 mol·dm−3, and values of Dapp ca. 10−10–10−9 cm2·s−1. To evaluate the possibility of using such a polymer coating in electroanalysis, HMT-PMBI-modified electrodes were utilized for the voltammetric detection of uric acid in artificial urine, Surine® and ascorbic acid in Vitamin C samples. The results showed that HMT-PMBI-coated electrodes can detect uric acid in Surine® with a limit of detection (LoD) of 7.7 µM, sensitivity of 0.14 µA·µM−1·cm−2, and linear range between 5 μM and 200 μM, whereas for Vitamin C tablets, the LoD is 41.4 µM, the sensitivity is 0.08 µA·µM−1·cm−2, and the linear range is between 25 μM and 450 μM.