Analytical & Bioanalytical Electrochemistry
Volume:14 Issue: 3, Mar 2022

Many electron transfer mechanisms of important physiological systems commonly occur as multistep electrode reactions that are initiated by a gain or loss of an electron. The product of initial electrochemical reaction might subsequently participate in chemical and/or electrochemical reaction(s), in which the final product of entire mechanism is generated. Therefore, a proper understanding of electron transfer phenomena is of outmost importance to get information about mechanism going on in the redox transformation of relevant physiological systems. In this work, we focus on theoretical voltammetric features of complex multielectron surface electrode mechanisms, in which two electron transfer steps are bridged by a reversible chemical reaction. Special attention is paid to systems with so-called “inverted potentials”, in which the second electron transfer requires less energy to occur than the first one. Square-wave voltammetry (SWV) of so-called “surface ECrevE mechanism” is explored as a valuable technique that can give relevant information about diagnostics of this mechanism. The presented model is suitable to study the activity of various enzymes and lipophilic organic compounds by exploring the “protein-film voltammetry” scenario.

In this study, the metoprolol (MTP), which is a beta blocker class molecule used in the hypertension treatment, was prepared by modifying the glassy carbon electrode (GCE) with molecular imprinting technique. Firstly, p-toluene sulfonic acid (PTSA) and aniline (AN) were coelectropolymerized in the presence of MTP as a template molecule on GCE and MTP contained poly(aniline-co-p-toluene sulfonic acid) (p(AN-co-PTSA)) film was obtained. Then, the template metoprolol molecule was desorbed from the conductive p(AN-co-PTSA) film structure on the GCE surface using hydrochloric acid. Obtained molecularly imprinted electrodes were used to determine MTP by square wave voltammetry (SWV) method. The modifed electrodes obtained showed a correlation coefficient (R²) of 0.9995 in the 40-1500 µM MTP concentration range. The limit of detection (LOD) and the limit of quantification (LOQ) of the p(AN-co-PTSA) film modifed MTP electrodes were 37.9 µM and 126.3 µM, respectively. The standard deviation of 1.33% was observed for the first three replicates with the same modified electrode. For the ten replicated electrodes, stable reproducibility was achieved between the first electrode result and the tenth electrode result. For the modifed MTP electrode, the relative standard deviation (RSD%) value was calculated to be 2.53%. As results, the molecular imprinted electrodes prepared with p(AN-co-PTSA) film have low response time, high reproducibility, good stability and high selectivity for the determination of MTP.

Green inhibitors have recently captured the attention of researchers to achieve good performance to inhibit and minimize corrosion with low environmental effects. For this reason, in this work, Almond flower extract (AFE) was used as a natural inhibitor to reduce the corrosion rate of carbon steel in an aggressive solution 1M HCl. The inhibition efficiency (IE%) of this extract was examined via different experimental methods such as Potentiodynamic polarization (PDP) and Electrochemical impedance spectroscopy (EIS) for five concentrations from 0.5 to 2.5 g/L. The outcomes denoted that the inhibitory impact increased with the rising concentration of flower extract up to 2.5 g/L and subsequently decreased with increasing concentration. PDP results reveal that (AFE) is a mixed-type corrosion inhibitor, the adsorption of this flower extract compounds followed the Langmuir isotherm, and its (IE%) of 2.5g/L (AFE) can exceed 96% at 293 K. The inhibitory impact of Almond flower extract was studied at different temperatures ranging from 293 K to 323 K. The inhibition performance of (AFE) remained virtually constant with rising immersion time, depending on the results of the EIS.

A highly sensitive voltammetric sensor for quantitative analysis of methadone in biofluids is introduced. The proposed sensor is based on screen-printed electrode (SPE) modification with overoxidized polypyrrole and gold nanoparticles composite (AuNPs/PPyox/SPE). Electrochemical measurements were carried out using square wave voltammetry (SWV). Morphological and electrochemical characterization of the proposed composite were studied using field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry. A wide linear range of 1 to 120 µmol L-1 and the limit of detection of 0.45 µmol L-1 in methadone analysis obtained by the presented sensor. The proposed sensor shows proper stability and high sensitivity in quantitative analysis of standard samples and can be successfully used for methadone determination in biological fluids.

Heavy metals are materials with many advantages. However, it is also harmful to the environment and human health. Lead and cadmium can cause many health problems, such as cancer, liver dysfunction, nervous system disorders, cardiovascular problems, and many more. Lead and cadmium can also accumulate in water, soil, and plants. Based on the problem, the development of lead and cadmium analytical methods was necessary to monitor its concentration level in the environment. One of heavy metal analysis's widest voltammetry methods is anodic stripping voltammetry (ASV). ASV involves the accumulation and stripping step to improve the analysis sensitivity toward heavy metals ions. ASV applied a three-electrode system and the working electrode played an essential role in obtaining an excellent analysis performance. Recently, bismuth-material was widely used for a working electrode in voltammetry methods, especially heavy metals analysis. Bismuth can form alloys with lead and cadmium ions during the deposition step in ASV and improve sensitivity. Bismuth also has low toxicity than mercury. Therefore, this review described the recent development of bismuth-based electrodes and their modification with other materials. We also briefly explained the ASV principle and its important parameter that needs optimization. In several previous studies, the modification of bismuth-based electrodes with various materials, such as carbon nanomaterials, conductive polymers, and metal nanoparticles, can give a synergic effect and enhancement the performance of lead and cadmium analysis.

Flutamide (4-nitro-3-trifluoromethyl-isobutylanilide) is a synthetic anti-androgenic pharmaceutic compound used in the treatment of prostate cancer. Flutamide is also on the essential drug list of WHO. Determination of flutamide levels in biological fluids or in pharmaceutical dosage is of great importance in clinical medicine. Monitoring flutamide can be done through several sensitive analytical methods such as chromatography, chemiluminescence, spectrophotometry. Since flutamide is an electroactive material, it can be targeted for electroanalysis too. Meanwhile, electrochemical methods are more attended by researchers due to their desirable properties compared with other analytical methods. Designing sensors and biosensors for electroactive drugs may be a new trend in pharmaceutical analyses. Here, the electrochemical methods reported on the determination of flutamide are reviewed. Materials and nanomaterials used in the modification of the working electrodes and the characterization of each method are considered and compared.