Analytical & Bioanalytical Electrochemistry
Volume:14 Issue: 12, Dec 2022

Copper(II) and lead(II) are hazardous ions in environmental samples. Determining these ions from the samples is an important issue in analytical chemistry. Currently, various methods with analytical reagents are used in the determination of Cu(II) and Pb(II) ions, however, these methods and analytical reagents are expensive, hazardous, time-consuming, and non-recyclable. In this research, it is recommended new analytical reagent named 5-(4-aminophenyl)-1,3,4-oxadiazole-2-thiol in the determination of copper(II) and lead(II) by the amperometric titration method. It is found that this analytical reagent effectively determines the Cu(II) and Pb(II) ions from environmental samples by amperometric titration, which is time-saving and low-cost. This reagent is also recyclable. It was found: (i) the detection limit for lead(II) and copper(II) ions were 2.08 and 3 ppm, respectively; (ii) the complex of 5-(4-aminophenyl)-1,3,4-oxadiazole-2-thiol with lead(II) and copper(II) ions have a sharp angle at 0.5 V and 0.75 V, respectively, indicating that these ions are determined at one solution with this reagent; (iii) it was found that the half-wave potential of 5-(4-aminophenyl)-1,3,4-oxadiazole-2-thiol was 0.55 V, confirming that the reagent is a reducing agent. The selectivity of this reagent is very high. In the future, this reagent should be widely used in the analytical determination of Cu(II) and Pb(II) ions.

An electroanalytical technique was advanced for the detection of uric acid (URI) relying on its oxidation behaviour. Using cyclic voltammetry (CV) techniques, the electrochemical performance and detection of URI were easily accomplished on poly (Blue HEGN) modified glassy carbon electrode (Po-BHEGN/GCE). The role of pH on anodic peak current and potential was examined. Phosphate buffer of 7.4 pH was opted for subsequent data analysis. Sweep rate studies were carried out and showed that electrode reaction was a diffusion-controlled process. A linear calibration curve was established in the URI concentration levels from 10-70 µM. The LOD and LOQ were estimated to be 0.94 and 2.91 µM, respectively. A simultaneous study of URI and dopamine (DA) revealed that well-separated peak at Po-BHEGN/GCE compare to GCE. To sum up, a straightforward and inexpensive sensor Po-BHEGN/GCE is built for the sensitive and focused detection of URI in samples.

A new method based on a carbon paste electrode, modified with ErO2/MnO2 nanocomposite was introduced for melatonin determination. The differential Pulse Voltammetry (DPV) method was found to be a suitable analytical technique to acquire an enhanced electro-oxidation signal and thus it was chosen as the signal recording method. The nanocomposite was characterized using Scanning electron microscopy and X-ray diffraction analysis method. The electrocatalytic activity of the carbon paste electrode modified with ErO2/MnO2-CPE toward melatonin electro-oxidation was substantiated utilizing DPV and electrochemical impedance spectroscopy ((EIS). The EIS technique gave a clear indication for the intensification the of charge transfer rate by the nanocomposite described. Different parameters, affecting the electrode efficiency were investigated and optimized. Using DPV and ErO2/MnO2-CPE, a linear dynamic range of 4.0×10-8-2.0×10-5 mol L-1 as well as a detection limit of 6.0×10-9 mol L-1 was obtained for melatonin measurement. The relative standard deviation percentage (RSD%) of four repeated measurements was found to be about 4.08%. The developed method was used for the estimation of melatonin amount in urine samples which led to satisfactory results.

4-methylcoumarin-7-yloxy-N-4-nitrophenyl acetamide and 4-methylcoumarin-7-yloxy-N-phenyl acetamide were used as effective ionophores for preparation of chromium (III) and copper (II) selective liquid membrane electrodes, respectively. Optimization of the composition of the membranes and the conditions of the analysis was performed, and under the optimized conditions the chromium (III) liquid membrane electrode has a detections limit of 1.0×10-10 with response time 4-6 s and the concentration range 1.0×10-4 to 1.0×10-10 M chromium (III) with a Nernstian slope of 20.25±0.4 mV/decade over the pH range of 4.0–7.5 and copper (II) liquid membrane electrode has a detection limit of 3.0×10-5 with response time about 5 s and the concentration range 1.0×10-1 to 3.0×10-5 M copper (II) with a Nernstian slope of 31.08±0.5 mV/decade over the pH range of 4.5–8. The chromium (III) and copper (II) selective electrodes were stable for about 8 and 5 weeks, respectively. They exhibit good selectivity for two ions. They were successfully applied for the direct determination of chromium (III) and copper (II) in wastewater and as indicator electrodes for potentiometric titration of copper ions and chromium ions with EDTA.

Morphine is a non-synthetic narcotic that derived from opium; it is used for the treatment of pain and it is toxic during overdose or when abused. In comparison to conventional analytical techniques, like HPLC, electroanalytical methods have advantages like simplicity, ease of operation, and miniaturization. Today, electroanalytical sensors are used in agriculture, food, oil, and biomedical applications. In addition to the versatility of reporting signals, such as voltages, currents, power outputs, or electrochemical impedances, electrochemical sensing has low theoretical detection limits due to differences between Faradaic and non-Faradaic currents. In this review, different electrochemical sensing modification-based techniques for determining the morphine content of samples have been investigated. Furthermore, we present the performance of reported electrochemical sensors toward morphine detection, including their detection range (LDR), detection limit (LOD), and modification of electrodes. It is our belief that the information in this manuscript can serve as a platform for future research on developing sensitive electrodes for morphine and other drugs.

Given the importance of developing cost and time saving tools, techniques and procedures for analyzing of lanthanide ions in various media, development and use of ion selective sensors for these ions is important. In this light, studying the various ion selective electrodes developed for a specific target species can create insight about the factors creating selectivity in these devices. Therefore, a review is made on the ion selective sensors prepared for lutetium over the past years. The authors have tried to provide detailed information on the composition and function of each sensor to provide better understanding for further research on the construction, as well as, the mechanism of action of these devices.