Analytical & Bioanalytical Electrochemistry
Volume:14 Issue: 1, Jan 2022

Mixed orthorhombic Srx doped α-Sb2O4 (x=2,4,8 and 10 wt. %) nanostructures (NS) were successfully synthesized by simple chemical precipitation method. Crystal structure, morphologies and microstructures of the as-synthesized Srx: α-Sb2O4 NS were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. XRD displayed that the NS were extensively crystalized and crystallite size increases with increase in the concentration of Sr2+ ions. SEM revealed spherical like morphologies and grain size varies between ~ 88 nm to 110 nm. Red shift in the optical absorptivity and increase in the optical band gap (Eg) displayed in UV-visible spectra as the Sr concentration increases in α-Sb2O4 NS. In Fourier transform infrared spectra (FT-IR), intensity of the characteristic peak Sb-OH gradually increases as Sr2+ dopant concentration increases in NS. Electrochemical performances of Srx: α-Sb2O4 (x =10 wt. %) NS exhibited specific capacitance of 890 F/g at a current density of 1 A/g in 6 M KOH solution. Srx: α-Sb2O4 NS showed cyclic retention of 88.95 %, long term cyclic stability up to 1000 cycles and excellent repeatability and reproducibility. Srx:α-Sb2O4 NS act as a promising electrode material for super capacitor and can be used in high energy storage device applications.

Cyclic voltammetry and differential pulse voltammetry techniques for the simultaneous analysis of ibuprofen (IBU) and paracetamol (PCT) at carbon paste electrode modified with clay (CPE-Clay) are reported. The surface characterization of the clay was realized by zero-point charge and electrochemical methods. The electrocatalytic activity of clay toward ibuprofen electro-oxidation and paracetamol redox were reported. The kinetic parameters for ibuprofen and paracetamol electro-analysis by the modified carbon paste electrode clay-CPE were calculated. Peak ibuprofen oxidation and peaks paracetamol redox were well presented onto modified electrode clay-CPE when compared with other electrodes in the literature.  Peak oxidation of the ibuprofen and peaks paracetamol redox was well presented onto modified electrode clay-CPE compared with other electrodes in the literature. The high sensitivity of the clay-CPE is measured by the DPV method showed linear variation with ibuprofen and paracetamol concentration with respectively detection limit (LOD) of 3.23×10-8 mol L-1 and 1.04×10-8 mol L-1. The applicability of the working electrode has been explored by the simultaneous electroanalysis of the ibuprofen and paracetamol in human blood samples.

Mefenamic acid (Mef) is a derivative of phenylanthranilic acid (Paa). As a drug of the NSAID group, it reduces the sensation of pain and suppresses the development of inflammation in the human body. For its determination, in substance and dosage forms (tablets, capsules, gels) different methods of analysis are used. Ionic associate (IA) compounds of Mef and Paa with rhodamine 6G were used as electroactive substances (EAS) in the manufacture of membranes of ion-selective electrodes. Investigation of the electrochemical properties of the obtained ISEs with different contents of the EAS (1-10%) shows that they give an answer to the concentration of Mef and Paa in a solution in a wide range: 5×10-4-1×10-2 and 2×10-3-1×10-1 mol/l, with the slope of 83.1 and 89.1 mV/рС respectively. The content of the EAS in the composition of the membrane with a content of 4-8% slightly affects the basic electroanalytical characteristics of the sensors manufactured. Further, an increase in the content of the associate leads to thickening and increases the rigidity of the membrane, which causes the deterioration of the steepness value and the limits of detection of the test substance. Significant influence on the results of the work of the electrodes may alter the quantitative content of the plasticizer in the membrane. The research was carried out for membranes containing DBF of 35-75%. As a result of measurements, it was found that electrodes with content of plasticizer of 45-70% possess good electroanalytical characteristics. The operating range of the acidity of the functioning of the electrode is equal to the pH range 9-11. Stable values of electrode potentials are set within 5-10 seconds. Synthetic membranes are suitable for work for at least 4 months. Efficient techniques of the potentiometric determination of the content of mefenamic and phenylanthranilic acids in model solutions and pharmaceuticals were developed.

In this paper, the MgO nanoparticles were used to develop a low-cost carbon paste electrochemical sensor. This sensing platform was used to construct a mediator-free sensor for phenobarbital detection. MgO NPs act as the catalytically active sites for the oxidation of phenobarbital due to their excellent electrochemical properties. The experimental results indicate the excellent catalytic activity of the MgO nanoparticles modified carbon paste electrode (MgO−CE) toward phenobarbital. The cyclic voltammetric results show the significant enhancement of oxidation current (62%) and reduce over-potential oxidation (287 mV) of phenobarbital at the MgO−CE. The improvement of electrochemical signals is due to the accelerated electron transfer between the CE and the phenobarbital. The proposed MgO−CE offers a wide linear range from 1 μM to 1800 µM with a low limit of detection of 0.34 µM and good reproducibility. Given the sensitivity, simplicity, low-cost, accessibility ‎of the materials, it can potentially apply in clinical applications as phenobarbital sensors.

Due to the importance of sulfide removal from wastewater and waste streams, in this study, eight cost-effective electrocatalysts were designed and prepared by electrochemical technique and their performance was evaluated in the presence of a high concentration of sodium sulfide. According to the results, among the prepared electrocatalysts, CuNiDH-NP@G electrode (modified graphite with nitroprusside (vasodilator drug) and CuNi-double hydroxide) had the highest efficiency in sulfide electro-oxidation. Then, to improve the performance of the CuNiDH-NP@G electrode its structure was optimized and investigated by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). Based on the results of electrochemical analyzes, in the presence of sulfide the process is controlled by diffusion. The diffusion coefficient, heterogeneous electron transfer rate constant and electron transfer coefficient for sulfide electrochemical oxidation were determined 2.85 × 10-5 cm2/s, 3.126 cm.s-1 and  0. 72 respectively. The use of non_noble metals as the electrocatalyst for sulfide electro-oxidation, the very easy, affordable, and fast preparation of the introduced electrode and high performance of it demonstrate important items for the use of this procedure and electrode in the subsequent investigation of a different material.

A new nanocatalyst was prepared using montmorillonite (MMT) clay mineral as a low-cost substrate incorporation with platinum and osmium nanoparticles for electrocatalytic oxidation of methanol molecules. The morphology and microscopic structure of the nanocomposite film formed at the surface of the fluorine tin oxide (FTO) electrode, were characterized by scanning electron microscopy and energy dispersive X-ray analysis. The electrocatalytic activity of the Pt-Os/Clay/FTO modified electrode was compared with Pt/FTO and Pt/Clay/FTO electrodes using cyclic voltammetry and chronoamperometry techniques and it was found that the Pt-Os/Clay/FTO electrode has a better performance for oxidation of methanol molecules. The exchange current density (J0) values for Pt/FTO, Pt/Clay/FTO and Pt-Os/Clay/FTO were calculated using the Tafel equation and they were found to be: 2.48×10-6, 4.01×10-6 and 8.45×10-6 mA cm-2, respectively. The results indicate that the purposed electrode accelerates significantly the process of methanol electrooxidation. The effects of various parameters on the electro-oxidation of methanol molecules were investigated and the obtained experimental results were discussed. The new modified electrode, showed a significant electrocatalytic activity for methanol electrooxidation over the other Pt-modified electrodes.

The selection and development of active material is a challenge. The active sensing materials may be of any kind as whichever acts as a catalyst for sensing a particular analyte or a set of analytes.  Nickel oxide (NiO) nanoparticles are formed by using the co-precipitation method and analyzed by XRD, SEM, and EDAX techniques. The NiOMCPE was formed by using a certain amount of graphite powder, silicon oil, and different quantity of (2mg, 4mg, 6mg, and 8mg) NiO nanoparticles and further a bare carbon paste electrode was prepared by using a known amount of graphite powder and silicon oil. The NiOMCPE was used to analyze the parameters like scan rate, pH and concentration of L-tryptophan (TRP), and concentration and scan rate of uric acid (UA). Further, the modified electrodes were used for interference study and simultaneous determination of mixtures of L-tryptophan and uric acid. The same method can also be used for some other bioactive molecules.

In the present investigation, a potentiometric sensor using molecularly imprinted polymer (MIP) of Cefotaxime sodium (CS) drug was produced. The MIP was synthesized using CS as a drug, Meta acrylic acid as a monomer, and triethylene glycol as a cross-linker. Furthermore, potentiometric sensors were produced by dispersing CS MIP in Ortho-nitro phenyl octal ether and reinforcing it into a PVC matrix (PME) and PVC coated on graphite (CGE). There was a linear electrode response ranging from 3.0×10–7 to 1.0×10–2 M having 57.9 mV decade–1 as slope and a limit of detection of 9.0×10–8M for CGE. The pH-independent region ranged from 4.5 to 9.2, and the flow injection analysis (FIA) system depicted a lifetime exceeding eight weeks. The separate solutions technique was utilized to determine the selectivity coefficients for numerous ions. As indicated by our results, the selectivity coefficients for the entire implemented anions, had a magnitude of ≤10–3. The design and assembly of the flow cell were not complicated and extended usage did not overburden the memory. The suggested sensor was successfully used to directly ascertain the levels of both real and synthetic Cefotaxime samples.

Tamoxifen (TAM) is a selective estrogen receptor modulator used in the treatment of breast cancer, women’s infertility and some other endocrine diseases. TAM is a generic medication that is prescribed relatively a lot. Due to the impact of this medication and its side effects, screening TAM level in biological samples and in pharmaceutical formulations are of great importance. Various analytical techniques are developed for the detection or monitoring TAM levels in different matrices. Since TAM chemical structure is able to undergo electrochemical oxidation, electrochemical techniques due to their remarkable features are also considered as analytical methods. Here, electroanalytical measurements of TAM will be reviewed.

Electrochemical biosensors have been widely used to detect several biomolecules, such as viruses, because they have been shown to have several advantages, including portability, good sensitivity, high specificity, fast response, and easy to use. A biosensor that utilizes aptamer as a bioreceptor is known as an aptasensor. Compared with antibodies, aptamer has several advantages, such as smaller size, easy synthesis and chemical modification, thermal stability, lower toxicity, high affinity, and excellent sensitivity. Aptasensor exhibits very high sensitivity, specificity, and reproducibility to a wide variety of target analytes. This review explains, that the aptamer can be immobilized on the surface of the electrode by various immobilization techniques. This review describes the use of the aptamer-based biosensor for viruses detection including the development of the aptamer immobilization technique in an electrochemical aptasensor. Several applications of using the aptamer-based biosensor for viruses detection including the development of the aptamer immobilization technique in electrochemical aptasensor in the last past eight years are proposed in this review.