Analytical & Bioanalytical Electrochemistry
Volume:12 Issue: 7, Jul 2020

In the present paper, poly(Tyrosine) modified graphene paste electrode (PTMGPE) was fabricated by utilizing an electropolymerization technique. Deposition of polymer film at bare graphene paste electrode (BGPE) was characterized by field emission scanning electron microscopy (FE-SEM). The PTMGPE was applied for Voltammetric detection of catechol (CC) and its quantification in phosphate buffer solutions of pH 7.0 (PBS). The detected cyclic voltammetric oxidation current of CC and phloroglucinol (PG) on PTMGPE is nearly 4 times higher with controlled over potential as a contrast to BGPE. This result shows the electrocatalytic effect of the poly (Tyrosine) layer. The differential pulse voltammetry (DPV) results show that CC and PG can be detected instantaneously using PTMGPE with peak separation of 0.300 V between CC and PG. Also, DPV showed two linear current responses in the concentration range of 2×10-6 to 1×10-5 M and 1.5×10-5 to 5×10-5 M with a coefficients of correlation 0.9951 and 0.9976 respectively. The detection limit (DL) and quantization limit (QL) were found to be 3.04×10-7 and 10×10-7 mol L-1 respectively. Further, we have also studied real sample analysis in tap water using proposed PTMGPE in the form of recovery studies and the achieved outcomes are found to be excellent agreement with the previous results. The PTMGPE shows exceptional selectivity, good sensitivity, and steadiness, making it as an attractive and alternative sensor for concurrent determination of CC and PG.

In this investigation, Ti/TiN nanolayer and TiN single layer coatings were coated on substrate of AISI 316L stainless steel by applying physical vapor deposition (PVD) using the type of cathodic arc evaporation (CAE). The evaluation of microstructure were carried out using x-ray diffraction (XRD), nanoindentation, atomic force microscopy (AFM) as well as scanning electron microscopy (SEM). Polarization and impedance tests were utilized to study the coatings corrosion behavior in the simulated body solution (SBF) in different immersion times. Utilizing CAE technique, high density and adhesion Ti/TiN nanolayer and TiN single layer coatings were successfully made. The corrosion results showed that Ti/TiN nanolayer coating had an exceptionally high polarization resistance compared to 316L substrate and TiN single layer coating. Furthermore, the corrosion results indicated the desired corrosion behavior in the nanolayer coating towards the single layer within the SBF, as a result of the distinct layers presence resulting in a barrier against penetration of the corrosive media.

The precise analysis of redox chemistry of MN4-based macrocyclic complexes is of great importance because of stabilization of unusual oxidation states of metal ions by macrocyclic ligand and thus have various applications in biochemistry, electrochemistry, electrocatalysis, pharmaceuticals etc. In this work, MN4-macrocyclic complexes of Co (II) and Ni(II) transition metal ions have been synthesized by using template condensation method. Further, the MN4-macrocyclic complexes were characterized by elemental, molar conductance and multiple spectroscopic analysis. The spectral and elemental analysis suggested that both complexes would possess the saddle shape distorted octahedral geometry. Further, the electrochemical investigation of both complexes was carried out by cyclic voltammetry. Both complexes showed quasi-reversible one-electron transfer redox process indicating the stabilization of oxidation state of central metal ions. Moreover, the MN4-macrocyclic complexes have shown to have good antimicrobial activity against the various pathogens such as Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Bacillus subtilis (B. subtilis) and Staphylococcus aureus (S. aureus).

In recent years, electrochemical supercapacitors have received considerable attention from many researchers. Metal oxides such as chromium oxide with high redox activity, high specific capacity, and excellent reversibility are suitable alternatives to ruthenium oxide in supercapacitor applications. In this study, first, graphene oxide (GO) was synthesized by the modified Hummers method. The synthesized GO was reduced using hydrazine hydrate (HH.rGO) and thermal reduction (Th.rGO). Also, chromium oxide (Cr2O3) was synthesized using a simple method. The synthesized compounds were characterized using the scanning electron microscope, infrared spectroscopy, and X-ray diffraction methods. Then Cr2O3 and reduced GO were mixed in N-methyl pyrrolidone at a ratio of 20:80. Electrochemical properties of HH.rGO/Cr2O3 and Th.rGO/Cr2O3 nanocomposites were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, and chronopotentiometry methods. The supercapacitor studies show that the nanocomposites have excellent reversible supercapacitor behavior and suitable electrochemical performance. The specific capacity of HH.rGO/Cr2O3 and Th.rGO/Cr2O3 electrodes were 101 F/g and 151 F/g, respectively at the scan rate of 2 mV/s. These results indicate that the composition of Cr2O3 with GO increases the specific capacity of supercapacitor due to the synergistic effect of GO and metal oxide.

The corrosion inhibition and adsorption (CIA) performance of the aqueous extracts of Aaronsohnia pubescens aerial parts (Odorized aqueous extract (OE) and Deodorized aqueous extract (DE)) on the corrosion mild steel (MS) in 1M hydrochloric acid were evaluated. It is based on the weight loss (WL) analysis, kinetic and thermodynamic parameters, and electrochemical methods both stationary (Potentiodynamic polarization (PDP)) and transient (Electrochemical impedance spectroscopy (EIS)). The inhibition efficiency of inhibitors increases for the concentration of 1.5 g/L; reaching a high value of 93.11 and 87.88 % in 1 M HCl solution at 308 K for OE and DE, respectively. The thermodynamic kinetic parameters showed that the adsorption of OE and DE on the MS surface follows the Langmuir adsorption isotherm. Furthermore, PDP measurements exhibited that the studied of each inhibitor performs as a mixed-type inhibitor. OE shows itself to be the best aqueous extract of Aaronsohnia pubescens aerial parts to prevent against the corrosion of mild steel.

In this study, a simple strategy was described for the synthesis of Pt-SWCNTs conductive nanocomposite by microwave heated polyol method and nanocomposite characterized by EDS, FESEM, and XRD method. The Pt nanoparticles were decorated at the surface of SWCNTs with a diameter of 22.3 nm. The synthesized nanocomposite was used for modification of the carbon paste electrode (CPE) in the presence of n-hexyl-3-methylimidazolium hexafluorophosphate (nH3MHP) and paraffin oil as binders. The Pt-SWCNTs/nH3MHP/CPE was showed a good catalytic effect for electro-oxidation of the 5-fluorouracil anticancer drug in aqueous solution. In comparison to CPE, the Pt-SWCNTs/nH3MHP/CPE increased oxidation current of 5-fluorouracil (⁓4.47 times) and reduce oxidation potential of this anticancer drug ⁓125 mV. On the other hand, Pt-SWCNTs/nH3MHP/CPE was successfully used for the determination of 5-fluorouracil anticancer drugs in injection samples with acceptable recovery data (96.13%-103.5%). According to recorded results, the sensor has a powerful tool for determination of 5-fluorouracil anticancer drug in real samples.

Plant extracts are extensively researched as a source of green corrosion inhibitors. Herein, we report on a highly efficient and thermally stable corrosion inhibitor from the stem extract of high-altitude shrub Berberis aristata. The corrosion inhibition efficiency (IE) of the extract was tested in 1.0 M H2SO4 for the corrosion protection of mild steel (MS) by using gravimetric and electrochemical measurements. It displayed a remarkable IE of 90% at 200 ppm and reached to 98.18% at high concentration (1000 ppm) at room temperature. The thermal stability of the adsorbed extract was uncommon among the recently reported plant extracts, giving an IE of 80% at 338K. Besides, the adsorption of the extract was extremely efficient, producing an IE of 90% in 15 min. The thermodynamic parameters (ΔG and Ea) showed a chemisorption dominated behavior of the extract. Electrochemical measurements indicated a mixed type of inhibitor, and the extract suppressed the corrosion rate by blocking the active surface of the MS.

"Green analytical chemistry" (GAC) succeeded to become an eco-friendly environmental crucial area in the field of analytical chemistry targeting at the chemical processes' and products' optimization regarding to material consumption, generation of waste and intrinsic safety, toxicity and environmental burdens. For an expressive comparison, an electro-analytical in-line potentiometric selective determination of Doxylamine succinate (DOX) in a multi- component pharmaceutical dosage form containing both Caffeine (CAF) and Paracetamol (PAR) has been successfully developed and validated. A real-time monitoring of the dissolution profile of DOX from its pharmaceutical formulation was achieved by the proposed sensor without any interference from paracetamol or caffeine even without pretreating neither the sample nor its derivatization. A cationic exchanger; Potassium tetrakis (4-chlorophenyl) borate (KTCPB), polyvinyl chloride (PVC) based membrane and a plasticizer; 2-nitrophenyl-octyl-ether (2-NPOE) were employed for the fabrication DOX-selective sensor. The proposed sensor showed Nernstian response slope of 29.8 mV/concentration decades from 10-6 to 10-2 mol L-1. ICH guidelines' validation parameters; linearity, accuracy, precision and robustness were performed on the proposed green eco-friendly potentiometric method.

As the electrochemical method, the Fast Fourier Transform (FFT) Stripping Cyclic Voltammetry detection method was designed for measurement and monitoring of adsorbed mercury ions by new modified adsorbent based on mesoporous silica as a new adsorbent. In this respect, SBA-15 as mesoporous silica and 1, 3, 5 Trithiane as effective modifier ligand were chosen, and the modification process was carried out physically. Continuing research application of modified mesoporous silica for the removal of mercury ions (Hg2+) from the aquatic environment in different pH, the weight of adsorbent and, stirring time as the major parameters were investigated and analysis of flow-injection was used as the major method for determination of adsorbed mercury ions by modified SBA-15. Also, a special computer numerical technique is used to calculate Hg response based on the total charge exchange at the electrode surface, where the currents were integrated into the range of reduction of Hg. The time for stripping was less than 300 ms. The results showed that the best Hg2+ ions removal conditions were achieved at the 15.0 mg of modified adsorbent, pH 5.0 and stirring time 15 min; Also the maximum percentage removal of Hg2+ ions and the capacity of the adsorbent were found to be 85% and 10.6 mg of Hg2+ ions /g modified SBA-15, respectively.

A precise and simple in-situ voltammetric measurement of promethazine, based on the nano sized molecularly imprinted polymer (nano-MIP) was introduced. The nano-MIP was synthesized utilizing vinyl benzene and Divinylbenzene as the functional monomer and cross-linker respectively, and via the micro-emulsion polymerization method in silicon oil. The MIP particles were then embedded in a carbon paste electrode (CPE) in order to prepare the MIP-CP electrode. This electrode showed higher response to analyte, compared to the both bare CPE and modified with non-imprinted polymer. Also, the selectivity of the MIP-CPE was investigated using some of the cross reactants and the sensor was clearly selective towards the PMZ. Various factors, known to affect the response behavior of the sensor, were investigated and optimized. This sensor exhibited two distinct linear response ranges of 4× 10-9-4×10-7 M and 4×10- -7×10-6 M in optimum analysis conditions. Limit of detection was calculated equal to 1.4×10-9 M (S/N). An interestingly low RSD equal to 1.2% was found for 4 separate determinations by the proposed sensor. The sensor was applied for PMZ in-situ determination in plasma samples without applying any sample pretreatment.