Analytical & Bioanalytical Electrochemistry
Volume:12 Issue: 2, Feb 2020

A rapid electrochemical analysis of sulfadiazine (SFZ) has been carried out by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods by employing a sensitive single walled carbon nanotube-molybdenum disulfide nanocomposite/poly ethylene glycol modified carbon paste electrode (SWCNT-MoS2/PEG/CPE). The SFZ shows anodic peak potential at 0.94 V (vs. Ag/AgCl) in 0.1 M PBS of pH 7.0. The SFZ has been examined at different scan rate from 50 to 300 mVs-1 in 0.1 M PBS of pH 7.0 and the nature of mass transfer route is diffusion-controlled process. The different pH from 5.6 to 8.0 was analyzed at SFZ and obtained the slope value 0.063 proves the equal number of electrons and protons were involved in the reaction. In DPV mode LOD of SFZ in the linear range of 2-90 μM was found to be 1.69 μM. The prepared electrode was examined by electrochemical impedance spectroscopy (EIS) using 5 mM K3[Fe(CN)6] in 0.1 M KCl. The effective surface area of SWCNT-MoS2/PEG/CPE was found to be 0.262 cm2. This method could be successfully employed to determine the concentration of SFZ in biological fluids.

Clay modified carbon paste electrode (CPE-C) its applicability for electroanalysis of N, N’-ethylene-2,2’-bipyridinium (diquat) has been described in the present work. Electrochemical modification was performed by electronic impedance spectroscopy (EIS) and cyclic voltammetry (CV) in the range of -0.6 V to 1.2 V in 0.1 M K2SO4 (pH 3). The voltammetric method behavior of DQ is suggested where an anodic and cathodic peak appeared at Epa=0.55 V and Epc=0.1 V, successively. These peaks obtained from the reversible redox of DQ at the CPE-C surface. The optimal preconcentration time and percentage of clay insert were 10 min and 20% respectively. The proposed method exhibits certainly an electro-catalytic success toward DQ redox. The peaks current recorded using cyclic voltammetry has been linearly dependent on the DQ concentration ranging from 1×10-5 to 5×10-5 molL-1. The detection limit (DL) calculated for the anodic peak is 5.33×10-8 molL-1. Then relative standard deviation for 2×10-5 molL-1 diquat has been 4.3% for nine repetitions. The proposed detector has been successfully applied for DQ electroanalysis in a river water sample with a DL of 8.17×10-8 molL-1.

In the study, novel and sensitive carbon paste electrodes (CPEs) developed for thepotentiometric measurement of Cr(III) and Mg(II) ions in pharmacological and water samples.CPEs as indicator electrodes were prepared from a mixture of four components, includinggraphite powder, paraffin oil, multi-walled carbon nanotubes (MWCNTs), and a greenionophore (Chitosan Schiff base derivative). Optimization of CPE composites indicated thatthe critical factor in the preparation of the CPEs was chitosan Schiff base derivative whichselectivity proposed sensors highly depended on this factor. Effects of various parameters suchas pH, lifetime, response time, and selectivity of the potentiometric sensors to determine Cr(III)and Mg(II) ions were also evaluated. The results indicated that the proposed sensors can beapplied in a relatively wide range of pH, long lifetimes, short response times, and excellentselectivity for the analyte determination. The prepared sensors show Nernstian slopes of 19.53and 29.83 mVdecade−1, and LODs of 5.6×10– 8 and 4.4×10−9 with RSDs lower than 2.3% forCr(III) and Mg(II) ion determination, respectively. The calibration curves were linear in theconcentration ranges of 1.0×10-7-1.0×10-2 and 1.0×10-8-1.0×10-3 M, and R-square of 0.989 and0.987 for the measurement of Cr(III) and Mg(II) ions, respectively. Besides, the sensors weresuccessfully utilized for the Cr(III) and Mg(II) ion measurement in real samples such as tabletand tap water samples with suitable recovery higher than 97.6%.

This study set out to examine the cystoseira gibraltarica extract (CG) as an environmentally sustainable corrosion inhibitor for carbon steel in 1.0 M HCl medium. The corrosion inhibiting effect has been studied by conventional methods such as gravimetric (weight loss) and electrochemical (EIS and PDP) methods. All the methods used in this study confirm that cystoseira gibraltarica extract has a potential inhibitory effect of carbon steel in hydrochloric acid medium. The inhibitory efficiency reached at a maximum value of 90.3% at a concentration of 0.8 g/L, this efficiency was slightly decreased at high temperature. The results obtained by the polarization show that this ecological inhibitor acts as a mixed inhibitor. The parameters thermodynamics show that the studied inhibitor is adsorbed on the metal surface following Langmuir isotherm.

Electro analysis of 2-Aminothiazole (2-AT) by a low cost poly Glycine modified Pencil Graphite Electrode (poly Gly/PGE) was studied using of cyclic voltammetric (CV) and differential pulse voltammetric (DPV) techniques. The optimal experimental conditions to determine 2-AT was setup by the variation of the current with scan rate, concentration and pH. Electrochemical performance of the 2-AT at poly Gly/PGE was found adsorption-controlled reaction. A plausible electro oxidation mechanism was proposed. The anodic peak current of DPV was found to be linearly proportional to the 2-AT concentrations in the range from 1.0×10-6 to 12.0×10-6 M with a detection limit 7.29×10-8 M with better selectivity and sensitivity under the optimal conditions. Quantitative analysis of 2-AT levels in urine as real sample was carried out by applying this proposed method. Moreover, some common interfering substances were used to the study of interference. The clinical and quality control laboratories can employ this method to determine 2-AT.

The electrochemical behavior of tetrahydrozoline (THZ) was explored by cyclic voltammetry and differential pulse voltammetry. A well-defined peak at 915 mV using gold nanomodified electrode (AuNPts/CP) in presence of sodium dodecyl sulphate (SDS) was detected. Different buffers, pH and scan rates on oxidation peak current were studied. Linear calibration curve was achieved in the range of 1.99×10−5 to 7.79×10-5 M with a limit of detection (LOD) 5.54×10-6 M and limit of quantification (LOQ) 1.69×10−5 M, respectively.The suggested method was successfully utilized to the eye drops dosage form and urine sample with percentage recovery, 98.86%±0.77, and 101.13±0.62, respectively.

A novel recognition method for selective determination of the hyoscine N-Butyl bromide (HBB), an antispasmodic agent for smooth muscles, was devised using extended gate field-effect transistor (EG-FET) as transducing unit. For this purpose a PVC membrane, containing hyoscine n-butyl-tetraphenyl borate ion-pair as recognition component, was coated on Ag/AgCl wire, which was connected to the extended metal gate. In optimal conditions, the linear range for HBB was 10-8-10-5 molL−1 with limit of detection 1.7×10-9 molL-1. The proposed sensor was applied in real sample, it showed fast response with high accuracy, and therefore it could be used as HPLC detector in the pharmaceutical samples in quality control.

The foregone studies have shown that nicotinic acid cannot produce noticeable reductive signal at carbon-based electrodes without appropriate modification of the electrode. This is an obvious reason that mercury is known as the main electrode material for electro-reduction of nicotinic acid. In this study, it has been shown that it is possible to create a remarkable reduction signal for NA at a carbon paste electrode (CPE) without any modification. This achieved by precisely adjustment of electroanalysis pH, appropriately choosing of binder kind, precisely controlling of the percentage of the binder in the electrode composition and utilizing of an effective voltammetric technique. A carbon paste electrode, containing 30% of n-eicosane (as binder) was shown to be the best electrode for NA determination. It was also shown that utilizing of square wave voltammetry in place of differential pulse voltammetry led to remarkably improvement in the analytical signal of NA. The pH value of the electroanalysis solution was shown to be a crucially effective factor for creating of NA signal and an optimum value of pH equal to 2.2 was chosen as the best pH condition. The optimized method exhibited a dynamic concentration linear range of 3.0×10−6-3.0×10−3 molL-1 with a detection limit of 5.63×10−7 molL-1. As an analytical application, the proposed sensor was successfully used for determination of nicotinic acid in the urine, serum and pharmaceutical samples.

Nanoparticles of ytterbium tungstate prepared through the direct addition of an Yb3+ solution to a tungstate solution, were computed through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS). Further the supercapacitive characteristics of the nanoparticles, as a potential material for constructing electrodes, were evaluated through cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). Electrodes made of the Yb2(WO4)3 had a specific capacitance (SC) value of 336 F g-1 in a 2.0 M H2SO4 solution at a potential scan rate of 2 mV s-1; and 298 F g-1 at a current density of 1 A g-1 based on GCD tests. The electrodes also revealed to have a 95.8% cycling durability after 4000 potential cycles.

The electrochemical properties of a modified carbon paste electrode with the synthesized compound of 2,2'-[1,7–heptanediylbis(nitrilomethylidene)]-bis(4-hydroxyphenol) (DHBH) and graphite nanoparticle (GN) were studied by cyclic voltammetry (CV), chronoamperometry and differential pulse voltammetry (DPV) methods. The proposed electrode shows excellent electrocatalytic activity towards the oxidation of NADH under the optimum pH of 7.0. The modifier and nanoparticle simultaneously lead to a reduce overpotential of NADH oxidation about 250 mV and enhance current about 6 μA of the unmodified CPE. This electrochemical sensor exhibited a detection limit (3σ) of 13.4 nM with two linear dynamic ranges (0.01-6.0 and 6.0-400.0 μM) for the determination of NADH. The modified electrode can detect well NADH (180 mV) in the presence of Uric acid (360 mV) simultaneously. Also, the performance of the proposed sensor was evaluated in real samples.