جستجوی مقالات مرتبط با کلیدواژه « glassy carbon electrode » در نشریات گروه « شیمی »

The paper describes a scientific study involving the use of an over-oxidized p-aminophenol sensor for the quantification of sunset yellow in the presence of tartrazine. The study utilized the electropolymerization method on a glassy carbon electrode and employed the Box-Benken method to optimize parameters such as pH, step voltage, number of electropolymerization cycles, and precipitation potential. The study assessed the electrode's selectivity towards various ionic species and found no significant interference. It determined a linear range between 0.25 and 300.0 µ mol L-1 for sunset yellow, with a detection limit of 0.09 µ mol L-1. The electrode modified with PAP-OX underwent assessments of repeatability and reproducibility, yielding relative standard deviation (RSD) values of 1.14% and 4.09%, respectively. The primary objective of the research was to quantify the concentration of Sunset Yellow in different food samples, including ice cream, fruit juice, powder jelly, Smarties, and chocolate, while considering the presence of tartrazine. Overall, the study focused on developing a sensor for the quantification of sunset yellow in food and drink samples, with a particular emphasis on optimizing the sensor's performance and assessing its reliability for practical applications.

The present study aims to introduce a highly sensitive electrochemical sensor for quantification of trace amounts of Sumatriptan (SUM) in biological fluids. To immobilize a stable nano film of β-cyclodextrin (β-CD) on a glassy carbon electrode (GCE), electropolymerization of monomer was carried out within 0.1 M phosphate buffer with pH 6.0 utilizing cyclic voltammetry to yield polymerized β-CD (pβ-CD). The morphological characterization of pβ-CD/GCE was examined by Field emission scanning electron microscopy (FESEM). The electrochemical redox action of SUM on pβ-CD/GCE was scrutiny studied by cyclic voltammetry and chronocoulometry. The electrochemical parameters including the electron transfer coefficient (α), the standard heterogeneous rate constant (ks), the surface area of the electrode (A), the electron transfer number (n), and the surface coverage (Γ) were estimated to be 0.38, 1.23×10-3 cm s-1, 0.06 cm2, 1, 1.07×10-8 mol cm-2, respectively. At optimized criteria, a substantial enhancement was attained toward the electrooxidation of SUM on the developed electrode compared to the bare GCE, resulting in wide linear ranges of 0.0622.47µM and 2.4752.1µM with a low detection limit of 27 nM. The developed sensor was successfully employed for quantification of SUM in human blood serum and urine samples with good selectivity and acceptable recoveries, proving its utility for further applications as a sensitive and reliable sensor.

The electrochemical behavior of epinephrine (EP) at the catechol modified glassy carbon electrode (catechol/GCE) in phosphate buffer solution (PBS, pH = 7.0) was examined using cyclic voltammetry (CV), chronoamperometry (CA) and differential pulse voltammetry (DPV). The results of electrochemical studies confirmed the ability of catechol to accelerate the electron transfer process and reduce overvoltage for the oxidation of EP. DPV studies showed two dynamic ranges, of which in the low concentration range of EP, the detection limit was reported to be 1.6 µM. Moreover, the reproducibility, repeatability and selectivity of the designed sensor were investigated using DPV method. The selectivity of this sensor was studied in the presence of interfering substances such as glucose, fructose, ascorbic acid, sodium chloride, potassium chloride, norepinephrine and dopamine. Catechol/GCE was used for quantitative measurements of EP in human blood serum sample. DPV studies reported two linear segments with slopes of 0.0186 and 0.0068 µA µM-1 in the concentration ranges of 5.0-80.0 and 100.0-900.0 µM, respectively. The detection limit (3Sb/m) and sensitivity for the low concentration range of EP were found to be 1.61 µM and 0.6 µA µM-1 cm-2, respectively.

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.

Computational chemistry induced several fast, cost-effective revolutionary solutions for chemistry laboratories. The reliability of such solutions has been questioned in several studies. The current work introduces an experimental validation for the computational selection of an ionophore during potentiometric sensor optimization. We studied the correlation of the experimental sensor performance parameters to the computational binding scores of the embedded ionophores and the drug (loperamide hydrochloride). The study included eight sensors of different PVC-membrane compositions. The PVC-membrane containing phosphotungstic acid, dioctyl phthalate, and carboxymethyl-β-cyclodextrin developed a Nernstian slope of 59.69 mV/decade and a detection limit of 2.95×10-7 mol L-1. The sensor demonstrated a fast and stable response within a linear range of 2.99×10-6-9.09×10-3 mol L-1. We examined the drug-ionophore binding using molecular modeling and docking. The docking scores (binding energy) of the cyclodextrin derivatives strongly correlate to the studied sensors' experimental performance parameters (Nernstian slope). Performance and validation parameters were computed, and the results were statistically comparable to those of the reported method. Practically, the absence of sample preparation, chromatographic separation, high-purity solvents, and costly instrumentation are incomparable advantages of the developed method relative to the reported ones.

In this study, the electrochemical determination of oxazepam in plasma samples was studied. The composite of graphene oxide/boron (B-RGO) was synthesized via the hydrothermal method and it was cast on the glassy carbon electrode (GCE). The polyaspartic acid (poly(ASP)) was deposited on the B-RGO by electropolymerization to prepare the modified electrode named B-RGO/ poly(ASP)|GCE. The B-RGO and B-RGO/poly ASP were characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Electrochemical studies were performed by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV) methods. The experimental parameters affecting the reduction of oxazepam such as pH, preconcentration time, scan rate and other analysis conditions, and instrumental parameters were optimized. Under the optimal conditions, the linear range was obtained from 0.001 to 800 μM with a correlation coefficient of 0.998. The repeatability of the method for the electrode to electrode and one electrode were 4.3% and 4.9%, respectively. The limit of detection (LOD) of 0.3 nM and the limit of quantitation (LOQ) of 1 nM were obtained. The high efficiency of the developed electrode in the determination of oxazepam in the plasma sample was proved by using acceptable results and satisfactory relative recovery percentage (>90%). Based on our calculation, the heterogeneous electron transfer rate constant (ks) was 1.92 s-1. The interaction between oxazepam and modifier was single-layer and multi-layer adsorption, respectively in low and high concentrations.

A simultaneous electrochemical determination of serotonin (Ser), melatonin (Mel) and, tryptophan (Trp) was conducted for the first time in the presented research. A metal-metal-metal oxide nanocomposite (CuNi-CeO2-rGO) was synthesized and for modification of glassy carbon electrode (GCE), it was decorated at reduced graphene oxide (rGO). The differential pulse voltammetry (DPV) technique was applied to measurement of Ser, Mel and Trp at the surface of CuNi-CeO2-rGO/GCE. The electrical impedance spectroscopy (EIS) analysis of prepared bare and modified electrodes showed that the CuNi-CeO2-rGO/GCE has the lowest charge transfer resistant in comparison to GCE. The Transmission electron microscopy (TEM) and, X-ray Diffraction (XRD) techniques applied to check the characterization of synthesized nanomaterials. In contrast to the GCE, three separated and well-defined peaks appeared at the CuNi-CeO2-rGO/GCE at 369, 570 and 706 mV for Ser, Mel and Trp in the electrochemical potential window of 0.1-1.0 V. The chemical and electrochemical conditions of analysis were optimized and the detection limit of 5.8 nM (0.0058 µM) for Ser, 6.1 nM (0.0061 µM) for Mel and 6.3 nM (0.0063 µM) for Trp, were calculated based on 3Signal/Noise. The applicability of the CuNi-CeO2-rGO/GCE was investigated by determining target analytes in human urine and blood plasma and comparing the obtained data with HPLC data. The obtained data were in good agreement with each other which demonstrates that the presented method was one of the best analytical methods for the monitoring of Ser, Mel and Trp in the laboratory.

In this work, three dimensional NiO nanowrinkles (3D NiO-NWs) were prepared and used as electrode materials to modify the surface of a glassy carbon electrode (3D NiO-NWs/GCE). Then, differential pulse voltammetry (DPV), cyclic voltammetry (CV) and chronoamperometry (CHA) were employed to determine the electrochemical response of theophylline on as-fabricated sensor. The electrochemical theophylline oxidation was elevated on the modified electrode. The peak current on the modified electrode in phosphate buffer solution (PBS, 0.1 M, pH=7.0) showed a linear elevation with an increase in the theophylline concentration (0.1-900.0 µM), with a narrow detection limit of 0.03±0.001 µM.

In the presented study, for the first time, simultaneous electrochemical measurements of ascorbic acid (AA), melatonin (Mel), and tryptophan (Trp) were discussed. The CuO-CeO2-rGO-MWCNTs nanocomposite was prepared, then applied for amendment of glassy carbon electrode (GCE) surface to the measurement of target analytes using differential pulse voltammetry (DPV) technique. Electrical impedance spectroscopy (EIS) techniques displayed that CuO-CeO2-rGO-MWCNTs/GCE has the lowest electron transfer resistance (Rct) in comparison to GCE and was suitable for electrochemical applications. The synthesized compounds were analyzed by powerful methods including Scanning Electron Microscopy (SEM) and, X-ray Diffraction (XRD). At the CuO-CeO2-rGO-MWCNTs/GCE, three oxidation peaks appeared at 0.309, 0.631, and 0.855 V for AA, Mel, and Trp and the peaks separation of ΔEp (AA and Mel)=322 mV, and ΔEp (Mel and Trp)=224 mV in the electrochemical potential window of 0.0-1.1 V. In optimum DPV condition and pH=5.0, a dynamic range of AA (0.01-28 µM), Mel (0.01-12.6 µM) and Trp (0.01-13.5 µM) with the detection limit of 9, 8 and 7.3 nM for AA, Mel, and Trp, respectively, were acquired. The provided modified electrode was successfully used to monitor the analytes in human biological fluids.

A new differential pulse voltammetric method was developed for determination of the non-steroidal anti-inflammatory drug; acemetacin. Various experimental parameters were studied, namely; electrode type, pH of the used buffer and scan rate on the reduction and oxidation peaks of acemetacin. The drug responded only to glassy carbon electrode among the studied working electrodes with higher peak current and sensitivity in the favor of the reduction side. The results also revealed that acemetacin best assayed through measuring its reduction peak current when prepared in Britton Robinson buffer solution at pH 8 when scanned at rate of 16 mV/s. The proposed method presented a bimodal calibration curve where each segment showed strong linearity. The linearity ranges were 1 - 100 µM for the lower segment and 0.1 - 3 mM for the higher one with detection limit of 0.1 µM. The proposed method was successfully applied for determination of acemetacin in its pharmaceutical dosage form.

Electroanalysis of orphenadrine (ORD) by graphene modified glassy carbon electrode (GPN/GCE) was studied using cyclic voltammetric and linear sweep voltammetric (LSV) techniques. The variation of the current with pH, concentration and scan rate was investigated to optimize the experimental condition for determination of ORD. The optimal pH value for voltammetric determination of ORD is the physiological pH 7.0. The electrochemical behavior of the ORD at GPN/GCE was a diffusion-controlled process. Under the optimal conditions, the anodic peak current was linearly proportional to the concentration of ORD in the range from 1.0 × 10-7 to 1.2 × 10-6M with a limit of detection 2.8 nM for LSV. This method was applied for quantitative determination of ORD levels in urine as real samples. Further interference study was also carried with some common interfering substances. The present method could possibly be adopted for the pharmacokinetic studies as well as for quality control laboratories.

The CeO2-SnO2/rGO was synthesized and used for modification of glassy carbon electrode (GCE) to measurement of Tramadol (Tra), Codeine (Cod) and Caffeine (Caf). Electrical impedance spectroscopy (EIS) techniques showed that CeO2-SnO2/rGO/GCE has the lower electron transfer resistance (Rct) (63 Ω) in comparison to GCE (223 Ω) and was suitable for electrochemical applications. The synthesized nanomaterials were investigated by some methods such as Transmission electron microscopy (TEM), X-ray Diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The pH value was investigated in the range of 5.5 to 9.5 which the best signal was obtained at pH=6.5. At the CeO2-SnO2/rGO/GCE three oxidation peaks appeared at 0.755, 1.05, and 1.412 V with Ipa= 22.1, 78.4 and 69.49 µA for Tra, Cod, and Caf and the peaks separation of ΔEp (Tra-Cod)=295 mV, and ΔEp (Cod-Caf)=362 mV in the potential region 0.4-1.6 V. In optimum condition, a dynamic range of 0.008-10 μM and 10-270 μM for Tra, 0.01-12 μM and 12-260 μM for Cod, 0.01-14 μM and 14-260 μM for Caf with the detection limit of 0.0056, 0.0053, and 0.0055 μM for of Tra, Cod and Caf, respectively, were obtained. Investigation of effect of scan rate (25 and 300 mV/s) shows that the electrode process was diffusion-controlled. Interference studies show that Li+, Na+, K+, Cl-, Ca2+, Uric acid, Ascorbic acid, Morphine, sucrose, and glucose have no effect on the oxidation current of the analytes. Finally, The presented electrochemical electrode was applied for the measurement of Tra, Cod and Caf in urine and human plasma spiked samples.

Isoproterenol is an important catecholamine-based drug that is widely used in the treatment of heart disease. The present paper introduced one of the new modifications for the surfaces of glassy carbon electrodes (GCEs) using the CuO nanoflowers (CuO NFs) for determination of isoproterenol. Electrochemical properties of the CuO NFs/GCE for detecting isoproterenol were tested using the cyclic voltammetry (CV), chronoamperometry (CHA) as well as differential pulse voltammetry (DPV). Electrochemical studies demonstrated an efficient isoproterenol oxidation, with enhanced peak current from 2.9 µA to about 10.0 µA (3.4% increase) and decreased peak potential from 500 mV to about 300 mV. The linear response for the determination of isoproterenol was obtained in ranges for concentrations between 0.3 and 450.0 μM under the most proper conditions and the limit of detection (LOD) equaled 0.09 μM. Also, the modified electrode is utilized for simultaneously determining isoproterenol and theophylline using DPV. The proposed CuO NFs/GCE sensor was effectively employed for the isoproterenol and theophylline detection in the isoproterenol ampoule and urine samples.

We applied GCE modified with Ce3+-NiO hexagonal nanoparticles (Ce3+-NiO HNPs) for preparing methyldopa electrochemical sensor. Electrochemical study of the modified electrode showed that within the optimal conditions of phosphate buffer solution (PBS) at a pH of 7.0 in CV, oxidation potency of methyldopa decline to ~100 mV at the modified electrode in comparison with an unmodified GCE. The sensor exhibits a sensitive response to methyldopa in range between 0.1 and 80.0 μM with a limit of detection (LOD) equal to 0.03 μM. In addition, as sensing materials for simultaneously determine hydro-chlorothiazide and methyldopa, Ce3+-NiO HNPs/GCE, exhibited high sensitivity. The defined and separated oxidation peaks of a mixture of methyldopa and hydrochlorothiazide were obtained with significant peak potential differences of 390 V. The proposed electrochemical sensor was employed in analysis of both drugs in the real specimens.

This study aims to develop a promising electrochemical sensor based on polymer film overoxidation following the electrochemical polymerization of p-aminophenol on a bare glassy carbon electrode (GCE) surface for the voltammetric determination of sumatriptan succinate (SUM). Cyclic voltammetry (CV), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and square wave voltammetry (SWV) were employed to characterize the electroanalytical performance and morphology of the modified electrode. The results indicated a significant improvement in electrode sensitivity to SUM after electrochemical polymerization and overoxidation of poly(p-aminophenol). We also investigated the effect of all effective instrumental and experimental parameters on sensor response. Under the optimum conditions (accumulation for 60 s at 0.055V and pH= 2.0) the electrode SWV response to SUM within the range 1.0-100.0 μmol L-1 with a limit of detection (LOD) of 0.294 μmol L-1 was linear under optimized conditions. We also attempted to evaluate the designed sensor selectivity to different interfering species, suggesting no significant interference. The designed sensor was also used to determine SUM in pharmaceutical preparations and human serum samples with minimal matrix effects, admissible recoveries (99-106), and satisfactory repeatability (1.2-5.1 %RSD). The proposed sensor exhibited admissible repeatability, reproducibility, and stability.

As a promising alternative for the mercury film electrode (MFE), the bismuth film electrode (BiFE) has been widely used in the field of electrochemical analysis. BiFE shows attractive properties and excellent performance such as environmentally friendliness, high sensitivity, easy preparation, well-defined signals and negligible effect to dissolved oxygen. According to recent experimental reports many electrochemical analysis have been studied with the use of BiFEs. Toxic heavy metal ions, pharmaceutical substances, pesticides and other biological molecules and products are determined with the BiFE. The voltammetric behavior of tannic acid (TA) at bismuth film modified glassy carbon electrode (Bi-GCE) has been studied by linear sweep voltammetry (LSV). Bismuth film was deposited on glassy carbon electrode (GCE) by single potential step chronoamperometric deposition at -450 mV for 120 s. TA shows a well-defined cathodic peak on the modified electrode at around -0.6 V vs. Ag/AgCl in Briton Robinson (BR) buffer solution of pH 3.6 at Bi-GCE. The effect of deposition time, deposition potential, bath concentration and pH of supporting electrolyte on the reduction current of TA were optimized. Under optimum conditions TA shows a linear range between 0.05 μM to 200 μM and the limit of detection (LoD) was found to be 0.035 μΜ. The developed method was used for determination of TA in tea samples.

The surface of the glassy carbon electrode (GCE) is modified with the composite of new Cobalt complex with a tetradentate Schiff base ligand derived from 3-ethoxysalicylaldehyde and 4,5-dimethyl orthophenylenediamine (CoOEtSal) and multi-walled carbon nanotube (MWCNT). The electrochemical oxidation of ascorbic acid (AA) and dopamine (DA) at the modified electrode was studied using the cyclic and differential pulse voltammetric techniques (CV and DPV). The effect of the scan rate and pH of the buffered solution on the electrode response is studied. An acceptable resolution of more than 285 mV for anodic oxidation waves of AA and DA is obtained using the modified glassy carbon electrode, and makes it very efficient for the simultaneous detection of these compounds. The Results show good peak resolution for AA and DA and the sub-micromolar detection limits for these compounds (0.07 and 0.04 μM for AA and DA respectively). The modified GCE was used successfully for the recovery of the analytes in human urine samples.

Isatins, derivatives of indole, represent important class of compounds belonging to nitrogen heterocycles. These compounds comprise synthetically vital substrates that are used as precursors for drug synthesis and raw materials for heterocycles etc. Research in this group of compounds has engrossed interest among scientific community in recent and past as Isatins are known to possess immense biological activities. Present work delineates synthesis, characterization, electrochemical and antimicrobial studies of four substituted derivatives of isatin derivatives. The cyclic voltammetric studies of all the analytes showed that four derivatives have better electro catalytic activity towards the analytes at glassy carbon electrode. These synthesized isatin derivatives were screened for their antimicrobial activity against Gram-negative bacteria (Escherichia coli and Staphylococcus aureus) and fungi such as Candida albicans and Penicillin chrysogenum, and found to possess considerable antimicrobial activity suggesting their effectiveness in developing antibiotics and novel drugs.

The use MOF-508a as sensing component for the precise discerning of bisphenol A via the electrochemical technique and its synthesis by a simple method were reported in the present study. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were applied to describe the MOF-508a’s composition and structure. In addition, MOF-508a was exploited so that the glassy carbon electrode could be altered for the bisphenol A’s electrochemical oxidation. The results were indicative of illustration of palpable oxidation peak with lowering over-potential by the designed MOF-508a /GCE. In addition, there was a greater signal response, compared to the unmodified electrode, which was primarily because MOF-508a offered the establishment of large active surface area. As such, this process led to a considerable improvement in the electrochemical surface area. Moreover, adding the elevating bisphenol A concentration resulted in a severe elevation in the anodic peak, presented by the measurements of differential pulse voltammetry (DPV). Furthermore, excellent sensitivity (0.0564 µA.µM-1) with low limit of detection (0.03 µM), a wide linear range (0.1–700.0µM), and high selectivity were shown by the analytical performance of the modified electrode.