Determination of Diosmin in Pharmaceutical Products with Chemically Modified Voltammetric Sensors

In this paper, the electrochemical behavior of two types of sensors based on modified screen-printed electrodes (one screen-printed electrode based on carbon (SPCE) and another screen-printed electrode modified with Prussian Blue (PB/SPCE)) was studied with the aim of sensitive detection of diosmin, an active pharmaceutical compound from the class of flavonoids. The scan electron microscopy technique was used for the morphological characterization of PB/SPCE. The preliminary analysis assessed the electrochemical behavior of SPCE and PB/SPCE in KCl solution and in a double solution of potassium ferrocyanide–potassium chloride. It was shown that the active area of PB/SPCE is superior to the one of SPCE, the greater sensitivity being related with the presence of the electroactive modifier. Similarly, in the case of diosmin detection, the PB/SPCE sensor detect more sensitivity the diosmin due to the electrocatalytic effect of PB. From the study of the influence of reaction rate on the sensor’s electrochemical response, it was shown that the detection process is controlled by the adsorption process, the degree of surface coverage with electroactive molecules being higher in the case of PB/SPCE. From the PB/SPCE calibration curve, it wasdetermined that it has high sensitivity and low detection and quantification limit values (limit of detection 5.22 × 10−8 M). The applicability of the PB/SPCE sensor was confirmed by sensitive analysis of diosmin in pharmaceutical products. The voltammetric method is suitable for the detection and quantification of diosmin in pharmaceutical products. The method is simple, accurate, and quick and can be used in routine analysis in the examination of the quality of pharmaceutical products and other types of samples.

Metal-N4@Graphene as Multifunctional Anchoring Materials for Na-S Batteries: First-Principles Study

Developing highly efficient anchoring materials to suppress sodium polysulfides (NaPSs) shuttling is vital for the practical applications of sodium sulfur (Na-S) batteries. Herein, we systematically investigated pristine graphene and metal-N4@graphene (metal = Fe, Co, and Mn) as host materials for sulfur cathode to adsorb NaPSs via first-principles theory calculations. The computing results reveal that Fe-N4@graphene is a fairly promising anchoring material, in which the formed chemical bonds of Fe-S and N-Na ensure the stable adsorption of NaPSs. Furthermore, the doped transition metal iron could not only dramatically enhance the electronic conductivity and the adsorption strength of soluble NaPSs, but also significantly lower the decomposition energies of Na2S and Na2S2 on the surface of Fe-N4@graphene, which could effectively promote the full discharge of Na-S batteries. Our research provides a deep insight into the mechanism of anchoring and electrocatalytic effect of Fe-N4@graphene in sulfur cathode, which would be beneficial for the development of high-performance Na-S batteries.

Rapid Electrochemical Monitoring of Tyrosine by Poly (Riboflavin) Modified Carbon Nanotube Paste Electrode as a Sensitive Sensor and its Applications in Pharmaceutical Samples

A poly(riboflavin) modified carbon nanotube paste electrode (PRFMCNTPE) is employed as a compatible and electrocatalytic sensor for the determination of Tyrosine (TYR). The analysis and assessment are carried out through differential pulse voltammetry (DPV) and Cyclic Voltammetry (CV). The surface of the intended sensor is examined through Field Emission Scanning Electron Microscopy (FE-SEM). The modified electrode shows the outstanding electrocatalytic effect for TYR with high selectivity and sensitivity as compared to carbon nanotube paste electrode (CNTPE). The electro-oxidation peak current of TYR and its concentration is found linear from 2 µM to 10 µM with a detection limit (LOD) of 0.45 µM. The developed sensor is productively applied for the determination of TYR in pharmaceutical samples like Tyrosine capsules. The adapted electrode shows good stability, excellent reproducibility, and remarkable sensitivity.

Application of Nanocomposites Based on Graphene and Metal Materials in Measurement of Nitrate/Nitrite in Food Samples

Nitrite (NO2 −) has been broadly applied in industrial and agricultural products; it is often found in various foods, water, environmental systems, and biological samples, though NO2 − is a toxic inorganic contaminant that is hazardous to the health of humans and other organisms. In recent years several approaches have been recommended for detecting and monitoring NO2 − that the electrochemical method is of very attention, among them, due to its easy miniaturization, cost-effective, rapidness, straightforward operation. Graphene nanocomposites have a considerable synergistic electrocatalytic effect toward the nitrite redox, magnifying the electrochemical response signals and improving the sensitivity, selectivity, and feasibility of the nitrite detection in various real samples. In this article, we report the recent developments in electrochemical sensors based on graphene/metal nanocomposites for the measurement of nitrate/nitrite in the food samples and identifying performances, including limit of detection (LOD), detection ranges, pH, sensitivity, stability, and technology used were determined.

Electrocatalytic Effect of Al2O3 Supported on Clay in Oxidizing of Ibuprofen at Graphite Electrode

In this work, the electro-catalytic oxidation of ibuprofen was studied using aluminum oxide supported on clay (Clay/Al2O3). The latter has been successfully prepared by impregnating aluminum particles in the clay by heat treatment. The electro-catalytic performances of Clay/Al2O3 for the oxidation of ibuprofen were studied using cyclic voltammetry (CV), chronoamperometry, and differential pulse voltammetry (DPV) in 0.1 mol L-1 of the phosphate buffer (pH = 7). It has been shown that the proposed catalyst exhibits remarkably an electro-catalytic effect performance vis-a-vis the oxidation of ibuprofen. In addition, the peak oxidation currents depend linearly on the ibuprofen concentration in the wide ranges from 1.0·10-3 mol L-1 to 1.0·10-6 mol L-1 with a detection limit of 1.95·10-8 mol L-1 and response time of 30 second. Possible interferences were evaluated in 1.0·10-5 mol L-1 ibuprofen. The proposed catalyst also indicated suitable repeatability and stability. Besides, the proposed CPE-Clay/Al2O3 has been successfully applied for ibuprofen analysis in human blood with good recoveries.

Cost-Effective Electrochemical Activation of Graphitic Carbon Nitride on the Glassy Carbon Electrode Surface for Selective Determination of Serotonin

A simple one-step electrochemical deposition/activation of graphitic carbon nitride (g-C3N4) is highly desired for sensor configurations and remains a great challenge. Herein, we attempt an electrochemical route to exfoliate the g-C3N4 nanosheets in an aqueous solution of pH 7.0 for constructing a sensor, which is highly sensitive for the detection of serotonin (5-HT). The significance of our design is to exfoliate the g-C3N4 nanosheets, a strong electrocatalyst for 5-HT detection. Investigations regarding the effect of neutral pH (pH 7.0) on the bulk g-C3N4 and g-C3N4 nanosheets, physical characterization, and electrochemical studies were extensively carried out. We demonstrate that the g-C3N4 nanosheets have a significant electrocatalytic effect for the 5-HT detection in a dynamic linear range from 500 pM to 1000 nM (R2 = 0.999). The limit of detection and sensitivity of the designed 5-HT sensor was calculated to be 150 pM and 1.03 µA µM−1 cm−2, respectively. The proposed sensor has great advantages such as high sensitivity, good selectivity, reproducibility, and stability. The constructed g-C3N4 nanosheets-based sensor platform opens new feasibilities for the determination of 5-HT even at the picomolar/nanomolar concentration range.

Customized In Situ Functionalization of Nanodiamonds with Nanoparticles for Composite Carbon-Paste Electrodes

The incorporation of nanomaterials on (bio)sensors based on composite materials has led to important advances in the analytical chemistry field due to the extraordinary properties that these materials offer. Nanodiamonds (NDs) are a novel type of material that has raised much attention, as they have the possibility of being produced on a large scale by relatively inexpensive synthetic methodologies. Moreover, NDs can present some other interesting features, such as fluorescence, due to surface functionalization and proved biocompatibility, which makes them suitable for biomedical applications. In addition, NDs can be customized with metallic nanoparticles (NPs), such as silver or gold, in order to combine the features of both. Raw NDs were used as modifiers of sensors due to the electrocatalytic effect of the sp2 and oxygenated species present on their surface. The aim of this research work is evaluating the applicability of NDs modified with silver (Ag@NDs) and gold (Au@NDs) nanoparticles for the development of a suitable (bio)sensing platform. A complete morphological and electrochemical characterization as a function of the prepared nanocomposite composition was performed in order to improve the electroanalytical properties of the developed (bio)sensors. In the present work, the optimal composition for Au@NDs present on the nanocomposite matrix is 3.5% and the one for Ag@NDs is 1%. Good results were obtained in the evaluation of the optimal composition towards hydrogen peroxide and glucose as a model analyte using a (bio)sensor based on graphite-epoxy-Ag@NDs (17:82:1).

Nano-sized Metal and Metal Oxide Modified Electrodes for Pharmaceuticals Analysis

: Electrochemical analysis offers a number of important advantages such as providing information on pharmaceuticals analysis and their in vivo redox processes, and pharmacological activity. The interest in developing electrochemical sensing devices for use in clinical assays is growing rapidly. Metallic nanoparticles can be synthesized and modified with various chemical functional groups, which allow them to be conjugated with antibodies, ligands, and drugs of interest. In this article, the novel developments to enhance of the performance of sensor modified with metal nanoparticles of pharmaceuticals were reviewed. A discussion of the properties of metal nanostructures and their application in drug analysis is presented. Their application as modifier agent in determining low levels of drugs in pharmaceutical dosage forms and biological samples are discussed. It has been found that the electrocatalytic effect of the electrode, sensitivity and selectivity were increased using various working electrodes modified with nano-sized metal, metal oxide and metal / metal oxide particles.