A modified pencil graphite electrode with 2-thiobarbituric acid for the efficient and cheap voltammetric sensing of 4-aminophenol in water samples and child syrup sample

Molybdenum Disulfide/Nickel-Metal Organic Framework Hybrid Nanosheets Based Disposable Electrochemical Sensor for Determination of 4-Aminophenol in Presence of Acetaminophen

The toxicity of commonly used drugs, such as acetaminophen (ACAP) and its degradation-derived metabolite of 4-aminophenol (4-AP), underscores the need to achieve an effective approach in their simultaneous electrochemical determination. Hence, the present study attempts to introduce an ultra-sensitive disposable electrochemical 4-AP and ACAP sensor based on surface modification of a screen-printed graphite electrode (SPGE) with a combination of MoS₂ nanosheets and a nickel-based metal organic framework (MoS₂/Ni-MOF/SPGE sensor). A simple hydrothermal protocol was implemented to fabricate MoS₂/Ni-MOF hybrid nanosheets, which was subsequently tested for properties using valid techniques including X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transformed infrared spectroscopy (FTIR), and N₂ adsorption-desorption isotherm. The 4-AP detection behavior on MoS₂/Ni-MOF/SPGE sensor was followed by cyclic voltammetry (CV), chronoamperometry and differential pulse voltammetry (DPV). Our experimental findings on the generated sensor confirmed a broad linear dynamic range (LDR) for 4-AP from 0.1 to 600 μM with a high sensitivity of 0.0666 μA/μM and a low limit of detection (LOD) of 0.04 μM. In addition, an analysis of real specimens such as tap water sample as well as a commercial sample (acetaminophen tablets) illuminated the successful applicability of as-developed sensor in determining ACAP and 4-AP, with an impressive recovery rate.

Emphasis on the incorporation of Tropaeolin OO dye and silver nanoparticles for voltammetric estimation of flibanserin in bulk form, tablets and human plasma

A novel electrochemical sensor based on the electro-deposition of silver nanoparticles (AgNPs) on Tropaeolin OO (poly-TO) layers over pencil graphite electrode (PGE) surface was fabricated for the first time for voltammetric determination of flibanserin (FBS); a drug enhances female sexual performance. Further characterization studies using cyclic voltammetry (CV), square wave voltammetry (SWV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were conducted. The AgNPs synergistic effect on poly-TO layers facilitates the FBS electro-oxidation in phosphate buffer solution (pH 6.0) and its determination in bulk form, tablets and in human plasma. Following ICH guidelines, validation of the proposed SWV method for FBS analysis was successfully achieved using the fabricated sensor (AgNPs@poly-TO/PGE). Under the optimal instrumental and experimental conditions, the anodic oxidation peak current was directly proportional to FBS concentration in the range from 0.1 to 8.5 μmol L^-1 with low detection and quantitation limits (0.0286 and 0.0867 μmol L^-1, respectively). High sensitivity, selectivity as well as easiness of fabrication are the main advantages of the modified sensor.

Screen-printed graphite electrode modified with Co3O4nanoparticles and 2D graphitic carbon nitride as an effective electrochemical sensor for 4-aminophenol detection

We fabricated a new electrochemical 4-aminophenol sensor based on a nanocomposite of Co₃O₄nanoparticles and graphite carbon nitride (Co₃O₄@g-C₃N₄), used for the modification of a screen-printed electrode (Co₃O₄@g-C₃N₄/SPE). The synthesized nanocomposite was characterized using field-emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction and Fourier transform-infrared (FT-IR) techniques. The electro-oxidation of 4-aminophenol in phosphate buffer solution (pH = 7.0) was investigated via cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The peak current of oxidation in the optimized conditions had a linear relationship with various 4-aminophenol contents (0.05-780.0μM) with a correlation coefficient of 0.9996 and the limit of detection (S/N = 3) of 1.5 × 10^-8M. The developed method was successful to determine 4-aminophenol in real specimens, with acceptable outcomes.

Recent Developments in Voltammetric Analysis of Pharmaceuticals Using Disposable Pencil Graphite Electrodes

The even growing production of both well-known and new derivatives with pharmaceutical action involves the need for developing facile and reliable methods for the analysis of these compounds. Among the widely used instrumental techniques, the electrochemical ones are probably the simplest and the most rapid, also having good performance characteristics. However, the key tool in electroanalysis is the working electrode. Due to the inherent electrochemical and economic advantages of the pencil graphite electrode (PGE), the interest in its applicability in the analysis of different analytes has continuously increased in recent years. Thus, this paper aims to review the scientific reports published in the last 10 years on the use of the disposable eco- and user-friendly PGEs in the electroanalysis of compounds of pharmaceutical importance in different matrices. The PGE characteristics and designs (bare or modified with various types of materials), along with their applications and performance parameters (e.g., linear range, limit of detection, and reproducibility), will be discussed, and their advantages and limitations will be critically emphasized.

Homo pair formations of thiobarbituric acid: DFT calculations and QTAIM analysis

Homo pair formations of thiobarbituric acid (TBA) were investigated in this work by performing density functional theory (DFT) calculations and the quantum theory of atoms in molecule (QTAIM) analysis. Different types of interactions including N–H . . . O, N–H . . . S, C–H . . . O, and C–H . . . S were involved in formations of five models of homo pair of TBA. In this regard, the results of energy strength and QTAIM features indicated that the model with two N–H . . . O interacting bond (D1) was placed at the highest stability and the model with one N–H . . . O and one C–H . . . S interacting bonds (D5) was placed at the lowest stability. Existence of hydrogen bond (HB) interactions in the models were confirmed based on the obtained results. As a consequence, self-interaction of TBA, as an initiator of pharmaceutical compounds production, was investigated in this work in addition to recognition of existence of different types of interactions.

Disposable Pencil Graphite Electrode for Diosmin Voltammetric Analysis

Diosmin (DIO) is a naturally occurring flavonoid with multiple beneficial effects on human health. The presence of different hydroxyl groups in diosmin structure enables its electrochemical investigation and quantification. This work presents, for the first time, diosmin voltammetric behavior and quantification on the cost-effective, disposable pencil graphite electrode (PGE). Diosmin oxidation on PGE involves two irreversible steps, generating products with reversible redox behaviors. All electrode processes are pH-dependent and predominantly adsorption-controlled. Differential pulse (DPV) and adsorptive stripping differential pulse (AdSDPV) voltammetric methods have been optimized for diosmin quantification o an H-type PGE, in 0.100 mol/L H₂SO₄. The linear ranges and limits of detection were for DPV 1.00 × 10^-6-1.00 × 10^-5 mol/L and 2.76 × 10^-7 mol/L DIO for DPV and 1.00 × 10^-7-2.50 × 10^-6 mol/L and 7.42 × 10^-8 mol/L DIO for AdSDPV, respectively. The DPV method was successfully applied for diosmin quantification in dietary supplement tablets. The percentage recovery was 99.87 ± 4.88%.