Voltammetric measurement of entacapone in the presence of other medicines against Parkinson's disease by a screen-printed electrode modified with sulfur-tin oxide nanoparticles.

A screen-printed electrode (SPE) is described modified with sulfur-tin oxide nanoparticles (S@SnO2NP) for the determination of entacapone (ENT) in the presence of other medicines against Parkinson's disease (PD). The S@SnO2NP was synthesized through the hydrothermal method and used in the modification of the SPE. The smart utilization of the S@SnO2NP and the SPE provided excellent properties such as high surface area and current density amplification by embedding an efficient sensing interface for highly selective electrochemical measurement. Under optimized experimental conditions, the anodic peak current related to the ENT oxidation onto the sensor surface at 0.46 V presented a linear response towards different ENT concentration sin the range 100 nM to 75 µM. The limit of detection (LOD) and electrochemical sensitivity were estimated to be 0.010 µM and 2.27 µA·µM-1·cm-2, respectively. The applicability of the sensor was evaluated during ENT determination in the presence of other conventional medicines againts, including levodopa (LD), carbidopa (CD), and pramipexole (PPX). The results of the analysis of human urine and pharmaceutical formulation as real samples using the developed sensor were in good agreement withre sults of high-performance liquid chromatography (HPLC) as a standard method. These findings demonstrated that the strategy based on the SPE is a cost-effective platform creating a promising candidate for practical determination of ENT in routine clinical testing.Graphical abstract.

Electrochemical Oxidation and Determination of Antiviral Drug Acyclovir by Modified Carbon Paste Electrode With Magnetic CdO Nanoparticles.

With the development of nanomaterials in electrochemical sensors, the use of nanostructures to modify the electrode surface has been shown to improve the kinetics of the electron transfer process. In this study, a sensor was developed for the electrochemical determination of Acyclovir (ACV) based on the modified carbon paste electrode (CPE) by CdO/Fe3O4. The magnetic CdO nanoparticles characterization was studied by energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). To study of the modified CPE surface morphology, scanning electron microscopy (SEM) was used. At the optimal conditions, a noteworthy enhancement in the electrochemical behavior of ACV was observed at the surface of the modified CPE compared to the unmodified CPE. A detection limit of 300 nM and a linear range of 1-100 µM were obtained for the quantitative monitoring of ACV at the modified CPE surface using differential pulse voltammetry (DPV) in phosphate buffer. The RSD% (relative standard deviation) of the electrode response was <4.3% indicating the development of a high precision method. Also, satisfactory results were obtained in the determination of ACV with the modified electrode in tablet, blood serum, and urine samples with a satisfactory relative recovery (RR%) in the range of 94.0-104.4%.

A glassy carbon electrode modified with carbon nanoonions for electrochemical determination of fentanyl.

Fentanyl is a pain reliever stronger and deadlier than heroin. This lethal drug has killed many people in different countries recently. Due to the importance of the diagnosis of this drug, a fentanyl electrochemical sensor is developed based on a glassy carbon electrode (GCE) modified with the carbon nanoonions (CNOs) in this study. Accordingly, the electrochemical studies indicated the sensor is capable of the voltammetric determination of traces of fentanyl at a working potential of 0.85 (vs. Ag/AgCl). To obtain the great efficiency of the sensor some experimental factors such as time, the potential of accumulation and pH value of the electrolyte were optimized. The results illustrated a reduction and two oxidation peaks for fentanyl in phosphate buffer (PB) with pH = 7.0 under a probable mechanism of electrochemical-chemical-electrochemical (ECE). The differential pulse voltammetry (DPV) currents related to the fentanyl detection were linear with an increase of fentanyl concentrations in a linear range between 1 µM to 60 µM with a detection limit (LOD) of 300 nM. Furthermore, the values of the diffusion coefficient (D), transfer coefficient (α) and catalytic constant rate (kcat) were calculated to be 2.76 × 10-6 cm2 s-1, 0.54 and 1.76 × 104 M-1 s-1, respectively. These satisfactory results may be attributed to utilizing the CNOs in the electrode modification process due to some of its admirable characterizations of this nanostructure including high surface area, excellent electrical conductivity and good electrocatalytic activity. Consequently, these finding points the achieving a simple sensing system to measure of the fentanyl as an important drug from the judicial perspective might be a dream coming true soon.

Carbon paste electrodes modified with SnO2/CuS, SnO2/SnS and Cu@SnO2/SnS nanocomposites as voltammetric sensors for paracetamol and hydroquinone.

Several nanocomposites of tin oxide with CuS, SnS or Cu@SnS were prepared and used to modify carbon paste electrodes (CPEs). The structure and morphology of the materials were studied by XRD and SEM techniques. Cyclic voltammetry and electrochemical impedance spectroscopy were applied to investigate their electrochemical properties. The modified CPEs exhibit superior voltammetric response to paracetamol (PAT) and hydroquinone (HQ) (when compared to a bare CPE) in terms of onset oxidation potential and current density. The CPE modified with SnO2/SnS was applied to voltammetric determination of PAT (at a working potential of 0.55 V versus Ag/AgCl and with a 0.06 µM detection limit), and of HQ (at 0.39 V versus Ag/AgCl with a 0.2 µM detection limit). The voltammetric responses were linear in the range from 1.0 to 36 µM for PAT and from 1.0 to 85 µM for HQ. Graphical abstract Carbon paste electrodes were modified with several new tin oxide and sulfidic nanocomposites and then exhibit superior properties in terms of detection of paracetamol and hydroquinone.