Electrochemical Determination of Famotidine in Real Samples Using rGO/Cu2O Nanocomposite Modified Carbon Paste Electrode

Here, we developed a sensitive electrochemical sensor for famotidine (FAT) using Cu2O nanoparticles and reduced graphene oxide (rGO) as a sensing platform. The Cu2O nanoparticles and rGO were synthesized through a simple process and characterized by versatile analytical methods. The prepared Cu2O nanoparticles and rGO were taken to modify the carbon paste electrode (Cu2O/rGO/CPE) and developed for the electrochemical analysis of the FAT at pH 6.0. Cu2O/rGO/CPE showed superior electrocatalytic activity for detecting FAT, attributed to the high surface area of rGO and the electrocatalytic properties of Cu2O nanoparticles. The designed FAT sensor exhibited two linear ranges from 0.1-3 µM and 3-50 µM with a detection limit of 0.08 µM (S/N=3) using a differential pulse voltammetry. The proposed sensor also showed a repeatable and stable response over one month with negligible interference from usual organic and inorganic species. The sensor was also validated measuring FAT in real samples (urine, serum and pharmaceutical tablet) with good recovery values from 99.6 to 110.9%.

Two new bis(pyridine)-bis(amide)-based copper(II) coordination compounds for the electrochemical detection of trace Cr(VI) and efficient electrocatalytic oxygen evolution

Two new metal-organic compounds (MOCs) [Cu(L)0.5(3-nba)2] (1) and [Cu(L)(2,5-tdc)] (2) have been hydrothermally synthesized by employing the ligand N,N′-di(3-pyridyl)adipoamide (L) and two carboxylic acids (3-Hnba = 3-nitrobenzoic acid, 2,5-H2tdc = 2,5-thiophenedicarboxylic acid) as ligands. Compound 1 displays a metal-organic chain-like structure formed by the {Cu2(3-nba)4} double-paddle wheel units and the µ 2-bridging L ligands. The adjacent polymeric chains form a supramolecular layered structure through hydrogen bonding. Compound 2 shows a 3D metal-organic polymeric framework derived from Cu-L layers and µ 2-bridging 2,5-tdc ligands, which presents a 3,5-connected {4.62}{4.66.83} topology. The electrochemical and electrocatalytic behavior of the two compounds has been studied in detail. Carbon paste working electrodes modified with compounds 1 and 2 can be used as highly selective sensors for detecting traces Cr(VI). Both electrodes show also electrocatalytic performance in oxygen evolution reactions (OERs).

Cardanol-Based Salophen-Modified Electrode for Analysing Nitric Oxide Bioavailability under Nitrosative Stress Conditions

High levels of nitric oxide (NO) can signal nitrosative stress, but its analysis is challenging considering the high reactivity, short half-life and transient behavior of this target molecule in biological milieu. In this work, a cardanol-based salophen-modified carbon paste electrode (CDN-salophen/MCPE) was developed and successfully applied to assess NO bioavailability in blood plasma of mice under induced stress. The results revealed that the modifier improved the device performance in terms of signal-to-noise ratio, charge-transport and fouling resistance. NO reactivity on CDN-salophen/MCPE was higher in 0.1 mol L‒1 H2SO4, and the resulting redox process involves adsorption steps that control the reaction kinetics. Monitoring molecule oxidation by square-wave voltammetry (100 s−1 frequency, 30 mV amplitude, 2 mV scan increment, after electrode preconditioning at 0.9 V for 15 s for analyte accumulation), it was possible to identify and quantify NO with great sensitivity (detection and quantification limit < 0.1 µmol L‒1) and low data variance (RSD ≤ 9.4% for repeatability and reproducibility tests), through a simple, fast and reliable electroanalytical protocol. The robustness acquired with CDN-salophen/MCPE allowed to detect changes in NO content in blood plasma during nitrosative stress, proving its efficiency for research on this subject.

Design and construction of an electrochemical sensor for the determination of cerium(iii) ions in petroleum water samples based on a Schiff base-carbon nanotube as an ionophore

A carbon paste and screen-printed sensor for Ce(iii)-selective determination were prepared using a 2,6-pyridine dicarbomethine-triethylene tetraamine macrocyclic Schiff base ligand and multi-walled carbon nanotubes as good sensing materials.

Determination of moxifloxacin hydrochloride in AVELOX pharmacological formulations using modified potentiometer sensors

Three different carbon paste (CP), silk-screen (SP) and poly (vinyl chloride) (PVC) modified electrodes were obtained to verify the reliability of AVELOX, the generic name of which is Moxifloxacin HCl (AV-MOXH). The sensing membranes were containing AVELOX ion associated complexes with sodium tetraphenylborate (NaTPB), phosphomolybdic acid (PMA), phosphotungstic acid (PTA), and ammonium reineckate (RN) as electroactive materials. All three electrodes gave fast, viable, and near-Nernstian linear responses over a relative wide concentration range that ranged from 1.010-6 to 1.010-2 mol / L AV-MOXH at 25° C with a monovalent cationic decrease. The sensors demonstrated a good discernment of AV-MOXH from numerous inorganic and organic compounds such as glucose, sucrose, Na+, Ca+, etc. Additionally, the isothermal coefficients along with selectivity coefficients were calculated. The modified Screen Printed Electrode sensor appeared to be highly sensitive for the determination of AV-MOXH. The electrode response was observed in pH range 2--6 for ISPE electrodes and IPVC electrodes and 3--7 for ICPE electrodes under various temperature conditions. The short response time, lifetime validity, recovery, and all the methods of validation such as limit of detection and limit of quantification were estimated. The potentiometric method turned out to be suitable for determining AV-MOXH in pharmacological formulations, and the findings obtained are comparable to the “HPLC official method” in terms of the agreement. As a result, the postulated potentiometric approach was verified in accordance with IUPAC guidelines.

Highly sensitive voltammetric determination of NADH based on N-CQDs decorated SnO2/ionic liquid/carbon paste electrode

A highly sensitive and selective modified electrode was successfully developed for the monitoring of nicotinamide adenine dinucleotide (NADH) in the presence of folic acid. In this regard, a carbon paste electrode (CPE) was functionalized by the nitrogen-doped carbon quantum dots/tin oxide (N-CQDs/SnO2) nanocomposite and 1-butyl-2,3-dimethyl imidazolium hexafluorophosphate ([C4DMIM][PF6]) ionic liquid (IL). The structure and surface morphology of the nanocomposite were characterized by various methods, including field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD). The modified electrode displayed powerful and long-lasting electron mediating activity, with well-separated NADH and folic acid oxidation peaks. The sensing response of the developed [C4DMIM][PF6]/N-CQDs/SnO2/CPE platform was evaluated by determining NADH via the voltammetric technique under the optimized operating conditions. The current peaks of the square wave voltammograms of NADH and folic acid increased linearly with enhancing its concentrations within the ranges of 0.003 - 275 µM NADH and 0.4 - 380 µM folic acid. The detection limits for NADH and folic acid were obtained at 0.8 nM and 0.1 µM, respectively. Interference species such as glucose, urea, tryptophan, glycine, methionine, and vitamin B12 had no influence on the ability of the fabricated modified electrode to detect the target species. The low detection limit, high sensitivity, excellent selectivity, superior stability, and cost-effectiveness made it suitable for the quantification of NADH in the real biological samples with the recovery percent values in the range of 97.5 - 103%.

Electrodes for Paracetamol Sensing Modified with Bismuth Oxide and Oxynitrate Heterostructures: An Experimental and Computational Study

In this work, novel platforms for paracetamol sensing were developed by the deposition of Bi2O3, Bi5O7NO3 and their heterostructures onto screen-printed carbon-paste electrodes. An easy and scalable solid state synthesis route was employed, and by setting the calcination temperatures at 500 °C and 525 °C we induced the formation of heterostructures of Bi2O3 and Bi5O7NO3. Cyclic voltammetry measurements highlighted that the heterostructure produced at 500 °C provided a significant enhancement in performance compared to the monophases of Bi2O and Bi5O7NO3, respectively. That heterostructure showed a mean peak-to-peak separation Ep of 411 mV and a sensitivity increment of up to 70% compared to bare electrodes. A computational study was also performed in order to evaluate the geometrical and kinetic parameters of representative clusters of bismuth oxide and subnitrate when they interact with paracetamol.

DNA-Based Electrodes and Computational Approaches on the Intercalation Study of Antitumoral Drugs

The binding between anticancer drugs and double-stranded DNA (dsDNA) is a key issue to understand their mechanism of action, and many chemical methods have been explored on this task. Molecular docking techniques successfully predict the affinity of small molecules into the DNA binding sites. In turn, various DNA-targeted drugs are electroactive; in this regard, their electrochemical behavior may change according to the nature and strength of interaction with DNA. A carbon paste electrode (CPE) modified with calf thymus ds-DNA (CPDE) and computational methods were used to evaluate the drug–DNA intercalation of doxorubicin (DOX), daunorubicin (DAU), idarubicin (IDA), dacarbazine (DAR), mitoxantrone (MIT), and methotrexate (MTX), aiming to evaluate eventual correlations. CPE and CPDE were immersed in pH 7 0.1 mM solutions of each drug with different incubation times. As expected, the CPDE response for all DNA-targeted drugs was higher than that of CPE, evidencing the drug–DNA interaction. A peak current increase of up to 10-fold was observed; the lowest increase was seen for MTX, and the highest increase for MIT. Although this increase in the sensitivity is certainly tied to preconcentration effects of DNA, the data did not agree entirely with docking studies, evidencing the participation of other factors, such as viscosity, interfacial electrostatic interactions, and coefficient of diffusion.