Determination of sulfonamides in milk samples by HPLC with amperometric detection using a glassy carbon electrode modified with multiwalled carbon nanotubes

A sensitive and accurate method for determining five sulfonamides based on HPLC with amperometric detection and using a glassy carbon electrode modified with multiwalled carbon nanotubes is proposed. Optimal conditions for the quantitative separation of selected sulfonamides were studied, and glassy carbon electrodes with and without modification with carbon nanotubes were systematically investigated as electrodic materials. Statistical analysis of the obtained results demonstrated that these modified electrodes achieved considerably better stability and sensitivity than the conventional unmodified ones. Detection limits were in the 1.2–6.0 ng/mL range. The usefulness of the method was demonstrated by the analysis of milk samples, taking into account the European legislation on residues in food products, following both a screening method to classify the samples and a confirmation method to provide more detailed information in the case of positive samples.     

Carbon‐Coated LiTi2(PO4)3: An Ideal Insertion Host for Lithium‐Ion and Sodium‐Ion Batteries

We report the extraordinary performance of carbon‐coated sodium super ion conductor (NASICON)‐type LiTi₂(PO₄)₃ as an ideal host matrix for reversible insertion of both Li and Na ions. The NASICON‐type compound was prepared by means of a Pechini‐type polymerizable complex method and was subsequently carbon coated. Several characterization techniques such as XRD, thermogravimetric analysis (TGA), field‐emission (FE) SEM, TEM, and Raman analysis were used to study the physicochemical properties. Both guest species underwent a two‐phase insertion mechanism during the charge/discharge process that was clearly evidenced from galvanostatic and cyclic voltammetric studies. Unlike that of Li (≈1.5 moles of Li), Na insertion exhibits better reversibility (≈1.59 moles of Na) while experiencing a slightly higher capacity fade (≈8 % higher than Li) and polarization (780 mV) than Li. However, excellent rate capability profiles were noted for Na insertion relative to its counterpart Li. Overall, the Na insertion properties were found to be superior relative to Li insertion, which makes carbon‐coated NASICON‐type LiTi₂(PO₄)₃ hosts attractive for the development of next‐generation batteries.     

Pd nanoparticles on boron doped graphene catalyst for electrochemical detection of hydrogen peroxide prepared by electroless deposition methodEI北大核心CSCD

Taking advantage of large conjugated structure and reductivity of boron-doped graphenethe palladium nanoparticles/boron-doped graphene catalyst was prepared by electroless deposition method using boron-doped graphene as reductant and stabilizer. The average size of palladium nanoparticles highly dispersed on the surface of boron-doped graphene was about 6.5 nm. The electrochemical sensor was prepared by modifying the as-formed catalyst on the surface of glassy carbon electrode. The obtained electrochemical sensor exhibited an excellent electrochemical catalytic activity for H2 O2 . It exhibited high sensitivity with the detection limit as low as 830 nmol/L and good linearity in the range of 2.5-300 μµmol/L for detection of H2 O2 . It could be utilized for the determination of H2 O2 in milk samples. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

Molecularly imprinted polymer-carbon paste electrode (MIP-CPE)-based sensors for the sensitive detection of organic and inorganic environmental pollutants: A review

The rapidly growing existence of a number of contaminants (i.e. heavy metals, dye compounds, explosives and pesticides etc.) in environment is an alarming concern not only due to their harmful impacts for the environment bur also due to their potential high risk for human health. Thus, the careful and sensitive detection of these environmental contaminants is ver crucial. Electrochemical sensors combined with molecularly imprinted polymers (MIPs) become an attractive area for environmental monitoring. Benefiting from their great features such as high chemical and physical stability, cheap preparation process, excellent selectivity, sensitivity and fast response towards the target compound/s.This review paper aims to present and highlight the latest progresses in the design and development of novel electrochemical sensor systems composed of MIPs and carbon paste electrodes (CPEs) for the sensitive detection of pollutants in environmental samples.     

Bimetallic CuCo Derived from Prussian Blue Analogue for Nonenzymatic Glucose Sensing

Bimetallic CuCo composites are prepared by calcinating copper hexacyanocobaltate precursor in N₂ atmosphere. The CuCo modified electrodes are fabricated for nonenzymatic glucose sensing in the alkaline electrolyte. The glucose can be directly electro-oxidized on the surface of the electrode catalyst mediated by the redox couples of Cu and Co. The optimal glucose sensor exhibits a high sensitivity (567 μA ⋅ mM⁻¹ ⋅ cm⁻²) in the range up to 825 μM with a detection limit of 3 μM and acceptable selectivity. The sensor can also be applied in serum samples. This work provides a facile and easily-scalable synthesis method of electrocatalysts for nonenzymatic glucose sensors.     

A Novel Carbon Nitride Nanosheets-based Electrochemical Sensor for Determination of Hydroxychloroquine in Pharmaceutical Formulation and Synthetic Urine Samples

This study introduces modified carbon paste electrodes with carbon nitride nanosheets (CNNS) and outlines their application for the determination of hydroxychloroquine sulfate (HCQ) in tablets and synthetic urine samples. CNNS were synthesized by hydrothermal route (200 °C, 10 h) using melamine and citric acid as their precursors. The carbon nitride nanosheets-based electrode (CNNS/E) presented a linear dynamic range for HCQ (LDR), ranging from 10.0 nmol l⁻¹ to 6.92 μmol l⁻¹, and detection (LOD) and quantification limits (LOQ) of 0.16 nmol l⁻¹ and 0.52 nmol l⁻¹, respectively. LOD and LOQ were calculated by the equations: LOD=3(S_d/b), and LOQ=10(S_d/b). The modified sensor presented excellent relative standard deviations for parameters such as repeatability (2.39 % and 1.87 %) and reproducibility (3.22 % and 2.32 %) in HCQ oxidation peaks (1 and 2). The CNNS/E has not shown significant variations in its anodic signal intensity in the presence of some organic and inorganic substances. It is worth bearing in mind that CNNS/E can be easily manufactured and the sensor has the lowest HCQ detection limits reported so far. The proposed sensor was successfully applied for HCQ determination in tablets and synthetic urine, showing good recovery values and an error of 0.60 % about comparative method in tablet samples, assuring the quality of the method.     

Analytical Modelling of Electron-coupled Ion Transfers with Immobilized vs Soluble Redox Transducer at Thick Film-modified Electrodes

Analytical theoretical solutions are deduced for the current-potential response, concentration profiles and interfacial potentials of electron-coupled ion transfers in the cyclic voltammetry with thick film-modified electrodes. The theory covers a wide variety of possible situations, namely, the redox transducer can be either immobilized on the working electrode or freely diffusing in the organic film, and the ion transfer can be either simple or complicated by homogeneous chemical processes. A comparative and comprehensive study of each case is performed, establishing the key parameters that define the behaviour of the system, as well as guidelines to analyse its electrochemical signal.     

Probing the Local Reaction Environment During High Turnover Carbon Dioxide Reduction with Ag-Based Gas Diffusion Electrodes

Discerning the influence of electrochemical reactions on the electrode microenvironment is an unavoidable topic for electrochemical reactions that involve the production of OH⁻ and the consumption of water. That is particularly true for the carbon dioxide reduction reaction (CO₂RR), which together with the competing hydrogen evolution reaction (HER) exert changes in the local OH⁻ and H₂O activity that in turn can possibly affect activity, stability, and selectivity of the CO₂RR. We determine the local OH⁻ and H₂O activity in close proximity to a CO₂-converting Ag-based gas diffusion electrode (GDE) with product analysis using gas chromatography. A Pt nanosensor is positioned in the vicinity of the working GDE using shear-force-based scanning electrochemical microscopy (SECM) approach curves, which allows monitoring changes invoked by reactions proceeding within an otherwise inaccessible porous GDE by potentiodynamic measurements at the Pt-tip nanosensor. We show that high turnover HER/CO₂RR at a GDE lead to modulations of the alkalinity of the local electrolyte, that resemble a 16 m KOH solution, variations that are in turn linked to the reaction selectivity.     

Thin-film multi-layer capacitors using Bi2Mg2/3Nb4/3O7 (BMNO) pyrochlore thin films via radio-frequency sputtering

Thin-film multi-layer ceramic capacitors (MLCCs) were prepared using high-dielectric constant Bi₂Mg_2/3Nb_4/3O₇ thin-films deposited at room temperature via radio-frequency magnetron sputtering. The multi-layer capacitors, in sizes 0402, 0603 and 1005, were well equipped with both inner and outer Cu electrodes. The capacitances of the bi-layer capacitors were twice that of the single-layer version in sizes 0402, 0603, and 1005. The 200 nm-thick Bi₂Mg_2/3Nb_4/3O₇ thin-films would be suitable for thin-film multi-layer capacitor applications.     

Multiplexed Determination of Amino‐Terminal Pro‐B‐Type Natriuretic Peptide and C‐Reactive Protein Cardiac Biomarkers in Human Serum at a Disposable Electrochemical Magnetoimmunosensor

A rapid magnetoimmunosensor for the simultaneous determination of two cardiac biomarkers, amino‐terminal pro‐B‐type natriuretic peptide (NT‐proBNP) and C‐reactive protein (CRP), in human serum is described. Specific capture antibodies were covalently immobilized onto carboxylic acid‐modified magnetic beads. The quantification of NT‐proBNP and CRP was performed by using indirect competitive and sandwich configurations, respectively, and horseradish peroxidase‐labeled tracers. The use of dual screen‐printed carbon electrodes allowed the achievement of simultaneous independent amperometric readout for each cardiac biomarker. The developed methodology showed very low limits of detection (0.47 ng mL^?1). An international standard for CRP serum spiked with NT‐proBNP was analyzed to evaluate the usefulness of the magnetoimmunosensor.