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In this work, the EC' mechanism involving ascorbate (AA−) and the oxidized form of ferrocenemethanol (FcMeOH) was explored as an analytical strategy to monitor AA− at low concentration levels. The feasibility of this approach was investigated at different mass transport regimes utilizing macro‐ (glassy carbon) and ultramicroelectrodes (5 μm radius carbon disk). Cyclic voltammograms (CV) were recorded in acetate buffer solution (pH 3.7) using a glassy carbon electrode, and an expressive increase in the anodic peak current (and decrease in the cathodic peak) was noticed in the CV in a solution containing both FcMeOH and ascorbate, confirming the presence of an electrocatalytic process (EC'). The current increase was more pronounced when the reactants and products were confined in a thin solution layer, which was created by approaching an ultramicroelectrode close to an insulator surface. At optimized experimental conditions, a correlation between ascorbate concentration and the steady‐state current measured at the ultramicroelectrode was established, allowing the development of an analytical method for ascorbate detection in the micromolar range. The proposed approach was used to quantify ascorbate in a commercial juice sample. [ABSTRACT FROM AUTHOR]

The fabrication of a gold microelectrode modified with iridium oxide film (IrOx) and its use as tip with a dual function in SECM experiments is reported. The defective structure of the coating onto the microelectrode surface was used as strategy to combine the advantages of both amperometric (for current-distance determination) and potentiometric (for pH sensing) SECM operation modes. Approach curves, using oxygen and hexaammineruthenium(III) as redox mediators, were obtained without significant loss of the performance and reproducibility of the potentiometric pH response. This allowed the precise positioning of the proposed tip above a substrate in SECM experiments and, subsequently, to monitor pH at the substrate surface. The IrOx modified microelectrode was applied successfully in SECM experiments involving the local proton consumption during the nitrate reduction at a copper cathode surface. [ABSTRACT FROM AUTHOR]

The selective amperometric determination of paracetamol in pharmaceutical formulations containing ascorbate was achieved by removing the interfering species in the diffusion layer created between a platinum substrate and a disc microelectrode in a Scanning Electrochemical Microscopy (SECM) configuration, while the target analyte was kept unconsumed. After complete depletion of ascorbate, paracetamol was detected at the SECM tip in a free-interference solution zone. The influence of the substrate potential and the gap distance on the efficiency of ascorbate removal was systematically examined. The effectiveness of the device towards the determination of paracetamol in pharmaceutical samples was evaluated and under optimal conditions the results obtained agreed well with the labeled value. [ABSTRACT FROM AUTHOR]

Abstract: The cathodic reduction of nitrate at copper electrodes was investigated by using scanning electrochemical microscopy (SECM) in the stripping-mode SECM (SM-SECM). This electrochemical process is facilitated at surfaces activated by a potential protocol involving anodic dissolution and subsequent reduction of copper cations, which causes an increase in the surface area. In the presence of chloride, a much more significant current enhancement was noticed, and a mechanism based on the formation of CuCl was proposed to explain the increased rate of nitrate reduction at this experimental condition. [Copyright &y& Elsevier]

When the tooth is exposed to acidic environments, an irreversible loss of dental hard tissue occurs in a process called dental erosion. In this work, the scanning electrochemical microscopy (SECM) was used to probe the consumption of protons at the vicinity of a tooth surface with a platinum microelectrode fixed at -0.5 (V) versus Ag/AgCl/KCl(sat). SECM approach curves were recorded to assess the extent of diffusion in the solution close to the tooth substrate. SECM images clearly demonstrated that the acid erosion process is very fast at solution pH values in the range between 3 and 4. [ABSTRACT FROM AUTHOR]

The participation of cations in redox reactions of manganese oxides provides an opportunity for development of chemical sensors for non-electroactive ions. A sensor based on a nanostructured hollandite-type manganese oxide was investigated for voltammetric detection of potassium ions. The detection is based on the measurement of anodic current generated by oxidation of Mn(III) to Mn(IV) at the surface of the electrode and the subsequent extraction of the potassium ions into the hollandite structure. In this work, an amperometric procedure at an operating potential of 0.80 V (versus SCE) is exploited for amperometric monitoring. The current signals are linearly proportional to potassium ion concentration in the range 4.97 × 10-5 to 9.05 × 10-4 mol L-1, with a correlation coefficient of 0.9997. [ABSTRACT FROM AUTHOR]

We review the methods of vesicle impact electrochemical cytometry, intracellular impact electrochemical cytometry, and single cell amperometry and their application to measuring the storage of neurotransmitters in cellular vesicles. We provide protocols to measure vesicle content, the release of catecholamines, and from there the fraction of transmitter released in each exocytosis event. The focus here has been a combination of methods to evaluate factors related to neuronal function at the cellular level and implications in, for example, cognition., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Peroxiredoxins (Prx) are important proteins involved in hydroperoxide degradation and are related to virulence in several pathogens, including Aspergillus fumigatus. In this work, in vivo studies on the degradation of hydrogen peroxide (H 2 O 2 ) in the microenvironment of A. fumigatus fungus were performed by using an integrated Pt microelectrode. Three A. fumigatus strains were used to confirm the role of the cytosolic protein Prx1 in the defense mechanism of this microorganism: a wild-type strain, capable to expressing the protein Prx1; a Δprx strain, whose gene prx1 was removed; and a genetically complemented Δprx1::prx1 + strain generated from the Δprx1 and in which the gene prx1 was reintroduced. The fabricated microelectrode was shown to be a reliable inert probe tip for in situ and real-time measurements of H 2 O 2 in such microenvironments, with potential applications in investigations involving the mechanism of oxidative stress.

A novel approach of using a gold disc microelectrode to analyze sweat samples for copper ions by anodic square wave stripping voltammetry (SW stripping voltammetry) is described. Sweat was collected from the lower back of four subjects after physical exercise and the sample volume required for the determinations was 100 μL. Under the optimized conditions, the calibration plot was linear over the range 1-100 μmol L(-1) Cu(II) with a limit of detection of 0.25 μmol L(-1). The precision was evaluated by carrying out five replicate measurements in a 1 μmol L(-1) Cu(II) solution and the standard deviation was found to be 1.5%. Measurements were performed by inserting the microelectrode into sweat drops and Cu(II) concentrations in the analyzed samples ranged from 0.9 to 28 μmol L(-1). Values obtained by the proposed voltammetric method agreed well with those found using graphite furnace atomic absorption spectroscopy (GFAAS)., (Copyright © 2010 Elsevier B.V. All rights reserved.)