Redox Potential Measurement in Aqueous Solutions and Biological Media

Goldin, Mark M.; Volkov, Alexander G.; Khubutiya, M. Sh.; Колесников, В. А.; Blanchard, G. J.; Евсеев, А. К.; Teselkin, Yury O.; Davydov, B. V.

doi:10.1149/1.2928905

Cited by 9 publications

(10 citation statements)

References 16 publications

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“…OCP measurements have shown usefulness in the measurement of oxidative stress, evaluation of the overall redox state of complex solutions, and chemical sensing. 12,[20][21][22][23][24][25] In an OCP measurement, no net current flows as the cathodic and anodic processes are balanced such that the sum of the anodic and cathodic currents are zero. 1 When both forms of a redox couple are present, the solution is said to be poised and the potential can be theoretically calculated via the Nernst equation.…”

mentioning

confidence: 99%

The Measurement of Mixed Potentials Using Platinum Decorated Nanoporous Gold Electrodes

Islam¹,

Branigan²,

Ullah³

et al. 2022

J. Electrochem. Soc.

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Potentiometric redox sensing in solutions containing multiple redox molecules was evaluated using in-house constructed nanoporous gold (NPG)-platinum (Pt) and unmodified NPG electrodes. The NPG-Pt electrode was fabricated by electrodepositing Pt into the nanoporous framework of a chemically dealloyed NPG electrode. By varying the concentration of the Pt salt and the electrodeposition time, different amounts of Pt were introduced. Characterization by SEM shows the pore morphology doesn’t change with the addition of Pt and XPS indicates the electrodes contain ∼2.5–24 wt% Pt. Open-circuit potential (OCP) measurements in buffer and solutions containing ascorbic acid, cysteine, and/or uric acid show that the OCP shifts positive with the addition of Pt. These results are explained by an increase in the rate of the oxygen reduction reaction with the addition of Pt. The overall shape of the potentiometric titration curves generated from solutions containing one or more bioreagents is also highly dependent on the amount of Pt in the nanoporous electrode. Furthermore, the generation of OCP vs Log [bioreagent] from the results of the potentiometric experiments shows an ∼2-fold increase in sensitivity can result with the addition of Pt. These results indicate the promise that these electrodes have in potentiometric redox sensing.

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mentioning

confidence: 99%

The Measurement of Mixed Potentials Using Platinum Decorated Nanoporous Gold Electrodes

Islam¹,

Branigan²,

Ullah³

et al. 2022

J. Electrochem. Soc.

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“…2,4,5 Such redox measurements have been used to characterize the redox state of solutions with a complex matrix including milk, cheese, sludge, water and biological systems. [6][7][8][9][10][11][12][13] An important and often neglected factor in the measurement of redox potential is the nature of the electrode surface, particularly the presence and extent of modification, contamination, and fouling/poisoning, as these variables can significantly reduce electron exchange rates. Natural systems, which often contain many redox species with varying electron exchange rates, are particularly challenging to study.…”

mentioning

confidence: 99%

Potentiometric Measurements in Biofouling Solutions: Comparison of Nanoporous Gold to Planar Gold

Farghaly

Lam

Freeman

et al. 2015

J. Electrochem. Soc.

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Potentiometric redox measurements were made in solutions of increasing biological complexity starting with buffer solutions containing either potassium ferri/ferrocyanide or ascorbic acid and finishing with plasma and blood. When the concentration of ferri/ferrocyanide was high (∼0.2 mM), both biofouled planar and nanoporous gold electrodes gave Nernstian slopes of 55-59 mV. However, at or below a critical concentration (≤ 0.1 mM), ∼20% loss in sensitivity was observed at planar gold in contrast to nanoporous gold where Nernstian behavior was retained. For ascorbic acid, a Nernst slope of −41 mV was observed at biofouled nanoporous gold electrodes. In contrast, biofouled planar gold electrodes failed to give any potentiometric redox response. At all concentrations studied, cyclic voltammetric measurements on biofouled electrodes revealed significant impairment of faradaic electroactivity at planar gold electrodes while no impairment was shown at nanoporous gold. These results indicate that nanoporous gold is an ideal electrode material to use when making both potentiometric and cyclic voltammetric measurements, particularly in complex solutions containing relatively low concentrations of redox molecules. As proof of concept, the redox potential of plasma and blood has been measured using nanoporous and planar gold electrodes and their values compared. Potentiometry is a technologically simple and inexpensive approach to obtain important information about the redox state of a system and/or the concentration of ions in solution.1,2 The measurement itself is simple in that all that is needed is a high impedance voltammeter, a stable reference electrode, and a suitable indicating electrode. In contrast to voltammetric measurements, no current flows, and the concentration of the redox species in solution does not change nor does the indicating electrode surface become altered as a potential is not applied. Likely the most popular potentiometric measurement is the measurement of pH using an ion-selective electrode that incorporates a thin membrane responsive to the activity of protons in solution. 3For the work described herein, the indicating electrode is an inert metallic redox electrode that is purposely designed to be nonselective and will 'ideally' respond to all redox active species in solution able to exchange electrons with the metallic surface.1,2 When the indicator electrode is immersed in solution, it will equilibrate electrochemically with the dissolved redox species and a potential will develop at its surface. The measured potential is governed by factors such as (1) the redox species present, (2) their concentrations (activities), and (3) the rate of electron exchange with the electrode.2,4,5 Such redox measurements have been used to characterize the redox state of solutions with a complex matrix including milk, cheese, sludge, water and biological systems. [6][7][8][9][10][11][12][13] An important and often neglected factor in the measurement of redox potential is the nature of the electrode surface, pa...

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“…in solution. In this case, more than one redox process can define the chemical potential of the solution and a mixed potential develops . Open circuit potential measurements confirm the change in the chemical potential of solution in the vicinity of the anode during electrochemical water or Cl − oxidation (see Supporting Information for details).…”

Section: Resultsmentioning

confidence: 77%

Effect of Chloride Oxidation on Local Electric Fields in Microelectrochemical Systems

2019

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We recently reported that electrochemical oxidation of Cl− to neutral Cl2 decreases solution conductivity, thereby yielding a local electric field gradient. Here, we report detailed experimental results and simulations indicating that the situation is more complex than we originally thought. The key new findings are twofold. First, once generated, Cl2 rapidly reacts with water to form ionic species that increase, rather than decrease, solution conductivity near the anode. Second, the electrochemical potential gradient measured in the vicinity of the anode during Cl− oxidation is dominated by differences in the chemical potential, rather than the electrical potential, of the solution. These findings clarify the electrochemical and chemical processes previously reported to enable desalination via faradaic Cl− oxidation.

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Redox Potential Measurement in Aqueous Solutions and Biological Media

Cited by 9 publications

References 16 publications

The Measurement of Mixed Potentials Using Platinum Decorated Nanoporous Gold Electrodes

The Measurement of Mixed Potentials Using Platinum Decorated Nanoporous Gold Electrodes

Potentiometric Measurements in Biofouling Solutions: Comparison of Nanoporous Gold to Planar Gold

Effect of Chloride Oxidation on Local Electric Fields in Microelectrochemical Systems

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