WordNet

existing in possibility; "a potential problem"; "possible uses of nuclear power" (同)possible
the inherent capacity for coming into being (同)potentiality, potency
of or involving electrochemistry

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可能性のある,潜在的な / 可能性,潜在力 / 電位

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/10/20 03:30:39」(JST)

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In electrochemistry, the electrochemical potential, , sometimes abbreviated to ECP, is a thermodynamic measure that combines the concepts of energy stored in the form of chemical potential and electrostatics. Electrochemical potential is expressed in the unit of J/mol.

Introduction

Each chemical species (for example, "water molecules", "sodium ions", "electrons", etc.) has an electrochemical potential (a quantity with units of energy) at any given location, which represents how easy or difficult it is to add more of that species to that location. If possible, a species will try to move from areas with higher electrochemical potential to areas with lower electrochemical potential; in equilibrium, the electrochemical potential will be constant everywhere for each species (it may have a different value for different species). For example, if a glass of water has sodium ions (Na⁺) dissolved uniformly in it, and an electric field is applied across the water, then the sodium ions will tend to get pulled by the electric field towards one side. We say the ions have electric potential energy, and are moving to lower their potential energy. Likewise, if a glass of water has a lot of dissolved sugar on one side and none on the other side, each sugar molecule will randomly diffuse around the water, until there is equal concentration of sugar everywhere. We say that the sugar molecules have a "chemical potential," which is higher in the high-concentration areas, and the molecules move to lower their chemical potential. These two examples show that an electrical potential and a chemical potential can both give the same result: A redistribution of the chemical species. Therefore it makes sense to combine them into a single "potential", the electrochemical potential, which can directly give the net redistribution taking both into account.

It is (in principle) easy to measure whether or not two regions (for example, two glasses of water) have the same electrochemical potential for a certain chemical species (for example, a solute molecule): Allow the species to freely move back and forth between the two regions (for example, connect them with a semi-permeable membrane that lets only that species through). If the chemical potential is the same in the two regions, the species will occasionally move back and forth between the two regions, but on average there is just as much movement in one direction as the other, and there is zero net migration (this is called "diffusive equilibrium"). If the chemical potentials of the two regions are different, more molecules will move to the lower chemical potential than the other direction.

Moreover, when there is not diffusive equilibrium, i.e., when there is a tendency for molecules to diffuse from one region to another, then there is a certain free energy released by each net-diffusing molecule. This energy, which can sometimes be harnessed (a simple example is a concentration cell), and the free-energy per molecule is exactly equal to the electrochemical potential difference between the two regions.

Conflicting terminologies

Definition and usage

In generic terms, electrochemical potential is the mechanical work done in bringing 1 mole of an ion from a standard state to a specified concentration and electrical potential. According to the IUPAC definition,^[4] it is the partial molar Gibbs energy of the substance at the specified electric potential, where the substance is in a specified phase. Electrochemical potential can be expressed as

,

where:

is the electrochemical potential of species i, J/mol
is the chemical potential of the species i, J/mol
is the valency (charge) of the ion i, dimensionless
is Faraday's Constant, C/mol
is the local electrostatic potential, V.

In the special case of an uncharged atom, = 0 and so .

Electrochemical potential is important in biological processes that involve molecular diffusion across membranes, in electroanalytical chemistry, and industrial applications such as batteries and fuel cells. It represents one of the many interchangeable forms of potential energy through which energy may be conserved.

In cell membranes, the electrochemical potential is the sum of the chemical potential and the membrane potential.

Incorrect usage

The term electrochemical potential is sometimes used to mean an electrode potential (either of a corroding electrode, an electrode with a non-zero net reaction or current, or an electrode at equilibrium). This particular usage can lead to confusion. A measured electrode potential does not equal the change of the electrochemical potential (see Galvani potential). Therefore, the recent literature usually explains the abbreviation ECP as "electrochemical corrosion potential". For an electrode at equilibrium, the phrase equilibrium or reversible potential of the electrode is used.

References

^ See, for example, Electrochemical Methods by Bard and Faulkner, 2nd edition, Section 2.2.4(a),4-5.
^ See, for example, Solid State Physics by Ashcroft and Mermin, page 593.
^ See, for example, Introduction to solid-state theory by Otfried Madelung page 198
^ IUPAC Gold Book, http://goldbook.iupac.org/E01945.html

External links

Electrochemical potential - lecture notes from University of Illinois at Urbana-Champaign

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English Journal

Characteristics of compounds in hops using cyclic voltammetry, UV-VIS, FTIR and GC-MS analysis.

Masek A1, Chrzescijanska E2, Kosmalska A3, Zaborski M3.Author information 1Technical University of Lodz, Institute of Polymer and Dye Technology, Faculty of Chemistry, ul Stefanowskiego 12/16, 90-924 Lodz, Poland. Electronic address: anna.masek@p.lodz.pl.2Technical University of Lodz, Institute of General and Ecological Chemistry, Faculty of Chemistry, ul Zeromskiego 116, 90-924 Lodz, Poland.3Technical University of Lodz, Institute of Polymer and Dye Technology, Faculty of Chemistry, ul Stefanowskiego 12/16, 90-924 Lodz, Poland.AbstractThe article presents the antioxidant properties of the extracts of hop EI and EII, by the electrochemical methods on a platinum electrode and comparative analysis of the composition of the extracts of hops using UV-VIS, FTIR and GC-MS methods. The hops extract EI, was obtained from the waste of the hops cone. The hops extract EII, was obtained from the hops cone itself. Hops contain a wide range of polyphenolic compounds with antioxidant properties divided in various chemical classes. Flavonoids and other polyphenolic compounds contained in hops show antioxidant capacity because of the presence of hydroxyl groups in various configurations and numbers within their molecules. The electrochemical properties and antioxidant capacity of hop samples were determined to select the most effective antioxidant. Based on the cyclic and pulse voltammograms, it was observed that hop extract EI contains polyphenols that are oxidised at a less positive potential than extract EII, i.e., it shows better antioxidant capacity. From the analysis of the UV-VIS and FTIR spectra and the GC-MS analysis, it was observed that extract EI contains less phenyl compounds than EII. In addition to flavonoids, EII contains hop acids and chlorophyll. The solutions of hop extracts show very good antioxidant capacities; therefore, they can effectively inhibit or slow negative oxidation reactions and scavenge free radicals and reactive oxygen species (ROS).
Food chemistry.Food Chem.2014 Aug 1;156:353-61. doi: 10.1016/j.foodchem.2014.02.005. Epub 2014 Feb 12.
The article presents the antioxidant properties of the extracts of hop EI and EII, by the electrochemical methods on a platinum electrode and comparative analysis of the composition of the extracts of hops using UV-VIS, FTIR and GC-MS methods. The hops extract EI, was obtained from the waste of the
PMID 24629980

Novel sensory surface for creatine kinase electrochemical detection.

Moreira FT1, Dutra RA2, Noronha JP3, Sales MG4.Author information 1BioMark/ISEP, Instituto Superior de Engenharia do Porto, Porto, Portugal; UOSE, INESC-Porto, Faculdade Ciências/Universidade Porto, Porto, Portugal; REQUIMTE/FCT-UNL, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Portugal.2PROCAPE, LAPED, Universidade Federal de Pernambuco, Recife, Brazil.3REQUIMTE/FCT-UNL, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, Portugal.4BioMark/ISEP, Instituto Superior de Engenharia do Porto, Porto, Portugal. Electronic address: goreti.sales@gmail.com.AbstractThis work describes a novel concept of biosensor for quantifying enzymes, where the substrate is immobilized directly over the working area of a screen printed electrode (Au-SPE). This concept is applied here to creatine kinase isoenzyme (CK-MB), a cardiac biomarker in ischemic conditions. It acts as a phospho-transferase on creatine (Crea), requiring the presence of phosphate. So, the phosphorylated form of creatine (Pcrea) was immobilized on the Au/SPE previously aminated with cysteamine (Cys) by self-assembling monolayer technique. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) studies were used to follow the chemical modifications in the Au-SPE. Since Pcrea is an electroactive species at low potential, its consumption over the platform by the enzyme changed the electrical response of the biosensor. So, CK-MB determination has been achieved in mediator free-conditions due the redox proprieties of the Pcrea. The analytical features of the resulting biosensor were studied by square wave voltammetry (SWV). The limit of detection was 0.11µg/mL and the slope was -0.029(±0.0035)µA×mL/µg. The interference effect of troponin T (TnT), bovine serum albumin (BSA) and myoglobin (Myo) in the performance of the sensor was tested and good selectivity was observed. The biosensor was successfully applied to biological fluids, showing good stability at room temperature and excellent sensitivity and selectivity. This new concept of biosensor is especially useful for point of care (POC) applications, due to the low cost and small size of the final device.
Biosensors & bioelectronics.Biosens Bioelectron.2014 Jun 15;56:217-22. doi: 10.1016/j.bios.2013.12.052. Epub 2014 Jan 16.
This work describes a novel concept of biosensor for quantifying enzymes, where the substrate is immobilized directly over the working area of a screen printed electrode (Au-SPE). This concept is applied here to creatine kinase isoenzyme (CK-MB), a cardiac biomarker in ischemic conditions. It acts a
PMID 24508544

Multiplex electrochemical origami immunodevice based on cuboid silver-paper electrode and metal ions tagged nanoporous silver-chitosan.

Li W1, Li L1, Ge S2, Song X3, Ge L1, Yan M1, Yu J4.Author information 1Key Laboratory of Chemical Sensing & Analysis in Universities of Shandong, School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022, PR China.2Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, School of Material Science and Engineering, University of Jinan, Jinan 250022, PR China.3Cancer Research Center, Shandong Tumor Hospital, Jinan 250117, PR China.4Key Laboratory of Chemical Sensing & Analysis in Universities of Shandong, School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022, PR China. Electronic address: ujn.yujh@gmail.com.AbstractA 3D microfluidic electrochemical origami immunodevice (denoted as µ-ECOI in this work) for sensitive detection of tumor markers was designed. High sensitivity was achieved by using novel cuboid silver modified paper working electrode (CS-PWE) as sensor platform and different metal ions-coated nanoporous silver-chitosan (NSC) as labels. The CS-PWE was fabricated through a seed-mediated growth approach and served as a promising platform for antibodies attachment. The metal ions could be detected directly through square wave voltammetry without metal preconcentration, and each biorecognition event produced a distinct voltammetric peak, whose position and size reflected the identity and amount of the corresponding antigen. The large number of metal ions loading on the NSC greatly amplified the detection signals, and the good biocompatibility of CS-PWE retained good stability for the sandwich-type immunoassay. Using cancer antigen 125 (CA125) and carcinoma antigen 199 (CA199) as model analytes, the simultaneous multiplex immunoassay showed linear ranges of over 4 orders of magnitude with the detection limits down to 0.02 and 0.04mUmL(-1), respectively. Moreover, this strategy accurately detected the concentrations of CA125 and CA199 in human serum samples. The detection limits of CA125 and CA199 were 0.08 and 0.10mUmL(-1), respectively. This facile biosensing µ-ECOI exhibited high sensitivity and specificity with excellent stability, reproducibility, and accuracy, indicating its wide range of potential applications in point-of-care testing.
Biosensors & bioelectronics.Biosens Bioelectron.2014 Jun 15;56:167-73. doi: 10.1016/j.bios.2014.01.011. Epub 2014 Jan 13.
A 3D microfluidic electrochemical origami immunodevice (denoted as µ-ECOI in this work) for sensitive detection of tumor markers was designed. High sensitivity was achieved by using novel cuboid silver modified paper working electrode (CS-PWE) as sensor platform and different metal ions-coated nano
PMID 24487104

Japanese Journal

The Standard Electrode Potential of AgClO₂/Ag and Electrochemical Determination of The Solubility Product of [Ag⁺][ClO₂⁻]

電気化学および工業物理化学 85(6), 294-296, 2017-06
NAID 40021210313

Thermodynamic Analysis of the Transition of Liquid Crystals from Lamellar to Vesicular Phase

Journal of Oleo Science 66(4), 375-382, 2017-04
NAID 40021142575

A Fundamental Study of Local Electrochemical Nano-processing

International journal of electrical machining (22), 36-41, 2017-03
NAID 40021179473

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