Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/03/10 15:19:27」(JST)

wiki en

A counterion is the ion that accompanies an ionic species in order to maintain electric neutrality. In table salt the sodium cation is the counterion for the chlorine anion and vice versa. In a charged transition metal complex, a simple (i.e. non-coordinated) ionic species accompanying the complex is termed the counterion.

Examples

Surfactants like cetyl trimethylammonium bromide form micelles in solution. The bromine counterions are retained around the micelles even in the presence of potassium chloride. Selective counterion condensation is observed with cetyl trimethylammonium chloride when the condensed chlorine ions are replaced by bromine on addition of potassium bromide.^[1]

In plant cells, the anion malate is often accumulated in the vacuole to decrease water potential and drive cell expansion. To maintain neutrality, K⁺ ions are often accumulated as the counterion.

Neutrally charged species

A counter ion is a mobile ion,^[2] the presence of which allows the formation of an overall neutrally charged species. For example, in the (neutral) species NaCl the sodium ion is countered by the chloride ion and vice versa. In most situations in chemistry, an ion has a counter ion, exceptions being in ion beams, mass spectrometry and situations where electrons counter the charge of the ion (e.g. the Na/NH₃ system, and plasmas).

Electrochemistry

Often the term is used to indicate an ion that is present in a solution but that is not the focus of the attention. For example when studying the electrochemistry of Co²⁺ one might dissolve the nitrate Co(NO₃)₂. The solution will then contain the counter ion NO₃^- that does not participate in the electrochemical reaction of interest. A very common counter ion is the perchlorate ion ClO₄^-. The reason for this is that perchlorates are typically highly soluble materials.

References

^ http://num.web.psi.ch/reports/2002/pdf/e-28.pdf
^ Nic, M.; Jirat, J.; Kosata, B., eds. (2006–). "counter-ions". IUPAC Compendium of Chemical Terminology (Online ed.). doi:10.1351/goldbook.C01371. ISBN 0-9678550-9-8. http://goldbook.iupac.org/C01371.html.

This chemistry-related article is a stub. You can help Wikipedia by expanding it.

English Journal

Influence of sodium carboxymethylcellulose on the aggregation behavior of aqueous 1-hexadecyl-3-methylimidazolium chloride solutions.

Das B1, Ray D2, De R3.
Carbohydrate polymers.Carbohydr Polym.2014 Nov 26;113:208-16. doi: 10.1016/j.carbpol.2014.07.002. Epub 2014 Jul 17.
The influence of sodium carboxymethylcellulose (NaCMC) on the aggregation phenomena of a surface active ionic liquid 1-hexadecyl-3-methylimidazolium chloride (C16MeImCl) was studied in aqueous solutions using electrical conductivity and surface tension measurements. The counterion condensation behav
PMID 25256477

The growth of charged platelets.

Labbez C1, Jönsson B, Woodward C, Nonat A, Delhorme M.
Physical chemistry chemical physics : PCCP.Phys Chem Chem Phys.2014 Nov 21;16(43):23800-8. doi: 10.1039/c4cp03246b. Epub 2014 Oct 2.
Growth models of charged nanoplatelets are investigated with Monte Carlo simulations and simple theory. In a first model, 2-dimensional simulations in the canonical ensemble are used to demonstrate that the growth of a single weakly charged platelet could be limited by its own internal repulsion. Th
PMID 25273977

GUMBOS matrices of variable hydrophobicity for matrix-assisted laser desorption/ionization mass spectrometry.

Al Ghafly H1, Siraj N, Das S, Regmi BP, Magut PK, Galpothdeniya WI, Murray KK, Warner IM.
Rapid communications in mass spectrometry : RCM.Rapid Commun Mass Spectrom.2014 Nov 15;28(21):2307-14. doi: 10.1002/rcm.7027.
RATIONALE: Detection of hydrophobic peptides remains a major obstacle for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). This stems from the fact that most matrices for MALDI are hydrophilic and therefore have low affinities for hydrophobic peptides. Herein, 1-aminopyrene
PMID 25279744