Potassium selective electrodes are a type of

ion selective electrode An ion-selective electrode (ISE), also known as a specific ion electrode (SIE), is a transducer (or sensor) that converts the activity (chemistry), activity of a specific ion dissolved in a Solution (chemistry), solution into an electrical potentia ...

used in

biochemical Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology an ...

and

biophysical Biophysics is an interdisciplinary science that applies approaches and methods traditionally used in physics to study biological phenomena. Biophysics covers all scales of biological organization, from molecular to organismic and populations. Bi ...

research, where measurements of

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', ''molar concentration'', ''number concentration'', an ...

in an aqueous solution are required, usually on a real time basis. These electrodes are typical ion exchange resin membrane electrodes, using

valinomycin Valinomycin is a naturally occurring dodecadepsipeptide used in the transport of potassium and as an antibiotic. Valinomycin is obtained from the cells of several '' Streptomyces'' species, '' S. fulvissimus'' being a notable one. It is a member ...

, a potassium

ionophore In chemistry, an ionophore () is a chemical species that reversibly binds ions. Many ionophores are lipid-soluble entities that transport ions across the cell membrane. Ionophores catalyze ion transport across hydrophobic membranes, such as liq ...

, as the ion carrier in the membrane to provide the potassium specificity. This type of ion-selective electrode is subject to interference from (in declining order of magnitude) rubidium,

caesium Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that a ...

, ammonium,

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

, and

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid el ...

. The most significant interference with measurement of potassium concentration is from the ammonium ion, which in practice is a problem where the ammonium concentration is approximately equal to or greater than the potassium concentration. Although sodium is usually present in high concentrations in biological preparations, the degree of interference is low enough to represent an error on the order of only 0.05 parts per million for the normal range of sodium concentration, requiring reduction of sodium only for measurements of very low potassium concentrations. Although the interference from rubidium or caesium is strong enough to require that these ions be present in much lower concentration than the potassium to be measured, this is not usually a problem in most experiments. Interference from calcium, magnesium, or lithium, on the other hand, is weak enough that their presence in normal concentrations is also usually not a problem.

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