Biomaterial Database

Continuous-flow quantitation of Na+ and K+ in nanoliter samples using chromogenic macrocyclic ionophores. 1989

Y Terada, and M A Knepper

Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung and Blood Institute, Bethesda, Maryland 20892.

Continuous-flow colorimetric methods for measurement of sodium and potassium contents in 1- to 30-nl aqueous samples are described. The methods employ macrocyclic ionophores (cryptahemispherands) that selectively bind sodium or potassium, altering the absorbance spectra of covalently attached chromophores. The potassium method is linear in the range 0-350 pmol and exhibits a high degree of precision (coefficient of variation of approximately 2% in the 150- to 350-pmol range). It can detect as little as 8 pmol of K+. The sodium method is linear in the range 0-2,700 pmol and also exhibits a high degree of precision (coefficient of variation of approximately 3% in the 1,700- to 2,700-pmol range). It can detect as little as 57 pmol of Na+. The instrumentation and reagents are available from commercial sources. These methods are proposed for measurement of K+ and Na+ fluxes in isolated perfused tubules.

UI	MeSH Term	Description	Entries
D007476	Ionophores	Chemical agents that increase the permeability of biological or artificial lipid membranes to specific ions. Most ionophores are relatively small organic molecules that act as mobile carriers within membranes or coalesce to form ion permeable channels across membranes. Many are antibiotics, and many act as uncoupling agents by short-circuiting the proton gradient across mitochondrial membranes.	Ionophore
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D003124	Colorimetry	Any technique by which an unknown color is evaluated in terms of standard colors. The technique may be visual, photoelectric, or indirect by means of spectrophotometry. It is used in chemistry and physics. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
D012964	Sodium	A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.	Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23