This communication describes a new optical sensor suitable for practical measurement of extracellular (serum or whole blood) potassium. The sensor responds rapidly and reversibly to changes in potassium concentrations typical of whole blood samples. No interferences from clinical concentrations of calcium or pH are observed, and the sodium interference is very minor. Excitation and emission occur in the visible light region. This new potassium sensor is currently used in the Roche OPTI CCA, a commercially available whole blood analyzer.

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Chemically homogeneous polymer layers loaded with oxygen-quenchable luminescent dyes may lead to promising applications for optical oxygen sensing. In this work, luminescence quenching of tris(4,7'-diphenyl-1,10'phenanthroline)Ru(II) perchlorate, dissolved in a polystyrene layer, has been investigated. Although the dye

A new optical sensor suitable for practical measurement of sodium in serum and whole blood samples is described. The optical sensor is based on a novel PET (photoinduced electron transfer) fluoroionophore immobilized in a hydrophilic polymer layer. The design concept of the fluoroionophore follows the receptor-spacer-fluorophore approach to sensor design using intramolecular PET-based signal transduction. Key to the development of this sensor is the identification of a nitrogen-containing, sodium-binding ionophore, coupled with a fluorophore having the correct spectral and electron-accepting properties. The slope of the sensor is approximately 0.5%/mM in the typical clinically significant range of 120-160 mM. This sensor has been implemented into a disposable cartridge, used for a commercially available critical care analyzer (Roche OPTI CCA) with precision better than +/- 1 mM (1 SD). The sensor displays excellent stability against hydrolysis and oxidation, leading to slope changes <5% after 9 months wet storage at 30 degrees C. On the basis of this design concept, fluoroionophores for other cations such as potassium, calcium and magnesium can be prepared by substitution of the ionophore.

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