Analytical Sciences

Abstract − Analytical Sciences, 14(1), 163 (1998).

Multilayer Potassium Sensor Based on Solid-StateCoextraction
Christian KRAUSE, TobiasWERNER * andOtto S. WOLFBEIS
University of Regensburg,Institute of Analytical Chemistry, Chemo and Biosensors, 93040 Regensburg, Germany
A highly selective solid state multilayer sensor is presented which enablesfluorescence optical determination ofpotassium ions. It is based on co-extraction using valinomycin along with afluorescent anion, both contained in differentlayers. The sensor membrane is composed of two layers of highly differentlipophilicity. The lipophilic phase containsthe carrier valinomycin whilst the hydrophilic phase contains the anionicfluorophore sulforhodamin B. On exposure topotassium ions, the lipophilic phase becomes fluorescent after coextractionof both potassium ions and the anionicfluorophore. To prevent leaching of the dye, an additional blocking layer(nafion) was spread on the sensor. Thedynamic range is from 0.1 to 50 mmol/l K + with very low cross-sensitivity to pH and ionic strength. Theresponse timesvary from 1 to 2 h. (Keywords: Potassium, optical solid state sensor, valinomycin,coextraction)