Urea Sensor Based on Ion Sensitiive Field Effect Transistor Coated With Cross-Linked Urease-Albumin Membrane

Abstract

The gate of ion sensitive field effect transistor (ISFET) was coated with urease-albumin membrane to fabricate a micro urea sensor. Potentiometric response of the sensor is markedly dependent on the nature of the membranes. Using the sensor with a thiner membrane (ca. 2µm), linear response with a slope of -44 mV/decade has been obtained over the range of 1x10 -4 -5x10 -3 mole/dm 3 (M) urea concentration, response time being 2 min. In contrast, for the thicker membrane (ca. 10µm), Nernstian response with 30 min of the response time has been obtained. The diffusion rate of h+ or OH- in the membranes has been estimated to be a main factor governing the response time of the sensor. Some operating variables such as the buffer concentration and the life time of the sensor have been also examined. © 1984, The Japan Society for Analytical Chemistry. All rights reserved.