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.
ASJC Scopus subject areas
- Analytical Chemistry