THICK FILM BIOSENSORS FOR ETHANOL AND UREA

Abstract

Two types of thick film biosensors with different substrate materials were tested for the preparation of amperometric devices and conductivity sensors. We present the determination of alcohol by an amperometric sensor and of urea based on conductometric measurements. Alcohol oxidase and urease were immobilized by crosslinking with glutaraldehyde. The alcohol sensor was fabricated by printing four working electrodes and the auxillary electrode using a platinium paste and the reference electrode using a silver paste on a conventional thick film Al,O,-substrate. The determination of alcohol is based on H,O,-measurement. Thelinear range of this sensor without any additional membraneis limited to 0.8 mmol/l. Hence, real samples required dilution prior to analytic. The results obtained for different beverages correlate acceptably with values obtained by gas chromatography. The conductometric sensors were made using "green-tape"-technique resulting in multi-layer-strips, which include four metal layers printed in a silver-palladium paste. Urea is hydrolysed by urease to ammonia and carbon dioxide resulting in an increase in conductivity. The analytical range of the urea sensors was 1 umol/l up to 5 mmol/l with a linear range from 10 umol/l to 200 umol/l.