INFLUENCE OF PLASTICIZER ON THE SELECTIVITY OF NITRATE-SENSITIVE CHEMFETS

By chemical modification of an ion-sensitive field-effect transistor, a sensor (CHEMFET) has been developed whose sensitivity for nitrate ha s been tested. A plasticized poly(vinyl chloride) (PVC) membrane, whic h contains lipophilic tetra-n-octyl-ammonium ions, is responsible for the nitrate sensitivity of the device. This membrane has been attached physically on top of a pH-buffered hydrogel, which itself has been at tached covalently to the gate oxide of the field-effect transistor. Th e influence of the plasticizer in the PVC membrane on the selectivity pattern of the CHEMFET for the detection of nitrate has been investiga ted.