Chemically sensitive measuring cells - based on insulated-gate FET as pH sensor

摘要

Measuring cells for determining the concn. of a given ion (I) in a test soln. comprise an ion-sensitive system electrochemically connected to the insulated gate of a pH sensor via a (I)-contg. liq. or gel or a conductive resin. The pH sensor is in the form of an insulated-gate field-effect transistor (IG FET). The potential difference (p.d.) between the test soln. and the ion-sensitive system is applied to the insulated gate of the pH sensor, whereby the concn. of (I) can be determined from the change in the source-drain current of the pH sensor. Measuring cells for determining the concn. of a given substance (II) in a test material comprise an O2 electrode and a chemically sensitive system electrochemically connected to an IG FET pH sensor via a conductive resin. The O2 electrode comprises Ag and Pt electrodes connected respectively to the positive and negative terminals of a direct-current source and generates a p.d. in response to the change O2 concn. in the chemically sensitive system. The p.d. is applied to the insulated gate of the pH sensor, whereby the concn. of (II) can be determined from the change in the source-drain current. Cells of type (A) can be used e.g. for Na+ or K+ determn. in blood serum. Cells of type (B) can be used e.g. for determn. of serum glucose, c.f. cells in which an ion-sensitive film is applied directly onto the insulated gate, the use of a conductive bridge between the insulated gate and the ion- or chemically sensitive system allows greater flexibility in the choice of systems, improves selectivity and durability, and reduces junction resistance and noise.