Measuring probe for the polarographic determination of partial gas

Abstract

The probe comprises a support of insulating or dielectric material, such as, for example, a glass tube drawn to a closed point at one end. An indicator electrode is supplied as a thin film of metal on the surface of the support, the metal being, for example, platinum or gold. An insulating sandwich-like multi-layer thin film is applied over the indicator electrode film. Preferably, a shielding electrode film is applied over the insulating sandwich-like film and is covered by another insulating film. A composite reference electrode film, including a layer of silver and a layer of platinum or gold, is applied over the outer insulating layer directly or separated by a film of water-proof material such as 'TEFLON' and, for special purposes, the reference electrode film may be covered by another film of water-proof material. In the tip region of the probe, a cut surface is formed through the films and through the insulating support, which cut surface includes a cut surface of the indicator electrode forming the effective surface of the latter, the cut being made in a plane substantially perpendicular to the plane of the indicator electrode. The entire tip of the probe is coated with a diaphragm layer of a hydrophilic organic plastic polymer, such as cellulose acetate. The support structure may include two or even three glass tubes which are arranged in concentric radially spaced relation, with each tube carrying one or more of the several films. The films may be applied by cathode sputtering in vacuum deposition. Electrical conductors or leads are secured to the several electrodes and are preferably covered by the insulating or water-proof layers or films, the several films extending from the tip of the probe for a substantial distance along the support.