CS267864B1 - Gas voltammetric sensor with separate reference electrode - Google Patents

Abstract

The sensor consists of a non-polarized reference electrode placed in a space filled with an electrolyte containing ions whose activity controls the potential of the reference electrode and is separated from the electrolyte in which the working electrode is immersed by a diffusion-limited connection, preferably realized by a ceramic roller with communicating pores of a suitable size. The electrolyte is separated from the measured medium by a separation membrane fixed to the sensor body by a fixing ring. The electrolyte can be replenished through an opening covered by a flexible ring. The sensor is intended for analytical determinations in which components that change the potential of the reference electrode diffuse through the membrane (e.g. determination of oxygen in waters containing hydrogen sulfide) and allows the solution of the sensor with a reference electrode, in which the products of the anodic reaction can subsequently be reduced on the working electrode.

Description

The invention solves a gas voltammetric sensor intended especially for the determination of oxygen in a treatment ensuring protection of a reference electrode against contamination and protection of a working electrode.

The original voltammetric systems for analytical purposes consisted of a mercury drop electrode immersed in a solution in which either a non-polarized reference electrode (mercury at the bottom in a Novak container - Novák 3, VA: Collection, 12, 237, 1947) was either directly placed or a reference electrode was placed. in another electrolyte separated from the analyzed solution with a mercury drop electrode, eg a tap (Kalousek M .: Collection, 11, 592, 1946) or cellophane film (Šerák L .: Chemické listy, 47, 86, 1953; Collection, 18, 439) (1953).

Gas voltammetric sensors represented by Clark's oxygen sensor (Clark L. C.,

Jr .: Appl. Physiol., 6, 189, 1953; Trance. Amer. Soc. Art. Int. Organs, 2, 41, 1956) and modifications thereof, have altered the order. The working electrode is made of solid noble metal such as platinum or gold (not a mercury drop electrode) and has the shape of a target adjacent to the separation membrane so that between the separation membrane and the working electrode there is only a thin electrolyte film which contains ions which controls the potential of the reference electrode, which is also immersed in it. The function of the sensor is that oxygen molecules diffuse from the measured environment through the separation membrane to the working electrode surface where they are reduced.

This arrangement has the disadvantage that, together with the oxygen molecules, in certain cases they can diffuse into the electrolyte also components which change the composition of the solution and thus the properties of the reference electrode. A further disadvantage is that due to the anodic electrode reaction at the reference electrode, substances can form and penetrate into the solution, which are subsequently reduced on the working electrode and contribute to increasing the sensor signal.

These drawbacks are eliminated by a gas voltammetric sensor with a separate reference electrode, which is based on the fact that the space in which the non-polarized reference electrode is located is filled with an electrolyte containing ions whose activity defines the reference electrode potential and separated from the electrolyte in which it is immersed a working electrode with a limited diffusion joint, preferably realized by a ceramic roller with communicating pores. The electrolyte is separated from the measured environment by a separation membrane attached to the sensor body by a fixing ring. The electrolyte defining the potential of the reference electrode may be supplemented by an opening that is covered by a flexible ring.

The advantage of the device is that the sensor in this arrangement has a reference electrode protected from undesirable environmental influences and on the contrary the working electrode is protected from contamination by substances ev. in the vicinity of the reference electrode.

The accompanying drawing (side view) shows a gas voltammetric sensor with a separate reference electrode according to the invention.

On the sensor body 7 is fastened to the fastening ring 2 separation membrane 2> for which is placed in an electrolyte solution of 2 working electrode polarized reference electrode 2 · 2 is placed in a space filled with electrolyte 2 ^{and the} space is separated from electrolyte 2 link 2 with limited diffusion. The electrolyte 2 may be supplemented by an opening which is covered by a flexible ring 10.

Claims (2)

SUBJECT OF THE INVENTION Gas detector with a separate reference electrode consisting of a polarized working electrode, a non-polarized reference electrode, a separation membrane and electrolyte solutions, characterized in that the space in which the non-polarized reference electrode (2) is located in the electrolyte (1) is separated by diffusion a joint (5) from a space filled with an electrolyte solution (3) in which the polarized working electrode (4) is immersed and in contact with the vapor membrane (6). 2. The gas voltametric sensor according to claim 1, characterized in that the non-polarized reference electrode (2) is a second type electrode. 3. The gas voltametric sensor according to claim 1, wherein the non-polarized reference electrode (2) is an argent chloride electrode. 4. The gas voltametric sensor according to claim 1, wherein the non-polarized reference electrode (2) comprises a metal electrode of a noble metal, e.g. platinum or gold, immersed in a solution with a constant redox potential.