JPH0442772Y2 - - Google Patents

Description

[Detailed Description of the Invention] Background of the Invention [Technical Field] This invention relates to an electrode body for gas concentration measurement that detects and measures the concentration of gases such as carbon dioxide and oxygen contained in a mixed gas or blood.

[Prior art and its problems]

As this type of electrode body, for example, the so-called Clark type electrode body is known, which has a three-pole structure of a working electrode, a reference electrode, and a counter electrode, or a two-pole structure of a working electrode and a reference electrode. Because of their good response characteristics, three-electrode structures are attracting attention today for use in measuring gas concentrations using pulse electrolysis methods and the like.

In such an electrode body, the end of each electrode faces, for example, the gas permeable membrane stretched over the opening of the outer case, and the exposed end face formed at the end of the support of the electrode, for example. It has an exposed structure.

However, in the conventional configuration, the contact area between the electrode and the measurement liquid is large, and the gas permeable membrane fluctuates due to the flow and pressure changes of the sample fluid such as mixed gas or blood. There are problems that interfere with the measurements used. Therefore, in order to solve this problem, attempts have been made to reduce the contact area, but in this case, as the partial pressures of carbon dioxide and oxygen increase, the reduction current value generated by the electrolytic reaction will be proportional to these partial pressures. The problem remained that accurate measurement results could not be obtained without deviating from the relationship and losing linearity.

Purpose of the invention This invention was made based on the above circumstances, and its purpose is to control the flow of sample fluid.
An object of the present invention is to provide an electrode body for gas concentration measurement, which is less affected by pressure and has good responsiveness capable of producing a corresponding reduction current value even in a state where the partial pressure of a measurement gas is high, and which enables highly accurate measurement. .

Specific explanation of the invention That is, this invention basically consists of an electrode body for measuring gas concentration in a sample liquid, which includes an outer cylinder housing having at least one opening, and the outer cylinder. A membrane holder attached to the opening of the housing, and a flexible gas permeable membrane detachably fixed to the membrane attachment surface of the membrane holder, detachable from the outer cylinder housing, and facing the part where the measurement gas is present. and working electrodes that are exposed from a support supported by the outer cylindrical housing and arranged independently of each other within the outer cylindrical housing.
a liquid storage chamber that is formed between the reference electrode and the counter electrode, the outer cylindrical housing, and the support body and that accommodates an internal liquid so as to be in contact with the electrode and the gas permeable membrane; and a filling setting in the liquid storage chamber. a protrusion that exposes the working electrode on the side of the support opposite to the gas permeable membrane, and a screw means that allows the outer cylinder housing and the support to move relative to each other in the axial direction; and a tapered end surface portion exposing the reference electrode and the counter electrode, and the outer case is relatively moved in the axial direction by the screw means to contact the working electrode located at the protrusion of the exposed end surface. The object of the present invention is to provide an electrode body for gas concentration measurement, characterized in that the gas permeable membrane is brought into elastic pressure contact to reduce the contact area of the gas permeable membrane with the test liquid.

With the above configuration of the present invention, only the working electrode is in close contact with the gas permeable membrane, so the response speed, which is the most important characteristic of a so-called gas sensor, is quick.
The effect of generated electrolytic products is small, and the internal liquid actively flows through the gap between the support end face and the permeable membrane due to the configuration of the tapered end.
The intended purpose is fully achieved because the electrolytic products diffuse quickly, the liquid resistance between the electrodes is small, and the influence of sample fluid flow and pressure changes is reduced.

Hereinafter, embodiments of this invention will be described with reference to the drawings.

In FIGS. 1 to 3, the illustrated electrode body for gas concentration measurement includes an outer case 1 made of Teflon or the like in a cylindrical shape, and a direction toward the detection end of the case 1 (toward the lower end in FIG. 1). Formed opening 1
an annular membrane holder 3 attached to a via an O-ring 2, and a gas permeable membrane 4 made of flexible Teflon or the like fixed to a membrane attachment surface 3a formed inside the holder. , an electrode support 5 made of polypropylene or the like disposed coaxially with the outer case 1 and inside the outer case 1; A pair of working electrodes 6, a reference electrode 7 and a counter electrode 8 are formed in an annular shape between the support body 5 and the outer case 1, and the inside thereof is made of a non-aqueous solution such as a dimethyl sulfoxide (DMSO) solution. It is provided with a liquid storage chamber 9 filled with an internal liquid.

The outer case 1 and the support body 5 are screwed together at their proximal ends via screw means 10 and are configured to be movable relative to each other in the axial direction. Further, an annular cap 11 is provided on the outside of the membrane holder 3.
It can be screwed into the outer case 1 and fixes the membrane holder 3 in the mounting position.

The three electrodes 6, 7, and 8 are connected to an external device, such as a pulse electrolysis device or a display/recording device, via a cable 12, but are not shown.

The working electrode 6 is made of a silver wire with a diameter of 0.2 mm, for example, and is set along the central axis of the support 5, and the reference electrode 7 and the counter electrode 8 each have a diameter of 1.0 mm.
It is composed of a silver wire and a platinum wire of mm in diameter, and, as shown in FIG. 2, is positioned to sandwich the working electrode 6 in the center.

An exposed end surface 13 is provided at the end of the support 5 facing the permeable membrane so that the ends of the three poles 6, 7, and 8 are exposed at positions facing the gas permeable membrane 4. This end surface 13 is composed of a protrusion 13a exposing the working electrode 6 at the center and a tapered surface section 13b exposing the reference electrode 7 and counter electrode 8, and the tapered surface section 13b has a conical surface.

On the other hand, the gas permeable membrane 4 is brought into contact with a portion where the measurement gas is present by introducing the electrode body into a mixed gas, blood, or the like as a sample fluid when measuring the gas concentration.

As shown in FIG. 1, when the membrane holder 3 is attached to the outer case 1, the gas permeable membrane 4 is in contact only with the working electrode 6 of the protrusion 13a of the exposed end surface 13, and the straight line indicated by the chain line It will be in a curved state compared to its original state. In addition, the membrane mounting surface 3a
is configured as a membrane support surface portion 14 having a concave shape except for the peripheral edge portion that removably fixes the permeable membrane. The membrane support surface portion 14 functions to back up the curved membrane 4, increase the degree of adhesion of the membrane 4 to the protrusion 13a, and stably support the membrane 4.

The degree of close contact of the membrane 4 with the working electrode 6 of the protrusion 13a can be determined by rotating the outer case 1 with respect to the support 5 at the screw means 10.
can be adjusted by relative movement in the axial direction.

However, in either state, since the inclination angle of the tapered surface portion 13a is more acute than that in the curved state of the membrane 3, a sufficient gap is not formed between the exposed end surface 13 and the membrane 4 at the tapered surface portion 13b. Therefore, the internal liquid of the annular liquid storage chamber 9 can actively flow into this gap.

Note that 15 (Fig. 2) is a thermistor.

Further, as a method of fixing the gas permeable membrane 4, the fourth
As shown in the modified example of the figure, the permeable membrane 4 is stretched over the side of the holder 3 from the membrane attachment surface 3a, and the annular groove 16 formed on the side of the holder 3 is filled with O.
- A ring 17 may be inserted to fix the membrane 4 in an airtight manner.

In the modified example shown in FIG. 4, parts corresponding to those in the embodiment shown in FIG. Also in this modification, the membrane holder 3
When the membrane 4 is attached to the protrusion 1 of the support 5
Although the membrane 3a is curved as shown by the chain line, a sufficient gap is left between the tapered surface portion 13b and the membrane 4.

It goes without saying that the present invention is not limited to this embodiment and its modifications.

Specific effects of the invention As described above, according to this invention, only the working electrode comes into close contact with the membrane, and the degree of contact can be set to the optimum state by adjusting the screw means, so it can be used as a gas sensor. The most important characteristic of this is that the response speed is quick, the generation of electrolytic products and their effects are small, and the configuration of the tapered surface part of the exposed end face allows the internal liquid to actively flow between the exposed end face and the membrane, which facilitates electrolysis. Product diffusion is smooth, the liquid resistance between the electrodes can be reduced, the influence of sample fluid flow and pressure changes can be reduced, and the reduction current responds linearly even in areas where the partial pressure of the measurement gas is high. It is possible to provide an electrode body for gas concentration measurement that can obtain a value, has excellent response characteristics, and can perform highly accurate measurement.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an electrode body for gas concentration measurement according to an embodiment of this invention, FIG. 2 is a sectional view taken along the line -- in FIG. 1, and FIG. 3 is an exposed end face portion of the inner cylinder shown in FIG. 1. FIG. 4 is a modified example showing another method of fixing the gas permeable membrane. DESCRIPTION OF SYMBOLS 1...Outer case, 3...Membrane holder, 4...Gas permeable membrane, 5...Electrode support, 10...Screw means, 13...Exposed end surface, 13a...Protrusion, 13b
...Tapered surface part.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) An electrode body for measuring gas concentration in a test liquid, comprising an outer housing having at least one opening, and an electrode body attached to the opening of the outer housing. a flexible gas-permeable membrane that is removably fixed to the membrane mounting surface of the membrane holder and that is removable from the outer cylinder housing and is in contact with a portion where the measurement gas is present; a working electrode, a reference electrode, and a counter electrode that are exposed from the supported support and arranged independently of each other in the outer cylinder housing; and formed between the outer cylinder housing and the support. Also, a liquid storage chamber containing an internal liquid so as to be in contact with the electrode and the gas permeable membrane, the internal liquid filled in the liquid storage chamber, and the outer cylindrical housing and the support body are movable relative to each other in the axial direction. a protrusion exposing the working electrode and a tapered end face exposing the reference electrode and the counter electrode on the side facing the gas permeable membrane of the support; , by relatively moving the outer case in the axial direction by the screw means, the gas permeable membrane is brought into elastic pressure contact only with the working electrode located on the protrusion of the exposed end surface, and the gas permeable membrane is connected to the test liquid. An electrode body for gas concentration measurement characterized by having a small contact area. (2) The electrode body for gas concentration measurement according to claim 1, wherein the tapered end face is formed of a curved surface such as a conical shape or a paraboloid. (3) The electrode assembly for gas concentration measurement according to claim 1, wherein the membrane mounting surface of the membrane holder has a concave membrane supporting surface portion. (4) The electrode assembly for gas concentration measurement according to claim 1, wherein the gas permeable membrane is fixed to the membrane mounting surface of the membrane holder by an O-ring.