JPH1090217A - Sensor for analyzing polarograph type dissolved gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarograph type sensor for analyzing dissolved gas capable of infallibly removing influence of interfering component gas dissolved in an electrolyte regardless of the concentration of the measurement objective gas in liquid. SOLUTION: This sensor, which includes a diaphragm 4 permeating measurement objective gas in a liquid 5 contacting with its exterior surface 'a' but not permeating an electrolyte 6 contacting with its interior surface 'b', and an action pole 7 provided closely to the interior surface 'b' so that an electrolyte phase 11 isolated from the liquid 5 by the diaphragm 4 is formed, measures the density of the measurement objective gas in the liquid 5 by an electrochemical reaction on an action pole surface 7a of the measurement objective gas reaching the action pole surface 7a by diffusing the electrolyte phase 11 after permeating the diaphragm 4. In this case, an electrolyte passage 14 formed on the electrolyte phase 11 by running the action pole 7 through it so that they may communicate with each other and a sealing means 10 for sealing the electrolyte from coming in and out of the electrolyte phase 11 other through the electrolyte passage 14 are provided and an auxiliary pole 8 is also provided for consuming the interfering component dissolved in the electrolyte 6 inside the electrolyte passage on this side of the action pole 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarographic sensor for dissolved gas analysis having a novel structure for eliminating the influence of interfering component gases dissolved in an electrolytic solution.

[0002]

2. Description of the Related Art FIG. 4 shows a method of measuring the concentration when a conventional sensor for analyzing dissolved gas of a diaphragm type is used for measuring dissolved oxygen in water. In FIG. 4, a gap (electrolyte phase) 43 of several tens to several hundreds microns is formed between the working electrode 41 and the diaphragm 42, and the electrolyte A is supplied to the electrolyte phase 43 from around the working electrode 41. When an external voltage is applied between the working electrode 41 and the counter electrode (not shown), the electrolyte phase 43 is diffused in a state where the gas to be measured (O ₂ gas) which has passed through the diaphragm 42 is dissolved, and is diffused to the working electrode surface 41a. The dissolved gas reaches the working electrode surface 41a of the dissolved gas (O ₂ gas) and is consumed by the electrochemical reaction. R indicates a region of the dissolved gas (O ₂ gas) consumed on the working electrode surface 41 a, and S indicates a guard electrode 45 coaxially arranged to cover the periphery of the working electrode 41 after passing through the diaphragm 42. 3 shows a region of the dissolved gas (O ₂ gas) consumed on the surface 45a.

[0003]

For example, the dissolved gas region S is a region in which a so-called interfering component gas (O ₂ gas) is dissolved, and the interfering component gas is only the dissolved gas region S. Rather, the electrolyte solution A moves to the electrolyte solution phase 43 in a state in which the electrolyte solution A has permeated and dissolved from all parts of the diaphragm 42 other than the diaphragm portion 42 a immediately above the dissolved gas region R, while the measurement target gas in the liquid 44 When the concentration fluctuates greatly, the gas to be measured (O ₂ gas) is required for 100% response.
It takes time for the partial pressure of the gas to become equal to the partial pressure of the dissolved gas (O ₂ gas) in the electrolytic solution. Therefore, the interfering component gas dissolved in the electrolytic solution A is also consumed on the working electrode surface 41a, or the measurement target gas in the dissolved gas region R to be consumed on the working electrode surface 41a does not touch the working electrode 41. Inconvenience occurs. In particular, when an extremely low concentration gas to be measured is measured, the degree of influence on the measured value increases, and as a result, there is a disadvantage that a response speed is delayed and an analysis error occurs.

The present invention has been made in consideration of the above-mentioned matters, and an object of the present invention is to surely prevent the influence of the interfering component gas dissolved in the electrolytic solution regardless of the concentration of the gas to be measured in the liquid. An object of the present invention is to provide a polarographic dissolved gas analysis sensor that can be removed.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a diaphragm which transmits a gas to be measured in a liquid which comes into contact with an outer surface and does not transmit an electrolytic solution which comes into contact with an inner surface; A working electrode provided in close proximity to the inner surface to form an electrolyte solution phase separated from the liquid, and after passing through the diaphragm, diffuse the electrolyte solution phase to the working electrode surface In a polarographic dissolved gas analysis sensor for measuring the concentration of a gas to be measured in a liquid by an electrochemical reaction of the gas to be measured on the surface of the working electrode by an electrochemical reaction, the sensor is formed so as to communicate with the electrolytic solution phase through a working electrode. An electrolytic solution flow path, and a sealing means for sealing the flow of the electrolytic solution into and out of the electrolytic solution phase from other than the electrolytic solution flow path, and further, in the electrolytic solution flow path, before the working electrode, Dissolved in the liquid An auxiliary electrode which consume interfering components are are installed.

In the present invention, the region sandwiched between the diaphragm, the working electrode and the sealing means is used as the electrolyte phase, the flow path of the electrolyte in which the interfering component gas is dissolved is restricted in one direction, In the liquid flow path, since the disturbing component gas is configured to be consumed by the auxiliary electrode installed before the electrolytic solution is supplied to the working electrode, the dissolved component gas reaching the working electrode is transmitted through the diaphragm. Since the measurement is limited to the gas to be measured in the liquid, the influence of the interfering component gas can be reliably removed regardless of the concentration of the gas to be measured in the liquid.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A shows an embodiment of a polarographic dissolved gas analysis sensor (hereinafter, referred to as a sensor) T of the present invention into which an electrolytic solution 6 is injected. In this embodiment, a case is shown in which a dissolved oxygen meter (DO meter) used for measuring dissolved oxygen in water is used as the sensor T. FIG. 1B shows the surface (flat surface) 7a of the working electrode 7. FIG. 2 shows a main part of the sensor T.

1 (A), 1 (B) and 2, reference numeral 1 denotes a body of a sensor T, which comprises, for example, a cylindrical outer body 2 and a cylindrical inner body 3. Reference numeral 4 denotes a diaphragm, which is attached to the upper end of the outer body 2 so as to cover the upper opening K of the outer body 2. At the time of use, the sensor T is installed so that water 5 as a sample liquid contacts the outer surface a of the diaphragm 4 and the electrolytic solution 6 contacts the inner surface b of the diaphragm 4. As the diaphragm 4, an oxygen-permeable thin film, such as Teflon, high-pressure polyethylene, or silicone rubber, which does not allow the passage of the electrolytic solution 6 is used.

Reference numeral 7 denotes a working electrode made of Ag attached to the inner wall c at the upper end 3a of the inner body 3.
The working electrode 7 is provided near the inner surface b of the diaphragm 4, and an auxiliary electrode 8 made of Ag is attached to the inner wall c below the working electrode 7. Reference numerals 20 and 21 denote a lead wire of the working electrode 7 and a lead wire of the auxiliary electrode 8, respectively, and both of the lead wires 20 and 21 pass through the inside of the inner body 3 and are connected to a substrate (not shown). 9 means both 7,8
With a thickness D of several tens of microns,
The spacers 9 keep the two 7, 8 in parallel. Reference numeral 12 denotes a counter electrode made of Pb attached to the outer wall of the large diameter portion 13 of the inner body 3. The lead wire 22 of the counter electrode 12 is also connected to the substrate, and a predetermined external voltage is applied between the working electrode 7 and the counter electrode 12 and between the auxiliary electrode 8 and the counter electrode 12 at the time of measurement.

Reference numeral 10 denotes an annular projection which is in contact with the inner surface b of the diaphragm 4 and is formed to protrude from the tip 3a of the inner body 3 toward the diaphragm. The annular projection 10 functions as a sealing means for preventing the electrolyte 6 from flowing into and out of the electrolyte phase 11 to be described later from other than the electrolyte flow path (described later) 14.

Reference numeral 11 denotes an electrolyte phase, which is sandwiched between the annular projection 10, the diaphragm 4, and the working electrode 7. This electrolyte phase 11
Corresponds to the length between the working electrode surface (flat surface) 7a and the inner surface b of the diaphragm 4, and is several tens to several hundreds of microns. This thickness d is controlled by the annular projection 10. When an external voltage is applied between the working electrode 7 and the counter electrode 12, the gas to be measured (O ₂ gas) that has passed through the diaphragm portion 4a immediately above the electrolyte phase 11 diffuses through the electrolyte phase 11, and the dissolved gas (O ₂ gas) reaches the working electrode surface 7a, and the dissolved oxygen concentration of the measurement target gas (O ₂ gas) in the liquid 5 by the electrochemical reaction of the dissolved gas (O ₂ gas) on the working electrode surface 7a ( The concentration can be determined by measuring the diffusion current in proportion to the (partial pressure).

Further, the working electrode 7 has a plurality of electrolyte passages p formed in a lattice shape in plan view, and the auxiliary electrode 8 has a plurality of electrolyte solutions formed in a grid shape in plan view similar to the working electrode 7. It has a passage q.

The spacer 9 is formed of a thin film (for example, a Teflon thin film) having a plurality of slits (not shown) of a size through which the electrolyte 6 can pass, and is provided between the working electrode back surface 7b and the auxiliary electrode back surface 8a. It is sandwiched.

Reference numeral 14 denotes an electrolyte solution flow path which is formed so as to communicate with the electrolyte solution phase 11 through the electrolyte solution inlet / outlet 15, the auxiliary electrode 8, the spacer 9, and the working electrode 7 formed in the inner body 3 in order from the lower side. I have. That is, the electrolyte flow path 1
4 includes a passage q of the auxiliary electrode 8, a slit of the spacer 9, and a passage p of the working electrode 7.

Then, by applying a predetermined external voltage between the auxiliary electrode 8 and the counter electrode 12, by the same operation as the working electrode 7, the interfering component gas (dissolved in the electrolytic solution 6 passing through the entrance 15) O ₂ gas) is consumed by the auxiliary electrode 8.

Incidentally, the sealing means may be constituted by a ring 33 (see FIG. 3) inserted into an annular groove N formed on the upper surface n of the distal end portion 3a of the inner body 3. in this case,
The diaphragm 33 is pressed by the ring 33 toward the upper surface n, and the electrolyte phase 11 can be sealed.

Thus, between the working electrode 7 and the counter electrode 12, the auxiliary electrode 8
The measurement is started in a state where a predetermined external voltage is applied between the counter electrode 12 and the counter electrode 12, respectively.

In this embodiment, as described above, the electrolytic solution phase 11 is supplied with the electrolytic solution 6 containing no interfering component gas (dissolved O ₂ gas).

That is, the electrolytic solution 6 passes through the passage q of the auxiliary electrode 8 from the entrance 15. In this case, the entrance 15
The electrolyte 6 passing through contains the disturbing component gas (dissolved O ₂ gas) that has permeated from all parts of the diaphragm part 4 b other than the diaphragm part 4 a immediately above the electrolyte phase 11, When the dissolved O ₂ gas comes into contact with the front surface (flat surface) 8b, an electrochemical reaction similar to that of the working electrode 7 occurs, and while the electrolytic solution 6 passes through the electrolytic solution passage q, the dissolved O ₂ gas Is consumed.

Therefore, in a state where the O ₂ gas permeating the diaphragm 4 is dissolved, the electrolyte phase 11 is diffused and the working electrode surface 7 a
And the working electrode surface 7a of this dissolved gas (O ₂ gas)
The dissolved gas is consumed by the electrochemical reaction in step ( ₂₎ , and the concentration of the O ₂ gas can be accurately measured without being affected by the interfering component gas.

Thus, the electrolyte 6 reaching the working electrode 7
Channel 14 is limited in one direction, and an auxiliary electrode 8 for consuming the interfering component gas (dissolved O ₂ gas) contained in the electrolytic solution 6 is provided in the channel 14 and before the working electrode 7. As a result, the dissolved O ₂ gas reaching the working electrode 7
Is limited to only the O ₂ gas in the sample liquid 5 that has passed through, and as a result, measurement accuracy and response speed can be improved.

[0022]

As described above, in the present invention, the region sandwiched by the diaphragm, the working electrode and the sealing means is used as the electrolyte phase, and the flow path of the electrolyte in which the interfering component gas is dissolved is unidirectional. And, in the flow path of the electrolytic solution, the auxiliary component disposed before the electrolytic solution is supplied to the working electrode is configured to consume the disturbing component gas. Since the component gas is restricted to only the gas to be measured in the liquid that has passed through the diaphragm, the influence of the interfering component gas can be reliably removed regardless of the concentration of the gas to be measured in the liquid. As a result, the response speed at the time of measuring an extremely low concentration sample is improved, and highly accurate measurement can be performed in a short time.

[Brief description of the drawings]

FIG. 1A is an explanatory view of the overall configuration of a polarographic dissolved gas analysis sensor according to an embodiment of the present invention, and FIG. 1B is a diagram showing the shape of a working electrode in the embodiment.

FIG. 2 is an explanatory diagram of a main part configuration in the embodiment.

FIG. 3 is an explanatory diagram of a main part configuration showing a modification of the sealing means used in the embodiment.

FIG. 4 is an explanatory diagram of a main part configuration showing a conventional polarographic dissolved gas analysis sensor.

[Explanation of symbols]

4 ... diaphragm, 5 ... sample solution, 6 ... electrolyte solution, 7 ... working electrode,
7a: working electrode surface, 8: auxiliary electrode, 10: annular projection (sealing means), 11: electrolytic solution phase, a: outer surface of diaphragm, b: inner surface of diaphragm.

Claims (6)

[Claims] 1. A diaphragm that transmits a gas to be measured in a liquid that contacts an outer surface and does not transmit an electrolyte that contacts an inner surface, and forms an electrolyte phase that is isolated from the liquid by the diaphragm. A working electrode provided in the vicinity of the inner surface, the electrochemical reaction of the gas to be measured reaching the working electrode surface by diffusing the electrolytic solution phase after passing through the diaphragm, at the working electrode surface In a polarographic dissolved gas analysis sensor for measuring the concentration of a gas to be measured in a liquid, an electrolytic solution flow path formed to communicate with the electrolytic solution phase through a working electrode, and the electrolytic solution from other than this electrolytic solution flow path A sealing means for sealing the entry and exit of the electrolyte into and out of the liquid phase, and further in the electrolyte passage, before the working electrode,
A polarographic sensor for dissolved gas analysis, comprising an auxiliary electrode for consuming an interfering component dissolved in an electrolytic solution. 2. The polarographic dissolved gas analysis sensor according to claim 1, wherein the electrolyte solution flow path includes a plurality of passages formed in the auxiliary electrode and the working electrode in a lattice shape in plan view. 3. The polarographic dissolution according to claim 1, wherein the sealing means is formed by an annular projection formed on the body having the working electrode attached to the distal end thereof and projecting toward the diaphragm. Gas analysis sensor. 4. The sealing means is constituted by a ring which sandwiches the electrolyte phase between the diaphragm and the working electrode in a state in which the body having the working electrode attached to the tip thereof is pressed through the diaphragm. 3. The polarographic sensor for dissolved gas analysis according to claim 1 or claim 2. 5. The polarographic dissolved gas analysis sensor according to claim 1, wherein the working electrode and the auxiliary electrode are held by the body in a parallel state by a spacer that insulates the working electrode and the auxiliary electrode. . 6. The polarographic apparatus according to claim 5, wherein the spacer is formed of a Teflon thin film having a predetermined thickness and having a plurality of slits through which an electrolyte can pass, and is sandwiched between the working electrode and the auxiliary electrode. Type dissolved gas analysis sensor.