WO2023286400A1 - Electrochemical measurement device and electrochemical measurement method - Google Patents

Abstract

This electrochemical measurement device is for electrochemically measuring the concentration of a to-be-measured substance included in a sample liquid, the electrochemical measurement device comprising: a flow path through which the sample liquid flows; and a working electrode and a counter electrode having a liquid contact surface in contact with the sample liquid flowing through the flow path. The liquid contact surface of the working electrode and the liquid contact surface of the counter electrode are disposed so as to be offset from each other along the direction in which the flow path extends, and such that each portion of the surfaces directly face each other.

Description

Electrochemical measuring device and electrochemical measuring method

The present invention relates to an electrochemical measuring device and an electrochemical measuring method.

For example, in the process of washing and sterilizing food, it is necessary to strictly control the chlorine concentration within the range where sterilization is properly performed. Therefore, it is required to accurately measure the chlorine concentration in the washing liquid used to wash food.

As an apparatus for measuring the chlorine concentration in a cleaning solution with high accuracy, for example, as shown in Patent Document 1, a flow injection type electrochemical system that performs voltammetry measurement in which a sample is analyzed by applying a voltage to a sample solution that is an electrolyte solution is used. A device is known (for example, US Pat. In this device, a cleaning solution, which is a sample solution, is sent to a measuring cell equipped with a working electrode, a reference electrode and a counter electrode, and a predetermined voltage is applied to the working electrode to measure the chlorine concentration in the sample solution. be able to.

Japanese Patent Application Laid-Open No. 2020-034408

By the way, when measuring the chlorine concentration or the like in a sample liquid using the electrochemical measurement apparatus as described above, electromagnetic noise generated from other analyzers or electric field processing devices penetrates into the measurement cell through the sample liquid. There is a risk that the measurement accuracy will be degraded. In order to reduce the influence of such noise, it is preferable to place the working electrode and the counter electrode as close as possible. However, when these electrodes are placed so as to face each other completely, bubbles generated on the liquid contact surface (sensor surface) of the working electrode accumulate on the step between the liquid contact surface of each electrode and the channel. This causes a problem that the measurement accuracy is lowered.

The present invention has been made to solve such problems at once, and is mainly intended to reduce the retention of bubbles generated at the working electrode while reducing the influence of electromagnetic noise in an electrochemical measurement device. This is an issue.

That is, an electrochemical measuring apparatus according to the present invention electrochemically measures the concentration of a substance to be measured contained in a sample liquid, and comprises a channel through which the sample liquid flows, and the sample flowing through the channel. a working electrode and a counter electrode having liquid-contacting surfaces in contact with a liquid, wherein the liquid-contacting surface of the working electrode and the liquid-contacting surface of the counter electrode are displaced from each other along the direction in which the channel extends, and It is characterized by being arranged so that a part faces directly.

According to the electrochemical measurement apparatus configured as described above, the working electrode and the counter electrode are brought close to each other so that parts of their wetted surfaces face each other. noise can be reduced. In addition, since the liquid contact surface of the working electrode and the liquid contact surface of the counter electrode are arranged so as to be offset from each other along the direction in which the flow channel extends while partly facing each other, the flow of the sample liquid is disturbed. can be generated, and bubbles generated on the wetted surface of the working electrode can be discharged downstream without remaining.

As a mode in which the effect of the present invention is exhibited remarkably, as a specific mode of the electrochemical measurement device, the inner wall surface forming the flow path has concave portions at positions respectively corresponding to the counter electrode and the working electrode. and the bottom surface of each of the recesses is constituted by the liquid contact surfaces of the working electrode and the counter electrode.

The electrochemical measurement device includes a measurement channel portion in which the channel faces the liquid contact surface of the working electrode and the liquid contact surface of the counter electrode, and the measurement channel portion It is preferable that the sample liquid is applied perpendicularly or obliquely from the upstream side to the downstream side to the liquid-contacting surface of the counter electrode disposed on the downstream side.
If the measurement channel section is formed in this way, by applying the sample liquid perpendicularly or obliquely to the wetted surface of the electrode on the downstream side, the bubbles accumulated on the wetted surface of the electrode on the downstream side can be effectively removed. It can be pushed away well.

Further, in the electrochemical measurement device, the channel is preferably formed so that the sample liquid is applied perpendicularly or obliquely to the liquid-contacting surface of the working electrode.
In this way, the flow of the sample liquid collides with the wetted surface of the working electrode, which tends to cause turbulent flow. Makes it easier to remove air bubbles.

In order to make it easier for air bubbles generated on the wetted surface of the working electrode to escape without stagnation, the electrochemical measurement device is formed such that the sample liquid flows upward in the measurement flow path, and the working electrode It is preferable that the contact surface of the counter electrode and the contact surface of the counter electrode are displaced vertically along the measurement channel.

The electrochemical measurement device further includes a fluid blocking part capable of blocking the flow of the sample liquid upstream of the working electrode and the counter electrode in the channel, and the fluid blocking part blocks the flow of the sample liquid. It is preferable that the concentration of the substance to be measured contained in the sample liquid is electrochemically measured in this state.
In this way, by blocking the flow of the sample liquid during measurement, it is possible to block external electromagnetic noise transmitted through the sample liquid, thereby improving the measurement accuracy.
A roller pump, a diaphragm pump, or an on-off valve is mentioned as a specific aspect of such a fluid shutoff part.

It is preferable that the electrochemical measurement device is provided with a second counter electrode upstream of the working electrode and the counter electrode in the channel.
With such a structure, the electromagnetic noise transmitted through the sample liquid is absorbed by the second counter electrode, thereby reducing the influence of the electromagnetic noise transmitted to the working electrode and the counter electrode on the downstream side.

Further, in the electrochemical measurement device, the working electrode and the counter electrode are preferably arranged in this order from upstream.
By doing so, the counter electrode can absorb the electromagnetic noise transmitted from the downstream side of the working electrode through the sample liquid, so that the measurement accuracy can be further improved.

Further, the electrochemical measurement method of the present invention uses an electrochemical measurement device comprising a channel through which a sample liquid flows, and a working electrode and a counter electrode each having a wetted surface contacting the sample liquid flowing through the channel. An electrochemical measurement method for electrochemically measuring the concentration of a substance to be measured contained in a liquid, wherein the liquid contact surface of the working electrode and the liquid contact surface of the counter electrode are arranged along the direction in which the channel extends. are arranged such that they are offset from each other and some of them face each other.
According to such an electrochemical measurement method, the same effect as the electrochemical measurement device of the present invention described above can be obtained.

According to the present invention, in an electrochemical measurement device, it is possible to reduce the retention of bubbles generated at the working electrode while reducing the influence of electromagnetic noise.

1 is a diagram showing the overall configuration of an electrochemical measuring device according to one embodiment of the present invention; FIG. The figure which shows roughly the structure of the measuring cell of the electrochemical measuring apparatus of the same embodiment. FIG. 3 is an enlarged view of part A in FIG. 2 ; FIG. 2 is a functional block diagram of the electrochemical measurement device of the same embodiment; The figure which shows roughly the structure of the measuring cell of the electrochemical measuring apparatus of other embodiment. The figure which shows roughly the structure of the measuring cell of the electrochemical measuring apparatus of other embodiment. The figure which shows roughly the structure of the measuring cell of the electrochemical measuring apparatus of other embodiment.

An electrochemical measurement device 100 according to one embodiment of the present invention will be described below with reference to the drawings.

The electrochemical measurement device 100 of the present embodiment is, for example, a flow injection type electrochemical measurement device 100 that performs triode voltammetry measurement in which a sample is analyzed by applying a voltage to a sample liquid that is an electrolyte solution.

The electrochemical measurement apparatus 100 can be used for various purposes. Here, it is connected to a flow path (also referred to as a main flow path ML) in which a cleaning liquid used to wash foods such as vegetables flows, and the water contained in the cleaning liquid is connected to the flow path. It is configured to measure the concentration of residual chlorine (which is the substance to be measured) in the Residual chlorine refers to all available chlorine contained in the aqueous solution. And this available chlorine includes free chlorine such as hypochlorous acid (HClO), hypochlorite ion (ClO ⁻ ), dissolved chlorine (Cl ₂ ), monochloramine (NH ₂ Cl) and dichloramine (NHCl ₂ ). , and trichloramine (NCl ₃ ).

Specifically, as shown in FIG. 1, the electrochemical measurement apparatus 100 includes a box-shaped casing 1 having side walls provided with an inlet port P1 and an outlet port P2, and both ends of the casing 1 having an inlet port P1 and an outlet port P1. A sample flow path 2 connected to the port P2 to flow the sample liquid introduced from the inlet port P1 and lead to the outlet port P2, a sensor section 3 provided on the sample flow path 2, and a signal from the sensor section 3. and an information processing device 5 for calculating the concentration of components in the sample based on the voltage, current, etc. obtained by the measurement circuit 4 .

The inlet port P1 is connected to a first branch pipe forming a first branch channel BL1 branching from the main channel ML, and the outlet port P2 forming a second branch channel BL2 branching from the main channel ML. It is connected to the second branch pipe. The sample liquid flowing through the main channel ML passes through the first branch channel BL1 and is taken into the sample channel 2 via the inlet port P1. It is returned to the main flow path ML through the branch flow path BL2.

The sample flow path 2 includes an inlet flow path 21 that guides the sample liquid introduced from the inlet port P1 to the sensor section 3, a sensor flow path 22 provided in the sensor section 3, and an outlet port P2 that transfers the sample liquid exiting the sensor section 3. and an outlet channel 23 leading to the The upstream end of sensor channel 22 is connected to the downstream end of inlet channel 21 , and the downstream end of sensor channel 22 is connected to the upstream end of outlet channel 23 .

The sensor unit 3 includes a measurement cell 31 having a sensor channel 22 formed therein, a working electrode 32 attached to the measurement cell 31 and having a liquid-contact surface that contacts the sample liquid flowing through the sensor channel 22, and a reference electrode 33. and a counter electrode 34 . Here, a reference electrode 33, a working electrode 32, and a counter electrode 34 are provided in this order from upstream.

The measurement cell 31 is, for example, of a flow cell type having a block shape as shown in FIGS. This sensor flow path 22 is formed by the inner wall of a tubular through-hole 311 passing through the measurement cell 31 . An upstream end of the sensor channel 22 communicates with an inlet 22a formed on one end face of the measurement cell 31, and a downstream end of the sensor channel 22 communicates with an outlet port 22b formed on the other end face of the measurement cell 31. communicates with The inlet port 22 a is connected to the downstream end of the inlet channel 21 and the outlet port 22 b is connected to the upstream end of the outlet channel 23 . In this embodiment, the introduction port 22 a is formed on the bottom surface of the measurement cell 31 and the outlet port 22 b is formed on the top surface of the measurement cell 31 . The sample liquid introduced from the inlet 22a flows through the sensor channel 22 from the bottom to the top (upward) and is discharged from the outlet 22b.

More specifically, the sensor channel 22 includes an introduction channel portion 221 whose upstream end is connected to the inlet port 22a, and a measurement sensor provided downstream of the introduction channel portion 221 and facing the liquid contact surface 321 of the working electrode 32. and a channel portion 222 . The downstream end of this measurement channel section 222 is connected to the outlet 22b.

The working electrode 32 has a sensor surface (liquid contact surface) 321 for detecting the object to be measured by applying a voltage in contact with the sample liquid. Specifically, the working electrode 32 is, for example, a diamond electrode in which the sensor surface 321 is formed of boron-doped diamond having conductivity by doping boron at a high concentration.

The reference electrode 33 is an electrode that serves as a reference for the potential of the working electrode 32, and in this embodiment, a silver/silver chloride electrode is used.

The counter electrode 34 allows current to flow through the working electrode 32 without hindrance when setting a certain potential on the working electrode 32 . Similar to the working electrode 32, this embodiment uses a boron-doped diamond electrode.

These working electrode 32 , reference electrode 33 , and counter electrode 34 are attached to the measurement cell 31 so that their wetted surfaces 321 , 331 , 341 are all in contact with the sample liquid in the sensor channel 22 . there is Specifically, the measurement cell 31 has a plurality of thin portions 312 whose thickness is relatively smaller than that of other portions. 313 are formed. Each of the electrodes 32, 33, 34 is attached to the thin portion 312 so that the liquid contact surfaces 321, 331, 341 of the electrodes 32, 33, 34 cover the opening 313 from the outside. Sealing members S such as O-rings and gaskets are interposed between the liquid contact surfaces 321, 331, 341 of the electrodes 32, 33, 34 and the outer wall surface of the thin portion 312, and the gap between them is watertight. Sealed.

In addition, upstream of the sensor section 3 in the sample channel 2 (specifically, the inlet channel 21), a fluid blocking section 6 capable of blocking the flow of the sample liquid is provided. Specifically, the fluid blocker 6 of this embodiment is a roller pump (tubing pump). When the roller pump is driven, the sample liquid flows through the inlet channel 21 to the sensor section 3, and when the roller pump is stopped, the flow of the sample liquid in the inlet channel 21 is interrupted, and the sample liquid is sent to the sensor section 3. is set to stop.

The measurement circuit 4 applies a voltage to the working electrode 32, the reference electrode 33 and the counter electrode 34 and detects the current value at the applied voltage, and includes, for example, a potentiostat.

The information processing device 5 is a dedicated or general-purpose computer equipped with a CPU, internal memory, input/output interface, A/D converter, and the like. Based on a predetermined program stored in the internal memory, the information processing device 5 controls the voltage applied to the measuring circuit 4 as shown in FIG. A section 51 obtains a current-residual chlorine concentration curve from the relationship between the current signal output from the measuring circuit 4 and the residual chlorine concentration, and calculates the concentration of residual chlorine in the sample based on this current-residual chlorine concentration curve. It functions as a fluid control unit 53 that controls the unit 52 and the fluid cutoff unit 6 .

In the electrochemical measurement apparatus 100 of the present embodiment, the voltage control unit 51 applies a voltage to the measurement circuit 4 while the flow of the sample liquid is blocked by the fluid blocking unit 6 and the liquid supply to the sensor unit 3 is stopped. , the calculating unit 52 is configured to calculate the concentration of residual chlorine.

Thus, in the electrochemical measurement apparatus 100 of the present embodiment, the liquid contact surface 321 of the working electrode 32 and the liquid contact surface 341 of the counter electrode 34 are displaced from each other along the direction in which the sensor channel 22 extends, and they are are arranged to face each other.

Specifically, both the working electrode 32 and the counter electrode 34 are provided so that the liquid contact surfaces 321 and 341 thereof face the measurement channel section 222, and the liquid contact surface 321 of the working electrode 32 and the counter electrode 34 are opposed to each other with the measurement flow path section 222 interposed therebetween. The measurement channel portion 222 is formed so that the sample liquid flows upward. are placed. Here, the working electrode 32 is arranged below (upstream) and the counter electrode 34 is arranged above (downstream).

In addition, recesses 22r are formed at positions corresponding to the counter electrode 34 and the working electrode 32 on the inner wall surface forming the measurement flow channel portion 222 . The bottom surface of each concave portion 22r is formed by the liquid contact surfaces 321 and 341 of the corresponding electrodes 32 and 34, respectively. The bottom surfaces of the recesses 22r are displaced along the direction in which the measurement flow path section 222 extends, and are arranged such that they partially face each other (partially overlap and face each other). ing. Note that part of the liquid contact surface 321 and the liquid contact surface 341 face each other means that part of the liquid contact surfaces 321 and 341 face each other with the measurement flow path part 222 interposed therebetween. The one surface 321 and the other surface 341 may be parallel to each other or may be inclined to each other.

By arranging the working electrode 32 and the counter electrode 34 in this manner, the sample liquid does not flow straight upward in the measurement channel section 222, but flows upward while meandering. Further, in the measurement flow path section 222, the sample liquid can be obliquely applied to the liquid contact surface 341 of the counter electrode 34 from the upstream side to the downstream side. As a result, a turbulent flow of the sample liquid is generated in the vicinity of the liquid contact surfaces 321 and 341 of the working electrode 32 and the counter electrode 34, and air bubbles generated on the sensor surface 321 are not accumulated and are efficiently flushed toward the outlet 22b. be able to.

In addition, the introduction channel portion 221 of the present embodiment is formed so that the sample liquid taken in from the introduction port 22a is directed vertically (including an angle close to the vertical) or obliquely to the liquid contact surface 321 of the working electrode 32. ing. Here, the introduction channel part 221 is formed so that the sample liquid taken in from the introduction port 22 a first flows upward, and then changes direction so that the liquid flows sideways, and the sample liquid hits the liquid contact surface 321 of the working electrode 32 . ing. By forming the introduction channel part 221 into such a shape, the flow of the sample liquid that collides with the liquid contact surface 321 of the working electrode 32 becomes turbulent, and bubbles generated on the liquid contact surface 321 can be efficiently washed away. . As a result, measurement accuracy can be further improved.

According to the electrochemical measurement apparatus 100 according to the present embodiment configured in this way, the working electrode 32 and the counter electrode 34 are brought close to each other so that part of the respective wetted surfaces 321 and 341 face each other. The influence of external electromagnetic noise transmitted to the electrodes 32 and 34 through the sample liquid can be reduced. In addition, since the liquid contact surface 321 of the working electrode 32 and the liquid contact surface 341 of the counter electrode 34 are arranged so as to be offset from each other along the direction in which the flow channel extends while partly facing each other. turbulence is generated in the flow of the working electrode 32, and air bubbles generated on the wetted surface 321 of the working electrode 32 can be discharged downstream without remaining.

The present invention is not limited to the above embodiments.

For example, although the fluid cutoff part 6 in the above embodiment was a roller pump, it is not limited to this. The fluid blocker 6 of other embodiments may be any device as long as it can completely block the flow of the sample liquid flowing through the introduction channel, and may be, for example, a diaphragm pump or an on-off valve. Also, the electrochemical measurement device 100 of another embodiment may not include the fluid blocker 6 on the sample channel 2 .

The electrochemical measurement device 100 of another embodiment may include a second counter electrode 3435 upstream of the working electrode 32 and the counter electrode 34 in the sensor channel 22, as shown in FIG. A boron-doped diamond electrode may be used as the second counter electrode 3435 in the same manner as the counter electrode 34 on the downstream side. For example, the second counter electrode 35 may be attached to the measurement cell 31 so that its wetted surface is in contact with the sample liquid flowing through the introduction channel section 221 .

In addition, in the electrochemical measurement device 100 of the above-described embodiment, the introduction channel part 221 is formed so that the sample liquid taken in from the introduction port 22a is applied vertically or obliquely toward the liquid contact surface 321 of the working electrode 32. However, it is not limited to this. In another embodiment, as shown in FIG. 6, the introduction channel part 221 may be formed so as to extend straight from bottom to top.

In addition, in the electrochemical measurement apparatus 100 of the above-described embodiment, the sample liquid is applied obliquely from the upstream side to the downstream side to the liquid contact surface 341 of the counter electrode 34 in the measurement channel section 222. It is not limited to this. In another embodiment, as shown in FIG. 7 , the measurement flow channel section 222 directs the sample liquid vertically (at an angle close to the vertical) to the liquid contact surface 341 of the counter electrode 34 from the upstream side to the downstream side. including).

Further, in the above-described embodiment, the working electrode 32 was provided so as to be located upstream of the counter electrode 34, but the present invention is not limited to this. In other embodiments, the counter electrode 34 may be provided upstream of the working electrode 32 .

Also, although the electrochemical measurement device 100 of the above embodiment is of a three-electrode type, it is not limited to this. Other embodiments of the electrochemical measurement device 100 may be bipolar, quadrupolar, hexapolar, or the like.

In the electrochemical measurement device 100 of another embodiment, the working electrode 32 is not limited to the boron-doped diamond electrode, but may be a conductive diamond electrode doped with a Group 13 or Group 15 element such as nitrogen or phosphorus. The working electrode 32 is not limited to a diamond electrode, and carbon electrodes containing carbon such as carbon electrodes, glassy carbon electrodes, diamond-like carbon electrodes, etc., noble metals such as gold and platinum, and alloys containing these noble metals are used. It may be an electrode or the like. Further, the reference electrode 33 in other embodiments is not limited to a silver/silver chloride electrode, and may be, for example, a standard hydrogen electrode, a mercury/mercury chloride electrode, a hydrogen palladium electrode, or the like. In addition, the counter electrode of other embodiments is not limited to the diamond electrode, and may be, for example, carbon, stainless steel, gold, silver, silver chloride, platinum, SnO ₂ or the like.

In addition, the substance to be measured in other embodiments is not limited to the residual chlorine described above, and may be other inorganic substances such as ozone, bromine, and hydrogen peroxide. In addition, the electrochemical measurement device 100 of another embodiment is not limited to the food field, but can be used for tap water, drinking water, water of rivers and marshes, industrial wastewater, industrial wastewater, laboratory reagents, night soil, sewage and sewage, medical reagents, It may be used for various sample solutions such as cooling water for air conditioning and leachate treatment.

In addition, it goes without saying that the present invention is not limited to the above-described embodiments, and that various modifications are possible without departing from the spirit of the present invention.

According to the present invention described above, in an electrochemical measurement device, it is possible to reduce the retention of air bubbles generated at the working electrode while reducing the influence of electromagnetic noise.

DESCRIPTION OF SYMBOLS 100... Electrochemical measuring apparatus 22... Sensor channel 32... Working electrode 321... Wetted surface (sensor surface)
34 Counter electrode 341 Wetted surface

Claims (10)

An electrochemical measuring device for electrochemically measuring the concentration of a substance to be measured contained in a sample liquid,
a channel through which the sample liquid flows;
A working electrode and a counter electrode each having a wetted surface contacting the sample liquid flowing in the channel,
An electrochemical measuring device, wherein the liquid contact surface of the working electrode and the liquid contact surface of the counter electrode are arranged such that they are displaced from each other along the direction in which the channel extends, and partly face each other. concave portions are formed at positions corresponding to the counter electrode and the working electrode on the inner wall surface forming the flow channel,
2. The electrochemical measurement apparatus according to claim 1, wherein the bottom surface of each recess is composed of the liquid contact surfaces of the working electrode and the counter electrode. the channel comprises a measurement channel portion facing the liquid contact surface of the working electrode and the liquid contact surface of the counter electrode;
The measurement flow path part applies the sample liquid perpendicularly or obliquely from the upstream side to the downstream side to the liquid-contacting surface of the working electrode and the counter electrode arranged on the downstream side. 3. The electrochemical measuring device according to claim 1, wherein a The electrochemical measurement apparatus according to any one of claims 1 to 3, wherein the channel is formed so that the sample liquid is applied perpendicularly or obliquely to the liquid contact surface of the working electrode. the measurement flow path portion is formed so as to flow the sample liquid upward;
The electrochemical measurement according to claim 3 or claim 4, wherein the liquid-contacting surface of the working electrode and the liquid-contacting surface of the counter electrode are displaced vertically along the measurement channel section. Device. further comprising a fluid blocking part capable of blocking the flow of the sample liquid upstream of the working electrode and the counter electrode in the channel;
6. The method according to any one of claims 1 to 5, wherein the concentration of the substance to be measured contained in the sample liquid is electrochemically measured while the flow of the sample liquid is blocked by the fluid blocking section. The electrochemical measurement device according to Item. The electrochemical measurement device according to claim 6, wherein the fluid cutoff part is a roller pump, a diaphragm pump, or an on-off valve. The electrochemical measurement device according to any one of claims 1 to 7, wherein a second counter electrode is provided upstream of the working electrode and the counter electrode in the channel. The electrochemical measurement device according to any one of claims 6 to 8, wherein the working electrode and the counter electrode are arranged in this order from upstream. An electrochemical measuring device comprising a channel through which a sample liquid flows, and a working electrode and a counter electrode having liquid-contacting surfaces in contact with the sample liquid flowing through the channel, is used to determine the concentration of a substance to be measured contained in the sample liquid. An electrochemical measurement method for electrochemically measuring,
An electrochemical measurement method in which the liquid-contacting surface of the working electrode and the liquid-contacting surface of the counter electrode are displaced from each other along the direction in which the channel extends, and are arranged so that part of them face each other.

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