JP2001174430A - Composite sensor for measuring concentration and ph of hypochlorous acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject composite sensor capable of miniaturizing an apparatus while simplifying a measuring circuit by making a reference electrode common and exerting no effect on a measured value even if a stray current is generated when a current is allowed to flow through the water in an electrolytic cell, preventing the generation of bacteria and the formation of slime or the generation of scale on the surface of an electrode at a time of the stagnation of water to be measured and capable of detecting the deterioration of the electrode. SOLUTION: The composite sensor for measuring the concentration and pH of hypochlorous acid is equipped with a measuring cell 7 arranged in a flow channel of a liquid to be measured, the acting electrode 1 for measuring the concentration of hypochlorous acid provided in the measuring cell 7, the counter electrode 3 of the acting electrode 1 provided in the measuring cell 7, the pH measuring hydrogen ion sensitive electrode 2 provided in the measuring cell 7 and the reference electrode 4 common to the acting electrode 1 and the hydrogen ion sensitive electrode 2 provided in the measuring cell 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the concentration of hypochlorous acid in a liquid to be measured by measuring a diffusion current accompanying a reduction reaction occurring near two electrodes,
The present invention relates to a composite sensor for measuring hypochlorous acid concentration and pH, which detects a highly accurate hypochlorous acid concentration by correcting a diffusion current value that changes under the influence of the above.

[0002]

2. Description of the Related Art Conventionally, hypochlorous acid contained in a liquid to be measured is electrolytically reduced using a working electrode provided in a flow path, and the concentration is continuously adjusted by utilizing the concentration dependence of a diffusion current value. Has been proposed. on the other hand,
It is said that the measured value of the concentration of hypochlorous acid is affected by pH and electric conductivity.
Hypochlorous acid which has a measuring means and an electric conductivity measuring means, separately measures an apparent concentration measured by a hypochlorous acid concentration meter, and corrects the obtained value with the values of pH and electric conductivity. An acid concentration measuring device has also been proposed.

[0003] As a conventional hypochlorous acid concentration measuring device, Japanese Patent Application Laid-Open No. 8-278282 (hereinafter referred to as “A”) has been proposed.
Discloses a "free chlorine measuring device".

[0004] A conventional hypochlorous acid concentration measuring device disclosed in Japanese Patent Application Laid-Open Publication No. H07-27139 will be described below with reference to the drawings.

FIG. 4 is a schematic diagram of a conventional hypochlorous acid concentration measuring device disclosed in Japanese Patent Publication No. A. In the figure, 1 is a working electrode made of platinum disposed in contact with the cylindrical filter 10, 3 is a counter electrode of the working electrode 1 made of silver / silver chloride, and 10 is a counter electrode 11 on the counter electrode 3 side and a working electrode. A cylindrical filter through which the liquid to be measured is connected, which is connected to the channel 13 on the first side; 11 is a counter electrode chamber in which the counter electrode 3 is provided; 12 is a power supply for applying a voltage between the working electrode 1 and the counter electrode 3 13 is a flow path of the liquid to be measured, and 14 is a water flow of the liquid to be measured flowing through the flow path 13.

With this configuration, the liquid to be measured is introduced into the counter electrode chamber 13 via the cylindrical filter 10 and the working electrode 1 and the counter electrode 3 are electrically connected. The concentration of free chlorine can be measured by contact, and the working electrode 1 is disposed in contact with the cylindrical filter 10, so that the structural strength of the device is increased and the working electrode 1 and the counter electrode 3 are arranged. Can be stabilized, and the stability of measurement accuracy can be enhanced.

[0007] As another hypochlorous acid concentration measuring device, a "residual chlorine concentration measuring device" is disclosed in JP-A-9-329577 (hereinafter referred to as "B").

A conventional hypochlorous acid concentration measuring device disclosed in Japanese Patent Application Laid-Open Publication No. H08-26136 will be described below with reference to the drawings.

FIG. 5 is a schematic diagram of a conventional hypochlorous acid concentration measuring device disclosed in Japanese Patent Application Publication No. 2002-110,197. In the figure, reference numeral 15 denotes a residual chlorine concentration meter for giving an apparent residual chlorine concentration, and 16 denotes a signal for calculating the residual chlorine concentration corrected based on the signals of the residual chlorine concentration meter 15, the pH meter 17, and the electric conductivity meter 18. A processing unit 17 for giving a pH of the test solution to the signal processing unit 16;
Reference numeral 18 denotes an electric conductivity meter for giving the electric conductivity of the test liquid to the signal processing unit 16.

With this configuration, the signal processing unit 16 can control the pH meter 17 and the pH meter 17 based on a correction curve for the pH dependency and the electrical conductivity dependency of the apparent residual chlorine concentration normalized to the true value of the residual chlorine concentration. The correction coefficient for the pH and the electric conductivity of the test liquid measured by the electric conductivity meter 18 is determined, and the apparent residual chlorine concentration of the test liquid measured by the residual chlorine concentration meter 15 is divided by the correction coefficient. The true residual chlorine can be calculated.

[0011]

However, the conventional hypochlorous acid concentration measuring device has the following problems.

(1) The purpose of the concentration measuring device disclosed in A is to provide high durability by improving the structural strength and to stabilize the positional relationship between the electrodes to perform highly accurate measurement. Since the concentration correction corresponding to the change in pH is not performed, there is a problem that it is necessary to separately provide a pH measuring means when used in an electrolyzed water generator or the like which changes the pH.

(2) The concentration measuring apparatus disclosed in the publication (b) corrects an apparent measured value in response to a change in pH or electric conductivity and requires a separate pH measuring means. When used in a water generator, it is necessary to provide a separate grounding means so that the stray current from the electrolytic cell does not affect the pH measurement. .

(3) In addition, when both the concentration measuring device of the publication A and the concentration measurement device of the publication B are used for a long period of time, contamination such as generation of bacteria in the measurement cell and adhesion of scale to the electrode is caused. However, there is a problem in that it is necessary to add a cleaning operation such as a cleaning operation of appropriately injecting a cleaning agent or a bactericide or a mechanical wiping of the electrode surface.

The present invention solves the above-mentioned conventional problems. By sharing a reference electrode which requires the largest volume, the apparatus can be reduced in size and the measuring circuit can be simplified. Even if a stray current occurs when the current is applied, it does not affect the measured value, the generation of bacteria that occurs when the measured water stays, the generation of slime by the polysaccharide based on it, and the deposition of calcium ions on the electrode surface It is an object of the present invention to provide a composite sensor for measuring the concentration and pH of hypochlorous acid with high stability and high accuracy of a measured value capable of preventing generation of scale and detecting deterioration of an electrode when the electrode is deteriorated.

[0016]

Means for Solving the Problems To solve the above problems, a composite sensor for measuring hypochlorous acid concentration and pH according to the present invention comprises a cell provided in a flow path of a liquid to be measured, and a cell provided inside the cell. Working electrode for measuring the concentration of hypochlorous acid, a counter electrode of the working electrode provided in the cell, a hydrogen ion sensitive electrode for measuring pH provided in the cell, and a working electrode provided in the cell And a reference electrode common to the hydrogen ion sensitive electrode.

[0017] This makes it possible to reduce the size of the apparatus and simplify the measurement circuit by using a common reference electrode requiring the largest volume, and to generate a stray current when a current flows in water such as an electrolytic cell. This does not affect the measured value, preventing the generation of bacteria that occur when the water to be measured stays and the generation of slime by the polysaccharide and the formation of scale on the electrode surface due to the deposition of calcium ions, and the deterioration of the electrode. In this case, it is possible to provide a composite sensor for measuring hypochlorous acid concentration and pH with high stability and high accuracy of the measured value that can detect the case.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A composite sensor for measuring hypochlorous acid concentration and pH according to claim 1 of the present invention comprises a cell provided in a flow path of a liquid to be measured and a cell provided in the cell. Working electrode for measuring chlorite concentration, counter electrode of working electrode provided in cell, hydrogen ion sensitive electrode provided for measuring pH provided in cell, working electrode provided in cell and hydrogen ion And a reference electrode common to the sensitive electrodes.

According to this configuration, the measuring unit for measuring the concentration of hypochlorous acid and the measuring unit for measuring pH are arranged in the same cell.
It is possible to use a common reference electrode, to reduce the size of the device and simplify the measurement circuit, and to prevent noise due to stray current.

According to a second aspect of the present invention, there is provided the composite sensor for measuring hypochlorous acid concentration and pH according to the first aspect, wherein the working electrode is any one of noble metals such as platinum, gold and silver. An ionic substance, wherein the hydrogen ion-sensitive electrode is formed of a planar or hemispherical alkali metal-containing glass, and the reference electrode is filled in a housing part separated from the working electrode and the counter electrode by a porous body. Formed from silver / silver chloride electrodes immersed in a highly concentrated solution of
It has a structure formed of at least one of corrosion-resistant metals such as titanium, gold, platinum, and silver.

With this configuration, in addition to the function of the first aspect,
It has the following functions.

(1) Since the electrode is formed of a stable material, the stability of measured values and the durability of the electrode can be improved.

(2) By using a common reference electrode, the volume of the storage section can be reduced, and the amount of ionic substance released from the liquid junction can be stabilized. The potential can be stabilized without the need to supply a substance.

Here, as the working electrode, a noble metal such as platinum or gold is preferably used. As the counter electrode, titanium or stainless steel having excellent corrosion resistance is preferably used,
In addition, a metal which is hardly corroded, such as gold or platinum, may be used. Further, as the hydrogen ion sensitive electrode, glass containing an alkali metal such as sodium, potassium, lithium and the like is preferably used.

As the reference electrode, a composite of silver and silver chloride is preferably used. The reference electrode plays a role of maintaining the stability of the potential between the reference electrode and the working electrode or between the reference electrode and the hydrogen ion-sensitive electrode by releasing a small amount of a high-concentration solution of the ionic substance filled in the storage section through the liquid junction. have.

According to a third aspect of the present invention, there is provided the composite sensor for measuring hypochlorous acid concentration and pH according to the first or second aspect, wherein the ionic substance is potassium chloride or sodium chloride. have.

According to this configuration, in addition to the function of the first or second aspect, the transport speed (transport number) of the positive ion and the negative ion by the ionic substance is substantially equal, so that the stability of the potential between the electrodes is more preferably maintained. It has the effect of being able to.

According to a fourth aspect of the present invention, there is provided the composite sensor for measuring hypochlorous acid concentration and pH according to any one of the first to third aspects, wherein the potentials of the working electrode and the counter electrode are inverted. A potential of 2.2 to 4.5 V is applied between the working electrode and the counter electrode, and a potential of 1.16 V or more is applied between the working electrode and the reference electrode.
It has a configuration with a power supply that applies for 15 seconds.

With this configuration, in addition to the function of any one of claims 1 to 3, the following function is provided.

(1) Hypochlorous acid can be generated even when the concentration of hypochlorous acid in the liquid to be measured is low, so that the electrodes and the porous body can be prevented from being deteriorated by microorganisms and organic substances. .

(2) Just by reversing the potentials of the working electrode and the counter electrode, it is possible to easily sterilize microorganisms and decompose organic substances using the time during which no measurement is performed, such as after the completion of measurement or between measurements. .

Here, the potential applied between the working electrode and the counter electrode is 2.2 to 4.5 V. 2.2V potential
If it is smaller than this, hypochlorous acid will not be generated, and there will be a tendency that the sterilizing power and the decomposition power of organic substances will be lost, and it will be 4.5.
When it is larger than V, the generation efficiency of hypochlorous acid decreases and the applied potential tends to be used as decomposition energy of water and heat generation.

The time for applying the potential is 5 to 5.
15 seconds. As the application time becomes shorter than 5 seconds, it tends to become difficult for hypochlorous acid to perform sufficient sterilization and decomposition of organic substances, and as the application time becomes longer than 15 seconds, the applied potential degrades water and Both tend to be used as exothermic energy and are therefore not preferred.

[0034] The invention according to claim 5 provides the invention according to claims 1 to 4.
A composite sensor for measuring hypochlorous acid concentration and pH of any one of the above, comprising resistance value measuring means for measuring a change in DC resistance or AC impedance of the hydrogen ion sensitive electrode and the reference electrode with respect to the counter electrode or working electrode. Configuration.

With this configuration, the following operation is obtained in addition to the operation of any one of the first to fourth aspects.

(1) Dirt and electrical / mechanical deterioration due to foreign substances adhering to the surface of the electrode or the porous body can be detected from the measured values of the DC resistance and the AC impedance. By applying a reversal potential between the working electrode and the counter electrode to generate hypochlorous acid, the foreign matter can be washed.

(2) When the electrode or the porous body is deteriorated to the extent that it cannot be completely cleaned even if hypochlorous acid is generated, the life can be detected by issuing a warning signal, and the life of the electrode or the porous body can be detected. The replacement time can be easily known.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic diagram of a composite sensor for measuring hypochlorous acid concentration and pH according to an embodiment of the present invention. In the figure, 1 is a working electrode made of platinum for measuring the concentration of hypochlorous acid in the liquid to be measured, and 2 is the direction of a surface which is disposed at a position where the water flow changes direction at an angle of about 45 ° and does not contact the liquid to be measured. Which has a silver / silver chloride electrode 5a and measures the pH of the solution to be measured filled with a pH buffer solution.
The hydrogen ion sensitive electrode made of i ₂ O—La ₂ O ₃ —Cs ₂ O—SiO ₂ has a donut shape made of stainless steel (SUS304) arranged at right angles to the water flow so as not to obstruct the water flow of the liquid to be measured. 4 is a reference electrode having a silver / silver chloride electrode 5b disposed in the vicinity of the hydrogen ion sensitive electrode 2 and having a storage section filled with a high concentration solution of an ionic substance, and 5a being a hydrogen ion sensitive electrode. A silver / silver chloride electrode 5b arranged in the direction of the surface of the electrode 2 which does not contact the liquid to be measured
Is a silver / silver chloride electrode arranged in the reference electrode 4, 6 is a liquid junction of a porous body made of a ceramic porous body that releases a very small amount of a high-concentration solution of an ionic substance from a housing portion of the reference electrode 4, and 7 is a cover. The measurement cell 8 disposed in the flow path of the measurement liquid is the working electrode 1
A composite power supply for applying a DC and AC potential between the
Is a changeover switch that can switch an electrode to which a voltage is applied.

In the present embodiment, a neutral phosphate buffer is used as a pH buffer, and a 3.3 M potassium chloride solution is used as a high-concentration solution of an ionic substance. Also,
A voltmeter (V ₁ ) for measuring the DC resistance or AC impedance between the hydrogen ion sensitive electrode 2 and the counter electrode 3 in the circuit
And a voltmeter (V ₂ ) for measuring DC resistance or AC impedance between the reference electrode 4 and the working electrode 1 and an ammeter (A).

The operation of the composite sensor for measuring the concentration of hypochlorous acid and the pH in the present embodiment configured as described above will be described below.

The measured liquid containing hypochlorous acid which has flowed into the measuring cell 7 at a constant flow rate has the hypochlorous acid reduced at the working electrode 1, and is provided between the working electrode 1 and the counter electrode 3 in proportion to the concentration of hypochlorous acid. The diffused current flows. Here, in a configuration using two electrodes of the working electrode 1 and the counter electrode 3, for example, in the concentration measuring device described in Japanese Patent Application Laid-Open No. H10-107, the potential between the electrodes changes with the change in electrical conductivity. Since it is difficult to obtain an accurate value from the liquid to be measured having a possibility that the conductivity may change, a separate electrical conductivity detecting unit may be separately provided as in the concentration measuring device of Japanese Patent Application Publication No. It is necessary to feed back the value of the electric conductivity as a correction value. Therefore, in order to easily obtain an accurate hypochlorous acid concentration, a three-electrode structure of the working electrode 1, the counter electrode 3, and the reference electrode 4 is required, and the potential of the working electrode 1 with respect to the reference electrode 4 is kept constant. Thus, a reproducible current value can be obtained.

Here, the storage portion provided inside the reference electrode 4 is filled with a solution of an ionic substance. Reference electrode 4
Has a contradictory problem that the potential is maintained as the amount of release from the liquid junction 6 increases, but the life is shortened, because the potential is maintained by releasing a small amount of ionic substance to the outside. For this reason, it is necessary to increase the volume of the storage section to increase the filling amount of the ionic substance, or to periodically supply the ionic substance. Therefore, in the present embodiment, in order to reduce the size of the storage unit and secure stable release of the ionic substance, the working electrode 1 and the counter electrode 3 as the hypochlorous acid concentration measurement unit and the hydrogen ion as the pH measurement unit are used. The sensitive electrode 2 is arranged in the same measuring cell 7 and the common reference electrode 4
It is possible to satisfy both the potential stability and the lifetime at the same time by using.

On the other hand, a potential corresponding to the hydrogen ion concentration of the liquid to be measured is generated on both surfaces of the hydrogen ion sensitive electrode 2. By connecting the silver / silver chloride electrode 5a on the hydrogen ion sensitive electrode 2 side and the silver / silver chloride electrode 5b in the reference electrode 4, this potential can be taken out, and the pH of the liquid to be measured can be measured.

In order to continuously measure the pH and the concentration of hypochlorous acid in the liquid to be measured for several years while maintaining high accuracy,
It is necessary to keep the electrodes such as the working electrode 1, the hydrogen ion sensitive electrode 2 and the counter electrode 3 and the surface of the liquid junction 6 always clean. The deterioration of the electrodes and the liquid junction 6 is often caused by the propagation of microorganisms and the attachment of a slime-like substance called extracellular polysaccharide produced by the microorganisms. Is often contaminated while the liquid to be measured remains in the sensor. Therefore, the working electrode 1 and the counter electrode 3 are periodically used by using the time when the sensor is not used.
By applying a potential from the power supply 8 during the process to generate hypochlorous acid from chloride ions contained in the liquid to be measured, it is possible to sterilize microorganisms and decompose organic substances such as extracellular polysaccharides. . Here, the potential required for generation of hypochlorous acid is 1.16 V with respect to the silver / silver chloride electrode 5a.
If a potential of 1.16 V or more is applied for a certain period of time, hypochlorous acid can be efficiently generated, and each electrode and liquid junction 6
Can be washed.

On the other hand, in order to evaluate the sterilization performance and the degree of decomposition of organic substances, the DC resistance or AC impedance between the electrodes is measured using voltmeters V ₁ and V ₂ , and each electrode or liquid junction 6 is measured.
By monitoring the increase in resistance value due to contamination such as the adhesion of foreign substances on the surface, the timing for generating hypochlorous acid can be controlled. Specifically, the counter electrode 3
Silver / silver chloride electrode 5a on the hydrogen ion sensitive electrode 2 side
By measuring the impedance of 1 kHz, it is possible to detect the deterioration of the surface of the hydrogen ion sensitive electrode 2 and the surface of the counter electrode 3 due to the adhesion of foreign matter. Further, by measuring the 1 kHz impedance of the silver / silver chloride electrode 5 b in the reference electrode 4 with respect to the counter electrode 3, it is possible to detect the abnormal release of the ionic substance due to the adhesion of the foreign matter to the liquid junction 6. Further, by measuring the impedance of the working electrode 1 at 1 KHz with respect to the counter electrode 3, it is possible to detect the deterioration of the surface of the working electrode 1 due to the adhesion of foreign matter. These measurements can be continuously performed by switching the changeover switch 9 to the hydrogen ion sensitive electrode 2 side and the working electrode 1.

When the measured values are abnormal, the power supply 8 applies a potential of 1.16 V or more between the counter electrode 3 and the working electrode 1 to generate hypochlorous acid, thereby causing the electrodes and the liquid junction 6 The surface can be cleaned. If the value of the impedance does not improve even if hypochlorous acid is generated, the life of each electrode or the liquid junction 6 is detected by a warning signal to notify the replacement time.

FIG. 2 is a graph showing a change in impedance when the sensor is continuously used and when an inverted potential of 1.5 V is applied. In the figure, the horizontal axis represents the elapsed time,
The vertical axis represents the degree of change in impedance. In FIG. 2, the degree of change in impedance indicates the degree of regeneration of the liquid junction 6, and the reference value for the degree of regeneration is 2. FIG. 2 shows that the impedance continues to rise when the sensor is continuously used, but returns to the original value when the inversion potential is applied intermittently. In addition, when the application time of the inversion potential is 4 seconds, the reference value 2 which is the determination criterion that cannot be completely returned to the original state and is set.
However, when the application time is 5 seconds or longer, the reference value 2 is not exceeded.

The correction based on the change in the electrical conductivity of hypochlorous acid can be solved by providing the reference electrode 4, while p
Assuming that the equilibrium constant of (1) is K ₁ and the equilibrium constant of (2) is K ₂ , the existence form of hypochlorous acid due to the change of H is given by
It is represented as

[0050]

(Equation 1)

Here, in (Equation 1), the equilibrium constant at a temperature of 20 ° C. is expressed by (Equation 2) and (Equation 3).

[0052]

(Equation 2)

[0053]

(Equation 3)

The equilibrium is determined by the hydrogen ion concentration [H ⁺ ] (=
It depends on ^- pH) and chloride ion concentration [Cl].

FIG. 3 shows that the chloride ion concentration was 1.000 pp.
It is a graph which shows the existence ratio of hypochlorous acid (HOCl) with respect to hydrogen ion concentration [pH] in case of m. In the figure, the horizontal axis represents the hydrogen ion concentration [pH], and the vertical axis represents the proportion of hypochlorous acid (HOCl) to the pH. In FIG. 3, the lower limit of the pH is 1.77. According to FIG.
But due to change, hypochlorite, OCl ^- → HOC
It can be seen that 1 → Cl ₂ changes. Here, since the measurement target of the sensor is hypochlorous acid, the reduction potential of the working electrode 1 is fixed to the reduction potential of hypochlorous acid. On the other hand, since the oxidizing power is strong in the order of Cl ₂ >HOCl> OCl ⁻ , the pH value is also necessary for knowing the bactericidal effect and the oxidative decomposition effect of organic substances. Therefore, particularly in an electrolytic water generator that electrolyzes a thin saline solution to produce water containing hypochlorous acid,
It is important to indicate both the hypochlorous acid concentration and the pH. However, there is no point in correcting the concentration of hypochlorous acid with pH.

As described above, the composite sensor for measuring hypochlorous acid concentration and pH according to the present embodiment has the following functions.

(1) Since the working electrode, the counter electrode, and the hydrogen ion sensitive electrode are arranged in the same cell and the reference electrode is shared, the size of the reference electrode can be reduced and the amount of ionic substance released can be stabilized. Can be changed.

(2) Further, there is no need to periodically supply an ionic substance, and the size and cost of the apparatus can be reduced.

(3) Hypochlorous acid can be generated by inverting and applying the potentials of the working electrode and the counter electrode using the time when the sensor is not used. Propagation of microorganisms and the occurrence of slimming due to organic matter can be prevented.

(4) Since the DC resistance or AC impedance between the electrodes can be measured, the degree of contamination of the electrodes and the surface of the liquid junction can be easily known, and the timing and potential for generating hypochlorous acid. Can be controlled.

[0061]

As described above, according to the composite sensor for measuring hypochlorous acid concentration and pH of the present invention, the following advantageous effects can be obtained.

According to the first aspect of the present invention, since the measuring unit for measuring the concentration of hypochlorous acid and the measuring unit for measuring pH are arranged in the same cell, a common reference electrode can be used, and the size of the apparatus can be reduced. Thus, it is possible to provide a high-performance composite sensor for hypochlorite concentration preliminary pH measurement with a simple configuration capable of simplifying the configuration and the measurement circuit and preventing noise due to stray current.

According to the second aspect of the invention, in addition to the effects of the first aspect, (1) Since the electrode is formed of a stable material, the stability of measured values and the durability of the electrode can be improved. A composite sensor for chloric acid concentration preliminary pH measurement can be provided.

(2) By using a common reference electrode, the volume of the reference electrode can be reduced, and the amount of ionic substances released from the liquid junction can be stabilized.
It is possible to provide a compact and highly accurate hypochlorous acid concentration preliminary pH measurement composite sensor that can stabilize the potential without having to supply an ionic substance periodically.

According to the invention of claim 3, claim 1 or 2
In addition to the effect of the above, since the transport speed (transport number) of the positive ion and the negative ion by the ionic substance is almost equal, the concentration of hypochlorous acid with high measurement accuracy that can keep the potential stability between the electrodes more suitable and A composite sensor for measuring pH can be provided.

According to the invention of claim 4, claims 1 to 3 are provided.
(1) Hypochlorous acid can be generated even when the concentration of hypochlorous acid in the liquid to be measured is low, so that the electrode is prevented from being deteriorated by microorganisms or organic substances. A long-life composite sensor for measuring hypochlorous acid concentration and pH that can be provided.

(2) Just by reversing the potentials of the working electrode and the counter electrode, it is possible to easily sterilize microorganisms and decompose organic substances by using the time during which measurement is not performed, such as after the completion of measurement or between measurements. Further, it is possible to provide a composite sensor for measuring hypochlorous acid concentration and pH which can efficiently and cleanly maintain electrodes and liquid junctions.

According to the invention of claim 5, claims 1 to 4
In addition to the effects of any one of the above, (1) Dirt or electrical or
Since mechanical deterioration can be detected, if there is an abnormality, the measured value has a long service life that can apply a reversal potential between the working electrode and the counter electrode to generate hypochlorous acid and clean foreign substances. A composite sensor for measuring hypochlorous acid concentration and pH excellent in stability can be provided.

(2) If the electrode or liquid junction is deteriorated to such an extent that it cannot be completely cleaned even if hypochlorous acid is generated, the life can be detected by issuing a warning signal. Can be provided, and a composite sensor for measuring hypochlorous acid concentration and pH with high measurement accuracy can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a composite sensor for measuring hypochlorous acid concentration and pH according to an embodiment of the present invention.

FIG. 2 When the sensor is continuously used and 1.5 V
Graph showing the change in impedance when an inversion potential is applied

FIG. 3 is a graph showing the proportion of hypochlorous acid to hydrogen ion concentration.

FIG. 4 is a schematic diagram of a hypochlorous acid concentration measuring device disclosed in JP-A No.

FIG. 5 is a schematic diagram of a hypochlorous acid concentration measuring device disclosed in B

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Working electrode 2 Hydrogen ion sensitive electrode 3 Counter electrode 4 Reference electrode 5a, 5b Silver / silver chloride electrode 6 Liquid junction 7 Measurement cell 8 Composite power supply 9 Changeover switch 10 Cylindrical filter 11 Counter electrode room 12 Power supply 13 Flow path 14 Water flow 15 Residual chlorine Concentration meter 16 Signal processing unit 17 pH meter 18 Electric conductivity meter

Claims (5)

[Claims] 1. A cell disposed in a flow path of a liquid to be measured, and a working electrode provided in the cell for measuring the concentration of hypochlorous acid,
A counter electrode of the working electrode provided in the cell, a hydrogen ion sensitive electrode for measuring pH provided in the cell, and a common electrode for the working electrode and the hydrogen ion sensitive electrode provided in the cell. A composite sensor for measuring hypochlorous acid concentration and pH, comprising: a reference electrode. 2. The working electrode is formed of one or more noble metals such as platinum, gold and silver, and / or the hydrogen ion sensitive electrode is formed of a planar or hemispherical alkali metal-containing glass, And / or the reference electrode is immersed in a high-concentration solution of an ionic substance filled in a storage portion separated from the working electrode and the counter electrode by a porous body.
2. The sub-sub-electrode according to claim 1, wherein the electrode is formed of a silver chloride electrode, and / or the counter electrode is formed of at least one of a corrosion-resistant metal such as stainless steel, titanium, gold, platinum, and silver. Composite sensor for chloric acid concentration and pH measurement. 3. The composite sensor for measuring hypochlorous acid concentration and pH according to claim 1, wherein the ionic substance is potassium chloride or sodium chloride. 4. After inverting the potentials of said working electrode and said counter electrode, a potential of 2.2 to 4.5 V is applied between said working electrode and said counter electrode, and 1 potential is applied between said working electrode and said reference electrode. The composite sensor for measuring hypochlorous acid concentration and pH according to any one of claims 1 to 3, further comprising a power supply for applying a potential of 16 V or more for 5 to 15 seconds. 5. The apparatus according to claim 1, further comprising resistance value measuring means for measuring a change in DC resistance or AC impedance of said hydrogen ion sensitive electrode and said reference electrode with respect to said counter electrode or said working electrode. The composite sensor for measuring hypochlorous acid concentration and pH according to any one of the above.