JP2000121605A - Reagent-free type apparatus for measuring concentration of oxidation-reduction substance, and its measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reagent-free type apparatus for measuring the concentration of oxidation-reduction substance capable of easily and stably measuring an oxidation-reduction current even if the flow condition of a liquid to be measured fluctuates. SOLUTION: This reagent-free type apparatus for measuring the concentration of oxidation- reduction substance is provided with a detection electrode 2 submergedly installed in a flow-in liquid to be measured; a counter electrode 3 formed with a material different from that of the detection electrode 2; a third electrode 4 disposed to be opposed to the counter electrode 3 across the flow of the liquid to be measured and formed of the same material as that of the counter electrode 3; a magnetic field generator 5 generating a magnetic field vertically to a flow-in direction of the liquid to be measured and to a direction which connects the counter electrode 3 and the third electrode 4; and a current detector 6 connected with the counter electrode 3 and detecting a current or voltage between the detection electrode 2 and the counter electrode 3 to which a current or voltage, generated by the magnetic field generator 5, between the counter electrode 3 and the third electrode 4 is overlapped. The apparatus is constituted to correct the current or voltage between the detection electrode 2 and the counter electrode 3, which fluctuates according to the flow velocity of the liquid to be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for determining the concentration of a component to be measured contained in a liquid to be measured by an oxidation-reduction reaction at a detection electrode. The present invention relates to a redox substance concentration measuring device and a measuring method with improved detection accuracy.

[0002]

2. Description of the Related Art In recent years, components to be measured contained in a liquid to be measured are electrolytically oxidized or reduced by using a detection electrode provided in a flow path, and the concentration is continuously controlled by utilizing the concentration dependence of a current value flowing at that time. Various devices have been developed for measurement.

[0003] Japanese Patent Application Laid-Open No. 8-278284 (hereinafter referred to as “A”) discloses a sample liquid flow path inside a cylindrical filter.
Forming a counter electrode chamber on the outside and increasing the structural strength of the device by placing the detection electrode in contact with the filter in the sample liquid flow path,
In addition, a measurement device is disclosed which is configured to stabilize the positional relationship between the detection electrode and the counter electrode, thereby improving the stability of measurement accuracy.

[0004]

However, the conventional measuring device and measuring method have the following problems.

[0005] The measuring device described in Japanese Patent Application Laid-Open Publication No. H07-27139 aims to provide high durability by improving the structural strength and to stabilize the positional relationship between the electrodes. When the flow rate of the liquid to be measured changes, the oxidation-reduction current value between the electrodes also changes, so that the concentration of the target substance in the liquid to be measured must be continuously and stably measured. Therefore, it is necessary to add a mechanism such as a flow rate adjusting valve in order to regulate the flow rate to a constant value, and the change in the flow rate of the liquid to be measured cannot be corrected.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and is a non-reagent type redox substance concentration measurement method capable of easily and constantly measuring an oxidation-reduction current value even when the flow state of a liquid to be measured changes. An object is to provide an apparatus and a measurement method.

[0007]

In order to achieve this object, a reagent-free type redox substance concentration measuring apparatus and measuring method of the present invention have the following constitution.

According to the present invention, there is provided a non-reagent type redox substance concentration measuring apparatus, comprising: a detection electrode immersed and arranged in a liquid to be measured; a counter electrode formed of a material different from the detection electrode; It is arranged at a position facing the counter electrode across the flow,
A third electrode formed of the same material as the counter electrode, and a magnetic field generator that generates a magnetic field perpendicular to the inflow direction of the liquid to be measured and the direction in which the counter electrode is connected to the third electrode;
A current detector connected to the counter electrode and detecting a current or voltage between the detection electrode and the counter electrode on which a current or voltage formed between the counter electrode and the third electrode by the magnetic field generator is superimposed; And the current or voltage between the detection electrode and the counter electrode, which fluctuates according to the flow rate of the liquid to be measured, is corrected.

With this configuration, the current value or the voltage value of the detection electrode, which changes due to the fluctuation of the flow rate of the liquid to be measured, can be corrected by the current value or the voltage value that changes by the magnetic field generator and the third electrode. This has the effect that a stable redox substance concentration can be measured accurately and stably without using any reagent.

[0010] In the method for measuring the concentration of a redox substance without a reagent according to the present invention, the concentration of the redox substance based on the current value or the voltage value of the detection electrode and the counter electrode may be determined by measuring the current between the counter electrode and the third electrode. Alternatively, the flow rate is corrected by the voltage value.

According to this configuration, the flow rate variation of the oxidation-reduction current of the liquid to be measured detected between the detection electrode and the counter electrode is determined by the current value or the voltage value between the counter electrode and the third electrode induced by the magnetic field generator. This has the effect that the measured current of the substance to be measured can be corrected in accordance with the fluctuation of the flow rate of the liquid to be measured.

[0012]

According to a first aspect of the present invention, there is provided an apparatus for measuring a concentration of a redox substance without a reagent, wherein the detection electrode is immersed in the liquid to be measured and a counter electrode formed of a material different from the detection electrode. A third electrode disposed at a position facing the counter electrode across the flow of the liquid to be measured, and a third electrode formed of the same type of material as the counter electrode; and a flowing direction of the liquid to be measured and the counter electrode and the third electrode. A magnetic field generator that generates a magnetic field perpendicular to the direction in which the three electrodes are connected; and a current or voltage that is connected to the counter electrode and that is formed between the counter electrode and the third electrode by the magnetic field generator. A current detector that detects a current or a voltage between the superposed detection electrode and the counter electrode, and has a configuration for correcting a current or a voltage between the detection electrode and the counter electrode that fluctuates according to a flow rate of the liquid to be measured. are doing.

Thus, the oxidation-reduction current of the liquid to be measured, which is detected between the detection electrode and the counter electrode, is changed by the current or voltage between the counter electrode and the third electrode induced by the magnetic field generating section to change the flow rate of the liquid to be measured. This has the effect that the measured current or voltage of the substance to be measured can be corrected accordingly.

Here, the material of the detection electrode is platinum,
Solid electrodes of gold, carbon and glassy carbon are used.

As the material of the counter electrode and the third electrode, solid electrodes of silver, silver chloride, stainless steel, platinum, carbon, and glassy carbon are used.

According to a second aspect of the present invention, there is provided a reagent-free type redox substance concentration measuring apparatus, wherein the magnetic field generating section is a permanent magnet or an electromagnet.

Thus, in addition to the effect obtained in the first aspect, there is an effect that a correction current corresponding to the flow rate can be formed between the counter electrode and the third electrode by the permanent magnet or the electromagnet.

[0018] Here, permanent magnets include magnetite, giruite ore, nickel ore, carbon steel, tungsten steel, K
S steel, cobalt steel, MT steel, chrome steel, and alnico are used.

As the electromagnet, a magnet which generates a magnetic field by passing an electric current through a coil wound around a ferromagnetic material such as pure iron, structural carbon steel, cast steel, and silicon steel plate is used.

According to a third aspect of the present invention, there is provided a reagent-free type redox substance concentration measuring apparatus according to any one of the first or second aspects, wherein the redox substance is residual chlorine. I have.

Thus, in addition to the effect obtained by any one of the first and second aspects, the present invention has the effect of accurately detecting residual chlorine contained in the liquid to be measured.

Here, the residual chlorine includes chlorine, chloric acid, hypochlorous acid, chlorine dioxide, chlorous acid, chloramine and the like.

The method of measuring a concentration of a redox substance without a reagent according to claim 4, wherein the concentration of the redox substance based on the current or voltage value of the detection electrode and the counter electrode is determined by measuring the current between the counter electrode and the third electrode. Alternatively, the flow rate is corrected by the voltage value.

Thus, the flow rate variation of the oxidation-reduction current of the liquid to be measured detected between the detection electrode and the counter electrode is corrected by the current or voltage between the counter electrode and the third electrode induced by the magnetic field generator, This has the effect that the measured current or voltage of the substance to be measured can be corrected according to the flow rate fluctuation of the liquid to be measured.

According to a fifth aspect of the present invention, in the method for measuring a concentration of a reagentless redox substance according to the fourth aspect of the present invention, the counter electrode and the counter electrode are arranged in a direction of current generated by an electrode reaction between the detection electrode and the counter electrode. The direction of current generated by the flow rate between the third electrodes provided opposite to each other is opposite, and the magnetic field generation unit is arranged such that the current gradients due to both flow rates are the same. The flow rate is corrected by canceling the current between the counter electrode and the reverse current between the counter electrode and the third electrode.

According to this, in addition to the function obtained by the fourth aspect, the flow rate variation of the oxidation-reduction current of the liquid to be measured detected between the detection electrode and the counter electrode can be calculated by using the counter electrode induced by the magnetic field generator and the third electrode. This has the effect of canceling out the current between them and correcting the measured current of the substance to be measured according to the fluctuation of the flow rate of the liquid to be measured.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment) FIG. 1 is a diagram showing an outline of a reagentless redox substance concentration measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a cross section taken along line AA of FIG. 1, and FIG. 3 is a diagram showing the principle of wiring between electrodes constituting a reagentless redox substance concentration measuring device.

1 to 3, reference numeral 1 denotes a conduit through which a liquid to be measured flows, 2 denotes a detection electrode for detecting a substance to be measured by an electrode reaction of the liquid to be measured, and 3 denotes a detection electrode 2 which is electrically connected. A counter electrode 4 made of a different kind of material; a third electrode disposed at a position facing the counter electrode 3 with respect to the flow direction Q;
Reference numeral 5 denotes a magnetic field generator including a permanent magnet or an electromagnet provided with the conduit 1 interposed therebetween at a position orthogonal to the flow direction Q and the counter electrode 3 and the third electrode 4, and 6 denotes a detection electrode 2 And a current detector that superimposes and measures an oxidation-reduction current generated by an electrode reaction between the counter electrode 3 and a current induced by the magnetic field generator between the counter electrode 3 and the third electrode 4.

In FIG. 1, a detection electrode 2 and a counter electrode 3 for detecting a substance to be measured by an electrode reaction of the liquid to be measured are arranged along a pipe 1 through which the liquid to be measured flows. A third electrode 4 is provided at a position facing the counter electrode 3 with respect to Q so as to come into contact with the liquid to be measured in the pipeline 1. Further, a magnetic field generator 5 is provided at a position orthogonal to the flow direction Q and the counter electrode 3 and the third electrode 4 with the conduit 1 interposed therebetween.

The detection electrode 2 and the counter electrode 3 are made of different kinds of materials, and the detection electrode 2 and the counter electrode 3 are electrically connected. The redox current generated by the electrode reaction of the detection electrode 2 can be measured by bringing the liquid into direct contact with the detection electrode 2, and the target substance contained in the liquid to be measured is determined by utilizing the concentration dependence of the current value or voltage value flowing at that time. Can be measured.

The detection electrode is made of a solid electrode such as platinum, gold, or carbon, while the counter electrode is made of a solid electrode made of silver, silver chloride, stainless steel, or the like, and uses the voltage difference generated between the two electrodes. Then, the target substance in the liquid to be measured is electrolytically oxidized or reduced on the detection electrode, and the oxidation or reduction current value or voltage value generated at this time is measured, and the current or voltage value is incorporated in the current detector. The arithmetic circuit thus configured can display the concentration of the target substance. However, the material and combination of the detection electrode and the counter electrode are not particularly limited as long as they are materials having a configuration for obtaining an oxidation-reduction current.

In FIG. 2, the third electrode 4 is made of the same material as the counter electrode 3, so that no voltage difference occurs, but the third electrode 4 is located at a position orthogonal to the flow path direction Q and the magnetic field generator 5. Since they are arranged and electrically connected to each other, the third
An electromotive force is generated between the electrode 4 and the counter electrode 3 according to the flow rate of the liquid to be measured. At this time, the magnetic field generator 5 is configured so that the direction of the current between the electrodes due to the flow rate of the liquid to be measured is opposite to the direction of the current between the detection electrode 2 and the counter electrode 3, and the tube 1 is sandwiched therebetween. An N pole and an S pole are respectively arranged facing each other.

If the detection electrode 2, the counter electrode 3, and the third electrode 4 are integrated and arranged so as to be connected to each other, the detection electrode 2, the counter electrode 3, and the third electrode 4 Are connected electrically to each other, the direction of current flowing due to the voltage difference generated between the detection electrode and the counter electrode is only between the detection electrode and the counter electrode. Does not flow, while the current flowing due to the electromotive force generated by the flow velocity of the liquid to be measured and the magnetic field flows only between the counter electrode 3 and the third electrode 4, and the current flows in the direction of the detection electrode. It will not be.

Incidentally, the oxidation-reduction current flowing between the detection electrode 2 and the counter electrode 3 is a current value due to an oxidation or reduction reaction that occurs when the target substance reacts on the detection electrode according to the flow rate of the liquid to be measured flowing in the pipe. Alternatively, since the voltage value changes, the current has a current gradient with respect to the flow velocity. At this time, a current detector 6 is provided at the counter electrode 3 as shown in FIG. 3, and the detected current value is taken as the inflow / outflow current of the counter electrode 3, between the counter electrode 3 and the third electrode 4 by the magnetic field generator. Since the current gradient of the generated current can be adjusted in proportion to the magnetic field strength, the detection electrode 2 and the counter electrode 3
By giving the magnetic field strength so as to be the same as the current gradient generated according to the flow velocity generated between them, the current values fluctuating according to the flow velocity of the liquid to be measured can be superimposed and cancel each other, and the current values fluctuate due to the flow fluctuation. Since the current value can be corrected, a constant current value can be measured regardless of the flow rate fluctuation.

Therefore, the detection pole 2, the counter electrode 3, and the third
Are electrically connected to each other, and an electrode current corresponding to the target substance of the liquid to be measured is detected by a current detector 6 provided on the counter electrode 3, and this current value is converted to a concentration of the target substance by the current detector. By converting and displaying, even if the flow rate of the liquid to be measured fluctuates, by measuring the inflow / outflow current of the counter electrode, the current value due to the fluctuation can be automatically canceled and corrected. It is possible to continuously and stably measure the concentration of the residual chlorine or the like as the redox substance in the liquid to be measured, and it is possible to perform highly accurate measurement.

Furthermore, the induced current between the counter electrode 3 and the third electrode 4 generated by the flow velocity and the magnetic field in the pipe changes depending on the diameter of the pipe, so that it is necessary to adjust the magnetic field strength. If the generator 5 is a device having a constant pipe diameter, the magnetic field can be adjusted by selecting a permanent magnet capable of generating the same current gradient as the current gradient due to the flow velocity in the pipe.

In the above description, an example has been described in which the magnetic field generator 5 uses a permanent magnet. However, the magnetic field generator 5 can be similarly implemented using an electromagnet. In the case of an electromagnet, by providing means for adjusting the flowing current in the circuit, the magnetic field strength can be adjusted to have the same current gradient.

According to the embodiment of the present invention, a reagentless redox substance concentration measuring apparatus and a measuring method capable of easily and constantly measuring an oxidation-reduction current value even when the flow state of a liquid to be measured changes. Can be provided.

[0039]

EXAMPLES (Example 1) As an example, an experiment for confirming residual chlorine was carried out using the reagentless redox substance concentration measuring apparatus of the embodiment. The measurement results are shown in FIG. FIG. 4 is a diagram showing the measurement of residual chlorine using the reagentless redox substance concentration measuring apparatus of the present embodiment.

The figure shows the reduction current value of residual chlorine contained in the liquid to be measured detected only between the detection electrode and the counter electrode. As the flow rate Q of the liquid to be measured increases, the reduction current value increases with a constant gradient (+ α).

On the other hand, a magnetic field is generated only by the counter electrode 3 and the third electrode 4, and the magnetic field intensity is adjusted so that the gradient (-α) is opposite to the gradient (α) indicated. The induced current based on the obtained flow rate is shown in the figure.

With the above arrangement, the detection electrode 2, the counter electrode 3, and the third electrode 4 were arranged so as to be connected to each other, and detected as the inflow / outflow current value at the counter electrode 3, and the straight line data in the figure was obtained.

The reduction current value fluctuating according to the flow rate of the liquid to be measured can be automatically corrected by the current value of the liquid to be measured, and a stable reduction current value i can be measured. The concentration can be measured accurately.

(Comparative Example 1) An experiment for confirming residual chlorine was conducted using a conventional reagentless redox substance concentration measuring apparatus. The measurement results are shown in FIG. FIG. 5 is a measurement diagram of residual chlorine using a conventional reagentless redox substance concentration measuring device.

The reduction current values of residual chlorine contained in the liquid to be measured detected only between the detection electrode and the counter electrode are shown in FIG.

Here, 〜 indicates that the residual chlorine concentration in each liquid to be measured is different. For each sample, the flow rate Q
There was a constant gradient (α) with the increase in, and the measured current value changed depending on the flow rate.

Therefore, in the electrode pair configured here, it is necessary to measure the residual chlorine concentration by defining a constant flow rate Q and measuring the reduction current value i.

As described above, according to the embodiment, even if the flow state of the liquid to be measured changes, the oxidation-reduction substance concentration measuring apparatus and the reagent can be measured easily and constantly stably. It is clear that can be provided.

[0049]

As described above, according to the present invention, the following excellent effects can be realized.

According to the first aspect of the present invention,
(1) The oxidation-reduction current of the liquid to be measured detected between the detection electrode and the counter electrode is changed according to the flow rate fluctuation of the liquid to be measured by the current between the counter electrode and the third electrode induced by the magnetic field generating unit with a simple structure. Thus, the measured current of the substance to be measured can be automatically corrected.

According to the second aspect of the present invention,
In addition to the effect of the first aspect, (2) a correction current corresponding to the flow rate can be formed between the counter electrode and the third electrode by the permanent magnet or the electromagnet.

According to the third aspect of the present invention,
In addition to the effect described in any one of claims 1 and 2, (3) residual chlorine contained in the liquid to be measured can be detected with high accuracy.

According to the fourth aspect of the present invention,
(4) The flow rate variation of the oxidation-reduction current of the liquid to be measured detected between the detection electrode and the counter electrode is corrected by the current between the counter electrode and the third electrode induced by the magnetic field generator, and the flow rate of the liquid to be measured is corrected. The measured current of the substance to be measured can be corrected according to the fluctuation, and the concentration of the redox substance can be measured continuously without using any reagent.
Measurement accuracy can be improved.

According to the fifth aspect of the present invention,
In addition to the effect of the fourth aspect, (5) the flow rate variation of the oxidation-reduction current of the liquid to be measured detected between the detection electrode and the counter electrode may be calculated between the counter electrode and the third electrode induced by the magnetic field generator. The measurement current of the substance to be measured can be corrected according to the fluctuation of the flow rate of the liquid to be measured, offset by the current.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of an apparatus for measuring the concentration of a redox substance according to an embodiment of the present invention.

FIG. 2 is a diagram showing a cross section taken along line AA of FIG. 1;

FIG. 3 is a diagram showing the principle of wiring between electrodes constituting the redox substance concentration measuring device.

FIG. 4 is a view showing the measurement of residual chlorine using the reagentless redox substance concentration measuring apparatus according to the embodiment.

FIG. 5 is a measurement diagram of residual chlorine using a conventional reagentless redox substance concentration measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipeline 2 Detection pole 3 Counter electrode 4 Third electrode 5 Magnetic field generator 6 Current detector Q Flow direction of liquid to be measured

Claims (5)

[Claims] A detection electrode immersed in the liquid to be measured, a counter electrode formed of a material different from the detection electrode, and a detection electrode disposed at a position facing the counter electrode with the flow of the liquid to be measured interposed therebetween. A third electrode formed of the same material as the counter electrode; and a magnetic field generator that generates a magnetic field perpendicular to the inflow direction of the liquid to be measured and the direction in which the counter electrode is connected to the third electrode. A current detection device that is connected to the counter electrode and detects a current or voltage between the detection electrode and the counter electrode on which a current or voltage formed between the counter electrode and the third electrode is superimposed by the magnetic field generator. A non-reagent-type redox substance concentration measuring device, comprising: a device for correcting a current or a voltage between the detection electrode and the counter electrode, which fluctuates according to a flow rate of the liquid to be measured. 2. The apparatus according to claim 1, wherein the magnetic field generator is a permanent magnet or an electromagnet. 3. The reagentless redox substance concentration measuring device according to claim 1, wherein the redox substance is residual chlorine. 4. The method according to claim 1, wherein a flow rate of the liquid to be measured is corrected by a current or voltage value between the counter electrode and the third electrode based on a current or voltage value between the detection electrode and the counter electrode. For measuring the concentration of a reagentless redox substance. 5. A current direction generated by the flow rate between the third electrode provided opposite to the counter electrode is opposite to a current direction generated by an electrode reaction between the detection electrode and the counter electrode, and The magnetic field generating unit is arranged such that current gradients due to both flow rates are the same, and a current between the detection electrode and the counter electrode is offset by a reverse current between the counter electrode and the third electrode. The method for measuring the concentration of a reagentless redox substance according to claim 4, wherein the flow rate is corrected by: