JP2023093068A - Device, method, and program for measuring ion concentration - Google Patents

Abstract

To provide an ion concentration measuring device that can measure an ion concentration more precisely and with a simpler configuration.SOLUTION: The ion concentration measuring device includes: a work electrode for outputting a measurement potential according to the ion concentration included in a sample liquid; a comparison electrode for outputting a reference potential to the measurement potential output from the work electrode; a resistance value measurement unit for measuring a resistance value of the sample liquid; and a calculation unit for calculating an ion concentration on the basis of a potential difference between the work electrode and the comparison electrode and the resistance value.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ion concentration measuring device, an ion concentration measuring method, and an ion concentration measuring program for measuring the concentration of ions contained in a sample liquid.

In the ion concentration measurement, an error may occur in the measured value depending on the electric conductivity of the sample liquid to be measured.
As a method for reducing the influence of the electrical conductivity of the sample liquid on the measured value, as described in Patent Document 1, a conductivity meter that measures the conductivity of the sample liquid is provided, and the conductivity meter outputs It is conceivable to correct the ion concentration using the measured conductivity.

However, in this conventional method, the conductivity is first measured by a conductivity meter, and the ion concentration is corrected using this conductivity. There is a problem that it is difficult to miniaturize the ion concentration measuring device because it requires complicated calculation means.

JP-A-4-27856

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ion concentration measuring device capable of accurately measuring an ion concentration with a simpler configuration.

That is, the ion concentration measuring device according to the present invention comprises a working electrode arranged in contact with a sample solution and outputting a measurement potential corresponding to the ion concentration in the sample solution, and a reference electrode arranged in contact with the sample solution. A reference electrode that outputs a potential, a resistance value measuring unit that measures the resistance value of the sample liquid, and a calculator that calculates the ion concentration based on the potential difference between the measured potential and the reference potential and the resistance value. It is characterized by comprising a part.

According to the ion concentration measuring device configured as described above, since the ion concentration is calculated using the resistance value, there is no need to calculate the conductivity. Further, the resistance value measuring unit does not need to be a conductivity meter as long as it can measure the resistance value. Therefore, it is possible to make the ion concentration measuring device as simple as possible while achieving the desired measurement accuracy.

If the resistance value measuring unit uses the reference electrode as a resistance value measuring electrode, the resistance value can be measured using only the parts necessary for measuring the ion concentration.

As a specific embodiment of the present invention, the calculator corrects the potential difference using the resistance value.

The type of ions to be measured is not particularly limited, but since calcium ions or ammonium ions have a relatively large effect on ion concentration measurement due to the electrical conductivity of the sample solution, the working electrode measures calcium ions or ammonium ions. When it does, the effect of the present invention is exhibited remarkably.

When the electric conductivity of the sample liquid is in the range of 10 mS/cm or more and 25 mS/cm or less, the effects of the present invention are exhibited particularly remarkably.

If dirt adheres to the surface of the resistance value measuring electrode for measuring the resistance value of the sample liquid, the resistance value measured by the resistance value measuring unit may change. Therefore, it is preferable to further include a cleaning mechanism for cleaning the surface of the resistance measurement electrode.

According to the present invention, since the ion concentration is corrected using the resistance value measured by the resistance value measuring unit, it is possible to save the trouble of converting the resistance value into conductivity while accurately measuring the ion concentration. can. In addition, since the ion concentration measuring device has a resistance value measuring unit, there is no need to separately prepare a conductivity meter.

1 is an overall schematic diagram of an ion concentration measuring device according to an embodiment of the present invention; FIG. 4 is a schematic diagram showing the structure of the sensor section of the ion concentration measuring device according to the present embodiment. FIG. FIG. 2 is a flowchart showing a method of calculating ion concentration in the ion concentration measuring device according to the embodiment; FIG. 4 is a schematic diagram showing the structure of a sensor section of an ion concentration measuring device according to another embodiment of the present invention.

An ion concentration measuring device 100 according to an embodiment of the present invention will be described below with reference to the drawings.

The ion concentration measuring device 100 according to the present embodiment measures, for example, various ion concentrations in sample liquids such as industrial wastewater, effluent water from water treatment facilities, river water, marsh water, and groundwater. .

This ion concentration measuring device 100 comprises, for example, as shown in FIG. and a display unit 4 for displaying the ion concentration and the like calculated by the calculation unit 3 .

The working electrode 1 is placed in contact with the sample liquid to output a measured potential corresponding to the concentration of specific ions in the sample liquid. For example, as shown in FIG. 2, the working electrode 1 according to the present embodiment includes a cylindrical working electrode housing 11 made of resin, and an internal electrode for measurement (internal electrode) disposed inside the working electrode housing 11. ), an ion-responsive membrane 12 attached to the tip of the working electrode housing 11 so as to be in contact with the sample liquid, and an ion-responsive membrane 12 housed inside the working electrode housing 11 to connect the internal electrode for measurement and the ion It has an internal liquid for measurement electrically connected to the responsive membrane 12 . The ion-responsive membrane 12 responds to calcium ions, for example. The internal electrode for measurement is, for example, a silver/silver chloride electrode, and the internal liquid for measurement is, for example, an aqueous solution of potassium chloride.

The reference electrode 2 outputs a reference potential with respect to the measured potential output from the working electrode 1. For example, as shown in FIG. 21 and a comparative internal electrode (not shown), which penetrates the comparative electrode housing 21 in the thickness direction and is formed to open on the surface of the comparative electrode housing 21 in contact with the sample. A liquid junction portion 22 made of a through hole and a porous ceramic or the like attached inside the through hole; and an internal liquid for a reference electrode that electrically connects the The internal electrode for measurement is, for example, a silver/silver chloride electrode, and the internal liquid for measurement is, for example, an aqueous solution of potassium chloride.

The calculator 3 is arranged, for example, between the working electrode 1 and the reference electrode 2, and detects the potential difference between the working electrode 1 and the reference electrode 2, and the potential difference output from the electrometer 5. For example, an information processing circuit comprising a CPU, a memory, an A/D converter, a D/A converter, and the like, executes the CPU and peripherals according to a program stored in a predetermined area of the memory. It is configured so that the devices work together to exhibit their functions.

As shown in FIG. 1, the ion concentration measuring device 100 according to this embodiment further includes a resistance value measuring section 6 that measures the resistance value of the sample liquid.
The resistance value measurement unit 6 includes a resistance value measurement electrode 61 , a ground electrode 62 , and a resistance value output unit 63 .
The resistance value output unit 63 outputs the resistance value (for example, resistance count value) detected between the resistance value measurement electrode 61 immersed in the sample liquid and the ground electrode 62 to the calculation unit 3. is output.

In this embodiment, as shown in FIG. 2, the reference electrode 2 is used as the resistance value measuring electrode 61 .
The calculation unit 3 also refers to the resistance value measured by the resistance value measurement unit 6 when calculating the ion concentration based on the potential difference between the working electrode 1 and the reference electrode 2 as described above. Then, the ion concentration is calculated.

A specific method by which the calculator 3 calculates the ion concentration based on the potential difference and the resistance value is, for example, as shown in FIG.

The potential difference between the working electrode 1 and the reference electrode 2 output from the electrometer 5 and the resistance value output from the resistance value measuring unit 6 are received, and the potential difference is corrected with the resistance value. I have to.

More specifically, a correlation formula representing the correlation between the electrical conductivity of a certain sample liquid and the resistance count value measured by the resistance value measuring unit 6 for the same sample is obtained in advance. Since the correlation between the electrical conductivity and the resistance count value has a relatively small individual difference in each ion concentration measuring device 100, the correlation formula obtained in advance is stored when the ion concentration measuring device 100 is shipped. It is good as

Further, for example, using a standard sample solution with a known concentration of ions to be measured, the potential difference output from the electrometer 5 is measured when the electrical conductivity is changed while the ion concentration is kept constant. A correlation formula representing the correlation between the conductivity (conductivity) and the potential difference is obtained in advance.

Using the two correlation formulas obtained in advance by the procedure described above, a correlation formula between the resistance count and the potential difference is created and stored in the ion concentration measuring device.

After that, the potential difference and the resistance count value are measured for a sample liquid whose ion concentration and electrical conductivity are unknown, and the calculation unit 3 that receives them uses the correlation formula between the resistance count value and the potential difference to calculate the The potential difference is corrected with the resistance count value.
The calculator 3 calculates the ion concentration based on the corrected potential difference and the Nernst equation.

According to the ion concentration measuring device 100 and the ion concentration measuring method according to the present embodiment, the calculator 3 calculates the potential difference between the working electrode 1 and the reference electrode 2 by the resistance value measured by the resistance value measuring unit 6. Since the potential difference after correction is used to calculate the ion concentration, fluctuations in the ion concentration due to changes in the electrical conductivity of the sample liquid can be suppressed as much as possible.

Since the calculation unit 3 uses the resistance count value measured by the resistance value measurement unit 6 as it is to correct the potential difference, the device configuration for calculating electrical conductivity from the resistance count value can be omitted.

Since the reference electrode 2 that is always included in the ion concentration measuring device 100 is used as the resistance value measuring electrode 61, there is no need to increase the number of parts of the ion concentration measuring device 100. FIG.

<Other embodiments according to the present invention>
The present invention is not limited to the above embodiments.
If the surface of the resistance value measuring electrode becomes dirty, the measured resistance value may fluctuate. Therefore, it is preferable to further include a cleaning mechanism 7 for cleaning the surface of the resistance value measuring electrode.

As the cleaning mechanism 7, for example, as shown in FIG. 4, one provided with a light source 71 for irradiating the surface of the reference electrode with ultraviolet rays, or a self-cleaning device such as titanium dioxide formed on the surface of the reference electrode. It may be provided with an effective antifouling coating, or may be provided with a cleaning member for physically scraping off dirt from the surface of the reference electrode.

The resistance value measuring electrode is not limited to the reference electrode, and may be another electrode or component such as a temperature sensor provided in the ion concentration measuring device, which also serves as the electrode.
Also, instead of providing a separate ground electrode, another electrode or the like may also serve as the ground electrode.

A temperature sensor for measuring temperature may be further provided, and the ion concentration measurement result may be further corrected based on the temperature information output from this temperature sensor.

In the above embodiment, the case where the working electrode outputs a potential corresponding to the concentration of calcium ions has been described, but the working electrode may respond to ammonium ions, hydrogen ions or potassium ions. It may be a case where it responds to other types of ions such as ions and sodium ions.

In the above-described embodiment, the case of a composite electrode in which the housings of the working electrode and the reference electrode are integrated has been described. good.
In addition, various modifications and combinations of embodiments may be made without departing from the gist of the present invention.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

In this example, the ion concentration measuring device described in detail in the above embodiment was used to measure the calcium ion concentration, and it was confirmed that the ion concentration measuring method according to the present invention improved the accuracy of the ion concentration measurement. rice field. Specific experimental procedures are as follows.

As a sample liquid, an aqueous solution with a calcium ion concentration of 40 mg/L was used.
Potassium chloride was added to this aqueous solution to prepare a plurality of sample solutions having different electrical conductivities while keeping the calcium ion concentration constant.

For a plurality of sample solutions having different electrical conductivities as described above, the resistance count value measured between the reference electrode and the ground electrode, the output potential actually measured between the working electrode and the reference electrode, and the specific resistance A corrected potential difference corrected using the count value and a calcium ion concentration calculated based on the corrected potential difference were obtained.

From the results of the experiment described above, it was found that the output potential for each sample with different electrical conductivity gradually decreased as the electrical conductivity increased, even though the calcium ion concentration was constant. Also, from the same experimental results, it was found that the resistance count value also gradually decreased as the electrical conductivity of the sample increased. As a result of evaluating these results, it was found that there is a relatively high correlation between the amount of change in the resistance count value and the amount of change in the output potential. Therefore, the corrected potential difference corrected using this correlation is stable because the amount of change when the electrical conductivity of the sample is changed is clearly smaller than the amount of change in the output potential. Do you get it. It was also confirmed that the calcium ion concentration calculated based on the corrected potential difference and the Nernst equation stably showed a value around 40 mg/L. It has been confirmed that the error in the calcium ion concentration calculated using the corrected potential difference is within the allowable range.

Further, from the results of the experiment, it was found that the correlation between the resistance count value and the output potential is highly correlated, especially when the electric conductivity of the sample liquid is in the range of 10 mS/cm or more and 25 mS/cm or less. rice field. Therefore, it is presumed that the effect of the ion concentration measuring device and the ion concentration measuring method according to the present invention is more remarkably exhibited in the sample liquid having the electrical conductivity within the range described above.

DESCRIPTION OF SYMBOLS 100... Ion concentration measuring apparatus 1... Working electrode 2... Reference electrode 3... Calculation part 6... Resistance value measurement part 7... Cleaning mechanism

Claims (8)

a working electrode that outputs a measured potential corresponding to the concentration of ions contained in the sample liquid;
a reference electrode that outputs a reference potential with respect to the measured potential that is output from the working electrode;
a resistance value measuring unit that measures the resistance value of the sample liquid;
An ion concentration measuring device, comprising: a calculator for calculating an ion concentration based on the potential difference between the working electrode and the reference electrode and the resistance value. 2. The ion concentration measuring device according to claim 1, wherein said resistance value measuring unit uses said reference electrode as a resistance value measuring electrode. The ion concentration measuring device according to claim 1 or 2, wherein the calculator corrects the potential difference using the resistance value. The ion concentration measuring device according to any one of claims 1 to 3, wherein the working electrode is for detecting calcium ion concentration or ammonium ion concentration. The ion concentration measuring device according to any one of claims 1 to 4, wherein the sample liquid has an electrical conductivity ranging from 10 mS/cm to 25 mS/cm. 3. The ion concentration measuring device according to claim 2, further comprising a cleaning mechanism for cleaning the surface of said resistance value measuring electrode. A method for measuring the concentration of ions contained in a sample liquid,
An ion concentration measuring method, wherein the concentration of the ions is calculated using a potential difference between a working electrode and a reference electrode arranged so as to be in contact with the sample liquid and a resistance value of the sample liquid. A program for measuring the concentration of ions contained in a sample liquid,
Ion concentration measurement that causes a computer to function as a calculator that calculates the concentration of the ions using the potential difference between the working electrode and the reference electrode that are arranged so as to be in contact with the sample liquid and the resistance value of the sample liquid. program.

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