Dissolved hydrogen concentration measurement device, electrode for dissolved hydrogen concentration measurement device, and dissolved hydrogen concentration measurement method

Abstract

To provide a device for measuring dissolved hydrogen concentration, electrodes for measuring dissolved hydrogen concentration, and method for measuring dissolved hydrogen concentration, which enable measurement of dissolved hydrogen concentration and facilitate pretreatment of the electrodes during measurement.SOLUTION: A dissolved hydrogen concentration measurement device is provided, comprising a working electrode immersed in a solution under measurement, and a measurement circuit configured to acquire dissolved hydrogen concentration in the solution under measurement by applying a given voltage to the working electrode and measuring a response current. The working electrode is obtained by modifying a surface of conductive diamond with platinum.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a dissolved hydrogen concentration measuring device that measures the dissolved hydrogen concentration in a liquid to be measured such as hydrogen water using an electrochemical measurement method, an electrode for the dissolved hydrogen concentration measuring device, and a dissolved hydrogen concentration measuring method.

Background Art

[0002] In recent years, hydrogen water in which hydrogen molecules (hydrogen gas) are dissolved in water has attracted attention in various fields. For example, in the health industry field, the effect of hydrogen molecules in hydrogen water reducing and removing active oxygen in the body has been focused on, and hydrogen water is used as drinking water for maintaining health. In the electronics industry field, hydrogen water is used as water for cleaning electronic components, focusing on the cleaning effect. In the medical field, the efficacy of hydrogen water has been attracting attention for suppressing neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease, improving diabetes, suppressing oxidative stress, anti-fatigue, anti-cancer, suppressing arteriosclerosis, suppressing drug side effects, suppressing kidney function / kidney transplantation disorders, suppressing small intestine transplantation disorders, suppressing allergic diseases, etc.

[0003] In such fields as the health industry, the electronics industry, and particularly the medical field, it is necessary to accurately measure the dissolved hydrogen concentration of hydrogen water. Generally, since hydrogen molecules easily escape from water in hydrogen water and the dissolved hydrogen concentration tends to decrease over time, it is important to measure and grasp the dissolved hydrogen concentration in hydrogen water at the time of use.

[0004] As a device for measuring the dissolved hydrogen concentration, gas chromatography (GC) is mainly used. However, this GC has problems such as being expensive, having a complicated operation, and lacking in convenience. On the other hand, a dissolved hydrogen concentration measuring device using an electrochemical measurement method that measures the current flowing during the oxidation-reduction reaction of molecules or the potential at the electrode interface not only does not require a large-scale device, but is also inexpensive and can perform accurate measurements with a simple operation. Furthermore, since the electrochemical measurement method can be measured by simply immersing the electrode in the liquid to be measured, real-time continuous measurement is also possible.

[0005] As an electrode for measuring the dissolved hydrogen concentration by an electrochemical measurement method, metal electrodes such as platinum (Pt) have been conventionally used. However, in order to perform accurate measurement with a metal electrode, it has been necessary to perform pretreatment by polishing each time, so the measurement has been very complicated.

[0006] If a conductive diamond electrode as described in Patent Document 1 is used as the measurement electrode, measurement can be performed without such pretreatment by polishing.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, when actually performing electrochemical measurement (cyclic voltammogram (CV) measurement) of hydrogen water using a boron-doped diamond electrode (BDD electrode), which is a conductive diamond electrode described in Patent Document 1, as a working electrode, a peak value related to hydrogen could not be detected in the response current flowing between the working electrode and the counter electrode. As a result, in the CV measurement using the BDD electrode as the working electrode, the dissolved hydrogen concentration could not be measured.

[0009] The present invention solves the above-described problems of the prior art, and an object of the present invention is to provide a dissolved hydrogen concentration measuring device, an electrode for a dissolved hydrogen concentration measuring device, and a dissolved hydrogen concentration measuring method that can measure the dissolved hydrogen concentration and are easy to pretreat the electrode during measurement.

Means for Solving the Problems

[0010] According to the present invention, a dissolved hydrogen concentration measuring device includes a working electrode immersed in a liquid to be measured, and a measurement circuit that acquires the dissolved hydrogen concentration in the liquid to be measured by applying a predetermined potential to the working electrode and measuring a response current. The working electrode is an electrode in which platinum is modified on the surface of conductive diamond.

[0011] In a device that applies a predetermined potential to a working electrode to measure a response current and acquires the dissolved hydrogen concentration in a liquid to be measured, since the working electrode is an electrode in which platinum is modified on the surface of conductive diamond, it is possible to measure the dissolved hydrogen concentration with good reproducibility. Also, even when the electrode is not polished before measurement, it is possible to measure the dissolved hydrogen concentration with stable and good reproducibility.

[0012] It is preferable that the conductive diamond is a boron-doped diamond polycrystalline thin film, and the platinum is platinum electrodeposited on the surface of the diamond polycrystalline thin film.

[0013] It is also preferable to include a working electrode that conducts electron transfer, a reference electrode that serves as a potential reference for the working electrode, and a counter electrode that forms a current circuit with the working electrode, and the measurement circuit is configured to linearly sweep the potential difference between the working electrode and the reference electrode and measure the response current flowing between the working electrode and the counter electrode.

[0014] It is also preferable that the measurement circuit is configured to apply a potential difference assumed to be a potential difference at which a peak value appears in the response current flowing between the working electrode and the counter electrode or a potential difference within a predetermined range including this potential difference between the working electrode and the reference electrode and measure the response current.

[0015] More preferably, the measurement circuit is configured to acquire the dissolved hydrogen concentration in the liquid to be measured from the peak value of the measured response current.

[0016] Furthermore, it is also preferable that the measurement circuit includes peak value detection means for detecting the peak value of the measured response current, and dissolved hydrogen concentration extraction means for obtaining the dissolved hydrogen concentration using a preset relationship between the peak value detected by the peak value detection means and the dissolved hydrogen concentration.

[0017] It is also preferable that the measurement circuit is configured to correct the acquired dissolved hydrogen concentration in the liquid to be measured according to the electrical conductivity of the liquid to be measured.

[0018] In this case, it is more preferable that the measurement circuit is configured to correct the acquired dissolved hydrogen concentration by adding a hydrogen concentration difference to the acquired dissolved hydrogen concentration or multiplying by a hydrogen concentration ratio.

[0019] According to the present invention, there is provided an electrode for a dissolved hydrogen concentration measuring device, which is used as a working electrode of the above-described dissolved hydrogen concentration measuring device and has a surface of conductive diamond modified with platinum.

[0020] According to the present invention, further, the dissolved hydrogen concentration measuring method includes dipping a working electrode, which is an electrode having a surface of conductive diamond modified with platinum, into the liquid to be measured, applying a predetermined potential to the working electrode, and measuring a response current, thereby obtaining the dissolved hydrogen concentration in the liquid to be measured.

[0021] It is preferable to use, as the working electrode, an electrode in which platinum is electrodeposited on the surface of a boron-doped diamond polycrystalline thin film.

[0022] It is also preferable to obtain the dissolved hydrogen concentration in the liquid to be measured by linearly sweeping the potential difference between the working electrode for electron transfer and the reference electrode serving as the potential reference of the working electrode and measuring the response current flowing between the working electrode and the counter electrode.

[0023] It is also preferable to apply a potential difference assumed to be a potential difference at which a peak value appears in the response current flowing between the working electrode and the counter electrode or a potential difference within a predetermined range including this potential difference between the working electrode and the reference electrode and measure the response current.

[0024] In this case, it is more preferable to obtain the dissolved hydrogen concentration in the liquid to be measured from the peak value of the measured response current.

[0025] More specifically, it is also preferable to detect the peak value of the measured response current and obtain the dissolved hydrogen concentration using a preset relationship between the detected peak value and the dissolved hydrogen concentration.

[0026] It is also preferable to correct the obtained dissolved hydrogen concentration in the liquid to be measured according to the electrical conductivity of the liquid to be measured.

[0027] In this case, it is more preferable to correct the obtained dissolved hydrogen concentration by adding a hydrogen concentration difference or multiplying by a hydrogen concentration ratio to the obtained dissolved hydrogen concentration.

Advantages of the Invention

[0028] According to the present invention, since the working electrode is an electrode in which platinum is modified on the surface of conductive diamond, it is possible to measure the dissolved hydrogen concentration with good reproducibility. Also, even when the electrode is not polished before measurement, it is possible to measure the dissolved hydrogen concentration with stable and good reproducibility.

Brief Description of the Drawings

[0029]

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[0030] FIG. 1 schematically shows the overall device configuration in the first embodiment of the dissolved hydrogen concentration measuring device of the present invention, and FIG. 2 schematically shows an example of the configuration of the working electrode in the dissolved hydrogen concentration measuring device of FIG. 1. This embodiment is an example of a device for measuring the dissolved hydrogen concentration of a measurement liquid for which it is not necessary to consider electrical conductivity.

[0031] In FIG. 1, 10 is a cell in which a measurement liquid 11 for measuring the dissolved hydrogen concentration such as hydrogen water exists, 12 is a working electrode (WE) immersed in the measurement liquid 11, 13 is a reference electrode (RE) immersed in the measurement liquid 11 and serving as a reference when determining the potential of the working electrode 12, 14 is a counter electrode (CE) immersed in the measurement liquid 11 and forming a current circuit with the working electrode 12, and 15 respectively shows a measurement circuit electrically connected to these working electrode 12, reference electrode 13, and counter electrode 14.

[0032] The measurement circuit 15 includes a potentiostat (constant potential electrolysis device) 15a for performing CV measurement and an information processing device 15b connected to the potentiostat 15a and composed of a computer in this embodiment. The potentiostat 15a linearly sweeps the potential difference between the working electrode 12 and the reference electrode 13, and the information processing device 15b detects the peak value of the response current flowing between the working electrode 12 and the counter electrode 14 to obtain the dissolved hydrogen concentration in the measurement liquid 11.

[0033] The information processing device 15b acquires the dissolved hydrogen concentration in the measurement liquid 11 from the peak value of the detected response current. That is, in the information processing device 15b, a correspondence formula or correspondence data between the peak value of the response current and the dissolved hydrogen concentration is set and stored in advance, and when the peak value is detected, the dissolved hydrogen concentration can be obtained from this correspondence formula or correspondence data. Although it is just an example, the correspondence formula is H con =a×A peak +b. Here, H con is the dissolved hydrogen concentration, A peak is the peak value of the response current, and a and b are constants.

[0034] In this embodiment, a conductive diamond electrode modified with platinum (Pt) is used for the working electrode 12, Ag / AgCl is used for the reference electrode 13, and platinum (Pt) is used for the counter electrode 14.

[0035] As shown in FIG. 2, this working electrode 12 is formed by depositing a boron-doped diamond (BDD) film 12b, which is a conductive diamond film, on a silicon substrate 12a, and platinum (Pt) 12c is deposited on the surface of the BDD film 12b by electrodeposition for modification.

[0036] The formation of the BDD film 12b is performed, for example, by polishing the mirror side of a silicon wafer with a polishing pad with diamond powder, ultrasonically cleaning with methanol, drying, and then supplying hydrogen gas, a carbon source, and a boron source using a microwave plasma chemical vapor deposition method (microwave plasma CVD method). Although it is just an example, the plasma output was 5000 W and the film formation time was 6 hours.

[0037] The modification of platinum (Pt) was performed by chronoamperometry to reduce hexachloroplatinic acid (H2PtCl6) and electrodeposit platinum 12c on the surface of the BDD film 12b. Here, a BDD film was used for the working electrode, platinum (Pt) for the counter electrode, and Ag / AgCl for the reference electrode. As the solution, 1 mM H2PtCl6 was prepared using 0.5 M sulfuric acid (H2SO4). The applied voltage was -0.3 V and the applied time was 150 seconds.

[0038] Figure 3 shows SEM images of the formed BDD film and the Pt-BDD film with platinum (Pt) modified thereon. In the figure, (A) is the BDD film and (B) is the Pt-BDD film, and the magnification is 10,000 times. As shown in Figure (B), Pt that looks like white grains is modified on the BDD film.

[0039] Regarding the dissolved hydrogen concentration measuring device of this embodiment, various studies were conducted as described below.

[0040] First, the reproducibility of CV measurement and the measurability of dissolved hydrogen concentration were examined.

[0041] The working electrode 12 having the Pt-BDD film 12b shown in Figure 2 was fabricated, and CV measurement was performed using the device shown in Figure 1. The reference electrode 13 was Ag / AgCl, and the counter electrode 14 was Pt. As a pretreatment, chronoamperometry was performed using 0.1 M KCl (potassium chloride) with an applied voltage of 0.6 V and an applied time of 30 seconds. The working electrode 12 was not polished. As the liquid to be measured, hydrogen water prepared by filling a container containing 0.1 M KCl solution with hydrogen gas at high pressure was used. The hydrogen gas was obtained by a hydrogen filling machine DAYS (registered trademark) manufactured by Doctorsman Co., Ltd. In the CV measurement, the applied voltage was swept from -6 V to +0.2 V, and the sweep rate was 100 mV / s.

[0042] Regarding the reproducibility, CV measurement was performed three times (1st to 3rd) for examination. Figure 4 shows a voltammogram which is the result of CV measurement. The horizontal axis represents the potential (V) of the working electrode 12 with respect to the reference electrode 13, and the vertical axis represents the current density (μA / cm 2 ) between the working electrode 12 and the counter electrode 14. As can be seen from the figure, good reproducibility was obtained in the three CV measurements. As a result, according to the configuration of this embodiment (when using the working electrode 12 having the Pt-BDD film 12b), it can be seen that CV measurement of hydrogen water is possible.

[0043] Regarding the measurability of the dissolved hydrogen concentration, the dissolved hydrogen concentration dependence of CV measurement was examined. The dissolved hydrogen concentration was changed by the time (0 minutes, 30 minutes, 60 minutes, 90 minutes, 120 minutes) of leaving the container of the liquid to be measured filled with hydrogen gas with its lid open in the air. Fig. 5 shows the measurement results. The horizontal axis and the vertical axis are the same as those in Fig. 4. As can be seen from the figure, as the dissolved hydrogen concentration decreases with the passage of time, the peak current density of the response current also decreases. Therefore, according to the configuration of the present embodiment (when the working electrode 12 having the Pt-BDD film 12b is used), it can be seen that the dissolved hydrogen concentration can be measured.

[0044] Next, the correspondence between the peak current density of the response current by CV measurement and the dissolved hydrogen concentration by the measurement of gas chromatography (GC) was examined for the dissolved hydrogen concentration measuring device of the present embodiment.

[0045] Similar to the above case, after preparing the liquid to be measured filled with hydrogen gas, the lid of the container was opened, and CV measurement by the dissolved hydrogen concentration measuring device of the present embodiment and measurement of the dissolved hydrogen concentration by GC were performed every time of leaving it in the air for a time (5 minutes, 30 minutes, 60 minutes, 90 minutes, 120 minutes). Fig. 6 shows the results of CV measurement by the dissolved hydrogen concentration measuring device of the present embodiment. The horizontal axis and the vertical axis are the same as those in Fig. 4.

[0046] The equipment used for GC measurement was TRIlyzer mBA-3000 manufactured by Taiyo Co., Ltd. The detector was a semiconductor gas sensor, the column was a packed column, the carrier gas was synthetic air, and the injection volume was 1 mL (25 °C). The measurement results of the dissolved hydrogen concentration by this GC are shown in Table 1.

Table 1

[0047] Figure 7 is a characteristic diagram plotting the peak current density of the response current in the CV measurement by the dissolved hydrogen concentration measuring device of the present embodiment and the dissolved hydrogen concentration by the GC measurement for the liquid to be measured with the same standing time (same dissolved hydrogen concentration). The horizontal axis is the dissolved hydrogen concentration (ppm), and the vertical axis is the peak current density of the response current (μA / cm 2 ). From this figure, it can be seen that the calibration curve between the peak current density of the response current in the CV measurement and the dissolved hydrogen concentration in the GC measurement is linear, and it is possible to measure the dissolved hydrogen concentration by the CV measurement. The approximate formula of this calibration curve is the peak current density of the response current (μA / cm 2 ) = 130 × dissolved hydrogen concentration (ppm) - 136. When converted, the dissolved hydrogen concentration (ppm) = 0.0077 × peak current density of the response current (μA / cm 2 ) + 1.05. Furthermore, in this measurement, the peak current density of the electrode (μA / cm 2 ) can be converted to 1.5 × peak value (μA). When converted to the peak value (μA), the dissolved hydrogen concentration (ppm) = 0.01155 × peak value of the response current (μA) + 1.05. This corresponds to the case where a = 0.01155 and b = 1.05 in the above-mentioned correspondence formula H con = a × A peak . From this formula, if the peak value A peak of the response current is obtained, the dissolved hydrogen concentration H con can be obtained.

[0048] Next, it was examined that the pre-treatment of polishing for the CV measurement is not required for the working electrode 12 of the dissolved hydrogen concentration measuring device of the present embodiment.

[0049] Figure 8 shows the results of 4 times (1st to 4th) of CV measurements when a Pt electrode is used as the working electrode as in the prior art, and Figure 9 shows the results of 3 times (1st to 3rd) of CV measurements when a Pt-BDD electrode is used as in the present embodiment. The horizontal axis and the vertical axis are the same as in the case of Figure 4. In the case of the Pt electrode and the case of the Pt-BDD electrode, polishing as a pre-treatment is not performed.

[0050] When a Pt electrode is used as the working electrode, as shown in Fig. 8, the peak current density of the response current decreases with each additional measurement. In contrast, when a Pt-BDD electrode is used as the working electrode, as shown in Fig. 9, the peak current density of the response current does not change much even after multiple measurements, and it was confirmed that it is stable and reproducible. This means that while the Pt electrode requires pretreatment by polishing, the Pt-BDD electrode does not require pretreatment by polishing.

[0051] Next, the repeatability and durability of the working electrode 12 in the dissolved hydrogen concentration measuring device of the present embodiment were examined.

[0052] Fig. 10 shows the results of 28 (1 to 28) CV measurements when the same working electrode 12 is used in the dissolved hydrogen concentration measuring device of the present embodiment. The horizontal axis and the vertical axis are the same as in the case of Fig. 4. Fig. 11 is a graph plotting the peak current density of the response current and the number of measurements in 28 CV measurements. In the figure, the horizontal axis is the number of measurements, and the vertical axis is the current density (μA / cm 2 ) of the current between the working electrode 12 and the counter electrode 14. The liquid to be measured was prepared for each measurement.

[0053] As shown in Fig. 10, good reproducibility was obtained in 28 CV measurements. Also, as shown in Fig. 11, it can be seen that even when CV measurements are repeated with the same working electrode, the peak current density of the response current does not decrease as a whole, although there is some variation.

[0054] Fig. 12 shows SEM images of the Pt-BDD film before CV measurement and after 28 CV measurements. Fig. (A) in the figure is before CV measurement, Fig. (B) is after 28 CV measurements, and the magnification is 4000 times. As shown in Fig. (B), although the Pt modified on the Pt-BDD film has decreased slightly, it was confirmed that the electrode itself has no deterioration and has stability.

[0055] Next, the variation in the peak current density of the response current that occurred in the above durability test was examined.

[0056] First, for a plurality of hydrogen waters prepared under the same conditions, CV measurement and GC measurement were performed to measure the dissolved hydrogen concentration. FIG. 13 shows the results of five (1st to 5th) CV measurements by the dissolved hydrogen concentration measuring apparatus of the present embodiment. The horizontal axis and the vertical axis are the same as those in the case of FIG. 4.

[0057] The equipment used for GC measurement was TRIlyzer mBA-3000 manufactured by Taiyo Corporation. As the detector, a semiconductor gas sensor was used, the column was a packed column, the carrier gas was synthetic air, and the injection volume was 1 mL (25 °C). The results of measuring the dissolved hydrogen concentration by this GC are shown in Table 2.

Table 2

[0058] On the other hand, as the liquid to be measured, a sulfuric acid solution (1 mM H2SO4 in 0.1 M KCl) was used, and repeated CV measurements were performed. When sulfuric acid was subjected to CV measurement, it was possible to observe a hydrogen peak in the same manner as in the case of hydrogen water. Also, the concentration of sulfuric acid was maintained constant at 1 mM. FIG. 14 shows the results of 30 (1 to 30) CV measurements of this sulfuric acid solution. The horizontal axis and the vertical axis are the same as those in the case of FIG. 4. From the figure, it can be seen that the CV measurement results are all consistent in 30 consecutive measurements.

[0059] From FIG. 13 and Table 2, and FIG. 14, it was inferred that the variation in the peak current density of the response current was not based on the accuracy of the working electrode, but on the variation in the dissolved hydrogen of the prepared hydrogen water. As a result, the durability of the working electrode 12 made of Pt-BDD was proven.

[0060] In the above-described studies, KCl was added as an electrolyte to give hydrogen water conductivity. However, since most of the commercially available hydrogen water is produced by filling tap water with hydrogen, as a practical sample, CV measurement was examined for hydrogen water prepared based on tap water.

[0061] Figure 15 shows the CV measurement results for actual samples prepared based on tap water, representing the peak current density of the response current in CV measurements when 0.1 M KCl is added and when no KCl is added. In the figure, the horizontal axis represents the measurement cycle, and the vertical axis represents the peak current density of the response current (μA / cm 2 ). As can be seen from the figure, when KCl is not added and the electrolyte is low, the peak current density of the response current decreases, but reproducibility was obtained in 5 measurements. As a result, it was found that CV measurement is possible with actual samples prepared based on tap water without preparing the liquid to be measured, and the dissolved hydrogen concentration can be measured.

[0062] As described above, according to the dissolved hydrogen concentration measuring device of the present embodiment, the peak current density of the response current is detected by CV measurement using a working electrode that is a Pt-BDD electrode, and the dissolved hydrogen concentration in the liquid to be measured is obtained. Therefore, it is possible to measure the dissolved hydrogen concentration with good reproducibility by an electrochemical measurement method. In addition, since a Pt-BDD electrode is used, electrode polishing treatment is not required before measurement, and the dissolved hydrogen concentration can be measured stably and with high sensitivity. In addition, the Pt-BDD electrode has been confirmed to have good stability and durability when repeatedly measured.

[0063] The dissolved hydrogen concentration measuring device of the present embodiment is suitable for use when measuring the dissolved hydrogen concentration of a liquid to be measured that does not require consideration of electrical conductivity. That is, when measuring hydrogen water prepared with tap water in Japan, for example, if a calibration curve is obtained based on the hydrogen concentration and the peak value (or peak current density) of the response current with average tap water (for example, tap water with an electrical conductivity of about 10 mS / m) as a reference, consideration of electrical conductivity is not necessary. This is the case, for example, when tap water, mineral water, blood, infusion solution, dialysis water, etc. are used as the liquid to be measured.

[0064] Figure 16 schematically shows the overall device configuration in the second embodiment of the dissolved hydrogen concentration measuring device of the present invention. This embodiment is an example of a device for measuring the dissolved hydrogen concentration of a liquid to be measured that requires consideration of electrical conductivity.

[0065] In FIG. 16, 110 is a cell in which a measurement solution 111, in which the dissolved hydrogen concentration such as hydrogen water is to be measured, exists; 112 is a working electrode (WE) immersed in the measurement solution 111; 113 is a reference electrode (RE) immersed in the measurement solution 111 and serving as a reference when determining the potential of the working electrode 112; 114 is a counter electrode (CE) immersed in the measurement solution 111 and forming a current circuit with the working electrode 112; and 115 respectively indicates measurement circuits electrically connected to these working electrode 112, reference electrode 113, and counter electrode 114. Further, 116 is connected to the measurement circuit 115 and indicates a selection switch for selecting an assumed electrical conductivity value of the measurement solution 111. The selection switch 116 is a contact switching switch, a volume, or a digital switch that selects the electrical conductivity value in an analog or digital manner.

[0066] The measurement circuit 115 includes a potentiostat (constant potential electrolysis device) 115a for performing CV measurement and an information processing device 115b connected to the potentiostat 115a and composed of a computer in this embodiment. The selection switch 116 is connected to the information processing device 115b. The potentiostat 115a linearly sweeps the potential difference between the working electrode 112 and the reference electrode 113, and the information processing device 115b detects the peak value of the response current flowing between the working electrode 112 and the counter electrode 114, and obtains the dissolved hydrogen concentration in the measurement solution 111 from the detected peak value. In this case, the dissolved hydrogen concentration is corrected according to the electrical conductivity value specified by the selection switch 116.

[0067] The information processing device 115b obtains the dissolved hydrogen concentration in the liquid to be measured 111 from the detected peak value of the response current and the electrical conductivity specified by the selection switch 116. That is, a plurality of electrical conductivity values of the liquid to be measured obtained by measurement in advance are set in the information processing device 115b, and one electrical conductivity value is specified by the input from the selection switch 116. When calculating the dissolved hydrogen concentration from the peak value of the response current, the specified electrical conductivity value is used to correct the dissolved hydrogen concentration. That is, there is a linear correspondence between the electrical conductivity and the peak value of the response current, and the peak value of the response current is affected by the electrical conductivity of the liquid to be measured. Therefore, in the present embodiment, in order to eliminate this influence, the dissolved hydrogen concentration calculated from the peak value of the response current is corrected according to the electrical conductivity.

[0068] In the information processing device 115b, a correspondence formula or correspondence data between the peak value of the response current and the dissolved hydrogen concentration is set and stored in advance. When the peak value is detected, the dissolved hydrogen concentration can be obtained from this correspondence formula or correspondence data. The obtained dissolved hydrogen concentration is corrected based on the electrical conductivity, and the final dissolved hydrogen concentration is obtained. Although it is merely an example, the correspondence formula between the peak value of the response current and the dissolved hydrogen concentration is H con =a×A peak +b. When correcting with the electrical conductivity, H con =a×A peak +b+c, or H con =(a×A peak +b)×d. Here, H con is the dissolved hydrogen concentration, A peak is the peak value of the response current, a and b are constants, c is the hydrogen concentration difference when performing correction by addition, and d is the hydrogen concentration ratio when performing correction by multiplication.

[0069] In the present embodiment, a conductive diamond electrode modified with platinum (Pt) is used for the working electrode 112, Ag / AgCl is used for the reference electrode 113, and platinum (Pt) is used for the counter electrode 114.

[0070] Since the configuration and manufacturing method of the working electrode 112 are the same as those of the working electrode 12 shown in FIG. 2 in the first embodiment, detailed description thereof will be omitted.

[0071] In this embodiment, in order to examine how the peak value of the response current in the CV measurement should be corrected according to the electrical conductivity of the liquid to be measured, first, samples that are aqueous KCl solutions with various KCl concentrations are prepared, and a sample that is an aqueous solution obtained by preparing tap water with KCl (hereinafter, an aqueous solution derived from tap water) is prepared, and the electrical conductivities of these samples are measured.

[0072] The electrical conductivity of the samples was measured using a compact conductivity meter LAQUAtwin manufactured by Horiba, Ltd. This conductivity meter immerses a conductivity cell having a pair of current-carrying electrodes in the liquid to be measured, passes a current through this, measures the resistance, and obtains the electrical conductivity.

[0073] Table 3 shows the electrical conductivities measured for samples with various KCl concentrations using aqueous KCl solutions, and Table 4 shows the electrical conductivities measured for samples with various KCl concentrations using aqueous solutions derived from tap water. In Table 4, the data with a KCl concentration of 0 is the case where no KCl is added and only tap water is used.

Table 3

Table 4

[0074] For each of these samples with various KCl concentrations, cyclic voltammetry (CV) measurements were repeatedly performed using the dissolved hydrogen concentration measuring apparatus of the present embodiment. FIG. 17 shows the measurement results of a sample with a KCl concentration of 1 mM in an aqueous KCl solution for 4 times (1st to 4th), FIG. 18 shows the measurement results of a sample with a KCl concentration of 2.5 mM in an aqueous KCl solution for 3 times (1st to 3rd), FIG. 19 shows the measurement results of a sample with a KCl concentration of 5 mM in an aqueous KCl solution for 5 times (1st to 5th), FIG. 20 shows the measurement results of a sample with a KCl concentration of 7.5 mM in an aqueous KCl solution for 9 times (1st to 9th), and FIG. 21 shows the measurement results of a sample with a KCl concentration of 10 mM in an aqueous KCl solution for 9 times (1st to 9th). Also, FIG. 22 shows the measurement results of a sample with a KCl concentration of 1 mM in an aqueous solution derived from tap water for 10 times (1st to 10th), FIG. 23 shows the measurement results of a sample with a KCl concentration of 2.5 mM in an aqueous solution derived from tap water for 12 times (1st to 12th), FIG. 24 shows the measurement results of a sample with a KCl concentration of 5 mM in an aqueous solution derived from tap water for 16 times (1st to 16th), FIG. 25 shows the measurement results of a sample with a KCl concentration of 7.5 mM in an aqueous solution derived from tap water for 14 times (1st to 14th), and FIG. 26 shows the measurement results of a sample with a KCl concentration of 10 mM in an aqueous solution derived from tap water for 11 times (1st to 11th). In these figures, the horizontal axis represents the potential (V) of the working electrode 12 with respect to the reference electrode 13, and the vertical axis represents the current (μA) between the working electrode 12 and the counter electrode 14.

[0075] FIG. 27 is a characteristic diagram plotting the average value of the peak value of the response current obtained by performing CV measurement on samples with each KCl concentration in an aqueous KCl solution and samples with each KCl concentration in an aqueous solution derived from tap water, and the measured value of its electrical conductivity. The horizontal axis is the electrical conductivity (mS / m), the vertical axis is the peak value of the response current (peak current value) (μA), A is a sample in an aqueous KCl solution, and B is a sample in an aqueous solution derived from tap water. From this figure, the calibration curve between the peak value of the response current and the electrical conductivity of the CV measurement lies on a straight line. The approximate formula for this calibration curve is, for an aqueous KCl solution, the peak value of the response current (μA) = 0.2759 × electrical conductivity (mS / m) + 31.851. When converting the peak value of the response current to current density, the peak current density of the response current (μA / cm 2) = 0.414 × Electrical conductivity (mS / m) + 47.777. For the aqueous solution derived from tap water, the peak value of the response current (μA) = 0.2499 × Electrical conductivity (mS / m) + 34.932. When converting the peak value of the response current to current density, the peak current density of the response current (μA / cm 2 ) = 0.375 × Electrical conductivity (mS / m) + 52.398.

[0076] Figure 28 shows the relationship between the KCl concentration and the electrical conductivity of the KCl aqueous solution and the aqueous solution derived from tap water based on Tables 3 and 4. The horizontal axis is KCl (mM), and the vertical axis is the electrical conductivity (mS / m). Generally, for the electrical conductivity of the KCl aqueous solution, "approx. 0" indicates the linearity at zero concentration, and the characteristics shown in Figure 28 also show that the electrical conductivity of the KCl aqueous solution is "approx. 0". Also, in the aqueous solution derived from tap water, when the KCl concentration is about 1 mM, the electrical conductivity is affected by the tap water, but when the KCl concentration is 2.5 mM or more (the electrical conductivity is 50 mS / m or more), the electrical conductivity is almost based on the value of KCl.

[0077] Next, actually consider how the peak value of the response current in the CV measurement should be corrected according to the electrical conductivity of the liquid to be measured.

[0078] Examination with an Aqueous KCl Solution For the KCl aqueous solution, from Figure 27, the corresponding formula A where the peak value of the response current (μA) = 0.2759 × Electrical conductivity (mS / m) + 31.851 is obtained. From the relationship of current density (μA / cm 2 ) = 1.5 × current (μA), after conversion, the peak current density of the response current (μA / cm 2 ) = 0.414 × Electrical conductivity (mS / m) + 47.777 is obtained. Originally, the maximum dissolved hydrogen amount that can be dissolved does not become the same depending on the KCl concentration, but it is assumed by calculating with the maximum dissolved concentration of tap water in the atmosphere as 1.6 ppm.

[0079] Also, from the relationship between the peak value of the response current and the dissolved hydrogen concentration described in the first embodiment, the dissolved hydrogen concentration (ppm) = 0.0077 × the peak current density of the response current (μA / cm 2) A corresponding formula of +1.05 is obtained. FIG. 29 shows the relationship between the peak value of the response current corresponding to this corresponding formula and the dissolved hydrogen concentration. The horizontal axis is the peak value of the response current (μA), and the vertical axis is the dissolved hydrogen concentration (ppm).

[0080] As described above, in the case of only tap water, the electrical conductivity is 16.7 mS / m, the maximum dissolved hydrogen concentration in tap water in the atmosphere is 1.6 ppm, and the peak value of the response current is the peak value of the response current (μA) = (1.6 - 1.05) / (0.0077×1.5) = 47.62 μA. The measured value is the peak value of the response current (μA) = 0.2759×electrical conductivity (mS / m) + 31.851 = 0.2759×16.7 + 31.851 = 36.46 μA.

[0081] There is a difference of about 11 μA between the calculated value and the measured value. When this 11 μA is converted to the dissolved hydrogen concentration, the dissolved hydrogen concentration difference (ppm) = 0.0077×1.5×peak current value (μA) = 0.0077×1.5×11 = 0.13 ppm. Whether this difference is within the allowable range seems to depend on the application, and depending on the application of the aqueous solution to be measured, electrical conductivity correction may be required.

[0082] The electrical conductivity of tap water in Japan is approximately 5 - 20 (mS / m). When the peak value of the response current, the current density of the peak value (peak current density), and the dissolved hydrogen concentration are obtained, it is as shown in Table 5.

Table 5

[0083] Also, from the relationship between the KCl concentration and the electrical conductivity shown in Fig. 28, when measuring the electrical conductivity in a wide range of 0 to 150 mS / m, it is a desirable situation to perform correction. Here, the saturated hydrogen concentration at an electrical conductivity of 16.4 mS / m is 1.6 ppm, and the current density of the peak value of the response current is 150 μA / cm 2 (current value 100 μA), from the relationship between the peak current density value and the dissolved hydrogen concentration, the saturated concentration is dissolved hydrogen concentration (ppm) = 0.0077 × current density (μA / cm 2 ) + 1.05 = 0.0077 × 150 + 1.05 = 2.20 (ppm). The electrical conductivity corresponding to the peak value of 100 μA is obtained by converting the peak value of the response current (μA) = 0.2759 × electrical conductivity (mS / m) + 31.851, and the electrical conductivity (mS / m) = (peak value (μA) - 31.851) / 0.2759 = (100 - 31.851) / 0.2759 = 247 (mS / m). Fig. 30 shows the characteristics of the saturated hydrogen concentration with respect to the electrical conductivity, with the saturated hydrogen concentration being 1.6 ppm when the electrical conductivity is 16.4 mS / m and 2.2 ppm when the electrical conductivity is 247 mS / m. In the figure, the horizontal axis is the electrical conductivity (mS / m) and the vertical axis is the saturated hydrogen concentration (ppm).

[0084] From this figure, it can be seen that the calculated saturated hydrogen concentration (ppm) = 0.0026 × electrical conductivity (mS / m) + 1.5573 holds. Summarizing this result and the measurement result, it is as shown in Table 6. In Table 6, the calculated saturated hydrogen concentration is calculated by the calculated saturated hydrogen concentration (ppm) = 0.0026 × electrical conductivity (mS / m) + 1.5573, the peak value of the response current is calculated by the peak value of the response current (μA) = 0.2759 × electrical conductivity (mS / m) + 31.851, and the dissolved hydrogen concentration is calculated by the dissolved hydrogen concentration (ppm) = 0.0077 × 1.5 × current peak value (μA) + 1.05. Also, the difference between the calculated saturated hydrogen concentration (ppm) and the measured calculated saturated hydrogen concentration (ppm) is the hydrogen concentration difference (ppm), and the hydrogen concentration difference (ppm) = -0.0006 × electrical conductivity (mS / m) + 0.1394 is given.

Table 6

[0085] Figure 31 shows the relationship between the electrical conductivity (mS / m) and the hydrogen concentration difference (ppm) in Table 6. In the figure, the horizontal axis represents the electrical conductivity (mS / m), and the vertical axis represents the hydrogen concentration difference (ppm). By adding and correcting the hydrogen concentration difference shown in the figure to the dissolved hydrogen concentration calculated from the peak value of the response current, correction based on the electrical conductivity can be performed.

[0086] That is, the corrected calculated hydrogen concentration can be obtained by: Corrected calculated hydrogen concentration (ppm) = 0.0077 × 1.5 × Peak value of current (μA) + 1.05 - (0.0006 × Electrical conductivity (mS / m)) + 0.1394 = 0.0077 × 1.5 × Peak value of current (μA) - 0.0006 × Electrical conductivity (mS / m) + 1.1894.

[0087] When the corrected calculated hydrogen concentration is obtained using this formula, it is as shown in Table 7.

Table 7

[0088] From Table 7, according to the above correction method, an error of about 1% occurs, but the dissolved hydrogen concentration is almost the same value.

[0089] Incidentally, when the corrected calculated hydrogen concentration is obtained by multiplication correction instead of the addition correction as described above, it is as shown in Table 8. In Table 8, the calculated saturated hydrogen concentration is calculated by: Calculated saturated hydrogen concentration (ppm) = 0.0026 × Electrical conductivity (mS / m) + 1.5573, the peak value of the response current is calculated by: Peak value of response current (μA) = 0.2759 × Electrical conductivity (mS / m) + 31.851, and the dissolved hydrogen concentration is calculated by: Dissolved hydrogen concentration (ppm) = 0.0077 × 1.5 × Peak value of current (μA) + 1.05. Also, the ratio of the calculated saturated hydrogen concentration (ppm) to the measured calculated saturated hydrogen concentration (ppm) is the hydrogen concentration ratio, and the hydrogen concentration ratio = Calculated saturated hydrogen concentration (ppm) / Measured calculated saturated hydrogen concentration (ppm).

Table 8

[0090] Figure 32 shows the relationship between the electrical conductivity (mS / m) and the hydrogen concentration ratio (saturated / measured) in Table 8. In this figure, the horizontal axis represents the electrical conductivity (mS / m), and the vertical axis represents the hydrogen concentration ratio (saturated / measured). The hydrogen concentration ratio (saturated / measured) is a correction factor. If the dissolved hydrogen concentration calculated from the peak value of the response current is multiplied by the hydrogen concentration ratio (saturated / measured) shown in this figure, that is, the correction factor, correction based on the electrical conductivity can be performed.

[0091] From Figure 32, since the relationship of correction factor = -0.0005 × electrical conductivity (mS / m) + 1.0946 holds, the corrected calculated hydrogen concentration can be obtained by corrected calculated hydrogen concentration (ppm) = (0.0077 × 1.5 × current peak value (μA) + 1.05) × (-0.0005 × electrical conductivity (mS / m) + 1.0946).

[0092] When the corrected calculated hydrogen concentration is obtained using this formula, it becomes as shown in Table 9.

Table 9

[0093] From Table 9, according to this correction method, an error of about 1% occurs, but the dissolved hydrogen concentration becomes almost the same value.

[0094] Examination with an Aqueous Solution Derived from Tap Water For the aqueous solution derived from tap water, the corresponding formula B of peak value of response current (μA) = 0.2499 × electrical conductivity (mS / m) + 34.932 is obtained from Figure 27. When converted from the relationship of current density (μA / cm 2 ) = 1.5 × current (μA), the peak current density of the response current (μA / cm 2 ) = 0.3749 × electrical conductivity (mS / m) + 52.398 is obtained. Originally, the maximum dissolved hydrogen amount dissolved by the KCl concentration is not the same, but it is assumed that the maximum dissolved concentration in the atmosphere of tap water is 1.6 ppm for calculation.

[0095] Also, from the relationship between the peak value of the response current and the dissolved hydrogen concentration described in the first embodiment, the following correspondence formula shown in FIG. 29 is obtained: dissolved hydrogen concentration (ppm) = 0.0077 × peak current density of the response current (μA / cm 2 ) + 1.05.

[0096] As described above, in the case of only tap water, the electrical conductivity is 16.7 mS / m, the maximum dissolved hydrogen concentration in tap water in the atmosphere is 1.6 ppm, and the peak value of the response current is: peak value of the response current (μA) = (1.6 - 1.05) / (0.0077 × 1.5) = 47.62 μA. The measured value is: peak value of the response current (μA) = 0.2499 × electrical conductivity (mS / m) + 34.932 = 0.2759 × 16.7 + 34.932 = 39.12 μA.

[0097] There is a difference of about 8.5 μA between the calculated value and the measured value. When this 8.5 μA is converted to the dissolved hydrogen concentration, the dissolved hydrogen concentration difference (ppm) = 0.0077 × 1.5 × peak current value (μA) = 0.0077 × 1.5 × 8.5 = 0.098 ppm. Whether this difference is within the allowable range is considered to depend on the application, and depending on the application of the aqueous solution to be measured, electrical conductivity correction may be required.

[0098] As described in relation to Table 5, when producing hydrogen water with Japanese tap water, if a calibration curve is obtained based on the hydrogen concentration and the peak value (or peak current density) of the response current with respect to standard water having an electrical conductivity of about 10 mS / m, then when producing hydrogen water with Japanese tap water, the influence of electrical conductivity on the measurement results can be ignored. In addition to tap water, when mineral water, blood, infusion solution, dialysis water, etc. are used as the liquid to be measured, the electrical conductivity can also be ignored.

[0099] Also, from the relationship between the KCl concentration and the electrical conductivity shown in FIG. 28, when measuring in a wide range of electrical conductivity from 0 to 150 mS / m, it is a desirable situation to perform correction. Here, the saturated hydrogen concentration at an electrical conductivity of 16.4 mS / m is 1.6 ppm, and the current density of the peak value of the response current is 150 μA / cm 2(At a current value of 100 μA), the saturation concentration can be obtained from the relationship between the peak current density value and the dissolved hydrogen concentration. The dissolved hydrogen concentration (ppm) = 0.0077 × current density (μA / cm 2 ) + 1.05 = 0.0077 × 150 + 1.05 = 2.20 (ppm). The electrical conductivity corresponding to this peak value of 100 μA is obtained by converting the peak value of the response current (μA) = 0.2499 × electrical conductivity (mS / m) + 34.932. So, the electrical conductivity (mS / m) = (peak value (μA) - 34.932) / 0.2499 = (100 - 34.932) / 0.2499 = 260 (mS / m). Figure 33 shows the characteristics of the saturation hydrogen concentration with respect to the electrical conductivity, assuming a saturation hydrogen concentration of 1.6 ppm when the electrical conductivity is 16.4 mS / m and a saturation hydrogen concentration of 2.2 ppm when the electrical conductivity is 260 mS / m. In this figure, the horizontal axis represents the electrical conductivity (mS / m), and the vertical axis represents the saturation hydrogen concentration (ppm).

[0100] From this figure, it can be seen that the calculated saturation hydrogen concentration (ppm) = 0.0025 × electrical conductivity (mS / m) + 1.5596 holds. Summarizing this result and the measurement results, it is as shown in Table 10. In Table 10, the calculated saturation hydrogen concentration is calculated by the formula: calculated saturation hydrogen concentration (ppm) = 0.0025 × electrical conductivity (mS / m) + 1.5596. The peak value of the response current is calculated by the formula: peak value of the response current (μA) = 0.2499 × electrical conductivity (mS / m) + 34.932. The dissolved hydrogen concentration is calculated by the formula: dissolved hydrogen concentration (ppm) = 0.0077 × 1.5 × peak current value (μA) + 1.05. Also, the difference between the calculated saturation hydrogen concentration (ppm) and the measured calculated saturation hydrogen concentration (ppm) is the hydrogen concentration difference (ppm), which is given by hydrogen concentration difference (ppm) = -0.0004 × electrical conductivity (mS / m) + 0.1061.

Table 10

[0101] Figure 34 shows the relationship between the electrical conductivity (mS / m) and the hydrogen concentration difference (ppm) in Table 10. In this figure, the horizontal axis represents the electrical conductivity (mS / m), and the vertical axis represents the hydrogen concentration difference (ppm). By adding and correcting the hydrogen concentration difference shown in this figure to the dissolved hydrogen concentration calculated from the peak value of the response current, correction based on the electrical conductivity can be performed.

[0102] That is, the corrected calculated hydrogen concentration can be obtained by the formula: corrected calculated hydrogen concentration (ppm) = 0.0077×1.5×peak value of current (μA) + 1.05 - (0.0004×electrical conductivity (mS / m)) + 0.1061 = 0.0077×1.5×peak value of current (μA) - 0.0004×electrical conductivity (mS / m) + 1.156.

[0103] When the corrected calculated hydrogen concentration is obtained using this formula, it becomes as shown in Table 11.

Table 11

[0104] From Table 11, according to the above correction method, the dissolved hydrogen concentration becomes almost the same value.

[0105] Incidentally, when the corrected calculated hydrogen concentration is obtained by multiplication correction instead of the addition correction as described above, it becomes as shown in Table 12. In Table 12, the calculated saturated hydrogen concentration is calculated by the formula: calculated saturated hydrogen concentration (ppm) = 0.0025×electrical conductivity (mS / m) + 1.5596, the peak value of the response current is calculated by the formula: peak value of response current (μA) = 0.2499×electrical conductivity (mS / m) + 34.932, and the dissolved hydrogen concentration is calculated by the formula: dissolved hydrogen concentration (ppm) = 0.0077×1.5×peak value of current (μA) + 1.05. Also, the ratio of the calculated saturated hydrogen concentration (ppm) to the measured calculated saturated hydrogen concentration (ppm) is the hydrogen concentration ratio, and the hydrogen concentration ratio = calculated saturated hydrogen concentration (ppm) / measured calculated saturated hydrogen concentration (ppm).

Table 12

[0106] Figure 35 shows the relationship between the electrical conductivity (mS / m) and the hydrogen concentration ratio (saturated / measured) in Table 12. In this figure, the horizontal axis represents the electrical conductivity (mS / m), and the vertical axis represents the hydrogen concentration ratio (saturated / measured). The hydrogen concentration ratio (saturated / measured) is a correction factor. If the dissolved hydrogen concentration calculated from the peak value of the response current is multiplied by the hydrogen concentration ratio (saturated / measured) shown in this figure, that is, the correction factor, correction based on the electrical conductivity can be performed.

[0107] From Figure 35, since the relationship of correction factor = -0.0003 × electrical conductivity (mS / m) + 1.0708 holds, the corrected calculated hydrogen concentration can be obtained by corrected calculated hydrogen concentration (ppm) = (0.0077 × 1.5 × current peak value (μA) + 1.05) × (-0.0003 × electrical conductivity (mS / m) + 1.0708).

[0108] When the corrected calculated hydrogen concentration is obtained using this formula, it becomes as shown in Table 13.

Table 13

[0109] From Table 13, according to this correction method, an error of about 2% occurs, but the dissolved hydrogen concentration becomes almost the same value.

[0110] Note that regarding the results of examination on the reproducibility of CV measurement and the measurability of dissolved hydrogen concentration in this embodiment, the results of examination on the correspondence relationship between the peak value of the response current by CV measurement and the dissolved hydrogen concentration by GC measurement, the results of examination on the unnecessary pre-treatment of polishing for CV measurement regarding the working electrode, the results of examination on the repetitive reproducibility and durability of the working electrode, the results of examination on the variation of the peak value of the response current generated in the durability test, and as a practical sample, the results of examination on CV measurement for hydrogen water prepared based on tap water were the same as those in the case of the first embodiment.

[0111] As described above, according to the dissolved hydrogen concentration measuring device of the present embodiment, the peak value of the response current is detected by CV measurement using the working electrode which is a Pt-BDD electrode, and the dissolved hydrogen concentration in the liquid to be measured is acquired. Therefore, it is possible to measure the dissolved hydrogen concentration with good reproducibility by an electrochemical measurement method. Further, since a Pt-BDD electrode is used, polishing treatment of the electrode is not required before measurement, and the dissolved hydrogen concentration can be stably measured with high sensitivity. Further, the Pt-BDD electrode has been confirmed to have good stability and durability when repeatedly measured. Furthermore, since the peak value of the detected response current is corrected according to the electrical conductivity of the liquid to be measured, the dissolved hydrogen concentration can be correctly and accurately measured even for a liquid to be measured that requires consideration of the electrical conductivity.

[0112] In the second embodiment described above, the peak value of the response current is corrected according to the electrical conductivity value input from the selection switch 116, but a sensor for measuring the electrical conductivity of the liquid to be measured 111 may be provided, and the peak value of the response current may be corrected according to the electrical conductivity value measured by this sensor.

[0113] The dissolved hydrogen concentration measuring device of the present embodiment is suitable for use when measuring the dissolved hydrogen concentration of a liquid to be measured that requires consideration of the electrical conductivity. That is, when the liquid to be measured has a large electrical conductivity range exceeding 100 mS / m, in some cases, it is necessary to consider the electrical conductivity. This is, for example, the case when measuring liquids to be measured such as pure water, drinking water, carbonated water, soy sauce, dressing, and juice with the same measuring instrument.

[0114] In the embodiment described above, the potential difference between the working electrode and the reference electrode is linearly swept by the CV measurement circuit to detect the peak value of the response current flowing between the working electrode and the counter electrode. However, when the potential difference at which the peak value appears can be predicted, the peak response current may be measured by applying the potential difference or a potential difference within a predetermined range including the potential difference between the working electrode and the reference electrode, and the dissolved hydrogen concentration may be calculated. Thereby, the circuit configuration becomes simple, and a small and inexpensive dissolved hydrogen concentration measuring device can be provided.

[0115] The above-described embodiments all illustratively show the present invention and do not show it in a restrictive manner. The present invention can be implemented in various other modified forms and changed forms. Therefore, the scope of the present invention is defined only by the scope of the claims and its equivalent scope.

Explanation of Reference Numerals

[0116] 10, 110 cells 11, 111 liquid to be measured 12, 112 working electrode (WE) 12a, 112a silicon substrate 12b, 112b BDD film 12c, 112c Pt 13, 113 reference electrode (RE) 14, 114 counter electrode (CE) 15, 115 measurement circuit 15a, 115a potentiostat 15b, 115b information processing device 116 selection switch

Claims

1. An apparatus for measuring the dissolved hydrogen concentration in a liquid to be measured, comprising: a working electrode immersed in the liquid to be measured; and a measuring circuit configured to measure a response current by applying a predetermined potential to the working electrode and thereby obtain the dissolved hydrogen concentration in the liquid to be measured, wherein the working electrode is an electrode obtained by modifying conductive diamond with platinum.

2. The apparatus for measuring the dissolved hydrogen concentration according to claim 1, wherein the conductive diamond is a boron-doped diamond polycrystalline thin film, and the platinum is platinum electrodeposited on the surface of the diamond polycrystalline thin film.

3. The apparatus for measuring the dissolved hydrogen concentration according to claim 1 or 2, further comprising: the working electrode for electron transfer; a reference electrode serving as a potential reference for the working electrode; and a counter electrode forming a current circuit with the working electrode, wherein the measuring circuit is configured to linearly sweep the potential difference between the working electrode and the reference electrode and measure the response current flowing between the working electrode and the counter electrode.

4. The apparatus for measuring the dissolved hydrogen concentration according to claim 1 or 2, wherein the measuring circuit is configured to apply, between the working electrode and the reference electrode, a potential difference assumed to be a potential difference at which a peak value appears in the response current flowing between the working electrode and the counter electrode or a potential difference within a predetermined range including the potential difference, and measure the response current.

5. The apparatus for measuring the dissolved hydrogen concentration according to claim 3 or 4, wherein the measuring circuit is configured to obtain the dissolved hydrogen concentration in the liquid to be measured from the peak value of the measured response current.

6. The apparatus for measuring the dissolved hydrogen concentration according to claim 5, wherein the measuring circuit includes a peak value detecting means for detecting the peak value of the measured response current, and a dissolved hydrogen concentration extracting means for obtaining the dissolved hydrogen concentration by using a preset relationship between the peak value detected by the peak value detecting means and the dissolved hydrogen concentration.

7. The apparatus for measuring the dissolved hydrogen concentration according to any one of claims 3 to 6, wherein the measuring circuit is configured to correct the obtained dissolved hydrogen concentration in the liquid to be measured according to the electrical conductivity of the liquid to be measured.

8. The apparatus for measuring the dissolved hydrogen concentration according to claim 7, wherein the measuring circuit is configured to correct the obtained dissolved hydrogen concentration by adding a hydrogen concentration difference or multiplying by a hydrogen concentration ratio to the obtained dissolved hydrogen concentration.

9. An electrode for a dissolved hydrogen concentration measuring device, which is used as a working electrode of the dissolved hydrogen concentration measuring device according to any one of claims 1 to 8, and is characterized in that platinum is modified on the surface of conductive diamond.

10. A method for measuring the dissolved hydrogen concentration in a liquid to be measured, comprising immersing a working electrode, which is an electrode with platinum modified on the surface of conductive diamond, in the liquid to be measured, applying a predetermined potential to the working electrode, and measuring a response current, thereby obtaining the dissolved hydrogen concentration in the liquid to be measured.

11. The method for measuring the dissolved hydrogen concentration according to claim 10, wherein an electrode obtained by electrodepositing platinum on the surface of a boron-doped diamond polycrystalline thin film is used as the working electrode.

12. The method for measuring the dissolved hydrogen concentration according to claim 9 or 10, wherein a potential difference between the working electrode for electron transfer and a reference electrode serving as a potential reference of the working electrode is linearly swept, and a response current flowing between the working electrode and a counter electrode is measured, thereby obtaining the dissolved hydrogen concentration in the liquid to be measured.

13. The method for measuring the dissolved hydrogen concentration according to claim 9 or 10, wherein a potential difference assumed to be a potential difference at which a peak value appears in the response current flowing between the working electrode and the counter electrode or a potential difference within a predetermined range including the potential difference is applied between the working electrode and the reference electrode, and the response current is measured.

14. The method for measuring the dissolved hydrogen concentration according to claim 12 or 13, wherein the dissolved hydrogen concentration in the liquid to be measured is obtained from the peak value of the measured response current.

15. The method for measuring the dissolved hydrogen concentration according to claim 14, wherein the peak value of the measured response current is detected, and the dissolved hydrogen concentration is obtained by using a preset relationship between the detected peak value and the dissolved hydrogen concentration.

16. The method for measuring the dissolved hydrogen concentration according to any one of claims 12 to 15, wherein the obtained dissolved hydrogen concentration in the liquid to be measured is corrected according to the electrical conductivity of the liquid to be measured.

17. The method for measuring the dissolved hydrogen concentration according to claim 16, wherein the obtained dissolved hydrogen concentration is corrected by adding a hydrogen concentration difference or multiplying by a hydrogen concentration ratio to the obtained dissolved hydrogen concentration.

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