Electrochemical measuring device

Abstract

To execute electrochemical measurement precisely.SOLUTION: An electrochemical measuring device includes a first holding section, a first working electrode dipped into a first solution, a first counter electrode dipped into the first solution, a second holding section that holds a second solution and is a holding section different from the first holding section, a third holding section for holding a third solution in a state while liquid-joining it with the second solution of the second holding section, a reference electrode dipped into the second solution, a second working electrode that is electrically connected to the first working electrode and is dipped into the second solution or the third solution, a second counter electrode that is electrically connected to the first counter electrode, and is dipped into solution into which the second working electrode is not dipped from among the second solution and the third solution, and a potential control section for sweeping the potential of the first working electrode, and measures the total current obtained by adding a first current flowing to the first counter electrode through the first solution from the first working electrode and a second current flowing to the second counter electrode through the second solution and the third solution from the second working electrode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrochemical measurement device. [Background technology]

[0002] Research on electrochemical measurements is not only important for the development of electrochemistry as a basic science, but is also highly valued because it can be applied to industrial fields such as batteries, displays, and sensors.

[0003] One example of a technique relating to electrochemical measurement is the electrochemical measurement unit described in Patent Document 1. This electrochemical measurement unit is for flow measurement, and is an electrochemical measurement unit for flow measurement in which a cell having a pair of a reference electrode and a working electrode is connected to one or more other cells having another working electrode, and the electrochemical measurement unit has a pair of electrodes made of a conductive material on the upstream and downstream sides of the electrochemical measurement unit, and the pair of electrodes made of a conductive material are kept at the same potential and used as counter electrodes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 07-103936 Summary of the Invention [Problem to be solved by the invention]

[0005] However, since this electrochemical measurement unit requires the reference electrode to be immersed in the sample, electrochemical measurement can only be performed under measurement conditions in which a special reference electrode can be used or in which the reference electrode can be used normally. Furthermore, if the reference electrode is inserted into a tank or the like other than the connected cell and the cell and the tank or the like are connected with a salt bridge, liquid junction, or the like, electrochemical measurement can only be performed under measurement conditions in which the salt bridge, liquid junction, or the like can be used normally.

[0006] Therefore, an object of the present invention is to provide an electrochemical measurement apparatus capable of performing electrochemical measurements with high accuracy under a wider variety of measurement conditions. [Means for solving the problem]

[0007] One aspect of the present invention includes a first holding part holding a first solution having a measurement substance concentration equal to or higher than a first threshold value, a first working electrode immersed in the first solution, a first counter electrode immersed in the first solution, a second holding part which holds a second solution having the same concentration as the first solution and is different from the first holding part, a third holding part which holds a third solution having a measurement substance concentration equal to or lower than a second threshold value which is smaller than the first threshold value in a liquid junction with the second solution in the second holding part, a reference electrode immersed in the second solution, a second working electrode electrically connected to the first working electrode and immersed in the second solution or the third solution, and the first counter electrode. the second working electrode is immersed in one of the second solution and the third solution, whichever is not immersed in the second working electrode; and a potential control unit electrically connected to the first working electrode, the first counter electrode, the second working electrode, the second counter electrode, and the reference electrode, and configured to sweep the potential of the first working electrode by sweeping the potential difference between the second working electrode and the reference electrode, and the electrochemical measurement device measures a total current consisting of a first current flowing from the first working electrode to the first counter electrode through the first solution and a second current flowing from the second working electrode to the second counter electrode through the second solution and the third solution.

[0008] In one aspect of the present invention, the above-described electrochemical measurements apparatus further includes a fourth holding unit that holds the reference electrode in a liquid junction with the second solution without being immersed in the second solution. Effect of the Invention

[0009] According to the present invention, electrochemical measurements can be performed with high accuracy under a wider variety of measurement conditions. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of an electrochemical measurement apparatus according to an embodiment of the present invention. [Diagram 2] 11 is a diagram showing an example of a configuration of a third holding unit of the present embodiment. FIG. [Diagram 3] FIG. 13 is a diagram showing an example of the results of cyclic voltammetry performed by the electrochemical measurement apparatus according to the present embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a potential difference between electrodes according to the embodiment. [Diagram 5] FIG. 13 is a diagram showing an example of the measurement results in the case of a neutral solution. [Figure 6] FIG. 13 is a diagram showing an example of the measurement results in the case of a basic solution. [Figure 7] FIG. 13 is a diagram showing a modified example of the configuration of the electrochemical measurements apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The electrochemical measurement apparatus according to the embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing an example of the configuration of the electrochemical measurement apparatus according to the present embodiment. As shown in Fig. 1, the electrochemical measurement apparatus 1 includes a first holding unit 11, a first working electrode 12, a first counter electrode 13, a second holding unit 21, a second working electrode 22, a second counter electrode 23, a reference electrode 30, and a potential controller 40.

[0012] The first holding unit 11 is an electrolytic cell that holds a first solution L1 in which the concentration of the measured substance is equal to or higher than a first threshold value. The first solution L1 is an electrolyte solution in which an aqueous sodium sulfate solution having a concentration of 0.1 M (molar) as an example of an electrolyte and potassium ferrocyanide (K4[Fe(CN)6]) having a concentration of 25 mM (millimolar) as an example of a measured substance are dissolved. In the following description, the first solution L1 is also referred to as a “first sample solution” or simply as a “sample solution.” The first holding unit 11 is also referred to as a “first electrolytic bath” or a “first sample solution bath.”

[0013] The first threshold value here is, for example, 25 mM to 3 mM, and is a threshold value greater than a second threshold value described later, and is preferably a threshold value sufficiently greater than the second threshold value. Furthermore, since there is no reference electrode 30 in the first holding unit 11, the first solution L1 may be under conditions such as high temperature and high pressure, and the first holding unit 11 may be a microelectrolytic bath.

[0014] The first working electrode 12 is an electrode immersed in the first solution L1. For example, the first working electrode 12 is a cylindrical platinum electrode, and the side surface is covered with a cylindrical coating 12C. The coating 12C is made of, for example, polyether ether ketone (PEEK) and is in close contact with the side surface of the first working electrode 12 so that the first solution L1 does not penetrate between the side surface of the first working electrode 12 and the coating 12C. In addition, the end surface of the first working electrode 12 is polished before electrochemical measurement is performed using the electrochemical measurement device 1, and is in contact with the first solution L1.

[0015] The first counter electrode 13 is an electrode immersed in the first solution L1. For example, the first counter electrode 13 is a mesh-shaped platinum electrode.

[0016] The second holding unit 21 is an electrolytic cell that holds a second solution L2, which is a solution having the same components as the above-mentioned first holding unit 11. That is, the second holding unit 21 is an electrolytic cell that holds a second solution L2 in which the concentration of the measured substance is equal to or higher than a first threshold value. The second solution L2 is an electrolyte solution in which an aqueous sodium sulfate solution having a concentration of 0.1 M (molar) as an example of an electrolyte and potassium ferrocyanide (K4[Fe(CN)6]) having a concentration of 25 mM (millimolar) as an example of a measured substance is dissolved. In the following description, the second solution L2 is also referred to as a “second sample solution” or simply as a “sample solution.” In addition, the second holding unit 21 is also referred to as a “second electrolytic bath” or a “second sample solution bath.”

[0017] The second counter electrode 23 is an electrode immersed in the second solution L2. For example, the second counter electrode 23 is a mesh-shaped platinum electrode. The second counter electrode 23 is electrically connected to the first counter electrode 13. For example, the second counter electrode 23 is electrically connected to the first counter electrode 13 by a conductor 60. The shape, material, arrangement, etc. of the conductor 60 are arbitrary and may be designed freely.

[0018] The reference electrode 30 is a reference electrode immersed in the second solution L2. For example, the reference electrode 30 is a silver-silver chloride electrode, and has a structure in which a silver member having a silver surface coated with silver chloride is immersed in an aqueous chloride solution held in a glass tube.

[0019] The third holding unit 31 is an electrolytic cell that holds a third solution L3 in which the concentration of the measured substance is equal to or less than a second threshold value. The third solution L3 is an aqueous solution of sodium sulfate having a concentration of 0.1 M (molar) as an example of an electrolyte, in which potassium ferrocyanide as an example of a measured substance is not dissolved. In other words, the third solution L3 is an electrolyte solution containing sodium sulfate as an electrolyte. In the following description, the third solution L3 is also referred to as a “supporting electrolyte solution.” Moreover, the third holding unit 31 is also referred to as a “third electrolytic cell,” a “sample holder,” or simply a “holder.”

[0020] The second threshold value here is a threshold value smaller than the above-mentioned first threshold value, and is preferably a threshold value sufficiently smaller than the first threshold value, and may be zero.

[0021] 2 is a diagram showing an example of the configuration of the third holding unit 31 of this embodiment. The third holding unit 31 is, for example, a cylindrical glass tank, and is provided with a liquid junction 32 at its bottom. The liquid junction 32 is made of, for example, porous glass, and provides electrical conductivity between the solution inside the third holding unit 31 (i.e., the third solution L3) and the solution outside the third holding unit 31 (i.e., the second solution L2).

[0022] The second working electrode 22 is an electrode immersed in the third solution L3 inside the third holding unit 31. For example, the second working electrode 22 is a cylindrical platinum electrode, and the side surface is covered with a cylindrical coating 22C. The coating 22C is made of, for example, polyether ether ketone, and is in close contact with the side surface of the second working electrode 22 so that the third solution L3 does not penetrate between the side surface of the second working electrode 22 and the coating 22C. In addition, the end surface of the second working electrode 22 is polished before the electrochemical measurement using the electrochemical measurement device 1 is performed, and is in contact with the third solution L3. In addition, the second working electrode 22 is electrically connected to the first working electrode 12. For example, as shown in FIG. 1, the second working electrode 22 is electrically connected to the first working electrode 12 by a conductor 50. In addition, the shape, material, arrangement, etc. of the conductor 50 are arbitrary and may be freely designed.

[0023] The potential control unit 40 is, for example, a potentiostat, and is electrically connected to the first working electrode 12, the first counter electrode 13, the second working electrode 22, the second counter electrode 23, and the reference electrode 30, and sweeps the potential difference between the second working electrode 22 and the reference electrode 30. As a result, the first working electrode 12 is electrically connected to the second working electrode 22 by the conductor 50, and the potential control unit 40 can sweep the potential of the first working electrode 12. As a result, the potential control unit 40 can perform electrochemical measurement by the electrochemical measurement device 1, for example, cyclic voltammetry (CV). Voltammetry).

[0024] Fig. 3 is a diagram showing an example of the result of cyclic voltammetry performed by the electrochemical measurement apparatus according to this embodiment. The horizontal axis of Fig. 3 represents the potential of the first working electrode 12. The vertical axis of Fig. 3 represents the current flowing through the first working electrode. In other words, Fig. 3 shows a cyclic voltammogram obtained by the electrochemical measurement apparatus 1. In the following description, the measurement method using the electrochemical measurement apparatus of this embodiment is also referred to as NCS-RE (Non Contact Solution-Reference Electrode). In addition, when the measurement method using the electrochemical measurement apparatus of this embodiment is to be distinguished from the conventional NCS-RE that does not use the third holding unit 31, the measurement method using the electrochemical measurement apparatus of this embodiment is also referred to as holder-using NCS-RE.

[0025] 3, the potential control unit 40 repeats three times a process of increasing the potential of the first working electrode 12 from a starting potential of 0.0 V to a maximum potential of +0.7 V, decreasing the potential of the first working electrode 12 from the maximum potential of +0.7 V to a minimum potential of -0.4 V, and then increasing the potential of the first working electrode 12 from the minimum potential of -0.4 V to a starting potential of 0.0 V. In this case, the potential control unit 40 always sweeps the potential of the first working electrode 12 at a constant sweep speed of 20 mV / s. The starting potential is a potential at which no electrode reaction occurs.

[0026] In FIG. 3, when the potential of the first working electrode 12 is increasing, the ferricyanide ion [Fe(CN)6] is 4- The oxidation reaction of ferricyanide ion [Fe(CN)6] occurs. 3- and electrons (e - ) is occurring.

[0027] The electrons generated by this oxidation reaction (e - ) flows into the first working electrode 12. When the potential of the first working electrode 12 is reaching +0.3 V, the reaction rate of the oxidation reaction increases rapidly, and the electrons (e - ) increases suddenly, causing a sudden increase in the current in the positive direction.

[0028] The hexacyanidoferrate(III) ion [Fe(CN)6] generated by this oxidation reaction 3-is retained near the end surface of the first working electrode 12. When the potential of the first working electrode 12 exceeds +0.3 V and starts to move away from +0.3 V, most of the chemical species present near the end surface of the first working electrode 12 are ferricyanide ions [Fe(CN)6] 3- As a result, the electrons (e - ) decreases suddenly, so the current in the positive direction decreases suddenly.

[0029] This is believed to be why an upward peak appears near +0.3 V in the cyclic voltammogram shown in FIG. 3. When the potential of the first working electrode 12 increases in FIG. 3, the electrons (e - ) causes some kind of reduction reaction. For example, the reduction reaction of water (H2O) occurs, producing hydrogen (H2) and hydroxide ions (OH - ) occurs.

[0030] In FIG. 3, when the potential of the first working electrode 12 is decreasing, the end face of the first working electrode 12 is charged with ferricyanide ions [Fe(CN)6] 3- The reduction reaction of ferricyanide ion [Fe(CN)6] occurs, and the ferricyanide ion [Fe(CN)6] 4- is occurring.

[0031] This reduction reaction produces the hexacyanidoferrate(III) ion [Fe(CN)6] 3- The electrons acquired by (e - ) is supplied from the end face of the first working electrode 12. When the potential of the first working electrode 12 is reaching +0.2 V, the reaction rate of the reduction reaction increases rapidly, and electrons (e - ) increases suddenly, causing a sudden increase in the current in the negative direction.

[0032] The hexacyanidoferrate(II) ion [Fe(CN)6] generated by this reduction reaction 4-is retained near the end surface of the first working electrode 12. When the potential of the first working electrode 12 falls below +0.2 V and begins to move away from +0.2 V, most of the chemical species present near the end surface of the first working electrode 12 are ferricyanide ions [Fe(CN)6] 4- As a result, electrons (e - ) to obtain the hexacyanidoferrate(III) ion [Fe(CN)6] 3- Since the current in the negative direction decreases rapidly due to the decrease in

[0033] Therefore, it is considered that a downward peak appears near +0.2 V in the cyclic voltammogram shown in FIG. 3. When the potential of the first working electrode 12 is decreasing in FIG. 3, the electrons (e - The ferricyanide ion [Fe(CN)6], which is present in large quantities as the measurement substance, is used to offset the charge bias generated by the 4- The oxidation reaction proceeds.

[0034] In addition, the intermediate potential between the upward peak near +0.3 V and the downward peak near +0.2 V in the cyclic voltammogram shown in Figure 3 corresponds to the ferricyanide ion [Fe(CN)6]. 4- and ferricyanide ion [Fe(CN)6] 3- This potential can be approximated to the reversible half-wave potential of 100 kcal / mol. This potential can be further approximated to the standard redox potential.

[0035] The figure also shows an example of the results of cyclic voltammetry performed by an electrochemical measurement device that employs a general three-electrode method, as well as the results of cyclic voltammetry performed by a conventional NCS-RE. The results of cyclic voltammetry using the NCS-RE with the holder of this embodiment were shown to be in good agreement with the results of cyclic voltammetry performed using an electrochemical measurement device employing a general three-electrode method.

[0036] In FIG. 3, when the surface charge of the first working electrode 12 is at a positive potential, i.e., when the surface charge of the second working electrode 22 is at a positive potential, negatively charged sulfate ions (SO 2- ), hydroxide ion (OH - ) and other positively charged sodium ions (Na + ), oxoium ion (HO + 3, when the surface charge of the first working electrode 12 is at a negative potential, that is, when the surface charge of the second working electrode 22 is at a negative potential, sodium ions (Na + ), oxoium ion (HO + ) and the like gather near the surface of the second counter electrode 23, and hydroxide ions (OH - These two states of the second solution L2 are called an electric double layer.

[0037] The electrochemical measurement apparatus 1 according to the embodiment has been described above. The electrochemical measurement apparatus 1 sweeps the potential difference between the second working electrode 22 and the reference electrode 30, and sweeps the potential of the first working electrode 12 electrically connected to the second working electrode 22 via the conductor 50. Furthermore, the electrochemical measurement apparatus 1 does not need to immerse the reference electrode 30 in the first holding unit 11 that holds the first solution L1 in which the first working electrode 12 is immersed.

[0038] Therefore, the electrochemical measurement device 1 can perform electrochemical measurement of the measured substance even under conditions in which the reference electrode 30 cannot be used normally. The conditions in which the reference electrode 30 cannot be used normally are, for example, conditions in which the first solution L1 in which the concentration of the measured substance is equal to or higher than the first threshold value is at high temperature or high pressure, and conditions in which the first holding unit 11 that holds the first solution L1 is very small. Furthermore, since the electrochemical measurement device 1 exerts such effects, it can be said to be useful in various research and industrial fields, such as research into the mechanism of chemical reactions that occur in solutions under ultra-high pressure and research into the behavior of batteries mounted on robots used under ultra-high temperatures.

[0039] Furthermore, in the holder-using NCS-RE of this embodiment, the same sample solution is held in both the first holding part 11 (first electrolytic bath) in which the first counter electrode 13 is immersed and the second holding part 21 (second electrolytic bath) in which the second counter electrode 23 is immersed. That is, in the holder-using NCS-RE of this embodiment, the first counter electrode 13 and the second counter electrode 23 are immersed in sample solutions of the same components.

[0040] FIG. 4 is a diagram showing an example of a potential difference between electrodes according to the present embodiment. FIG. 1A shows the potential difference between the first counter electrode 13 and the reference electrode 30, and the potential difference between the second counter electrode 23 and the reference electrode 30, in the conventional NCS-RE. FIG. 1B shows the potential difference between the first counter electrode 13 and the reference electrode 30, and the potential difference between the second counter electrode 23 and the reference electrode 30, when an NCS-RE using the holder of this embodiment is used.

[0041] Here, in the conventional NCS-RE, the first counter electrode 13 and the second counter electrode 23 are immersed in solutions having different components. For example, in the conventional NCS-RE, the first counter electrode 13 is immersed in a sample solution, and the second counter electrode 23 is immersed in a supporting electrolyte solution. On the other hand, in the holder-using NCS-RE of this embodiment, the first counter electrode 13 and the second counter electrode 23 are immersed in a solution of the same component. According to the holder-using NCS-RE of this embodiment, the potential difference between the first counter electrode 13 and the second counter electrode 23 during measurement is extremely small compared to the case where the first counter electrode 13 and the second counter electrode 23 are immersed in solutions of different components (for example, the first counter electrode 13 is immersed in a sample solution and the second counter electrode 23 is immersed in a supporting electrolyte solution). According to the NCS-RE using the holder of this embodiment configured in this manner, it is possible to obtain results with higher accuracy than when the first counter electrode 13 and the second counter electrode 23 are immersed in solutions with different components.

[0042] [Changing the solution pH] Figure 5 shows an example of the results of NCS-RE using a holder in the case of a neutral solution, in which the measured substance is potassium ferricyanide (K3[Fe(CN)6]). 6 shows an example of the results of NCS-RE using a basic solution holder, in which the measured substance is potassium ferricyanide (K3[Fe(CN)6]). As shown in the figure, when the sample solution is made basic by dissolving, for example, sodium hydroxide (NaOH) in the sample solution, better results that are closer to the results of the conventional three-electrode method can be obtained compared to when the sample solution is neutral. When the sample solution is neutral, electrolysis of water (i.e., oxidation reaction) occurs at the first counter electrode 13 and the second counter electrode 23. When electrolysis of water is performed using platinum, which is the material of the first counter electrode 13 and the second counter electrode 23, a large overvoltage is required, making it difficult for the reaction to occur smoothly. On the other hand, when the sample solution is basic, an oxidation reaction of hydroxide ions occurs at the first counter electrode 13 and the second counter electrode 23. In this case, the oxidation potential is lower than that in the electrolysis of water by platinum, and therefore the reactivity of the first counter electrode 13 and the second counter electrode 23 is improved.

[0043] [Variation: Measurement of organic systems] 7 is a diagram showing a modified example of the configuration of the electrochemical measurement apparatus according to this embodiment. In the above-described embodiment, the measurement in which the sample solution is aqueous has been described. This modified example differs from the above-described embodiment in that the reference electrode 30 is protected by the fourth holding unit 41 in the measurement in which the sample solution is non-aqueous solvent-based (i.e., when an organic solvent is used). That is, the electrochemical measurements apparatus 2 of this modified example includes a fourth holding unit 41. The fourth holding unit 41 is an electrolytic bath that holds a fourth solution L4 that is a supporting electrolyte solution. In the following description, the fourth holding unit 41 is also referred to as a "fourth electrolytic bath" or a "reference electrode holder." The fourth holding unit 41, like the above-described third holding unit 31, is, for example, a cylindrical glass tank, and is provided at its bottom with a liquid junction 42. The liquid junction 42 is made of, for example, porous glass, and is in electrical contact between the solution inside the fourth holding unit 41 (i.e., fourth solution L4) and the solution outside the fourth holding unit 41 (i.e., second solution L2).

[0044] That is, the fourth holding unit 41 holds the reference electrode 30 in a state of liquid junction with the second solution L2 without directly immersing the reference electrode 30 in the second solution L2. According to the electrochemical measurement device 2 configured in this manner, the fourth holding section 41 functions as a separator and can prevent an organic solution from flowing into the reference electrode 30, so that measurements can be performed even if the sample solution is a non-aqueous solvent system.

[0045] In the above embodiment, the electrochemical measurement apparatus 1 (or the electrochemical measurement apparatus 2 (the same applies in the following description) performs electrochemical measurement when the first solution L1 and the second solution L2 are not stirred. However, the present invention is not limited to this. For example, the electrochemical measurement apparatus 1 may perform electrochemical measurement when at least one of the first solution L1 and the second solution L2 is stirred.

[0046] In the above-described embodiment, the first holding unit 11 and the second holding unit 21 are tanks, but the present invention is not limited thereto. For example, the first holding unit 11 may be a tubular member through which the first solution L1 flows. Similarly, the second holding unit 21 may be a tubular member through which the second solution L2 flows. In these cases, it may be necessary to apply pressure to the first solution L1 in order to make it flow inside the tube, and therefore it is expected that electrochemical measurement using a principle similar to that of the electrochemical measurement device 1 will be effective.

[0047] In the above embodiment, the first solution L1 and the second solution L2 are electrolyte solutions, but the present invention is not limited to this. For example, at least one of the first solution L1 and the second solution L2 may be an ionic liquid.

[0048] In the above embodiment, the measurement substance is not dissolved in the second solution L2, but the measurement substance may be dissolved in the second solution L2.

[0049] Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and various modifications, substitutions, and / or design changes can be made without departing from the scope of the present invention. The configurations described in the above-mentioned embodiments may be combined. [Explanation of symbols]

[0050] Reference Signs List 1, 2: Electrochemical measurement device, 11: First holding part, L1: First solution, 12: First working electrode, 13: First counter electrode, 21: Second holding part, L2: Second solution, 22: Second working electrode, 23: Second counter electrode, 30: Reference electrode, 31: Third holding part, 32: Liquid junction, L3: Third solution, 40: Potential control part, 41: Fourth holding part, 42: Liquid junction, L4: Fourth solution, 50, 60: Conductor

Claims

1. a first holding unit that holds a first solution having a concentration of a substance to be measured that is equal to or higher than a first threshold; a first working electrode immersed in the first solution; a first counter electrode immersed in the first solution; A second holding section that holds a second solution having the same concentration as the first solution and is different from the first holding section; a third holding section that holds a third solution having a concentration of the measured substance equal to or less than a second threshold value that is smaller than the first threshold value, in a state where the third solution is in liquid junction with the second solution in the second holding section; a reference electrode immersed in the second solution; a second working electrode electrically connected to the first working electrode and immersed in the second solution or the third solution; a second counter electrode electrically connected to the first counter electrode and immersed in one of the second solution and the third solution, the other of which is not immersed in the second working electrode; a potential control unit electrically connected to the first working electrode, the first counter electrode, the second working electrode, the second counter electrode, and the reference electrode, and configured to sweep a potential difference between the second working electrode and the reference electrode, thereby sweeping a potential of the first working electrode; Equipped with An electrochemical measurement device that measures a total current obtained by combining a first current flowing from the first working electrode through the first solution to the first counter electrode and a second current flowing from the second working electrode through the second solution and a third solution to the second counter electrode.

2. a fourth holding section for holding the reference electrode in a state where the reference electrode is not immersed in the second solution but is in liquid junction with the second solution; The electrochemical measurement apparatus according to claim 1 , further comprising:

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