JP2009186460A - Flow electrolytic cell, and apparatus and method for quantifying density using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flow electrolytic cell comprising a working electrode filled with many linear conductors, the flow electrolytic cell being capable of improving analytic precision, easy to handle, and more quickly analyzing many sample solutions. <P>SOLUTION: This flow electrolytic cell 1 includes a case 1a having a reservoir 1L for accumulating an electrolyte solution, and the working electrode 2, a reference electrode 3, and a counter electrode 4 which are adjusted to a predetermined potential vialead wires 2A, 3A and 4A respectively, and attached to the case 1a, partly soaked in the electrolyte solution. The sample solution is fed to the working electrode 2 to electrolyze a target component contained therein. The working electrode 2 includes an insulating hollow pipe 20 and a bundle 21 of the linear conductors arranged and filled inside the hollow pipe 20 in parallel to an axial direction. The bundle 21 of the conductors is extended outside from a rear end portion 20b of the hollow pipe 20 and connected to the lead wire 2A at a position away from the reservoir 1L. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a flow electrolysis cell that applies a predetermined potential to a working electrode and electrolyzes almost all of the target components in a sample solution in order to measure the amount of charge required for electrolysis, and also uses the flow electrolysis cell. The present invention relates to a concentration determination apparatus and a concentration determination method.

  Analytical methods using a sample solution containing an electrochemically active target component as a flowing liquid are widely used in many fields such as process control in chemical industrial facilities and rapid analysis of specimens in the medical field and chemical field. Among these analytical methods, one of the main methods based on electrolysis is a method of electrolyzing almost all of the target components contained in the sample solution and measuring the amount of charge required for the electrolysis (flow coulometry). ) In this method, when the sample solution is supplied to the flow electrolysis cell, it is necessary to quickly electrolyze the target component and reach equilibrium. For this reason, the surface area ratio of the conductor of the working electrode with respect to the amount of the sample solution is increased by various methods. For example, in the flow electrolysis cell described in Patent Documents 1 to 3, the insulating hollow tube is filled with a large number of linear conductor carbon fibers to increase the surface area of the working electrode conductor, and the hollow electrolytic cell is hollow. The amount of the sample solution is reduced by reducing the inner diameter of the tube.

  5A is a schematic cross-sectional view showing a working electrode 102 similar to that described in Patent Document 1, and FIG. 5B shows a working electrode 102 similar to that described in Patent Documents 2 and 3. It is a cross-sectional schematic diagram showing '. In these, an insulating hollow tube 120 made of a Vycor glass tube or a quartz glass tube is filled with a carbon fiber bundle 121. Regarding the connection between the carbon fiber bundle 121 and the lead wire 122, in the former case, another glass tube 120A is provided in front of the hollow tube 120, and the lead wire 122 is connected to the outside from the outside with a larger diameter. A platinum tube 120B is provided, and a part of the carbon fiber bundle 121 is extended and fixed between another glass tube 120A and the platinum tube 120B. On the other hand, in the latter, a through hole is formed near the center of the longitudinal direction of the hollow tube 120 and a carbon electrode 120 ′ to which the lead wire 122 is connected from the outside is embedded so that it contacts the carbon fiber bundle 121. Yes.

JP-A-9-264869 Japanese Patent Laid-Open No. 9-292359 JP-A-10-19844

  However, in addition to the hollow tube 120 as in the former working electrode 102, another glass tube 120A and a platinum tube 120B are provided, or the hollow tube 120 is processed as in the latter working electrode 102 ′ so that the carbon electrode 120 is processed. In a structure in which 'is embedded, those flow electrolysis cells are easily damaged, and therefore must be handled with care and are expensive. Further, since the hollow tube 120 is a Vycor glass tube or a quartz glass tube, the tube itself is easily damaged. Therefore, in such a flow electrolysis cell, many sample solutions can be analyzed more quickly, and there is room for improvement in order to facilitate handling and further improve the accuracy of analysis.

  The present invention has been made in view of the above reasons, and its purpose is to improve the accuracy of analysis in a flow electrolysis cell filled with a large number of linear conductors to serve as a working electrode, and to handle it. It is an object of the present invention to provide a flow electrolysis cell that is easy to perform and can analyze many sample solutions more quickly.

  In order to achieve the above object, a flow electrolysis cell according to claim 1 is provided with a working electrode, a reference electrode, and a working electrode, each of which has a predetermined potential via each lead wire, in a housing having a liquid reservoir for storing an electrolyte solution. In a flow electrolysis cell in which a counter electrode is attached so as to be immersed in the electrolyte solution, and a sample solution is passed through the working electrode to electrolyze a target component contained therein, the working electrode includes an insulating hollow tube, a hollow tube A bundle of linear conductors arranged in parallel in the axial direction inside the tube, and the bundle of conductors extends outward from the rear end of the hollow tube. It is connected to the lead wire at a position away from the liquid reservoir.

  The flow electrolysis cell according to claim 2 is the flow electrolysis cell according to claim 1, wherein the hollow tube is made of polytetrafluoroethylene.

  The flow electrolysis cell according to claim 3 is the flow electrolysis cell according to claim 1 or 2, wherein the conductor is a carbon fiber.

  A concentration quantification device according to claim 4 is a concentration quantification device comprising the flow electrolysis cell according to any one of claims 1 to 3, and measures the amount of a sample solution in which the target component is electrolyzed by a working electrode. And further comprising an analytical balance.

  The concentration quantification device according to claim 5 is the concentration quantification device according to claim 4, wherein a sample solution container for storing the sample solution, a liquid feeding tube for sending the sample solution from the sample solution container to the working electrode, The analytical balance is characterized by measuring the weight of the casing of the flow electrolysis cell or measuring the weight of the sample solution container.

  The concentration quantification method according to claim 6 is a concentration quantification method using the concentration quantification device according to claim 5, wherein the liquid surface of the liquid reservoir of the flow electrolysis cell and the working electrode are close to each other. By measuring the weight with the analytical balance while controlling so that the liquid level of the sample solution in the sample solution container and the liquid feeding tube are close to each other, It is characterized by quantifying the concentration of the target component contained in the sample solution.

  According to the flow electrolysis cell of the present invention, the working electrode is filled with a large number of linear conductors, and the working electrode is arranged in parallel with the insulating hollow tube and the inside of the hollow tube in the axial direction. A bundle of linear conductors arranged and filled, and the conductor bundle extends outward from the rear end of the hollow tube and leads away from the liquid reservoir. Because the lead wire is in contact with the sample solution, the potential window is reliably prevented from changing, and the liquid flow is less likely to be disturbed at the working electrode, improving the accuracy of the analysis. In addition, since the structure is simple and strong, handling becomes easy, and many samples can be analyzed quickly. In addition, when this flow electrolysis cell is used, it is possible to calculate the concentration with high accuracy.

It is a schematic diagram which shows the concentration determination apparatus containing the flow electrolysis cell which concerns on embodiment of this invention. It is a schematic diagram which shows another concentration determination apparatus same as the above. It is the perspective view which looked at the working electrode of the flow electrolysis cell same as the above. It is a graph which shows the experimental result using the flow electrolysis cell same as the above. It is a schematic sectional drawing which shows the working electrode of the conventional flow electrolysis cell.

  Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a concentration determination device 10 including a flow electrolysis cell 1 according to an embodiment of the present invention. The flow electrolysis cell 1 can be used not only for concentration determination using the concentration determination apparatus 10, but also for elucidation of electrolytic synthesis and electrolytic reaction mechanism, and concentration of metal ions.

  A glass casing 1a serving as a basic structure of the flow electrolysis cell 1 has a liquid reservoir 1L for accumulating an electrolyte solution, and has a predetermined potential via the lead wires 2A, 3A, and 4A. The electrode 2, the reference electrode 3, and the counter electrode 4 are attached so as to be immersed in the electrolyte solution in the liquid reservoir 1 </ b> L directly or through the sample solution flowing to the working electrode 2. The casing 1a has a bottomed cylindrical shape that is slightly swollen in the lower part, the upper substantially cylindrical part is the working electrode attaching part 1A, the lower cylindrical part is the liquid reservoir part 1L, and obliquely upward from the lower cylindrical part The portions that are formed to project are the reference electrode attachment portion 1B and the counter electrode attachment portion 1C.

  The working electrode 2 includes an insulating hollow tube 20 and a bundle of linear conductors 21 filled in the hollow tube 20 so as to be arranged in parallel in the axial direction. Attach to 1A. The hollow tube 20 is a tube having an inner diameter of about 1 mm, and a front end portion (upper end portion in FIG. 1) 20a protrudes from the upper end portion of the housing 1a when attached to the housing 1a. Further, the hollow tube 20 has a length at which the rear end portion (the lower end portion in FIG. 1) 20b reaches or almost reaches the liquid surface 1LS of the electrolyte solution stored in the liquid reservoir 1L. Thereby, the working electrode 2 is immersed in the electrolyte solution in the liquid reservoir 1L directly or through the sample solution flowing through the working electrode 2. The front end 20 a of the hollow tube 20 is connected to the liquid feeding tube 6. A sample solution, which is an electrolyte solution to which the target component is added, is stored in a sample solution container 7A, and is supplied from the sample solution container 7A through a liquid feeding tube 6 at a substantially constant speed by a liquid feeding pump (for example, a peristaltic pump) 7. The sample solution that has been sent to the working electrode 2 and passed through the working electrode 2 is mixed with the electrolyte solution originally stored in the liquid reservoir 1L. The configuration, material, dimensions, connection with the lead wire 2A, etc. of the working electrode 2 will be described in detail later.

  The reference electrode 3 is made of, for example, glass, has a tubular shape, a conductor 31 having a known shape (for example, a spiral shape) is disposed therein, and a diaphragm 32 is attached to an inner end thereof, so that an electrolyte solution is supplied. It is sealed and attached to the reference electrode attachment portion 1B using the fixing material 33. The conductor 31 is immersed in the electrolyte solution. Further, the diaphragm 32 is positioned so as to be immersed in the electrolyte solution stored in the liquid reservoir 1L, and the supporting electrolyte can pass between the electrolyte solution and the sealed electrolyte solution. The conductor 31 is taken out through the plug 34 at the outer end located outside the housing 1a of the reference electrode 3 and connected to the lead wire 3A.

  The counter electrode 4 is disposed so that a conductor 41 having a known shape (for example, a spiral shape) is immersed in an electrolyte solution stored in the liquid reservoir 1L, and is attached to the counter electrode attachment 1C by a plug member 44. The conductor 41 is taken out through the material 44 and connected to the lead wire 4A.

  The conductor bundle 21 of the working electrode 2, the conductor 31 of the reference electrode 3, and the conductor 41 of the counter electrode 4 are set to a predetermined potential by the potentiostat 8 via the respective lead wires 2A, 3A, 4A. That is, a potential that causes the target component contained in the sample solution to be sufficiently electrolyzed by oxidation or reduction reaction is applied to the working electrode 2 with respect to the reference electrode 3. The current flowing between the working electrode 2 and the counter electrode 4 due to the oxidation or reduction reaction of the target component is converted into a charge amount by the coulomb meter 9.

  Next, the working electrode 2 will be described in detail. The hollow tube 20 of the working electrode 2 has a small inner diameter so that the amount of the sample solution can be reduced. Therefore, the hollow tube 20 is a material that is durable against various sample solutions, and is hard to break and strong. desirable.

  In these respects, the hollow tube 20 is optimally made of polytetrafluoroethylene (PTFE), specifically, made of Teflon (registered trademark of DuPont, USA). The hollow tube 20 formed of such a material is durable to both acidic and alkaline sample solutions and to organic solvents, and breaks even if the outer diameter is about 2 mm. It is difficult and strong. Moreover, it is rich in flexibility and can be bent or spiraled in the axial direction, and further miniaturization can be achieved. In addition, the length of the working electrode 2 can be freely adjusted by changing the length in the axial direction according to the type of the sample solution and cutting it from a long tube of raw materials. Even if the electrode reaction of redox is slow, almost all electrolysis can be performed by making the working electrode 2 longer. Therefore, it becomes easy to analyze the oxidation-reduction behavior of harmful substances such as arsenic acid and phenols or biological substances such as ascorbic acid and NADH.

  As shown in FIG. 3, a bundle of linear conductors 21 of the working electrode 2 is filled with a bundle of conductors 21 composed of a number of conductors 21a, 21a,. Yes. The front end of the bundle of conductors 21 is substantially aligned with the front end 20a of the hollow tube 20, and the rear end extends sufficiently long from the rear end 20b of the hollow tube 20 as shown in FIG. ing. Specifically, it is folded back by 180 degrees and extends outward of the working electrode attachment portion 1A of the housing 1a along the hollow tube 20. And it is connected to the lead wire 2A made of metal such as platinum, for example, at a position away from the liquid reservoir 1L, that is, a position surely separated from the region where the electrolyte solution can exist. In the bundle of conductors 21, most of the portion from the back end 20b of the hollow tube 20 until it is connected to the lead wire 2A is agglomerated so that the electrolyte solution does not enter the gap, and the electrolyte solution (mixed sample) It is covered with the covering tape 22 so as not to react with the electrode.

  For the conductors 21a, 21a,... Of the working electrode 2, carbon fibers having a diameter of, for example, about 10 μm are used. The carbon fiber has a wide potential window so that the redox electrode reaction of the target component can proceed appropriately. On the other hand, the carbon fiber is flexible and hardly breaks even when bent. A conductor having properties and performance similar to those of carbon fibers may be used.

  The above-described connection to the lead wire 2A at the rear end of the bundle of conductors 21 is performed by winding the lead wire 2A around the rear end of the conductor bundle 21 and electrically connecting them. By winding the lead wire 2A, the periphery of the bundle of conductors 21 can be uniformly and uniformly connected to the lead wire 2A. Although not shown, the covering tape 22 may be extended or covered with another covering tape or a heat-shrinkable tube so as to be crimped.

  The casing 1 a to which the working electrode 2, the reference electrode 3, and the counter electrode 4 are attached is placed on the upper plate of the analytical balance 5. With this analytical balance 5, the amount of the sample solution in which the target component is electrolyzed by the working electrode 2 is determined by measuring the weight of the housing 1a before and after the sample solution. The measurement value obtained by the analytical balance 5 is used in quantitative analysis such as calculation of the concentration of the target component in the sample solution. Thereby, it is possible to perform highly accurate analysis without depending on the set value of the liquid feed pump 7 or the like. This is because the amount of the sample solution is small and the flow electrolysis cell 1 is small and light, so that the weight can be measured with high accuracy.

  The analytical balance 5 may measure the weight of the sample solution container 7A in which the sample solution is stored, like the concentration determination device 10 'shown in FIG. In this case, the sample solution container 7A is placed on the top plate of the analytical balance 5, and the amount of the sample solution whose target component is electrolyzed by the working electrode 2 is analyzed for the weight of the sample solution container 7A before and after that. It calculates | requires by measuring with the balance 5. In this way, as described above, high-precision analysis can be performed without depending on the set value of the liquid feed pump 7 or the like. Further, the sample solution container 7A is usually smaller in weight value than the housing 1a to which the working electrode 2, the reference electrode 3, and the counter electrode 4 are attached, and has a simple structure, so there are few error factors. In addition, there is an advantage in reading the weight value, as will be described later in Experiment 2 or the like. Note that, if the upper part of the sample solution container 7A is thinned as shown in FIG. 2, evaporation of the sample solution can be suppressed, which contributes to highly accurate measurement.

  Next, the usage method of the flow electrolysis cell 1 is demonstrated. First, the electrolyte solution is stored in the liquid reservoir 1L of the housing 1a, and the working electrode 2, the reference electrode 3, and the counter electrode 4 are immersed therein. There may be a slight distance between the working electrode 2 and the liquid level 1LS. Then, the sample solution is sent to the working electrode 2 by the liquid feed pump 7. The sample solution flowing into the hollow tube 20 of the working electrode 2 passes through the gaps between the conductors 21a, 21a,. The target component contained in the sample solution is oxidized and reduced by the conductors 21a, 21a,... Having a predetermined potential, and the sample solution flows out of the hollow tube 20. By the end of passing through the hollow tube 20, almost all of the target component is electrolyzed, and then the amount of charge required for electrolysis is measured. Further, the weight at that time is measured with the analytical balance 5.

  Here, since the bundle of conductors 21 is a fixed linear shape from the front end 20a to the rear end 20b of the hollow tube 20, the flow direction of the sample solution that has flowed in is not disturbed, that is, turbulence occurs. Instead, the sample solution passes through the entire section of the hollow tube 20. Further, since the conductor bundle 21 is connected to the lead wire 2A at a position surely separated from the region where the electrolyte solution including the mixed sample solution can exist, the lead wire 2A comes into contact with the electrolyte solution and is oxidized and reduced. By reacting, the potential window does not change, and it is possible to prevent an error from occurring in the measurement of the charge amount.

  In this way, the flow electrolysis cell 1 is capable of high-precision analysis even if the inner diameter of the hollow tube 20 is reduced, and has a simple and strong structure. As a result, the analysis can be performed in a short time by reducing the amount of the sample solution in a place where analysis of many samples is required in the chemical or medical fields. Moreover, since it is easy to carry and handle, analysis on site is easy.

FIG. 4 shows the experimental results of Experiment 1 in which a cyclic voltammogram was obtained using the flow electrolysis cell 1 in order to confirm the performance of the flow electrolysis cell 1. The horizontal axis is the potential of the working electrode 2 with respect to the reference electrode 3, and the vertical axis is the current value. The sample solution contains 0.5 mM [Fe (CN) ₆ ] ³⁻ as a target component and 1MKCl as a supporting electrolyte. While feeding from the liquid feeding pump 7 at 0.2 ml / min, the potential of the working electrode 2 was changed at a sweep speed of 1 mV / min and recorded. The conductor 31 of the reference electrode 3 was silver / silver chloride. The electrolyte solution stored in the liquid reservoir 1L uses 1MKCl as a supporting electrolyte. The solid curve A ₁ in the figure is a voltammogram showing the results. A broken line curve A _{2 in} the figure is a voltammogram of a result obtained for a sample solution containing only 1 MKCl for comparison with the curve A ₁ .

Curve _{A 1} is a steep curve in the range of potentials from about 0.15～0.35V. This is an ideal curve showing a reversible one-electron reduction reaction. Since the current value (about −200 μA) is almost constant on the negative potential side of the range, a stable reduction reaction of almost 100% occurs. In addition, since the current value is almost zero on the positive potential side of the range, it can be seen that the residual current (background current) is small. Therefore, it can be seen that the flow electrolysis cell 1 has a good SN ratio and can perform quantitative analysis with high accuracy.

  Next, a concentration determination method capable of calculating concentration with extremely high accuracy will be described. This concentration quantification method uses the concentration quantification apparatus 10 ′ shown in FIG. 2. When the weight value of the sample solution container 7A is read by the analytical balance 5, the sample solution in the sample solution container 7A is measured. The weight is measured while controlling the liquid surface 7LS and the liquid feeding tube 6 to approach each other. This is because, when the liquid feeding tube 6 has entered the sample solution, the value of the weight to be read is changed by the buoyancy to the liquid feeding tube 6, so that the influence due to the presence of the liquid feeding tube 6 is minimized. . In order to minimize the influence due to the presence of the liquid feeding tube 6, it is ideal to measure the liquid feeding tube 6 away from the liquid surface 7LS, but bubbles are introduced. Therefore, a state in which the end of the liquid feeding tube 6 is slightly pulled up by the liquid level 7LS, that is, a state in which a sample solution due to the interfacial tension slightly exists between the end of the liquid feeding tube 6 and the liquid level 7LS is preferable. The distance between the end of the liquid feeding tube 6 and the liquid level 7LS may be controlled at least when the weight value of the sample solution container 7A is read by the analytical balance 5.

  The distance between the end of the liquid feeding tube 6 and the liquid level 7LS is most easily controlled by a human hand, but the height of the liquid level 7LS is automatically recognized using a known image recognition technique. By doing so, the height of the liquid feeding tube 6 may be automatically controlled.

Experiment 2 was conducted to verify this concentration determination method. The sample solution contains Fe ³⁺ having a predetermined concentration as a target component and 1M H ₂ SO ₄ as a supporting electrolyte. The electrolyte solution stored in the liquid reservoir 1L uses 1MH ₂ SO ₄ as a supporting electrolyte. The conductor 31 of the reference electrode 3 was silver / silver chloride. The potential of the working electrode 2 is set to 0.2 V, which is a potential at which Fe ³⁺ is reduced to 100% by Fe ²⁺ , and the sample solution container 7A is fed before and after being fed from the feed pump 7 at a flow rate of 0.2 ml / min for 20 minutes. This was repeated 5 times to read the weight value and determine the accuracy. Then, the theoretical value of the charge amount was obtained from the weight obtained with the analytical balance 5, and the electrolytic efficiency was calculated by comparing with the experimental value of the charge amount obtained with the coulomb meter 9. The charge amount obtained by the coulomb meter 9 is subtracted from the charge amount due to the background current. Table 1 shows the results of the electrolytic efficiency calculation performed when the Fe ³⁺ concentration of the sample solution is 5 × 10 ⁻⁴ M, 1 × 10 ⁻⁴ M, and 5 × 10 ⁻⁵ M. From Table 1, the accuracy of electrolysis efficiency is ± 0.1 to ± 0.2%, which is extremely high accuracy. Therefore, it can be seen that this concentration determination method can calculate the concentration with extremely high accuracy.

  In the concentration quantification method using the concentration quantification apparatus 10 shown in FIG. 1, the liquid level 1 LS of the liquid reservoir 1 L of the flow electrolysis cell 1 and the working electrode 2 in order to suppress the influence of buoyancy on the working electrode 2 and the like. It is also possible to control so as to approach each other. In this case, due to the complexity of the structure of the working electrode 2, the control of the distance between the liquid level 1LS and the working electrode 2 is much easier than the concentration quantification method using the concentration quantification apparatus 10 ′ shown in FIG. However, the height of the working electrode 2 may be automatically controlled using known image recognition technology and position control technology, or the liquid level 1LS may be kept constant by providing a discharge port in the housing 1a. it can.

  The flow electrolysis cell according to the embodiment of the present invention has been described above, but the present invention is not limited to that described in the above-described embodiment, and various processes within the scope of the matters described in the claims. Design changes are possible. For example, it is arbitrary to change the shape of the case 1a, and an opening that can be opened and closed is provided in the case 1a at the top of the liquid reservoir 1L. When the analysis of one sample is completed, it is opened and collected. It is also possible to continuously analyze other sample solutions by discharging a part of the electrolyte solution including the sample solution.

DESCRIPTION OF SYMBOLS 1 Flow electrolysis cell 1a Case 1L Liquid reservoir 1LS Liquid level of liquid reservoir 2 Working electrode 2A Lead wire of working electrode 20 Hollow tube 20a Front end of hollow tube 20b Rear end of hollow tube 21 Working electrode Conductor bundle 21a Conductor constituting conductor bundle 3 Reference electrode 4 Counter electrode 5 Analytical balance 6 Liquid feed tube 7 Liquid feed pump 7A Sample solution container 7LS Liquid surface of sample solution container 8 Potentiostat 9 Coulomb meter 10 Concentration determination device

Claims (6)

A working electrode, a reference electrode, and a counter electrode that are set to a predetermined potential via each lead wire are attached to a housing having a liquid reservoir for storing an electrolyte solution so that the sample solution is immersed in the electrolytic solution. In a flow electrolysis cell that electrolyzes the target component contained in
The working electrode includes an insulative hollow tube and a bundle of linear conductors filled in the hollow tube so as to be arranged in parallel in the axial direction. A flow electrolysis cell characterized in that it extends outward from the rear end of a hollow tube and is connected to the lead wire at a position away from the liquid reservoir. The flow electrolysis cell according to claim 1,
The flow electrolytic cell, wherein the hollow tube is made of polytetrafluoroethylene. In the flow electrolysis cell according to claim 1 or 2,
The flow electrolysis cell, wherein the conductor is a carbon fiber. A concentration determination apparatus comprising the flow electrolysis cell according to any one of claims 1 to 3,
A concentration determination apparatus, further comprising an analytical balance for measuring the amount of a sample solution in which the target component is electrolyzed by a working electrode. The concentration determination apparatus according to claim 4,
A sample solution container for storing the sample solution;
A feeding tube for sending the sample solution from the sample solution container to the working electrode, and
The concentration quantification apparatus, wherein the analytical balance measures the weight of the casing of the flow electrolysis cell or measures the weight of the sample solution container. A concentration determination method using the concentration determination device according to claim 5,
Control so that the liquid surface of the liquid reservoir of the flow electrolysis cell approaches the working electrode, or approach the liquid surface of the sample solution in the sample solution container and the liquid feeding tube. A concentration quantification method characterized in that the concentration of a target component contained in a sample solution is quantified by measuring the weight with the analytical balance while controlling as described above.

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