JP4637676B2 - Working electrode and electrochemical measurement apparatus using the same - Google Patents

Description

  The present invention relates to a working electrode for applying a voltage to an electrolyte solution and an electrochemical measurement apparatus using the working electrode.

  Conventionally, an apparatus using an electrochemical measurement method (hereinafter referred to as an electrochemical measurement apparatus) stores an electrolyte solution obtained by dissolving a measurement sample and an electrolyte in a solvent in a measurement cell, and acts on the electrolyte solution. By immersing the electrode, a voltage is applied to the electrolyte solution (current is supplied).

  In recent years, conductive diamond electrodes have been used as working electrodes. The diamond electrode is formed by forming a conductive diamond film on a conductive silicon (Si) substrate.

  When this conductive diamond electrode is used in an electrochemical measurement device, when a conductive diamond film is immersed in an electrolyte solution, a silicon substrate or the like is always immersed in the electrolyte solution. Must be waterproofed.

  As this waterproofing method, a method of waterproofing by resin molding a silicon substrate or the like as shown in Patent Document 1, a method of waterproofing by embedding in a glass rod, or a method of waterproofing using a mechanical sheet is considered. It is done.

  However, it is difficult to mold only a silicon substrate, and it is necessary to mold it with a diamond film to some extent, but the diamond surface cannot be molded sufficiently due to its poor adhesiveness. There is a drawback that you can not.

  In addition, regarding waterproofing by embedding in a glass rod, it is difficult to embed this in a glass rod because of the flat plate structure in which a conductive diamond film is formed on a silicon substrate. In addition, the silicon substrate is destroyed by thermal stress due to the heat of the glass rod, resulting in a gap between the glass rod and the silicon substrate, and the electrolyte solution enters the glass rod and cannot be waterproofed. Also occurs.

  Furthermore, in the case of waterproofing using a mechanical sheet, there is a problem that the additive elutes from the housing or sealing resin used for the mechanical seal, adversely affecting the measurement result, and the size of the working electrode is enlarged. There is a problem. Although waterproofing using super engineering plastics or fluorine-based rubber is also conceivable, super engineering plastics have a very high cost, and there is a problem that the rubber O-ring deteriorates faster than the conductive diamond electrode.

  Furthermore, in order to perform waterproofing effectively in order to avoid short circuit using these waterproofing processing methods, the area of the working electrode itself and its peripheral part becomes large, and this makes it difficult to reduce the amount of sample to be measured Met.

As described above, any of the waterproofing methods described above cannot completely waterproof the silicon substrate or the like, and as a result, there is a problem that the measurement result and the convenience of the measurement operation are adversely affected.
JP 2001-147 211 A

  Therefore, the present invention has been made to solve the above problems all at once, and has been made based on a completely new idea, which is different from the conventional idea of immersing the working electrode in an electrolyte solution, and the working electrode is waterproofed. The main intended task is to eliminate the need for

That working electrode according to the present invention is a working electrode for applying a voltage to the electrolyte solution, before the substrate is formed in the substrate, has, a housing recess for housing the electrolyte solution, A conductive diamond film is formed on the surface of the housing recess. Here, the electrolyte solution refers to a solution in which the electrolyte is ionized, and includes a solution obtained by dissolving the sample and the electrolyte in a solvent. Further, applying a voltage to the electrolyte solution includes passing a current through the electrolyte.

  In such a case, since the electrolyte solution is accommodated only in the accommodating recess covered with the conductive diamond film, and the electrolyte solution contacts only the conductive diamond film, the silicon substrate to be waterproofed is the electrolyte. There is no contact with the solution, and as a result, the working electrode need not be waterproofed.

  In order to prevent the measurement sample from being unevenly distributed in the housing recess and to keep the measurement temperature constant, heating means for causing convection in the electrolyte solution in the housing recess by heating the conductive diamond film is provided. It is desirable to have it.

The electrochemical measurement apparatus according to the present invention is an electrochemical measurement apparatus for analyzing the electrolyte solution by immersing and applying at least a working electrode and a reference electrode to the electrolyte solution, wherein the working electrode is The substrate is formed on the substrate and has an accommodating recess for accommodating the electrolyte solution, and a conductive diamond film is formed on the surface of the accommodating recess.

  If this is the case, the electrolyte solution is accommodated in the accommodation recess covered with the conductive diamond film, and the electrolyte solution contacts only the conductive diamond film. As a result, the working electrode need not be waterproofed.

  In addition, in order to obtain a flow cell type electrochemical measurement apparatus using the working electrode of the present invention, an introduction port for introducing the electrolyte solution into the housing recess, and a lead-out port for deriving the electrolyte solution from the housing recess It is preferable that a flow path for flowing the electrolyte solution is formed by joining the working electrode and the lid portion together.

  And it is preferable to provide the said cover part with the counter electrode which makes a pair with the said reference electrode and the said working electrode, and aim at the simplification of the arrangement | positioning of a reference electrode and a counter electrode, and the facilitation of an assembly.

  As described above, according to the present invention, the electrolyte solution is accommodated in the accommodation recess covered with the conductive diamond film, and the electrolyte solution contacts only the conductive diamond film. There is no contact with the solution, and as a result, the working electrode need not be waterproofed. Therefore, various problems related to waterproofing can be solved.

  <First Embodiment>

  Next, an embodiment of the electrochemical measurement apparatus 1 according to the first embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the electrochemical measurement apparatus 1 according to the present embodiment analyzes the measurement sample by applying a voltage to an electrolyte solution L obtained by dissolving the measurement sample and the electrolyte in a solvent. A batch-type electrochemical measurement apparatus that performs voltammetry measurement using an electrode system, the basic configuration of which is a potentiometer that controls the working electrode 2, the reference electrode 3, the counter electrode 4, and the reference voltage 3 of the working electrode 2. The Ostat 5 and the information processing device 6 that calculates the concentration of the measurement sample based on the current and voltage obtained by the potentiostat 5 are used.

  In this embodiment, potassium chloride (KCl) is used as the electrolyte, the solvent is pure water, and the electrolyte solution is a KCl solution of about 0.1 mol / liter.

  As shown in FIG. 1, the working electrode 2 includes a silicon substrate 21 that is a conductive substrate, and a conductive diamond film 22 formed on the silicon substrate. The working electrode 2 has a housing recess 23 for housing the electrolyte solution L, and the housing recess 23 is formed by the conductive diamond film 22. The conductive diamond film 22 is connected to the lead wire 10 connected to the potentiostat 5 by a wiring member 24. The wiring member 24 is made of, for example, an epoxy-based conductive paint and needs to be waterproofed in the same manner as the silicon substrate 21. In the present embodiment, the opening edge of the housing recess 23 is provided so as not to contact the electrolyte solution L. Since it is in contact with the nearby conductive diamond film 22, it does not come into contact with the electrolyte solution L. Further, the conductive diamond film 22 is heated on the back surface of the silicon substrate 21 where the accommodation recess 23 is not formed, thereby causing convection in the electrolyte solution L in the accommodation recess 23 and stirring the measurement sample. A thermistor 25 is provided. The thermistor 25 heats the electrolyte solution L in the housing recess 23 to about 40 ° C. (a temperature about 20 ° C. higher than the environmental temperature (for example, room temperature 25 ° C.)). The thermistor 25 is controlled by normal feedback control. That is, a set value (temperature) is sent from the information processing apparatus 6 to the drive circuit 11, and the drive circuit 11 heats the thermistor 25 by flowing current through the thermistor 25 based on the set value (temperature). The resistance of the thermistor 25 is calculated, the temperature of the thermistor 25 is obtained from the temperature-resistance characteristic table specific to the thermistor 25, and is fed back to the current value.

  The specific shape of the working electrode 2 is a square shape as shown in the front view of the working electrode 2 in FIG. 2, and the lateral width of the silicon substrate 21 is 20.5 ± 0.5 mm. The width of the range in which the film 22 is formed, that is, the lateral width of the housing recess 23 is 6.8 ± 0.05 mm. As shown in the cross-sectional view of FIG. 3, the thickness of the conductive diamond electrode 2 (silicon substrate 21) is 450 ± 25 μm, and the depth of the accommodating recess 23 is 250 ± 12 μm.

  In the method for producing the diamond electrode 2, first, a square silicon substrate 21 is etched using a potassium hydroxide (KOH) solution to form a housing recess 23. By this etching, the gradient of the side wall surface 231 of the housing recess 23 with respect to the horizontal is approximately 55 degrees. Then, a diamond film 22 is formed in the accommodating recess 23 using a plasma CVD method. At this time, in order to make the diamond film 22 conductive, boron is doped as an impurity.

  The reference electrode 3 is an electrode serving as a reference for the potential of the working electrode 2. In this embodiment, for example, a silver / silver chloride electrode (Ag / AgCl electrode) is used, and the diameter thereof is about 2 mm. And it fixes by the holding member which is not illustrated so that it may be immersed in the electrolyte solution L accommodated in the accommodation recessed part 23. FIG.

  The counter electrode 4 is configured to allow a current in the working electrode 2 to flow without trouble when a potential at the working electrode 2 is set, and is connected to the working electrode 2 in series. In this embodiment, a platinum (Pt) electrode is used, and its diameter is about 0.1 mm. Similarly to the reference electrode 3, the counter electrode 4 is also fixed by a holding member (not shown) so as to be immersed in the electrolyte solution L accommodated in the accommodating recess 23.

  The potentiostat 5 is controlled by an information processing device 6 to be described later, receives voltage signals from the working electrode 2, the reference electrode 3, and the counter electrode 4, and controls the electrodes 2, 3, and 4. And the voltage applied between the working electrode 2 and the counter electrode 4 is always adjusted, and the voltage with respect to the reference electrode 3 of the working electrode 2 is controlled.

  The information processing device 6 controls the potentiostat 5, obtains a current-voltage curve based on the voltage signal and the current signal from the potentiostat 5, and calculates the concentration of the measurement sample based on the current-voltage curve. To do. Further, a setting signal indicating a set value (temperature) is output to the drive circuit 11 that drives the thermistor 25.

  According to the electrochemical measuring apparatus 1 of the present embodiment configured as described above, the electrolyte solution L is accommodated in the accommodating recess 23 covered with the conductive diamond film 22, and the electrolyte solution L is only in the conductive diamond film 22. Since the contact is made, the silicon substrate 21 to be waterproofed does not come into contact with the electrolyte solution L, and as a result, the working electrode 2 need not be waterproofed. Therefore, various problems related to waterproofing can be solved.

  Moreover, since the heating means 25 which causes the electrolyte solution L in the accommodation recessed part 23 to convect by heating the conductive diamond film 22 is provided, the measurement sample is prevented from being stirred and unevenly distributed in the accommodation recessed part 23. Can do.

  Second Embodiment

  Next, an embodiment of the electrochemical measurement apparatus 1 according to the second embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the thing corresponding to the said 1st Embodiment.

  The electrochemical measurement apparatus 1 according to the second embodiment is different from the first embodiment. As shown in FIG. 4, an electrolyte solution L obtained by dissolving a measurement sample and an electrolyte in a solvent is circulated in the flow cell 7. And an electrochemical measurement device that performs a voltammetric measurement by a three-electrode method for analyzing a measurement sample by applying a voltage to the electrolyte solution L in the flow cell 7. The basic configuration includes a working electrode 2 constituting the flow cell 7, a reference electrode 3 and a counter electrode 4 provided in the flow cell 7, a potentiostat 5 for controlling the voltages of the electrodes 2, 3, and 4, and a potentiostat. 5 is the information processing device 6 that calculates the concentration of the measurement sample based on the current and voltage obtained by 5.

  The flow cell 7 is configured by joining the working electrode 2 and the lid 71 with a joining member 72. And it connects with the introductory pipe | tube 8 which introduce | transduces the electrolyte solution L, and the derivation | leading-out pipe | tube 9 which derives | leads-out, and forms the flow path through which the electrolyte solution L is distribute | circulated. The electrolyte solution L is circulated through this flow path by a pump (not shown). In order to prevent liquid leakage, a waterproof gasket 73 is sandwiched between the working electrode 2 and the lid 71.

  The working electrode 2 is manufactured by the same method as in the first embodiment, and has a housing recess 23 that is generally rhombus in plan view, as shown in FIG. Specifically, it includes guide grooves 232 provided continuously at the apexes of the longer diagonal of the rhombus. An angle formed by two side wall surfaces 231 that are continuously adjacent to one guide groove 232 is less than about 30 degrees. Thereby, the electrolyte solution L flowing from the one guide groove 232 can pass through the flow cell 7 in a laminar flow without becoming a turbulent flow, and a remaining liquid of the electrolyte solution L can be prevented.

  The lid 71 includes an introduction port 711 for introducing the electrolyte solution L into the housing recess 23 and a lead-out port 712 for leading the electrolyte solution L from the housing recess 23. The working electrode 2 and the lid 71 are connected to the lid 71. The inlet port 711 or the outlet port 712 is opened above the guide groove 232 when bonded. And the counter electrode 4 is arrange | positioned at the introduction port 711 and the derivation | leading-out port 712, respectively. As shown in the schematic configuration diagram of FIG. 4 and the partially enlarged view of FIG. 5, the counter electrode is driven into the lid portion 71 so as not to hinder the flow of the electrolyte solution L, and is led out as the introduction pipe 8. 9, and the counter electrode 4 is fitted so that the inner diameter of the counter electrode 4 substantially matches the inner diameter of the introduction port 711, the inner diameter of the outlet port 712, the inner diameter of the inlet pipe 8, and the inner diameter of the outlet pipe 9. Further, in order to dispose the reference electrode 3 at a substantially central portion of the housing recess 23, the reference electrode 3 is fitted into a through hole 713 provided at a substantially central portion of the lid portion 71, and the tip portion of the reference electrode 3 is a lid It protrudes from the portion 71.

  As in the first embodiment, the reference electrode 3 is a silver / silver chloride electrode (Ag / AgCl electrode), and the counter electrode 4 is a platinum (Pt) electrode.

  According to the electrochemical measuring apparatus 1 of the present embodiment configured as described above, even the electrochemical measuring apparatus 1 using the flow cell 7 does not have a structure in which the working electrode 2 is immersed in the flow cell 7, but conductive diamond. Since only the membrane 22 is in contact with the electrolyte solution L, the silicon substrate 21 to be waterproofed does not come into contact with the electrolyte solution L, and as a result, the working electrode 2 need not be waterproofed. Therefore, various problems related to waterproofing can be solved.

  Since the reference electrode 3 and the counter electrode 4 that forms a pair with the working electrode 2 are provided on the lid 71, the arrangement of the reference electrode 3 and the counter electrode 4 can be simplified and the assembly can be facilitated. .

  <Third Embodiment>

  Next, an embodiment of the electrochemical measurement apparatus 1 according to the third embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the thing corresponding to the said each embodiment.

  As shown in FIG. 7, the electrochemical measurement apparatus according to the third embodiment has two electrodes for analyzing the measurement sample by passing a current through an electrolyte solution L obtained by dissolving the measurement sample and the electrolyte in a solvent. A batch-type electrochemical measurement device that performs constant current measurement by a method, the basic configuration of which is a working electrode 2, a counter electrode 4, a galvanostat 12 that controls the current flowing through the working electrode 2 and the counter electrode 4, The information processing apparatus 6 calculates the concentration of the measurement sample based on the current and voltage obtained by the galvanostat 12.

  The galvanostat 12 is controlled by the information processing device 6 and receives a voltage signal and a current signal from the working electrode 2 and the counter electrode 4, and controls the current flowing through the electrodes 2, 4 to control the working electrode. 2 and the current flowing through the counter electrode 4 are kept constant.

  The information processing device 6 controls the galvanostat 12, obtains a current-voltage curve based on the voltage signal and the current signal from the galvanostat 12, and calculates the concentration of the measurement sample based on the current-voltage curve. It is.

  According to the electrochemical measuring apparatus 1 of the present embodiment configured as described above, the electrolyte solution L is accommodated in the accommodating recess 23 covered with the conductive diamond film 22, and the electrolyte solution L is only in the conductive diamond film 22. Since the contact is made, the silicon substrate 21 to be waterproofed does not come into contact with the electrolyte solution L, and as a result, the working electrode 2 need not be waterproofed. Therefore, various problems related to waterproofing can be solved.

  The present invention is not limited to the above embodiment.

  For example, in the above-described embodiment, the gradient with respect to the horizontal of the side wall surface of the accommodating recess is set to about 55 degrees by etching with the KOH solution, but the present invention is not limited to this. For example, as shown in FIG. For example, as shown in FIG. 9, the slope of the side wall surface with respect to the horizontal may be a right angle.

  Further, the counter electrode and the reference electrode are not limited to the platinum (Pt) electrode or the silver / silver chloride (Ag / AgCl) electrode, and a common electrode may be used.

  Furthermore, the electrolyte solution is not limited to an aqueous solution. The electrolyte is not limited to liquid but may be gel or the like, and the electrolyte is not limited to KCl but may be NaCl or the like.

  In addition to the first and third embodiments, the working electrode of the present invention is a variety of devices using an electrochemical measurement method, such as an electro titration device, a polarograph, an electrolytic analysis device, a coulometric analysis device, and an electrode-type concentration measurement device. It can also be used.

  It can also be used as an apparatus for measuring whole blood using, for example, an enzyme electrode method, or an electrode used for refining such as copper.

  In addition, a part or all of the above-described embodiments and modified embodiments may be combined as appropriate, and the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit thereof. Needless to say.

1 is a schematic configuration diagram of a batch type electrochemical measurement device according to a first embodiment of the present invention. The top view of the working electrode in the embodiment. Sectional drawing of the working electrode in the embodiment. The schematic block diagram of the flow cell type electrochemical measuring apparatus which concerns on 2nd Embodiment of this invention. The partial expanded sectional view of the introduction port in the embodiment. The top view of the working electrode in the embodiment. The schematic block diagram of the batch type electrochemical measuring apparatus which concerns on 3rd Embodiment of this invention. Sectional drawing of the working electrode in other deformation | transformation embodiment. Furthermore, sectional drawing of the working electrode in other deformation | transformation embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrochemical measuring device L ... Electrolyte solution 2 ... Working electrode 22 ... Conductive diamond film 23 ... Containing recessed part 231 ... Side wall surface 25 ... Heating means (thermistor)
3 ... Reference electrode 4 ... Counter electrode 71 ... Lid 711 ... Introduction port 712 ... Derivation port

Claims (5)

A working electrode for applying a voltage to the electrolyte solution,
Substrate and are formed on the substrate, wherein the electrolyte solution has a housing recess for housing a working electrode conductive diamond film on the surface of the housing recess is formed.   The working electrode according to claim 1, further comprising a heating unit that heats the conductive diamond film to cause convection in the electrolyte solution in the housing recess. An electrochemical measurement device that analyzes the electrolyte solution by immersing and applying at least a working electrode and a reference electrode to the electrolyte solution,
An electrochemical measurement apparatus, wherein the working electrode is formed on a substrate and the substrate, has an accommodating recess for accommodating the electrolyte solution, and a conductive diamond film is formed on a surface of the accommodating recess. A lid provided with an introduction port for introducing the electrolyte solution into the accommodation recess and a lead-out port for extracting the electrolyte solution from the accommodation recess;
The electrochemical measurement apparatus according to claim 3, wherein a flow cell for circulating the electrolyte solution is configured by joining the working electrode and the lid. The electrochemical measurement device according to claim 4, wherein a counter electrode that forms a pair with the reference electrode and the working electrode is provided on the lid.