JP5331830B2 - Electrode for electrochemical measurement and electrochemical analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an electrochemical analyzer having a working electrode less varied in an electrode surface state. <P>SOLUTION: A working electrode 2, a counter electrode 3 and a reference electrode 4 are disposed in an electrolytic cell 1. The working electrode has a layered structure of a valve metal and platinum, a cross-sectional crystal structure along a thickness direction in a platinum portion is formed in the shape of layers on an electrode surface, and each layer of the platinum portion has a thickness of 5 micrometers or less. The electrodes 2, 3 and 4 are connected to potential applying means 5 and measuring means 6 through lead wires 7. A solution dispensing mechanism 11 introduces a measurement solution including a target chemical component from a measurement solution vessel 8 into a solution introducing tube 13 and introduces a buffer solution from a buffer vessel 9 into the solution introducing tube 13. The measurement solution and the buffer solution thus introduced are injected by a solution injecting mechanism 12 into the electrolytic cell 1 for electrochemical measurement of the target component. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to an electrode for electrochemical measurement and an electrochemical analyzer for electrochemically analyzing a trace amount of chemical components contained in a liquid sample such as blood and urine.

  Electrochemical measurement enables high-sensitivity measurement with a relatively simple apparatus configuration, and is frequently used in the field of analytical chemistry. Electrochemical measurement methods include potentiometry, amperometry, voltammetry, impedance measurement, and the like, and a method of detecting photons by combining these with other detection means such as an optical element.

  In general, platinum group metals, especially platinum, are frequently used for electrodes used for electrochemical measurements because of their excellent chemical stability. In recent years, platinum has been used as an electrode incorporated in a flow cell in the analysis of chemical components contained in liquid samples such as blood and urine.

  For example, as described in Patent Document 1, when chemical components in blood and urine are continuously measured, a process of applying a plurality of potentials between the working electrode and the counter electrode for each analysis is performed, including washing and main measurement. Through this, repeated measurement is possible.

  As an electrode material containing platinum, Patent Document 2 describes using a platinum group metal for a counter electrode and a working electrode. Patent Document 3 discloses an electrode for electrochemical reaction in which a valve metal such as titanium, tantalum, or zirconium and platinum are combined by hot pressing and a method for manufacturing the electrode.

  Furthermore, in Patent Document 4, titanium, niobium are used as an insoluble electrode used for an electrode for electrolyzing salt water to produce strongly acidic water having a bactericidal action, and for electrolytic cleaning treatment of organic matter-containing wastewater. An electrode in which a platinum alloy coating layer, iridium oxide and / or a platinum oxide coating layer are sequentially formed on a tantalum substrate is disclosed.

JP-A-6-222037 Japanese Patent Laid-Open No. 10-288592 JP-A-2-66188 JP 2001-262388 A

  When a platinum group metal, particularly platinum, is used as an electrode, it exhibits very excellent characteristics in the analysis of several tens to several hundreds of times that is experimentally performed.

  However, in the analysis system shown in Patent Document 1, for example, in the analysis of chemical components contained in a liquid sample such as blood and urine, when a sample containing a large amount of protein or halogen element is repeatedly measured over a long period of time Alternatively, when a sample containing a strong alkali component such as potassium hydroxide is brought into contact with the electrode surface as a cleaning agent for cleaning the electrode surface, and the voltage is repeatedly applied for a long time, the electrode surface is gradually eroded. As a result, there is a problem that the surface state of the electrode fluctuates and adversely affects the measurement result.

  As is well known, platinum is an expensive metal, and as shown in Patent Documents 2 and 3, a composite electrode of platinum group metal, platinum and titanium metal, etc. is known.

  However, in the above composite electrode, there is no example in which the crystal structure and orientation of the platinum layer are controlled.

  As a result of intensive studies by the inventors of the present application, the surface state of the electrode, particularly the crystal orientation, is analyzed in the case where an extremely small concentration of a chemical component contained in a liquid sample such as blood and urine is measured multiple times using the same electrode. It has been found that sex affects analytical data.

    The purpose of the present invention is to reduce the amount of platinum, have sufficient mechanical strength, and have little fluctuation in the electrode surface state, and an electrode for electrochemical measurement, and using the electrode, the data is stable and appropriate over a long period of time. It is to realize an electrochemical analysis apparatus capable of performing various analytical measurements.

In order to achieve the above object, the present invention is configured as follows.

  The electrode for electrochemical measurement according to the present invention is formed by stacking a valve metal of any one of Ti, Ta, Nb, Zr, Hf, V, Mo, and W and platinum, and a sectional crystal in the plate thickness direction of the platinum part. The tissue is layered with respect to the electrode surface.

  The electrochemical analysis apparatus of the present invention includes an electrolytic cell in which a working electrode, a counter electrode, and a reference electrode are disposed, a solution injection mechanism for injecting a measurement solution and a buffer solution in the electrolytic cell, a working electrode, and a counter electrode. A potential applying means for applying a potential to the reference electrode; and a working electrode, a counter electrode, and a measuring means connected to the reference electrode for measuring the electrochemical characteristics of the measurement solution, wherein the working electrode comprises Ti, Ta, Nb, A valve metal of any one of Zr, Hf, V, Mo, and W and platinum are laminated, and the cross-sectional crystal structure in the plate thickness direction of the platinum portion is formed in layers in parallel to the electrode surface.

  In addition, the method for producing an electrode for electrochemical measurement used in the electrochemical analysis apparatus of the present invention is a method of cooling any valve metal and platinum of Ti, Ta, Nb, Zr, Hf, V, Mo, and W. By laminating into a plate shape by hot rolling, a cross-sectional crystal structure in the plate thickness direction of the platinum is formed in a layer shape with respect to the electrode surface, and a laminated electrode in which the thickness of each layer of the platinum is 5 micrometers or less is formed. The formed laminated electrode is mirror-polished and the surface altered layer of the laminated electrode is removed electrochemically.

  Furthermore, the electrochemical measuring electrode manufacturing apparatus used in the electrochemical analysis apparatus of the present invention pressurizes platinum in a nitrogen atmosphere, heats it, and hot-rolls it to produce a platinum plate having a predetermined thickness. A platinum plate rolling section, a platinum plate cold rolling section for cold rolling a platinum plate, and a platinum plate and a titanium plate processed in the platinum plate cold rolling section are placed in a vacuum, and the titanium plate surface is Surface etching film removal part that removes the surface oxide layer by dry etching, a platinum plate and a titanium plate are laminated, and cold rolled so that the thickness of the platinum plate becomes a predetermined thickness in a vacuum atmosphere, A cross-sectional crystal structure in the plate thickness direction of the platinum is formed in a layered manner with respect to the electrode surface, and a laminated electrode forming portion for forming a laminated electrode of platinum and titanium having a thickness of each platinum layer of 5 micrometers or less; Cutting that cuts the laminated electrode to a specified size Insulating with an adhesive so that only the platinum surface of the laminated electrode connected to the lead wire is exposed in a predetermined area, and an electrode forming portion for electrically connecting the platinum surface of the cut laminated electrode and the lead wire A resin-embedded portion embedded in a conductive resin, a mechanical polishing portion that mechanically polishes the platinum surface of the embedded laminated electrode, and a mechanically polished laminated electrode at a predetermined potential and a predetermined potential scanning speed in an electrolyte. And an electropolishing unit that repeats scanning.

  According to the present invention, the amount of platinum is reduced, the electrode has a sufficient mechanical strength, and has little fluctuation in the electrode surface state, and the data is stable and appropriate over a long period of time using the electrode. An electrochemical analyzer capable of performing analytical measurement, an electrochemical measurement electrode manufacturing method, and an electrochemical measurement electrode manufacturing apparatus can be realized.

It is a whole block diagram of the electrochemical analyzer by Example 1 of this invention. It is a schematic block diagram of the electrode manufacturing apparatus for electrochemical measurements by Example 1 of this invention. It is a figure which shows the X-ray-diffraction analysis result of the electrode of Example 1 and a comparative example of this invention. It is a figure which shows the crystal structure analysis result of the plate | board thickness direction cross section of the electrode by Example 1 of this invention. It is a figure explaining the effect of the platinum electrode based on Example 1 of this invention. It is a cyclic voltammogram of the electrode of Example 2 and a comparative example of the present invention. It is a whole block diagram of the electrochemical analyzer by Example 3 of this invention. It is a decomposition | disassembly block diagram of the flow cell used for the electrochemical analyzer by Example 3 of this invention. It is a figure which shows the crystal structure analysis result of the plate | board thickness direction cross section of the electrode of the comparative example different from this invention. It is a table | surface which shows the priority orientation rate of the platinum part, analysis object, and fluctuation range of Examples 1-11 of this invention and Comparative Examples 1-9. It is a decomposition | disassembly block diagram in the other example of the flow cell used for the electrochemical analyzer of the Example of this invention. It is a decomposition | disassembly block diagram in the further another example of the flow cell used for the electrochemical analyzer of the Example of this invention. It is a decomposition | disassembly block diagram in the further another example of the flow cell used for the electrochemical analyzer of the Example of this invention. It is a decomposition | disassembly block diagram in the further another example of the flow cell used for the electrochemical analyzer of the Example of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  Prior to the description of the embodiments of the present invention, the principle of the present invention will be described.

  In the analysis of chemical components contained in liquid samples such as blood and urine, the present inventors have conducted various analyzes on the cause of fluctuations in the measurement results when repeatedly measuring over a long period of time. As a result, it was found that it was mainly caused by the change in the electrode surface state accompanying the repeated analysis.

  That is, the process of applying a potential in a liquid sample containing protein, the process of applying a potential in a liquid containing a strong alkali component such as potassium hydroxide as a cleaning agent for cleaning the electrode surface, both of which were repeated for a long time. In this case, the electrode surface is gradually etched, and the surface state after repeated analysis varies with respect to that at the beginning of analysis. As a result, the measurement result is adversely affected.

  As a result of examining the etching behavior of the platinum surface, it was found that the etching rate varies depending on the crystal orientation of the surface, so that a level difference occurs in the structural unit having different crystal orientation. When the crystal layer observed in the cross-sectional observation of platinum in the plate thickness direction exceeds 5 μm, as the analysis is repeated, that is, with the progress of etching, the unevenness of the electrode surface becomes obvious and the electrode surface area changes.

  In particular, when the working electrode is installed in the flow cell, if the unevenness of the electrode surface is large, it will not be possible to secure a stable liquid flow, and sufficient replacement of the analysis liquid and cleaning liquid will not be possible, making it impossible to perform proper analysis. .

  When the crystal layer is made small, large fluctuations in the electrode surface area can be suppressed. Therefore, in order to stabilize the analysis data over a long period of time, it is effective to etch uniformly in the thickness direction, and the thickness of the platinum crystal layer is 5 μm or less, preferably 3 μm or less, more preferably 1 μm or less. It is effective to do.

  That is, in the electrode for electrochemical measurement used in the electrochemical analyzer for measuring the electrochemical response of the chemical component contained in the liquid sample, among Ti, Ta, Nb, Zr, Hf, V, Mo, W One of the valve metals and platinum are laminated, and the cross-sectional crystal structure in the plate thickness direction of the platinum portion is formed in a layered manner with respect to the electrode surface, and the thickness of each layer of the platinum portion is 5 μm or less.

  However, if the crystal grains are too small, the material becomes hard and the workability is impaired, so the thickness of each layer is preferably 0.01 μm or more. In this specification, the “layered crystal structure” is a state in which each crystal structure is stretched in the electrode plane direction, that is, a state in which the crystal structure is stretched in the rolling direction, and in the electrode plate thickness direction. Refers to the compressed state. Further, the individual layers do not mean that they are composed of a single crystal structure, but are substantially composed of a plurality of different stretched crystal structures. “Crystal layer thickness” refers to the length in the plate thickness direction of the individual crystals of the platinum portion seen when the cross section in the plate thickness direction of the laminated electrode of platinum and valve metal is observed.

  Each crystal refers to a structure surrounded by a small-angle grain boundary having a grain boundary angle of less than 2 degrees. The crystal structure image can be observed by an electron beam backscattering pattern method or the like.

  For the above reasons, in order to improve the stability of the analytical data, it is effective to control not only the thickness of the platinum crystal layer but also the crystal orientation on the electrode surface. The preferred plane orientation is not particularly limited, but an electrode in which any one of the (111) plane, (200) plane, (220) plane, or (311) plane is preferentially oriented in X-ray diffraction of the platinum surface is preferable. Platinum in which the predetermined plane orientation occupies 80% or more of the peak integral value is preferable. The crystal orientation rate on the electrode surface is defined by the following formula (1).

(Orientation ratio of crystal orientation) = I (hkl) / Si [I (hkl)] × 100 (1)
However, I (hkl) is the integrated value of diffraction intensity of each surface obtained from the X-ray diffraction measurement of the electrode surface, and Si [I (hkl)] is the total sum of integrated values of diffraction intensity of (hkl). . In this specification, the preferred orientation according to the above formula (1) from the respective diffraction intensity integrated values of the (111) plane, (200) plane, (220) plane, or (311) plane obtained by X-ray diffraction measurement. Calculate gender. More preferably, platinum having a preferentially oriented (220) orientation obtained by combining hot rolling, annealing, and cold rolling can be used. In order to make the thickness of the platinum layer 5 μm or less, cold rolling at a temperature below the recrystallization temperature of platinum is carried out under conditions of a reduction rate of 70% or more, preferably 90% or more. The rolling reduction is defined by the following equation (2).

(Rolling ratio) = (t ₀ −t) / t ₀ × 100 (2)
However, in the above (2), t ₀ is the thickness before rolling, t is the thickness after rolling.

  For joining with valve metals such as titanium, the surface of titanium reacts with oxygen, carbon, nitrogen, etc. to form an inactive film, so that the metal surface of titanium is exposed and quickly joined with platinum. There is a need. For this purpose, for example, after the inert film formed on the titanium surface is removed by dry etching or the like in a vacuum atmosphere, bonding is possible by bonding with a platinum plate and forging at or below the recrystallization temperature of platinum. .

  It is also possible to cold-roll after titanium and platinum are joined by a known explosive pressure welding method. Alternatively, the cold-rolled platinum foil and the titanium plate may be joined by an explosion pressure welding method.

  Furthermore, it is also possible to produce a cold-rolled platinum foil and a titanium surface plated with platinum by bringing the platinum surfaces together and forging at a recrystallization temperature or lower. When platinum plating is performed on the titanium surface, the titanium surface may be treated by a sandblasting method or a chemical etching method as a pretreatment for improving adhesion. In the chemical etching method, hydrofluoric acid, fluoride-containing hydrofluoric acid, concentrated sulfuric acid, hydrochloric acid, oxalic acid, or a mixed solution thereof can be used.

  Further, an electrode in which the valve metal is plated with platinum can also be used. For controlling the crystal grain size and orientation, platinum plating is possible by controlling the current density in a plating solution containing an organic substance as an additive. Furthermore, after plating, the thickness and crystal orientation of the platinum crystal layer can be adjusted by rolling at a recrystallization temperature or lower.

  Although the plate | board thickness of the valve metal which is a base electrode of a laminated electrode is not specifically limited, From viewpoint of workability, such as a bending and cutting, 10-5000 micrometers is preferable. The thickness of the platinum portion of the laminated electrode is preferably 10 to 150 μm. More preferably, the thickness of the platinum part of a laminated electrode is 20-100 micrometers.

  In the rolling process, a layer having random crystal orientation may be formed on the surface layer or a coarse crystal structure may be formed due to heat concentration, and the depth may reach about 10 μm from the surface layer in some cases. Therefore, the thickness of the platinum part is preferably more than 10 μm. When the thickness is 150 μm or more, sufficient mechanical strength can be secured with no problem in handling the electrode alone, but the amount of platinum increases and the cost increases. By setting the thickness of the platinum portion to 100 μm, the amount of platinum can be reduced and the cost can be reduced, and since it has a laminated electrode structure, it has sufficient mechanical strength with no handling problems.

  It is preferable to mechanically polish the surface of the platinum electrode after producing a laminated electrode by integrating platinum and the valve metal. Furthermore, it is more preferable to electropolish the mechanically polished electrode. For the electropolishing, a method in which a potential is repeatedly applied between the hydrogen generation region and the oxygen generation region in an electrolytic solution containing a strong alkali component such as acid or potassium hydroxide is preferable. The applied potential waveform may be a triangular wave, a rectangular wave, or the like, but is not particularly limited in the present invention.

  The above mechanical polishing and electrolytic polishing are particularly effective treatments for a laminated electrode of platinum and a valve metal produced by rolling or an explosive pressure welding method. In other words, the crystal orientation in the vicinity of the surface of the electrode that has undergone hot rolling is relatively random, or the grain size and orientation at the inside of the plate and the surface layer due to local heat applied to the surface. Was found to be different. In the electrode after mechanical polishing, the deteriorated surface layer formed by rolling is removed to some extent, but the influence of pressurization during mechanical polishing and scratches due to abrasive grains still exist.

  Also in the manufacturing method of the present invention, although the inside of platinum is in a state having crystal orientation by cold rolling, it is conceivable that a surface deteriorated layer having disordered crystal orientation is formed in the vicinity of the surface. Electropolishing is effective in removing the surface-affected layer, and can be said to be a step of exposing a platinum portion having high crystal orientation inside the electrode.

  In the electrode manufacturing process, in order to determine the degree of removal of the altered layer on the platinum surface, the above-mentioned electrode is immersed in a predetermined electrolyte during the electropolishing process, and the surface state is diagnosed by cyclic voltammetry. Is preferred. That is, a plurality of hydrogen adsorption / desorption current peaks are obtained from the cyclic voltammetry results. Since these current peaks are current amounts depending on the surface orientation of the electrode surface, they can be used as a reference for determining the degree of removal of the surface altered layer caused by rolling and mirror finishing.

  Of the obtained peaks, the area of at least two peaks and the area ratio are calculated. Based on the calculation result, an electrode from which the surface-modified layer has been removed can be obtained by electropolishing until a predetermined area ratio is obtained.

  Examples of the electrolytic solution used in cyclic voltammetry include sulfuric acid, phosphoric acid, hydrochloric acid, perchloric acid, sodium hydroxide, potassium hydroxide, and aqueous ammonia.

  It has been found that an analytical apparatus using the above-described electrode as a working electrode shows stable measurement results with little fluctuation in its electrochemical response over a long period of time. Even when the working electrode is installed in the flow cell, the fluctuation of the surface area of the electrode is small over a long period of time, and the fluctuation of the surface unevenness is small, so that the liquid replacement of the analysis solution and the cleaning solution can be performed stably. As a result, data stability can be improved.

  In addition, in an electrochemical analyzer including a flow cell, when an electrode manufactured in a manufacturing process including rolling is used as a working electrode, the angle of the rolling direction of the electrode with respect to the flow direction of the liquid sample is 45 to 135 degrees. It is preferable to arrange. For example, when analyzing the electrochemical response of a chemical component adsorbed on a magnetic bead or the like as an analysis target substance, if the rolling direction is the same as the flow direction, the bead is likely to flow from the top of the working electrode, and the data is It tends to fluctuate. When the rolling direction is less than 45 degrees and exceeds 135 degrees with respect to the flow direction, the above-described influence is manifested. If the electrodes are arranged so that the rolling direction is at an angle of 45 to 135 degrees with respect to the flow direction, the step formed between the crystal structures is a slight step, for example, a magnetic having a diameter of sub-μm to several μm. It was found that beads and the like are likely to stay on the surface of the working electrode, resulting in improved data stability.

  For example, the following components can be analyzed as chemical components contained in a liquid sample such as blood and urine using the electrode and the electrochemical measurement apparatus of the present invention.

  That is, for example, glucose, glycated hemoglobin, glycated albumin, lactic acid, uric acid, urea, creatinine, bile acid, cholesterol, neutral fat, ammonia, urea nitrogen, bilirubin, histamine and the like can be mentioned. However, there is no particular limitation as long as it is a component that exhibits an electrochemical response of a redox species generated by the action of an enzyme, mediator, or the like.

  In the case of detecting glucose, for example, the glucose concentration can be quantified by reducing or oxidizing hydrogen peroxide generated by the action of glucose oxidase on the electrode.

  In the case of detecting glycated proteins such as glycated hemoglobin and glycated albumin, for example, after releasing the glycated peptide from the glycated protein by protease, hydrogen peroxide generated by further action of glycated peptide oxidase on the electrode By reducing or oxidizing, the glycated protein concentration can be quantified.

  In the case of detecting lactic acid, for example, the concentration of lactic acid can be quantified by reducing or oxidizing hydrogen peroxide generated by the action of lactate oxidase on the electrode.

  In the case of detecting uric acid, the concentration of uric acid can be quantified by, for example, reducing or oxidizing hydrogen peroxide generated by the action of uricase on the electrode.

  In the case of detecting urea, for example, it was produced by further acting glutamate dehydrogenase on ammonia produced by acting urease in the presence of β-nicotinamide adenine dinucleotide (NADH) and potassium ferricyanide. The urea concentration can be quantified by oxidizing potassium ferrocyanide on the electrode.

  In the case of detecting creatinine, for example, creatinine concentration can be quantified by reducing or oxidizing hydrogen peroxide generated by sequentially acting creatininase, creatinase and sarcosine oxidase on the electrode. .

  In the case of detecting bile acids, for example, by oxidizing potassium ferrocyanide produced by sequentially acting bile acid sulfate sulfatase, β-hydroxysteroid dehydrogenase in the presence of reduced NADH and potassium ferricyanide on the electrode, The bile acid concentration can be quantified.

  In the case of detecting cholesterol, for example, the cholesterol concentration can be quantified by reducing or oxidizing hydrogen peroxide generated by the action of cholesterol oxidase on the electrode.

  In the case of detecting neutral fat, the concentration of neutral fat can be quantified by reducing or oxidizing, for example, hydrogen peroxide generated by the action of glycerophosphate oxidase on the electrode.

  In the case of detecting a fatty acid, the fatty acid concentration can be quantified by, for example, reducing or oxidizing hydrogen peroxide generated by the action of acyl CoA oxidase on the electrode.

  In the case of detecting ammonia, the ammonia concentration can be quantified by oxidizing potassium ferrocyanide produced by the action of glutamate dehydrogenase in the presence of NADH and potassium ferricyanide on the electrode.

  In the case of detecting bilirubin, for example, the concentration of urea nitrogen can be determined by oxidizing potassium ferrocyanide produced by the action of bilirubin oxidase in the presence of potassium ferricyanide on the electrode.

  The enzymes described above are immobilized on the electrode surface. The method for immobilizing the enzyme on the electrode surface is not particularly limited. For example, a method of immersing the electrode in an aqueous solution or buffer solution in which the enzyme is dissolved, or an aqueous solution or buffer solution in which the enzyme is dissolved on the electrode is used. There is a method of physically or chemically immobilizing enzymes by dropping. In addition, there is a method in which an electrode is immersed in a solution containing a thiol into which a functional group such as a carboxyl group or an amino group is introduced as a terminal group, and the thiol is adsorbed on the electrode surface and then immobilized by reacting with an enzyme or the like. . Furthermore, a method of immobilizing an enzyme or the like on the electrode using a cross-linking reagent such as glutaraldehyde or further bovine serum albumin, an enzyme or the like in the membrane after forming a gel film such as a hydrophilic polymer on the electrode Or a method of immobilizing an enzyme or the like in the film after a conductive polymer film such as polythiophene is formed on the electrode.

  When detecting an analysis target, it is effective to use a mediator molecule for the purpose of extending the detection concentration range, if necessary. When using a mediator molecule, it is preferable to dispose the mediator molecule on the electrode in the immobilized membrane of the physiologically active substance of enzymes formed on the electrode or separately from it. The kind of the mediator molecule is not particularly limited, but for example, at least one kind such as potassium ferricyanide, potassium ferrocyanide, ferrocene and derivatives thereof, viologens and methylene blue can be used.

  Next, an embodiment of the present invention based on the above principle will be described.

  Hereinafter, the overall configuration of an electrochemical analyzer according to an embodiment of the present invention will be described.

  FIG. 1 is a diagram showing an overall configuration of an electrochemical analyzer according to Embodiment 1 of the present invention. The first embodiment of the present invention is an electrochemical analyzer having a batch processing system.

  In FIG. 1, a working electrode 2, a counter electrode 3 and a reference electrode 4 are arranged in an electrolytic cell 1. Each electrode 2, 3, 4 is connected to potential applying means 5 and measuring means 6 by a lead wire 7. The counter electrode 3 was obtained by rolling platinum into a plate shape and mirror-polishing the surface. The reference electrode 4 was an Ag | AgCl electrode. In this specification, a silver | silver chloride (saturated potassium chloride aqueous solution) electrode is referred to as Ag | AgCl.

  The solution dispensing mechanism 11 introduces the measurement solution containing the chemical component to be measured from the measurement solution container 8 and the buffer solution from the buffer solution container 9 into the solution introduction tube 13, respectively. The introduced measurement solution and buffer solution are mixed in the solution introduction tube 13, and the mixed solution is injected into the electrolytic cell 1 by the solution injection mechanism 12 to perform electrochemical measurement of the object to be measured. .

  The potential applying means 5 may be a potentiostat, a galvanostat, a DC power supply, an AC power supply, or a system in which they are connected to a function generator or the like. The measuring means 6 measures the electrochemical characteristics of the object to be measured. The electrochemical characteristics may be any known measurement technique such as potentiometry, amperometry, voltammetry, impedance measurement, etc., and are not particularly limited. There is also a method of detecting photons generated in response to an electrochemical reaction with an optical element.

  The measurement solution for which the measurement has been completed is sucked by the solution discharge mechanism 15 and discarded into the waste liquid container 16 through the solution discharge pipe 14. After the measurement of the sample, the cleaning liquid is sucked from the cleaning liquid container 10 by the solution dispensing mechanism 11 and supplied into the electrolytic cell 1 by the solution injection mechanism 12. The cleaning liquid that has cleaned the inside of the electrolytic cell 1 is discarded in the waste liquid container 16.

  Here, as a typical example, the voltage application means 5 outputs a pulse-shaped waveform potential that repeats a positive potential and a negative potential with a predetermined period with respect to the working electrode during measurement of the measurement solution. This pulse-like waveform potential is applied when a measurement solution containing a large amount of protein and halogen elements such as blood is continuously flowed into the electrolytic cell for a long period of time, or when a strong alkaline detergent such as potassium hydroxide is used in the measurement container. It is configured so that it is applied when it flows into the. In the first embodiment, the above-described potential application waveform is used. However, the present invention is not particularly limited to this.

  Here, the working electrode 2 was produced according to the following procedure by the working electrode manufacturing apparatus 50 shown in FIG.

  In FIG. 2, platinum is pressed at 30 MPa in a nitrogen atmosphere by the platinum plate processing section 50a. In the platinum plate processing section 50a, the platinum plate is heated at 800 ° C. for 1 hour and hot-rolled at 100 MPa to produce a platinum plate having a thickness of 5 mm. Subsequently, in the platinum plate cold rolling section 50b, the platinum plate processed in the rolling processing section 50a is cold rolled at 100 MPa to produce a platinum plate having a thickness of 1 mm. Thereafter, in the surface oxide film removing unit 50c, the platinum plate processed in the platinum plate cold rolling unit 50b and the titanium plate having a thickness of 0.5 mm are introduced into the vacuum chamber, and the titanium plate surface is dry-etched. Thus, the surface oxide layer is removed. Thereafter, the laminated electrode forming portion 50d quickly laminates the platinum plate and the titanium plate, and cold-rolled so that the film thickness of the platinum plate becomes 100 μm at 450 degrees in a vacuum atmosphere. A laminated electrode of platinum and titanium having a layered crystal structure of 5 μm or less is obtained.

  Next, the laminated electrode produced by the laminated electrode forming portion 50d is cut into a size of 5 mm × 15 mm at the cutting portion 50e. Thereafter, the cut laminated electrode is bent 90 degrees at the electrode-forming portion 50f, and the platinum surface and the conductive wire are connected by solder.

  Next, in the resin embedding part 50g, it is embedded in the fluororesin using an adhesive so that only the platinum surface of the laminated electrode is exposed in an area of 5 mm × 10 mm.

  Subsequently, in the mechanical polishing unit 50h, the platinum surface is sequentially mechanically polished using water-resistant polishing paper, diamond paste, and alumina particles to finish a mirror surface.

  Finally, in the electropolishing unit 50i, in the 0.2 mol / L potassium hydroxide aqueous solution, the potential scanning is performed 10,000 times at a potential scanning speed of 0.1 V / s between potentials of −1.2 V to 1.0 V vs Ag | AgCl. Repeatedly, the working electrode 2 is obtained.

  X-ray diffraction measurement of the electrode surface of the working electrode 2 used in Example 1 was performed. Using Cu Kα as the X-ray source, the output was 40 kV and 20 mA, and three different points on the platinum surface were measured. The integration value (I) of diffraction peaks of the (111) plane, (200) plane, (220) plane, and (311) plane on the platinum surface is calculated, and the orientation ratio ((%) = I (h kl) ) / ΣI (hkl) × 100). When calculating each peak integral value, the (111) plane is 37 ° ≦ 2θ ≦ 42 °, the (200) plane is 44 ° ≦ 2θ ≦ 4 °, and the (220) plane is 65 ° ≦ 2θ ≦ 70. The (311) plane was performed in the range of 78 ° ≦ 2θ ≦ 83 ° (θ is the diffraction angle). As a result of the measurement, it was found that the plane index (220) was preferentially oriented as in the result of Example 1 shown in FIG. 3, and the orientation rate was 97%.

  A cross section in the thickness direction of the laminated electrode produced in the same manner was exposed, and the platinum portion was analyzed by an electron beam backscattering pattern. The analysis results are shown in FIG.

  As shown in FIG. 4A, it was found that the obtained working electrode had a layered crystal structure with respect to the electrode surface. In order to calculate the thickness of the platinum crystal layer, an area of 25 μm × 25 μm was measured with three visual fields at intervals of 0.075 μm, and the thickness of the layer having the maximum layer thickness among the measured surfaces was measured.

  FIG. 4B shows a typical crystal structure image near the surface of the main electrode. It was found that the layer thickness was 5 μm or less at the maximum.

  FIG. 5 is a diagram for explaining the effect of the platinum electrode employed in Example 1 of the present invention. Note that the data shown in FIG. 5 is data obtained as a result of repeated measurement using the same concentration of TSH (thyroid stimulating hormone) as an analysis target. The horizontal axis in FIG. 5 indicates the number of tests, and the vertical axis indicates a value obtained by dividing each measured value by the reference value. Further, the reference value is an output value when a TSH-containing solution having a predetermined concentration is measured, and the actual measurement value is a measured value when each of the solutions used in Examples and Comparative Examples is measured. The fluctuation range is defined as the difference between the values of the 60000th analysis and the 1st analysis.

  In FIG. 5, the line connecting the circle marks is the case of Example 1 of the present invention, and the line connecting the triangle marks is the case of a comparative example different from the present invention.

  1, the chemical component contained in a liquid sample such as serum and urine, for example, TSH in the serum, is immunologically analyzed as a measurement solution, and the washing solution is used as, for example, potassium hydroxide. Measurement was performed by introducing an aqueous solution into the electrolytic cell at the end of each measurement.

  As shown in FIG. 5, the fluctuation range when the electrode of the comparative example was used was 10.3%. The electrode of the comparative example is a laminated electrode of platinum and titanium that has been subjected to hot rolling and recrystallization treatment, and the platinum surface is an electrode that has been subjected to mirror polishing treatment and electrolytic treatment in the same manner as in Example 1. Details will be described in a comparative example described later. On the other hand, when the platinum electrode of Example 1 of the present invention was used, the fluctuation range was reduced to 4.4%.

  The electrode of Example 1 of the present invention is a laminated electrode in which the cross-sectional crystal structure in the plate thickness direction of the platinum portion is formed in a layer shape with respect to the electrode surface, and the thickness of the layer is 5 μm or less. In the electrode according to Example 1 of the present invention, the surface deteriorated layer with disordered crystal orientation generated in rolling and mechanical polishing was removed, and the surface orientation (220) was preferentially oriented at an orientation ratio of 90% or more. Yes. In the electrochemical measuring apparatus using the electrode according to Example 1 of the present invention as a working electrode, the difference in etching rate in the electrode surface is small, so that the unevenness caused by etching is small and the fluctuation of the surface area can be suppressed. As a result, the electrochemical response has little fluctuation over a long period of time, and an effect that a stable measurement result can be obtained was recognized.

  Next, a second embodiment of the present invention will be described. In the electrode of Example 2 and the electrochemical analysis apparatus using the electrode, the electrode was immersed in a predetermined electrolyte during the electrolytic polishing process, and the surface state was determined by cyclic voltammetry. While diagnosing, the same as Example 1 except that the altered layer on the platinum surface was removed.

  Cyclic voltammetry uses a phosphate buffer solution with pH 6.86 substituted with nitrogen as the electrolyte, the working electrode is Pt wire, the reference electrode is Ag | AgCl, and the potential scanning range is -0.6 to 1.1 V, scanning It implemented on the conditions of speed | rate 0.1V / s. The measurement results are shown in FIG.

  Among a plurality of hydrogen adsorption / desorption current peaks obtained from the cyclic voltammetry results, a peak at −0.37 to −0.31 V is defined as a, and the peak is −0.31 to −0.2 V. The peak is b, and the peak area and the area ratio b / a are calculated. Electrolytic treatment was performed until the area ratio became 80% or less, and working electrode 2 was obtained.

  As a result of repeated analysis in the same manner as in Example 1 by an electrochemical analyzer using a working electrode according to Example 2 of the present invention, a favorable result was obtained with a fluctuation range of 4.2%. As a result of X-ray diffraction analysis of an electrode different from that of the present invention produced in the same manner, it was found that the orientation was preferentially oriented in the (220) direction with an orientation rate of 98%. Also in the electron beam backscattering pattern analysis, the thickness of the crystal structure layer of the platinum plate thick section was 5 μm or less. In the analyzer using the electrode according to Example 2 of the present invention as a working electrode, the etching rate difference in the electrode surface is small, so that the unevenness caused by the etching is small, and the variation in the surface area can be suppressed. It was confirmed that the electrochemical response had little fluctuation over a long period of time and a stable measurement result was obtained.

  In Example 2 of the present invention, peaks a and b were used as criteria for determining the degree of surface alteration layer removal, but b / c was calculated from peak c and peak b found at -0.48 to -0.37 V. It was confirmed that the same effect was obtained even when b / c was set to 35% or less as a criterion.

  Next, an electrochemical analyzer according to Example 3 of the present invention will be described with reference to FIGS. FIG. 7 is a schematic configuration diagram of an electrochemical analyzer according to Embodiment 3 of the present invention. FIG. 8 is an exploded configuration diagram of a flow cell used in the electrochemical analyzer shown in FIG.

  In FIG. 7, the example shown in FIG. 1 and the example shown in FIG. 7 are equivalent except that the electrolytic cell 1 shown in FIG.

  In FIG. 8, a flow cell 20 as an electrolysis cell has two electrically insulating substrates 30 and 32 shown in FIG. 8A and a seal member 31 laminated as shown in FIG. 8B. It is formed. The insulating substrate 30 is made of polyetheretherketone. The insulating substrate 30 is not particularly limited as long as it is an insulating resin excellent in chemical resistance. Fluorine resin, polystyrene, polyethylene, polypropylene, polyester, polyvinyl chloride, epoxy resin, polyimide, polyamideimide, polysulfone , Polyethersulfone, poniphenylene sulfide, acrylic resin, and the like can be used.

  A working electrode 34 is fixed to one surface of the insulating substrate 30 (surface facing the electrically insulating substrate 32). A method for manufacturing the working electrode 34 will be described below.

  That is, the steps up to mechanical polishing of Example 1 of the present invention were carried out to obtain a laminated electrode of platinum and titanium. After this laminated electrode is embedded in a recess provided on the surface of the insulating substrate 30 and fixed with an adhesive, the machine is sequentially machined with water-resistant abrasive paper, diamond paste, and alumina until there is no surface step between the insulating substrate 30 and the laminated electrode. Polished to a mirror surface. In addition, as an adhesive, thermoplastic, thermosetting or photo-curing resins such as epoxy and acrylic can be used, but as long as the resin is excellent in chemical resistance like the insulating resin, It does not specifically limit and can be selected suitably. Thereafter, application of a rectangular pulsed potential of −1.2 V / 0.5 seconds and 3.0 V / 1.5 seconds in a 0.2 mol / L potassium hydroxide aqueous solution was repeated 10,000 times. In Example 3 of the present invention, the working electrode 4 is arranged so as to be perpendicular to the rolling direction and the direction in which the liquid flows during analysis.

  The insulating substrate 32 is made of a transparent acrylic material. A counter electrode 35 is fixed to one surface of the insulating substrate 32 (the surface facing the electrically insulating substrate 30). As the counter electrode 35, platinum was processed into an electrode shape and then subjected to an annealing treatment at 1000 ° C. for one hour.

  A concave portion is formed on the surface of the electrically insulating substrate 32, and a counter electrode 35 subjected to annealing treatment is embedded in the concave portion and fixed with an adhesive, and then the surface of the counter electrode 35 is mirror-polished. The shape of the counter electrode 35 is not limited to a plate shape, and may be a comb shape, a mesh shape, or a rod shape. Further, the electrode material is not limited to platinum but may be other platinum group metals. Similarly to the working electrode 34, the counter electrode 35 may use platinum that has been subjected to electrolytic polishing after mirror polishing.

  The working electrode 34 and the counter electrode 35 are connected to the lead wires 39 and 40 by soldering before being embedded in the insulating substrates 30 and 32, respectively. The lead wires 39 and 40 are opened on the insulating substrates 30 and 32. Through the hole.

  The seal member 31 is made of a fluorine-based resin and has an opening 36 at the center. The insulating substrate 30 is formed with holes 21 and 22 for connecting to the pipes 37 and 38 with the working electrode 34 therebetween, and these two holes 21 and 22 are located on the inner periphery of the opening 36. The solution can be taken in and out of the opening 36. The working electrode 34 and the counter electrode 35 face each other through the opening 36 of the seal member 31.

  Screw holes 33 are formed at the four corners of the insulating substrates 30 and 32 and the sealing member 31, and screws are passed through each of the insulating substrates 30 and 32, and the insulating substrate 30, the sealing member 31, and the insulating substrate 32 are fixed and crimped. A flow cell 20 is formed.

  In the insulating substrate 30, fluororesin pipes 37 and 38 are fixedly connected to the surface opposite to the surface on which the working electrode 34 is disposed. As will be described later, one of the pipes 37 and 38 is connected to a mechanism for introducing a measurement solution or the like into the flow cell 20, and the other is used as a flow path for discharging the measured solution. A reference electrode (not shown in FIG. 8) is disposed in the pipe 38, that is, the solution discharge side pipe section, and is used as a reference electrode when a potential is applied to the working electrode.

  In addition, the flow cell of this invention is not specifically limited to the Example shown in FIG. 8, Other structures are possible. Hereinafter, examples of flow cells having other configurations will be described.

  FIG. 11 is a diagram illustrating another example of the flow cell. 11, the flow cell 60 is formed by laminating each member shown in FIG. 11A, that is, two electrically insulating substrates 70 and 72, and a seal member 71 as shown in FIG. 11B. The A working electrode 74 is fixed to one surface of the insulating substrate 70 (surface facing the electrically insulating substrate 72). A counter electrode 75 is fixed to one surface of the insulating substrate 72 (the surface on the side facing the electrically insulating substrate 70).

  The working electrode 74 and the counter electrode 75 are connected to the lead wires 79 and 80 by soldering before being embedded in the insulating substrates 70 and 72, respectively. The lead wires 79 and 80 are opened on the insulating substrates 70 and 72. Through the hole.

  An opening 76 is formed in the center of the seal member 71. Holes 21 and 22 for connecting to the pipes 77 and 78 are formed in the insulating substrate 72 with the counter electrode 75 interposed therebetween, and these two holes 21 and 22 are arranged so as to be located inside the opening 76. The solution can be taken in and out of the opening 76 portion. The working electrode 74 and the counter electrode 75 are opposed to each other through the opening 76 of the seal member 71.

  Screw holes 73 are formed in the four corners of the insulating substrates 70 and 72 and the seal member 71, and a screw is passed through each of the insulating substrates 70, 72, and the insulating substrate 70, the seal member 71, and the insulating substrate 72 are fixed and pressure-bonded. 60 is formed.

  In the insulating substrate 72, pipings 77 and 78 made of fluororesin are fixedly connected to the surface opposite to the surface on which the counter electrode 75 is disposed. As will be described later, one of the pipes 77 and 78 is connected to a mechanism for introducing a measurement solution or the like into the flow cell 60, and the other is used as a flow path for discharging the measured solution.

  The reference electrode (not shown in FIG. 11) is disposed in the pipe 78, that is, the solution discharge side pipe section, and is used as a reference electrode when a potential is applied to the working electrode.

  FIG. 12 is a diagram illustrating another example of the flow cell. In FIG. 12, a flow cell 90 is formed by laminating each member shown in FIG. 12A, that is, two electrically insulating substrates 100 and 102, and a seal member 101 as shown in FIG. 12B. The A working electrode 104 is fixed to one surface of the insulating substrate 100 (surface facing the electrically insulating substrate 102). A counter electrode 105 is fixed to one surface of the insulating substrate 102 (the surface facing the electrically insulating substrate 100).

  The working electrode 104 and the counter electrode 105 are connected to the lead wires 109 and 110 by soldering before being embedded in the insulating substrates 100 and 102, respectively. The lead wires 109 and 110 are opened on the insulating substrates 100 and 102. Through the hole.

  An opening 106 is formed in the center of the seal member 101. The shape of the opening 106 is hexagonal in the example shown in FIG. 12, but is not particularly limited as long as the liquid replacement is smoothly performed without stagnation of various solutions supplied in the flow cell.

  The insulating substrate 100 is formed with holes 21 and 22 for connecting to the pipes 107 and 108 with the working electrode 104 interposed therebetween, and these two holes 21 and 22 are located inside the opening 106. And the solution can be taken in and out of the opening 106. The working electrode 104 and the counter electrode 105 are opposed to each other through the opening 106 of the seal member 101.

  Screw holes 103 are formed in the four corners of the insulating substrates 100 and 102 and the seal member 101, and a screw is passed through each of the insulating substrates 100 and 102, and the insulating substrate 100, the seal member 101, and the insulating substrate 102 are fixed and pressure-bonded to each other. 90 is formed.

  In the insulating substrate 102, fluororesin pipes 107 and 108 are fixedly connected to the side surfaces. As will be described later, one of the pipes 107 and 108 is connected to a mechanism for introducing a measurement solution or the like into the flow cell 90, and the other is used as a flow path for discharging the measured solution.

  A reference electrode (not shown in FIG. 12) is arranged in the pipe 108, that is, the solution discharge side pipe section, and is used as a reference electrode when a potential is applied to the working electrode.

  FIG. 13 is a diagram illustrating another example of the flow cell. In FIG. 13, the flow cell 120 is formed by laminating each member shown in FIG. 13A, that is, two electrically insulating substrates 130 and 132, and a seal member 131 as shown in FIG. 13B. The A counter electrode 135 is fixed to one surface of the insulating substrate 132 (the surface facing the electrically insulating substrate 130). As shown in FIG. 13C, a concave portion in which the working electrode 134 is disposed and a thread groove 143 of the energizing bolt 141 that enables connection to the working electrode 134 are formed in the central portion of the insulating substrate 130. .

  After the working electrode 134 is fixed to the insulating substrate 130 with an adhesive, mirror polishing is performed. Thereafter, the energizing bolt 141 is tightened into the thread groove 143 through the energizing plate 142. The energization plate 142 is not particularly limited as long as it is a soft metal having a low resistivity, such as gold, tin, or aluminum. The energizing bolt 141 is connected to the REIT wire 139 and enables electrical connection to the working electrode 134.

  The counter electrode 135 is connected to the lead wire 140 by soldering before being embedded in the insulating substrate 132, and the lead wire 140 is passed through a hole formed in the insulating substrate 132.

  An opening 136 is formed at the center of the seal member 131. Holes 21 and 22 for connecting to the pipes 137 and 138 are formed in the insulating substrate 132 with the counter electrode 135 therebetween, and these two holes 21 and 22 are arranged so as to be located inside the opening 136. The solution can be taken in and out of the opening 136. The working electrode 134 and the counter electrode 135 are opposed to each other through the opening 136 of the seal member 131.

  Screws 133 are formed at the four corners of the insulating substrates 130 and 132 and the sealing member 131, and the screws are passed through them, and the insulating substrate 130, the sealing member 131, and the insulating substrate 132 are fixedly crimped to each other, and the flow cell 120. Form.

  In the insulating substrate 132, fluororesin pipes 137 and 138 are fixedly connected to the side surface of the surface on which the counter electrode 135 is disposed. As will be described later, one of the pipes 137 and 138 is connected to a mechanism for introducing a measurement solution or the like into the flow cell 120, and the other is used as a flow path for discharging the measured solution. The reference electrode (not shown in FIG. 13) is arranged in the pipe 138, that is, the solution discharge side pipe section, and is used as a reference electrode when a potential is applied to the working electrode 134.

  FIG. 14 is a diagram illustrating another example of the flow cell. In FIG. 14, the flow cell 180 is formed by laminating a working electrode 194 with insulating substrates 190 and 192 through an O-ring 191. A plurality of screw holes 193 are formed on the outer peripheries of the insulating substrates 190 and 192. By tightening the screws through the screw holes 193, the insulating substrates 190 and 192 are fixed to each other to form the flow cell 180.

  A counter electrode 195 is embedded in the central portion of the insulating substrate 192, and the counter electrode 195 protrudes inside the flow cell 180. Also, fluororesin pipes 197 and 198 are fixedly connected to the insulating substrate 192. As will be described later, one of the pipes 197 and 198 is connected to a mechanism for introducing a measurement solution or the like into the flow cell 180, and the other is used as a flow path for discharging the measured solution. A reference electrode (not shown in FIG. 14) is disposed in the pipe 198, that is, the solution discharge side pipe section, and is used as a reference electrode when applying a potential to the working electrode.

  The working electrode 194 and the counter electrode 195 are connected to the lead wires 199 and 200 by soldering.

  Next, with reference to FIG. 7, the whole structure of the electrochemical analyzer of Example 3 of this invention is demonstrated. Since the same components as those in FIG. 1 are duplicated, a detailed description thereof will be omitted.

  In FIG. 7, the measurement solution in the measurement solution container 8 and the buffer solution in the buffer solution container 9 are sucked by the solution dispensing mechanism 11, mixed in the solution introduction tube 13, and injected into the flow cell 20. . While the liquid mixture is stored in the flow cell 20, a predetermined potential is applied to the working electrodes (34, 74, 104, 134, 194) in the flow cell 20 by the voltage application means 5, and the electric power of the object to be measured is measured. Chemical measurements are taken. The signal obtained by the electrochemical reaction at the working electrode (34, 74, 104, 134, 194) in the flow cell 20 is transmitted to the measuring means 6 for signal processing via the lead wire 7.

  In addition, it is also possible to optically measure a change caused by an electrochemical reaction by disposing a detector on the transparent insulating resin substrate 32.

  The measurement solution that has been measured in the flow cell 20 is sucked by the solution discharge mechanism 15 and discarded through the solution discharge pipe 14 into the waste liquid container 16.

  As a result of X-ray diffraction measurement of the electrode surface of the working electrode (34, 74, 104, 134, 194) used in Example 3, the plane index (220) was preferentially oriented, and the orientation ratio 92 %. Further, from the electron beam backscattering pattern analysis, the working electrode (34, 74, 104, 134, 194) has a layered crystal structure with respect to the electrode surface, and the platinum layer thickness is 5 μm or less at the maximum. I found out.

  Using the electrochemical analyzer shown in FIG. 7, a complex in which a chemical component contained in a liquid sample such as serum or urine, for example, TSH in serum, is adsorbed on the surface of a magnetic bead having a diameter of 3 μm as a measurement solution. The measurement was performed by introducing, for example, an aqueous potassium hydroxide solution into the electrolytic cell as a cleaning solution at the end of each measurement.

  As in Example 1, the fluctuation range between the first analysis and the 60,000th analysis was 5.1%. In the analyzer using the electrode according to Example 3 of the present invention as a working electrode, the difference in etching rate in the electrode surface is small, so that the unevenness caused by the etching is small, and the fluctuation of the surface area can be suppressed. In addition, it was possible to stably perform the liquid replacement of the analysis solution and the cleaning solution, and the effect that the electrochemical response was less varied over a long period of time and a stable measurement result was obtained was confirmed.

  In addition, by placing the working electrode in a direction perpendicular to the flow direction of the analysis liquid, the working electrode is restrained from flowing out of the working electrode to the downstream, and the fluctuation is stable and stable over a long period of time. The effect that a measurement result was obtained was recognized.

  In Example 3, the working electrodes (34, 74, 104, 134, 194) are arranged so that the rolling direction is perpendicular to the direction in which the liquid during analysis flows, but the rolling direction is the flow direction. On the other hand, as a result of examination even in the case of the same direction, the fluctuation range was 7%, and the fluctuation range was slightly increased as compared with Example 3. In addition, as a result of evaluating the data stability in a short period, the variation in data was larger than that of the present example. This is considered to be the effect that the magnetic beads slightly flowed downstream from the working electrode surface during the analysis.

  Therefore, as shown in the third embodiment, it is preferable that the working electrode 34 be arranged so that the rolling direction is perpendicular to the direction in which the liquid at the time of analysis flows in order to improve data stability. all right.

  Next, a fourth embodiment of the present invention will be described. In Example 4, an enzyme is immobilized on the electrode surface of Example 1, and the base metal is Nb. Other configurations are the same as those in the first embodiment. In Example 4, glucose of a known concentration was used as an analysis target, and measurement was repeated as in Example 1.

  As a result of the measurement, as shown in FIG. 10, when the fluctuation range between the first analysis and the 60000th analysis is obtained, it is 4.1%, which is smaller than that in Comparative Example 2 in which glucose is analyzed. I found out. This is because, in the analyzer using the electrode according to Example 4 of the present invention as a working electrode, the etching rate difference in the electrode surface is small, so that the unevenness caused by the etching is small and the fluctuation of the surface area can be suppressed. As a result, the amount of enzyme that modifies the electrode surface can be stably controlled. In addition, according to Example 4 of the present invention, it is possible to stably perform the liquid replacement of the analysis solution and the cleaning solution, and the electrochemical response has little fluctuation over a long period of time, and a stable measurement result can be obtained. Was recognized.

  The comparative example shown in FIG. 10 will be described later.

  Next, a fifth embodiment of the present invention will be described. In Example 5, analysis was repeatedly performed according to the measurement method of Example 1 except that urea of a known concentration was used as an analysis target. That is, in the measurement solution container 8, potassium ferrocyanide was generated by further causing glutamate dehydrogenase to act in the presence of the specimen sample and urease, then β-nicotinamide adenine dinucleotide (NADH), and potassium ferricyanide.

  The measurement solution containing potassium ferrocyanide from the measurement solution container 8 and the buffer solution from the buffer solution container 9 are introduced into the solution introduction tube 13 and mixed, and injected into the electrolytic cell 1 by the solution injection mechanism 12. Electrochemical measurements were taken. As a result of the repeated measurement, as shown in FIG. 10, when the fluctuation range between the first analysis and the 60000th analysis is obtained, it is 2.8%, which is a fluctuation range compared to Comparative Example 3 in which the analysis target is the same. I found it getting smaller.

  This is because an analyzer using the present electrode as a working electrode has a small etching rate difference in the electrode surface, so that unevenness caused by etching is small, and variation in surface area can be suppressed.

  In addition, according to Example 5 of the present invention, it is possible to stably perform the liquid replacement of the analysis solution and the cleaning solution, and the electrochemical response has little fluctuation over a long period of time, and a stable measurement result can be obtained. Was recognized.

  Next, a sixth embodiment of the present invention will be described. In Example 6, the base metal is Zr. Other configurations are the same as those in the first embodiment. In Example 6, a known concentration of cholesterol was used as an analysis target, and repeated analysis measurement was performed according to the measurement method of Example 1.

  That is, hydrogen peroxide was generated by allowing the sample sample and cholesterol oxidase to act in the measurement solution container 8 of FIG. Then, the measurement solution containing hydrogen peroxide from the measurement solution container 8 and the buffer solution from the buffer solution container 9 are introduced into the solution introduction tube 13 and mixed, and injected into the electrolytic cell 1 by the solution injection mechanism 12. Then, electrochemical measurement was performed.

  As a result of the repeated measurement, as shown in FIG. 10, when the fluctuation range between the first analysis and 60000 times is obtained, it is 5.8%, which is a fluctuation range compared to Comparative Example 4 in which the analysis target is the same. I found it getting smaller. This is because an analyzer using this electrode as a working electrode has a small etching rate difference on the surface of the electrode, so that unevenness caused by etching is small, and variation in surface area can be suppressed.

  In addition, according to Example 6 of the present invention, it is possible to stably perform the liquid replacement of the analysis solution and the cleaning solution, and the electrochemical response has little fluctuation over a long period of time, and a stable measurement result can be obtained. Was recognized.

  Next, a seventh embodiment of the present invention will be described. In Example 7, analysis was repeatedly performed according to the measurement method of Example 1 except that uric acid having a known concentration was used as an analysis target.

  That is, in the measurement solution container 8, hydrogen peroxide was generated by allowing the sample sample and uricase to act. The measurement solution containing hydrogen peroxide from the measurement solution container 8 and the buffer solution from the buffer solution container 9 are introduced and mixed in the solution introduction tube 13 and injected into the electrolytic cell 1 by the solution injection mechanism 12. Then, electrochemical measurement was performed.

  As a result of repeated measurement, as shown in FIG. 10, when the fluctuation range between the first analysis and the 60000th analysis is obtained, it is 6.5%, and the fluctuation range is larger than that of Comparative Example 5 in which the analysis target is the same. I found it getting smaller. This is because an analyzer using this electrode as a working electrode has a small etching rate difference on the surface of the electrode, so that unevenness caused by etching is small, and variation in surface area can be suppressed.

  Further, according to Example 7 of the present invention, it is possible to stably perform the liquid replacement of the analysis solution and the cleaning solution, and the electrochemical response has little fluctuation over a long period of time, and a stable measurement result can be obtained. Was recognized.

  Next, an eighth embodiment of the present invention will be described. In Example 8, repeated analysis measurement was performed according to the measurement method of Example 1, except that a known concentration of creatinine was used as an analysis target.

  That is, in the measurement solution container 8, hydrogen peroxide was generated by sequentially causing the specimen sample, creatininase, and sarcosine oxidase to act. The measurement solution containing hydrogen peroxide from the measurement solution container 8 and the buffer solution from the buffer solution container 9 are introduced and mixed in the solution introduction tube 13 and injected into the electrolytic cell 1 by the solution injection mechanism 12. Electrochemical measurements were taken.

  As a result of the repeated measurement, as shown in FIG. 10, when the fluctuation range between the first analysis and the 60000th analysis is obtained, it is 7.9%, which is a fluctuation range compared to Comparative Example 6 in which the analysis target is the same. I found it getting smaller. This is because an analyzer using this electrode as a working electrode has a small etching rate difference on the surface of the electrode, so that unevenness caused by etching is small, and variation in surface area can be suppressed.

  In addition, according to Example 8 of the present invention, it is possible to stably perform the liquid replacement of the analysis solution and the cleaning solution, and the electrochemical response has little fluctuation over a long period of time, and a stable measurement result can be obtained. Was recognized.

  Next, a ninth embodiment of the present invention will be described. In Example 9, repeated analysis measurement was performed according to the measurement method of Example 1, except that a known concentration of creatinine was used as an analysis target.

  That is, in the measurement solution container 8, potassium ferrocyanide was generated by sequentially causing a specimen sample, bile acid sulfate sulfatase, and β-hydroxysteroid dehydrogenase to act in the presence of reduced NADH and potassium ferricyanide.

  The measurement solution containing potassium ferrocyanide from the measurement solution container 8 and the buffer solution from the buffer solution container 9 are introduced into the solution introduction tube 13 and mixed, and injected into the electrolytic cell 1 by the solution injection mechanism 12. Electrochemical measurements were taken.

  As a result of repeated measurement, as shown in FIG. 10, when the fluctuation range between the first analysis and the 60000th analysis is obtained, it is 9.8%, which is a fluctuation range compared to Comparative Example 7 in which the analysis target is the same. I found it getting smaller. This is because an analyzer using this electrode as a working electrode has a small etching rate difference in the surface of the electrode, so that unevenness caused by etching is small, and variation in surface area can be suppressed.

  Further, according to Example 9, it is possible to stably perform the liquid replacement of the analysis liquid and the cleaning liquid, and the effect that the electrochemical response is less fluctuated over a long period of time and a stable measurement result can be obtained. It was.

  Next, Example 10 of the present invention will be described. In Example 10, repeated analysis measurement was performed according to the measurement method of Example 1 except that a fatty acid having a known concentration was used as an analysis target.

  That is, in the measurement solution container 8, hydrogen peroxide was generated by allowing the sample sample and acyl CoA oxidase to act. The measurement solution containing hydrogen peroxide from the measurement solution container 8 and the buffer solution from the buffer solution container 9 are introduced into the solution introduction tube 13 and mixed, and injected into the electrolytic cell 1 by the solution injection mechanism 12. Electrochemical measurements were taken.

  As a result of the repeated measurement, as shown in FIG. 10, when the fluctuation range between the first analysis and the 60000th analysis is obtained, it is 5.9%, and the fluctuation range is larger than that of Comparative Example 8 where the analysis target is the same. I found it getting smaller.

  This is because an analyzer using this electrode as a working electrode has a small etching rate difference on the surface of the electrode, so that unevenness caused by etching is small, and variation in surface area can be suppressed.

  In addition, according to Example 10, it is possible to stably perform the liquid replacement of the analysis solution and the cleaning solution, and the effect that the electrochemical response is less fluctuated over a long period of time and a stable measurement result can be obtained. It was.

  Next, Example 11 of the present invention will be described. In Example 11, repeated analysis measurement was performed in accordance with the measurement method of Example 1 except that bilirubin having a known concentration was used as an analysis target.

  That is, potassium ferrocyanide was produced in the measurement solution container 8 by allowing bilirubin oxidase to act in the presence of the specimen sample and potassium ferricyanide. The measurement solution containing potassium ferrocyanide from the measurement solution container 8 and the buffer solution from the buffer solution container 9 are introduced into the solution introduction tube 13 and mixed, and injected into the electrolytic cell 1 by the solution injection mechanism 12. Electrochemical measurements were taken.

  As a result of the repeated measurement, as shown in FIG. 10, when the fluctuation range between the first analysis and the 60000th analysis is obtained, it is 4.3%, and the fluctuation range is larger than that of the comparative example 9 in which the analysis target is the same. I found it getting smaller.

  This is because an analyzer using this electrode as a working electrode has a small etching rate difference on the surface of the electrode, so that unevenness caused by etching is small, and variation in surface area can be suppressed.

  Further, according to Example 11, it is possible to stably perform the liquid replacement of the analysis liquid and the cleaning liquid, and the effect that the electrochemical response is less fluctuated over a long period of time and a stable measurement result can be obtained. It was.

Next, Comparative Examples 1 to 9 described in FIG. 10 will be described.
(Comparative Example 1)
The electrode of Comparative Example 1 is a laminated electrode of platinum and titanium. For this electrode, a platinum plate having a thickness of 1 mm and a titanium plate having a thickness of 0.5 mm were pressed at 30 MPa in a vacuum atmosphere. While heating at 800 ° C. for 1 hour, hot rolling was performed at 100 MPa so that the thickness of the platinum portion was 100 μm. After cooling, as in Example 1 of the present invention, it was embedded in a fluorine-based resin, the platinum surface was sequentially mechanically polished with water-resistant abrasive paper, diamond paste, and alumina, followed by electrolytic polishing to obtain a working electrode.

  Using this working electrode, as in Example 1, it was used in the electrochemical analyzer of FIG. 1 to immunologically analyze TSH in serum as a measurement solution, and for example, a potassium hydroxide aqueous solution as a washing solution. The measurement was carried out by introducing it into the electrolytic cell at the end of each measurement.

  As a result, as shown in FIG. 5, the fluctuation range when the electrode of Comparative Example 1 was used was about 10.3%. When the electrode of Comparative Example 1 was analyzed by X-ray diffraction, it was found that (220) and (200) were preferentially oriented as shown in FIG. The orientation rate was 54%.

  Further, when the crystal structure of the cross section in the plate thickness direction of the platinum portion was observed by electron beam backscattering pattern analysis, the platinum was not layered, and the particle size was very coarse as shown in FIG. all right.

When such an electrode is used, as the analysis repeats, that is, with the progress of surface etching, the etching rate difference within the electrode surface increases, and the unevenness and surface area variation caused by etching increase, resulting in an electrochemical response. The fluctuation is thought to have increased.
(Comparative Example 2)
In Comparative Example 2, the measurement was repeated using glucose as an analysis object in the same manner as in Example 4 using the laminated electrode with a coarse crystal structure of the platinum part of Comparative Example 1 as the working electrode. As a result of the measurement, as shown in FIG. 10, the fluctuation range between the first analysis and the 60000th analysis is 4.2%, which is larger than that of Example 4.
(Comparative Example 3)
In Comparative Example 3, the laminated electrode in which the crystal structure of the platinum portion of Comparative Example 1 was coarse was used as a working electrode, and the measurement was repeated using urea as an analysis target in the same manner as in Example 5. As a result of the measurement, as shown in FIG. 10, the fluctuation range between the first analysis and the 60000th analysis is 3.7%, which is larger than that in Example 5.
(Comparative Example 4)
In Comparative Example 4, the measurement was repeated using cholesterol as an analysis target in the same manner as in Example 6 using the laminated electrode with a coarse crystal structure of the platinum part of Comparative Example 1 as the working electrode. As a result of the measurement, as shown in FIG. 10, the fluctuation range between the first analysis and the 60000th analysis is 7.3%, which is larger than that in Example 6.
(Comparative Example 5)
In Comparative Example 5, the measurement was performed repeatedly using uric acid as an analysis target in the same manner as in Example 7 using the laminated electrode in which the crystal structure of the platinum portion of Comparative Example 1 was coarse as the working electrode. As a result of the measurement, as shown in FIG. 10, when the fluctuation range between the first analysis and the 60000th analysis is obtained, it is 8.8%, which is larger than that in Example 7.
(Comparative Example 6)
In Comparative Example 6, the laminated electrode in which the crystal structure of the platinum portion in Comparative Example 1 was coarse was used as a working electrode, and the measurement was repeated using creatinine as an analysis target in the same manner as in Example 8. As a result of the measurement, as shown in FIG. 10, the fluctuation range between the first analysis and the 60000th analysis is 11.2%, which is larger than that of Example 8.
(Comparative Example 7)
In Comparative Example 7, the laminated electrode in which the crystal structure of the platinum portion in Comparative Example 1 was coarse was used as a working electrode, and the measurement was repeated using creatinine as an analysis target in the same manner as in Example 9. As a result of the measurement, as shown in FIG. 10, the fluctuation range between the first analysis and the 60000th analysis is 12.6%, which is larger than that of Example 9.
(Comparative Example 8)
In Comparative Example 8, the laminated electrode in which the crystal structure of the platinum portion in Comparative Example 1 was coarse was used as a working electrode, and the measurement was repeated using fatty acid as an analysis target in the same manner as in Example 10. As a result of the measurement, as shown in FIG. 10, the fluctuation range between the first analysis and the 60000th analysis is 7.2%, which is larger than that of Example 10.
(Comparative Example 9)
In Comparative Example 9, the measurement was repeated with bilirubin as the analysis target in the same manner as in Example 11 using the laminated electrode with a coarse crystal structure of the platinum part of Comparative Example 1 as the working electrode. As a result of the measurement, as shown in FIG. 10, the fluctuation range between the first analysis and the 60000th analysis is 6.6%, which is larger than that of Example 11.
It was.

  When the laminated electrodes of Comparative Examples 2 to 9 were used, as the analysis was repeated, that is, with the progress of surface etching, the etching rate difference in the electrode surface was large, and the unevenness caused by the etching and the variation of the surface area increased, It is thought that the fluctuation of electrochemical response became large.

  In addition, although the Example of this invention mentioned above is an example at the time of applying this invention to the working electrode of an electrochemical analyzer, this invention can be applied not only to a working electrode but to a counter electrode. If the present invention is also applied to the counter electrode, the analysis data can be made more accurate.

  DESCRIPTION OF SYMBOLS 1 ... Electrolytic cell, 2 ... Working electrode, 3 ... Counter electrode, 4 ... Reference electrode, 5 ... Potential application means, 6 ... Measuring means, 7 ... Lead wire, 8 ... Measurement solution container, 9 ... Buffer container, 10 ... Washing liquid container, 11 ... Solution dispensing mechanism, 12 ... Solution injection mechanism, 13 ... Solution introduction tube, 14 ... -Solution discharge pipe, 15 ... Solution discharge mechanism, 16 ... Waste liquid container, 20, 60, 90, 120, 180 ... Flow cell, 21, 22 ... Hole, 30, 32, 70, 72, 100, 102, 130, 132, 190, 192 ... Insulating substrate, 31, 71, 101, 131 ... Seal member, 33, 73, 103, 133, 193 ... Screw hole, 34, 74, 104, 134, 194 ... working electrode, 35, 75, 105, 135, 195 ... counter electrode, 6, 76, 106, 136 ... opening, 37, 38, 77, 78, 107, 108, 137, 138, 197, 198 ... piping, 39, 40, 79, 80, 109, 110, 139 140, 199, 200 ... lead wire, 50 ... working electrode manufacturing apparatus, 50a ... platinum plate processing section, 50b ... platinum plate cold rolling section, 50c ... surface oxide film removal section , 50d... Laminated electrode creation unit, 50e... Cutting unit, 50f... Electrodeization unit, 50g... Resin embedding unit, 50h. ... Energization bolts, 142 ... Energization plates, 143 ... Thread grooves, 191 ... O-rings

Claims (14)

In an electrode for electrochemical measurement used in an electrochemical analyzer for measuring an electrochemical response of a chemical component contained in a liquid sample,
A valve metal of any one of Ti, Ta, Nb, Zr, Hf, V, Mo, W and a platinum part are laminated,
Electrochemical measurement electrode thickness direction of the cross-section crystal structure of the platinum portion is characterized in that it is formed in layers with respect to the electrode surface. The electrode for electrochemical measurement according to claim 1,
An electrode for electrochemical measurement, wherein the plane orientation (220) is preferentially oriented among the diffraction peaks of platinum detected by X-ray diffraction on the electrode surface. The electrode for electrochemical measurements according to claim 2,
The orientation ratio (%) in each direction is I (hkl) / Si [I (hkl)] × 100 (where I (hkl) is the integrated value of diffraction intensity of each surface,
An electrode for electrochemical measurements, wherein the orientation ratio of the plane orientation (220) is 80% or more, where Si [I (hkl)] is the sum of I (hkl). The electrode for electrochemical measurements according to any one of claims 1 to 3,
An electrode for electrochemical measurement, wherein the thickness of each layer of the platinum portion is 5 μm or less. The electrode for electrochemical measurements according to any one of claims 1 to 4,
An electrode for electrochemical measurement, wherein the platinum portion has a thickness of 10 to 100 µm. In the electrolytic cell in which the working electrode, counter electrode, and reference electrode are arranged,
An electrolytic cell, wherein the working electrode is an electrode according to any one of claims 1 to 5. The electrolysis cell according to claim 6,
An electrolysis cell, wherein the electrolysis cell is a flow cell. In an electrochemical analyzer for analyzing a liquid sample,
An electrolytic cell in which a working electrode, a counter electrode, and a reference electrode are disposed; and
A solution injection mechanism for injecting a measurement solution and a buffer solution in the electrolytic cell;
The working electrode, and potential applying means for applying a potential to the counter electrode, the reference electrode,
The working electrode, the counter electrode, is connected to the reference electrode and a measuring means for measuring the electrochemical properties of the sample solution,
The working electrode is formed by stacking a valve metal and a platinum part of any one of Ti, Ta, Nb, Zr, Hf, V, Mo, and W,
An electrochemical analyzer characterized in that the cross-sectional crystal structure in the plate thickness direction of the platinum portion is formed in a layered manner with respect to the electrode surface. The electrochemical analyzer according to claim 8, wherein
An electrochemical analyzer characterized in that the plane orientation (220) is preferentially oriented among the platinum diffraction peaks detected by X-ray diffraction on the electrode surface. The electrochemical analyzer according to claim 8 or 9,
The electrochemical analyzer is characterized in that each layer of the platinum portion has a thickness of 5 μm or less. The electrochemical analyzer according to any one of claims 8 to 10,
The electrolysis cell is a flow cell;
The electrochemical analyzer is arranged such that the rolling direction of the working electrode forms an angle of 45 to 135 degrees with respect to the flow direction of the measurement solution in the flow cell. In the method for producing an electrode for electrochemical measurement used in an electrochemical analyzer for measuring an electrochemical response of a chemical component contained in a measurement solution,
The platinum part is coated on the surface of the valve metal of any one of Ti, Ta, Nb, Zr, Hf, V, Mo, W,
Laminated into a plate by cold rolling while being facing the platinum portion and platinum-coated surface of said valve metal,
Forming a cross-sectional crystal structure in the plate thickness direction of the platinum portion in a layered manner with respect to the electrode surface;
Forming a laminated electrode in which the thickness of each layer of the platinum part is 5 μm or less,
Electropolishing after mechanically polishing the laminated electrode,
A method for producing an electrode for electrochemical measurement, comprising removing a surface alteration layer of the laminated electrode. In the manufacturing method of the electrode for electrochemical measurements according to claim 12,
The method of manufacturing an electrode for electrochemical measurement, wherein the electropolishing is a step of repeatedly applying a potential multiple times between a hydrogen generation region and an oxygen generation region in an electrolytic solution. In the manufacturing method of the electrode for electrochemical measurements according to claim 12 or 13,
After removing the surface alteration layer, the electrode surface state is diagnosed from the area ratio of at least two of the plurality of hydrogen adsorption / desorption peaks obtained by cyclic voltammetry,
A method for producing an electrode for electrochemical measurement, characterized by repeating electropolishing until a predetermined peak ratio is obtained.

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