Electrochemical measuring device, electrochemical sensor, and electrochemical measuring method

Abstract

To be able to electrochemically measure a trace of sample liquid, for example, liquid of several μL order.SOLUTION: An electrochemical measurement device 100, for electrochemically measuring a component of a measurement target included in a sample liquid, comprises: a sensor body 2 having a sensing surface 2S onto which a liquid junction part 21c for contacting an internal liquid 21b to the sample liquid and a sensitive part 22a sensitive to the component of the measurement target are exposed; and a cover body 4 for sandwiching the sample liquid with the sensing surface 2S, covering the liquid junction part 21c and the sensitive part 22a, and diffusing the sample liquid into the liquid junction part 21c and the sensitive part 22a.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an electrochemical measurement device, an electrochemical sensor, and an electrochemical measurement method for electrochemically measuring a component to be measured contained in a sample solution.

Background Art

[0002] In an ion sensor such as a pH sensor, there is a device that has been miniaturized by using an ISFET (Ion Sensitive Field Effect Transistor) chip as a sensor chip for electrochemical measurement instead of a conventional glass electrode.

[0003] For example, as shown in Patent Document 1, an ISFET sensor provided with a probe that constitutes a composite electrode including an ISFET chip and a reference electrode is considered. In this ISFET sensor, a sensitive portion of the ISFET chip and a liquid junction portion of the reference electrode are provided so as to be exposed on a front end surface or a side circumferential surface of a tip portion of the probe. Then, the tip portion of the ISFET sensor is immersed in a sample solution to measure pH or the like, or the ISFET sensor is placed on a table or the like, and a sample solution is dropped or brought into contact with the sensitive portion of the ISFET chip and the liquid junction portion of the reference electrode to measure pH or the like.

[0004] However, in the above ISFET sensor, if the sensitive portion of the ISFET chip and the liquid junction portion of the reference electrode are not electrically connected by the sample solution, the concentration of a component to be measured such as the pH of the sample solution cannot be measured. For this reason, it is necessary to drop a sample solution to such an extent that the sensitive portion of the ISFET chip and the liquid junction portion of the reference electrode are electrically connected. If only a trace amount of the sample solution less than that is dropped or brought into contact, the sample solution does not spread over the sensitive portion of the ISFET chip and the liquid junction portion of the reference electrode, and the concentration of a component to be measured such as pH cannot be measured.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] Therefore, the present invention was made to solve the above-mentioned problems, and its main objective is to enable the reliable electrochemical measurement of minute amounts of sample solution, for example, on the order of a few μL. [Means for solving the problem]

[0007] In other words, the electrochemical measuring device according to the present invention is an electrochemical measuring device for electrochemically measuring a target component contained in a sample liquid, comprising: a sensor body having a sensing surface on which a liquid junction portion that contacts the internal liquid with the sample liquid and a sensing portion that is sensitive to the target component are exposed; and a cover body that sandwiches the sample liquid between itself and the sensing surface and covers the liquid junction portion and the sensing portion, thereby allowing the sample liquid to spread to the liquid junction portion and the sensing portion even if the sample liquid is in a minute amount, wherein the cover body has a removable portion for attaching to and detaching from the sensing surface.

[0008] This electrochemical measuring device allows for the spread of minute amounts of sample liquid that would not otherwise reach the sensing element and liquid junction simply by being dropped or placed on the sensing surface, by using the cover to distribute the sample to both the liquid junction and the sensing element. As a result, it becomes possible to reliably measure minute amounts of sample liquid, such as a few μL, electrochemically. Furthermore, since the cover has a removable section for attaching and detaching it from the sensing surface, handling of the cover is made easier when inserting or removing minute amounts of sample liquid from the sensing surface.

[0009] In order to ensure that the sample liquid is reliably distributed between the sensing surface and the liquid junction and sensing parts, it is desirable that the cover body be made of a material that does not allow liquid to pass through or absorb liquid. If the cover is configured in such a way that it does not allow liquid to pass through or absorb liquid, the sample liquid can be distributed to the liquid junction and sensing part without loss, and minute amounts of sample liquid can be reliably measured electrochemically.

[0010] In order to allow visual confirmation of whether the sample liquid has spread to the liquid junction and the sensing part while the cover body is covering the liquid junction and the sensing part, it is desirable that the cover body be translucent.

[0011] In order to facilitate the spreading of the sample liquid on the sensing surface, it is desirable that the sensing surface be a flat surface.

[0012] The electrochemical measuring device of the present invention can be used not only in a method of measuring by sandwiching the sample liquid between the sensing surface and the cover body, but also in a method of measuring by immersing the sensing surface of the sensor body in the stored sample liquid. In order to be suitably used in such a measurement method, it is desirable that the sensor body be rod-shaped extending along a predetermined axis, with the sensing surface formed on its tip surface.

[0013] It is desirable that the sensing surface is formed at an inclination with respect to a predetermined axis of the sensor body. With this configuration, even if the sensing surface is placed facing downwards and immersed in the sample solution, any bubbles generated can escape along the inclination of the sensing surface.

[0014] As a specific embodiment for miniaturizing the sensing surface, it is desirable that the sensing part be composed of an ISFET chip.

[0015] Furthermore, the electrochemical sensor according to the present invention comprises a sensor body having a sensing surface on which a liquid junction portion that brings the internal liquid into contact with a sample liquid and a sensing portion that is sensitive to a component to be measured contained in the sample liquid are exposed, and a cover body that sandwiches the sample liquid between itself and the sensing surface and covers the liquid junction portion and the sensing portion, and allows the sample liquid to spread to the liquid junction portion and the sensing portion, wherein the cover body has a removable portion for attaching to and detaching from the sensing surface.

[0016] Furthermore, the electrochemical measurement method according to the present invention is an electrochemical measurement method for electrochemically measuring a target component contained in a sample liquid, and is characterized by using a sensor body having a sensing surface on which a liquid junction portion that contacts the internal liquid with the sample liquid and a sensing portion that is sensitive to the target component are exposed, and a cover body that covers the liquid junction portion and the sensing portion and has a removable portion for attaching to and detaching from the sensing surface, and sandwiching the sample liquid between the sensing surface and the cover body, thereby allowing the sample liquid to spread to the liquid junction portion and the sensing portion. [Effects of the Invention]

[0017] According to the present invention described above, for example, minute amounts of sample solution on the order of a few μL can be reliably measured electrochemically. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic diagram of the entire electrochemical measuring device according to one embodiment of the present invention, and a magnified view of the tip of the sensor body (including the cover). [Figure 2] This is a schematic cross-sectional view of the sensor body in the same embodiment, along axis C. Note that the cross-sectional view in (a) and the cross-sectional view in (b) show mutually orthogonal cross-sections around axis C. [Figure 3] This is a schematic, partially enlarged cross-sectional view showing the tip of the sensor body in the same embodiment. [Figure 4]It is a partial enlarged cross-sectional view schematically showing (a) the state before covering the sensing surface with a cover body and (b) the state after covering the sensing surface with the cover body in the same embodiment. [Figure 5] It is a plan view schematically showing (a) the state before covering the sensing surface with a cover body and (b) the state after covering the sensing surface with the cover body in the same embodiment. [Figure 6] It is a diagram showing configuration examples (a) to (c) of the removal part of the cover body in the same embodiment. [Figure 7] It is a plan view schematically showing the cover body of the modified embodiment.

Mode for Carrying Out the Invention

[0019] Hereinafter, an electrochemical measurement device according to an embodiment of the present invention will be described with reference to the drawings. Note that, for any of the drawings shown below, for the sake of clarity, they are schematically drawn with appropriate omissions or exaggerations. The same components are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0020] <Device Configuration of Electrochemical Measurement Device> The electrochemical measurement device 100 of the present embodiment electrochemically measures the concentration of a measurement target component contained in a sample solution. Note that the measurement target component in the present embodiment is a hydrogen ion, and the electrochemical measurement device 10 serves to measure the hydrogen ion concentration (pH) of the sample solution.

[0021] Specifically, as shown in FIG. 1, the electrochemical measurement device 100 has a sensor body 2 that contacts the sample solution and measures the pH contained in the sample solution, and an arithmetic device 3 that calculates the pH and the like based on the output signal from the sensor body 2. The arithmetic device 3 has an operation unit 31 for operating calibration, measurement, etc. of the sensor body 2, a display unit 32 for displaying measurement values such as pH, and the like. The sensor body 2 and the arithmetic device 3 are connected by a cable K. <(

[0022] As shown in Figure 2, the sensor body 2 has a composite electrode consisting of a reference electrode 21 that serves as a reference for detecting electrode potential and a measuring electrode 22 that measures pH. The sensor body 2 in this embodiment is rod-shaped and extends along a predetermined axis C, and a cable K is connected to its axial base end. In this embodiment, the body 20 that houses or holds the reference electrode 21 and the measuring electrode 22 is also rod-shaped and extends along the predetermined axis C. This body 20 is made of a non-water-permeable resin.

[0023] The reference electrode 21 has an internal electrode 21a, such as a silver / silver chloride electrode; an internal liquid 21b, which is a gel of, for example, a KCl solution in which the internal electrode 21a is immersed; and a liquid junction 21c made of a porous material such as ceramics that brings the internal liquid 21b into contact with the sample liquid. The internal electrode 21a of the reference electrode 21 is connected to cable K by relay wiring.

[0024] The measuring electrode 22 is constructed using an ISFET (Ion Sensitive Field Effect Transistor) chip. In this embodiment, the ISFET chip 22 has an ion-sensitive film, such as tantalum pentoxide, formed on the gate insulating film to create the sensing portion 22a. The measuring electrode 22 is fixed between the body 20 and the substrate 23, which will be described later (see Figure 3).

[0025] Furthermore, a sensing surface 2S is formed on the axial end surface of the sensor body 2 (in this case, the body 20). This sensing surface 2S is a flat surface, and in this embodiment, it is formed at an inclination with respect to a predetermined axis C (see Figure 2(a)).

[0026] Furthermore, as shown in Figures 1 to 3, the sensing surface 2S is exposed so that the liquid junction portion 21c, which brings the internal liquid 21b into contact with the sample liquid, and the sensing portion 22a of the ISFET chip 22, which is sensitive to the component to be measured, can come into contact with the sample liquid.

[0027] Specifically, the sensing surface 2S is constructed using a flat substrate 23 provided at the axial end of the sensor body 2, as shown in Figure 3. This substrate 23 has through-holes 23h1 for the liquid junction and 23h2 for the sensing element, which penetrate both the front and back surfaces. The liquid junction 21c of the reference electrode 21 is exposed to the outside through the liquid junction 23h1, and the sensing element 22a of the measuring electrode 22 is exposed to the outside through the sensing element 23h2. Wiring is formed on the back surface of the substrate 23, and the ISFET chip 22 is mounted on this back surface, for example, by flip-chip mounting. The ISFET chip 22 is connected to cable K via relay wiring through the substrate 23.

[0028] <Configuration for spreading the sample liquid (cover body 4)> Therefore, as shown in Figures 1, 4, and 5, the electrochemical measuring device 100 of this embodiment is equipped with a cover body 4 that holds a small amount of sample liquid between itself and the sensing surface 2S.

[0029] Specifically, the cover body 4 is separate from the sensor body 2 and is configured to be impermeable to liquids or to absorb liquids. Specifically, the liquid-contacting surface of the cover body 4 that comes into contact with the sample liquid is impermeable to liquids. The liquid-contacting surface of the cover body 4 is the surface that faces the sensing surface 2S when the sample liquid is sandwiched between the cover body 4 and the sensing surface 2S. In this embodiment, the cover body 4 is made of, for example, a non-porous film or glass. In addition, the cover body 4 has light-transmitting properties, such as transparency. Furthermore, in this embodiment, since the sensing surface 2S is a flat surface, the liquid-contacting surface of the cover body 4 is also a flat surface.

[0030] As shown in Figures 4 and 5, the cover body 4 sandwiches the sample liquid between itself and the sensing surface 2S and covers the liquid junction portion 21c and the sensing portion 22a exposed from the sensing surface 2S. The cover body 4 has a shape that covers at least a part of the liquid junction portion 21c and at least a part of the sensing portion 22a, and in this embodiment, it has a shape that covers all of the liquid junction portion 21c and all of the sensing portion 22a (see Figures 4(b) and 5(b)). In this embodiment, the cover body 4 is circular in plan view, but it may also have other shapes, such as rectangular in plan view. When the sample liquid is sandwiched between the cover body 4 and the sensing surface 2S, the cover body 4 pushes the sample liquid out and spreads it to the liquid junction portion 21c and the sensing portion 22a (see Figures 4(b) and 5(b)).

[0031] Here, it is said that the sample liquid spreads to the liquid junction 21c and the sensing part 22a, meaning that the sample liquid comes into contact with at least a portion of the liquid junction 21c and at least a portion of the sensing part 22a, and that the liquid junction 21c and the sensing part 22a become electrically connected by the sample liquid.

[0032] <Measurement method using electrochemical measuring device 100 (electrochemical measurement method)> Next, a method for measuring the pH of a sample solution using the electrochemical measuring device 100 of this embodiment will be described.

[0033] (1) Measurement method without using cover body 4 When measuring without using the cover body 4, it is conceivable to immerse the sensing surface 2S of the sensor body 2 in the sample solution and measure the pH of the sample solution. Alternatively, it is conceivable to position the sensor body 2 with its sensing surface 2S facing upwards, drop the sample solution onto the sensing surface 2S, and measure the pH of the sample solution. In addition, it is conceivable to bring a holding member (not shown) impregnated with the sample solution into contact with the sensing surface 2S of the sensor body 2 and measure the pH of the sample solution.

[0034] (2) Measurement method using cover body 4 When measuring using the cover body 4, the sensor body 2 is positioned so that its sensing surface 2S faces upward, and a small amount of sample liquid is dropped onto the sensing surface 2S (see Figures 4(a) and 5(a)). Here, a small amount of sample liquid is, for example, an amount that remains on the sensing surface 2S due to surface tension, etc., and does not come into contact with both the sensing part 22a and the liquid junction part 21c. Specifically, the range of the amount of sample liquid is 2 μL to 50 μL, and more specifically, 5 μL to 30 μL is preferable.

[0035] Then, by placing the cover body 4 over the sensing surface 2S on which the sample liquid has been dropped, the sample liquid is sandwiched between the sensing surface 2S and the cover body 4 (see Figures 4(b) and 5(b)). At this time, the sample liquid on the sensing surface 2S is pushed toward the sensing surface 2S by the cover body 4 and spreads within the sensing surface 2S, reaching both the sensing part 22a and the liquid junction part 21c. This makes it possible to measure the pH of a small amount of sample liquid.

[0036] Alternatively, the cover body 4 may be placed on the top surface of a table or the like, and a small amount of sample liquid may be dropped onto the top surface of the cover body 4. Then, the sensor body 2 may be operated so that the sensing surface 2S of the sensor body 2 comes into contact with the sample liquid on the top surface of the cover body 4, and the sample liquid is sandwiched between the sensing surface 2S and the cover body 4.

[0037] Furthermore, the cover body 4 of this embodiment is provided with a removable portion 40 to facilitate handling of the cover body 4. This removable portion 40 is an area that the operator touches when performing tasks such as sandwiching a small amount of sample liquid between the cover body 4 and the sensing surface 2S or removing the cover body 4.

[0038] Specifically, as shown in Figure 6(a), a knob portion 4T may be provided on the cover body 4 as a removable portion 40. By grasping this knob portion 4T with a person's hand or using an instrument such as tweezers, the cover body 4 can be easily handled. The knob portion 4T is preferably made of a material that does not allow liquid to pass through or absorb liquid, similar to the cover body 4. The material of the knob portion 4T is, for example, a non-porous film or glass. In addition, the cover body 4 has light-transmitting properties, such as being transparent. The knob portion 4T may be molded integrally with the cover body 4, or it may be attached to the cover body 4 by heat welding or adhesion with an adhesive. The position of the knob portion 4T may be provided in the center or at the end of the flat plate portion of the cover body 4. Furthermore, the knob portion 4T may be provided extending in a direction that intersects the flat plate portion of the cover body 4, for example, perpendicularly, or it may be provided parallel to the two flat plate portions.

[0039] Alternatively, the cover body 4 may be configured to be attached to and fixed to the sensor body 2. In this case, as shown in Figure 6(b), the cover body 4 has a facing surface portion 41 that faces the sensing surface 2S and a fixing portion 42 for fixing the facing surface portion 41 to the sensor body 2. Specifically, the cover body 4 can be a cap structure that is fitted onto the tip of the sensor body 2. Here, for example, the cylindrical fixing portion 42 becomes the removal portion 40.

[0040] Furthermore, as shown in Figure 6(c), the cover body 4 may be a flat plate that, for example, forms a rectangular shape in plan view, with the four corners of the cover body 4 (the parts that extend beyond the sensing surface 2S) serving as removable parts 40. In this case, the area of ​​the cover body 4 is larger than the area of ​​the sensing surface 2S.

[0041] <Effects of this embodiment> With the electrochemical measuring device 100 of this embodiment configured in this way, a minute amount of sample liquid that would not spread to the liquid junction 21c and sensing part 22a by simply dropping or contacting it on the sensing surface 2S can be spread by the cover body 4, allowing it to reach the liquid junction 21c and sensing part 22a. As a result, it becomes possible to reliably measure a minute amount of sample liquid, for example, on the order of a few μL, electrochemically. Furthermore, since the cover body 4 has a removable part 40 for attaching and detaching it from the sensing surface 2S, the cover body 4 can be easily handled when sandwiching a minute amount of sample liquid between the cover body 4 and the sensing surface 2S or when removing the cover body 4.

[0042] <Other modified embodiments> However, the present invention is not limited to the embodiments described above.

[0043] For example, the area of ​​the cover body 4 that covers the sensing surface 2S can be made smaller than the sensing surface 2S itself. With this configuration, a small amount of sample liquid can be reliably brought into contact with the sensing surface 2S.

[0044] Furthermore, as shown in Figure 7, the cover body 4 of the above embodiment may be subjected to hydrophilic or hydrophobic treatment on the liquid-contacting surface that comes into contact with the sample liquid.

[0045] For example, when the liquid-contacting surface of the cover body 4 is subjected to hydrophobic treatment, it is desirable that the hydrophobic region, as shown in Figure 7(a), be formed in a position that surrounds, for example, at least a part of the sensing part 22a and at least a part of the liquid junction part 21c. With this configuration, the sample liquid spread out by the cover body 4 is more likely to remain inside the hydrophobic region, and the sample liquid can be reliably brought into contact with the sensing part 22a and the liquid junction part 21c.

[0046] Furthermore, when the liquid-contacting surface of the cover body 4 is treated with a hydrophilic coating, it is desirable that the hydrophilic region, as shown in Figure 7(b), be formed so that it extends, for example, from at least a part of the sensing portion 22a to at least a part of the liquid junction portion 21c. With this configuration, the sample liquid spread out by the cover body 4 can spread more easily within the hydrophilic region, ensuring that the sample liquid comes into reliable contact with the liquid junction portion 21c and the sensing portion 22a.

[0047] Furthermore, if both hydrophobic and hydrophilic treatments are applied to the liquid-contacting surface of the cover body 4, for example, it is conceivable to form a hydrophilic region inside the hydrophobic region described above.

[0048] In addition, to facilitate conductivity between the liquid junction 21c and the sensing part 22a with the sample liquid while the sample liquid is sandwiched between the sensing surface 2S and the cover body 4, a groove connecting the liquid junction 21c and the sensing part 22a may be formed on the liquid-contacting surface of the sensing surface 2S or the cover body 4. With this configuration, when the sample liquid is sandwiched between the sensing surface 2S and the cover body 4, the sample liquid conducts through the groove to the liquid junction 21c and the sensing part 22a. The position of the groove is not specified, but it is desirable that it be formed between the liquid junction 21c and the sensing part 22a to shorten the distance between them, and in particular, that it be formed to connect the liquid junction 21c and the sensing part 22a by the shortest distance. For example, it is desirable that the groove be formed on a straight line connecting the liquid junction 21c and the sensing part 22a by the shortest distance.

[0049] Furthermore, to make it easier for the user to identify the target location when dropping or bringing a small amount of sample liquid into contact with the sensing surface 2S, it is conceivable to attach a target marker to the sensing surface 2S. This target marker could be placed, for example, between the liquid junction portion 21c and the sensing portion 22a on the sensing surface 2S (for example, in the center).

[0050] In the above embodiment, pH was measured using an ISFET chip. However, by forming an ion-selective film on the gate insulating film of the ISFET chip that selects ions other than protons, the concentration of other ion species (for example, sodium ions, potassium ions, and nitrate ions) may also be measured.

[0051] In the above embodiment, the sensing surface 2S was formed on the tip surface of the sensor body 2, but the sensing surface 2S may also be formed on the outer circumferential surface of the sensor body 2. Furthermore, the shape of the sensor body 2 is not limited to a rod shape extending in a predetermined axial direction, but can be various shapes such as a plate shape.

[0052] Furthermore, although the above embodiment described an electrochemical measuring device consisting of a sensor body 2, a calculation device 3, and a cover body 4, an electrochemical sensor (sensor set) consisting of a sensor body 2 and a cover body 4 is also one embodiment of the present invention.

[0053] Furthermore, various modifications and combinations of the embodiments are permitted, as long as they do not contradict the spirit of the present invention. [Explanation of symbols]

[0054] 100... Electrochemical measuring device 2. Sensor unit 3...Arithmetic unit K-Cable 2S...Sensing surface C...Predetermined axis 20...body 21...Reference electrode 21a...Internal electrode 21b...Internal liquid 21c...Liquid junction 22. Measuring electrode (ISFET chip) 22a...Sensing part 23... Circuit board 4. Cover body

Claims

1. An electrochemical measuring device for electrochemically measuring the target component contained in a sample solution, A sensor body having a sensing surface on which a liquid junction portion that brings the internal liquid into contact with the sample liquid and a sensing portion that is sensitive to the component to be measured are exposed, The system includes a cover body that sandwiches the sample liquid between itself and the sensing surface, covers the liquid junction and the sensing part, and allows the sample liquid to spread to the liquid junction and the sensing part. The electrochemical measuring device wherein the cover body has a removable part that an operator can pinch to remove when attaching or detaching itself from the sensing surface.

2. The electrochemical measuring apparatus according to claim 1, wherein the cover body is configured to be impermeable to liquid or impermeable to liquid.

3. The electrochemical measuring apparatus according to claim 1 or 2, wherein the cover body is translucent.

4. The electrochemical measuring apparatus according to claim 1 or 2, wherein the sensing surface is a flat surface.

5. The electrochemical measuring device according to claim 1 or 2, wherein the sensor body is rod-shaped and extends along a predetermined axis, and the sensing surface is formed on its tip surface.

6. The electrochemical measuring device according to claim 5, wherein the sensing surface is formed at an inclination with respect to a predetermined axis of the sensor body.

7. The electrochemical measuring apparatus according to claim 1 or 2, wherein the sensing element is composed of an ISFET chip.

8. The electrochemical measuring apparatus according to claim 1 or 2, wherein when the sample liquid is dropped onto or brought into contact with the sensing surface which is facing upward, the cover body, the sample liquid, and the sensing surface are arranged in the order of gravity.

9. The electrochemical measuring apparatus according to claim 1 or 2, wherein the area of ​​the cover body that covers the sensing surface is smaller than the sensing surface.

10. The electrochemical measuring device according to claim 1 or 2, wherein the removable portion extends in a direction intersecting the flat plate portion of the cover body that covers the sensing surface.

11. A sensor body having a sensing surface that exposes a liquid junction portion that brings the internal liquid into contact with the sample liquid and a sensing portion that is sensitive to the target component contained in the sample liquid, The system includes a cover body that sandwiches the sample liquid between itself and the sensing surface, covers the liquid junction and the sensing part, and allows the sample liquid to spread to the liquid junction and the sensing part. The cover body has a removable portion that allows an operator to pinch and remove it when attaching or detaching it from the sensing surface, and is an electrochemical sensor.

12. An electrochemical measurement method for electrochemically measuring the target component contained in a sample solution, The sensor body has a sensing surface from which a liquid junction portion that brings the internal liquid into contact with the sample liquid and a sensing portion that is sensitive to the component to be measured are exposed, and the cover body covers the liquid junction portion and the sensing portion and has a removable portion that the operator can pinch to remove it when attaching or detaching it from the sensing surface, An electrochemical measurement method comprising sandwiching the sample liquid between the sensing surface and the cover body, and allowing the sample liquid to spread to the liquid junction and the sensing part.

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