Microanalysis chip, electrolyte concentration measurement system, and electrolyte concentration measurement method

Abstract

To provide a microanalysis chip that can sufficiently secure the contact area between a specimen and an ion-selective membrane and the amount of the specimen reacting with the ion-selective membrane, and has excellent measurement sensitivity and ion selectivity.SOLUTION: A microanalysis chip has a channel region surrounded by a channel wall provided inside a porous substrate. The channel region has a first channel chamber, a second channel chamber, and a channel connecting the first channel chamber and the second channel chamber. The first channel chamber has a reference electrode and the second channel chamber has a working electrode. The working electrode is covered with an ion-selective membrane containing components having ion selectivity. An exposed surface of the ion-selective membrane is a dispensing portion into which the specimen is dispensed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a microanalysis chip having a microchannel formed inside a porous substrate, and an electrolyte concentration measurement system and electrolyte concentration measurement method using the microanalysis chip. [Background technology]

[0002] In recent years, microanalysis chips, which utilize micro-sized fine channels to efficiently perform biochemical analysis within a single chip, have been attracting attention in a wide range of fields, including biochemical research, medicine, drug discovery, healthcare, the environment, and food. In the early 1990s, photolithography and molds were used to form micrometer-sized fine channels on glass or silicon, and microanalysis chips were developed that could perform sample pretreatment, stirring, mixing, reaction, and detection on a single chip. As a result, miniaturization of testing systems, rapid analysis, and reduction of specimens and waste liquids were realized.

[0003] Electrochemical analysis, which measures the potential between electrodes immersed in the sample to be analyzed, is widely used in fields such as medicine and the environment. Conventional electrochemical analysis is performed by technicians using sophisticated equipment, which limits the fields and resources available for measurement. However, there is a need for inexpensive, easy-to-use, and disposable microanalytical chips for electrochemical analysis, such as those for medical care in developing countries, remote areas, and disaster sites where medical facilities are inadequate, and for use in airports where the spread of infectious diseases must be prevented at the border.

[0004] Non-Patent Document 1 proposes a filter paper-based measurement device for measuring the concentrations of Na ions and K ions. This device has a dispensing section for dispensing the sample. The dispensed sample permeates from the dispensing section into the working electrode and reference electrode, electrically connecting the two electrodes and enabling potential difference measurement. To achieve a stable potential at the reference electrode, the device deposits KCl ion crystals on the reference electrode. During measurement, KCl dissolves in the sample, maintaining a high concentration of Cl ions in the reference electrode area and achieving a stable reference electrode potential. Furthermore, an ion-selective membrane formed to cover the working electrode selects only the ions to be measured, allowing measurement to be performed without being affected by other ions.

[0005] Patent Document 1 also discloses a method for measuring the concentration of a specific protein contained in a biological sample. A fluorescent substance is placed in a sensing area defined by a hydrophobic barrier formed on a paper substrate, and the concentration of the specific protein is measured by analyzing the fluorescent signal generated by reaction with the sample. It is stated that the sensing area formed by the hydrophobic barrier and the sampling area (biological sample dispensing section) may be the same area. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6415827 [Non-patent literature]

[0007] [Non-Patent Document 1] Nipapan Ruecha, Orawon Chailapakul, Koji Suzuki and Daniel Chitterio “Fully Inkjet-Printed Paper-Based Potentiometric Ion-Sensing Devices” Analytical chemistry August 29, 2017 Published, 89, pp.10608-10616 Summary of the Invention [Problem to be solved by the invention]

[0008] However, with the above-described configuration, the selectivity for a specific ion contained in the specimen becomes unstable, and there are cases where good accuracy in measuring the specimen concentration cannot be obtained. In the configuration of Non-Patent Document 1, a sample dispensed onto the surface of a porous substrate permeates from the surface into the porous substrate, then into the working electrode and reference electrode regions, and contacts the ion-selective membrane formed within the porous substrate. The ion-selective membrane then selects the target ions contained in the sample, and the target ions reach the working electrode. However, macroscopically, contact between the sample and the ion-selective membrane is limited to the interface between the porous substrate and the ion-selective membrane within the porous substrate. Therefore, to achieve good measurement accuracy, precise control of the ion-selective membrane formation conditions was required, such as adjusting the contact area between the porous substrate and the ion-selective membrane within the porous substrate to facilitate permeation of the ion-selective membrane into the voids of the porous substrate. However, Non-Patent Document 1 did not disclose detailed methods for controlling permeation. Furthermore, increasing the length of the interface between the ion-selective membrane and the porous substrate and increasing the area of ​​the ion-selective membrane to increase the interface area between the ion-selective membrane and the porous substrate would result in an increased size of the analytical chip.

[0009] Furthermore, the configuration of Patent Document 1 allows the sensing area formed by the hydrophobic barrier and the sampling area (biological sample dispensing section) to be the same, thereby ensuring contact between the biological sample and the sensing substance in the sensing area. However, in electrochemical measurements, measurements can only be performed when the reference electrode and the working electrode section are maintained at different ion concentrations. For this reason, the configuration disclosed in Patent Document 1, which does not provide a region with a reference ion concentration (a configuration in which the sensing area and the sampling area (biological sample dispensing section) are the same), cannot be applied to electrochemical measurements. In view of the above problems, the present invention aims to provide a microanalysis chip for measuring electrolyte concentrations, which can provide good measurement sensitivity and ion selectivity, as well as an electrolyte concentration measurement system and electrolyte concentration measurement method. [Means for solving the problem]

[0010] In order to achieve the above object, according to one aspect of the present disclosure, A microanalysis chip having a flow path region surrounded by a flow path wall provided inside a porous substrate, the flow path region has a first flow path chamber, a second flow path chamber, and a flow path connecting the first flow path chamber and the second flow path chamber, the first flow chamber has a reference electrode and the second flow chamber has a working electrode; the working electrode is covered with an ion-selective membrane containing a component having ion selectivity; The exposed surface of the ion selective membrane is a dispensing portion into which a sample is dispensed.

[0011] According to another aspect of the present disclosure, A microanalysis chip; a sample supply unit that supplies a sample to the microanalysis chip; a measurement unit that measures a potential difference generated on the microanalysis chip, The microanalysis chip has a flow path region surrounded by a flow path wall provided inside a porous substrate, the flow path region has a first flow path chamber, a second flow path chamber, and a flow path connecting the first flow path chamber and the second flow path chamber, the first flow chamber has a reference electrode and the second flow chamber has a working electrode; the working electrode is covered with an ion-selective membrane containing a component having ion selectivity; the specimen supply unit supplies the specimen so that at least a portion of the specimen covers an exposed surface of the ion selective membrane that covers the working electrode; The measurement unit measures a potential difference between the reference electrode and the working electrode, which is caused by a difference between the ion concentration at the reference electrode and the ion concentration at the working electrode.

[0012] Furthermore, according to another aspect of the present disclosure, A method for measuring an electrolyte concentration using a microanalysis chip, comprising: The microanalysis chip has a flow path region surrounded by a flow path wall provided inside a porous substrate, the flow path region includes a first flow path chamber, a second flow path chamber, and a flow path connecting the first flow path chamber and the second flow path chamber; the first flow chamber has a reference electrode and the second flow chamber has a working electrode; the working electrode is covered with an ion-selective membrane containing a component having ion selectivity; At least a portion of the sample is dispensed onto the exposed surface of the ion selective membrane covering the working electrode; Ions contained in the dispensed sample and selected by the ion selective membrane contact the working electrode; The dispensed sample permeates the flow path and contacts the reference electrode, A method for measuring electrolyte concentration is provided that measures the potential difference between the reference electrode and the working electrode, which is caused by the difference between the ion concentrations at both electrodes. [Effects of the Invention]

[0013] According to one aspect of the present disclosure, it is possible to provide a microanalysis chip with excellent electrolyte concentration measurement sensitivity and ion selectivity by ensuring a sufficient contact area between the analyte and the ion-selective membrane and a sufficient amount of analyte that reacts with the ion-selective membrane. Furthermore, by providing a dispensing section in the flow channel chamber where the ion-selective membrane is located, the length of the flow channel connecting the flow channel chambers can be shortened, thereby enabling the miniaturization of the microanalysis chip. According to another aspect of the present disclosure, it is possible to provide an electrolyte concentration measurement system and an electrolyte concentration measurement method using the above-described microanalysis chip. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a top view showing the configuration of a micro-analysis chip P1 according to Example 1. FIG. [Figure 2] FIG. 2 is a simplified diagram showing the AA cross section of the micro-analysis chip P1 shown in FIG. [Figure 3] FIG. 1 is a schematic diagram of sample dispensing in Example 1. [Figure 4] 4 is a cross-sectional view showing another configuration of the exposed surface of the ion selective membrane according to Example 1. FIG. [Figure 5] 1 shows an example of measurement results in Example 1 and Comparative Example 1. [Figure 6] FIG. 10 is a top view showing the configuration of a micro-analysis chip P2 according to Example 2. [Figure 7] FIG. 10 is a cross-sectional view showing a configuration in which a spacer is provided below a regulating member that overlaps the boundary between an ion selective membrane and a porous substrate. [Figure 8] FIG. 10 is a conceptual diagram illustrating an example of the configuration of a measurement system according to a third embodiment. [Figure 9] FIG. 7 is a simplified diagram showing the AA cross section of the micro-analysis chip P2 shown in FIG. [Figure 10] FIG. 10 is a cross-sectional view showing a configuration in which a portion of the regulating member overlaps the boundary between the ion selective membrane and the porous substrate. DETAILED DESCRIPTION OF THE INVENTION

[0015] The microanalysis chip according to the present invention for solving the above-mentioned problems will be described based on the following examples. Note that the examples shown below are merely examples and are not intended to limit the technical scope of the present invention.

[0016] <Flow path configuration> A schematic diagram of the microanalysis chip P1 according to Example 1 will be explained with reference to FIGS. 1 to 3. FIG. FIG. 1 is a simplified top view of the microanalysis chip P1. FIG. 2 is a simplified diagram showing the AA cross section of the micro-analysis chip P1 shown in FIG. FIG. 3 is a schematic diagram showing the dispensing process for the microanalysis chip P1. The microanalysis chip has a flow path region surrounded by a flow path wall provided inside a porous substrate. A flow path pattern is formed in the porous substrate and has a flow path chamber 1 (first flow path chamber), a flow path chamber 2 (second flow path chamber), and a flow path 3. The flow path 3 connects the flow path chamber 1 (first flow path chamber) and the flow path chamber 2 (second flow path chamber).

[0017] A reference electrode 7 is placed in the flow channel chamber 1 (first flow channel chamber). The top and side surfaces of the reference electrode 7 are covered with ion crystals 10 that are soluble in the sample. The reference electrode 7 has a lead wire that extends continuously from inside the flow channel chamber 1 onto the flow channel wall 5 as a contact point during measurement. A working electrode 8 is disposed in the flow channel chamber 2 (second flow channel chamber). The top and side surfaces of the working electrode 8 are covered with an ion-selective membrane 9 containing a component with ion selectivity. The working electrode 8 has a lead wire that continuously extends from inside the flow channel chamber 2 onto the flow channel wall 5. A dispensing unit 6 that dispenses the sample will be described later.

[0018] [Example 1] In Example 1, a hydrophobic resin was placed on a paper porous substrate S1 having a thickness L1 of 0.1 mm and a porosity of 50%, and then thermally fixed to form a flow path pattern as a flow path wall 5 that is impermeable to samples.

[0019] In this example, a paper substrate was used as the porous substrate, but the porous substrate is not limited to paper. The porous substrate may be any material that generates capillary action in a liquid, and may have a porous structure such as open cells or nanofibers inside, or a mesh-like structure. Alternatively, resin, glass, an inorganic substrate, fabric, metal paper, etc. may be used. In this embodiment, the flow path pattern is formed by thermal fixing after disposing the hydrophobic resin, but the method is not limited to this. Any method may be used as long as the flow path pattern is formed, such as cutting the paper porous substrate S1 to leave only the flow path shape, or forming the flow path walls with a wax printer.

[0020] <Electrode formulation> The electrode formulation for Example 1 will be described. A reference electrode 7 using Ag / AgCl was provided in the flow channel chamber 1. 3.5 mg of KCl ion crystals 10 were placed on the reference electrode 7. On the other hand, a working electrode 8 made primarily of carbon is provided in the flow channel chamber 2. Note that instead of the carbon electrode, an electrode 8 made of a conductive polymer such as PEDOT:PSS (a dispersion of polyethylenedioxythiophene and polystyrene sulfonic acid) may be used. Also, a material such as Ag / AgCl, which has traditionally been used as the base of a reference electrode, may be used.

[0021] A Na ion selective membrane 9 was formed so as to cover the working electrode 8. The ion selective membrane 9 was made of the following material. Ion-selective material Bis(12-crown-4) 3.0 wt% Potassium tetrakis (4-chlorophenyl) borate 0.5wt% as an anion scavenger o-nitro phenyl octyl either 64.0wt% Polyvinyl chloride 32.5wt%

[0022] In this example, the reference electrode 7, the working electrode 8, and the ion selective membrane 9 are formed in the shapes, sizes, and materials described above, but are not limited to these. The material of the ionic crystal 10 is not limited to KCl ionic crystals as long as it contains Cl ions. The mass of the ionic crystal 10 to be placed is not limited to this, but is within the range of mass that results in a saturated solution when the KCl ionic crystal is dissolved in pure water with a volume equivalent to the volume of the flow channel chamber 1.

[0023] Furthermore, when measuring the total amount of ions in a sample or when only one type of ion is contained, there is no need to select an ion, and therefore, in such cases, there is no need to cover the working electrode with the ion selective membrane 9. When the ion selective membrane 9 covering the working electrode is not used, A microanalysis chip having a flow path region surrounded by a flow path wall provided inside a porous substrate, the flow path region has a first flow path chamber, a second flow path chamber, and a flow path connecting the first flow path chamber and the second flow path chamber, the first flow chamber has a reference electrode and the second flow chamber has a working electrode; There is no layer covering the surface of the working electrode within or on the surface of the porous substrate; The working electrode section may be configured as a dispensing section into which a sample is dispensed.

[0024] The phrase "there is no layer covering the surface of the working electrode within or on the surface of the porous substrate" means that there is no layer such as an ion-selective membrane on the surface of the working electrode. In other words, when observing the surface of the microanalysis chip, the first structure that appears other than the porous substrate is the working electrode. Furthermore, the phrase "the working electrode portion is a dispensing portion into which a sample is dispensed" means that, when the working electrode is exposed on the surface of the porous substrate, the sample is dispensed onto the exposed surface; When the working electrode is formed inside the porous substrate, this means that the structure is such that the sample is dispensed onto the surface of the microanalysis chip at the part where the working electrode is present. In the electrolyte concentration measurement system and the electrolyte concentration measurement method, if the ion selective membrane 9 covering the working electrode is not used, the sample may be dispensed toward the working electrode.

[0025] <Shape of dispensing part and dispensing method> In this embodiment, the dispensing section 6 is the exposed surface X of the ion selective membrane 9. The area of ​​the exposed surface X is 5 mm × 10 mm (= 50 mm 2 ) On the other hand, the contact area between the substrate and the ion-selective membrane in the cross section of the porous substrate S1 is (5 mm × thickness of porous substrate 0.1 mm × 2 surfaces) + (10 mm × thickness of porous substrate 0.1 mm × 2 surfaces) = 3 mm 2 In other words, the area of ​​the exposed surface X is sufficiently larger than the contact area between the sample and the ion selective membrane within the cross section of the porous substrate S1. Therefore, by dispensing the specimen onto the exposed surface X, it can be brought into sufficient contact with the ion selective membrane 9 over a wide contact area. In addition, the amount of the dispensed specimen that comes into contact with the ion selective membrane 9 is also sufficient.

[0026] Figure 3(a) shows the entire cross section of the microanalysis chip, and Figure 3(b) shows an enlarged cross section of only the area around the flow channel chamber 2, rather than the entire microanalysis chip. In Figure 3, the dispensed sample S is shown filled in black. As shown in FIG. 3(a), the entire sample may be placed on the exposed surface X of the ion selective membrane 9 immediately after dispensing.

[0027] 3(b), immediately after dispensing, a portion of the specimen may be placed on the exposed surface X of the ion selective membrane 9, and another portion may be placed on the porous substrate S1. In other words, the specimen may be dispensed at the boundary between the ion selective membrane 9 and the porous substrate S1 in the second flow path chamber. It is sufficient that a portion of the specimen is placed on the exposed surface X of the ion selective membrane 9. The blackened areas in FIG. 3 show the state of the sample immediately after dispensing, and after dispensing, the sample spreads over the ion selective membrane 9.

[0028] <Sample penetration> The permeation of the specimen will now be described. After dispensing, ions contained in the specimen and selected by the ion selective membrane 9 permeate toward the working electrode 8. In parallel with this permeation, the specimen spreads on the exposed surface X, comes into contact with the porous substrate present around the ion selective membrane 9, permeates into the porous substrate, and then permeates into the flow channel 3 and the flow channel chamber 1 by capillary action. While the sample was permeating into the flow channel chamber 1, ions contained in the sample in contact with the exposed surface X were selected by the ion selective membrane 9, and the measurement potential of the working electrode 8 required for measuring the electrolyte concentration was stabilized.

[0029] <Measurement of sample concentration> The measurement of analyte concentration will now be described. When the sample penetrates and reaches the KCl ion crystals 10 covering the reference electrode 7, the KCl ion crystals 10 dissolve in the sample, and the Cl ion concentration in the solution in the flow channel chamber 1 becomes saturated. At this time, if the measurement potential of the working electrode 8 is stable, the sample concentration can be measured, and the measurement of the sample concentration is completed after the predetermined measurement time has elapsed. In this embodiment, "ion selection by the ion selective membrane" and "permeation of the specimen into the reference electrode" proceed in parallel, so that the working electrode potential is likely to be stable when the specimen reaches the reference electrode 7.

[0030] In this example, the case where exposed surface X is the dispensing section 6 has been described. If the dispensed volume of the sample is equal to or greater than the volume that can reach flow channel chamber 1 via the upper part of exposed surface X, flow channel chamber 2, and flow channel 3, a sufficient amount of sample can be brought into contact with ion selective membrane 9, and the sample concentration can be measured with good accuracy between the working electrode and the reference electrode.

[0031] 4(a), the exposed surface X of the ion selective membrane 9 is preferably lower in the center than in the peripheral areas and is inclined from the lower central area toward the higher peripheral areas. By inclining the exposed surface X, even if the dispensing position of the sample is slightly shifted from the center or even if the concentration or surface tension of each sample differs, the sample can be naturally placed in the center of the ion selective membrane. Furthermore, as shown in Figure 4(b), by tilting the inclined structure toward the flow path side (making the height of the peripheral part on the flow path side lower than the height of the peripheral part on the opposite side from the flow path), the structure makes it easier for the sample to penetrate into the porous substrate in the flow path chamber 2.

[0032] 4(c), the exposed surface X of the ion selective membrane 9 may be configured so that the central portion is higher than the peripheral portion and is inclined from the higher central portion toward the lower peripheral portion. This configuration allows specimens with different concentrations and surface tensions to come into contact with the ion selective membrane 9 over a wide area of ​​the exposed surface X, and ensures that the specimens penetrate into the porous substrate in the flow path chamber 2.

[0033] For example, for samples with low viscosity, the configuration shown in Figure 4(a) is suitable, as it allows the sample to be naturally concentrated at the center of the ion-selective membrane. The configuration shown in Figure 4(b) allows the sample to be concentrated at the center and further penetrate into the porous material. Conversely, for samples with high viscosity, the configuration shown in Figure 4(c) is suitable, as it allows the sample to be easily penetrated into the porous substrate in the flow channel chamber 2. As described above, it is preferable to provide a difference in height between the central portion and the peripheral portion of the exposed surface of the ion selective membrane; the central portion may be low and the peripheral portion may be high, or conversely, the central portion may be high and the peripheral portion may be low.

[0034] [Comparative Example 1] In order to explain the effects of Example 1 in more detail, Comparative Example 1 will be presented. <Flow path configuration and dispenser shape> The shape of the flow channel wall of the microanalysis chip was the same as in Example 1. The configurations of the reference electrode, working electrode, ion selective membrane, etc. were also the same as in Example 1. However, the dispensing part was not on the exposed surface of the ion selective membrane, but was located at the midpoint in flow channel 3 where the distance from flow channel chamber 1 and the distance from flow channel chamber 2 were equal.

[0035] <Sample penetration> The dispensed sample began to permeate from the dispenser in both directions, toward flow channel chamber 1 and toward flow channel chamber 2, simultaneously reaching flow channel chamber 1 and flow channel chamber 2. The sample that reached flow channel chamber 1 dissolved the KCl crystals in the reference electrode, as in Example 1, to form a saturated Cl ion solution. On the other hand, the sample that reached the flow channel chamber 2 came into contact with the ion selective membrane 9, but the contact was mainly at the boundary position between the porous substrate and the ion selective membrane 9 within the cross section of the porous substrate. Therefore, depending on the state of penetration of the ion selective member into the voids of the porous substrate and the shape of the ion selective membrane arranged within the porous substrate, sufficient measurement sensitivity and ion selectivity may not be obtained.

[0036] [Effects of Example 1] [Advantages of Example 1 over Comparative Example 1] The advantages of Example 1 over Comparative Example 1 will be described. The electrolyte concentration was measured by the mixed solution method specified in JIS K0122, General Rules for Ion Electrode Measurement Methods. The solution containing the ions to be measured was NaCl, and the solution containing the coexisting ions was KCl. The KCl concentration was fixed at 10 mmol / L, and the NaCl concentration was varied in five steps: 10 μmol / L, 100 μmol / L, 1 mmol / L, 10 mmol / L, and 100 mmol / L. The sample volume was 30 μL to 50 μL.

[0037] The experimental results are shown in FIG. 5. FIG. 5(a) shows the logarithmic Na ion concentration (logC Na +) and the measured potential (potential after stabilization). Sensitivity represents the slope of the region where the slope of the measured potential versus logarithmic Na ion concentration is non-negative and constant. The ion selectivity coefficient indicates how many orders of magnitude smaller the target ion can be detected than the coexisting K ion; the larger the negative value, the better.

[0038] As shown in Figure 5(a), the non-negative linear rising point in Example 1 was in the range of logarithmic Na ion concentration from -4 (mol / L) to -3.5 (mol / L). In this example, the logarithmic concentration of coexisting K ions was -2, which indicates that the target Na ions can be measured at concentrations that are one order of magnitude lower. On the other hand, as shown in FIG. 5(b), in Comparative Example 1, it was difficult to determine the region where the measurement potential rose, and the determination of the ion selectivity coefficient and sensitivity was unstable.

[0039] The results are summarized in Table 1. In Example 1, the sensitivity required for measurement was obtained and the ion selectivity was also good, but in Comparative Example 1, the ion selectivity was not constant in each measurement where the ion concentration was changed, and it was shown that the concentration measurement may become unstable. In the configuration of Example 1, the area of ​​the ion selective membrane 9 that comes into contact with the sample is increased, which makes it possible to increase the amount of sample that reacts with the ion selective membrane 9, and it has been shown that both measurement sensitivity and ion selectivity are excellent, making it effective for measuring electrolyte concentrations. Furthermore, by providing a dispensing section 6 in the flow channel chamber 2 where the ion selective membrane 9 is located, the length of the flow channel 3 connecting the flow channel chamber 1 and the flow channel chamber 2 can be shortened, which also leads to the miniaturization of the device (microanalysis chip).

[0040] [Table 1]

[0041] [Example 2] The microanalysis chip P2 in the second embodiment will be described. FIG. 6 is a top view showing a schematic configuration of the micro-analysis chip P2. FIG. 9 is a simplified diagram showing the AA cross section of the micro-analysis chip P2 shown in FIG. 6 and 9 indicate the restricting member 11. As shown in Fig. 6 and 9, in the micro-analysis chip P2 of this embodiment, almost all of the flow path chamber 1, all of the flow paths 3, and the periphery of the dispensing section 6 of the flow path chamber 2 are covered with the restricting member 11, which is impermeable to specimens. As the restricting member 11, for example, a laminated film made of PET (polyethylene terephthalate) can be used.

[0042] The restricting member 11 covers the periphery of the dispensing unit 6 in the flow path chamber 2, and has an opening that exposes the upper surface of the ion selective membrane 9. This prevents dispensing essentially onto any surface other than the exposed surface X of the ion selective membrane 9, and the opening of the restricting member 11 becomes the dispensing unit 6. The sample dispensed into the dispensing unit 6 spreads over the exposed surface X of the ion selective membrane 9, permeates from the exposed portion 91 of the porous substrate S1 into the porous substrate S1, and then permeates through the flow path.

[0043] As shown in Figure 10, the opening of the regulating member 11 can be made small so that a part of the regulating member 11 (the edge of the opening) overlaps the boundary between the ion selective membrane 9 and the porous substrate S1 on the upper surface of the porous substrate S1. However, at the boundary between the ion selective membrane 9 and the porous substrate S1, in the portion 101 where the edge of the opening of the restricting member 11 overlaps, When the lower surface of the restricting member 11 and the upper surface of the ion selective membrane 9 are adhered to each other, the sample dispensed into the dispensing section 6 (upper surface of the ion selective membrane 9) cannot penetrate the lower surface of the restricting member 11, and as a result, the dispensed sample cannot penetrate into the porous substrate S1.

[0044] For this reason, it is necessary to provide a non-adhesive portion in part of the overlapping area between the lower surface of the restricting member 11 and the upper surface of the ion selective membrane 9 so that the dispensed sample can penetrate into the porous substrate S1 through this non-adhesive portion. 7, a spacer 71 may be inserted between the lower surface of the restriction member 11 and the upper surface of the ion selective membrane 9 at the overlapping portion between the lower surface of the restriction member 11 and the upper surface of the ion selective membrane 9. By inserting the spacer 71, the dispensed sample can permeate from the upper surface of the ion selective membrane 9 to the porous substrate S1 around the inserted spacer 71.

[0045] In particular, when dispensing is performed manually in an analysis using a microanalysis chip, it is necessary to reliably dispense the specimen manually onto the exposed surface of the ion selective membrane 9. For this reason, as in this embodiment, it is preferable to cover the periphery of the ion selective membrane 9 with a restricting member that does not allow the specimen to penetrate, and to configure the specimen so that it can only be dispensed onto the exposed surface X of the ion selective membrane that is not covered by the restricting member.

[0046] [Example 3] A third embodiment will now be described. The microanalysis chip may be used as part of an electrolyte concentration measurement system (hereinafter also simply referred to as a "measurement system") that measures a plurality of test chips in sequence. FIG. 8 conceptually shows an example of a measurement system. The analytical chip P3 is placed on the measurement table 31. The measurement system also includes a dispenser (sample supply unit) 32. The dispenser 32 includes a sample container 321 that contains a sample, and a supply device 322 that supplies the sample based on an external signal. The sample container 321 and the supply device 322 may be an integrated pipette, or the supply device 322 may pressurize the sample contained in the sample container 321 based on an external signal to supply a fixed amount of sample to the analytical chip P3. The dispenser 32 is supported by a dispenser support arm 81 provided on the measurement table 31.

[0047] The analytical chip P3 can be positioned relative to the measurement system by a step shape (not shown) provided on a positioning section 33 provided on either or both of the measurement table 31 and the dispenser support arm 81. When the analytical chip P3 is positioned at a predetermined position, the relative positional relationship between the dispenser 32 (sample supply section) and the dispenser section 6 (exposed surface of the ion selective membrane 9) is determined, so that a predetermined amount of sample can be reliably dispensed into the dispenser section 6 of the analytical chip P3.

[0048] Alternatively, the analytical chip P3 may have a positioning mark, and the relative positional relationship may be adjusted based on an output indicating that a mark detection unit (not shown) provided in the measurement system has detected the mark. A camera or the like may be used as the mark detection unit. Such a mechanism allows for more precise positioning and allows the sample to be dispensed to a desired position on the exposed surface X of the ion selective membrane 9 (for example, the center of the exposed surface X).

[0049] The measurement system further includes a voltage measurement unit 34. The voltage measurement unit 34 measures the potential difference generated on the microanalysis chip. The voltage measurement unit 34 is connected between the reference electrode 7 and the working electrode 8, and measures the potential difference between the two electrodes, which is generated by the difference between the ion concentration at the reference electrode 7 and the ion concentration at the working electrode 8, at a predetermined timing. According to the measurement system of this embodiment, the microanalysis chip can be quickly placed in a predetermined position on the measurement table, and a predetermined amount of sample can be accurately dispensed onto the exposed surface of the ion-selective membrane, making it suitable as a measurement system for quickly and accurately measuring many samples. [Explanation of symbols]

[0050] 1. Flow channel chamber containing reference electrode 7 2. A flow chamber including a working electrode 8 3: Flow channel connecting flow channel chamber 1 and flow channel chamber 2 5. Channel wall 6. Dispensing section 7...Reference electrode 8...Working electrode 9. Ion-selective membrane Ionic crystals containing 10···Cl ions 11. Regulating member 31 Measuring table 32... Dispenser 33 Positioning part 34 Voltage measurement section S... Specimen S1...Porous base material L1: Thickness of porous substrate X···Exposed surface of ion-selective membrane 9

Claims

1. A microanalysis chip having a flow path region surrounded by a flow path wall provided inside a porous substrate, the flow path region has a first flow path chamber, a second flow path chamber, and a flow path connecting the first flow path chamber and the second flow path chamber, the first flow chamber has a reference electrode and the second flow chamber has a working electrode; the working electrode is covered with an ion-selective membrane containing a component having ion selectivity; the exposed surface of the ion selective membrane is a dispensing portion into which a sample is dispensed; In the dispensing section, the exposed surface of the ion selective membrane has a difference in height between the central section and the peripheral section.

2. 2. The micro-analysis chip according to claim 1, wherein the periphery of the dispensing section is covered with a restricting member that is impermeable to the specimen.

3. 3. The microanalysis chip according to claim 1, further comprising a positioning mark.

4. A microanalysis chip; a sample supply unit that dispenses a sample into the microanalysis chip; a measurement unit that measures a potential difference generated on the microanalysis chip, The microanalysis chip has a flow path region surrounded by a flow path wall provided inside a porous substrate, the flow path region has a first flow path chamber, a second flow path chamber, and a flow path connecting the first flow path chamber and the second flow path chamber, the first flow chamber has a reference electrode and the second flow chamber has a working electrode; the working electrode is covered with an ion-selective membrane containing a component having ion selectivity; the specimen supply unit supplies the specimen so that at least a portion of the specimen covers an exposed surface of the ion selective membrane that covers the working electrode; the measurement unit measures a potential difference between the reference electrode and the working electrode, which is caused by a difference between the ion concentration at the reference electrode and the ion concentration at the working electrode; The exposed surface of the ion selective membrane has a height difference between the central portion and the peripheral portion, and is an electrolyte concentration measurement system.

5. 5. The electrolyte concentration measurement system according to claim 4, further comprising a positioning mechanism for determining the relative positions of the specimen supply unit and the exposed surface of the ion selective membrane.

6. A method for measuring an electrolyte concentration using a microanalysis chip, comprising: The microanalysis chip has a flow path region surrounded by a flow path wall provided inside a porous substrate, the flow path region includes a first flow path chamber, a second flow path chamber, and a flow path connecting the first flow path chamber and the second flow path chamber; the first flow chamber has a reference electrode and the second flow chamber has a working electrode; the working electrode is covered with an ion-selective membrane containing a component having ion selectivity; At least a portion of the sample is dispensed onto the exposed surface of the ion selective membrane covering the working electrode; Ions contained in the dispensed sample and selected by the ion selective membrane contact the working electrode; The dispensed sample permeates the flow path and contacts the reference electrode, The potential difference between the reference electrode and the working electrode, which is caused by the difference in ion concentration between the reference electrode and the working electrode, is measured. The exposed surface of the ion selective membrane has a height difference between the central portion and the peripheral portion, and the method for measuring electrolyte concentration.

7. The method for measuring an electrolyte concentration according to claim 6 , wherein the sample is dispensed into a boundary between the ion selective membrane and the porous substrate in the second flow channel chamber.

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