Analysis device and analysis method

Abstract

Provided is an analysis device that is a microchannel device having a plurality of adjacent working electrodes for simultaneously measuring the concentrations of a plurality of kinds of ions in which the ion concentration measurements do not interfere with each other.　The analysis device has: a first channel region having a reference electrode and provided on a substrate; a first working electrode part, which is provided on the substrate and positioned inside or outside the first channel region, and a second working electrode part, which is provided on the substrate and positioned outside the first channel region, wherein a first working electrode is present in the first working electrode part and a second working electrode is present in the second working electrode part; and a restricting member separating the first working electrode part and the second working electrode part, the restricting member being a member that is impermeable to a sample to be analyzed and has a height that does not divide the sample.

Description

Analytical device and analytical method

[0001] The present invention relates to an analytical device having a hydrophilic or porous flow path region surrounded by hydrophobic flow path walls provided inside or on a substrate, and an analytical method using the analytical device.

[0002] In recent years, microanalysis chips that 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.

[0003] In the early 1990s, photolithography and molds were used to form micron-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.

[0004] Electrochemical analysis, which measures the potential between electrodes immersed in the sample to be analyzed, is widely used in the medical and environmental fields. Traditionally, electrochemical analysis has required sophisticated equipment and been performed by technicians, which has limited the fields and resources available for measurement. Therefore, there is a need for inexpensive, easy-to-use, disposable microanalysis chips for electrochemical analysis, which can be used in medical activities in developing countries, remote areas, and disaster sites with limited medical facilities, as well as in airports and other locations where the spread of infectious diseases must be prevented at the border.

[0005] Electrochemical analysis, such as quantifying electrolyte ions in a solution, requires a stable reference electrode that can maintain a constant potential. Conventional glass reference electrodes are expensive and cannot be miniaturized because they require an internal liquid. Furthermore, they require storage in a concentrated ion solution, making them difficult to handle.

[0006] Patent Document 1 proposes a system including a microanalysis chip capable of measuring potential differences using a porous substrate, enabling electrochemical measurements at low cost, with easy handling and disposal. This microanalysis chip includes one or more working electrodes and one reference electrode on a porous substrate. In such a microanalysis chip, electrical continuity between the two electrodes must be established by a fluid during measurement. Patent Document 1 describes the use of a highly concentrated aqueous solution of KCl as a reference solution, which is dispensed into a reference region including the reference electrode in order to obtain a stable potential at the reference electrode during measurement.

[0007] Furthermore, Non-Patent Document 1 proposes a filter paper-based analytical device for measuring Na ion concentration and K ion concentration. This analytical device has an inlet for introducing a sample, and the introduced sample permeates from the inlet into the working electrode and reference electrode regions. Furthermore, Non-Patent Document 1 proposes a device in which KCl ion crystals are deposited on the reference electrode to stabilize the potential at the reference electrode. During measurement, KCl dissolves in the sample, maintaining a high concentration of Cl ions in the reference electrode region, thereby achieving a stable reference electrode potential.

[0008] Furthermore, Patent Document 2 proposes an ion concentration measurement device in which a specimen introduction section is provided in a working electrode section in order to obtain sufficient ion selectivity. This makes it possible to ensure a sufficient contact area between the specimen and the ion-selective membrane in the working electrode section, as well as the amount of specimen that reacts with the ion-selective membrane, thereby providing a microanalysis chip with excellent measurement sensitivity for electrolyte concentration and excellent ion selectivity.

[0009] US Patent Application Publication No. 2016 / 033438 JP 2023-048923 A

[0010] Nipapan Ruecha, Orawon Chailapakul, Koji Suzuki and Daniel Citterio “Fully Inkjet-Printed Paper-Based Potentiometric Ion-Sensing Devices” Analytical Chemistry August 29, 2017 Published, 89, pp.10608-10616

[0011] In order to provide the analytical device with multiple functions, it is preferable to have multiple working electrodes (working electrode portions) covered with coating films containing compounds with different ion selectivities. Various arrangements of the multiple working electrode portions are possible. As described above, there is a demand for miniaturization of analytical devices, and by arranging the working electrode portions close to each other and arranging one reference electrode in comparison, it is possible to realize an analytical device that has multiple functions and is compact.

[0012] Furthermore, when an area where the working electrode is located is used as the measurement introduction area when measuring the electrolyte concentration of a sample, it is necessary to arrange each working electrode at a distance that allows them to simultaneously come into contact with the sample dropped in one introduction, in order to reduce the amount of sample and the number of times it is introduced.

[0013] However, when measuring an analyte by introducing it onto multiple working electrodes located close to each other, it has been found that the measured potential at each working electrode may be unstable. When measuring the electrolyte concentration of the introduced analyte, slight changes in the composition of the analyte may occur near the working electrodes due to the uptake of ions into a coating film containing ion-selective compounds or the diffusion of salts within the working electrodes. When the working electrodes are not electrically connected by the analyte or when multiple working electrodes are placed at a sufficient distance from each other, the measurement results are not affected by slight changes in the composition of the analyte. However, when multiple working electrodes are located close to each other, the changes in the composition of the analyte occurring near the working electrodes may interfere with each other, resulting in an unstable measured potential.

[0014] As described above, it is important to arrange multiple working electrode units close to each other in order to reduce the size of the analytical device and the amount of sample, but this may result in a decrease in measurement accuracy. The present invention aims to provide an analytical device that arranges multiple working electrode units close to each other, enabling measurement of electrolyte concentrations by introducing a small amount of sample at a time, while avoiding interference between the working electrode units and enabling stable measurement of ion concentrations.

[0015] According to the present invention, there is provided an analytical device having a hydrophilic or porous flow path region surrounded by a hydrophobic flow path wall provided inside or on a substrate, the analytical device having a first flow path region having a reference electrode provided on the substrate, a first working electrode portion provided on the substrate within the first flow path region or outside the first flow path region, a second working electrode portion provided on the substrate outside the first flow path region, a first working electrode present at the first working electrode portion, a second working electrode present at the second working electrode portion, and a regulating member separating the first working electrode portion and the second working electrode portion, the regulating member being a member that is not permeable by a specimen to be analyzed and having a height that does not divide the specimen. Furthermore, according to the present invention, there is provided an analytical method for measuring the electrolyte concentration of a specimen using an analytical device, wherein the analytical device has a hydrophilic or porous flow region surrounded by a hydrophobic flow wall provided inside or on a substrate, a first flow region having a reference electrode provided on the substrate, a first working electrode portion provided on the substrate within the first flow region or outside the first flow region, a second working electrode portion provided on the substrate outside the first flow region, a first working electrode present at the first working electrode portion, and a second working electrode present at the second working electrode portion, and a regulating member separating the first working electrode portion and the second working electrode portion, wherein the regulating member is a member that is impermeable to the specimen and has a height that does not divide the specimen, and the specimen is supplied to a position where the specimen simultaneously contacts the first working electrode portion, the second working electrode portion, and the regulating member.Further, according to the present invention, there is provided an analytical device having a hydrophilic or porous flow path region surrounded by a hydrophobic flow path wall provided inside or on a substrate, the analytical device having a first flow path region having a reference electrode provided on the substrate, a first working electrode portion provided on the substrate within the first flow path region or outside the first flow path region, a second working electrode portion provided on the substrate outside the first flow path region, a first working electrode present at the first working electrode portion and optionally a coating film containing an ion-selective compound covering at least a portion of the first working electrode, and a second working electrode present at the second working electrode portion and optionally a coating film containing an ion-selective compound covering at least a portion of the second working electrode, at least one of a coating film covering at least a portion of the first working electrode present at the first working electrode portion and a coating film covering at least a portion of the second working electrode present at the second working electrode portion, and a regulating member separating the first working electrode portion and the second working electrode portion, The analytical device is provided in which the restricting member is a member that is not permeable to a specimen to be analyzed and has a height that does not divide the specimen.Further, according to the present invention, there is provided an analytical method for measuring the electrolyte concentration of a sample using an analytical device, wherein the analytical device has a hydrophilic or porous flow region surrounded by a hydrophobic flow wall provided inside or on a substrate, a first flow region having a reference electrode provided on the substrate, a first working electrode portion provided on the substrate within the first flow region or outside the first flow region, a second working electrode portion provided on the substrate outside the first flow region, a first working electrode present at the first working electrode portion and optionally a coating film containing a compound having ion selectivity covering at least a portion of the first working electrode, and a second working electrode present at the second working electrode portion and optionally a coating film containing a compound having ion selectivity covering at least a portion of the second working electrode, and at least one of a coating film covering at least a portion of the first working electrode present at the first working electrode portion and a coating film covering at least a portion of the second working electrode present at the second working electrode portion, The analytical method includes a restricting member separating the first working electrode portion and the second working electrode portion, the restricting member being a member that the specimen does not permeate and having a height that does not divide the specimen, and the specimen is supplied to a position where the specimen simultaneously contacts the first working electrode portion, the second working electrode portion, and the restricting member.

[0016] According to the present invention, in an analytical device having multiple working electrode units capable of simultaneously measuring the concentrations of multiple ions, when the working electrode units are arranged close to each other to minimize the device size, the following effects can be obtained: An analytical device can be provided in which, when a sample is introduced onto multiple working electrode units that are close to each other and measured, interference with the measurements at the multiple working electrode units due to changes in the state of the solution near the working electrode units (working electrodes) is suppressed.

[0017] 9 is a schematic diagram showing a method of dropping a sample when measuring an electrolyte concentration using the analytical device shown in FIG. 1; a schematic diagram showing the shape of a dropped sample droplet; a schematic diagram showing a part of a cross section of the analytical device and sample droplet taken along line AA' when measuring an electrolyte concentration shown in FIG. 3; a schematic diagram showing a part of a cross section of the analytical device and sample droplet taken along line AA' when measuring an electrolyte concentration shown in FIG. 3; a schematic diagram showing a part of a cross section of the analytical device and sample droplet taken along line AA' when measuring an electrolyte concentration when an analytical device not satisfying the present invention is used; a top view of an analytical device according to a conventional technique in Comparative Example 1; a schematic diagram showing a method of dropping a sample when measuring an electrolyte concentration using the analytical device of FIG. 8 according to a conventional technique in Comparative Example 1; a schematic diagram showing a part of a cross section of the analytical device and sample droplet taken along line BB' when measuring an electrolyte concentration shown in FIG. 9; a top view of an analytical device according to Example 2; 12 is a schematic diagram showing a part of a cross section of the analytical device taken along line CC' when a droplet of a sample is dropped onto the analytical device of FIG. 11 to measure the concentration of an electrolyte, and a cross section of the droplet of the sample. FIG.

[0018] An exemplary embodiment of the present invention will be described below with reference to the drawings, with respect to an analytical method according to the present invention that is carried out using an analytical device according to the present invention to solve the above-mentioned problems. Note that the following embodiment is merely an example, and the present invention is not limited to the contents of the embodiment. Furthermore, in the following drawings, components that are not necessary for explaining the embodiment are omitted from the drawings. Note that in the drawings, similar components are given the same reference numbers, and duplicate explanations will be omitted.

[0019] The analytical device according to the present invention has a hydrophilic or porous flow region surrounded by a hydrophobic flow wall provided inside or on a substrate. The analytical device according to the present invention has a first flow region having a reference electrode provided on the substrate. The analytical device also has a first working electrode portion provided on the substrate within or outside the first flow region, and a second working electrode portion provided on the substrate outside the first flow region. The first working electrode portion includes a first working electrode. The first working electrode portion may include a coating film containing an ion-selective compound that covers at least a portion of the first working electrode. The second working electrode portion includes a second working electrode. The second working electrode portion may include a coating film containing an ion-selective compound that covers at least a portion of the second working electrode. The analytical device according to the present invention may include a coating film covering at least a portion of the first working electrode at the first working electrode portion, a coating film covering at least a portion of the first working electrode at the second working electrode portion, or both. That is, at least one of the first working electrode unit and the second working electrode unit may have a working electrode covered with a coating film. The analytical device according to the present invention may have a first working electrode in the first working electrode unit, and a second working electrode in the second working electrode unit, and a coating film containing an ion-selective compound that covers at least a portion of the second working electrode. The analytical device may further have a regulating member separating the first working electrode unit and the second working electrode unit, the regulating member being a member that is impermeable to the analyte to be analyzed and having a height that does not separate the analyte. In this specification, when a working electrode unit (first working electrode unit or second working electrode unit) is present on a flow path region (first flow path region or second flow path region), it is referred to as "the flow path region has a working electrode unit" ("the flow path region has a working electrode unit").

[0020] The analytical method according to the present invention is a method for measuring the electrolyte concentration of a sample using an analytical device, in which the analytical device has a hydrophilic or porous flow path region surrounded by a hydrophobic flow path wall provided inside or on a substrate. The analytical device has a first flow path region having a reference electrode provided on the substrate, a first working electrode portion provided on the substrate within or outside the first flow path region, and a second working electrode portion provided on the substrate outside the first flow path region. The first working electrode portion includes a first working electrode. The first working electrode portion may include a coating film containing an ion-selective compound that covers at least a portion of the first working electrode. The second working electrode portion includes a second working electrode. The second working electrode portion may include a coating film containing an ion-selective compound that covers at least a portion of the second working electrode. The analytical device may include at least one of a coating film covering at least a portion of the first working electrode present on the first working electrode portion and a coating film covering at least a portion of the second working electrode present on the second working electrode portion. The analytical device according to the present invention may include a first working electrode in the first working electrode section, and a second working electrode in the second working electrode section, both of which have a coating film containing an ion-selective compound covering at least a portion of the second working electrode. The analytical device further includes a restricting member separating the first and second working electrode sections, the restricting member being a member impermeable to the analyte to be analyzed and having a height that does not separate the analyte, and the analyte is supplied to a position where it simultaneously contacts the first working electrode section, the second working electrode section, and the restricting member.

[0021] Example 1 <Flow Channel Configuration> Schematic diagrams of an analytical device P1 according to Example 1 will be described with reference to FIGS. 1, 2, and 3. FIG. 1 is a schematic diagram showing a simplified top view of the analytical device P1. The analytical device P1 of Example 1 uses a porous substrate as a substrate, with a hydrophilic or porous flow channel region surrounded by a hydrophobic flow channel wall provided inside or on the substrate. The analytical device P1 has a flow channel pattern including a flow channel wall 1 formed inside the porous substrate 100 using a hydrophobic resin, and multiple flow channel regions surrounded by the flow channel wall 1. The analytical device P1 has a first flow channel region 3 provided on the porous substrate 100, in which a reference electrode 2 is provided, and flow channel regions 7 and 8 that are not connected to the first flow channel region 3. A working electrode 4a provided on the porous substrate 100 is provided within the first flow channel region 3. The working electrode 4a is provided within the first flow channel region 3, and an electrode rod extends from a reaction region that contacts the sample and measures the electrolyte concentration (Cl ion concentration) when measuring the electrolyte concentration of the sample, onto the flow channel wall 1. Further, outside the first flow path region 3, there are a working electrode 5a provided on the porous substrate 100, and a coating film 5b containing an ion-selective compound that covers at least a portion of the working electrode 5a (including the reaction region where the electrolyte concentration is measured when measuring the electrolyte concentration of the analyte). The coating film 5b is a Na ion-selective membrane, and the working electrode 5a is capable of measuring the Na ion concentration. The working electrode 5a has an electrode rod extending from the reaction region provided in the flow path region 7 onto the flow path wall 1. Similarly, outside the first flow path region 3, there are a working electrode 6a provided on the porous substrate 100, and a coating film 6b containing an ion-selective compound that covers at least a portion of the working electrode 6a (including the reaction region where the electrolyte concentration is measured when measuring the electrolyte concentration of the analyte). The coating film 6b is a K ion-selective membrane, and the working electrode 6a is capable of measuring the K ion concentration. The working electrode 6a has an electrode rod extending from the reaction region provided in the flow path region 8 onto the flow path wall 1. In FIG. 1, the flow path wall 1 is indicated by light ink, and the portion of the analytical device P1 that is covered with the coating film 5b or the coating film 6b is indicated by a broken line.

[0022] In the present invention, the first working electrode unit and the second working electrode unit are units that simultaneously contact the sample to be analyzed and measure the electrolyte concentration when measuring the electrolyte concentration of the sample, and the analytical device of the present invention has a restriction member that separates the first working electrode unit and the second working electrode unit. The restriction member in the present invention is a member that separates the first working electrode unit and the second working electrode unit so that the first selected ion measured at the first working electrode unit and the second selected ion measured at the second working electrode unit do not mix. The working electrode units (the first working electrode unit and the second working electrode unit) are indicated by dotted patterns in the figures.

[0023] In the present invention, the analytical device may have a second flow path region. When the analytical device has a second flow path region, (i) when the first working electrode portion is included in the first flow path region, the second flow path region may have a second working electrode portion, and the first flow path region and the second flow path region may be separated from each other by a flow path wall. In the case of (i), the analytical device has one or more second flow path regions, and when the analytical device has multiple second flow path regions, the multiple second flow path regions are separated from each other by flow path walls.

[0024] On the other hand, (ii) when the first working electrode portion is provided outside the first flow path region, the device may have a plurality of second flow path regions, each of which has the first working electrode portion and the second working electrode portion. The first flow path region and the second flow path region are separated from each other by a flow path wall, and the plurality of second flow path regions are separated from each other by a flow path wall.

[0025] In this embodiment, the analytical device P1 may have (i) a first working electrode portion provided on the porous substrate 100 within the first flow path region 3. That is, the first working electrode portion may have a working electrode 4a (including a reaction region) as the first working electrode. The analytical device P1 may have a second working electrode portion provided on the porous substrate 100 outside the first flow path region 3. The second working electrode portion may have a working electrode 5a (including a reaction region) as the second working electrode and a coating film 5b covering at least a portion of the second working electrode (including the reaction region). The second working electrode portion may also have a working electrode 6a (including a reaction region) as the second working electrode and a coating film 6b covering at least a portion of the second working electrode (including the reaction region). That is, the second working electrode portion may have a second working electrode and a coating film containing a compound having ion selectivity that covers at least a portion of the second working electrode.

[0026] As described above, when the analytical device P1 has a first working electrode section in the first flow path region 3, the first working electrode section has a first working electrode, and the second working electrode section has a second working electrode and a coating film covering at least a part of the second working electrode, the regulating member 9 plays the following role: The regulating member 9 separates the first working electrode section from the second working electrode section to prevent mixing of the first selected ion (Cl ion) measured at the first working electrode section and the second selected ion (Na ion or K ion) that has passed through the coating film 5b or 6b and is measured at the second working electrode section.

[0027] In this case, analytical device P1 has, as second flow path regions, flow path regions 7 and / or 8. As the second flow path region, for example, flow path region 7 has, as the second working electrode portion, a working electrode portion where working electrode 5a (including a reaction region portion) and coating film 5b are present. Also, as the second flow path region, for example, flow path region 8 has, as the second working electrode portion, a working electrode portion where working electrode 6a (including a reaction region portion) and coating film 6b are present.

[0028] The first flow path region 3 and the second flow path region 7, the first flow path region 3 and the second flow path region 8, and the plurality of second flow path regions 7 and 8 are separated from one another by the flow path wall 1.

[0029] Alternatively, the analytical device P1 may have (ii) a first working electrode portion provided on the porous substrate 100 outside the first flow path region 3. The first working electrode portion may include, for example, a working electrode 5a (including a reaction region) as the first working electrode and a coating film 5b covering at least a portion of the first working electrode (including the reaction region). That is, the first working electrode portion may include a first working electrode and a coating film containing an ion-selective compound that covers at least a portion of the first working electrode. The second working electrode portion may include a working electrode 6a (including a reaction region) as the second working electrode and a coating film 6b that covers at least a portion of the second working electrode (including the reaction region). That is, the second working electrode portion may include a second working electrode and a coating film containing an ion-selective compound that covers at least a portion of the second working electrode.

[0030] As described above, when the first working electrode unit includes a first working electrode and a coating film covering at least a portion of the first working electrode, and the second working electrode unit includes a second working electrode and a coating film covering at least a portion of the second working electrode, the regulating member 9 serves the following role: The regulating member 9 separates the first working electrode unit from the second working electrode unit so that the first selected ion (Na ion) that has passed through the coating film 5b and is measured at the first working electrode unit and the second selected ion (K ion) that has passed through the coating film 6b and is measured at the second working electrode unit do not mix.

[0031] In this case, analytical device P1 has a plurality of second flow path regions, namely, flow path regions 7 and 8. One of the second flow path regions, for example, flow path region 7, has a working electrode portion where working electrode 5a (including a reaction region) and coating film 5b are present as a first working electrode portion. The other second flow path region, for example, flow path region 8, has a working electrode portion where working electrode 6a (including a reaction region) and coating film 6b are present as a second working electrode portion.

[0032] The first flow path region 3 and the second flow path region 7, the first flow path region 3 and the second flow path region 8, and the plurality of second flow path regions 7 and 8 are separated from one another by the flow path wall 1.

[0033] In the analytical device P1, all working electrode parts that can serve as the first working electrode part and the second working electrode part are separated by a regulating member 9. When there are three or more working electrode parts that can serve as the first working electrode part and the second working electrode part, as in this embodiment, all working electrode parts may be separated by the same regulating member, or all working electrode parts may be separated by different regulating members. In this embodiment, the regulating member 9 is Y-shaped, and all working electrode parts are separated by a single regulating member 9.

[0034] Fig. 2 is a schematic diagram showing a cross section of the analytical device P1 taken along line AA' in Fig. 1. In Example 1, a hydrophobic resin was placed on a paper porous substrate 100 having a thickness t = 0.1 mm and a porosity of 50%, and then thermally fixed to form a flow path wall 1 impermeable to samples.

[0035] In this example, a paper material was used as the porous substrate 100, but the present invention is not limited to this. Any material that can generate capillary action in a liquid may be used, and the porous substrate may have a porous structure such as open cells or nanofibers inside, or may be made of resin, glass, an inorganic substrate, fabric, metallic paper, or the like.

[0036] In this example, a porous substrate 100 having a thickness of 100 μm was used, but the thickness of the porous substrate in the analytical device according to the present invention is not limited to this and can be selected appropriately depending on the purpose. Porous substrates of approximately 20 μm to 300 μm are often used. If the thickness of the porous substrate is 20 μm or less, it may not be able to maintain its strength as a substrate. Furthermore, if the thickness of the porous substrate is 300 μm or more, materials such as coating films may easily diffuse into the analytical device, which may result in a deterioration in dimensional accuracy. However, depending on the application, a thick porous substrate of approximately 600 μm may be used by adjusting the arrangement within the analytical device.

[0037] In the analytical device according to the present invention, the porosity of the porous substrate can be appropriately selected depending on the purpose, but is preferably 20% or more and 90% or less. When the porosity is 90% or less, the strength of the substrate is easily maintained, and when it is 20% or more, the permeability of the sample liquid (analyte) is good, which is preferable. The porosity (%) is calculated by the following formula: Porosity (%) = (true density - apparent density) / true density × 100. The apparent density (g / cm ３ ) is the apparent density (g / cm ３ )=Basic weight (g / m ２ ) / thickness (mm)×1000.

[0038] The hydrophobic resin forming the flow path wall is not particularly limited, and examples thereof include polyester resin, vinyl resin, acrylic resin, styrene-acrylic resin, polyethylene, polypropylene, polyolefin, ethylene-vinyl acetate copolymer resin, and ethylene-acrylic acid copolymer resin.

[0039] In this example, the flow path pattern was formed by thermal fixing after disposing the hydrophobic resin. In this case, a method of using toner particles as the hydrophobic resin (thermoplastic resin) and thermally fixing the resin using an electrophotographic device can be mentioned. For this method, reference can be made to JP 2021-37612 A. The method of forming the flow path pattern is not limited to this. It is sufficient to form a flow path pattern having a flow path region. In addition to a cutting method in which a paper porous substrate is cut to leave only the flow path shape, the flow path walls may be formed using an inkjet printer or a wax printer.

[0040] In this example, multiple flow path regions (flow path regions 7 and 8) are arranged in addition to the first flow path region 3, but these flow path regions do not have to be arranged. That is, the first working electrode portion and the second working electrode portion do not have to be arranged on the flow path region, and may be arranged on the flow path wall.

[0041] <Electrode formulation> The formulation of the electrode used in Example 1 will be described. The first flow path region 3 has a reference electrode 2 made of Ag / AgCl on the porous substrate 100. The reference electrode 2 has a shape in which a reaction region portion is provided in the first flow path region 3 as a contact point with the analyte when measuring the electrolyte concentration of the analyte, and an electrode rod extends continuously onto the flow path wall 1. In addition, 2.5 mg of NaCl ion crystals 11 were placed upstream of the reference electrode 2 in the first flow path region 3.

[0042] In this embodiment, the reference electrode 2 has a shape as shown in FIG. 1 and is formed from the above-mentioned material, but is not limited thereto. It is sufficient that a solution of a constant concentration always reaches the reference electrode 2 when measuring the electrolyte concentration of the sample. It is also possible to dispense with the ionic crystals 11, for example by dripping a saturated ionic liquid into the first flow path region during measurement. Furthermore, the material of the ionic crystals 11 is not limited to a material that contains Cl ions, and the mass of the ionic crystals to be disposed is not limited thereto, but is within a range that results in a saturated solution when NaCl ionic crystals are dissolved in pure water having a volume equivalent to the volume of the first flow path region 3. Furthermore, in this embodiment, the location of the ionic crystals is formed upstream of the reference electrode 2 in the first flow path region 3, but is not limited thereto, and the ionic crystals may be disposed in a manner that covers the top of the reference electrode 2.

[0043] In this example, working electrodes 5a and 6a using PEDOT:PSS were placed outside the first flow path region 3. A coating film 5b, a Na ion-selective membrane, was formed to cover a portion of the working electrode 5a (including the reaction region). The coating film 5b was composed of 3% by mass of Bis(12-crown-4) as an ion-selective material, 0.5% by mass of potassium tetrakis(4-chlorophenyl)borate as an anion-rejecting agent, 64% by mass of o-nitrophenyl octyl ether, and 32.5% by mass of polyvinyl chloride.

[0044] A coating film 6b, which is a K ion-selective membrane, was formed to cover a portion of the working electrode 6a (including the reaction region). The coating film 6b was formed from 1.0 mass% of valinomycin, an ion-selective material, 0.5 mass% of potassium tetrakis(4-chlorophenyl)borate, 65 mass% of o-nitrophenyl octyl ether, and 33.5 mass% of polyvinyl chloride, as an anion-removing agent.

[0045] In this embodiment, a working electrode 5a capable of measuring the concentration of Na ions is arranged with a coating film 5b thereon, and a working electrode 6a capable of measuring the concentration of K ions is arranged with a coating film 6b thereon. When the first working electrode unit and the second working electrode unit are located outside the first flow path region, a coating film covering the working electrode (first working electrode or second working electrode) may be present on either the first working electrode unit or the second working electrode unit, and a coating film may not be present on the other working electrode unit. For example, the first working electrode unit may include a first working electrode without a coating film, and the second working electrode unit may include a second working electrode and a coating film containing an ion-selective compound covering at least a portion of the second working electrode. In this case, the regulating member separates the first working electrode unit from the second working electrode unit to prevent mixing of the first selected ions measured at the first working electrode unit and the second selected ions that have passed through the coating film and are measured at the second working electrode unit.

[0046] In this example, a working electrode 4a capable of measuring the concentration of Cl ions is disposed in the first flow path region 3. The working electrode portion in the first flow path region 3 may include a working electrode capable of measuring the concentration of H ions and a coating film containing a compound having ion selectivity that covers at least a portion of the working electrode. The types and number of ions to be detected are not limited to this, and the presence or absence of a coating film for both the first working electrode and the second working electrode may be determined depending on the types of ions to be detected.

[0047] When the above-described working electrode is included in the first flow path region, the first working electrode section may be included in the first flow path region, and the first working electrode section may include a first working electrode and a coating membrane containing an ion-selective compound that covers at least a portion of the first working electrode. Furthermore, the second working electrode section may be included outside the first flow path region, and the second working electrode section may include a second working electrode and a coating membrane containing an ion-selective compound that covers at least a portion of the second working electrode. In this case, the restricting member separates the first working electrode section from the second working electrode section to prevent mixing of the first selected ions that have passed through the coating membrane and are measured at the first working electrode section and the second selected ions that have passed through the coating membrane and are measured at the second working electrode section.

[0048] Alternatively, the first working electrode unit may be located within the first flow path region, and the first working electrode unit may include a first working electrode and a coating film covering at least a portion of the first working electrode, while the second working electrode unit outside the first flow path region may not include a coating film. That is, the first working electrode unit may include a first working electrode and a coating film containing an ion-selective compound covering at least a portion of the first working electrode, while the second working electrode unit may include a second working electrode. In this case, the restricting member separates the first working electrode unit from the second working electrode unit so as to prevent mixing of the first selected ions that have passed through the coating film and are measured at the first working electrode unit with the second selected ions that are measured at the second working electrode unit.

[0049] Furthermore, the materials of the working electrodes 5a, 6a, and 4a are not limited to these. The arrangement of the electrodes is not limited to this, as long as the multiple working electrode portions (first working electrode portion and second working electrode portion) are arranged in positions where they simultaneously contact the sample when a droplet of the sample is dropped into a measurement introduction portion (described later) during measurement of the electrolyte concentration of the sample. All of the working electrode portions arranged within a range where they simultaneously contact the sample during measurement are separated by a restricting member.

[0050] In the analytical method according to the present invention, the electrolyte concentration of the sample may be measured based on the potential difference between the reference electrode and the first working electrode or the second working electrode.

[0051] (i) When the first flow path region 3 has a first working electrode portion, the first working electrode portion and the second working electrode portion can be connected by simultaneously contacting the sample below the liquid surface of the sample that straddles the restrictor member 9.

[0052] (ii) When the first working electrode portion is located outside the first flow path region 3, the first working electrode portion and the second working electrode portion can be connected by simultaneously contacting the sample below the liquid surface of the sample that straddles the restrictor member 9. Furthermore, at least one of the first working electrode portion and the second working electrode portion can be connected to the first flow path region 3 by simultaneously contacting the sample with the first flow path region 3 below the liquid surface of the sample.

[0053] The analytical device according to the present invention may be arranged such that at least a portion of the first flow path region, at least a portion of the first working electrode portion, at least a portion of the second working electrode portion, and at least a portion of the restricting member are within a circle having a diameter L. L is equal to or smaller than the diameter of a droplet of the analyte to be introduced. The volume of the analyte droplet may be 1 μL or more and 100 μL or less, and the diameter of the analyte droplet may be 2.5 mm or more and 7.5 mm or less.

[0054] In this example, at least a part of the first flow path region 3, at least a part of the working electrode section where the working electrode 4a is present, at least a part of the working electrode section where the working electrode 5a and the coating film 5b are present, and at least a part of the working electrode section where the working electrode 6a and the coating film 6b are present are arranged so as to be within a distance L from one another.

[0055] That is, the reaction regions of all the working electrodes (4a, 5a, and 6a) and the regions where the coating films (5b and 6b) are present are arranged as part of the respective working electrode portions so as to fit within the range of a circle (shown by a dashed line in the figure) having a diameter of L. Note that a portion of the restricting member 9 separating the respective working electrode portions also fits within the range of the circle having a diameter of L. L is equal to or less than the diameter of the droplet d of the sample to be introduced as the analysis target.

[0056] In this example, the region (the portion surrounded by the long two-dot chain line in the figure) including a circle with a diameter of L (circle shown by a dashed line) that includes at least a portion of the first flow path region 3, at least a portion of each of all working electrode portions, and at least a portion of the restricting member 9 is defined as the measurement introduction portion 10. In this example, L is set to 5.0 mm. The measurement introduction portion 10 is a portion into which a droplet d of the analyte to be analyzed is introduced when measuring the electrolyte concentration of the analyte to be analyzed. As a result, the region including a circle with a diameter of L that includes at least a portion of the first flow path region, at least a portion of the first working electrode portion, at least a portion of the second working electrode portion, and at least a portion of the restricting member becomes the measurement introduction portion.

[0057] 3 is a schematic diagram showing a simplified top view of the analytical device P1 and the sample droplet d when the sample droplet d is introduced into the measurement introduction portion 10. In FIG. 3, the sample droplet d indicates the portion with a wave pattern.

[0058] The measurement introduction portion 10 can be marked or otherwise devised so that it is clear that this is the portion into which a droplet of sample is introduced during measurement.

[0059] As a result, all of the working electrode parts (including the reaction region parts of the working electrodes) are positioned so as to simultaneously contact the droplet d of the sample introduced into the measurement introduction part 10. In other words, the sample is supplied to a position so as to simultaneously contact the first working electrode part, the second working electrode part, and the restricting member 9 separating them.

[0060] Note that the distance L (the diameter of the circle indicated by the dashed line) at which the sample droplet d is simultaneously contacted during measurement and introduced into the introduction portion 10 is smaller than the diameter of the sample droplet d being dropped. Figure 4 is a simplified schematic diagram showing the sample droplet d dropped on the analytical device P1. The diameter of the sample droplet d dropped on the analytical device P1 is 2R1, its height is H1, its volume is V1, and its contact angle is θ1. If we assume that the sample droplet d is a part of a sphere (spherical cap), then equation (1) can be obtained using the A half-angle method, which is commonly used to measure contact angles.

[0061] The volume of the part of the sphere, the spherical cap (volume V1 of the droplet) is expressed by equation (2).

[0062] From equations (1) and (2), the diameter 2R1 of the droplet d of the specimen is expressed by equation (3) using the volume V1 and contact angle θ1 of the droplet d dropped on the analytical device P1.

[0063] Therefore, L is a value within the range of the condition shown in equation (3)'.

[0064] In this example, a human serum sample was used as the specimen. The contact angle θ1 of the droplet d dropped onto the analytical device P1 was 88.2°, the volume V1 of the dropped specimen droplet d was 32 μL, and the diameter 2R1 of the droplet d was 5.04 mm, so the distance (above L) of the electrode arrangement range was set to 5 mm.

[0065] As for the possible shapes of droplets d, the highest height of droplets d occurs when the volume of droplets d is 100 μL and the contact angle of the droplet is 88.2°, in which case the height of droplets d is 3.57 mm.Furthermore, the lowest height of droplets d occurs when the volume of droplets d is 1 μL and the contact angle of the droplet is 30° due to the influence of the addition of a surfactant or the like, in which case the height of droplets d is 0.35 mm.

[0066] <Restriction Member> The analytical device P1 has a restriction member 9 that separates the working electrode sections. The restriction member 9 is a member that is not permeable to the sample to be analyzed, and has a height that does not separate the sample.

[0067] In this example, when the creepage distance S between the first working electrode portion and the second working electrode portion adjacent to the restriction member 9 is taken as S, S is equal to or greater than the thickness of a layer containing a concentration distribution that occurs near each of the first working electrode portion and the second working electrode portion adjacent to the restriction member 9 during measurement of the electrolyte concentration of a sample. In the analytical device according to the present invention, the creepage distance S is preferably 532 μm or greater.

[0068] The restricting member 9 is disposed in a region including the closest portion where the working electrode portions are closest to each other (measurement introduction portion 10 in this embodiment). The creeping distance from the surface of one working electrode portion (the coating film if a coating film is present, or the reaction region of the working electrode if no coating film is present) to the surface of the other adjacent working electrode portion across the restricting member 9 (the coating film if a coating film is present, or the reaction region of the working electrode if no coating film is present) is defined as S.

[0069] Using the height H2 of the regulating member 9 shown in FIG. 2 from the surface of each working electrode adjacent to the regulating member 9 and the width W1 of the regulating member 9, the creepage distance S is calculated as W1 + 2H2. The height H2 of the regulating member 9 from the surface of each working electrode adjacent to the regulating member 9 may differ for each working electrode. In this case, the creepage distance S is calculated as W1 + the height H2(1) of the regulating member from the surface of the first working electrode + the height H2(2) of the regulating member from the surface of the second working electrode. The value of H2 is determined within a range that allows measurement of the electrolyte concentration of the analyte. In this example, H2 was set to 75 μm for all of the regulating members. The regulating member 9 was formed using a laminate material consisting of a polyethylene terephthalate sheet and an adhesive primarily composed of acrylic ester, so that the width W1 between the working electrodes was 500 μm. As a result, the creepage distance S was 650 μm.

[0070] However, the height and width of the restricting member are not limited to these. The restricting member is positioned so that changes in the concentration of the sample droplet d near one working electrode do not affect the measurement of ion concentration by the working electrode of the other working electrode. Examples of placement conditions will be described with reference to the drawings. Figure 5 is a schematic diagram showing a portion of a cross section of the analytical device P1 and the sample droplet d taken along line AA' in Figure 3 for the analytical device P1 in Example 1 using the restricting member 9 during electrolyte concentration measurement. Note that in Figure 5, the working electrode portion is not filled in with a pattern to facilitate understanding.

[0071] When measuring the electrolyte concentration of a sample, a droplet d of the sample is dropped onto an area (measurement introduction portion 10) including a circle that includes at least a portion of each working electrode portion (the reaction area portion of each of working electrodes 4a, 5a, and 6a and the coating films 5b and 6b). Then, at the reaction interface, the electrolyte concentration in the sample droplet decreases or increases as the reaction progresses, and a layer with a concentration distribution is generated near the working electrode portion. When an electrode reaction occurs, reactants such as ions are consumed at the interface between the sample and the electrode, causing a concentration change in the sample. This layer with a concentration distribution is called a diffusion layer.

[0072] The thickness H3 of the diffusion layer 13 (the shaded portion) in FIG. 5 is expressed by the equation (4) using the time T1 elapsed since the start of the reaction and the diffusion coefficient D1.

[0073] To prevent diffusion layer 13, which has a concentration distribution near the first working electrode (e.g., the working electrode where working electrode 5a in FIG. 5 is located), from being located near the working electrode of the second working electrode (e.g., the working electrode where working electrode 6a is located), the following condition is satisfied: Each component is arranged so that the surface of the first working electrode (the surface of coating film 5b) is located at a distance equal to or greater than the thickness H3 of diffusion layer 13 (the shaded portion) from the surface of the second working electrode (the surface of coating film 6b). In this embodiment, the height H2 of the regulating member from the first working electrode and the height H2 of the regulating member from the second working electrode are the same, and the condition for creepage distance S under which the diffusion layer near the first working electrode is not affected in measurement at the working electrode of the second working electrode is expressed by the condition of Equation (4)'.

[0074] That is, it is sufficient that the creepage distance S is equal to or greater than the thickness H3 of the diffusion layer 13 generated near each of the first working electrode portion and the second working electrode portion. In this embodiment, the diffusion layer of NaCl near the first working electrode portion is formed over a period of time T1 from the start to the end of measurement of the electrolyte concentration of the sample, which is 60 s, and has a diffusion coefficient D1 of NaCl in a room temperature environment during measurement, which is 1.5×10 －９ Therefore, H3 = 532 μm. In addition, the diffusion layer of KCl near the second working electrode has a time T1 = 60 s and a diffusion coefficient D1 of KCl = 1.95 × 10 －９Therefore, H3 = 606 μm. In order to prevent the working electrodes 5 a and 6 a from being affected by changes in the concentrations of both K and Na ions, in this example, H2 = 75 μm, W1 = 500 μm, and the creepage distance S was set to 650 μm so that the creepage distance S = W1 + 2H2 was 606 μm or more.

[0075] The height H4 of the regulating member shown in FIG. 6 is a height that does not separate the analyte to be analyzed and does not interfere with the electrical connection between the working electrode sections and between the working electrode section and the first flow path region through the analyte droplet. The height H4 of the regulating member is, for example, the height of the portion separating the multiple working electrode sections or the portion separating the working electrode section and the first flow path region in the measurement introduction section, and is the height from the reference point of the height H1 of the droplet d. For example, when the droplet d is dropped so as to contact the porous substrate 100, the height H4 of the regulating member is the height from the porous substrate 100. Furthermore, for example, when the droplet d is dropped onto the working electrode, the height H4 of the regulating member is the height from the working electrode. In the analytical device according to the present invention, the height of the regulating member is preferably equal to or less than the height of the droplet of the analyte to be introduced, and is preferably 3.57 mm or less. The height of the regulating member can be changed depending on the volume of the droplet of the analyte to be introduced, and can be, for example, 0.35 mm or less.

[0076] 6 is a diagram showing a portion of a cross section of the analytical device P1 and the sample droplet d taken along line AA' in FIG. 3 during measurement of the electrolyte concentration of the sample in Example 1. In the analytical device P1, the height H4 of the restricting member 9 is 150 μm, which is shorter than the height H1 of the sample droplet. As a result, during measurement of the electrolyte concentration of the sample, each working electrode portion is electrically connected by the sample droplet. In addition, the height of the restricting member 9, which separates the working electrode 4a of the first flow path region from the other working electrode portions, is also shorter than the height H1 of the sample droplet. As a result, each working electrode portion and the first flow path region are electrically connected by the sample droplet.

[0077] 7 is a schematic diagram showing a cross section of a portion of an analytical device P2 and a sample droplet during measurement when an analytical device P2 not satisfying the present invention is used. The analytical device P2 has a first flow path region (not shown) in which a reference electrode is disposed, as well as flow path regions 207 and 208 separated from the first flow path region by a flow path wall 201. The flow path regions 207 and 208 are separated by the flow path wall 201 and a regulating member 209. The flow path region 207 has a working electrode portion (referred to as a first working electrode portion) provided on a porous substrate 200, in which a working electrode 205a and a coating film 205b containing a compound having ion selectivity are present and covering at least a portion of the working electrode 205a. The flow path region 208 has a working electrode portion (referred to as a second working electrode portion) provided on the porous substrate 200, in which a working electrode 206a and a coating film 206b containing a compound having ion selectivity are present and covering at least a portion of the working electrode 206a. The analytical device P2 further has a restricting member 209 separating the first working electrode portion from the second working electrode portion, and the restricting member 209 is a member that is impermeable to the analyte to be analyzed, and has a height that separates droplets of the analyte during measurement. In Figure 7, the flow path wall 201 indicates the portion shown in light ink, and the working electrode portion indicates the portion with a dotted pattern.

[0078] If the height H4 of the restricting member 209 is set to exceed the height H1 of the introduced droplet d of the sample, the droplet d will be divided by the restricting member 209. In this case, the first working electrode unit and the second working electrode unit will not be electrically connected by the droplet d of the sample, making it impossible to measure the electrolyte concentration with a small amount of sample.

[0079] Therefore, the height H4 of the regulating member is set to a height that does not hinder the electrical connection between the first working electrode portion and the second working electrode portion, and between at least one of the first working electrode portion and the second working electrode portion and the first flow path region when measuring the electrolyte concentration of the sample.

[0080] In this embodiment, as described above, the contact angle θ1 of the dropped sample droplet is 88.2° and the diameter 2R1 is 5.04 mm, so that the droplet height H1 is 2.44 mm according to formula (1). The height H4 of the restricting member must be lower than the droplet height H1. In this embodiment, H2 is 75 μm, and the height H2 of the restricting member from the surface of each of the multiple working electrode portions adjacent to the restricting member is lower than the droplet height H1. Furthermore, the height H4 of the restricting member is 150 μm, which is lower than the droplet height H1. This has confirmed that electrical connection between the working electrodes and between the working electrode and the first flow path region is not impeded when measuring the electrolyte concentration of the sample.

[0081] Comparative Example 1 Comparative Example 1 will be presented to explain the effects of Example 1 in more detail. <Flow Channel Configuration> A top view of an analytical device P3 according to the prior art in Comparative Example 1 is shown in FIG. 8. The analytical device P3 according to the prior art in Comparative Example 1 has a flow channel region surrounded by a flow channel wall 301 formed of a hydrophobic resin provided within a porous substrate 300. The analytical device P3 has a first flow channel region 303 having a reference electrode 302 provided on the porous substrate 300, and flow channel regions 307 and 308 that are not connected to the first flow channel region 303. The first flow channel region 303 has a working electrode 304a provided on the porous substrate 300. The working electrode 304a is provided within the first flow channel region 303, and an electrode rod extends onto the flow channel wall 301 from a reaction region that contacts the sample and measures the electrolyte concentration when measuring the electrolyte concentration of the sample. Further, outside the first flow path region 303, there is a working electrode 305a provided on the porous substrate 300, and a coating film 305b containing an ion-selective compound that covers at least a portion of the working electrode 305a (including a reaction region where the electrolyte concentration is measured). The working electrode 305a has an electrode rod extending from a reaction region provided in the flow path region 307 onto the flow path wall 301. Similarly, outside the first flow path region 303, there is a working electrode 306a provided on the porous substrate 300, and a coating film 306b containing an ion-selective compound that covers at least a portion of the working electrode 306a (including a reaction region where the electrolyte concentration is measured). The working electrode 306a has an electrode rod extending from a reaction region provided in the flow path region 308 onto the flow path wall 301.

[0082] In Figures 8 to 10, the flow path wall 301 refers to the portion indicated by light ink, and in Figure 8, the working electrode portion refers to the portion with a dotted pattern. In this comparative example, the first working electrode portion can be a working electrode portion provided within the first flow path region 303. That is, the first working electrode portion can be a working electrode 304a (including a reaction region portion) as the first working electrode. Furthermore, the second working electrode portion can be a working electrode portion provided outside the first flow path region 303. The second working electrode portion can be a working electrode 305a or 306a (including a reaction region portion) as the second working electrode and a coating film 305b or 306b covering at least a portion of the second working electrode (including the reaction region portion). Furthermore, the second flow path region 307 or 308 can have a second working electrode portion including the working electrode 305a or 306a and the coating film 305b or 306b.

[0083] Alternatively, the first working electrode portion may be a working electrode portion provided outside the first flow path region 303. The first working electrode portion may include a working electrode 305a (including a reaction region portion) as the first working electrode and a coating film 305b covering at least a portion of the first working electrode (including the reaction region portion). The second working electrode portion may include the other working electrode (working electrode 306a, including a reaction region portion) as the second working electrode and a coating film (coating film 306b) covering at least a portion of the second working electrode (including the reaction region portion). The second flow path region 307 may include a first working electrode portion including the working electrode 305a and the coating film 305b, and the second flow path region 308 may include a second working electrode portion including the working electrode 306a and the coating film 306b.

[0084] All of the working electrode sections are arranged so that a portion of each (including the reaction region and coating film of the working electrode) fits entirely within a circular region having a diameter of L, where L is equal to or less than the diameter of the droplet d of the analyte to be introduced. The region (the area surrounded by the long two-dot chain line in the figure) including a circle having a diameter of L (shown by the dashed line in the figure) that includes at least a portion of the first flow path region 303 and at least a portion of each of all of the working electrode sections is defined as the measurement introduction section 310. The measurement introduction section 310 is the site where the droplet d of the analyte to be introduced is introduced when measuring the electrolyte concentration of the analyte.

[0085] The porous substrate and the materials of the flow path walls in the analytical device P3 of this comparative example, as well as the flow path pattern, are the same as those in the first embodiment.

[0086] <Electrode formulation> The shapes, arrangements, and materials of the reference electrode, ion crystal (311), and working electrode in analytical device P3 of this comparative example were the same as those in Example 1. A working electrode 305a capable of measuring the concentration of Na ions and a coating membrane 305b that is a Na ion selective membrane were arranged, a working electrode 306a capable of measuring the concentration of K ions and a coating membrane 306b that is a K ion selective membrane were arranged, and a working electrode 304a capable of measuring the concentration of Cl ions was arranged.

[0087] <Restriction Member> The prior art device P3 according to Comparative Example 1 differs from the analytical device P1 according to Example 1 in that it does not have a restriction member for separating the first working electrode part from the second working electrode part.

[0088] <Measurement of Analyte Concentration> Measurement of the electrolyte concentration of the analyte in Comparative Example 1 will be described using Figures 8 and 9. Figure 9 is a top view schematically showing an analytical device P3 and a droplet d of the analyte according to the prior art in Comparative Example 1, and Figure 10 is a schematic diagram showing a portion of a cross section of the analytical device P3 and the droplet d of the analyte taken along line BB' when measuring the electrolyte concentration of the analyte. In Figure 9, the droplet d of the analyte indicates the portion with a wave pattern. In Figure 10, the droplet d of the analyte and the working electrode portion are not shown filled in with a pattern to facilitate understanding.

[0089] Adjacent working electrode parts are arranged with a minimum distance W2 between the surface of one working electrode part (e.g., the surface of coating film 305b) and the surface of the other working electrode part (e.g., the surface of coating film 306b). In this comparative example, W2 was set to 500 μm. In the vicinity of the working electrode part having working electrode 305a, the time from the start to the end of electrolyte concentration measurement T1 = 60 s, and the diffusion coefficient of NaCl in a room temperature environment during measurement D1 = 1.5 × 10 －９ Therefore, from equation (4), the thickness H3 of the diffusion layer 13 (hatched portion) is 532 μm.

[0090] In this comparative example, the shortest distance W2 from the surface of one working electrode to the surface of the other working electrode is 500 μm, and no restrictor member is present to separate the working electrodes. Therefore, a diffusion layer (a layer with a concentration distribution) near one working electrode (near the coating film 305b) reaches the interface of the other working electrode (the surface of the coating film 306b). This results in a layer of analyte with a concentration distribution different from the analyte electrolyte concentration that should be measured at the specified working electrode reaching the working electrode interface, resulting in a detected potential value that differs from the potential that should be measured. Therefore, different concentrations are detected depending on the value of the shortest distance W2 between the working electrode surfaces. Stable values ​​cannot be obtained, particularly when an analytical device with a small W2 value and a small overall size is used.

[0091] Effect of Analyte Concentration Measurement in Example 1 (Comparison with Comparative Example 1) Comparative Example 1 presented the possibility that the diffusion layer near one working electrode may reach the surface of the other working electrode, resulting in a detected value different from the intended analyte electrolyte concentration. In contrast, Example 1 provided a regulating member between the working electrodes, thereby increasing the creepage distance from one working electrode to the surface of the other working electrode. This ensured a distance between the analyte (diffusion layer) near the working electrode, whose composition changes during electrolyte concentration measurement, and the other working electrode, preventing interference with the measurement and enabling the intended analyte electrolyte concentration to be detected at the working electrode (working electrode surface).

[0092] Example 2 <Configuration of Flow Channel> A description will be given of an analytical device P4 in Example 2. A top view of the analytical device P4 in Example 2 is shown in FIG.

[0093] The analytical device P4 according to the present invention in Example 2 has a flow path region surrounded by a flow path wall 401 formed of a hydrophobic resin provided within a porous substrate 400. It has a first flow path region 403 having a reference electrode 402 provided on the porous substrate 400, and flow path regions 407 and 408 that are not connected to the first flow path region 403. A working electrode 404a provided on the porous substrate 400 is present within the first flow path region 403. The working electrode 404a is provided within the first flow path region 403, and an electrode rod extends onto the flow path wall 401 from the reaction region that contacts the sample and measures the electrolyte concentration when measuring the electrolyte concentration of the sample. Also, outside the first flow path region 403, there is a working electrode 405a provided on the porous substrate 400, and a coating film 405b containing an ion-selective compound that covers at least a portion of the working electrode 405a (including the reaction region where the electrolyte concentration is measured). The working electrode 405a has an electrode rod extending from a reaction region provided in the flow channel region 407 onto the flow channel wall 401. Similarly, outside the first flow channel region 403, there are a working electrode 406a provided on the porous substrate 400 and a coating film 406b containing an ion-selective compound that covers at least a portion of the working electrode 406a (including the reaction region where the electrolyte concentration is measured). The working electrode 406a has an electrode rod extending from a reaction region provided in the flow channel region 408 onto the flow channel wall 401.

[0094] 11, the restricting member 409 is indicated by light ink, and the portion of the analytical device P4 covered by the restricting member 409 or the coating film 405b or 406b is indicated by a dashed line. The working electrode portion is indicated by the portion with a dotted pattern. In Example 1 and Comparative Example 1, the flow path wall was colored by light ink to distinguish it from the flow path region, but in FIG. 11, the flow path wall 401 is not colored to facilitate understanding.

[0095] The flow path pattern and the materials of the porous substrate and flow path walls in the analytical device P4 of this embodiment are the same as those in the first embodiment.

[0096] As in Example 1, the analytical device P4 may have (i) a first working electrode portion provided on the porous substrate 400 within the first flow path region 403. That is, the first working electrode portion may have a working electrode 404a (including a reaction region) as the first working electrode. The analytical device P4 may have a second working electrode portion provided on the porous substrate 400 outside the first flow path region 403. The second working electrode portion may have a working electrode 405a (including a reaction region) as the second working electrode and a coating film 405b covering at least a portion of the second working electrode (including the reaction region). The second working electrode portion may have a working electrode 406a (including a reaction region) as the second working electrode and a coating film 406b covering at least a portion of the second working electrode (including the reaction region). The analytical device P4 may also have flow path regions 407 and / or 408 as the second flow path region. The second flow path region 407 or 408 may have a second working electrode portion having a working electrode 405a or 406a and a covering membrane 405b or 406b.

[0097] Alternatively, the analytical device P4 may have (ii) a first working electrode portion provided on the porous substrate 400 outside the first flow path region 403. The first working electrode portion may include, for example, a working electrode 405a (including a reaction region) as the first working electrode and a coating film 405b covering at least a portion of the first working electrode (including the reaction region). The second working electrode portion may include a working electrode 406a (including a reaction region) as the second working electrode and a coating film 406b covering at least a portion of the second working electrode (including the reaction region). The analytical device P4 may also have flow path regions 407 and 408 as the second flow path region. The second flow path region 407 may include a first working electrode portion including the working electrode 405a and the coating film 405b, and the second flow path region 408 may include a second working electrode portion including the working electrode 406a and the coating film 406b.

[0098] In this embodiment, at least a portion of the first flow path region 403, at least a portion of the working electrode section where the working electrode 404a is present, at least a portion of the working electrode section where the working electrode 405a and coating film 405b are present, and at least a portion of the working electrode section where the working electrode 406a and coating film 406b are present are arranged within a distance L from one another. That is, as part of each working electrode section, the reaction regions of all of the working electrodes (404a, 405a, and 406a) and the areas where the coating films (405b and 406b) are present are arranged so that they all fall within the range of a circle (shown by a dashed line in the figure) with a diameter L. L is equal to or less than the diameter of the droplet d of the analyte to be introduced. In addition, the working electrode section where the working electrode 404a is present, the working electrode section where the working electrode 405a and coating film 405b are present, and the working electrode section where the working electrode 406a and coating film 406b are present are separated by a regulating member 409.

[0099] The region (the portion surrounded by the long two-dot chain line in the figure) including a circle with a diameter of L (the circle shown by the one-dot chain line) that includes at least a portion of the first flow path region 403, at least a portion of each of all of the working electrode portions, and at least a portion of the restricting member 409 is defined as the measurement introduction portion 410. The measurement introduction portion 410 is a portion into which a droplet d of the analyte to be analyzed is introduced when measuring the electrolyte concentration of the analyte to be analyzed.

[0100] <Electrode formulation> The shapes, arrangements, and materials of the reference electrode, ion crystal (411), and working electrode in the analytical device P4 of this example are the same as those in Example 1. A working electrode 405a capable of measuring the concentration of Na ions and a coating membrane 405b that is a Na ion selective membrane are arranged, a working electrode 406a capable of measuring the concentration of K ions and a coating membrane 406b that is a K ion selective membrane are arranged, and a working electrode 404a capable of measuring the concentration of Cl ions is arranged.

[0101] <Restriction Member> The restriction member 409 in Example 2 will be described. The restriction member 409 in this Example was arranged so as to cut off the contact points between the droplet d of the sample and a part of each working electrode (reaction region) during measurement, and the contact points between the droplet d and the first flow path region, and cover the remaining areas (the part of the working electrode excluding the reaction region, and the reference electrode 402).

[0102] As in Example 1, FIG. 12 is a schematic diagram showing a cross section of a portion of analytical device P4 and the sample droplet d when the sample droplet d is introduced into the measurement introduction portion 410. FIG. 12 shows a portion of the cross section of analytical device P4 taken along line CC' in FIG. 11 . Note that the pattern of the working electrode portion is not filled in in FIG. 12 to facilitate understanding. The width W1 of the regulating member in the proximity region (measurement introduction portion 410) where the working electrodes are closest to each other was set to 500 μm, and the height H2 of the regulating member 409 from the working electrode portion adjacent to the regulating member 409 was set to 75 μm.

[0103] In this example, the diffusion layer of NaCl has H3 = 532 μm, similar to Example 1. In addition, in this example, the diffusion layer of KCl has H3 = 606 μm, similar to Example 1. In order to prevent the working electrodes from being affected by changes in the concentrations of both K and Na ions, in this example, the creepage distance S is 650 μm, which is greater than H3 (= 606 μm).

[0104] In this example, similar to Example 1, the height H1 of the sample droplet is 2.44 mm, and the height H4 of the restricting member from the first flow path region 403 is 150 μm, which is shorter than the height H1 of the droplet. This confirms that electrical connection between the first working electrode portion and the second working electrode portion, and between each working electrode portion and the first flow path region, is not impeded during electrolyte concentration measurement.

[0105] That is, as in Example 1, the creepage distance can be appropriately controlled by forming walls between the multiple working electrodes using a restricting member, and the distance between the portion having the analyte concentration distribution near the working electrode where the components change during electrolyte concentration measurement and the other working electrodes can be maintained. This makes it possible to prevent interference with the measurement even when a miniaturized analytical device is used.

[0106] In this embodiment, the shape of the cut-out portion of the restricting member 409 corresponds to the shape of the working electrode portion, but the cut-out shape is not limited to this.

[0107] The width W1 of the restricting member in the proximity region where the working electrode portions are closest to each other and the height H2 of the restricting member from the working electrode adjacent to the restricting member are not limited to these values ​​as long as they satisfy the relationship W1 + 2H2 ≥ H3 relative to the thickness H3 of the diffusion layer 13, as in Example 1. Furthermore, the shape of the cutout area in the area where the first flow path region and the surface of the working electrode portion are electrically connected when a droplet of analyte is dropped is not limited to these values.

[0108] In addition, in this example, the shape of the regulating member was arranged so as to cover the working electrode and the reference electrode excluding the contact points with the sample droplets, but this is not restrictive as long as the regulating member is present in the vicinity of the working electrode portions and separates the working electrode portions from each other.

[0109] Although the flow path region of the present invention has been described as an example of a flow path region surrounded by flow path walls formed of a hydrophobic resin disposed inside a porous substrate, it may also be a flow path region in which a hydrophobic sheet such as PET is used as the substrate and its surface is made hydrophilic by plasma treatment, corona discharge treatment, or surface coating with a hydrophilic polymer. The hydrophilic polymer may be, for example, polyethylene glycol (PEG), EVAL (EVOH), poval (PVOH), or a polymer containing a phosphorylcholine group. A coating layer may also be formed by applying and drying a blended liquid consisting of hydrophilic inorganic fine particles, polymer fine particles dispersed in an aqueous medium, and a reactive organic fluorine compound. The hydrophilicity of the flow path region allows analytes to migrate. Furthermore, by providing a regulating member as in Example 2 on the flow path region so as to form a gap with the flow path region, capillary action due to the gap between the flow path region and the regulating member is also added, thereby accelerating analyte migration. Alternatively, a hydrophobic sheet may be used as the substrate and a flow path region made of a porous material may be provided on the surface of the sheet. The flow path region of the present invention can be any hydrophilic flow path region surrounded by hydrophobic flow path walls.

[0110] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0111] This application claims priority based on Japanese Patent Application No. 2024-065708, filed April 15, 2024, the entire contents of which are incorporated herein by reference.

[0112] 1, 201, 301, 401... Flow path wall 2, 302, 402... Reference electrode 3, 303, 403... First flow path region 4a, 5a, 6a, 205a, 206a, 304a, 305a, 306a, 404a, 405a, 406a... Working electrode 5b, 6b, 205b, 206b, 305b, 306b, 405b, 406b... Coating film 7, 8, 207, 208, 307, 308, 407, 408... Flow path region 9, 209, 409... Restricting member 10, 310, 410... Introduction portion during measurement

Claims

1. An analytical device having a hydrophilic or porous flow region surrounded by a hydrophobic flow wall provided inside or on a substrate, the analytical device having a first flow region having a reference electrode provided on the substrate, a first working electrode portion provided on the substrate within the first flow region or outside the first flow region, a second working electrode portion provided on the substrate outside the first flow region, a first working electrode present at the first working electrode portion, a second working electrode present at the second working electrode portion, and a regulating member separating the first working electrode portion and the second working electrode portion, the regulating member being a member that is not permeable by the analyte to be analyzed and having a height that does not separate the analyte.

2. The analytical device according to claim 1, comprising a second flow path region, (i) when the first working electrode portion is present within the first flow path region, the second flow path region also comprises the second working electrode portion, and the first flow path region and the second flow path region are separated from each other by the flow path wall, and (ii) when the first working electrode portion is present outside the first flow path region, comprising a plurality of second flow path regions, each of the plurality of second flow path regions comprising the first working electrode portion and the second working electrode portion, the first flow path region and the second flow path region being separated from each other by the flow path wall, and the plurality of second flow path regions being separated from each other by the flow path wall.

3. An analytical device as described in claim 1 or 2, wherein at least a portion of the first flow path region, at least a portion of the first working electrode portion, at least a portion of the second working electrode portion, and at least a portion of the regulating member are arranged to be within a circle having a diameter L, and L is equal to or smaller than the diameter of the droplet of the sample to be introduced.

4. The analytical device described in claim 3, wherein an area including a circle with a diameter of L that includes at least a portion of the first flow path region, at least a portion of the first working electrode portion, at least a portion of the second working electrode portion, and at least a portion of the regulating member is used as a measurement introduction portion for introducing the sample during measurement.

5. An analytical device according to any one of claims 1 to 4, wherein when the creeping distance between the first working electrode portion and the second working electrode portion adjacent to the regulating member is S, S is equal to or greater than the thickness of a layer in which a concentration distribution occurs near each of the first working electrode portion and the second working electrode portion adjacent to the regulating member during measurement.

6. The analytical device according to claim 5, wherein the creepage distance S is 532 μm or more.

7. An analytical device according to any one of claims 1 to 6, wherein the height of the regulating member is equal to or less than the height of the droplet of the sample to be introduced.

8. An analytical device according to any one of claims 1 to 7, wherein the height of the regulating member is 3.57 mm or less.

9. An analytical method for measuring the electrolyte concentration of a sample using an analytical device, wherein the analytical device has a hydrophilic or porous flow path region surrounded by a hydrophobic flow path wall provided inside or on a substrate, a first flow path region having a reference electrode provided on the substrate, a first working electrode portion provided on the substrate within the first flow path region or outside the first flow path region, a second working electrode portion provided on the substrate outside the first flow path region, a first working electrode present at the first working electrode portion, and a second working electrode present at the second working electrode portion, and a regulating member separating the first working electrode portion and the second working electrode portion, wherein the regulating member is a member that is impermeable to the sample and has a height that does not divide the sample, and the sample is supplied to a position where it simultaneously contacts the first working electrode portion, the second working electrode portion, and the regulating member.

10. The analytical method described in claim 9, wherein the regulating member is a member that separates the first working electrode portion from the second working electrode portion so that the first selected ion measured at the first working electrode portion and the second selected ion measured at the second working electrode portion do not mix.

11. The analytical method according to claim 9 or 10, wherein the measurement of the electrolyte concentration of the analyte is performed based on the potential difference between the reference electrode and the first working electrode or the second working electrode, and wherein (i) when the first working electrode portion is located within the first flow path region, the first working electrode portion and the second working electrode portion are connected by simultaneously contacting the analyte below the liquid surface of the analyte across the regulating member, and (ii) when the first working electrode portion is located outside the first flow path region, the first working electrode portion and the second working electrode portion are connected by simultaneously contacting the analyte below the liquid surface of the analyte across the regulating member, and further wherein at least one of the first working electrode portion and the second working electrode portion is connected to the first flow path region by simultaneously contacting the analyte with the first flow path region below the liquid surface of the analyte.

12. An analytical device having a hydrophilic or porous flow path region surrounded by a hydrophobic flow path wall provided inside or on a substrate, comprising: a first flow path region having a reference electrode provided on the substrate; a first working electrode portion provided on the substrate within the first flow path region or outside the first flow path region; a second working electrode portion provided on the substrate outside the first flow path region; a first working electrode present at the first working electrode portion, and optionally a coating film covering at least a portion of the first working electrode and containing a compound having ion selectivity; a second working electrode present at the second working electrode portion, and optionally a coating film covering at least a portion of the second working electrode and containing a compound having ion selectivity; at least one of a coating film covering at least a portion of the first working electrode present at the first working electrode portion and a coating film covering at least a portion of the second working electrode present at the second working electrode portion; and a restricting member separating the first working electrode portion and the second working electrode portion. An analytical device, wherein the restricting member is a member that is not permeable to a specimen to be analyzed and has a height that does not divide the specimen.

13. An analytical method for measuring the electrolyte concentration of a sample using an analytical device, wherein the analytical device has a hydrophilic or porous flow region surrounded by a hydrophobic flow wall provided inside or on a substrate, a first flow region having a reference electrode provided on the substrate, a first working electrode portion provided on the substrate within the first flow region or outside the first flow region, a second working electrode portion provided on the substrate outside the first flow region, a first working electrode present at the first working electrode portion, and a coating film containing an ion-selective compound covering at least a portion of the first working electrode, and a second working electrode present at the second working electrode portion, and a coating film containing an ion-selective compound covering at least a portion of the second working electrode, and at least one of a coating film covering at least a portion of the first working electrode present at the first working electrode portion and a coating film covering at least a portion of the second working electrode present at the second working electrode portion, an analytical method comprising: a restricting member separating the first working electrode portion and the second working electrode portion; the restricting member being a member that the specimen cannot penetrate and having a height that does not divide the specimen; and the specimen being supplied to a position where the specimen is in contact with the first working electrode portion, the second working electrode portion, and the restricting member simultaneously.

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