Measurement System and Sensor Unit

Abstract

A technique is provided that enables the Na / K ratio to be measured simply and quickly. [Solution] The sensor unit 10, which comes into contact with the test liquid, has at least a sodium ion electrode 15a that selectively responds to sodium ions in the test liquid, a potassium ion electrode 15b that selectively responds to potassium ions in the test liquid, and a chloride ion electrode 15c that selectively responds to chloride ions in the test liquid and is used as a counter electrode to the sodium ion electrode 15a and the potassium ion electrode 15b, and is configured so that the potential difference between the sodium ion electrode 15a and the chloride ion electrode 15c and the potential difference between the potassium ion electrode 15b and the chloride ion electrode 15c when each electrode is in contact with the test liquid can be measured by a measuring device unit 20 to which the sensor unit 10 is attached.

Description

[Technical Field]

[0001] The present disclosure relates to a measurement system and a sensor unit. [Background technology]

[0002] Since excessive salt (sodium) intake and insufficient potassium intake, which is found in vegetables and fruits, both increase the risk of high blood pressure and cardiovascular disease, the significance of measuring the sodium ion to potassium ion concentration ratio (hereinafter referred to as the "Na / K ratio") in urine as an indicator of the balance between reducing salt and increasing potassium is attracting attention.

[0003] It is known that the Na / K ratio can be measured using, for example, an electrochemical sensor equipped with two types of ion-selective electrodes (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-95675 Summary of the Invention [Problem to be solved by the invention]

[0005] It is preferable for the health management of a subject that the measurement of the urinary Na / K ratio can be performed routinely at home, etc. However, conventional methods for measuring the Na / K ratio require complicated procedures for conditioning the sensor (e.g., zero-point calibration), and therefore are not necessarily suitable for routine health management applications.

[0006] The present disclosure provides a technique that enables the Na / K ratio to be measured simply and quickly, making it suitable for routine health care applications. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a sensor portion that comes into contact with the test liquid; a measuring device unit to which the sensor unit is attached, The sensor unit a sodium ion electrode that selectively responds to sodium ions in the test solution; a potassium ion electrode that selectively responds to potassium ions in the test solution; a chloride ion electrode that selectively responds to chloride ions in the test solution and is used as a counter electrode to the sodium ion electrode and the potassium ion electrode; a wiring section that electrically connects the sodium ion electrode, the potassium ion electrode, and the chloride ion electrode to the measuring device section, The measuring device is configured to calculate the concentration of sodium ions in the test liquid from the potential difference of the sodium ion electrode when the chloride ion sensor is used as a counter electrode, using a predetermined proportional relational expression that represents the correlation between the concentrations of sodium ions and chloride ions, and to calculate the concentration of potassium ions in the test liquid from the potential difference of the potassium ion electrode when the chloride ion sensor is used as a counter electrode, and to specify the concentration ratio of sodium ions to potassium ions in the test liquid from the respective calculation results. A measurement system is provided. [Effects of the Invention]

[0008] According to the present disclosure, the Na / K ratio in a test solution can be measured simply and quickly, making it suitable for use in, for example, daily health management. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view schematically illustrating a configuration example of a measurement system according to an embodiment of the present disclosure. [Figure 2] 1 is an exploded perspective view showing a configuration example of a sensor section (sensor unit) that constitutes a measurement system according to an embodiment of the present disclosure. [Figure 3] 3 is a plan view showing an example of the main configuration of the sensor unit shown in FIG. 2. FIG. [Figure 4] FIG. 1 is an explanatory diagram showing a specific example of the relationship between sodium ion concentration and chloride ion concentration in a urine sample. [Figure 5] FIG. 10 is an explanatory diagram showing a specific example of correlation between measurement results obtained by a measurement system according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0011] (1) Overview of the measurement system First, an overview of the measurement system according to this embodiment will be described. The measurement system according to this embodiment is used to measure the Na / K ratio in a test liquid.

[0012] An example of the test liquid is urine excreted from a living human being. However, this is not necessarily limited to this. For example, the living body may be an animal such as a pet, and urine excreted from the animal may be used as the test liquid. Furthermore, the method can be applied to liquids other than urine as long as the measurement of the Na / K ratio is required. In the following explanation, the case where urine excreted from a human being is used as the test liquid will be taken as an example.

[0013] It is preferable that the measurement of the Na / K ratio in urine excreted from humans can be carried out on a daily basis in an ordinary household, etc., because the Na / K ratio in urine is a useful index for health management.

[0014] For this reason, the measurement system according to this embodiment has the following characteristic configuration so as to be suitable for daily health management applications.

[0015] (2) Measurement system configuration example Fig. 1 is a perspective view schematically showing an example of the configuration of a measurement system according to this embodiment. Fig. 2 is an exploded perspective view showing an example of the configuration of a sensor section (sensor unit) that constitutes the measurement system according to this embodiment. Fig. 3 is a plan view showing an example of the configuration of the main parts of the sensor section shown in Fig. 2.

[0016] (Overall composition) As shown in FIG. 1, the measurement system according to this embodiment is broadly composed of a sensor unit 10 that is used by bringing it into contact with the test liquid, i.e., urine, and a measurement device unit 20 to which the sensor unit 10 is attached.

[0017] The sensor section 10 functions as a sensor unit for measuring the Na / K ratio in urine, and is configured to be detachable from the measurement device section 20. This allows the sensor section 10 to be replaced after each use (i.e., it can be used as a disposable item).

[0018] Because the sensor unit 10 is detachable, the measurement unit 20 functions as one of the external devices for the sensor unit 10, and is formed in a size and shape that can be held in the hand of a user of the measurement system (for example, a person who excretes urine, which is the test liquid). This allows the user to hold the measurement unit 20 and bring the tip of the sensor unit 10 attached to the measurement unit 20 into contact with urine that they have excreted.

[0019] Each of these components will be described in more detail below.

[0020] (Sensor configuration) The sensor section 10 is formed in a strip shape, with one end in the longitudinal direction of the strip functioning as an attachment end to the measuring device section 20 and the other end functioning as an end that comes into contact with urine.

[0021] As shown in FIG. 2, the sensor section 10 is configured by laminating a plurality of layers of films 12 to 14 on a substrate 11.

[0022] The substrate 11 is formed from a water-resistant material, specifically a resin material, ceramic, glass, paper, or the like. A plurality of electrodes 15 are arranged on the surface of the substrate 11, on the side that comes into contact with urine. Details of each electrode 15 will be described later. Also, on the surface of the substrate 11, on the side that is attached to the measuring device 20, connection terminals 16 corresponding to each electrode 15 are arranged. Furthermore, the substrate 11 is formed with wiring sections (not shown) that connect each electrode 15 to each connection terminal 16. As a result, when the sensor section 10 is attached to the measuring device 20, each electrode 15 is electrically connected to the measuring device.

[0023] Like the substrate 11, the films 12 to 14 on the substrate 11 are also made of a water-resistant material. Of the films 12 to 14, the first film 12, which is located closest to the substrate 11, functions as, for example, double-sided tape and has partially removed portions 12a at locations corresponding to the electrodes 15. By attaching a second film 13, which functions as, for example, a hydrophilic film, to the first film 12 via the first film 12, the removed portions 12a form a urine flow path that communicates with the end surface of the film. The second film 13 has slits 13a that function as air escape routes, allowing urine to fill the flow path formed by the removed portions 12a. A third film 14, which functions as, for example, single-sided tape, is attached to the second film 13 to cover the slits 13a.

[0024] In this laminated structure of the substrate 11 and each of the films 12 to 14, the edge position of each of the films 12 to 14 on the side of the end that is attached to the measuring device part 20 is set so that it does not cover the connection terminals 16 on the substrate 11.

[0025] Furthermore, the edge positions of at least second film 13 and third film 14 on the side of the end that comes into contact with urine are set to protrude relative to the edge position of substrate 11. This prevents removal unit 12a from absorbing urine from the flow path even when the flow rate of urine that comes into contact with sensor unit 10 is high, making it possible to stably guide and retain urine within the flow path.

[0026] (Configuration of each electrode) The plurality of electrodes 15 arranged on the substrate 11 of the sensor unit 10 each function as an ion-selective electrode, and as shown in FIG. 3, all are located within the region of the removed portion 12a of the first film 12. The plurality of electrodes 15 within the region of the removed portion 12a include a sodium ion electrode 15a, a potassium ion electrode 15b, and a chloride ion electrode 15c. In other words, the sensor unit 10 is configured with at least three electrodes: the sodium ion electrode 15a, the potassium ion electrode 15b, and the chloride ion electrode 15c. The arrangement of the electrodes 15 is not limited to a particular embodiment as long as they are located within the region of the removed portion 12a.

[0027] The sodium ion electrode 15a is an electrode that selectively responds to sodium ions in the test liquid (specifically, urine that comes into contact with the electrode 15) and is configured to be able to detect the sodium ion concentration in the test liquid with high accuracy. The potassium ion electrode 15b is an electrode that selectively responds to potassium ions in the sample liquid, and is configured to be able to detect the potassium ion concentration in the sample liquid with high accuracy. The chloride ion electrode 15c is an electrode that selectively responds to chloride ions in the test liquid and is configured to detect the chloride ion concentration in the test liquid with high accuracy. The chloride ion electrode 15c is used as a counter electrode to the sodium ion electrode 15a and the potassium ion electrode 15b.

[0028] In this embodiment, both the sodium ion electrode 15a and the potassium ion electrode 15b are solid-contact ion selective electrodes. A solid-contact ion selective electrode selectively detects specific ions in a sample and measures their concentrations. Unlike conventional ion-selective electrodes, which require an internal solution and a reference electrode, this electrode has a significant advantage in that it replaces these elements with solid materials, eliminating the need for an internal solution and making it easier to handle. A known example of such a solid-contact ion-selective electrode is a coated wire-type ion-selective electrode, which is a wire coated with an ion-sensitive membrane and used as an electrode.

[0029] Specifically, the sodium ion electrode 15a can be formed as a solid-contact liquid membrane ion-selective electrode by using, for example, bis(12-crown-4) (Dojindo Laboratories) as the ionophore, and the potassium ion electrode 15b can be formed as a solid-contact liquid membrane ion-selective electrode by using, for example, bis(benzo-15-crown-5) (Dojindo Laboratories) as the ionophore. The chloride ion electrode 15c can function as a chloride ion sensor by forming, for example, a silver / silver chloride paste electrode, which is a solid electrode, and bringing it into contact with urine as is. It should be noted that the examples given here are merely specific examples and are not necessarily limited to these.

[0030] (Configuration of measuring instrument) 1, the measuring unit 20 has an insertion opening (slot) 21 for attaching the sensor unit 10. When the sensor unit 10 is attached to the insertion opening 21, the measuring unit 20 electrically connects to each electrode 15 of the sensor unit 10 and measures the Na / K ratio in urine that comes into contact with each electrode 15. In other words, the measuring unit 20 has the function of performing electrical signal processing, information processing, etc., required for measuring the Na / K ratio in urine.

[0031] Specifically, the measuring unit 20 has a function of calculating the concentration of sodium ions in urine from the potential difference of the sodium ion electrode 15a when the chloride ion electrode 15c is used as the counter electrode. The measuring unit 20 also has a function of calculating the concentration of potassium ions in urine from the potential difference of the potassium ion electrode 15b when the chloride ion electrode 15c is used as the counter electrode. The measuring unit 20 also has a function of determining the Na / K ratio in urine from the respective calculation results (i.e., the calculation results of the sodium ion and potassium ion concentrations). The function of calculating the sodium ion and potassium ion concentrations in the measuring unit 20 utilizes a predetermined proportional relational expression that expresses the correlation between the concentrations of sodium ions and chloride ions. The predetermined proportional relational expression will be described in detail below.

[0032] Additionally, the measuring unit 20 may have a function of notifying at least one of the operation timings of the start and end of measurement of the urinary Na / K ratio, for example, by display output using an LED (Light Emitting Diode) panel or sound output using a buzzer. Furthermore, the measuring unit 20 may have a short-range wireless communication function for connecting to an information terminal device, such as a smartphone, and transmitting measurement data.

[0033] To operate these functions, the measuring unit 20 preferably includes a power supply unit (not shown). This is because including a power supply unit ensures sufficient flexibility in the location of use of the measuring unit 20, etc. Examples of the power supply unit include, but are not limited to, a secondary battery, and any other power supply unit configured using known technology may be used as long as it is capable of supplying power.

[0034] In this way, the measuring device section 20 is configured so that it is possible to measure the Na / K ratio in urine with the sensor section 10 attached.

[0035] (3) Example of processing operation in the measurement system Next, an example of the processing operation in the measurement system configured as above will be specifically described.

[0036] When measuring the Na / K ratio in urine using the measurement system configured as described above, first, an unused sensor unit 10 is attached to the insertion port 21 of the measurement unit 20. Once the sensor unit 10 is attached, the measurement unit 20 automatically starts up.

[0037] After starting up the measuring unit 20, the user of the measuring system (the person urinating) holds the measuring unit 20 in their hand and brings their own urine into contact with the tip (i.e., the end that comes into contact with urine) of the sensor unit 10 attached to the measuring unit 20. As a result, in the sensor unit 10, the urine fills the flow path formed by the removal unit 12a by capillary action, using the slit 13a that functions as an escape route for air. At this time, if the edge positions of the second film 13 and the third film 14 that make up the sensor unit 10 protrude, even if the flow rate of the urine coming into contact with the sensor unit 10 is high, the removal unit 12a will be prevented from suctioning the urine from the flow path, and the urine can be stably guided and held in the flow path.

[0038] When urine fills the flow path defined by removal unit 12a, the urine comes into contact with each of electrodes 15 arranged within the area of ​​removal unit 12a. At this time, measurement unit 20 detects the fluctuation in measurement voltage when urine comes into contact with each of electrodes 15, and automatically starts measurement, and ends the measurement after a predetermined time (e.g., 30 seconds) has elapsed. The timing of the start or end of measurement may be notified by a display output, sound output, etc.

[0039] In this way, the measurement of the urinary Na / K ratio by the measuring device unit 20 starts when the urine comes into contact with each electrode 15, and ends when a predetermined time has elapsed since then. However, this is not necessarily limited to this, and it is sufficient if the processing operation for measuring the Na / K ratio is performed at at least any measurement timing between the attachment of the sensor unit 10 to the measuring device unit 20 (i.e., the activation of the measuring device unit 20) and the elapse of a predetermined time.

[0040] Specifically, the measurement unit 20 measures the urinary Na / K ratio in the following manner.

[0041] Urine, which is the subject of measurement, contains sodium ions and chloride ions, and it is known that there is a high correlation between the sodium ion concentration and the chloride ion concentration. 4 is an explanatory diagram showing a specific example of the relationship between sodium ion concentration and chloride ion concentration in urine samples. The diagram shows the results of measuring the sodium ion concentration and chloride ion concentration of several urine samples using a known automatic biochemical analyzer (e.g., JCA-BM6050 manufactured by JEOL Ltd.). In the diagram, the horizontal axis represents sodium ion concentration, and the vertical axis represents chloride ion concentration. According to the measurement results shown in Figure 4, the relationship between the sodium ion concentration and chloride ion concentration in the urine sample was determined by the linear regression equation y = 0.972x, R 2 =0.976, which shows a strong proportional relationship.

[0042] Based on this, the measuring unit 20 uses a predetermined proportional relational expression that expresses the correlation between the concentrations of sodium ions and chloride ions to create a calibration curve for calculating the sodium ion concentration and potassium ion concentration when the chloride ion electrode 15c is used as the counter electrode, and calculates the Na / K ratio. One example of the predetermined proportional relational expression is the following equation (1). In equation (1), [Na] is the sodium ion concentration, [Cl] is the chloride ion concentration, and d is a constant.

[0043]

number

[0044] To explain in more detail, the measuring device section 20 calculates the Na / K ratio by using the above-mentioned formula (1), which is a predetermined proportional relational expression, and by carrying out the following arithmetic processing, for example.

[0045] The potential difference applied by the ion selective electrode for ion species M is E M (V vs. chloride ion electrode) and E' M (V vs. commercially available reference electrode), the above formula (1) holds. Therefore, assuming a Nernst response, the following formulas (2) and (3) hold for sodium ions. In formulas (2) and (3), a to c, and e are all constants.

[0046]

number

[0047]

number

[0048] On the other hand, the potential difference E Na The following relationship (4) holds true for

[0049]

number

[0050] Therefore, by rearranging these equations (1) to (4), the following equation (5) is obtained, which allows the sodium ion concentration in urine to be calculated from the potential difference at the sodium ion electrode 15a when the chloride ion electrode 15c is used as the counter electrode.

[0051]

number

[0052] Similarly, the following equations (6) and (7) hold true for potassium ions: In equation (6), f and g are both constants.

[0053]

number

[0054]

number

[0055] Therefore, by rearranging these equations (1), (3), (6) to (7), the following equation (8) is obtained, which allows the potassium ion concentration in urine to be calculated from the potential difference at potassium ion electrode 15b when chloride ion electrode 15c is used as the counter electrode.

[0056]

number

[0057] As described above, the measuring device 20 can calculate the sodium ion concentration from the potential difference of the sodium ion electrode 15a (the counter electrode is the chloride ion electrode 15c) and the potassium ion concentration from the potential difference of the potassium ion electrode 15b (the counter electrode is the chloride ion electrode 15c) while utilizing a predetermined proportional relational expression that is previously determined from the correlation between the sodium ion concentration and the chloride ion concentration.

[0058] After calculating the sodium ion concentration and potassium ion concentration, the measuring unit 20 determines the Na / K ratio in urine by calculating the ratio between the respective calculation results. In this way, the measuring unit 20 makes it possible to measure the Na / K ratio in urine.

[0059] The measurement results of the Na / K ratio by the measuring device unit 20 are transmitted as measurement data to an information terminal device, such as a smartphone, using, for example, a short-range wireless communication function. This allows the system user to understand the measurement results of the urinary Na / K ratio by referring to the measurement data output results on the information terminal device, making it possible to realize useful information for health management of the person being measured (the person excreting urine).

[0060] It has been confirmed that the measurement results of the urinary Na / K ratio obtained by the procedure described above in this embodiment correlate with the measurement results of the Na / K ratio obtained using a known automatic biochemical analyzer (for example, JCA-BM6050 manufactured by JEOL Ltd.). 5 is an explanatory diagram showing a specific example of the correlation between the measurement results obtained by the measurement system according to this embodiment. The diagram shows the relationship between the measurement results of the urinary Na / K ratio obtained by the procedure described in this embodiment and the measurement results of the urinary Na / K ratio obtained using the above-mentioned automatic biochemical analyzer for several urine samples. In the diagram, the horizontal axis represents the Na / K ratio value obtained using the above-mentioned automatic biochemical analyzer, and the vertical axis represents the Na / K ratio value obtained using this embodiment. According to the relationship shown in Figure 5, the linear regression equation for each measurement result is y=1.218x-0.464, R 2=0.736. In other words, it has been confirmed that the measurement results of the Na / K ratio obtained in this embodiment show a good correlation with the measurement results of the Na / K ratio obtained by the above-mentioned automatic biochemical analyzer.

[0061] (4) Effects of this embodiment The measurement system according to the present embodiment described above provides one or more of the following advantageous effects.

[0062] (a) According to this embodiment, the electrodes 15 that come into contact with urine (the test liquid) include a sodium ion electrode 15a, a potassium ion electrode 15b, and a chloride ion electrode 15c, and the measuring device 20 electrically connected to these electrodes determines the Na / K ratio in urine using a predetermined proportional relationship that expresses the correlation between the concentrations of sodium ions and chloride ions. That is, in this embodiment, the sodium ion electrode 15a and the potassium ion electrode 15b are used as working electrodes, while the chloride ion electrode 15c is used as a counter electrode, making it possible to determine the Na / K ratio using the predetermined proportional relationship described above.

[0063] As described above, in this embodiment, the Na / K ratio is measured using a predetermined proportional relational expression, which eliminates the need for complicated procedures for conditioning the sensor each time a measurement is performed (e.g., zero-point calibration), and allows the Na / K ratio to be measured simply and quickly. Moreover, the use of the predetermined proportional relational expression is achieved by using the chloride ion electrode 15c as the counter electrode, which minimizes the complexity of the sensor configuration, making this embodiment also suitable for simply and quickly measuring the Na / K ratio.

[0064] In other words, according to this embodiment, the Na / K ratio can be measured simply and quickly, so that the Na / K ratio can be easily measured on a daily basis in the subject's home, etc., making it very suitable for use in the subject's daily health management.

[0065] (b) According to this embodiment, both the sodium ion electrode 15a and the potassium ion electrode 15b are solid-contact ion-selective electrodes. Therefore, unlike conventional ion-selective electrodes that require an internal solution and a reference electrode, the elimination of the internal solution and the like makes it easy to handle. In addition, since it can be manufactured compactly, it is highly portable.

[0066] That is, according to this embodiment, each electrode 15 is a solid-contact ion-selective electrode, which allows for easy handling and excellent portability, etc. Therefore, it is very suitable for easily and quickly measuring the Na / K ratio, and is even more suitable for daily health management of the subject.

[0067] (c) According to this embodiment, the sensor unit 10 is configured to be detachable from the measurement unit 20. The detachable sensor unit 10 is configured as a disposable item. Therefore, this embodiment is extremely convenient for the subject whose Na / K ratio is being measured, and is even more suitable for daily health management of the subject.

[0068] (d) According to this embodiment, the processing operation for measuring the Na / K ratio is performed at least at any measurement timing between the attachment of sensor unit 10 to measurement unit 20 and the lapse of a predetermined time. In other words, measurement starts automatically when sensor unit 10 is attached, and ends automatically when the predetermined time has elapsed. Therefore, according to this embodiment, the person undergoing measurement of the Na / K ratio does not need to perform any complicated operations on measurement unit 20, which is extremely suitable for measuring the Na / K ratio simply and quickly, and is even more suitable for use in the daily health management of the person being measured.

[0069] (5) Modifications, etc. Although the embodiments of the present disclosure have been specifically described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0070] For example, in the above-described embodiment, the test liquid is urine excreted from a human being, but this is not necessarily limited to this, and the same can be applied as in the above-described embodiment when measuring the Na / K ratio of other types of test liquid.

[0071] Furthermore, for example, in the above-described embodiment, the sensor section 10 is configured as a laminated structure of a substrate 11 and each film 12 to 14, but this is not necessarily limited to this, and other configurations (for example, a non-laminated structure) may also be used.

[0072] Furthermore, for example, in the above-described embodiment, the specific procedure for measuring the Na / K ratio is exemplified as a case where the measuring device unit 20 uses equations (1) to (8), but this is not necessarily limited to this, and the Na / K ratio may be calculated using other calculation equations as long as they are preset. [Explanation of symbols]

[0073] 10...sensor portion, 11...substrate, 12...first film, 12a...removal portion, 13...second film, 13a...slit, 14...third film, 15...electrodes, 15a...sodium ion electrode, 15b...potassium ion electrode, 15c...chloride ion electrode, 16...connection terminal, 20...measuring device portion, 21...insertion port

Claims

1. a sensor portion that comes into contact with the test liquid; a measuring device unit to which the sensor unit is attached, The sensor unit a sodium ion electrode that selectively responds to sodium ions in the test solution; a potassium ion electrode that selectively responds to potassium ions in the test solution; a chloride ion electrode that selectively responds to chloride ions in the test solution and is used as a counter electrode to the sodium ion electrode and the potassium ion electrode; a wiring section that electrically connects the sodium ion electrode, the potassium ion electrode, and the chloride ion electrode to the measuring device section, The measuring device is configured to calculate the concentration of sodium ions in the test liquid from the potential difference of the sodium ion electrode when the chloride ion electrode is used as a counter electrode, using a predetermined proportional relational expression that represents the correlation between the concentrations of sodium ions and chloride ions, calculate the concentration of potassium ions in the test liquid from the potential difference of the potassium ion electrode when the chloride ion electrode is used as a counter electrode, and the chloride ion concentration obtained based on the proportional relational expression, and to specify the concentration ratio of sodium ions to potassium ions in the test liquid from the respective calculation results. Measurement system.

2. The sodium ion electrode and the potassium ion electrode are both solid contact type ion selective electrodes. The measurement system of claim 1 .

3. The sensor unit is configured to be detachable from the measuring unit. The measurement system of claim 2 .

4. The sensor unit is configured as a disposable item. The measurement system of claim 3 .

5. The test liquid is urine excreted from a living body. The measurement system of claim 4 .

6. The measuring unit is configured to measure the potential difference of the sodium ion electrode and the potential difference of the potassium ion electrode at least at any measurement timing during a period from when the sensor unit is attached to the measuring unit until a predetermined time has elapsed.

6. A measurement system according to any one of claims 1 to 5.

7. A substrate; a plurality of electrodes disposed on the substrate and in contact with the test liquid; a wiring portion that electrically connects the plurality of electrodes to an external device, The plurality of electrodes a sodium ion electrode that selectively responds to sodium ions in the test solution; a potassium ion electrode that selectively responds to potassium ions in the test solution; a chloride ion electrode that selectively responds to chloride ions in the test solution and is used as a counter electrode to the sodium ion electrode and the potassium ion electrode; The potential difference between the sodium ion electrode and the chloride ion electrode and the potential difference between the potassium ion electrode and the chloride ion electrode when the plurality of electrodes are in contact with the test liquid can be measured by the external device; The external device is configured to calculate the concentration of sodium ions in the test liquid from the potential difference between the sodium ion electrode and the chloride ion electrode using a predetermined proportional relational expression that expresses the correlation between the concentrations of sodium ions and chloride ions, and to calculate the concentration of potassium ions in the test liquid from the potential difference between the potassium ion electrode and the chloride ion electrode and the concentration of chloride ions obtained based on the proportional relational expression, and to specify the concentration ratio of sodium ions to potassium ions in the test liquid from the respective calculation results. Sensor unit.

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