Oxygen concentration measuring device and substrate concentration measuring device

Abstract

To provide an oxygen concentration measuring apparatus capable of employing a sensor in a favorable state for a long period and efficiently performing measurement by preventing deterioration in a polarographic oxygen concentration measuring sensor, or a substrate concentration measuring apparatus applying the oxygen concentration measuring apparatus.SOLUTION: An oxygen concentration measuring apparatus equipped with a polarographic oxygen concentration measuring sensor or equipped with the polarographic oxygen concentration measuring sensor and a substrate concentration sensor combining enzyme reactions, or a substrate concentration measuring apparatus, in a time zone in which the apparatus is not used for the concentration measurement of a measuring object material, de-energizes, while constantly maintaining a temperature of the sensor. Further, the apparatus applies a voltage of -0.9 to -0.6 V to the sensor again at a time being retrospective by a prescribed time from a measurement start desired time preset by the player.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a technique for an oxygen concentration measuring device using a polarographic oxygen concentration measuring sensor, and a technique for a substrate concentration measuring device combining a polarographic oxygen concentration measuring sensor with an enzyme reaction. [Background technology]

[0002] The technology of measuring the amount of oxygen passing through an oxygen-permeable membrane using an oxygen concentration measurement sensor is used in a wide variety of applications, including fermentation process control, environmental measurement for water quality, and measurement in the medical field. In addition, when an enzyme related to the increase or decrease of oxygen is placed as an immobilized enzyme layer on the surface of the oxygen-permeable membrane of the oxygen concentration measurement sensor, the concentration of a substance that can be a substrate for the enzyme can be measured, and therefore the sensor is used in various industries as an enzyme sensor.

[0003] Oxygen concentration measuring sensors can be classified according to the principle of use. There are polarographic, galvanic cell, and concentration cell types, and they are used according to the purpose. Of these, polarographic types have a sensing electrode that serves as a cathode and a counter electrode that serves as an anode, and an aqueous solution of an alkali metal halide salt as an electrolyte solution, inside an electrode housing in which a part of the wall that serves as the detection section is made of an oxygen-permeable membrane. When a specific potential is applied to the sensing electrode, the current that flows according to the amount of oxygen that permeates the oxygen-permeable membrane is measured to determine the partial pressure of oxygen in a gas or liquid.

[0004] Polarographic oxygen concentration sensors have a drawback due to their operating principle: they deteriorate simply by being in standby, regardless of whether they are in a measurement state or not. When a polarographic oxygen concentration sensor is placed in an environment where oxygen is present while it is functioning normally (around -0.9 to -0.6 V), oxygen is consumed on the surface of the sensing electrode (cathode), while the halide ions in the electrolyte solution on the counter electrode (anode) become insoluble silver halide. The reaction is as shown in the following equations (1) and (2).

[0005] O2+2H2O+4e - →4OH - …(1) 4Ag+4X - →4AgX+4e - …(2)

[0006] Figure 7 shows an image of the sensing electrode of a polarographic oxygen concentration sensor and its surroundings. Figure 7(a) shows a typical example of the electrode of a polarographic oxygen concentration sensor before use. The pH of the electrolyte solution gradually increases with the amount of current passed through it, while the concentration of halide ions decreases (hereinafter, this phenomenon will be referred to as "deterioration of the electrolyte solution"). When the electrolyte solution deteriorates, the response speed of the polarographic oxygen concentration sensor decreases and the voltage range in which it functions normally narrows, making it an unstable sensor. In addition to the deterioration of the electrolyte solution, there are other sensor deteriorations caused by current passing through it.

[0007] 7(b) and (c), when the amount of current increases, inorganic or organic matter may accumulate on the sensing electrode 701 or on the resin (embedding resin) 702 that embeds the sensing electrode 701, which may slow down the response speed of the sensor or cause an abnormal electrochemical reaction. When this deterioration occurs, the sensor will eventually be unable to measure the oxygen concentration accurately, and the sensor will have to be replaced.

[0008] A deteriorated polarographic oxygen concentration measurement sensor can be restored to a normal state by disassembling the sensor, removing the deposits on the surface of the sensing electrode, and replacing the deteriorated electrolyte solution with a normal electrolyte solution. However, this task requires skill and is not something that a user can easily do, so in many cases the sensor is returned to the manufacturer, who then carries out the restoration. Since it takes a certain number of days for the regenerated sensor to arrive at the user, the user needs to have several normal sensors on hand as spares.

[0009] In addition, sensors cannot be regenerated indefinitely. The shape of the sensing electrode and its surroundings has a significant effect on the electrode performance, so it is common to perform precise and expensive processing to ensure good performance (see Patent Document 1 below, etc.).

[0010] However, the removal (polishing) of deposits on the sensing electrode and around the sensing electrode during regeneration can sometimes exceed the allowable range of dimensional accuracy. As a result, it often becomes unusable after a few regenerations, and the sensor body must be replaced with a new one. Furthermore, in recent years, sensors have come to be used more frequently for medical purposes, and the issue of thorough infection control for workers performing regeneration has become a major problem. For these reasons, both users and manufacturers have been looking for technology that would enable polarographic oxygen concentration measurement sensors and enzyme sensors that use them to be used for long periods of time in good condition and reduce the frequency of sensor replacement. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 11-183424 Summary of the Invention [Problem to be solved by the invention]

[0012] In order to prevent the above-mentioned polarographic oxygen concentration measuring sensor from deteriorating, it is necessary to make the integrated current flow during the period when the sensor is not used for measuring the concentration of the object to be measured as small as possible.

[0013] Figure 8 shows the current-voltage curve of a typical polarographic oxygen concentration sensor. Methods for minimizing the accumulated current flow during periods when the sensor is not being used to measure the concentration of the object being measured include (1) lowering the environmental temperature around the sensor, (2) cutting off the supply of oxygen, and (3) canceling the current flow, as shown in Figure 8.

[0014] However, the method of lowering the environmental temperature around the sensor requires reheating to the specified temperature before measurement, and has the drawback of taking a very long time to reach and stabilize at the specified temperature. In addition, cooling and heating means must be installed, making it difficult to create a cheap and small device. Methods for cutting off the supply of oxygen require replacing the area near the oxygen-permeable membrane with a gas that does not contain oxygen, attaching a molded part made of an oxygen-impermeable material to the oxygen-permeable membrane, or sealing the area near the oxygen-permeable membrane and using an oxygen scavenger, and these tend to require expensive devices that require precise machining.

[0015] Another method is to fill the area near the oxygen permeable membrane with an aqueous sodium sulfite solution, but this method is difficult to use in sensors that incorporate enzymes, as the effect on the enzyme cannot be ignored. Furthermore, the method of removing the current may not be able to provide accurate measurements depending on how the current is applied again. This is thought to be because once the current is removed, the electrochemical equilibrium is lost in the small areas around the sensing electrode and counter electrode, and it takes time to reach a steady state.

[0016] Due to these issues, there has not previously been an oxygen concentration measuring device or substrate concentration measuring device that is suitable for practical use, that prevents deterioration of polarographic oxygen concentration measuring sensors or enzyme sensors based on polarographic oxygen concentration measuring sensors, reduces the frequency of replacement, and enables timely measurements.

[0017] The present invention aims to solve the above problems and provide an oxygen concentration measuring device or substrate concentration measuring device that prevents deterioration of a polarographic oxygen concentration measuring sensor or an enzyme sensor that uses the same, thereby enabling the sensor to be used in good condition for a long period of time and capable of timely and efficient measurement. [Means for solving the problem]

[0018] In the present invention, "removing the current" does not necessarily mean that the voltage applied to the polarographic oxygen concentration sensor is set to 0V. As shown in FIG. 8, the relationship between the voltage applied to the polarographic oxygen concentration sensor and the amount of current flowing is not proportional. At voltages greater than about -0.2V (close to 0V), there is a region in which no current flows even if the voltage is not 0V. Therefore, in the present invention, as long as no current flows, the "no current state" is defined even if the voltage is not 0V. Furthermore, "removing the current" is defined as changing the state in which current was flowing through the sensor to the aforementioned "no current state." Note that the voltage region in which no current flows through the polarographic oxygen concentration sensor even when voltage is applied (region A in FIG. 8) may vary slightly depending on the material and shape of the sensor, environmental conditions, individual differences, etc.

[0019] The invention described in claim 1 is an oxygen concentration measuring device having a polarographic oxygen concentration measuring sensor, a thermostatic device capable of maintaining the polarographic oxygen concentration measuring sensor at a constant temperature, a power supply unit connected to the polarographic oxygen concentration measuring sensor, a control unit for controlling a voltage applied to the polarographic oxygen concentration measuring sensor, a measuring unit for measuring a current flowing through the polarographic oxygen concentration measuring sensor, and an analyzing unit for analyzing a signal from the measuring unit, characterized in that the oxygen concentration measuring device further comprises an input unit that allows a user of the device to input a desired measurement start time, the device cancels the power supply to the polarographic oxygen concentration measuring sensor after the user inputs the desired measurement start time, and applies a voltage of -0.9 to -0.6 V to the polarographic oxygen concentration measuring sensor again at a time that is a predetermined time before the desired measurement start time. The predetermined time is preferably 5 to 240 minutes, more preferably 10 to 120 minutes. If it is shorter than the desired range, the small areas around the sensing electrode and counter electrode may not reach electrochemical equilibrium, which may hinder accurate measurement. Also, if it is longer than the desired range, the effect of minimizing the cumulative current flow and preventing sensor deterioration is lost.

[0020] The invention described in claim 2 is the oxygen concentration measuring device described in claim 1, characterized in that calibration is performed after the necessary voltage is applied to the sensor again. By performing calibration automatically, the user can start concentration measurement immediately at the desired measurement start time. Furthermore, in the unlikely event that electrochemical equilibrium has not been achieved in the sensor and accurate concentration measurement is hindered, the calibration will result in an error, notifying the user of the abnormality and preventing measurement from being performed while a defect exists in the sensor and / or device.

[0021] The invention described in claim 3 is an oxygen concentration measuring device in which an enzyme involved in a reaction accompanied by an increase or decrease in oxygen is disposed as an immobilized enzyme layer on the oxygen permeable membrane of the sensor of the oxygen concentration measuring device described in claim 2. Any enzyme involved in a reaction accompanied by an increase or decrease in oxygen can be freely selected as long as it meets the purpose.

[0022] The invention recited in claim 4 is the substrate concentration measurement device recited in claim 3, characterized in that calibration is performed after a necessary voltage is applied to the sensor again.

[0023] The invention described in claim 5 is the invention described in claims 3 and 4, in which glucose oxidase is used as the enzyme involved in a reaction involving an increase or decrease in oxygen. The invention according to this claim can be used as a glucose concentration (substrate concentration) measuring device. Note that the biological origin, separation method, and processing method of glucose oxidase can be freely selected as long as they match the purpose. Effect of the Invention

[0024] According to the present invention, by preventing the deterioration of a polarographic oxygen concentration measuring sensor or an enzyme sensor that uses the same, it is possible to provide an oxygen concentration measuring device or a substrate concentration measuring device that can use the sensor in good condition for a long period of time and perform efficient measurement at the appropriate time. In addition, since the frequency of sensor replacement can be reduced, it is possible to reduce the replacement of expensive bodies that have been precisely processed. This not only contributes to cost, but also reduces the amount of waste plastic and the energy required for body molding, which can help corporate activities in line with the Sustainable Development Goals. Furthermore, since the absolute number of sensors returned from medical sites for regeneration can be reduced, it also contributes to reducing the risk of infection for employees of sensor manufacturers. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a cross-sectional view showing a typical structure of a polarographic oxygen concentration measuring sensor employed in the present invention. [Diagram 2] FIG. 2 is an explanatory diagram showing the system configuration of the substrate concentration measuring device according to the present embodiment. [Diagram 3] FIG. 3 is a block diagram showing the hardware configuration of the substrate concentration measuring device according to the present embodiment. [Figure 4] FIG. 4 is an operation flow diagram of the substrate concentration measuring device according to the present embodiment. [Diagram 5] FIG. 5 is a diagram for supplementarily explaining the contents of the examples and comparative examples. [Figure 6] FIG. 6 is a diagram showing the results of the examples and the comparative examples. [Figure 7] Figure 7 is an image of the sensing electrode of a polarographic oxygen concentration sensor and its surroundings. [Figure 8] FIG. 8 shows a current-voltage curve of a typical polarographic oxygen concentration measurement sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The following describes in detail an embodiment of the present invention, but the present invention is not limited thereto.

[0027] (Polarographic oxygen concentration sensor) Fig. 1 is a cross-sectional view showing a typical structure of a polarographic oxygen concentration measurement sensor used in the present invention. In Fig. 1, reference numeral 1 denotes a sensing electrode (cathode), 2 denotes a resin in which the sensing electrode 1 is embedded, 3 denotes a finely processed portion around the sensing electrode, 4 denotes an electrode housing, and 8 denotes an electrolyte solution.

[0028] The electrode housing 4 in the present invention is not particularly limited as long as it is a container whose wall of the detection section is made of an oxygen-permeable membrane 7, but a typical structure is one in which the tip of a cylindrical container is made of an oxygen-permeable membrane 7, as shown in FIG. 1.

[0029] The material of the parts constituting the electrode housing 4 other than the oxygen permeable membrane 7 can be appropriately selected from known materials that are resistant to the electrolyte solution contained therein. Examples of such materials include inorganic materials such as glass and ceramics, and synthetic resins such as polypropylene, polyethylene, polyvinyl chloride, and epoxy resin.

[0030] The material of the oxygen-permeable film 7 is not particularly limited as long as it is impermeable to liquid and permeable to oxygen. Preferably, the material has a gas permeability coefficient of oxygen of 1×10 -12 (cm 3 cm cm -2 ·S -1 cmHg -1 ) or more, more preferably 1×10 -10 The above are preferred. Specifically, typical examples include fluororesins such as polytetrafluoroethylene, polychlorotrifluoroethylene, and tetrafluoroethylene-hexafluoropropylene copolymers, polyolefin resins such as polyethylene and polypropylene, polystyrene, polyamide, polyvinyl chloride, polyethylene terephthalate, and polymethyl methacrylate. Among these, fluororesins with particularly high oxygen permeability are preferred.

[0031] There is no particular restriction on the thickness of the oxygen-permeable membrane, but it is preferably 1 to 100 μm in order to detect the permeated oxygen by a constant potential electrolytic current, and particularly preferably 10 to 50 μm in order to facilitate easy handling of the membrane.

[0032] In the present invention, in order to measure the amount of oxygen permeating through the oxygen-permeable membrane, at least two electrodes, a sensing electrode 1 and a counter electrode 6, are required as shown in FIG. 1. That is, the sensing electrode 1 is an electrode for electrolyzing oxygen by an electrochemical reaction on its surface, and the counter electrode 6 is an electrode for constituting a circuit for advancing the electrochemical reaction. The sensing electrode 1 can be appropriately selected from known electrodes, and is preferably an electrode made of an inert metal such as platinum or gold. In addition, the counter electrode 6 is generally made of a metal with a high overvoltage such as silver, lead, or mercury. In recent years, a silver electrode has been often used as the counter electrode 6 from the viewpoints of the ease of measurement and the harmfulness of the compounds produced.

[0033] In the oxygen electrode of the present invention, in order to increase the response speed, i.e., the speed from when oxygen comes into contact with the surface of the oxygen-permeable membrane 7 of the electrode housing 4 until an electrode reaction occurs on the surface of the sensing electrode 1, a structure is generally adopted in which the sensing electrode 1 is brought close to the oxygen-permeable membrane 7. The term "close" as mentioned above means that the sensing electrode 1 and the oxygen-permeable membrane 7 are brought as close as possible.

[0034] Other structures and modes of use of the polarographic oxygen concentration measuring sensor of the present invention may be those known in the art, without any particular limitations. For example, as shown in Fig. 1, in the case of a sensing electrode 1 and a counter electrode 6, the sensing electrode 1 is electrically connected to the counter electrode 6 via a power source 9 and an ammeter 10. An aqueous solution containing an alkali metal halide salt, which is a highly stable compound, is enclosed as an electrolyte solution in the electrode housing 4. Specific examples include aqueous solutions containing potassium chloride, sodium chloride, sodium bromide, etc.

[0035] The polarographic oxygen concentration measuring sensor may be provided with a plurality of sensing electrodes 1. When a plurality of sensing electrodes 1 is provided, it is possible to simultaneously measure the oxygen concentration under different conditions or in different measurement objects, and to compare and analyze the respective data.

[0036] (A substrate concentration sensor that combines a polarographic oxygen concentration sensor and an enzyme) For example, by providing an immobilized enzyme layer on multiple sensing electrodes, inactivating the immobilized enzyme on one sensing electrode to make it a reference sensing electrode (hereinafter referred to as Ref electrode), and calculating the difference between the information from the other sensing electrodes (hereinafter referred to as Sig electrode), it is possible to measure the substrate concentration of the enzyme more accurately than when measuring with a single sensing electrode. These signals may be used as they are for concentration measurement, or may be differentiated to obtain the maximum oxygen consumption rate or second-order derivative to obtain the maximum oxygen consumption acceleration, and then used for concentration measurement. When signals are differentiated and then used, the amount of change in response can be detected quickly, making it possible to configure a device with a high processing speed.

[0037] The immobilized enzyme layer can be formed by any known method that suits the purpose, such as a crosslinking method, a lattice-type entrapping method, a microcapsule-type entrapping method, a covalent bond method or an ionic bond method, which are a type of carrier binding method, a physical adsorption method, or a combination of any one or more methods.

[0038] (substrate concentration measuring device) The system configuration of the substrate concentration measuring device according to the present embodiment will be described. Fig. 2 is an explanatory diagram showing the system configuration of the substrate concentration measuring device according to the present embodiment. In this invention, the measurement of glucose concentration as the substrate concentration will be described as an example.

[0039] In FIG. 2, a substrate concentration measuring device 200 is configured to include a sample supplying means 201 , a buffer solution supplying means 202 , a sample dilution / measurement means 203 , and a buffer solution draining means 204 .

[0040] The sample supplying means 201 includes a movable crane 211 that is movable in the X and Y directions in the figure, and a sample dispensing nozzle 212 that dispenses the sample.

[0041] A reaction cell 230 is provided in the direction of movement of the movable crane 211. A sample such as blood is accommodated in the reaction cell 230. The sample is not limited to blood, and plasma, serum, urine, etc. can also be handled. After the movable crane 211 is moved, a predetermined amount of the sample in the sample dispensing nozzle 212 is supplied to the reaction cell 230.

[0042] A buffer solution for diluting a sample can be injected into a reaction cell 230 constituting the sample dilution / measurement means 203 by a buffer solution supply means 202. The buffer solution is stored in a buffer solution bottle 220, and examples of the buffer solution include an aqueous tris(hydroxymethyl)aminomethane solution, an aqueous monomethanolamine solution, an aqueous diethanolamine solution, an aqueous triethanolamine solution, an acetate solution, a citrate solution, a carbonate solution, a phosphate solution, a borate solution, and a Good's buffer solution such as MOPS or HEPES. The buffer solution is sucked by a buffer solution pump 221, and injected into a pre-chamber 205 having a temperature control function via a liquid supply manifold 222, while being monitored by an air bubble detection sensor 223 for the generation of air bubbles. At the same time, the buffer solution in the pre-chamber is sent to the reaction cell 230 via a buffer solution inlet 231.

[0043] The reaction cell 230 is provided with a sample inlet 232 into which a sample is injected, a buffer inlet 231 into which a buffer solution is injected, a stirring space 233 for diluting the sample with the buffer solution, a stirrer 234 that performs dilution by rotation, an oxygen concentration measuring sensor 235 that detects the sample diluted with the buffer solution, and a drain port 236. By switching the solenoid valve of the buffer solution pump 221, the drained liquid after detection is discharged via a path from the drain port 236 to the buffer solution pump 221 to a wash bottle 237.

[0044] The sample pump 224 supplies a cleaning liquid. The cleaning liquid is stored in a cleaning liquid bottle 238. The cleaning liquid is supplied to the sample dispensing nozzle 212 via the liquid supply manifold 222 to the sample pump 224.

[0045] (Hardware configuration of the substrate concentration measuring device 200) Next, a description will be given of the hardware configuration of the substrate concentration measuring device 200. Fig. 3 is a block diagram showing the hardware configuration of the substrate concentration measuring device according to this embodiment.

[0046] 3, the substrate concentration measuring device 200 includes a CPU 301 functioning as a control unit, a ROM 302, a RAM 303, a display 304, and a network I / F (interface) 305. Each of the components 301 to 305 is connected to a bus 300.

[0047] The CPU 301 is responsible for the overall control of the substrate concentration measuring device 200. The ROM 302 stores various data such as a boot program for starting up the substrate concentration measuring device 200 and measurement processing programs. The RAM 303 is used as a work area for the CPU 301.

[0048] The display 304 displays various data. In the present invention, the display 304 not only allows the user to recognize the state of the device, but also functions as a human interface for inputting a desired time to start use. The network I / F 305 controls data communication between the substrate concentration measuring device 200 and other information processing devices.

[0049] (Operation flow of the substrate concentration measuring device 200 according to the present invention) Fig. 4 is an operation flow diagram of the substrate concentration measuring device according to this embodiment. The processing in Fig. 4 is executed by control unit (CPU) 301 of substrate concentration measuring device 200. The device user can input any time at which the device will next be used (hereinafter, referred to as the desired measurement start time) from the input unit. When the desired measurement start time is input, control unit 301 starts a countdown to the desired measurement start time and turns off the power to the sensor (step S401). The power to the sensor may be turned off automatically by the device or by the device user each time it is required.

[0050] The control unit 301 again applies −0.9 to −0.6 V at a time that is a predetermined time before the desired measurement start time (step S402, start of standby time). After the standby time ends (=desired measurement start time, step S403), the control unit 301 starts calibration (step S404). In the calibration, a glucose standard solution of known concentration is used to obtain a calibration curve. Then, the control unit 301 determines whether the calibration state is good or not (step S405). If the calibration state is good (step S405: Yes), the substrate concentration can then be measured, and the control unit 301 waits until the measurement (step S406).

[0051] On the other hand, if the calibration state is not good (step S405: No), the control unit 301 issues an error, and the user of the device can be informed of that fact. For example, the control unit 301 determines the number of times the calibration state is not good (step S407), and if an error occurs the first time (step S407: 1st time), the control unit 301 returns to the process of step S404, and if an error occurs the second time (step S407: 2nd time), the control unit 301 issues an error to the outside of the device (step S408). After the process of step S406 or step S408, the control unit 301 ends the above series of processes.

[0052] In the above-described embodiment and the examples and comparative examples described below, glucose oxidase is immobilized in the immobilized enzyme layer to form a glucose concentration measurement sensor, but it is possible to form a concentration measurement sensor or concentration measurement device for other substrates by replacing it with another enzyme involved in the oxygen increase / decrease reaction.

[0053] (Comparison between Examples and Comparative Examples) Fig. 5 is a diagram for supplementary explanation of the contents of the embodiment and the comparative example, Fig. 5(a) is the comparative example, and Fig. 5(b) is the embodiment of the present invention. The horizontal axis of Fig. 5 is time (24 hours), and the vertical axis is the day of the week.

[0054] The embodiment of the present invention was installed in a glucose analyzer GA09IIα manufactured by A&T Corporation, and operated for about two weeks in the pattern shown in FIG. 5(b). Specifically, it is as follows. The desired measurement start time was set to 09:30 from Monday to Friday, and the power-off time was set to 20:00. 90 minutes before the desired measurement start time, a constant voltage in the range of -0.9 to -0.6 V was applied to the glucose measurement sensor to set the standby time. After the standby time, calibration was performed using aqueous glucose solutions of known concentrations (0 mg / dL and 200 mg / dL). The change in the output value of an aqueous glucose solution with a concentration of 200 mg / dL during calibration was plotted. Considering the individual differences of the sensors, similar data was obtained for the three sensors.

[0055] As a comparative example, as shown in FIG. 5(a), a glucose measurement sensor of the same type as that used in the examples was attached to a glucose analyzer GA09II manufactured by A&T Corporation, and data was obtained in the same manner as in the examples, except that electricity was continuously applied for two weeks.

[0056] (Differences between Examples and Comparative Examples) Figure 6 shows the results of the example and the comparative example. As shown in Figure 6(a), in the comparative example where the current was continuously applied, the output value for the 200 mg / dL glucose aqueous solution tended to decrease. This indicates that the responsiveness to the target substance tends to decrease.

[0057] On the other hand, as shown in Fig. 6(b), in the embodiment in which the current was appropriately released and the cumulative current was reduced, no particular decrease in output was observed as in the comparative example. In addition, in the embodiment, no error was observed in the calibration after re-application. It was confirmed that the repeated release and re-application of current did not cause a lack of electrochemical stability inside the sensor, making it impossible to use it for timely measurements.

[0058] The measurement method described in this embodiment can be realized by executing a prepared program on a computer. This program is recorded on a computer-readable storage medium such as a RAM, a hard disk, a flexible disk, a CD-ROM, an MO, or a DVD, and is executed by being read from the storage medium by the computer. This program may also be a transmission medium that can be distributed via a network such as the Internet. [Industrial Applicability]

[0059] The oxygen concentration measuring device and substrate concentration measuring device according to the present invention can be used in a wide range of fields, such as fermentation process control, environmental measurement for water quality, and measurement in the medical field. [Explanation of symbols]

[0060] 1. Detection electrode (cathode) 2 Resin for embedding the sensing electrode 3. Micromachined area around the sensing electrode 4 Electrode Housing 5 Precious metal electrode 6 Counter electrode (anode) 7. Oxygen permeable membrane 8 Electrolyte solution 9 Power supply 10 Ammeter 200 Substrate concentration measuring device 201 Sample supply means 202 Buffer supply means 203 Sample dilution and measurement methods 204 Buffer solution drainage means 205 Pre-chamber 211 Mobile Crane 212 Sample dispensing nozzle 221 Buffer Pump 222 Liquid supply manifold 223 Air bubble detection sensor 224 Sample Pump 230 Reaction Cell 231 Buffer inlet 232 Sample injection port 233 Stirring space 234 Stirrer 235 Oxygen Electrode 236 Drain 237 Wash Bottle 238 Cleaning solution bottle 301 CPU (control unit) 302 ROM 303 RAM 304 Display 305 Network Interface

Claims

1. A polarographic oxygen concentration measuring sensor; a thermostatic device capable of maintaining the polarographic oxygen concentration measuring sensor at a constant temperature; A power supply unit connected to the polarographic oxygen concentration measuring sensor; A control unit that controls a voltage applied to the polarographic oxygen concentration measuring sensor; A measurement unit that measures a current flowing through the polarographic oxygen concentration measurement sensor; an analysis unit that analyzes a signal from the measurement unit; An oxygen concentration measuring device having An input unit is provided that allows a user of the device to input a desired measurement start time, The control unit stops the power supply to the polarographic oxygen concentration measuring sensor after the user inputs a desired measurement start time, and further an oxygen concentration measuring device which applies a voltage of -0.9 to -0.6 V to said polarographic oxygen concentration measuring sensor again at a time that is a predetermined time prior to said desired measurement start time;

2. The oxygen concentration measuring device described in Claim 1, characterized in that the control unit performs calibration after the re-application of voltage.

3. a substrate concentration measurement sensor in which an immobilized enzyme layer is disposed on the surface of an oxygen permeable membrane of a polarographic oxygen concentration measurement sensor, the immobilized enzyme layer being involved in a reaction accompanied by an increase or decrease in oxygen; a thermostatic device capable of maintaining the substrate concentration measurement sensor at a constant temperature; A power supply unit connected to the substrate concentration measurement sensor; A control unit that controls a voltage applied to the substrate concentration measurement sensor; A measurement unit that measures a current flowing through the substrate concentration measurement sensor; an analysis unit that analyzes a signal from the measurement unit; A substrate concentration measuring device comprising: An input unit is provided that allows a user of the device to input a desired measurement start time, The control unit cancels the power supply to the substrate concentration measurement sensor after the user inputs a desired measurement start time, and further A substrate concentration measuring device comprising: a voltage of −0.9 to −0.6 V being reapplied to said substrate concentration measuring sensor at a time that is a predetermined time prior to said desired measurement start time.

4. A substrate concentration measuring device as described in Claim 3, characterized in that the control unit performs calibration after the re-application of voltage.

5. 5. The substrate concentration measuring device according to claim 3, wherein the enzyme involved in the reaction accompanied by an increase or decrease in oxygen is glucose oxidase.

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