Chemical sensor and method of reproducing chemical sensor

Abstract

To provide a chemical sensor that can be continuously used and applied to environmental monitoring, and to provide a method of reproducing the chemical sensor.SOLUTION: A chemical sensor 1 is provided, comprising a flow channel 2 for causing a sample solution 120 containing a measurement target substance 110 to flow, a sensor unit 3 disposed in the flow channel 2, a first electrode 4 and a second electrode 5 arranged at a distance from each other in the flow channel 2, voltage application means 7 for applying voltage to the first electrode 4 and the second electrode 5, and detection means 8 for detecting the measurement target substance 110 attached to the first electrode 4.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a chemical sensor and a method for regenerating the chemical sensor.

Background Art

[0002] Currently, in industrial activities and daily life, a wide variety of chemical substances are being used. Among chemical substances, there are those that cause environmental pollution and have harmful effects on human health and the ecosystem if proper management is not carried out at each stage such as their production, distribution, use, disposal, and recycling. In addition, there are persistent organic pollutants (POPs) that are difficult to decompose in the environment, accumulate in organisms, and may move over long distances to cause widespread environmental pollution. These substances are targets for pollution prevention, and it is required to cooperate internationally to eliminate and remove them.

[0003] Regulations on the discharge of chemical substances into the environment are becoming increasingly strict. However, it is difficult to correctly understand the impact of chemical substances on ecology and the environment in the actual environment. In such a situation, it is difficult to evaluate the chronic effects of chemical substances. Therefore, it is required to constantly monitor chemical substances at emission sources such as factories and in the living environment such as rivers and waterworks.

[0004] As methods for environmental monitoring, for example, methods using physical sensors such as gas thermal conductivity gas sensors, and methods using chemical sensors such as high-performance liquid chromatography (HPLC), Fourier transform infrared spectrophotometer (FT-IR), inductively coupled plasma mass spectrometer (ICP-MS), etc. are known.

[0005] Conventional methods using physical sensors or chemical sensors are not suitable for environmental monitoring because not only are the facilities large and expensive, but also pretreatment of the chemical substances to be measured is required. Therefore, the present inventors have been considering a method of continuously using a small and inexpensive chemical sensor as a method for environmental monitoring. As a method of performing environmental monitoring using an electrochemical sensor as a chemical sensor, for example, heavy metal measurement by anodic stripping voltammetry is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, chemical sensors have a problem that dirt easily adheres to the electrode surface and their performance deteriorates due to the dirt. Therefore, in chemical sensors, a cleaning operation is required to remove the dirt attached to the electrode surface. Chemical sensors were difficult to use continuously in order to perform the above-described cleaning operation. In order to regenerate a chemical sensor, it was necessary to feed a regeneration liquid (acid, alkali, etc.) into the chemical sensor using a liquid feed pump and a valve. Such a method promotes the complication and enlargement of chemical sensors and causes consumption (necessity of replacement) of reagents. Therefore, it has been difficult to apply chemical sensors to environmental monitoring.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a chemical sensor that can be continuously used and can be applied to environmental monitoring, and a method for regenerating the chemical sensor.

Means for Solving the Problems

[0009] The present invention has the following aspects. [1] A flow path through which a sample solution containing a substance to be measured flows, A sensor unit disposed in the flow path, A first electrode and a second electrode disposed apart from each other in the flow path, Voltage application means for applying a voltage to the first electrode and the second electrode, Detection means for detecting a substance to be measured attached to the sensor unit, a chemical sensor comprising the same. [2] The chemical sensor according to [1], wherein the sensor unit is the first electrode or the second electrode. [3] The chemical sensor according to [1] or [2], further comprising a pH detection unit for detecting the pH of the sample solution present in a region including the first electrode and its periphery. [4] The chemical sensor according to any one of [1] to [3], further comprising a reference electrode disposed apart from the sensor unit in the flow path, and the voltage application means applies a voltage to the sensor unit and the reference electrode. [5] The chemical sensor according to any one of [1] to [4], wherein the first electrode is a conductive diamond electrode. [6] A method for regenerating the chemical sensor according to any one of [1] to [5], A method for regenerating a chemical sensor, wherein a voltage is applied to the first electrode and the second electrode by the voltage application means, and the pH of the sample solution present in a region including the first electrode and its periphery is controlled in the flow path. [7] The method for regenerating a chemical sensor according to [6], wherein the pH of the sample solution present in a region including the first electrode and its periphery is controlled to be 8 or more and 14 or less. [8] The method for regenerating a chemical sensor according to [6], wherein the pH of the sample solution present in a region including the first electrode and its periphery is controlled to be 1 or more and 6 or less.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a chemical sensor that can be continuously used and applied to environmental monitoring, and a method for regenerating the chemical sensor.

Brief Description of the Drawings

[0011]

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Embodiments for Carrying Out the Invention

[0012] Embodiments of the chemical sensor and the regeneration method of the chemical sensor of the present invention will be described. Note that this embodiment is specifically described to better understand the gist of the invention, and does not limit the present invention unless otherwise specified.

[0013] [Chemical Sensor] FIG. 1 shows a schematic configuration of a chemical sensor according to an embodiment of the present invention, and is a schematic diagram showing a cross section along the height direction of the chemical sensor. As shown in FIG. 1, the chemical sensor 1 of this embodiment includes a flow path 2, a sensor unit 3, a first electrode 4, a second electrode 5, a reference electrode 6, a voltage application means 7, and a detection means 8. The chemical sensor 1 of this embodiment may include a pH detection unit 9. Further, the chemical sensor 1 of this embodiment may include a substrate 10 that supports the flow path 2.

[0014] The flow path 2 is a flow path through which a sample solution 120 containing a measurement target substance 110 flows.

[0015] The first electrode 4 and the second electrode 5 are arranged to be separated from each other in the flow path 2. The first electrode 4 and the second electrode 5 are arranged, for example, as shown in FIG. 1, in the flow path 2 so as to sandwich the sensor unit 3 along the flow direction of the sample solution 120 (the length direction of the flow path 2). Further, the first electrode 4 and the second electrode 5 may be arranged in the flow path 2 so as to sandwich the sensor unit 3 along the direction perpendicular to the flow direction of the sample solution 120 (the inner peripheral direction of the flow path 2). Further, the base material 31 of the sensor unit 3 may be the first electrode 4. When the first electrode 4 and the second electrode 5 are arranged so as to sandwich the sensor unit 3, and when the base material 31 of the sensor unit 3 is the first electrode 4, there is almost no difference in the detection ability of the measurement target substance 110 by the chemical sensor 1.

[0016] The voltage application means 7 is connected to the first electrode 4, the second electrode 5, the sensor unit 3, and the reference electrode 6. The voltage application means 7 applies a voltage to the first electrode 4 and the second electrode 5 with the first electrode 4 as the cathode to reduce water molecules in the sample solution 120 at the surface 4a of the first electrode 4, generate hydrogen, and generate a region with a high concentration of hydroxide ions (OH - ) in the vicinity of the surface 4a of the first electrode 4, or applies a voltage with the first electrode 4 as the anode to oxidize chloride ions and hydroxide ions in the sample solution 120 at the surface 4a of the first electrode, generate chlorine and oxygen, and generate a region with a high concentration of hydrogen ions (H + ) in the vicinity of the surface 4a of the first electrode 4. Also, the voltage application means 7 applies a voltage to the sensor unit 3 and the reference electrode 6 to control the voltage between the sensor unit 3 and the reference electrode 6. When the measurement target substance is oxidized or reduced on the working electrode (sensor unit 3), a current flows between the sensor unit 3 and the second electrode 5. The concentration of the measurement target substance 110 is measured from the amount of the current.

[0017] The reference electrode 6 is arranged in the flow path 2 at a distance from the sensor unit 3. The detection means 8 is connected to the sensor unit 3 and detects the measurement target substance 110 attached to the sensor unit 3.

[0018] The pH detection unit 9 detects the pH of the sample solution 120 present in the region α including the first electrode 4 and its periphery. The pH detection unit 9 is connected to the reading unit 11.

[0019] [Flow path] The flow path 2 is not particularly limited as long as it can flow the sample solution 120 containing the substance to be measured (chemical substance) 110. For example, it is preferably a micro flow path formed in the flow path substrate 12 by a hydrogel molding method, a microfabrication method such as photolithography, soft lithography, cutting, bonding, or a method combining these microfabrication methods. In other words, the flow path 2 is preferably a micro flow path formed in the flow path substrate 12 provided on one surface 10a of the substrate 10. The micro flow path has an inner diameter (maximum diameter) on the order of nanometers to millimeters. By using the flow path 2, the substance to be measured 110 can be detected with high sensitivity by the chemical sensor 1. In addition, by the regeneration method described later, the dirt substances (microorganisms, proteins, oils and fats, etc.) attached to the sensor unit 3 can be easily dissociated. Examples of the flow path substrate 12 include silicone rubber, various resins other than silicone rubber, glass, and the like.

[0020] [First Electrode] The first electrode 4 is not particularly limited as long as it is not deteriorated by the sample solution 120 and ions such as hydrogen ions. Examples of the first electrode 4 include a metal electrode made of a metal such as gold or platinum, and a carbon-based electrode. Examples of the carbon-based electrode include an electrode printed with carbon ink, a glassy carbon electrode, and a boron-doped diamond electrode.

[0021] [Second Electrode] The second electrode 5 is not particularly limited as long as it is not deteriorated by the sample solution 120 and ions such as hydrogen ions. Examples of the second electrode 5 include a metal electrode made of a metal such as gold or platinum, and a carbon-based electrode. Examples of the carbon-based electrode include an electrode printed with carbon ink, a glassy carbon electrode, and a boron-doped diamond electrode. Note that either one of the first electrode 4 or the second electrode 5 may be the sensor unit 3.

[0022] [Reference Electrode] The reference electrode 6 is not particularly limited as long as it exhibits a constant potential in the sample solution 120. Examples of the reference electrode 6 include a silver / silver chloride electrode, a standard hydrogen electrode, a calomel electrode, and the like.

[0023] [Voltage application means] The voltage application means 7 is not particularly limited as long as it can apply a voltage to the first electrode 4, the second electrode 5, the sensor unit 3, and the reference electrode 6. Examples of the voltage application means 7 include a voltage generator, a voltage-current generator, and the like.

[0024] [Detection means] The detection means 8 includes an electrical detection unit 13. As the electrical detection unit 13, for example, an ammeter, a potentiostat, or the like is used. When ions (cations) of the measurement target substance (chemical substance) 110 are reduced by the first electrode 4, electrons flow from the first electrode 4 toward the second electrode 5. At the same time, a current flows from the second electrode 5 toward the first electrode 4. Therefore, by measuring the current value flowing from the second electrode 5 toward the first electrode 4, the concentration of the measurement target substance (chemical substance) 110 contained in the sample solution 120 can be measured.

[0025] [Substrate] The substrate 10 is not particularly limited as long as a flow path substrate 12 can be provided on one surface 10a thereof. Examples include a glass substrate, a resin substrate, and the like.

[0026] [Flow path substrate] The flow path substrate 12 is not particularly limited as long as it is not deteriorated by the sample solution 120 and ions such as hydrogen ions and hydroxide ions. Examples of the flow path substrate 12 include a glass substrate material, a resin substrate material, and the like.

[0027] [Sample solution] The sample solution 120 is a solution containing the measurement target substance (chemical substance) 110. Specifically, examples of the sample solution 120 include wastewater discharged from factories and households, river water, seawater, and the like.

[0028] [Substance to be measured (chemical substance)] Examples of the substance to be measured (chemical substance) 110 include heavy metals such as arsenic, cadmium, lead, mercury, selenium, chromium, and copper, environmental pollutants such as cyanide, cyanide complex compounds, alkyl mercury, polychlorinated biphenyls (PCBs), organophosphorus, thiuram, simazine, and thiobencarb, and electron transfer mediators such as potassium ferricyanide, aminophenol, and ferrocene derivatives.

[0029] [Method of using the chemical sensor] An example of the method of using the chemical sensor 1 of the present embodiment will be described. Here, a method of detecting arsenic by stripping voltammetry using the chemical sensor 1 will be described.

[0030] While flowing the sample solution 120, a voltage is applied to the sensor unit 3 (working electrode) and the reference electrode 6 (counter electrode) by the voltage application means 7, and the voltage between the sensor unit 3 and the reference electrode 6 is controlled. The substance to be measured 110 is reduced on the working electrode (sensor unit 3), and the substance to be measured 110 is electrodeposited on the surface 3a of the sensor unit 3. Then, when the voltage between the sensor unit 3 and the reference electrode 6 is swept in the positive direction, the substance to be measured 110 electrodeposited on the surface 3a of the sensor unit 3 is oxidized and dissolved in the sample solution 120. When the substance to be measured 110 is dissolved, a current flows between the sensor unit 3 and the second electrode 5. The concentration of the substance to be measured 110 is measured from the amount of the current. The electrical detection unit 13 includes a potentiostat and an information processing device. At this time, when As(III) is the measurement target, the potential is set to -0.1V. When both As(V) or As(III) and As(V) are measurement targets, the potential is varied in two steps. First, the potential is set to -1.0V to reduce As(V), and then the potential is set to -0.1V. In any case, after setting the potential to -0.1V, by holding the potential of the first electrode 4 at -0.1V for a while, arsenic can be concentrated and sufficiently electrodeposited.

[0031] The electrochemical reaction in the electrodeposition process for detecting both As(V) or As(III) and As(V) will be described in more detail below. The standard oxidation potential of As(V) is as follows. 2H 2 AsO 4 - +6H + +4e - =As 2 O 3 +5H 2 O (E 0 =-0.036V vs Ag / AgCl) As 2 O 3 +H 2 O = 2HAsO 2 HAsO 2 +3H + +3e - =As + 2H 2 O (E 0 =-0.036V vs Ag / AgCl)

[0032] Thus, until As(V) is electrodeposited (precipitated) on the surface 3a of the sensor unit 3, there are two-stage reactions of a reduction reaction and an electrodeposition reaction. Therefore, to electrodeposit As(V), first, the potential is set to -1.0 V to reduce As(V) to As(III), and then the potential is set to -0.1 V to electrodeposit As(III) on the surface 3a of the sensor unit 3.

[0033] When arsenic and gold are electrodeposited on the surface 3a of the sensor unit 3, the flow of the sample solution 120 is stopped, and the potential of the sensor unit 3 is swept in the positive potential direction from -0.1 V by a potentiostat (electric detection unit 13) to elute arsenic into the sample solution 120.

[0034] When arsenic is eluted, a current is generated accordingly. At this time, when a negative potential is applied in two stages with As(V) and As(III) as the measurement targets, the total amount of As(V) and As(III) present in the sample solution 120 can be detected as the peak current value of As(III).

[0035] The current value (electrical signal) generated by such an electrochemical reaction is transmitted to a potentiostat (electrical detection unit 13), and the potentiostat (electrical detection unit 13) controls and detects the signal at each electrode. The signal detected by the potentiostat (electrical detection unit 13) is transmitted to an information processing device (electrical detection unit 13), and the calibration curve between the arsenic concentration and the current value created in advance is compared with the obtained current value, and the arsenic concentration in the sample solution is calculated.

[0036] Next, a voltage is applied to the first electrode 4 and the second electrode 5 by the voltage application means 7. The first electrode 4 is used as the cathode and the second electrode 5 is used as the anode to apply a voltage. The water molecules in the sample solution 120 are reduced at the surface 4a of the first electrode 4 to generate hydrogen, and a high-concentration hydroxide ion (OH - ) region is generated and moved to the region α including the first electrode 4 and its periphery, so that the pH of the sample solution 120 existing in the region α including the first electrode 4 and its periphery exceeds 7. As a result, due to the alkaline sample solution 120, microorganisms, proteins, oils and fats, etc. contained in the sample solution 120 attached to the surface 3a of the sensor unit 3 are dissociated, and the sensor unit 3 is regenerated to a state where microorganisms, proteins, oils and fats, etc. contained in the sample solution 120 are not attached. Thereby, it becomes possible to attach the measurement target substance 110 contained in the sample solution 120 to the sensor unit 3 again.

[0037] Note that depending on the type of the measurement target substance 110 and the microorganisms, proteins, oils and fats, etc. contained in the sample solution 120, a voltage is applied by the voltage application means 7 with the first electrode 4 as the anode and the second electrode 5 as the cathode, and chloride ions and hydroxide ions in the sample solution 120 are oxidized at the surface 4a of the first electrode 4 to generate chlorine and oxygen, and a high-concentration hydrogen ion (H + ) region is generated and the hydrogen ions (H +) may be moved to the region α including the first electrode 4 and its periphery. As a result, in the flow path 2, the pH of the sample solution 120 present in the region α including the first electrode 4 and its periphery becomes less than 7. As a result, due to the acidic sample solution 120, metals, metal oxides, etc. contained in the sample solution 120 attached to the surface 3a of the sensor unit 3 are dissociated, and the sensor unit 3 is regenerated to a state where the measurement target substance 110 and metals, metal oxides, etc. contained in the sample solution 120 are not attached.

[0038] According to the chemical sensor 1 of the present embodiment, a voltage is applied to the first electrode 4 and the second electrode 5 by the voltage application means 7 to reduce water molecules in the sample solution 120 to generate hydrogen, and a high concentration of hydroxide ions (OH ー ) region is generated, or chloride ions and hydroxide ions in the sample solution 120 are oxidized to generate chlorine and oxygen, and a high concentration of hydrogen ions (H + ) region is generated, and in the flow path 2, the pH of the sample solution 120 present in the region α including the sensor unit 3 and its periphery can be controlled. As a result, due to the alkaline or acidic sample solution 120, microorganisms, proteins, oils and fats, metals, metal oxides, etc. contained in the sample solution 120 attached to the surface 3a of the sensor unit 3 are dissociated, and the sensor unit 3 can be regenerated to a state where microorganisms, proteins, oils and fats, metals, metal oxides, etc. contained in the sample solution 120 are not attached. Therefore, since the chemical sensor 1 can be used continuously, it can be applied to environmental monitoring. In addition, since the chemical sensor 1 can regenerate the sensor unit 3 without using large-scale equipment, it can be miniaturized and applied to environmental monitoring.

[0039] [Other Embodiments] Note that the present invention is not limited to the above-described embodiment. The chemical sensor of the present invention may adopt, for example, a modification as shown in FIG. 2. In the drawings showing each modification, the same parts as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted, and only the differences will be described.

[0040] [Modification Example] As shown in FIG. 2, the chemical sensor 200 of the modification example may be configured such that the detection means 8 includes a light source 210 that irradiates the sensor unit 3 with white light, and a detector 220 that detects the amount by which the wavelength of the light attenuated by surface plasmon resonance changes when the measurement target substance 110 adheres to the sensor unit 3. According to the chemical sensor 200 of the modification example, the amount of the measurement target substance 110 adhering to the sensor unit 3 can be directly measured by the surface plasmon resonance method.

[0041] [Method for regenerating chemical sensor] The method for regenerating the chemical sensor according to an embodiment of the present invention is a method for regenerating the sensor unit in the chemical sensor according to an embodiment of the present invention described above.

[0042] "First regeneration method" In the method for regenerating the chemical sensor of the present embodiment, for example, in the chemical sensor 1, a voltage is applied by the voltage application means 7 with the first electrode 4 as the cathode and the second electrode 5 as the anode, and water molecules in the sample solution 120 are reduced at the surface 4a of the first electrode 4 to generate hydrogen, and a high-concentration hydroxide ion (OH ー ) region is generated to control the pH of the sample solution 120 existing in the region α including the first electrode 4 and its periphery to be greater than 7.

[0043] The voltage applied to the first electrode 4 and the second electrode 5 is not particularly limited, but is preferably, for example, 1 V or more and 10 V or less, and more preferably 3 V or more and 8 V or less. When the voltage is less than 1 V, the reaction amount of ions is small, and it becomes difficult to sufficiently control the pH of the sample solution 120 existing in the region α including the first electrode 4 and its periphery. When the voltage exceeds 10 V, the amount of gas generated from the vicinity of the first electrode 4 increases, and the risk of gas retention in the flow path 2 becoming a problem increases.

[0044] The time for applying the voltage to the first electrode 4 and the second electrode 5 is not particularly limited, but is preferably, for example, 1 minute or more and 20 minutes or less, and more preferably 1 minute or more and 5 minutes or less.

[0045] In the flow path 2, the pH of the sample solution 120 present in the region α including the first electrode 4 and its periphery is appropriately controlled according to the type of the contaminant. When the contaminant is a water-soluble (slightly soluble) contaminant such as a denatured protein, and when dissociating the contaminant from the sensor unit 3, the sample solution 120 is set to be weakly alkaline (pH 8 to 12). When the contaminant is an oily (strongly acidic) contaminant such as a fatty acid, and when dissociating the contaminant from the sensor unit 3, the sample solution 120 is set to be weakly alkaline (pH 8 to 12). When the contaminant is an oily (medium polar) contaminant such as an animal or vegetable fat, and when dissociating the contaminant from the sensor unit 3, the sample solution 120 is set to be strongly alkaline (pH 12 to 14). When the contaminant is a solid (hydrophilic) contaminant such as mud, and when dissociating the contaminant from the sensor unit 3, the sample solution 120 is set to be weakly alkaline (pH 8 to 12).

[0046] The sample solution 120 may contain a pH indicator. The pH indicator is not particularly limited as long as it can indicate the range from alkaline (pH 14) to acidic (pH 1). For example, alizarin yellow, thymol blue, methyl red, phenolphthalein, etc. may be mentioned. Alizarin yellow shows yellow in neutrality and changes to orange in alkalinity. Alizarin yellow shows yellow at pH 10, and the closer it is to orange, the higher the pH and the higher the alkalinity. If the sample solution 120 contains a pH indicator, the pH of the sample solution 120 present in the region α including the first electrode 4 and its periphery can be confirmed by applying a voltage to the first electrode 4 and the second electrode 5. Based on the pH indicator, it is possible to determine whether to continue applying the voltage to the first electrode 4 and the second electrode 5, or to stop applying the voltage to the first electrode 4 and the second electrode 5.

[0047] Further, the chemical sensor 1 may include a pH detection unit 9 such as a pH meter that detects the pH of the sample solution 120 present in the region α including the first electrode 4 and its periphery. If the pH detection unit 9 is provided, by applying a voltage to the first electrode 4 and the second electrode 5, the pH of the sample solution 120 present in the region α including the first electrode 4 and its periphery can be confirmed. The pH detection unit 9 can immediately determine whether to continue applying the voltage to the first electrode 4 and the second electrode 5 or to stop applying the voltage to the first electrode 4 and the second electrode 5.

[0048] According to the electrode regeneration method of the present embodiment, by applying a voltage to the first electrode 4 and the second electrode 5 and controlling the pH of the sample solution 120 present in the region α including the first electrode 4 and its periphery to be greater than 7, the measurement target substance 110 attached to the surface 3a of the sensor unit 3 by the alkaline sample solution 120, and microorganisms, proteins, oils and fats, etc. contained in the sample solution 120 are dissociated, and the sensor unit 3 can be regenerated to a state where the measurement target substance 110 is not attached. Therefore, the chemical sensor 1 can be used repeatedly and continuously. In addition, the sensor unit 3 can be regenerated without using large-scale equipment.

[0049] "Second regeneration method" In the electrode regeneration method of the chemical sensor of the present embodiment, the voltage application means 7 applies a voltage with the first electrode 4 as the anode and the second electrode 5 as the cathode, oxidizes chloride ions and hydroxide ions in the sample solution 120 at the surface 4a of the first electrode 4, generates chlorine and oxygen, and generates a high-concentration hydrogen ion (H + ) region near the surface 4a of the first electrode 4 to control the pH of the sample solution 120 present in the region α including the first electrode 4 and its periphery to be less than 7.

[0050] The voltage applied to the first electrode 4 and the second electrode 5 is not particularly limited, but for example, it is preferably 1 V or more and 10 V or less, and more preferably 2 V or more and 8 V or less. If the voltage is less than 1 V, the reaction amount of ions is small, and it becomes difficult to sufficiently control the pH of the sample solution 120 present in the region α including the first electrode 4 and its vicinity. If the voltage exceeds 10 V, the amount of gas generated from the vicinity of the first electrode 4 increases, and the risk of gas retention in the flow path 2 becoming a problem increases.

[0051] The time for applying a voltage to the first electrode 4 and the second electrode 5 is not particularly limited, but for example, it is preferably 1 minute or more and 20 minutes or less, and more preferably 1 minute or more and 10 minutes or less.

[0052] In the flow path 2, the pH of the sample solution 120 present in the region α including the first electrode 4 and its vicinity is appropriately controlled according to the type of dirt substance. When the dirt substance is a metal, a metal oxide, etc., when dissociating the dirt substance from the first electrode 4, the sample solution 120 is made weakly acidic (pH 1 to 6).

[0053] The sample solution 120 may contain a pH indicator. The pH indicator is not particularly limited as long as it can indicate the range from alkaline (pH 14) to acidic (pH 1). For example, thymol blue, methyl red, phenolphthalein, etc. can be mentioned. Thymol blue shows yellow in neutral and changes to red in acidic. Thymol blue shows yellow at pH 3, and the closer it is to red, the lower the pH and the higher the acidity. If the sample solution 120 contains a pH indicator, the pH of the sample solution 120 present in the region α including the first electrode 4 and its vicinity can be confirmed by applying a voltage to the first electrode 4 and the second electrode 5. It is possible to judge whether to continue applying a voltage to the first electrode 4 and the second electrode 5 or to stop applying a voltage to the first electrode 4 and the second electrode 5 based on the pH indicator.

[0054] Also in the second regeneration method, similar to the second regeneration method, the chemical sensor 1 may include a pH detection unit such as a pH meter that detects the pH of the sample solution 120 present in the region α including the first electrode 4 and its periphery.

[0055] According to the electrode regeneration method of the present embodiment, by applying a voltage to the first electrode 4 and the second electrode 5 and controlling the pH of the sample solution 120 present in the region α including the first electrode 4 and its periphery to be less than 7, the acidic sample solution 120 dissociates the measurement target substance 110 attached to the surface 3a of the sensor unit 3 and metals, metal oxides, etc. contained in the sample solution 120, and the sensor unit 3 can be regenerated to a state where the measurement target substance 110 is not attached. Therefore, the chemical sensor 1 can be used repeatedly and continuously. In addition, the sensor unit 3 can be regenerated without using large-scale equipment.

Example

[0056] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples.

[0057] [Reference Example 1] Using the measuring device shown in FIG. 3, the time change of cyclic voltammetry due to the attachment of bovine serum albumin (BSA) to the working electrode (sensor unit) was examined. In the device shown in FIG. 3, reference numeral 201 is a cell, reference numeral 202 is a conductive diamond electrode as a working electrode, reference numeral 203 is a conductive diamond electrode as a counter electrode, and reference numeral 204 is Ag / AgCl as a reference electrode. As the sample solution, 0.2 mmol / L sulfuric acid, 1 mmol / L potassium ferricyanide (K 3 Fe(CN) 6 ) containing 0.0005% bovine serum albumin (BSA) was used. The results are shown in FIG. 4. From the results shown in Fig. 4, it was found that the current peak value of potassium ferricyanide decreased as time passed. This is presumably because the effective electrode area of the working electrode decreased due to the attachment of bovine serum albumin (BSA) to the working electrode.

[0058] [Comparative Example 1] Using the measuring device shown in Fig. 3, bovine serum albumin (BSA) was attached to the working electrode (sensor part). As the sample solution, a solution containing 0.2 mmol / L sulfuric acid, 1 mmol / L potassium ferricyanide (K 3 Fe(CN) 6 ) and 0.0005% bovine serum albumin (BSA) was used. Thereafter, a 7% aqueous solution of an alkaline phosphorus-free cleaning agent (trade name: Decon 90, manufactured by Decon Laboratories Ltd.) was flowed through the cell to clean the inside of the cell. Cyclic voltammetry was examined for the case where ultrasonic waves were applied for 10 minutes using the above aqueous solution. The results are shown in Fig. 5. From the results shown in Fig. 5, it was found that the cleaning of the working electrode progressed when it was cleaned with the alkaline cleaning solution.

[0059] [Example 1] Using the measuring device shown in Fig. 3, bovine serum albumin (BSA) was attached to the working electrode (sensor part). As the cleaning solution, a 0.9% aqueous sodium chloride solution was used. Using the working electrode contaminated by attaching bovine serum albumin, after measuring 0.2 mmol / L sulfuric acid and 1 mmol / L potassium ferricyanide (K 3 Fe(CN) 6 ) by cyclic voltammetry, the solution was exchanged for a 0.9% aqueous sodium chloride solution, a voltage was applied between the working electrode and the reference electrode at -4V for 10 minutes, and then the solution was changed to 0.2 mmol / L sulfuric acid and 1 mmol / L potassium ferricyanide (K 3 Fe(CN) 6) was replaced to perform cyclic voltammetry measurement, and the cleaning ability was evaluated by comparing the cyclic voltammograms before and after the regeneration operation (-4V, voltage application for 10 minutes) in 0.9% sodium chloride aqueous solution. The results are shown in Fig. 6. From the results shown in Fig. 6, it was found that when an aqueous solution containing sodium chloride was used, the cleaning of the working electrode progressed.

[0060] [Example 2] As the cleaning solution, 10 mmol / L phosphate buffered saline (PBS) containing 1 mmol / L potassium ferricyanide (K 3 Fe(CN) 6 ) was used. Using a working electrode contaminated by attaching bovine serum albumin, after measuring 0.2 mmol / L sulfuric acid and 1 mmol / L potassium ferricyanide (K 3 Fe(CN) 6 ) by cyclic voltammetry, the solution was replaced with 0.9% sodium chloride aqueous solution, and after applying a voltage of -4V between the working electrode and the reference electrode for 10 minutes, the solution was replaced with 10 mmol / L phosphate buffered saline (PBS) containing 1 mmol / L potassium ferricyanide (K 3 Fe(CN) 6 ) to perform cyclic voltammetry measurement, and the cleaning ability was evaluated by comparing the cyclic voltammograms before and after the regeneration operation (-4V, voltage application for 10 minutes) in 0.9% sodium chloride aqueous solution. Hereinafter, cyclic voltammetry was examined in the same manner as in Example 1. The results are shown in Fig. 7. From the results shown in Fig. 7, it was found that when phosphate buffered saline containing potassium ferricyanide was used, the cleaning of the working electrode progressed.

[0061] [Example 3] As the cleaning solution, 10 mmol / L phosphate buffered saline (PBS) containing 1 mmol / L potassium ferricyanide (K 3 Fe(CN) 6 ) with 0.0005% bovine serum albumin (BSA) added was used. Next, cyclic voltammetry was examined in the same manner as in Example 1. The results are shown in Fig. 8. From the results shown in Fig. 8, it was found that when using phosphate buffered saline containing potassium ferricyanide and bovine serum albumin, the cleaning of the working electrode proceeded, and further cleaning proceeded by allowing it to stand even after cleaning. In Example 3, it was found that cleaning proceeded even when the measurement solution and the cleaning solution were the same, that is, even when the cleaning solution contained bovine serum albumin. This result indicates that cleaning can be performed without exchanging the cleaning solution. That is, it is possible to solve problems such as the enlargement of the device for incorporating the mechanism of exchanging the cleaning solution and the consumption of reagents.

[0062] [Reference Example 2] The measuring device shown in Fig. 3 was used. As the cleaning solution, 10 mmol / L phosphate buffered saline (PBS) was used. As the working electrode, a conductive diamond electrode or a gold thin film electrode was used. As the gold thin film electrode, a film formed by sputtering on a silicon substrate to have a gold thin film of 50 nm / chromium thin film of 5 nm was used. A voltage of -1V to -4V was applied to the working electrode and the reference electrode for 60 seconds, and the pH of the aqueous solution near the surface of the working electrode at that time was measured. A pH meter was used for the pH measurement. The results are shown in Fig. 9. From the results shown in Fig. 9, it was found that when using either a conductive diamond electrode or a gold thin film electrode as the working electrode, by increasing the voltage applied to the working electrode and the counter electrode, the pH of the aqueous solution near the surface of the working electrode can be increased to 10 or more. Also, when using a gold thin film electrode as the working electrode, it was found that even when the applied voltage was -1V, the thin film peeled off from the silicon substrate, and the peeling of the thin film increased as the voltage increased.

[0063] [Example 4] Using the measuring device shown in Fig. 3, bovine serum albumin (BSA) was attached to the working electrode (sensor part). As the cleaning solution, an aqueous solution containing 10 mmol / L phosphate buffered saline (PBS) was used. The results are shown in Fig. 10. From the results shown in Fig. 10, it was found that when a conductive diamond electrode was used as the working electrode, the cleaning of the working electrode proceeded.

[0064] [Comparative Example 2] Using the measuring device shown in Fig. 11, bovine serum albumin (BSA) was attached to the working electrode (sensor part). In the measuring device shown in Fig. 11, reference numeral 301 is a cell, reference numeral 302 is a glassy carbon electrode as the working electrode, reference numeral 303 is a conductive diamond electrode as the counter electrode, and reference numeral 304 is Ag / AgCl as the reference electrode. As the cleaning solution, 10 mmol / L phosphate buffered saline (PBS) was used. The results are shown in Fig. 12. From the results shown in Fig. 12, it was found that when a glassy carbon electrode was used as the working electrode, the cleaning of the working electrode did not proceed. When a glassy carbon electrode was used, during cleaning, the electrode film peeled off and the signal deteriorated. That is, it was found that the glassy carbon electrode cannot be applied to the regeneration method of the chemical sensor of the present invention.

[0065] [Comparative Example 3] Using the measuring device shown in Fig. 13, bovine serum albumin (BSA) was attached to the working electrode (sensor part). In the measuring device shown in Fig. 13, reference numeral 401 is a cell, reference numeral 402 is a gold electrode as the working electrode, reference numeral 403 is a conductive diamond electrode as the counter electrode, and reference numeral 404 is Ag / AgCl as the reference electrode. As the cleaning solution, 10 mmol / L phosphate buffered saline (PBS) was used. The results are shown in Fig. 14. From the results shown in Fig. 14, it was found that when a gold electrode was used as the working electrode, the cleaning of the working electrode proceeded. When a gold electrode was used, it is considered that the gold electrode deteriorates during cleaning. Therefore, it was found that the gold electrode is not suitable for the regeneration method of the chemical sensor of the present invention.

Industrial Applicability

[0066] Since the chemical sensor of the present invention can be used continuously, it can be applied to environmental monitoring.

Explanation of Reference Numerals

[0067] 1,200 Chemical sensor 2 Flow path 3 Sensor unit 4 First electrode 5 Second electrode 6 Reference electrode 7 Voltage application means 8 Detection means 9 pH detection unit 10 Substrate 11 Reading unit 12 Flow path substrate 13 Electrical detection unit 110 Substance to be measured 120 Sample solution 210 Light source 220 Detector

Claims

1. A flow path through which a sample solution containing a substance to be measured flows, A sensor unit disposed in the flow path, A first electrode and a second electrode disposed apart from each other in the flow path, Voltage application means for applying a voltage to the first electrode and the second electrode, A chemical sensor comprising detection means for detecting the substance to be measured adhering to the first electrode.

2. The chemical sensor according to claim 1, wherein the sensor unit is the first electrode or the second electrode.

3. The chemical sensor according to claim 1, further comprising a pH detection unit for detecting the pH of the sample solution present in the region including the first electrode and its periphery.

4. The chemical sensor according to claim 1, further comprising a reference electrode disposed apart from the sensor unit in the flow path, wherein the voltage application means applies a voltage to the sensor unit and the reference electrode.

5. The chemical sensor according to claim 1, wherein the first electrode is a conductive diamond electrode.

6. A method for regenerating the chemical sensor according to any one of claims 1 to 5, wherein a voltage is applied to the first electrode and the second electrode by the voltage application means, and the pH of the sample solution present in the region including the first electrode and its periphery is controlled in the flow path.

7. The method for regenerating the chemical sensor according to claim 6, wherein the pH of the sample solution present in the region including the first electrode and its periphery is controlled to be 8 or more and 14 or less.

8. The method for regenerating the chemical sensor according to claim 6, wherein the pH of the sample solution present in the region including the first electrode and its periphery is controlled to be 1 or more and 6 or less.

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