JP2005221299A - Metal ion measuring method and metal ion measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring method and a measuring device capable of measuring kind and concentration of metal ions in a solution on an on-line basis. <P>SOLUTION: This method comprises the steps of: immersing a working electrode and a counter electrode in a measuring solution; passing an electric current between the working electrode and the counter electrode, and measuring a potential-current curve due to an electrochemistry reaction to specify the kind of metal ions in the solution; holding the potential of the working electrode to the reduction potential of the specified metal ions; detecting the minute deformation amount of the working electrode generated by a metal film formed on the working electrode; and determining the metal ion concentration in the solution based on the minute deformation amount. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a measurement method and a measurement apparatus for measuring the concentration of a trace substance present in a solution, and in particular, to measure the type and concentration of metal ions in a solution.

Conventionally, as a method for measuring the concentration of a trace substance present in a solution, there has been a method for measuring a substance concentration using photothermal spectroscopy (see, for example, Non-Patent Document 1).
In this method, measurement is performed using two laser beams of excitation light having a wavelength that matches the absorption wavelength of the measurement sample and probe light having a wavelength region in which the sample does not absorb. By converting the energy of the excitation light absorbed in the measurement sample as heat, a temperature gradient is generated near the focal point of the laser, and as a result, a concentration gradient of trace substances existing in the solution also occurs. As a result, a difference in refractive index occurs in the excitation light irradiation portion, and a thermal lens effect corresponding to the concentration gradient appears. When this effect is utilized to irradiate the irradiating portion with probe light, the probe light is refracted by a thermal lens corresponding to the concentration gradient, and an optical path change occurs. A pinhole is installed in the vicinity of the light detector, and the difference in refractive index generated by the thermal lens effect is detected as the difference in the intensity of the laser light incident on the light detector, so that the concentration of trace substances in the solution is highly sensitive. Can be determined.

Kitamori et al., “Thermal Lens Microscope”, Jpn. J. et al. Appl. Phys. 39, 5316-5322 (2000)

  However, since the photothermal spectroscopy uses light absorption of a substance, it is difficult to measure the concentration of a substance that changes due to light absorption or a substance that has very large light absorption. In addition, if a substance that does not absorb light, for example, the concentration of metal ions in a solution is measured by the measurement method using the photothermal spectroscopy, light of a specific wavelength is once absorbed by the metal ions to be measured. It was necessary to mark with a substance to be used, and the concentration of the metal ion could not be detected online.

  The present invention has been made to solve such problems, and an object of the present invention is to obtain a measurement method and a measurement apparatus that can measure the type and concentration of metal ions in a solution on-line.

  In the method for measuring metal ions according to the present invention, a working electrode and a counter electrode are immersed in a measuring solution, a current is passed between the working electrode and the counter electrode, and a potential-current curve by an electrochemical reaction is measured. The step of identifying the type of metal ion in the solution, the step of maintaining the potential of the working electrode at the reduction potential of the identified metal ion, and the working electrode generated by the metal coating formed on the working electrode. The method includes a step of detecting a minute deformation amount and a step of determining a metal ion concentration in the solution based on the minute deformation amount.

  Further, the metal ion measuring apparatus according to the present invention includes a device main body in which a solution passes or contains a solution, a working electrode and a counter electrode disposed so as to contact the solution in the device main body, and the working electrode. Control means for controlling the potential of the electrode, potential-current detection means for detecting the current flowing corresponding to the potential of the working electrode, and the action deformed by a metal film formed on the electrode surface of the working electrode by an electrochemical reaction A deformation amount detecting means for detecting the deformation amount of the electrode is provided.

  In the method for measuring metal ions according to the present invention, a potential-current curve due to an electrochemical reaction is measured, whereby the type of metal ions in the solution can be specified. In addition, by utilizing the fact that the electrode is deformed by the metal film formed on the electrode by the electrochemical reaction, and measuring the minute deformation amount of the electrode, even a minute quantitative measurement of metal ions in the solution can be performed online. It becomes possible.

  Further, the metal ion measuring apparatus according to the present invention includes a device main body in which a solution passes or contains a solution, a working electrode and a counter electrode disposed so as to come into contact with the solution in the device main body, and the working electrode. Control means for controlling the potential of the electrode, potential-current detection means for detecting the current flowing corresponding to the potential of the working electrode, and the action deformed by a metal film formed on the electrode surface of the working electrode by an electrochemical reaction Since the deformation amount detecting means for detecting the deformation amount of the electrode is provided, it is possible to easily measure the type and concentration of the metal ion in the solution.

Embodiment 1 FIG.
The redox potential of the metal ion dissolved in the aqueous solution varies depending on the type of ion. If the working electrode is immersed in the solution and charge is transferred to and from the working electrode, a reduction precipitation reaction of metal ions in the solution occurs, and a film such as a metal film or an adsorbed compound layer is formed on the working electrode surface. The The type of metal ion present in the solution can be specified from the potential at which the reduction current is observed.
In addition, the growth rate and thickness of the film deposited on the electrode surface change corresponding to the metal ion concentration in the solution. In general, when a metal film is formed on the surface of a base metal, a crystal mismatch occurs between the film and the base metal. In particular, many lattice defects and dislocations are generated at the interface between the film and the base metal, which increase with the growth of the film, and stress is generated between the film and the base metal. It has been reported that when a plating film, a gas phase formation film, an oxide film, or the like is generated on the surface of the base metal, stress is generated. Similarly, in the case of the present embodiment, the film deposited on the electrode surface generates stress on the working electrode, and as a result, the working electrode is slightly deformed. For example, when a Ni plate (thickness 10 μm) is plated on a platinum plate having a length of 85 mm, a width of 10 mm, and a thickness of 0.2 mm, the film strain is about 0.01% and the deformation is about 500 nm. The stress in this case was a compressive stress on the substrate. Therefore, when metal ions are deposited on a substrate having a length of 100 mm, deformation of about 10 nm to 500 nm can be expected. Therefore, while detecting this amount of minute deformation, a calibration curve that clarifies the relationship between the amount of minute deformation of the electrode and the ion concentration in the solution, or the time differential value of the amount of minute deformation of the electrode and the ion concentration in the solution. A calibration curve with a clear relationship is prepared in advance, and the ion concentration in the solution can be determined by using this calibration curve.

Hereinafter, a method for measuring metal ions according to the first embodiment will be described with reference to FIG.
First, a substrate such as glass on which a metal electrode is formed is used as a working electrode, and the working electrode and the counter electrode are directly immersed in a measurement sample (step S1).
Next, a current is passed between the working electrode immersed in the solution and the counter electrode, and a potential-current curve (polarization curve) due to an electrochemical reaction is measured (step S2). FIG. 2 shows a conceptual diagram of a current spectrum obtained by scanning the potential on the working electrode. In FIG. 2, the horizontal axis represents potential (V (SHE: standard hydrogen electrode reference)), and the vertical axis represents current (A). Since the redox potential of various ions in the solution differs depending on the type of ion, when a potential scan is performed, the metal ions in the solution undergo a reductive precipitation reaction at a specific potential, and a current spectrum corresponding to this reaction is observed. Is done. The ion species dissolved in the solution is determined from the potential at which the reduction current is observed (step S3).

Next, the potential of the working electrode is held at a potential corresponding to the determined ion species (step S4). As a result, the metal ions are deposited or adsorbed on the surface of the working electrode and form a film on the electrode surface. The growth rate and thickness of the film varies with the concentration of ions in the solution. The film formed on the electrode surface generates stress on the working electrode.
If a thin glass substrate with a metal vapor deposition thin film is used as the working electrode, when the electrode potential at which the reduction reaction of the metal ions occurs is maintained, the working electrode is caused by the stress generated in the working electrode due to the formation of the metal film. Small deformation. This microdeformation amount is measured with high sensitivity (step S5), the time differential value of the measured microdeformation amount is calculated (step S6), the calculated value, the time differential value of the microdeformation amount of the electrode, and the ions in the solution The metal ion concentration in the solution is determined by associating the relationship with the concentration with a calibration curve measured in advance (step S7). By such a method, the metal ion concentration in the solution can be determined on-line with high sensitivity. Further, the measurement method of the present invention uses an electrochemical reaction, and has an effect that is not subject to restrictions such as light absorption of the solution and solution alteration due to the photoreaction.

  As a method for measuring the amount of minute deformation of the substrate with high sensitivity, there are methods such as measurement using interference fringes, measurement of laser beam displacement, measurement using a piezoelectric element, and measurement of change in capacitance.

  Further, in the above embodiment, in step S1, the working electrode is directly immersed in the solution system to be measured. However, the solution is separated in the cell, and the working electrode and the counter electrode are immersed in the cell so that the ionic species. May be determined. In this case, if the amount of minute deformation is measured with high sensitivity in step S5, the calculation in step S6 is not performed, and the relationship between the amount of minute deformation measured in step S7, the amount of minute deformation of the electrode, and the ion concentration in the solution. Is associated with a calibration curve measured in advance, so that the ion concentration in the solution can be determined off-line.

  In addition, when separating the solution into the cell, an electrolyte may be added to increase the electrical conductivity in the solution. A desirable electrolyte is one that does not participate in the electrode reaction and stabilizes the pH of the solution. Such electrolytes include boric acid + borax solution.

  In an electrochemical reaction in an aqueous solution, an electrolysis reaction of water occurs simultaneously with an ion redox reaction. Oxygen is generated at the anode side potential, and hydrogen is generated at the cathode side potential. Therefore, in order to detect a minute current, it is necessary to remove these current components. In this experiment, the polarization curve was measured in pure water in advance, and then the polarization curve was measured in the target solution. By taking the difference between the two, the current associated with the redox reaction of the metal ions in the solution could be observed with high accuracy. Even when an electrolyte such as boric acid + borax is added, the polarization curve is measured in advance in an aqueous solution to which the electrolyte is added, and then the polarization curve is measured in a solution in which the same electrolyte is added to the target solution. By taking the difference between the two, the current associated with the redox reaction of the metal ions in the solution could be observed with high accuracy. As a result, it is possible to accurately determine the ion species dissolved in the solution.

Embodiment 2. FIG.
3 is a block diagram showing a metal ion measuring apparatus according to Embodiment 2 of the present invention. FIG. 3 (a) is a cross-sectional block diagram, and FIG. 3 (b) is a top block diagram. The measuring apparatus according to the second embodiment has an apparatus main body 100 installed in a flow path 2 through which a solution 1 flows, and can measure metal ions in the solution online. In addition, the measuring apparatus according to the second embodiment measures the amount of minute deformation of the working electrode with high sensitivity using optical interference fringes. In the figure, the apparatus main body 100 is installed so that the flow path 2 through which the solution 1 flows and the flow path 2 a provided in the apparatus main body 100 communicate with each other. A working electrode 3 is installed on the upper surface of the flow path 2a, and a reference surface 4 made of a glass substrate is installed on the upper surface of the working electrode 3 with a predetermined distance from the working electrode 3. The working electrode 3 is obtained by forming a metal electrode 32 on a glass substrate (for example, a thickness of 0.1 mm) 31, and the metal electrode 32 is obtained by forming an Au film by vapor deposition, for example. Further, the surface of the glass substrate 31 opposite to the metal electrode 32 forms a reflecting surface. The working electrode 3 is placed so that the metal electrode 32 faces the side where the solution 1 flows, and the working electrode 3 is placed so that the metal electrode 32 is in contact with the solution 1. Further, one end (one side) 3a of the working electrode 3 is fixed to the flow path 2a of the apparatus main body 100, and the other end (three sides) 3b is not fixed to the apparatus main body 100 but is a free end, and is perpendicular to the solution surface. It is possible to deform in the direction to do. The reference surface 4 is a glass substrate whose surface opposite to the working electrode 3 is a reflecting surface, and is fixed to the plate apparatus main body 100 so that it does not deform. Further, a counter electrode 5 made of platinum and a reference electrode (Ag / AgCl electrode) 6 are installed in the flow path 2 a, and a current flows from the potentiostat 10 between the working electrode 3 and the counter electrode 5. The reference electrode 6 is for measuring the potential of the working electrode 3, and the potentiostat 10 controls the potential of the working electrode 3 and detects the current flowing corresponding to the potential of the working electrode 3. A laser interferometer 7 is installed above the reference surface 4. The laser interferometer 7 includes, for example, a laser light source 71, a half mirror 72, a lens 73, and a CCD camera 74, and the CCD camera 74 detects reflected light 76 of the laser light 75 emitted from the laser light source 71. Thus, when the working electrode 3 is deformed, an interference fringe 70 generated between the reference surface 4 and the working electrode 3 is detected.

Next, a method for measuring the type and concentration of metal ions by the metal ion measuring apparatus according to this embodiment will be described.
First, a current is applied by applying a voltage between the working electrode 3 and the counter electrode 5. At that time, the voltage to be applied is changed, and the potential to the working electrode 3 is scanned from + 1V to -2V. The current spectrum obtained by potential scanning is measured to identify the ion species present in the water.
Next, the potential of the working electrode is maintained at the reduction potential of the metal ion whose concentration is to be measured, for example, -0.126 V of Pb (SHE: standard hydrogen electrode reference). A reduction reaction occurs at the interface between the working electrode 3 and the solution 1, a Pb film is formed on the surface of the metal electrode 32, and the glass substrate 31 is deformed by stress.
Due to this deformation, an interference fringe 70 as shown in FIG. 3B is generated between the reference surface 4 and the glass substrate 31. The observation area A of the CCD camera 74 is set as a portion where the interference fringe 70 is generated, By measuring the width of the observed interference fringes, the deformation amount of the working electrode 3 can be calculated. A semiconductor laser having a wavelength of 650 nm was used for measuring the interference fringes. The theoretical resolution for measuring the deformation of the electrode using interference fringes is about 6 nm.
Further, the time differential value of the deformation amount of the working electrode 3 is calculated by measuring the time variation of the width of the interference fringe, the calculated value, the time differential value of the minute deformation amount of the electrode measured in advance, and the ion concentration in the solution. The metal ion concentration in the solution can be determined by matching the calibration curve representing the relationship between Thereby, the metal ion concentration in the solution can be determined online with high sensitivity.

  In the case of the measuring apparatus of the present embodiment, since the measurement of the deformation amount of the electrode is performed outside the solution, the measurement is performed even when the light absorption of the solution is large or the solution is altered by light. It was possible.

  In the above embodiment, one end (one side) 3a of the working electrode 3 is fixed to the apparatus main body 100, and the remaining three sides are free ends, but two opposite sides are fixed to the apparatus main body 100, The other two sides may be configured as free ends. In this case, the interference fringes that appear appear symmetrical, but the width of the interference fringes may be measured in the same manner.

Embodiment 3 FIG.
FIG. 4 is a block diagram showing a metal ion measuring apparatus according to Embodiment 3 of the present invention. FIG. 4 (a) is a cross-sectional block diagram, and FIG. 4 (b) is a top block diagram. The measuring apparatus according to the third embodiment is configured to install the apparatus main body 100 in the flow path 2 through which the solution 1 flows, and can measure metal ions in the solution online. In addition, the measuring apparatus according to the third embodiment irradiates the working electrode with laser light, and measures the amount of minute deformation of the working electrode with high sensitivity using the displacement of the laser reflected light caused by bending of the working electrode. In the figure, the apparatus main body 100 is installed so that the flow path 2 through which the solution 1 flows and the flow path 2 a provided in the apparatus main body 100 communicate with each other. A hole 2b is formed in the upper surface of the flow path 2a. An Au thin film is formed as a metal electrode 32 on a thin glass substrate 31 (thickness 0.1 mm), and this is used as a working electrode 3. One end 3a of the glass substrate 31 provided with the working electrode 3 is fixed to the bottom surface of the flow path 2a, and the other end 3b of the glass substrate 31 is outside the flow path 2a through the hole 2b and forms a free end. That is, one end of the glass substrate 31 is immersed in the solution, and the other end is installed outside the solution. Further, a counter electrode 5 made of platinum and a reference electrode (Ag / AgCl electrode) 6 are installed in the flow path 2 a, and a current flows from the potentiostat 10 between the working electrode 3 and the counter electrode 5. The reference electrode 6 is for measuring the potential of the working electrode 3, and the potentiostat 10 controls the potential of the working electrode 3 and detects the current flowing corresponding to the potential of the working electrode 3. A metal (Ti) thin film 33 is deposited on the substrate near the free end of the glass substrate 31 so as to be a laser beam reflecting mirror. A laser light source (semiconductor laser) 71 is deposited on the metal thin film 33. The laser beam 75 is irradiated using The laser beam 75 is reflected on the surface of the metal thin film 33, and a light receiver (CCD camera) 74 is installed so that the reflected laser beam 76 enters the light receiving element.

Next, a method for measuring the type and concentration of metal ions by the metal ion measuring apparatus according to this embodiment will be described.
First, a current is applied by applying a voltage between the working electrode 3 and the counter electrode 5. At that time, the voltage to be applied is changed, and the potential to the working electrode 3 is scanned from + 1V to -2V. The current spectrum obtained by potential scanning is measured to identify the ion species present in the water.
Next, when the potential of the working electrode 3 is kept at the reduction deposition potential of the dissolved metal ions, a metal film is formed on the working electrode 3, whereby the glass substrate 31 is deformed by the stress generated on the working electrode side. As a result, the optical path of the reflected laser beam 76 changes, and the position of the laser spot on the light receiver 74 moves. Since the reflected light 76 input to the light receiver 74 moves on the light receiver 74 with the deformation amount of the glass substrate 31 enlarged, a minute deformation of the glass substrate 31 can be detected with high sensitivity. That is, by measuring the time change of the spot moving distance of the reflected laser beam, the time differential value of the deformation amount of the working electrode 3 is calculated, the calculated value, the time differential value of the micro deformation amount of the electrode measured in advance, and the solution The metal ion concentration in the solution can be determined by associating with a calibration curve representing the relationship with the ion concentration in the solution. Thereby, the metal ion concentration in the solution can be determined online with high sensitivity.

  Also, in the measurement apparatus of the present embodiment, since the measurement of the deformation amount of the electrode is all performed outside the solution, the measurement can be performed even when the light absorption of the solution is large or the solution is altered by light. It was possible.

Embodiment 4 FIG.
FIG. 5 is a block diagram showing a metal ion measuring apparatus according to Embodiment 4 of the present invention. FIG. 5 (a) is a cross-sectional block diagram, and FIG. 5 (b) is a top block diagram. The measurement apparatus according to the fourth embodiment is configured to install the apparatus main body 100 in the flow path 2 through which the solution 1 flows, and can measure metal ions in the solution online. In addition, the measuring apparatus according to the fourth embodiment has an optical fiber installed along the working electrode, detects a change in the optical path of the laser beam due to bending of the working electrode, and measures the amount of minute deformation of the working electrode with high sensitivity. It is. In the figure, the apparatus main body 100 is installed so that the flow path 2 through which the solution 1 flows and the flow path 2 a provided in the apparatus main body 100 communicate with each other. Further, holes 2b and 2c are formed in the upper surface and the bottom surface of the flow path 2a, respectively, and the end 3a of the glass substrate 31 constituting the working electrode 3 is fixed to the bottom of the flow path 2a as in the third embodiment. The other end 3b which is immersed in the solution and forms a free end is placed outside the solution. The glass substrate 31 is provided with a metal electrode 32 at least on the surface of the portion immersed in the solution. Further, a counter electrode 5 made of platinum and a reference electrode (Ag / AgCl electrode) 6 are installed in the flow path 2 a, and a current flows from the potentiostat 10 between the working electrode 3 and the counter electrode 5. The reference electrode 6 is for measuring the potential of the working electrode 3, and the potentiostat 10 controls the potential of the working electrode 3 and detects the current flowing corresponding to the potential of the working electrode 3. Further, an optical fiber 77 is installed along the holes 2b and 2c provided in the upper surface and the bottom of the flow path 2a and along the one end 3a to the other end 3b of the glass substrate 31. The laser light incident from the lower end portion of the optical fiber 77 is emitted from the upper end portion of the optical fiber 77 and is input to the light receiver 74 through the lens 78. An aperture 79 having a pinhole is installed between them.

Next, a method for measuring the type and concentration of metal ions by the metal ion measuring apparatus according to this embodiment will be described.
First, a current is applied by applying a voltage between the working electrode 3 and the counter electrode 5. At that time, the voltage to be applied is changed, and the potential to the working electrode 3 is scanned from + 1V to -2V. The current spectrum obtained by potential scanning is measured to identify the ion species present in the water.
Next, when the potential of the working electrode 3 is kept at the reduction deposition potential of the dissolved metal ions, a metal film is formed on the working electrode 3, whereby the glass substrate 31 is deformed by the stress generated on the working electrode side. As a result, the optical fiber 77 provided along the glass substrate 31 is bent. Since the aperture 78 is provided between the optical fiber end face on the output side and the light receiver 74, the amount of light input to the light receiver 74 decreases when the deformation amount of the optical fiber 77 is large. By measuring the temporal change in the amount of light detected by the light receiver 74, the time differential value of the deformation amount of the working electrode 3 is calculated, and the calculated value, the time differential value of the micro deformation amount of the electrode measured in advance, and the solution The metal ion concentration in the solution can be determined by associating the calibration curve representing the relationship with the ion concentration. Thereby, the metal ion concentration in the solution can be determined online with high sensitivity.

  Also, in the measurement apparatus of the present embodiment, since the measurement of the deformation amount of the electrode is all performed outside the solution, the measurement can be performed even when the light absorption of the solution is large or the solution is altered by light. It was possible.

Embodiment 5 FIG.
6A and 6B are configuration diagrams showing a metal ion measuring apparatus according to Embodiment 5 of the present invention. FIG. 6A is a cross-sectional configuration diagram, and FIG. 6B is a top configuration diagram. The measuring apparatus according to the fifth embodiment is configured to install the apparatus main body 100 in the flow path 2 through which the solution 1 flows, and can measure metal ions in the solution online. In addition, the measuring apparatus according to the fifth embodiment measures a minute deformation amount of the working electrode with high sensitivity using a piezoelectric element. In the figure, the apparatus main body 100 is installed so that the flow path 2 through which the solution 1 flows and the flow path 2 a provided in the apparatus main body 100 communicate with each other. A working electrode 3 is provided on the upper surface of the flow path 2a. The working electrode 3 is obtained by forming a metal electrode 32 on a glass substrate (for example, a thickness of 0.1 mm) 31, and the metal electrode 32 is obtained by forming an Au film by vapor deposition, for example. The working electrode 3 is installed so that the metal electrode 32 faces the solution 1 flow side, and the metal electrode 32 is in contact with the solution 1. The working electrode 3 has one end 3a fixed to the flow path 2a of the apparatus main body 100 and the other end 3b not fixed to the apparatus main body 100 but a free end, and can be deformed in a direction perpendicular to the solution surface. It has become. Further, a piezo element 80 is affixed on the glass substrate 31 opposite to the side in contact with the solution 1, and the piezo element 80 is fixed to a support beam 81 coupled to the flow path 2a. The structure is sandwiched by 81. When the working electrode 3 is deformed, stress is applied to the piezo element 80, and the piezo element 80 is distorted according to the stress. The minute voltage detector 82 provided in the piezo element 80 outputs the distortion amount of the piezo element 80 as a voltage. Further, a counter electrode 5 made of platinum and a reference electrode (Ag / AgCl electrode) 6 are installed in the flow path 2 a, and a current flows from the potentiostat 10 between the working electrode 3 and the counter electrode 5. The reference electrode 6 is for measuring the potential of the working electrode 3, and the potentiostat 10 controls the potential of the working electrode 3 and detects the current flowing corresponding to the potential of the working electrode 3.

Next, a method for measuring the type and concentration of metal ions by the metal ion measuring apparatus according to this embodiment will be described.
First, a current is applied by applying a voltage between the working electrode 3 and the counter electrode 5. At that time, the voltage to be applied is changed, and the potential to the working electrode 3 is scanned from + 1V to -2V. The current spectrum obtained by potential scanning is measured to identify the ion species present in the water.
Next, when the potential of the working electrode 3 is kept at the reduction deposition potential of the dissolved metal ions, a metal film is formed on the working electrode 3, whereby the glass substrate 31 is deformed by the stress generated on the working electrode side. As a result, the piezo element 80 is distorted. By detecting the distortion amount of the piezo element 30 as a voltage value by the minute voltage detection device 82, the deformation amount of the working electrode 3 can be measured with high sensitivity. By measuring the time variation of the detected voltage value, the time differential value of the deformation amount of the working electrode 3 is calculated, and the calculated value, the time differential value of the micro deformation amount of the electrode measured in advance, and the ion concentration in the solution The metal ion concentration in the solution can be determined by matching the calibration curve representing the relationship between Thereby, the metal ion concentration in the solution can be determined online with high sensitivity.

  Also, in the measurement apparatus of the present embodiment, since the measurement of the deformation amount of the electrode is all performed outside the solution, the measurement can be performed even when the light absorption of the solution is large or the solution is altered by light. It was possible.

In the above embodiment, the piezo element 80 is attached to the glass substrate 31. However, the metal electrode 32 may be formed on the piezo element 80 itself, and the same effect is obtained.
In the above embodiment, one end (one side) 3a of the working electrode 3 is fixed to the apparatus main body 100, and the remaining three sides are free ends, but two opposite sides are fixed to the apparatus main body 100. The other two sides may be configured as free ends. In this case, the distortion amount of the piezo element 80 is smaller than that of the above embodiment, but the deformation of the working electrode 3 is similarly performed if the distortion amount of the piezo element 30 is within a range that can be detected as a voltage value by the minute voltage detector 82. The amount can be measured.

Embodiment 6 FIG.
The measuring apparatus according to the sixth embodiment measures the amount of minute deformation of the working electrode 3 with high sensitivity from the minute change in capacitance between the glass substrate 31 and the support beam 81 in FIG. The apparatus configuration is the same as in FIG. 6, but there is no piezo element 80. Instead, a metal electrode (counter electrode) is applied to the surface of the support beam 81 facing the working electrode 3, and the counter electrode and working electrode are also provided. 3 is provided with a detector for measuring the capacitance between them.
In measuring the concentration of the metal ions, the time differential value of the deformation amount of the working electrode 3 is calculated by measuring the time change of the capacitance value to be detected, and in the same manner as in the fifth embodiment. The metal ion concentration in the solution can be determined.
Thereby, the metal ion concentration in the solution can be determined online with high sensitivity.

  In each of the above embodiments, the measurement apparatus is installed in the flow path 2 through which the solution 1 flows to measure the metal ion species and the metal ion concentration online. However, the solution 1 is separated in the cell. It may be measured. In that case, the working electrode having the same configuration as that of each of the above embodiments is provided in the cell, and the minute deformation amount of the glass substrate on which the above working electrode is provided, the interference fringes, the displacement of the laser light, as in each of the embodiments. It is possible to measure the ion concentration with high sensitivity by measuring the piezoelectric element, change in capacitance, and the like.

It is a flowchart which shows the measuring method of the metal ion by Embodiment 1 of this invention. The conceptual diagram of the current spectrum by the potential scan to the working electrode concerning Embodiment 1 of this invention is shown. It is a block diagram which shows the measuring apparatus of the metal ion by Embodiment 2 of this invention. It is a block diagram which shows the measuring apparatus of the metal ion by Embodiment 3 of this invention. It is a block diagram which shows the measuring apparatus of the metal ion by Embodiment 4 of this invention. It is a block diagram which shows the measuring apparatus of the metal ion by Embodiment 5 of this invention.

Explanation of symbols

1 Solution, 2, 2a channel, 2b, 2c hole, 3 working electrode, 31 glass substrate, 32 metal electrode, 33 metal thin film, 4 reference plane, 5 counter electrode, 6 reference electrode, 7 laser interferometer, 10 potentiostat, 70 Interference fringes, 71 Laser light source, 72 Half mirror, 73, 78 Lens, 74 CCD camera, 75 Laser light, 76 Reflected light, 77 Optical fiber, 79 Aperture, 80 Piezo element, 81 Support beam, 82 Micro voltage detector, 100 Device body.

Claims (7)

Step of immersing the working electrode and the counter electrode in the measurement solution, passing a current between the working electrode and the counter electrode, and measuring the potential-current curve by the electrochemical reaction to identify the type of metal ion in the solution A step of maintaining the potential of the working electrode at the reduction potential of the specified metal ion, a step of detecting a minute deformation amount of the working electrode generated by the metal film formed on the working electrode, and the minute A method for measuring metal ions, comprising a step of determining a metal ion concentration in a solution based on a deformation amount. An apparatus main body through which the solution passes or contains the solution, a working electrode and a counter electrode arranged so as to come into contact with the solution in the apparatus main body, control means for controlling the potential of the working electrode, A potential-current detecting means for detecting a current flowing corresponding to the potential, and a deformation amount detecting means for detecting a deformation amount of the working electrode deformed by a metal film formed on an electrode surface of the working electrode by an electrochemical reaction. A metal ion measuring apparatus comprising: The deformation amount detecting means includes a reference surface that is disposed to face the working electrode at a predetermined interval, and a light interference fringe detecting means that detects a light interference fringe between the working electrode and the reference surface. The metal ion measuring apparatus according to claim 2. One end of the working electrode is fixed to the apparatus main body, the other end is a free end, the deformation amount detecting means is a laser irradiation means for irradiating a laser beam near the other end of the working electrode, and the other end of the working electrode. 3. The metal ion measuring apparatus according to claim 2, comprising a light detecting means for detecting the position of the reflected laser light from the vicinity. One end of the working electrode is fixed to the apparatus main body, the other end is a free end, and the deformation detection means is provided along one end from the other end of the working electrode, and is incident from one end side of the working electrode. 3. The metal ion measuring apparatus according to claim 2, comprising: an optical fiber that emits light from the other end side; and a detection means that detects a change in the optical path of light emitted from the optical fiber. The deformation amount detection means is fixed to the apparatus main body and is provided so as to be in contact with the surface of the working electrode, and is composed of a piezoelectric element that converts the deformation amount of the working electrode into a voltage and outputs the voltage. The metal ion measuring device according to claim 2. The deformation amount detecting means is composed of a counter electrode disposed to face the working electrode at a predetermined interval, and a detecting means for detecting a capacitance between the working electrode and the counter electrode. The metal ion measuring device according to claim 2.

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