JP5714433B2 - Electrolytic cell - Google Patents

Description

  The present invention relates to an electrolysis technique using a redox reaction.

  The spectroelectrochemical method is a method in which spectroscopic methods and electrochemical methods are combined, and the spectroscopic characteristics before and after electrolysis can be measured while applying a potential to the working electrode for electrolysis. Usually, since it takes time to electrolyze the electrode reactive substance, spectroelectrochemical measurement is performed by inserting an electrode into a thin-layer cell and electrolyzing only the electrode reactive substance in the vicinity of the electrode. (For example, Non-Patent Document 1).

  In the spectroscopic method, the absorbance is defined based on Lambert-Beer's law. That is, the absorbance is the product of the molar extinction coefficient, the sample concentration, and the optical path length. The molar extinction coefficient is a coefficient specific to the sample. Since the optical path length of the thin-layer cell is as short as about 0.1 mm to 1.0 mm, the sample concentration must be increased in order to obtain high absorbance. Furthermore, since the optical path length is short, it is not suitable for a sample having a small molar extinction coefficient. Also, because the sample cannot be agitated during electrolysis, the electrolysis product must be concentrated on the optical path of the cell. Therefore, it is necessary to install the working electrode on the optical path of the cell, and the structure of the electrode is also restricted, such as using a net-like or light transmissive electrode that does not obstruct the optical path.

  In the electrochemistry field, bulk electrolysis technology using redox reactions is not only a physicochemical viewpoint such as equilibrium theory and reaction mechanism theory, but an analytical chemistry viewpoint such as high-precision absolute quantification, as well as organic and inorganic synthetic chemistry. It is extremely useful also from a viewpoint.

  When performing bulk electrolysis, the anode side and the cathode side are separated from each other (or liquid junction) to prevent re-reduction reaction of the anode reaction product at the cathode (or re-oxidation reaction of the cathode reaction product at the anode). It is said that it must be done separately. When such a diaphragm is added to the structure of the electrolysis cell, it cannot be installed in the apparatus due to restrictions on the dimensions of the electrolysis cell, or even if it can be applied, an apparatus that simultaneously measures the product online (for example, various spectroscopic methods) May be difficult to use together. Therefore, a non-diaphragm bulk electrolysis method has been proposed in which the electrode reaction of the counter electrode is mainly attributed to the oxidation-reduction reaction of the solvent and does not require a diaphragm (for example, Patent Document 1 and Non-Patent Document 2).

  In the diaphragmless bulk electrolysis method, the area of the working electrode relative to the counter electrode is relatively increased under the action of a potential control device (potentiostat), thereby reoxidizing (or re-reducing) the electrode-reactive substance generated at the working electrode. ) Is negligibly small. At this time, oxidation or reduction of the solvent (supporting electrolyte) proceeds at the counter electrode, and reoxidation (or rereduction) of the target substance is remarkably suppressed. As the electrolytic reaction proceeds, the current in the working electrode decreases, so the potential of the counter electrode approaches the potential of the working electrode. The non-diaphragm bulk electrolysis method is being widely used as shown below, for example.

[Electrochemical synthesis]
Organic electrosynthesis using bulk electrolysis technology does not require an organic solvent as in the case of conventional organic synthesis (ie, no organic solvent or other waste is generated). Has been. In addition, by setting the electrolysis conditions as appropriate, it is possible to cause a specific oxidation-reduction reaction according to the electrolysis conditions (high selectivity). (For example, Non-Patent Documents 3 and 4).

[Electrochemical analysis method]
The standard redox potential (E ⁰ ) indicates the equilibrium potential of the electrode during the redox reaction (redox reaction occurring on the electrode surface of the electrolytic cell) in the standard state (25 ° C., 1 atm). Are treated as extremely important thermodynamic parameters and are generally expressed with reference to a standard hydrogen electrode (SHE) (for example, Non-Patent Document 5).

For example, when the oxidant in the electrolyte is O and the reductant is R, the electrode potential (E) when the electron transfer equilibrium “O + ne ⁻ = R” is established between the oxidant O and the reductant R is: Using the standard oxidation-reduction potential (E ⁰ ), it can be expressed by the Nernst equation shown in the following equation (1).

In the symbol of the formula (1), R is a gas constant (8.314 J · mol ⁻¹ · K ⁻¹ ), F is a Faraday constant (96500 C · mol ⁻¹ ), T is an absolute temperature (at 25 ° C., 298.15K), [O] represents the oxidant concentration, and [R] represents the reductant concentration.

E = E ⁰ + (RT / nF) ln ([O] / [R]) (1)
From the equation (1), when the ratio of the activity of the oxidant O and the reductant R (molar concentration ratio in the case of a solution; hereinafter referred to as [O] / [R]) is 1, theoretically “ E = E ⁰ ”holds.

Here, the electrode potential E obtained by actual measurement rather than E ^0, it is known that its is E ⁰ to approximate the formula weight potential (E ⁰ '). This formula quantity potential E ⁰ ′ can be obtained, for example, by measuring [O] / [R] at various electrode potentials and reading the potential when “[O] / [R] = 1”. It is.

  The above [O] / [R] is difficult to measure simply by a configuration using a bulk electrolysis cell (in situ), but the analyte (redox species) absorbs light ( When the absorption spectrum changes during the oxidation-reduction reaction), it can be determined relatively easily by spectroscopy. Therefore, a spectroelectrochemical method in which a bulk electrolysis technique and a spectroscopic method are integrated is applied. As the spectroelectrochemical method, a method using a light-transmitting thin layer cell (OTTTL) method or a specular reflection method is known. (For example, Patent Document 1, Non-Patent Documents 4, 6, and 7).

FIGS. 21A and 21B are schematic explanatory views showing an example of a front view of an electrolysis cell and a side view of the electrolysis cell used in the light-transmitting thin-layer cell method, respectively. 21A and 21B, the working electrode 81 of the thin cell 80 has a transparent electrode 83 interposed between a pair of substantially flat glass members (members made of quartz glass) 82a and 82b. At the same time, a gap 81a is formed through a spacer (dotted line portion in the figure) 84. As the transparent electrode 83, a mini grid (net) made of gold, platinum, or the like, a thin film in which a metal is deposited on a quartz glass substrate, or a conductive oxide thin film made of In ₂ O ₃ or SnO ₂ is used.

  The electrolyte solution 85 that holds the electrolyte solution holds the electrolyte solution to be measured. Then, a part of the working electrode 81 is immersed in the electrolytic solution held in the electrolytic solution container 85, and the counter electrode 86 and the reference electrode 87 are immersed therein. Into the gap 81a of the working electrode 81 immersed in the electrolytic solution, the electrolytic solution enters (through capillary action) through the immersed portion.

As shown in FIGS. 21A and 21B, according to the light-transmitting thin-layer cell method to which the bulk electrolysis technique is applied, various electrodes are obtained by spectroscopic methods for the electrolytic solution containing redox species that absorb light. By measuring [O] / [R] with the potential, it is possible to obtain the potential when “[O] / [R] = 1”, that is, the formula potential E ⁰ ′.

[Electrochemical analysis method for biological materials]
The oxidation-reduction potential E ⁰ ′ is handled as one of the important parameters in analyzing the function of the biological material and the like, but it is not always easy to obtain reliable data.

When protein (P) is analyzed using a general electrolytic cell, transfer of electrons between the protein and the electrode of the electrolytic cell is unlikely to occur, and equilibration by direct electrolysis is practically impossible. For this reason, low-molecular substances (hereinafter referred to as mediators (M; M _ox , M _red )) having high reactivity in the working electrode and protein (P; P _ox , P _red ) of the electrolytic cell are interposed in the electrolytic solution. And a method of titrating the mediator with an appropriate reducing agent or oxidizing agent has been employed.

In such a titration method, the mediator and protein are in an equilibrium state by the reaction shown in the following formula (2), so that the equilibrium potential (E) of the mediator can be measured by potentiometry. In the formula (2), “M _ox ” is an oxidizing mediator concentration, “M _red ” is a reducing mediator concentration, [P _ox ] is an oxidizing protein concentration, and [P _red ] is a reducing protein. It shall indicate the concentration.

In addition, the equilibrium potential (E) of the mediator is measured as described above, and at the same time, the concentration ratio of the redox substance in the protein (hereinafter referred to as [P _ox ] / [P _red ]) is detected by spectroscopy.

Then, based on the following formula (3), it is possible to indirectly obtain the formula potential E ⁰ ′ of the protein. In the formula (3), n _M and n _P indicate the number of electrons of the mediator and the number of electrons of the protein, respectively, which changed when one molecule of the mediator or protein reacted.
E = E ⁰ ′ (RT / n _M F) ln ([O] / [R])
_{^{= E 0 'P + (RT}} / n P F) ln ([P ox] / [P red]) ... (3)
When the titration method as described above is applied, it is necessary to pay attention to side reactions between the titration reagent and the target substance, volume correction by titration, suppression of the reaction between the reducing agent and oxygen, and the like. In addition to taking a long time for the titration system to reach equilibrium, it is necessary to consider what equilibrium is detected by the potential.

On the other hand, when a bulk electrolysis technique is applied instead of using a titration reagent, it is possible in principle to perform bulk electrolysis of the mediator with an electrode and measure [P _ox ] / [P _red ]. It is also easy to solve the problem in the case of using a titration reagent (for example, Non-Patent Document 8).

JP-A-2005-76116

“Spectroelectrochemical measurement system”, [online], B.S., Ltd., [Search June 1, 2011], Internet <URL: http://www.basj.com/1459.html> Satoshi Kuriyama, 5 others, “Proposal of Total Electrolysis Method of Non-diaphragm and Its Spectroelectrochemical Application”, Electrochemistry, 2004, Vol. 72, No. 7, p. 484 “5th Edition Electrochemical Handbook”, Maruzen, p. 405 Toshiyuki Ohtsuki, 2 other people, “Basic Electrochemistry”, Chemistry Doujin, 128, p. 129 The Electrochemical Society, “Electrochemical Measurement Manual Basics”, Maruzen, p. 13 “The Chemistry of Electron Transfer—Introduction to Electrochemistry” edited by the Chemical Society of Japan, Asakura Shoten, p. 69 The Electrochemical Society, “Electrochemical Measurement Manual Practice”, Maruzen, p. 46 Electrochemical Society Kansai Branch “28th Electrochemical Workshop”, 1998, Maruzen, p. 57 Chemical Engineering Handbook (6th revised edition), Maruzen, p. 424, p. 443

  As described above, when a thin layer cell is used to improve the electrolysis efficiency, the optical path length is short, so that the absorbance becomes small, and it becomes difficult to measure a substance having a small molar extinction coefficient. In addition, since the electrolyte solution cannot be stirred in the thin-layer cell, there is a concern that total electrolysis cannot be performed and analysis accuracy as coulometry is lowered.

  On the other hand, if a cell with a long optical path length is used to enable stirring of the electrolytic solution, the absorbance value can be increased and the measurement accuracy of a substance having a small molar extinction coefficient can be expected to be increased, but the amount of electrolytic solution is large. As a result, the time required for electrolysis becomes longer, and there is a concern that the measurement accuracy may be lowered due to the influence of fluctuations in measurement conditions including temperature fluctuations.

  In view of the above circumstances, an object of the present invention is to provide an electrolytic cell, an electrochemical synthesis method, and an electrochemical analysis method that contribute to improvement in accuracy or efficiency of synthesis or analysis.

  In the electrolytic cell of the present invention that achieves the above object, an electrolytic solution container having at least a pair of side surfaces facing each other and a working electrode immersed in the electrolytic solution in the electrolytic solution container are fixed, It is characterized by having a frame body inserted in the electrolytic solution container, a stirring means for stirring the electrolytic solution, a counter electrode immersed in the electrolytic solution, and a reference electrode.

  In addition, the electrochemical synthesis method of the present invention that achieves the above object includes immersing at least the working electrode, the counter electrode, and the reference electrode in an electrolytic solution container holding an electrolytic solution containing a redox species, The liquid is stirred at a stirring speed of 1000 rpm or higher or a stirring Reynolds number of 950 or higher via a stirring means, and a potential is applied to the working electrode to synthesize the redox species.

  In addition, the electrochemical analysis method of the present invention that achieves the above object includes immersing at least a working electrode, a counter electrode, and a reference electrode in a light-transmitting electrolytic solution container holding an electrolytic solution containing an object to be analyzed. The electrolytic solution is stirred at a stirring speed of 1000 rpm or more or a stirring Reynolds number of 950 or more through a stirring means, and a potential is applied to the working electrode to detect a change in current of the working electrode. The method is characterized in that the change in absorbance of the electrolytic solution is calculated by a method.

  According to the above invention, it is possible to provide an electrolysis cell that contributes to improvement in accuracy and efficiency of synthesis or analysis. In addition, in the electrochemical synthesis method and the electrochemical analysis method, it can contribute to improvement in accuracy or efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing which shows an example of the electrolytic cell which concerns on Embodiment 1 of this invention, (A) Electrolytic cell front view, (B) Electrolytic cell AA arrow line view, (C) System structure provided with an electrolytic cell FIG. It is a schematic explanatory drawing which shows an example of the electrolytic cell which concerns on Embodiment 1 of this invention, (A) It is explanatory drawing of a cell structure, (B) It is explanatory drawing of the working electrode fixed frame body provided with a working electrode. It is a characteristic view which shows the change with respect to the reaction time of the logarithm of the electric current in the working electrode of Example 1. It is a characteristic view which shows the change with respect to the reaction time of the electric current in the working electrode of Example 1. It is a characteristic view which shows the change with respect to the reaction time of the light absorbency in the electrolytic cell of Example 1. It is a characteristic view which shows the change with respect to the reaction time of the logarithm of the electric current in the working electrode of Example 2. It is a characteristic view which shows the change with respect to the reaction time of the electric current in the working electrode of Example 2. It is a characteristic view which shows the relationship between stirring Re number and reaction rate constant p. It is a characteristic view which shows the change with respect to the reaction time of the light absorbency in the electrolytic cell of Example 2. It is a characteristic view which shows the change with respect to the reaction time of the logarithm of the electric current in the working electrode of Example 3. It is a characteristic view which shows the change with respect to the reaction time of the electric current in the working electrode of Example 3. It is a characteristic view which shows the change with respect to the reaction time of the light absorbency in the electrolytic cell of Example 3. It is a characteristic view which shows the change with respect to the reaction time of the electric current in the working electrode of Example 4. It is a characteristic view which shows the change with respect to the reaction time of the light absorbency in the electrolytic cell of Example 4. 6 is an absorption spectrum characteristic diagram in the electrolytic cell of Example 5. FIG. 10 is a Nernst plot diagram in Example 5. FIG. It is a schematic explanatory drawing which shows an example of the electrolytic cell which concerns on Embodiment 2 of this invention. It is a characteristic view which shows the change with respect to the reaction time of the electric current in the working electrode of Example 6. It is a characteristic view which shows the change with respect to the reaction time of the light absorbency in the electrolytic cell of Example 6. 6 is an absorption spectrum characteristic diagram in the electrolytic cell of Example 7. FIG. It is a schematic explanatory drawing which shows an example of a thin layer type | mold spectroelectrochemical cell, (A) Cell front view, (B) Cell side view.

  An electrolytic cell, an electrochemical synthesis method, and an electrochemical analysis method according to an embodiment of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
1A and 1B are schematic explanatory views showing a side view through which a light beam of an electrolytic cell in an embodiment of the present invention is transmitted and a view taken along the line AA of the electrolytic cell, respectively.

  As shown in FIG. 1A, the electrolysis cell 1 includes a light transmissive container 2, a stirrer 13, a working electrode 3, a working electrode fixing frame 4, a counter electrode 5, and a sealing member 9. Hereinafter, each component of the electrolytic cell 1 will be described.

[Light transmissive container 2]
The light transmissive container 2 is a bottomed cylindrical container having a substantially rectangular cross section, and at least a pair of opposed side surfaces of the light transmissive container 2 is made of a material that can transmit light used for measurement. It is made of a transparent material such as quartz. In the light transmissive container 2, an electrolytic solution 10 including an object to be synthesized and an object to be analyzed is held. The amount of the electrolyte solution 10 is required to be immersed in various electrodes, and is the same even in a stirring state in which the liquid level varies.

[Stirrer 13]
The stirrer 13 stirs the electrolytic solution 10 held in the light transmissive container 2. The stirrer 13 is rotated by a magnetic stirrer (not shown). The stirrer 13 is, for example, a bar magnet sealed with a fluororesin or the like, and has a long and narrow bowl-like shape such as a bar, octagonal bar, windmill blade, etc. It is properly used depending on the usage such as quantity. In the description of the embodiment of the present invention, a rod-shaped stirrer having excellent versatility is used, but stirrers having other shapes can also be applied.

[Working electrode 3]
The working electrode 3 is appropriately selected according to an object to be synthesized such as platinum, gold, and carbon, an object to be analyzed, and the electrolytic solution 10. The working electrode 3 is fixed to a working electrode fixing frame 4 which will be described later, and is immersed in the electrolytic solution 10. As shown in FIGS. 1A and 1B, when the working electrode 3 is a wire mesh of platinum or gold, the working electrode 3 is fixed by being wound around the working electrode fixing frame 4. The working electrode 3 is connected to a wiring such as a lead wire 3a as necessary.

[Working electrode fixing frame 4]
The working electrode fixing frame 4 is a substantially rectangular lattice-shaped frame that can be machined and is made of a chemical-resistant material (for example, peak resin or fluororesin). As shown in FIG. 2A, a rotating guide 4a of a stirrer 13 is formed on the bottom surface of the working electrode fixed frame 4, and the stirrer 13 rotates in the rotating guide 4a to stir the electrolyte solution 10. Is done.

  In addition, the amount of the electrolyte solution used for electrochemical synthesis or electrochemical analysis can be reduced by inserting the working electrode fixing frame 4 into the light transmissive container 2. Furthermore, by making the outer shape of the working electrode fixing frame 4 substantially equal to the inner shape of the light transmissive container 2, dead space in the light transmissive container 2 that is not affected by stirring can be reduced, Contributes to improving the accuracy and efficiency of synthesis or analysis. Further, as shown in FIG. 2B, when the fixing portion 4b for fixing the working electrode 3 is formed on the side surface of the working electrode fixing frame 4, the working electrode 3 provided on the working electrode fixing frame 4 becomes light transmissive. The working electrode fixing frame 4 is preferably not inserted into the conductive container 2 without hindering. The working electrode fixing frame 4 may be of any shape as long as it can fix the working electrode 3, and is shown in FIG. 2 having a rectangular frame shape on both the top and bottom of the working electrode fixing frame 4. The form is not limited.

  Further, the fixing portion 4b for fixing the working electrode 3 is not limited to the form shown in FIG. 2B, and the form for locking the working electrode 3 or the working electrode 3 between the working electrode fixing frame 4 is not limited. A form to be fitted may be used. Further, the position of the fixing portion 4b for fixing the working electrode 3 is not limited to the form shown in the drawing as long as it does not interfere with the optical path for measurement.

[Counter electrode 5]
As shown in FIG. 1A, the counter electrode 5 is provided on a sealing member 9 that seals the light transmissive container 2 in which the electrolytic solution 10 is held. The counter electrode 5 is provided such that the lower end portion of the counter electrode 5 is immersed in the electrolytic solution 10 when the sealing member 9 is provided in the light transmissive container 2. As the counter electrode 5, an electrode (platinum wire or carbon electrode) used in normal electrochemical measurement is used. The immersion area of the counter electrode 5 is set to be smaller than the immersion area of the working electrode 3.

[Sealing member 9]
The sealing member 9 is a member that seals the opening of the light transmissive container 2 and is made of a chemical-resistant material (for example, peak resin or fluororesin) that can be machined. In addition to the counter electrode 5, the sealing member 9 has an introduction pipe 7 for introducing a gas (argon gas, nitrogen gas, etc., hereinafter referred to as introduction gas) into the reference electrode 6 and the light transmissive container 2, A discharge pipe 8 for discharging the introduced gas introduced from the introduction pipe 7 is provided. A thin film 6 a made of ceramics or the like is provided at the tip of the reference electrode 6 in order to prevent contamination with the electrolytic solution 10.

  The distal end portion (introduction port) of the introduction tube 7 is immersed in the electrolytic solution 10 when the introduced gas is used for removing dissolved oxygen from the electrolytic solution 10 (hereinafter referred to as deaeration treatment), and the introduced gas is light-transmitting. When replacing with the gas phase in the container 2, it is preferably taken out from the electrolytic solution 10 (positioned above the water surface of the electrolytic solution 10).

[Analysis system configuration]
Using the electrolytic cell 1 shown in FIGS. 1 (A) and 1 (B), the system shown in FIG. 1 (C) is configured, and measurement by electrochemical measurement and spectroscopy is performed. In Examples 1 to 7 which will be described later, the same system configuration was used when performing analysis by constant potential electrolysis.

  As shown in FIG. 1C, the analysis system is configured by setting the electrolysis cell 1 in the measurement region (sample chamber) 15a of the spectrophotometer 15 and using the potentiostat 16a (and the function generator 16b) as a reference electrode. A predetermined potential with respect to 6 was applied to the working electrode 3. In this state, the light beam 15c from the light-emitting unit 15b is irradiated perpendicularly to the light-transmitting side surface of the light-transmitting container 2 of the electrolysis cell 1, and the transmitted light beam 15c is received by the light-receiving unit 15d and absorbed. Was calculated.

In addition, in the electrolysis cell 1 of Examples 1-5, if there is no notice in particular, the light transmissive container 2 includes a quartz cell manufactured by GL Sciences Inc. (double-faced quartz code 6210-11006, optical path length 10 mm), working electrode. In No. 3, a platinum net (φ0.07 mm, 100 mesh) made by Niraco was cut into a shape of 10 mm × 40 mm, thickness: 0.07 mm, surface area: 14.8 cm ² , and the platinum net was bent to 5 mm × 40 mm. Thickness: 0.14 mm, surface area: 14.8 cm ² , working electrode fixing frame 4 is made of peak resin, counter electrode 5 is covered with a platinum wire with a diameter of 1 mm, and only the tip of 1 mm is exposed. The reference electrode 6 is an Ag / AgCl electrode dipped in a saturated potassium chloride solution, the introduction tube 7 and the discharge tube 8 are glass tubes with a diameter of 1 mm, and the sealing member 9 is made of a peak resin. I used. Moreover, the immersion area of the counter electrode 5 was set to 0.039 cm < ² >, nitrogen gas was used for the deaeration process, and stirring of the electrolyte solution 10 was performed using the stirring bar 13 and the magnetic stirrer.

[Calculation of stirring Reynolds number of electrolyte]
In the constant potential electrolysis test, it is ideal that the electrolyte solution is in a completely mixed state with a uniform concentration so that no concentration distribution occurs in the electrolyte solution 10 in the electrolytic cell 1 as the reaction proceeds. However, when the stirrer 13 is used at a high speed rotation in order to obtain a high stirring effect, the rotation axis of the stirrer 13 is likely to be displaced, resulting in a stable rotation such as causing the step-out (jumping) of the stirrer 13. It becomes difficult. Therefore, in practice, it is important to suppress the number of rotations and maintain a stable mixed state. In reality, it is extremely difficult to form a completely mixed state. Therefore, in order to perform constant-potential electrolysis with improved accuracy and efficiency of analysis, the stirring state is quantified to obtain appropriate stirring conditions. It is necessary to set and test.

The following stirring Reynolds number (hereinafter referred to as stirring Re number) is known as an index for quantifying the stirring state. The stirring Reynolds number is used for the design of the stirring device, the scale-up of the stirring device, and the like.
Stirring Re number = ρ · n · d ² / μ
(Ρ: Density of electrolyte [kg / m ³ ], n: Rotation speed [rps] of stirrer 13, d: Blade span (length of stirrer 13) [m], μ: Viscosity of electrolyte [Pa]・ S])
In general, the fluid flow is laminar when the Reynolds number is small, but turns into turbulent flow when the Reynolds number is large. As numerical values, it is possible to roughly divide the state of flow roughly with a turbulent flow region of 4000 or more, a laminar flow region of 2100 or less, and a transition region therebetween.

  In the description of the examples of the present invention, the temperature of the electrolytic solution 10 was set to 20 ° C. when calculating the stirring Re number.

[Example 1] Relationship between stirring conditions and electrolysis rate Using two stirrers having different lengths, the influence of the stirring state on the electrolysis rate was evaluated. The shapes of the stirrers in Example 1 and Comparative Example 1 were both elongated and rod-shaped, and the following were used.
Example 1: GL Sciences MC-7 φ2mm × 7mm
Comparative Example 1: ASONE Co., Ltd. Microrotor D φ2mm × 5mm
The stirrer 13 is intended to stir the electrolytic solution 10, and the stirring state of the electrolytic solution 10 varies depending on the length and rotation speed of the stirrer 13. Therefore, in Example 1, in the rod-shaped stirrer 13, the diameter and rotation speed of the stirrer 13 were made the same, and the change in the electrolysis speed due to the difference in the length of the stirrer 13 was evaluated.

In Example 1, 0.1 mol / l phosphate buffer (pH 7.0) containing 0.25 mmol / l hexacyanoferrate (II) ion (Fe (CN) ₆ ⁴⁻ ) was used as sample S1 (electrolysis). As a liquid 10), 1.0 ml was held in the light transmissive container 2. In addition, the liquid amount of the sample S1 was set to a liquid level that would allow the various electrodes to be sufficiently immersed in the light-transmitting container 2 without being exposed to the atmosphere even while stirring.

Then, after degassing the sample S1 with nitrogen gas, the stirrer 13 (Example 1) is put into the light-transmitting container 2 and rotated at 1200 rpm (rpm = number of rotations per minute), and the electrolytic solution 10 Was stirred. Then, constant potential electrolysis is performed by applying a potential of 0.5 V (potential based on the reference electrode 6) to the working electrode 3 while flowing nitrogen gas into the sample S1 through the introduction tube 7. At the same time, the change of the current in the working electrode 3 with respect to the electrolytic reaction time was measured. Fe (CN) ₆ ⁴⁻ was oxidized to Fe (CN) ₆ ³⁻ by constant potential electrolysis. Further, during constant potential electrolysis, the time change of the absorbance of the electrolytic solution 10 was measured using a wavelength of 420 nm, which is an absorption peak wavelength capable of selectively specifying Fe (CN) ₆ ³⁻ .

  In addition, as a comparative example of Example 1, the stirrer according to Comparative Example 1 was used, and the other conditions were the same as those in Example 1 and constant potential electrolysis and absorptiometry were performed. Table 1 shows the measurement conditions and measurement results (reaction rate constant p, equilibrium absorbance and arrival time, total electrolysis time) of Example 1 and Comparative Example 1.

In Example 1 (and Comparative Example 1), Fe (CN) ₆ ⁴⁻ in the electrolytic solution 10 is produced by electrolysis, and Fe (CN) ₆ ³⁻ is generated by an oxidation reaction by a primary reaction. At this time, the current value i (t) in the electrolytic reaction time t (s) is expressed by the equation (4). In the equation (4), i (0) is a current value flowing through the working electrode 3 when t = 0, and p is a reaction rate constant (1 / s).
i (t) = i (0) exp (-pt) (4)
Moreover, the reaction rate constant p can be calculated | required by (5) Formula. In Equation (5), m is a mass transfer constant, A _w is the surface area of the working electrode (same in both Example 1 and Comparative Example 1), and V is the sample volume.
p = mA _w / V (5)
From the equation (4), the reaction rate constant p can be obtained by the equation (6).
p = ln [i (0) / i (t)] / t (6)
Note that i (0) is a current value that flows through the working electrode 3 when t = 0, but in reality, the concentration distribution of the electrode reactive substance is instantaneously in the vicinity of the working electrode 3 after the start of electrolysis. As a result, the current value in this initial state is measured as i (0). Therefore, the higher the stirring state, the thinner the diffusion layer near the working electrode 3 at the start of electrolysis. As a result, the higher the stirring state, the higher i (0) is measured.

  In the calculation of the reaction rate constant p in Example 1 (and Comparative Example 1), a logarithmic plot of the current value in the working electrode 3 is performed as shown in FIG. 3, and the reaction rate constant p is calculated from the slope of the straight line at t = 50 s. Asked.

FIG. 4 shows a current-time curve when constant potential electrolysis was performed under the conditions of Example 1 and Comparative Example 1. Since the current flowing through the working electrode 3 has a high Fe (CN) ₆ ⁴⁻ concentration in the sample S1 at the start of constant potential electrolysis, an oxidation current corresponding to this Fe (CN) ₆ ⁴⁻ concentration flows greatly. On the other hand, when the oxidation reaction proceeds, the Fe (CN) ₆ ⁴⁻ concentration in the sample S1 decreases, so that the oxidation current flowing through the working electrode 3 decreases. When Fe (CN) ₆ ^{4- is} almost oxidized to Fe (CN) ₆ ^3- , the current flowing through the working electrode 3 is called a residual current and does not become a current value of 0 mA, but is constant regardless of time. Value. When this residual current is measured, it is determined that the entire electrolytic state has been reached.

  As shown in FIG. 4, the total electrolysis time from the change in the current value with respect to the electrolysis time was t = 140 s in Example 1, and t = 190 s in Comparative Example 1.

In FIG. 5, the change with respect to reaction time of the light absorbency when performing constant potential electrolysis on the conditions of Example 1 and Comparative Example 1 is shown. When the total electrolysis is completed, the absorbance reaches an equilibrium absorbance at which the absorbance becomes a constant value. Therefore, the absorbance at 420 nm, which is an absorption wavelength capable of selectively specifying Fe (CN) ₆ ³⁻ in the electrolytic solution 10, with respect to the reaction time. It can be determined whether the entire electrolytic state has been reached also by the change.

  As shown in FIG. 5, the equilibrium absorbance was measured to be 0.22 in both Example 1 and Comparative Example 1, and the total electrolysis time from the change in absorbance over time was t = 140 s in Example 1 and in Comparative Example 1. t = 200 s, and Comparative Example 1 took about 1.5 times longer than Example 1 to complete electrolysis.

  As described above, when the electrolysis speed was compared by changing the stirring Re number only by changing the length of the stirrer 13, the higher the stirring Re number, the larger the reaction rate constant p, and the equilibrium with the total electrolysis time. It was found that the concentration arrival time was shortened and the electrolysis rate was increased.

  From the calculation formula of the stirring Re number, the length of the stirring bar 13 affects the stirring Re number. However, since the stirring bar 13 is rotated in the light transmissive container 2, the size of the light transmissive container 2 is determined. Limited. Therefore, the length of the stirrer 13 is selected to be shorter than the optical path length of the light transmissive container 2 (when the cross section of the light transmissive container 2 is square).

[Example 2] Relationship between stirring speed, number of stirring Re, and electrolysis speed The effect of the rotational speed of the stirrer 13 (φ2 mm × 7 mm) of Example 1 (hereinafter referred to as stirring speed) and the number of stirring Re on the electrolysis speed. evaluated. In Example 2, constant potential electrolysis and absorptiometry were performed by changing the stirring speed of the stirrer 13 to 800 rpm, 1000 rpm, 1200 rpm, and 1400 rpm. The conditions other than the stirring speed of the stirrer 13 and the number of stirring Re were the same as in Example 1.

  Table 2 shows measurement conditions and measurement results (reaction rate constant p, equilibrium absorbance and arrival time, total electrolysis time) at each stirring speed.

  As shown in Table 2, i (0) and reaction rate constant p increased with increasing stirring speed and Re Re number. In the calculation of the reaction rate constant p in Example 2, a logarithmic plot of the current value at the working electrode 3 was performed as shown in FIG. 6, and the reaction rate constant p was obtained from the slope of the straight line at t = 50 s.

  FIG. 7 shows a current-time curve when constant potential electrolysis is performed under conditions where the stirring speed of the stirrer 13 is different (conditions where the stirring Re number is different). The time required for the current flowing through the working electrode 3 to reach a total electrolysis state in which the current is constant regardless of the electrolysis reaction time (that is, the total electrolysis time) is an increase in the stirring Re number when the stirring Re number is 950 or less. However, when the number of stirring Re was 950 or more (equivalent to about 1000 rpm or more at the stirring speed), the result was almost constant.

  FIG. 8 shows a chart in which the relationship between the number of stirring Re and the reaction rate constant p is arranged. From FIG. 8, it can be seen that when the number of stirring Re is 950 or more (equivalent to about 1000 rpm or more at stirring speed), the reaction rate constant p is constant at about 0.270, and stable electrolytic reaction can be performed.

  FIG. 9 shows an absorbance-time curve which is a change of the absorbance of the electrolytic solution 10 with respect to the electrolytic reaction time. As shown in FIG. 9, the equilibrium absorbance arrival time at which the total electrolysis is completed and the absorbance is constant was obtained when the stirring Re number was 950 or more, but when the stirring Re number was 950 or less, the stirring Re number was obtained. It became longer with the decline.

From the above, it is considered that when the stirring Re number is smaller than 950 (the stirring speed is slower than about 1000 rpm), the rate of electrolysis is slowed by the rate of supply to the vicinity of the working electrode 3 of Fe (CN) ₆ ^4- by stirring. On the other hand, when the number of stirring Re is 950 or more (the stirring speed is about 1000 rpm or more), it is considered that the rate is limited only by the electrolytic reaction of the working electrode 3 and there is no change due to the difference in the stirring speed.

[Example 3] Relationship between the amount of electrolytic solution and the rate of electrolysis In Example 3, the difference in electrolysis rate due to the difference in the amount of electrolytic solution 10 held in the light transmissive container 2 (hereinafter referred to as the amount of electrolytic solution) Evaluated. In Example 3, constant potential electrolysis and absorptiometry were performed with the amount of electrolyte changed to 1 ml, 1.2 ml, and 1.5 ml. The conditions other than the amount of the electrolytic solution were the same conditions as in Example 1 except that the stirring speed of the stirrer 13 (φ2 mm × 7 mm) was 1400 rpm. Table 3 shows the measurement conditions and the measurement results (reaction rate constant p, equilibrium absorbance and its arrival time, total electrolysis time) in each electrolytic solution amount.

  In terms of chemical engineering, changing the amount of the electrolyte in the evaluation of the stirring condition corresponds to scaling up or down of the apparatus. Therefore, in the condition comparison in which the amount of the electrolyte in Example 3 was changed, when calculating the stirring Re number, the length of the stirrer 13 was calculated and corrected after the correction according to the similarity rule of the Re number. It is necessary to determine the number of stirring Re (corrected stirring Re number). The corrected stirring Re number can be calculated as follows.

  For example, the corrected stirring Re number of the electrolyte amount of 1.2 (ml) is obtained based on the condition of the electrolyte amount of 1 (ml). Based on the ratio of the amount of electrolyte, the scale-up coefficient is 1.2 / 1.0 = 1.2. That is, the length of the stirrer 13 is equivalent to 1 / 1.2 times on the basis of 1 ml of the electrolytic solution amount under the stirring condition of the electrolytic solution amount of 1.2 (ml). Therefore, 7 mm × (1 / 1.2) What is necessary is just to use it for calculation of stirring Re number as = 5.8mm. When the amount of the electrolytic solution is 1.5 (ml), the corrected stirring Re number can be obtained by the same method.

  As shown in Table 3, the value of the reaction rate constant p increases as the amount of the electrolytic solution decreases. In the calculation of the reaction rate constant p in the examples, a logarithmic plot of the current value in the working electrode 3 was performed as shown in FIG. 10, and the reaction rate constant p was obtained from the slope of the straight line at t = 50 s.

  FIG. 11 shows a current-time curve when constant potential electrolysis is performed under conditions where the amount of the electrolytic solution is different. As shown in FIG. 11, when the amount of the electrolytic solution increases, the decreasing rate of the current value flowing through the working electrode 3 decreases.

  FIG. 12 shows an absorbance-time curve that is a change of the absorbance of the electrolytic solution 10 with respect to the electrolytic reaction time. As shown in FIG. 12, the time for the absorbance to become constant (that is, the time for complete electrolysis) became longer in the order of 1 ml, 1.2 ml, and 1.5 ml of the electrolyte solution.

  The above is explained by comparing the corrected stirring Re numbers in Table 3. That is, when the length of the stirrer 13 and the stirring speed are the same, the number of corrected stirring Re decreases as the amount of the electrolytic solution increases, so that numerical values such as the reaction rate constant, the equilibrium absorbance arrival time, the total electrolysis time, etc. Is a value corresponding to a decrease in the stirring Re number.

  Based on the above concept, the relationship between the number of Re stirring and the reaction rate constant p shown in FIG. 8 can be plotted on an approximate curve. From this, it is possible to optimize the amount of electrolyte by the corrected stirring Re number.

  From the above, it should be noted that the change in the amount of the electrolytic solution 10 affects the stirring state. And even if the amount of the electrolytic solution 10 held in the light transmissive container 2 is increased or decreased, the measurement conditions are modified so that sufficient agitation can be achieved based on the corrected agitation Re number, thereby improving the accuracy and efficiency of the analysis. Maintained measurement is possible.

  Note that the amount of the electrolyte solution 10 held in the light transmissive container 2 has no problem in measuring the absorbance in the electrolytic cell 1, and the electrodes such as the counter electrode 5 provided in the sealing member 9 are in the electrolyte solution 10. At least the amount to be immersed is necessary.

[Example 4] Relationship between counter electrode area and bulk electrolysis rate Electrolysis rate due to difference in surface area of counter electrode 5 (surface area (immersion area) of a portion of counter electrode 5 that is immersed in electrolyte solution 10 and can undergo electrode reaction)) The difference was evaluated. In Example 4, a platinum wire (φ1 mm × 1 mm, surface area: 0.039 cm ² ) and a platinum net (10 mm × 40 mm, thickness: 0.07 mm, surface area: 14.8 cm ² ) were used as the counter electrode 5 and electrolysis was performed. The liquid amount was set to 1 ml, and the stirring speed of the stirring bar 13 was set to 1400 rpm (the number of stirring Re was 1140). Other conditions were the same as those in Example 1, and constant potential electrolysis and absorptiometry were performed. In Example 4, the surface area of the counter electrode 5 was set to 380 times so that the influence of the counter electrode area becomes clear. As the working electrode 3, a platinum mesh (5 mm × 40 mm, thickness: 0.14 mm, surface area: 14.8 cm ² ) having the same dimensions was used regardless of whether a platinum wire was used for the counter electrode or a platinum mesh. . Therefore, the ratio of the surface area (immersion area) of the working electrode 3 to the surface area (immersion area) of the counter electrode 5 (working electrode area / counter electrode area) was 380 and 1, respectively. Table 4 shows the test conditions in Example 4.

  FIG. 13 shows a current-time curve when constant potential electrolysis is performed under each condition. As shown in FIG. 13, when the surface area of the counter electrode 5 increases, the rate of decrease in the current value flowing through the working electrode 3 decreases.

  In the electrolytic reaction time t = 100 s, when the current value flowing through the working electrode 3 obtained under the conditions of Example 4 is 1, the relative value of the current value flowing through the working electrode 3 obtained under the conditions of Comparative Example 2 is 3, indicating that the time required for total electrolysis increases as the surface area of the counter electrode 5 increases.

In FIG. 14, the light absorbency-time curve which is a change with respect to the electrolysis reaction time of the light absorbency of the electrolyte solution 10 is shown. As shown in FIG. 14, in t = 100s, to surface area of the electrode 5 when the absorbance is 1 in the case of electrolysis condition in the case of 0.039 cm ^2, the surface area of the counter electrode 5 is in the case of 14.8 cm ² When the electrolysis is performed under the conditions, the absorbance is 0.87, which indicates that the total electrolysis time becomes longer as the area of the counter electrode 5 increases.

This is because when the counter electrode 5 area is small (when a platinum wire is used), hydrogen ions are mainly reduced in the counter electrode 5 whereas the counter electrode 5 has a large area (platinum network). It is considered that the electrode reaction active substance Fe (CN) ₆ ^3- produced at the working electrode ³ is reduced again to Fe (CN) ₆ ^4- and oxidized again at the working electrode 3. Under any condition, constant potential electrolysis and absorptiometric measurement could be performed without any trouble.

  From the above, the influence of the working electrode 3 on the electrode reaction can be reduced as the surface area of the counter electrode 5 is smaller than the surface area of the working electrode 3. On the other hand, if the surface area of the counter electrode 5 is made too small, a large amount of bubbles are generated on the surface of the counter electrode 5 for reasons such as electrolysis of the solution, and the surface of the counter electrode 5 is covered with the bubbles. There is a possibility that contact with the Therefore, when the working electrode area / counter electrode area is 380 or less, more preferably 380 or less and 1 or more, the electrolytic reaction of the electrolytic cell is measured without using a diaphragm or the like between the working electrode 3 and the counter electrode 5. be able to. In addition, when a diaphragm or the like is provided between the working electrode 3 and the counter electrode 5 as in the second embodiment described later, even when the surface area of the counter electrode 5 is increased, the working electrode 3 is hardly affected. . Therefore, when a diaphragm is provided between the working electrode 3 and the counter electrode 5, the surface area of the counter electrode 5 is preferably set to a size that is not affected by the generated bubbles.

[Example 5] Measurement of redox potential and number of reaction electrons In Example 5, with respect to Fe (CN) ₆ ^4- known as a reductant, standard redox potential (formula potential E ⁰ ') and redox The number n of reaction electrons involved in the reaction was determined.

First, 1.0 ml of a 0.1 mol / l phosphate buffer (pH 7.0) containing 0.25 mmol / l Fe (CN) ₆ ^4- was held in the light transmissive container 2 as a sample S2.

  Then, after the sample S2 is degassed with nitrogen gas, potentials of 140 mV, 180 mV, 220 mV, and 260 mV are applied to the working electrode 3 while flowing the nitrogen gas into the sample S2 through the introduction pipe 7 (see (Potential based on the electrode 6) was applied to perform constant potential electrolysis, and an absorption spectrum at a wavelength of 250 nm to 500 nm was measured with an ultraviolet-visible diode array spectrophotometer.

As shown in the characteristic diagram of FIG. 15, it is a peak wavelength that identifies Fe (CN) ₆ ^3- that is an oxidant among redox pairs of Fe (CN) ₆ ^4- and Fe (CN) ₆ ^3-. It can be read from the absorbance at a wavelength of 420 nm that the absorption peak changes according to the set applied voltage.

Next, the concentration ratio of [Fe (CN) ₆ ³⁻ ] and [Fe (CN) ₆ ⁴⁻ ] based on Lambert-Beer's law from the change in absorption spectrum at a wavelength of 420 nm measured at each potential ( [O] / [R]) was calculated, and a Nernst plot of [O] / [R] and the electrode potential of the working electrode 3 was obtained based on the equation (1). FIG. 16 shows a Nernst plot.

In the result shown in FIG. 16, Nernst analysis was performed, and from the intercept of the regression equation, the formula quantity potential E ⁰ ′ of Fe (CN) ₆ ⁴⁻ was 210 mV (converted on the basis of SHE (approximately 197 mV on the Ag / AgCl reference potential). The total number of reaction electrons n was 1 from the slope of the regression equation. Each of these numerical values substantially coincided with literature (for example, non-patent literature 4) values.

Therefore, according to the electrolytic cell 1 according to the present embodiment, when there is an absorption peak wavelength capable of selectively specifying either of the redox species, the spectroelectrochemical method is applied to apply the standard redox potential ( That is, the formula potential E ⁰ ′) and the number of reaction electrons n could be measured, and the measured values were confirmed to have sufficient measurement accuracy.

(Embodiment 2)
FIG. 17 shows a schematic side view of the electrolysis cell 11 according to Embodiment 2 of the present invention. The electrolytic cell 11 according to Embodiment 2 of the present invention is provided in the counter electrode chamber 12 formed by electrically connecting the counter electrode 5 of the electrolytic cell 1 according to Embodiment 1 with the electrolytic solution 10 through the glass filter 12a. Except for this, it is the same as the electrolytic cell 1 according to Embodiment 1. Therefore, the same code | symbol is attached | subjected about the structure similar to the electrolytic cell 1 which concerns on Embodiment 1, and detailed description is abbreviate | omitted.

  As shown in FIG. 17, the electrolytic cell 11 according to the second embodiment includes a light transmissive container 2, a stirrer 13, a working electrode 3, a working electrode fixing frame 4, a counter electrode 5, a counter electrode chamber 12, and a sealing member 9. Is provided.

  The counter electrode chamber 12 is configured by providing a glass filter 12a at one end of a cylindrical glass tube. The counter electrode chamber 12 holds an electrolyte solution (for example, an electrolyte solution having the same composition as the electrolyte solution 10 except that the electrode reaction active substance is not included), and the counter electrode chamber is immersed in the electrolyte solution. 12 is immersed in the electrolytic solution 10. That is, the counter electrode chamber 12 is electrically connected to the electrolyte solution 10 through the glass filter 12a.

Next, using the electrolytic cell 11, various samples were analyzed by constant potential electrolysis as shown in Examples 6 and 7. In the electrolytic cells 11 of Examples 6 and 7, the light transmissive container 2 is a quartz cell manufactured by GL Sciences (double-faced quartz code 6210-11006, optical path length 10 mm), and the working electrode 3 is manufactured by Niraco. The platinum mesh (φ0.07 mm, 100 mesh) was cut into a shape of 10 mm × 40 mm, thickness: 0.07 mm, surface area: 14.8 cm ² , and the platinum mesh was bent to 5 mm × 40 mm, thickness: 0.00. 14 mm, surface area: 14.8 cm ² , working electrode fixed frame 4 made of peak resin, counter electrode 5 covered with a 1 mm diameter platinum wire, and only 10 mm tip exposed, counter electrode chamber 12, a 1,2-dichloroethane solution containing 0.1 mol / l of tetrabutylammonium hexafluorophosphate (TBAHFP) was held in a glass tube having a diameter of 3 mm. The reference electrode 6 is an Ag electrode in which a silver wire is immersed in a 1,2-dichloroethane solution containing 0.1 mol / l of TBAHFP, the introduction tube 7 and the discharge tube 8 are a glass tube having a diameter of 1 mm, and a sealing member 9 was made of a peak resin. Stirring of the electrolytic solution 10 was performed using a stirring bar 13 (MC-7 φ2 mm × 7 mm) manufactured by GL Science and a magnetic stirrer.

[Example 6] Spectroelectrochemical measurement in a non-aqueous solvent In Example 6, 0.02 mmol / l tetracyanoquinodimethane (TCNQ) and 0.1 mol / l tetrabutylammonium hexafluorophosphate (TBAHFP) 1.0 ml of the 1,2-dichloroethane solution containing was stored as a sample S3 in the light transmissive container 2.

Then, after degassing the sample S3 with nitrogen gas, the stirrer 13 (φ2 mm × 7 mm) was placed in the light transmissive container 2 and rotated at 1400 rpm to stir the electrolyte solution 10. At this time, the number of stirring Re was 1554, which was a sufficient stirring state. Then, a potential of 0.1 V (potential based on the reference electrode 6 (Ag / Ag ⁺ )) is applied to the working electrode 3 while flowing nitrogen gas into the sample S3 through the introduction tube 7. Was used to perform constant-potential electrolysis, and the change in current at the working electrode 3 during the electrolysis was measured. TCNQ was reduced to TCNQ ^{− ·} by constant potential electrolysis. Furthermore, the light absorbency of wavelength 300-1000nm was measured with respect to sample S3 during constant potential electrolysis.

  Further, as a comparative example of Example 6, the counter electrode chamber 12 was not provided, and the counter electrode 5 (a platinum wire having a diameter of 1 mm was covered and only the tip 10 mm was exposed) was directly immersed in the electrolytic solution 10. A constant potential electrolysis and absorptiometric measurement were performed under the same conditions as in Example 6 to obtain Comparative Example 2.

  FIG. 18 shows a current-time curve when constant potential electrolysis was performed under the conditions of Example 6 and Comparative Example 2. As shown in FIG. 18, when the electrolysis was performed under the condition of Comparative Example 2 (without the counter electrode chamber 12) as compared with the condition of Example 6 (with the counter electrode chamber 12), the rate of decrease in the current value was slow. In the electrolytic reaction time t = 100 s, when the current flowing through the working electrode 3 is 1 when the counter electrode chamber 12 is present, the relative value of the current flowing through the working electrode 3 when the counter electrode chamber 12 is absent is 9. That is, providing the counter electrode chamber 12 shortened the time required for total electrolysis.

In FIG. 19, the change with respect to the reaction time of the light absorbency when constant potential electrolysis was performed on the conditions of Example 6 and Comparative Example 2 is shown. Of TCNQ and TCNQ ^{− ·} which are redox species in the electrolyte solution 10 ^, only TCNQ ^{− ·} has an absorption peak at 850 nm. When the electrolytic solution 10 containing TCNQ is electrolyzed at a constant potential ^, the concentration of TCNQ ^{− in the} electrolytic solution 10 increases with the lapse of electrolysis time. Therefore, the absorbance at a wavelength of 850 nm with respect to the electrolytic solution 10 increases with time, and all electrolysis is completed. It becomes a constant value. As shown in FIG. 19, the time change of the absorbance when the constant potential electrolysis was performed under the conditions of Example 6 and Comparative Example 2 showed almost the same behavior.

As described above, when the counter electrode chamber 12 is present (Example 6) and when the counter electrode chamber 12 is not present (Comparative Example 2), the measured value by the spectroscopic method is not changed, but the current value decreases. The speed was significantly reduced by providing the counter electrode chamber 12. This is because a substance generated by electrolysis of 1,2-dichloroethane or TBAHFP at the counter electrode 5 reacts with TCNQ ⁻ generated by electrolysis of TCNQ at the working electrode 3 in the constant potential electrolysis reaction of the sample S3. It is thought to be caused. That is, in the case of Example 6, the product generated by the reaction of the counter electrode 5 remains in the counter electrode chamber 12 without diffusing into the sample, but in the case of Comparative Example 2, there is no counter electrode chamber 12. presumably because it reacted with ^& - product TCNQ diffuse.

  Therefore, when the reaction product at the counter electrode 5 affects the reaction of the working electrode 3, the counter electrode 5 is provided in the counter electrode chamber 12. The influence on the reaction can be prevented.

[Example 7] Comparison of electrolytic cell according to Embodiment 2 and thin-layered spectroelectrochemical cell In Example 7, the electrolytic cell 11 according to Embodiment 2 and FIGS. 21A and 21B were referred to. Comparison was made with the thin-layered spectroelectrochemical cell 80 (Comparative Example 3) according to the prior art described above.

  In Example 7, the constant-potential electrolysis conditions were the same as in Example 6. Further, in the thin-layer spectroelectrochemical cell 80 of Comparative Example 3, 1.0 mmol / l tetracyanoquinodimethane (TCNQ) and 0.1 mol / l tetrabutylammonium hexafluoro were added to the thin-layer spectroelectrochemical cell. A 1,2-dichloroethane solution containing phosphate (TBAHFP) was prepared as Sample S4, and constant potential electrolysis of Sample S4 was performed.

  Since the optical path length of the electrolysis cell 11 according to Embodiment 2 is 10 mm and the optical path length of the thin-layer spectroelectrochemical cell 80 is 0.2 mm, the concentration is theoretically 50 times higher to obtain the same absorbance. Is required. Therefore, the TCNQ concentration of Comparative Example 3 was 50 times that of the TCNQ concentration of Example 7.

In FIG. 20, the measurement result of the spectroscopic measurement at the time of performing bulk electrolytic reaction on the conditions of Example 7 and Comparative Example 3 is shown. Completion of the bulk total electrolysis reaction was determined that almost all of the TCNQ was reduced to TCNQ ⁻ when the time change of the current flowing through the working electrode 3 in the constant potential electrolysis reaction was almost zero.

As shown in FIG. 20, when comparing the absorbance at 850 nm, which is the selected wavelength for identifying TCNQ ^−, the absorbance in Example 7 is 1.2, while that in Comparative Example 3 is 0.4. It has become. This indicates that in Comparative Example 4, since the electrolytic solution held in the thin-layer spectroelectrochemical cell 80 is not stirred, only the redox species near the working electrode are electrolyzed. That is, in the thin layer type spectroelectrochemical cell 80, it is considered that only about 30% of all redox species are electrolyzed.

  As described above, as described with reference to specific examples, according to the electrolysis cell of the present invention, highly accurate electrochemical measurement and spectroscopic measurement can be performed.

  By using a spectroscopic measurement cell (for example, a cross-sectional shape of 10 mm square), a sample having a long optical path length and a small molar extinction coefficient can be measured at a low concentration. Note that the shape of the cell for spectroscopic measurement is appropriately selected in consideration of the molar extinction coefficient of the substance to be measured and the sample concentration, under the condition that the measurement error is reduced and the electrolyte can be sufficiently stirred. The optical path length of the spectroscopic measurement cell is not limited to 10 mm.

  In addition, when changing the cell size, the length of the stirrer, and the type and amount of the electrolytic solution, the scale-up or the scale-down is performed by the chemical engineering method as in Example 3 based on the stirring Reynolds number. Thus, various conditions of the electrolytic cell can be calculated.

And by providing the stirring means which stirs the electrolyte solution hold | maintained at an electrolytic cell during an electrolytic reaction, rapid bulk electrolysis can be performed. In that case, when the electrolytic reaction is performed under the stirring condition with a stirring Re number of 950 or more, the electrolytic reaction can be rapidly performed. Moreover, since the electrolytic product (electrolytic reaction product) in the electrolytic solution is uniformly distributed by stirring the electrolytic solution, it is not necessary to arrange an electrode on the optical path. As a result, it becomes possible to select an electrode (for example, platinum, gold, carbon, etc.) or an electrode structure according to the sample. By this stirring, the movement of the substance (redox species) can be promoted, and the movement of the substance (redox species) to the working electrode can be made constant by making the stirring speed constant. As a result, the influence of diffusion can be suppressed in the vicinity of the electrode, and the expression potential E ^O ′ can be measured with high accuracy.

  That is, by increasing the optical path length, it is possible to measure a substance having a small light absorption characteristic, and it is possible to shorten the electrolytic reaction time by stirring the electrolytic solution.

  Moreover, since the electrolysis cell of this invention is the structure which inserts the working electrode fixing frame which fixes a working electrode in a light transmissive container, a working electrode is easily provided in the predetermined location of a light transmissive container. Can do. Furthermore, the working electrode fixing frame can block the corners of the light transmissive container, and can hold the electrolytic solution in the central part of the light transmissive container (that is, the part where the spectroscopic measurement is performed). Therefore, even when the amount of the electrolyte solution held in the light transmissive container is reduced, the spectroscopic measurement can be performed with high accuracy. In addition, the time required for the whole electrolysis reaction can be shortened by reducing the amount of the electrolyte solution retained in the light transmissive container.

  In addition, by forming a stirrer guide that stirs the electrolyte under the working electrode fixing frame, the stirrer can be used even when a long stirrer is used or when the rotation speed of the stirrer is increased. It can be rotated well. That is, when the stirring speed of the stirrer is increased, the stirrer is rotated favorably by the guide, so that the electrolytic reaction can be performed quickly. Furthermore, since the place where the stirrer is provided is a portion that does not require light transmission, there is no problem in performing the spectroscopic measurement. Therefore, by forming a stirrer guide at the lower part of the working electrode fixing frame, it is possible to suppress the extra electrolyte solution from being held in the light-transmitting container and perform spectroscopic measurement with a smaller amount of electrolyte solution. .

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications can be made within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

  For example, in the electrolytic reaction of the electrolytic cell of this embodiment, it is possible to calculate the total number of moles of a substance involved in the electrolytic reaction by performing a Nernst analysis and obtaining the number of reaction electrons (electric quantity). If the cell (light-transmitting container) has a sufficiently small structure (for example, a structure that is sufficiently small as compared with a conventional electrolytic cell), it is possible to perform absolute micro-quantification.

  Further, the redox species (electrode reaction active substance) to be subjected to redox measurement is not limited to the example, and the redox reaction can be detected in any redox species. In addition, if the redox species has an absorption peak peculiar to only the oxidant (or only the reductant), the oxidant (or reductant) is measured by measuring the absorbance at the wavelength of the absorption peak. And the like can be obtained by optical measurement. Then, by performing an electrolytic reaction under a stirring condition having a stirring Reynolds number of 950 or more, an electrolytic reaction can be rapidly performed in any redox species.

  In electrochemical analysis, the type of electrolyte varies depending on the analytical application, but if the basic solvent properties (viscosity and density) are clear, the Stirling Reynolds number can be calculated. However, the stirring state can be managed by the stirring Re number.

  Further, by making the surface area of the counter electrode sufficiently small relative to the surface area of the working electrode, various spectroscopic methods can be applied and spectroelectrochemical measurement of the electrolytic cell can be performed without using a diaphragm. Therefore, elucidation of the electrolytic reaction mechanism, control of the electrolytic reaction, and the like are facilitated (for example, easier compared to conventional electrolytic cells).

  When the oxidation / reduction reaction of the working electrode is affected by the reaction products at the counter electrode, the counter electrolyte chamber is prevented regardless of whether the supporting electrolyte is water or a non-aqueous solvent, thereby preventing stirring of the electrolyte. In addition, the influence of the reaction product at the counter electrode can be reduced. That is, by providing the counter electrode chamber, it is possible to prevent movement of the anode reaction product to the cathode side and movement of the cathode reaction product to the anode side.

  The electrolytic cell, electrochemical synthesis method, and electrochemical analysis method of the present invention include standard redox potential measurement methods, absolute microquantitative methods, new electrolytic synthesis methods aimed at fine chemistry, and oxidoreductase is immobilized on the working electrode. The bioelectrode can be used for a microdevice-type electrolytic cell imparted with biological reaction specificity and a method for measuring oxidoreductase activity.

  For example, by applying a bioelectrode on which an oxidoreductase is immobilized as a working electrode to form a microdevice-type electrolytic cell (for example, a conversion system unit having biological reaction specificity with the same configuration as in FIG. 1). Thus, it is possible to carry out absolute micro-quantification with respect to a biological substance that causes a specific reaction to the enzyme. Furthermore, an enzyme capable of causing a redox reaction can be analyzed for the activity of the enzyme. In addition, the respiratory activity of a single cell or a plurality of cells can be analyzed by measuring the oxygen concentration using an electrolytic cell with a minute structure.

1, 11 ... Electrolytic cell 2 ... Light transmissive container (electrolyte container)
3 ... working electrode 4 ... working electrode fixed frame (frame)
4a ... guide 5 ... counter electrode 6 ... reference electrode 7 ... introducing tube 8 ... discharge tube 9 ... sealing member 10 ... electrolytic solution 12 ... counter electrode chamber 13 ... stirring bar (stirring means)

Claims (7)

An electrolytic cell for electrochemical measurements and spectroscopic measurements,
An electrolyte container having at least a pair of side surfaces facing each other and having light permeability;
A working electrode immersed in the electrolytic solution in the electrolytic solution container is provided, and a frame body inserted into the electrolytic solution container;
Stirring means for stirring the electrolyte solution;
A counter electrode immersed in the electrolyte, and a reference electrode;
Have
An electrolysis cell , wherein a guide for the stirring means is formed at an end of the frame . The electrolytic cell according to claim 1 , wherein a fixing groove for fixing the working electrode is formed in the frame. 3. The electrolytic cell according to claim 1, wherein a ratio of an immersion area of the working electrode to an immersion area of the counter electrode is 380 or less. 4. The electrolytic cell according to claim 3 , wherein a ratio of an immersion area of the working electrode to an immersion area of the counter electrode is 1 or more. 5. The electrolytic cell according to claim 1, wherein the counter electrode is provided in a counter electrode chamber electrically connected to the electrolyte in the electrolyte solution container via a diaphragm. 6. . The electrolysis cell according to any one of claims 1 to 5 , wherein the stirring speed of the stirring means is 1000 rpm or more. The electrolytic cell according to any one of claims 1 to 5 , wherein the stirring means stirs the electrolytic solution so that a stirring Reynolds number of the electrolytic solution is 950 or more.

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