JP4482993B2 - Electrochemical measurement method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrochemical measurement method in which a measurement sample is electrochemically measured using a working electrode, a counter electrode, and a solid reference electrode.
[0002]
[Prior art]
In recent years, by investigating the components in a substance, the characteristics of the substance have been grasped and have been used for various developments. For example, the amount of dissolved oxygen and the amount of chemical oxygen supplied in water indicate the amount of water contamination, and the amounts of nitric acid, various metals and organic substances in the soil indicate the amount of soil contamination. Among them, foods are required to have a certain level of quality from the viewpoint of health and safety, and acids contained in foods have a great influence on the quality of foods. This acid will be explained in detail. The acidity of food includes acidity of free fatty acids contained in edible oil, acidity of malic acid and tartaric acid contained in fruit drinks such as juice, and alcoholic drinks such as whiskey, liquor and wine. The acidity of the acid to be used and the acidity of the coffee acid in the coffee have been used, and neutralization titration methods have been mainly used in the past as methods for measuring the acid.
[0003]
There are various neutralization measurement methods. For example, the standard oil and fat analysis method, Japanese agricultural and forestry standard, JIS, Japanese Pharmacopoeia oil and fat test method, hygiene test method food and drink test method, water test method, etc. Although there are defined methods, the basis of the measurement of all is phenolphthalein as an indicator. A detailed description of this neutralization titration method is omitted.
[0004]
On the other hand, as a method for measuring acid, there is a method in which acidity is measured by an electrochemical measurement method without using such neutralization titration method. This is, for example, a measurement method disclosed in Japanese Patent Application Laid-Open No. 5-264503, in which a measurement electrolyte solution in which a free fatty acid and a naphthoquinone derivative coexist is measured by an electrochemical measurement method based on a potential regulation method. Such an electrochemical measurement method that sweeps by the potential regulation method is called voltammetry. The current value of the pre-reduction wave of the naphthoquinone derivative is proportional to the free fatty acid concentration for all fatty acids from lower fatty acids such as formic acid to higher fatty acids such as oleic acid and linoleic acid, and the current values of each fatty acid are superimposed. It is used that the combined value corresponds to the total concentration of fatty acids. That is, the acid concentration is measured by measuring the current value of the pre-reduction wave of the naphthoquinone derivative. The method will be briefly described below.
[0005]
FIG. 6 shows the voltage generated between the working electrode and the counter electrode when the voltage between the working electrode and the counter electrode is swept so that the voltage changes at a constant speed by monitoring the voltage of the working electrode and the solid reference electrode. It is the graph which measured the electric current value to do. Using the fact that the relationship between the reduction pre-wave current value i and the acidity in FIG. 6 is proportional, the measured value is collated with a calibration curve prepared in advance between the standard acidity and the current value. It is a method to ask for.
[0006]
In addition, it relates to the electrode storage method. In the electrochemical measurement method, measurement is performed by immersing the electrode in a coexisting electrolyte mixed with the measurement electrolyte and measurement sample, and after the measurement, the electrode is washed with a cleaning solution. In addition, there is a storage method of storing in a dry storage or immersing in water. However, in this storage method, the measured value is not stable at the beginning of the measurement, that is, for a while after the electrode is immersed in the coexisting electrolyte. This is thought to be because there is what should be “familiar” between each electrode, particularly the working electrode and the coexisting electrolyte. In this storage method, since there is no “familiarity” immediately after the start of measurement, it is conceivable that measured values vary.
[0007]
Thus, in the storage method in the conventional electrochemical measurement method, since the measurement value after immersion is not stable, the measurement was repeated many times, and the value when the measurement value was stabilized was regarded as the effective value.
[0008]
[Problems to be solved by the invention]
As described above, the conventional electrochemical measurement method has a problem that the stored electrode is immersed in the coexisting electrolyte and the data varies for a while. A possible reason for this is that when the electrode surface is viewed microscopically, the effective surface of the electrode is determined by the penetration of the coexisting electrolyte along the fine irregularities of the electrode surface. This means that the area of the effective surface has changed due to adhesion of microscopic bubbles or dust.
[0009]
In this electrochemical measurement method, it is required to prevent variation in data immediately after the electrode is immersed in the coexisting electrolyte.
[0010]
An object of the present invention is to provide an electrochemical measurement method capable of preventing variation in data immediately after an electrode is immersed in a coexisting electrolyte.
[0011]
[Means for Solving the Problems]
In order to achieve this object, the electrochemical measurement method of the present invention is immersed in a coexisting electrolyte obtained by mixing a measurement electrolyte obtained by mixing an electrolyte with an organic solvent, a measurement sample, and a reversible redox reagent. Using the working electrode, counter electrode, and solid reference electrode, the potential of the working electrode is set to a potential that sweeps within the specified potential difference from the potential of the solid reference electrode, and the current flowing between the working electrode and the counter electrode is detected. To measure the acidity of the sample This is a batch-type electrochemical measurement method, and has a configuration in which at least the working electrode is kept in a dipped state or a wet state with an organic preservation solution during non-measurement.
[0012]
In addition, the electrochemical measurement method of the present invention includes a measurement electrolyte obtained by mixing an electrolyte in an organic solvent and a measurement sample, a working electrode immersed in a coexisting electrolyte mixed with a reversible redox reagent, a counter electrode, Using a solid reference electrode, the potential of the working electrode is kept at a constant potential difference from the potential of the solid reference electrode, and the current flowing between the working electrode and the counter electrode is detected. To measure the acidity of the sample This is a batch-type electrochemical measurement method, and has a configuration in which at least the working electrode is kept in a dipped state or a wet state with an organic preservation solution during non-measurement.
[0013]
Thereby, the electrochemical measurement method which can prevent the dispersion | variation in the data immediately after immersing an electrode in coexistence electrolyte solution is obtained.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The electrochemical measurement method according to claim 1 of the present invention is an operation in which a measurement electrolytic solution obtained by mixing an electrolyte in an organic solvent, a measurement sample, and a coexisting electrolytic solution in which a reversible redox reagent is mixed. Using the electrode, counter electrode, and solid reference electrode, the potential of the working electrode is set to a potential that sweeps within the specified potential difference from the potential of the solid reference electrode, and the current flowing between the working electrode and the counter electrode is detected. To measure the acidity of the sample This is a batch-type electrochemical measurement method, and at the time of non-measurement, the working electrode is kept in a dipped or wet state with an organic preservation solution. The familiarity is kept almost constant without changing over time, and the variation in the current value that flows when the potential of the working electrode is swept within the predetermined potential difference from the potential of the solid reference electrode is immersed in the coexisting electrolyte. It has the effect of being suppressed to the minimum value immediately after.
[0015]
The electrochemical measurement method according to claim 2 includes a measurement electrolyte solution obtained by mixing an electrolyte in an organic solvent, a measurement sample, a working electrode immersed in a coexisting electrolyte solution mixed with a reversible redox reagent, and a counter electrode. Using a solid reference electrode, the potential of the working electrode is kept at a constant potential difference from the potential of the solid reference electrode, and the current flowing between the working electrode and the counter electrode is detected. To measure the acidity of the sample This is a batch-type electrochemical measurement method, and at the time of non-measurement, the working electrode is kept in a dipped or wet state with an organic preservation solution. The familiarity is maintained almost constant without changing over time, and the variation in the current value that flows when the potential of the working electrode is maintained at a constant potential difference from the potential of the solid reference electrode is immediately after the electrode is immersed in the coexisting electrolyte. It has the effect of being suppressed to the minimum value.
[0016]
The electrochemical measurement method according to claim 3 is the electrochemical measurement method according to claim 1 or 2, wherein the organic preservation solution is a liquid electrolyte for measurement. Organic It is intended to contain at least one of the solvent component, the electrolyte component of the measurement electrolyte, the reversible redox reagent, and the substance to be measured, whereby the electrode is immersed in the coexisting electrolyte. At this time, the storage solution and the coexisting electrolyte on the electrode surface can be smoothly exchanged. Note that the substance to be measured is a substance for measurement contained in the measurement sample such as citric acid or malic acid if the measurement sample is orange.
[0017]
The electrochemical measurement method according to claim 4 is the electrochemical measurement method according to claim 3, wherein the substance to be measured is a carboxylic acid, whereby the electrode is immersed in the coexisting electrolyte. When the storage solution on the electrode surface is replaced with the coexisting electrolyte, the concentration of the carboxylic acid in the storage solution is uniform from the concentration of the carboxylic acid in the storage solution by the carboxylic acid previously given to the storage solution. It has the effect that the conversion is performed quickly. In addition, even if the carboxylic acids are different carboxylic acids, the reduction potentials are almost the same. Therefore, the current flowing between the working electrode and the counter electrode is almost governed by the total acidity of all carboxylic acids. If an acid is contained, the concentration of all carboxylic acids can be made uniform quickly.
[0018]
The electrochemical measurement method according to claim 5 is the electrochemical measurement method according to claim 3 or claim 4, wherein the reversible redox reagent is quinone, whereby an electrode The quinone concentration in the preservation solution is changed from the quinone concentration in the preservation solution to the quinone concentration in the coexistence electrolyte by the quinone previously given to the preservation solution when the preservation solution on the electrode surface is replaced with the coexistence electrolyte when immersed in the coexistence electrolyte This has the effect that the concentration of the liquid is rapidly made uniform.
[0019]
The electrochemical measurement method according to claim 6 is the electrochemical measurement method according to any one of claims 3 to 5, wherein the organic preservation solution contains a denatured alcohol. The preservation solution has an effect that it is inexpensive.
[0020]
The electrochemical measurement method according to claim 7 is the electrochemical measurement method according to claim 1 or claim 2, wherein the organic preservation solution is a liquid having the same component as the electrolyte for measurement, As a result, the measurement electrolytic solution is diverted as the storage solution, and there is an effect that it is not necessary to prepare it separately.
[0021]
The electrochemical measurement method according to claim 8 is the electrochemical measurement method according to claim 1 or 2, wherein the organic preservation solution is reversibly redox-reducing into a solution having the same component as the electrolyte for measurement. Reagent added, so that when the electrode is immersed in the coexisting electrolyte, the electrolyte and reversible oxidation-reduction previously applied to the storage solution when the storage solution on the electrode surface is replaced with the coexisting electrolyte The functional reagent has the effect that the concentration of the electrolyte and the reversible redox reagent in the storage solution is rapidly made uniform from the concentration of the electrolyte and the reversible redox reagent in the coexisting electrolytic solution.
[0022]
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
[0023]
(Embodiment 1)
In the electrochemical measurement method according to Embodiment 1 of the present invention, the acidity is determined from the current flowing between the working electrode and the counter electrode when the potential of the working electrode is swept within a predetermined potential difference from the potential of the solid reference electrode. The acidity measurement method (voltammetry measurement method) for calculating the value will be described in detail with reference to the drawings.
[0024]
FIG. 1 is a configuration diagram showing a measurement cell at the time of acidity measurement.
[0025]
In FIG. 1, 1 is a counter electrode, 2 is a working electrode, 3 is a solid reference electrode, 4 is a coexisting electrolyte obtained by mixing a measurement electrolyte, a reversible redox reagent and a measurement sample for causing an electrochemical reaction, 5 is a measurement container, 6 is a measurement cell, and 10 is a container cover.
[0026]
In acidity measurement, an orthobenzoquinone derivative or the like, which is a reversible redox reagent, was added in advance to an electrolyte for measurement in which an electrolyte such as sodium chloride or lithium perchlorate was mixed in an alcohol such as ethanol or an organic solvent such as isooctane. Use things. A parabenzoquinone derivative may be used as the reversible redox reagent. These have excellent characteristics that they are excellent in light stability and can be measured without removing dissolved oxygen. In the present invention, these are referred to as quinones.
[0027]
A container cover 10 to which the counter electrode 1, the working electrode 2, and the solid reference electrode 3 are attached is attached to the measurement container 5 in a state where the electrodes 1 to 3 are immersed in the coexisting electrolyte 4. In the first embodiment, a measurement electrolytic solution in which sodium chloride as an electrolyte is added to a mixed solution of water as a solvent, ethanol and isopropyl alcohol, and an orthobenzoquinone derivative as a reversible redox reagent are mixed. A case where a mixed solution for measurement (hereinafter, a sample-unmixed electrolyte) is used as an example will be described.
[0028]
In FIG. 1, the counter electrode 1, the working electrode 2, and the solid reference electrode 3 are each electrically connected to the outside, and are electrically connected to a measuring instrument main body (not shown). The measuring instrument main body here includes a control unit that performs voltage control applied between the electrodes and current measurement, a power source, and the like, but is not necessary in the description of the present embodiment, and thus the drawings and the description thereof are omitted.
[0029]
By the way, the acidity measurement method for calculating the acidity from the current flowing between the working electrode 2 and the counter electrode 1 while keeping the potential of the working electrode 2 at a potential that maintains a constant potential difference from the potential of the solid reference electrode 3 is also carried out. Only the operation of the control unit is different from the above-described form, and the operations and effects relating to measurement and electrode storage are completely the same. This acidity measurement method is called chronoamperometry.
[0030]
FIG. 2 is a configuration diagram showing an electrode storage state at the time of non-measurement, and FIG. 3 is a configuration diagram showing a sample-unmixed electrolyte solution at the time of non-measurement. 2 and 3, the counter electrode 1, the working electrode 2, the solid reference electrode 3, the measurement container 5, and the container cover 10 are the same as those in FIG. 7 is an organic storage solution, 8 is a storage container, 9 is a measurement electrolyte in which 150 mM sodium chloride is added to a solvent in which ethanol, isopropyl alcohol, and water are mixed at a volume ratio of 6: 2: 2. This is a sample-unmixed electrolyte solution mixed with 20 mM orthobenzoquinone derivative. The preservation solution 7 is a mixture of denatured alcohol and water mixed at a volume ratio of 50:50 and added with 20 mM sodium chloride. In addition, the denatured alcohol used the commercial item which mixed ethanol, isopropyl alcohol, and 1-butanol by volume ratio 86: 13: 1. As the storage solution, a solution containing at least one of a solvent component, sodium chloride (electrolyte component), an orthobenzoquinone derivative (reversible redox reagent), and a substance to be measured is suitable. In the first embodiment, the liquid having the same component as the measurement electrolyte, that is, the measurement electrolyte is diluted and used as the storage solution, but the measurement electrolyte may be used as it is.
[0031]
As shown in FIG. 2, the counter electrode 1, the working electrode 2, and the solid reference electrode 3 are all immersed in the storage solution 7. First, the container cover 10 is removed, and a measurement sample obtained by measuring a predetermined amount is injected into the measurement container 5 (FIG. 3) to prepare the coexisting electrolyte 4 with the sample-unmixed coexisting electrolyte 9.
[0032]
Next, the container cover 10 is removed with the counter electrode 1, the working electrode 2, and the solid reference electrode 3 attached, and the electrodes 1 to 3 are taken out from the storage solution 7. At this time, since the electrodes 1 to 3 are wrinkled with the storage solution 7, it is necessary to shake the container cover 10 several times to shake off the wrinkles. Thereafter, the counter cover 1, the working electrode 2, and the solid reference electrode 3 are immersed in the coexisting electrolyte 4 by mounting the container cover 10 on the measuring container 5 containing the coexisting electrolyte 4 (this state is shown in FIG. 1). State.) Subsequently, while the electrodes 1 to 3 are immersed in the coexisting electrolyte 4, the measurement cell 6 is held and shaken to stir the coexisting electrolyte 4 and to allow the electrodes 1 to 3 to conform to the coexisting electrolyte 4. In addition, in this Embodiment, although 3 electrodes 1-3 are immersed in the preservation | save liquid, the same effect is acquired by immersing only the working electrode 2 which is a reaction electrode in a preservation | save liquid.
[0033]
It goes without saying that it takes time for the coexisting electrolyte 4 to penetrate into the electrode when the electrode is stored dry, and even if it is immersed in water and stored, microscopic bubbles and dust adhere to the electrode surface. Water having low permeability does not reach the fine irregularities of the electrode surface, and even when the electrode is immersed in the coexisting electrolyte 4, there is a difference in the components of the water and the alcohol-based coexisting electrolyte 4. Therefore, the replacement is slow and it takes time for the coexisting electrolyte 4 to penetrate into the electrode surface.
[0034]
However, as shown in FIG. 2, when the electrodes 1 to 3 are stored by immersing them in a highly permeable organic-based, particularly alcohol-based storage solution 7, they are stored even when microscopic bubbles or dust adhere to the electrode surface. The liquid 7 reaches the details of the electrode surface. Furthermore, when the electrodes 1 to 3 are immersed in the coexisting electrolyte 4, the coexisting electrolyte 4 and the preserving solution 7 having similar components are replaced quickly, and the coexisting electrolyte 4 penetrates the electrode surface quickly. is there. Further, 20 mM sodium chloride is added to the storage solution 7, and the concentration of the sodium chloride concentration in the storage solution 7 to the sodium chloride concentration in the coexisting electrolyte solution 4 is rapidly performed on the electrode surface. Although not used in the present embodiment, by adding quinone, which is a reversible redox reagent, to the storage solution 7, the concentration of the quinone in the storage solution 7 on the surface of the electrode can be used to determine the concentration in the coexisting electrolyte 4. It is possible to quickly make the concentration uniform to the quinone concentration. Similarly, by adding the carboxylic acid that is the measurement target substance to the storage solution 7, the concentration of the carboxylic acid in the storage solution 7 on the electrode surface can be quickly made uniform from the carboxylic acid concentration in the coexisting electrolyte 4. It is also possible to do so. In addition, since the reduction potentials of carboxylic acids are almost the same even with different acids, the current flowing between the counter electrode 1 and the working electrode 2 is governed by the total acidity, and malic acid, tartaric acid, lactic acid. The effect of being able to accurately measure the total acidity is obtained even when there are a plurality of substances to be measured in a single measurement sample, such as wine containing a wide variety of carboxylic acids. At that time, the carboxylic acid added to the preservation solution 7 may be one kind, and the kind is not particularly limited as long as it can be completely dissolved in the preservation solution 7 and the coexisting electrolyte solution 4.
[0035]
Further, as an electrode storage method at the time of non-measurement, the electrode is applied to a method of spraying the storage solution 7 continuously or intermittently on the electrode or a material having good water absorption such as cotton or sponge containing the storage solution 7. The same effect can be obtained.
[0036]
After shaking the measurement cell 6 by hand, the measurement cell 6 is set in a measuring instrument main body (not shown) and measurement is started. At the time of measurement, the current flowing between the working electrode 2 and the counter electrode 1 obtained when the potential of the working electrode 2 is swept within a predetermined potential difference from the electrode potential of the solid reference electrode 3 is controlled by the control unit. The acidity is calculated from a calibration curve obtained in advance.
[0037]
Here, in the case where mandarin orange juice is used as the measurement sample, the measurement value variations due to different electrode storage states are compared with FIG. 4 and FIG. 5. In general, the acidity of fruit juice is expressed by the weight ratio (wt%) of how much it is contained in the fruit juice when the sum of the multiple acids present is replaced with a representative acid. Stipulated as being represented by citric acid.
[0038]
FIG. 4 is a graph showing acidity measurement values when using an electrode that has been stored dry, and FIG. 5 is a graph showing acidity measurement values when using an electrode that has been immersed and stored in the preservation solution 7. FIG. 4 shows the measurement of acidity when the electrode was stored in a dry state and the immersion time after the electrode was immersed in the coexisting electrolyte 4 reached a predetermined time. The relationship between immersion time when measured about coexisting electrolyte solution of this and measurement value dispersion | variation is shown. Further, FIG. 5 uses an electrode immersed and stored in the preserving solution 7, and the acidity is measured when the immersion time after the electrode is immersed in the coexisting electrolyte 4 reaches a predetermined time, as in the case of FIG. The relationship between immersion time and measured value variation when this is measured for 10 different coexisting electrolytes prepared with the same measurement sample is shown. In all measurements, the same electrode was used with a storage time of 60 minutes or more from the end of the previous measurement, and the measured value variation was expressed as a ratio of the maximum measured value difference to the measured average value in percent.
[0039]
From the graphs of FIGS. 4 and 5, the dry-stored electrode is immersed in the coexisting electrolyte 4 and the measured value is not stable for a while. When the electrode stored in the preserving solution 7 is used, the electrode is immersed in the coexisting electrolyte 4. It can be seen that the measured value is stabilized immediately after the measurement.
[0040]
After completion of the measurement, the container cover 10 is removed from the measurement container 5 and the electrode is taken out from the coexisting electrolyte 4. Thereafter, the counter cover 1, the working electrode 2, and the solid reference electrode 3 are immersed in the storage solution 7 by attaching the container cover 10 to the storage container 8 containing the storage solution 7. By the way, although it does not affect the measurement, in order to suppress discoloration of the preservation solution 7 due to quinone, it is necessary to shake the container cover 10 several times to shake off the soot of the coexisting electrolyte solution 4 attached to the electrode. When the quinone that is a reversible redox reagent, sodium chloride that is an electrolyte, and the acid of the substance to be measured are dissolved and contained as the preservation solution 7, the quinone, sodium chloride, and acid that are attached to the electrode during storage of the electrode Since it elutes into the coexisting electrolyte 4 when immersed in the coexisting electrolyte 4, the concentration of quinone, sodium chloride, acid in the preservation solution 7 and quinone, sodium chloride, acid in the coexisting electrolyte 4 is made uniform on the electrode surface. Is done quickly.
[0041]
【The invention's effect】
According to the electrochemical measurement method described in claim 1 of the present invention, it is immersed in a coexisting electrolyte obtained by mixing a measurement electrolyte obtained by mixing an electrolyte with an organic solvent, a measurement sample, and a reversible redox reagent. The working electrode, counter electrode, and solid reference electrode are used to make the potential of the working electrode sweep within a predetermined potential difference from the potential of the solid reference electrode, and the current flowing between the working electrode and the counter electrode is detected. To measure the acidity of the sample A batch-type electrochemical measurement method, in which the familiarity between the coexisting electrolyte and the working electrode changes with time by keeping at least the working electrode immersed or wet with an organic preservation solution when not measured. Since the potential of the working electrode is swept within a predetermined potential difference from the potential of the solid reference electrode, the variation in the current value that flows when the electrode is immersed in the coexisting electrolyte is minimized. An advantageous effect is obtained that the variation in data immediately after the electrode is immersed in the coexisting electrolyte can be prevented.
[0042]
According to the electrochemical measurement method according to claim 2, the working electrode is immersed in a coexisting electrolytic solution in which a measurement electrolytic solution obtained by mixing an electrolyte in an organic solvent, a measurement sample, and a reversible redox reagent are mixed. Using a counter electrode and a solid reference electrode, the potential of the working electrode is kept at a constant potential difference from the potential of the solid reference electrode, and the current flowing between the working electrode and the counter electrode is detected. To measure the acidity of the sample A batch-type electrochemical measurement method, in which the familiarity between the coexisting electrolyte and the working electrode changes with time by keeping at least the working electrode immersed or wet with an organic preservation solution when not measured. Since the potential of the working electrode is kept at a constant potential difference from the potential of the solid reference electrode, the variation in the current value that flows when the electrode is immersed in the coexisting electrolyte is kept to a minimum value. This provides an advantageous effect of preventing variation in data immediately after the electrode is immersed in the coexisting electrolyte.
[0043]
According to the electrochemical measurement method according to claim 3, in the electrochemical measurement method according to claim 1 or 2, the organic preservation solution is an electrolyte for measurement. Organic Containing at least one of the solvent component, the electrolyte component of the electrolyte for measurement, the reversible redox reagent, and the substance to be measured, and stored on the electrode surface when the electrode is immersed in the coexisting electrolyte Since the replacement of the solution and the coexisting electrolyte is performed smoothly, an advantageous effect is obtained that it is possible to prevent variation in data immediately after the electrode is immersed in the coexisting electrolyte.
[0044]
According to the electrochemical measurement method of claim 4, in the electrochemical measurement method of claim 3, when the measurement target substance is a carboxylic acid, it is stored by the carboxylic acid previously given to the storage solution. There is an advantageous effect that the concentration is uniformized quickly from the carboxylic acid concentration in the solution to the carboxylic acid concentration in the coexisting electrolyte. In addition, even if the carboxylic acids are different carboxylic acids, the reduction potentials are almost the same. Therefore, the current flowing between the working electrode and the counter electrode is almost governed by the total acidity of all carboxylic acids. If an acid is contained, the concentration of all carboxylic acids can be made uniform quickly.
[0045]
According to the electrochemical measurement method of claim 5, in the electrochemical measurement method of claim 3 or 4, the reversible redox reagent is quinone, so that the electrode is immersed in the coexisting electrolyte. When the preservation solution on the electrode surface is replaced with the coexisting electrolyte, the concentration of quinone in the preserving solution is quickly made uniform from the quinone concentration in the preserving solution to the quinone concentration in the coexisting electrolyte. The advantageous effect of being carried out is obtained.
[0046]
According to the electrochemical measurement method according to claim 6, in the electrochemical measurement method according to any one of claims 3 to 5, the organic preservation solution contains a denatured alcohol. Is advantageous in that it is inexpensive.
[0047]
According to the electrochemical measurement method of claim 7, in the electrochemical measurement method of claim 1 or 2, the organic preservation solution is a solution having the same component as the measurement electrolyte solution. An advantageous effect is obtained in that the measurement electrolytic solution is used as the liquid and there is no need to prepare it separately.
[0048]
According to the electrochemical measurement method of claim 8, in the electrochemical measurement method of claim 1 or 2, the organic preservation solution is reversibly redox-reducing into a solution having the same component as the electrolyte for measurement. Since the reagent is added, the electrolyte and reversible redox reagent previously applied to the storage solution when the storage solution on the electrode surface is replaced with the coexisting electrolyte when the electrode is immersed in the coexisting electrolyte Thus, the concentration of the electrolyte and the reversible redox reagent in the storage solution to the concentration of the electrolyte and the reversible redox reagent in the coexisting electrolytic solution can be quickly achieved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a measurement cell when measuring acidity.
FIG. 2 is a configuration diagram showing an electrode storage state during non-measurement.
FIG. 3 is a block diagram showing a coexisting electrolyte not mixed with a sample when not measured.
FIG. 4 is a graph showing acidity measurement values when an electrode stored in a dry state is used.
FIG. 5 is a graph showing acidity measurement values when an electrode immersed and stored in a storage solution is used.
FIG. 6 is generated between the working electrode and the counter electrode when the voltage between the working electrode and the counter electrode is swept so that the voltage changes at a constant speed by monitoring the voltage of the working electrode and the solid reference electrode. Graph of measured current value
[Explanation of symbols]
1 Counter electrode
2 Working electrode
3 Solid reference electrode
4 Coexisting electrolyte
5 measuring containers
6 Measurement cell
7 Stock solution
8 Storage container
9 Sample-free mixed electrolyte
10 Container cover

Claims (8)

Using a working electrolyte, a counter electrode, and a solid reference electrode immersed in a coexisting electrolytic solution in which an electrolyte is mixed with an organic solvent and a measurement sample, a reversible redox reagent, and the potential of the working electrode is Batch-type electrochemistry that measures the acidity of the measurement sample by detecting the current flowing between the working electrode and the counter electrode while setting the potential to sweep within a predetermined potential difference from the potential of the solid reference electrode An electrochemical measurement method, wherein at least the working electrode is kept in a dipped state or a wet state with an organic preservation solution when not measured. Using a working electrolyte, a counter electrode, and a solid reference electrode immersed in a coexisting electrolytic solution in which an electrolyte is mixed with an organic solvent and a measurement sample, a reversible redox reagent, and the potential of the working electrode is A batch-type electrochemical measurement method for measuring the acidity of the measurement sample by detecting a current flowing between the working electrode and the counter electrode while maintaining a constant potential difference from the potential of the solid reference electrode. In the non-measurement, the electrochemical measurement method is characterized in that at least the working electrode is kept in a dipped or wet state with an organic preservation solution. The organic preservation solution contains at least one component of an organic solvent component of the measurement electrolyte solution, an electrolyte component of the measurement electrolyte solution, the reversible redox reagent, and a measurement target substance. The electrochemical measurement method according to claim 1, wherein the method is electrochemical. The electrochemical measurement method according to claim 3, wherein the measurement target substance is a carboxylic acid. The electrochemical measurement method according to claim 3 or 4, wherein the reversible redox reagent is quinone. 6. The electrochemical measurement method according to claim 3, wherein the organic preservation solution contains a denatured alcohol. The electrochemical measurement method according to claim 1, wherein the organic preservation solution is a solution having the same component as the measurement electrolytic solution. The electrochemical measurement method according to claim 1 or 2, wherein the organic preservation solution is a solution obtained by adding the reversible redox reagent to a solution having the same component as the measurement electrolyte. .

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