JP2001050924A - Flow cell for electrochemical measurement and electrochemical measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably achieve measurement over a long time and to measure wide range of chemical species by a boron-doped diamond electrode, where boron has been added as the operation electrode of a flow cell. SOLUTION: For example, a flow cell 4 of a liquid-injection type electrochemical measuring device is provided with, for example, a counter electrode 6 using a conductive diamond electrode created by performing the vapor growth of diamond, where boron has been added as a dopant by the micro plasma CVD on a silicon substrate. The conductive diamond electrode is preferably subjected to anode oxidation treatment in acid or alkali electrolyte. Then, sample solution made of a sample and buffer liquid is introduced into the flow cell 4, and a voltage is applied between the operation electrode 6 and a counter electrode 5 for specific analysis, thus obtaining the same value by repeated measurement, without leaving the history of the sample of the operation electrode 6 and performing measurement over a wide potential range for preferably measuring histamine or the like with high oxidation potential.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow cell using a conductive diamond electrode as a working electrode and an electrochemical measuring device using the flow cell.
It is also suitable for analysis of electrochemically active species, for example, species having a high oxidation potential such as histamine.

[0002]

[Prior art] Histamine is an essential amine for life support, and many vegetables and fruits naturally exist in small amounts.
Not toxic. But beer, cheese,
In fermented foods such as fish and wine, which have been pickled in oil for preservation, the amount of histamine increases if preservation is not sufficiently performed during preservation, causing damage to the gastrointestinal tract, blood circulation, nerves, etc. Sometimes. Histamine is a chemical mediator that causes vasoconstriction and many allergic reactions due to obesity. Therefore, detection of histamine is extremely important.

In recent years, a measurement method using an electrochemical technique has attracted attention. Among them, a flow type cell is used, and continuous measurement can be performed by combining with a liquid chromatography. Chemical measurement devices are widely used.

In the electrochemical measurement using a flow cell, a sample solution in which a sample is mixed in a buffer solution is introduced into the flow cell by a pump or the like, and a voltage is applied between the working electrode and the counter electrode in the flow cell. Analyzes the components in the sample solution and transmits the signal obtained by the electrochemical reaction between the working electrode and the counter electrode to a measuring device consisting of a potentiogalvanostat, an analyzer (a personal computer, etc.), etc. By performing processing such as control, analysis, and analysis, the result of electrochemically measuring the sample is obtained. Here, the buffer is a solution added to easily perform an electrochemical measurement, for example, a solution used to control a hydrogen ion exponent (pH) of a sample solution.

In this type of electrochemical measurement apparatus, for example, when analyzing NADH (dihydronicotinamide adenine dinucleotide), a glassy carbon electrode is generally used as a working electrode material of a flow cell.

The reason for using glassy carbon as a working electrode is that it has good electrical conductivity, is stable to chemicals, has the same properties as pyrolytic graphite in that it does not pass gas, and is inexpensive, and produces hydrogen and oxygen. Overvoltage is relatively large.
It is said that.

[0007]

However, since the electrochemical oxidation of histamine is caused by a high potential, it is considered that analysis is difficult with a conventional electrochemical measurement apparatus using glassy carbon or the like as a working electrode. Can be

Further, it has been found that when the glassy carbon electrode is used repeatedly or for a long time, the measurement accuracy is reduced, and there is a problem that a stable and accurate measurement cannot be performed for a long time.

That is, FIG. 11 shows the results of analysis of 50 μM NADH in 0.1 M buffer of pH 7 using an electrochemical measurement device using a glassy carbon electrode as the working electrode of the flow cell. As shown in the figure, it can be seen that there is a large difference in the potential characteristics between the initial stage of analysis using a new glassy carbon electrode and one hour after the start of analysis.

Therefore, the present invention relates to a substance (buffer or the like) used for buffering action in a sample solution even when used for a long time.
Provided is a flow cell for electrochemical measurement, which is capable of performing stable measurement without being affected by oxidization, and is also suitable for detecting a chemical species having a high oxidation potential such as histamine, and an electrochemical measurement apparatus using the flow cell. Things.

[0011]

In order to solve the above problems, the present invention introduces a sample solution, applies a voltage between a working electrode and a counter electrode, and analyzes the sample solution electrochemically.
A conductive diamond electrode is used as a working electrode of an electrochemical measurement flow cell that performs an electrochemical measurement continuously by discharging a sample solution.

A boron-doped diamond electrode doped with boron is used as the conductive diamond electrode.

Further, as the conductive diamond electrode,
It is also possible to use a conductive diamond electrode whose surface has been subjected to anodic oxidation treatment by placing a conductive diamond electrode in an electrolytic solution of either an acid or an alkali and flowing an amount of electricity causing an oxidation reaction to the conductive diamond electrode.

Further, the sample solution is introduced, a voltage is applied between the working electrode and the counter electrode, the sample solution is analyzed electrochemically, and then the sample solution is discharged to perform the electrochemical measurement continuously. The flow cell for electrochemical measurement to be performed and the signal from the electrodes of the flow cell connected to this flow cell
In an electrochemical measurement device comprising a measurement device for detection and analysis, a flow cell for electrochemical measurement using a conductive diamond electrode as a working electrode is used as a flow cell for electrochemical measurement.

Further, in this electrochemical measurement device, a buffer solution introducing means for introducing a buffer solution into the flow cell;
A sample injection valve for injecting a sample to be analyzed is provided between the buffer introducing means and the flow cell, and a sample solution is introduced into the flow cell by injecting the sample from the sample injection valve.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In recent years, it has been found that diamond has excellent (stable) electrochemical properties, and is expected to replace the conventional carbon-based electrodes.

Although diamond itself is a good insulator having a high resistance, if boron or the like is doped as an impurity, the resistivity decreases, and by changing the boron doping amount, the conductivity from semiconducting to metallic conductivity can be improved. It has been confirmed that sex can be controlled.

Attention has been paid to the boron-doped diamond electrode doped with boron at a high concentration because of its advantageous properties such as a wide potential window and a low background current as compared with other electrode materials. It is believed that the wide potential window that has been collected allows for the detection of electrochemical oxidation at high potential.

Here, as an example of a method for producing a boron-doped diamond electrode (hereinafter referred to as a conductive diamond electrode), microwave plasma assisted CVD is used.
The fabrication method by the method will be briefly described. As a film forming apparatus, a microwave CVD film forming apparatus manufactured by ASTeX was used.

The conductive diamond electrode generates hydrogen plasma in a chamber filled with hydrogen gas, introduces a mixed gas of acetone and methanol in which boron species is dissolved, and introduces a carbon source. By conducting vapor phase growth on a conductive (or semiconductive) substrate.

First, as a substrate, a silicon substrate ｛Si
After the surface of the substrate was textured (for example, polished with 0.5 μm diamond powder) using (100)）, the substrate was set in a holder of a film forming apparatus. As a source for film formation, a mixture of acetone and methanol (liquid, mixing ratio 9: 1 by volume) is used, and boron oxide (B ₂ O ₃ ) is added to this mixture in a boron / carbon (B / C) ratio. 10 ⁴
What dissolved the amount used as ppm was used.

Then, after passing pure H ₂ gas as a carrier gas through the film-forming source, the gas is introduced into the chamber, and hydrogen (532c in this embodiment) is previously supplied through another line.
c / min) and a predetermined pressure (1 in this embodiment).
15 Torr = 115 × 133.322 Pa). Then, after injecting and discharging microwave power of 2.45 GHz, the power was adjusted to be 5 kW. Then, when stable, pure H ₂ gas (in the present embodiment,
(15 cc / min) to form a film. The film forming speed at this time was 1 to 4 μm / h. By adjusting the time, a film having a thickness of about 30 μm was obtained. In this apparatus, heating of the substrate was not particularly performed, but approximately 850 in a steady state.
９950 ° C.

Next, the results of various analytical measurements performed using the conductive diamond thin film electrode obtained by the above-described manufacturing method will be described.

The conductive diamond electrode is a high-concentration boron-doped diamond thin-film electrode with a boron: carbon ratio of 10 ⁴ ppm.

First, similarly to the glassy carbon electrode described above, 50 μM NA in a 0.1 M buffer solution of pH 7 was used.
When the DH was analyzed, the results shown in FIG. 1 were obtained.

As can be seen from the results shown in FIG. 1, when the conductive diamond electrode was used, the analysis was started, and
It was confirmed that even after a lapse of time, the same characteristics as the potential characteristics at the initial stage of analysis with a new conductive diamond electrode were obtained.

The analysis was further continued, and the same potential characteristics could be confirmed three months after the analysis.

This is considered to be because diamond has an extremely stable structure which is not affected by dissolved oxygen and the like in the sample solution.

Further, when the change in the peak current when the concentration of NADH in the buffer solution was changed was measured, it was found that both were in a proportional relationship as shown in FIG.
It was confirmed that the peak current according to the change in the concentration of ADH was correctly measured.

In the graph of FIG. 2, when the concentration of NADH is 50 μM, the peak current is about 1.2 μA, which is the same as the peak current in FIG.

Based on these confirmed characteristics, the applicant considers that the conductive diamond electrode is excellent as a sensor material, and uses the conductive diamond electrode in a liquid injection type electrochemical measurement using a hood cell for electrochemical measurement. An attempt was made to construct a device (flow injection analyzer).

In the flow injection analysis, a controlled continuous flow is created using a metering pump or the like, and various reactions, separation, sample injection, and the like are performed in the flow, and the flow is analyzed by a detector having a flow cell installed at the end. It is known as a method for analyzing components in a solution.

FIG. 3 is a schematic diagram showing an electrochemical measuring apparatus using a conductive diamond electrode as a working electrode of a flow cell. In the figure, reference numeral 1 denotes a buffer tank containing a buffer, and 2 denotes a pump for liquid chromatography. (Hereinafter referred to as a pump), the buffer solution tank 1 and the pump 2 constitute a buffer solution introducing means. Reference numeral 3 denotes an injection valve for injecting a sample, and 4 denotes a flow cell incorporating a counter electrode 5, a working electrode 6, and a reference electrode 7, respectively. Reference numeral 8 denotes a potentiogalvanostat that controls / detects a signal at each electrode, and 9 denotes an analyzer (such as a personal computer) that performs various types of analysis based on the signal. .

In the present embodiment, a thin film electrode prepared by vapor-growing diamond doped with 10 ⁴ ppm of boron by microwave plasma CVD on a silicon substrate is used as a conductive diamond electrode. However, any boron doping amount and electrode shape can be used depending on various conditions such as the application and the configuration of the flow cell.

The electrochemical measuring device thus configured is
The buffer solution is sent from the buffer solution tank 10 to the flow cell 13 side by the pump 11, and at this time, a sample to be measured or the like is injected from the injection valve 12. Then, the sample solution comprising the sample and the buffer is introduced into the flow cell 13 and the flow cell 1
By applying a voltage between the working electrode 13 and the counter electrode 14 in the sample 3, analysis of components in the sample solution and the like are performed. Measurement and the like are performed.

Using this electrochemical measurement apparatus, NAD having a concentration of 100 μM was used as a sample in a 0.1 M phosphate buffer.
When a change in the current value was measured by injecting 20 μl of H from the injection valve 3 at one-minute intervals, a peak current was detected immediately after the sample injection as shown in FIG. The current value decreased, and the same current characteristic was detected every time NADH was injected thereafter.

From this, it was confirmed that the electrochemical measurement device using the injection valve accurately analyzed the sample injected from the injection valve 3.

The experimental conditions were set at a set potential of 600 mV.
(VS. Ag / AgCl), and the flow rate was 1 ml / min.

Next, using the same apparatus, a lower concentration of 1 μM, 100 nM, 50 μM in 0.1 M phosphate buffer was used.
As a sample, NADH of each concentration of nM (20 μl) was injected from the injection valve 3 at one-minute intervals, and changes in the current value were measured. As shown in FIGS. 5 (a), (b), and (c), each concentration was measured. , A peak current was detected immediately after injection.

The experimental conditions were the same as above, with a set potential of 600 mV (VS. Ag / AgCl) and a flow rate of 1 ml / mi.
n.

From these results, it was confirmed that the analysis could be performed accurately even when the concentration of the sample was extremely low.

As is clear from the results shown in FIGS. 4 and 5, the conductive diamond electrode has no previous history of the analyzed sample, and the same measurement result is obtained each time the sample is repeatedly injected. I understand. This is probably because the surface of the conductive diamond electrode is extremely stable, and the sample does not adhere to the electrode surface. That is, the sample after analysis is not adsorbed on the electrode surface and the cell 4
This characteristic is extremely preferable as an electrode for a flow cell for continuously analyzing a sample.

Next, a sample solution obtained by injecting 20 μl of 100 μM NADH into 0.1 M phosphate buffer at pH 7.2 was controlled by the pump 11 to flow the current, and the relationship between the current and the potential (voltanogram). Was examined.

The experimental conditions were set at a set potential of 600 mV (V
S. Ag / AgCl) and the flow rate was 1 ml / min.

As a result, the result shown by line A in FIG. 6 was obtained, and the set potential was 600 mV (VS. Ag / AgCl).
It was confirmed that the current value was substantially saturated.

The line B in FIG. 6 shows the result of examining the relationship between the current and the potential (voltangram) by flowing only the phosphate buffer.

From the results shown in FIG. 6, it can be confirmed that NADH has been analyzed, and from the results of measurement by flowing only a phosphate buffer, the value of the background current of the conductive diamond electrode is extremely small. Was confirmed.

That is, when performing analysis using a flow cell in general, there is a problem that the pulsation has a great influence on the analysis. However, from the results of FIG. Is extremely small, it has been confirmed that the use of this as a working electrode of a flow cell has an extremely small influence of pulsation and enables more accurate analysis.

Next, histamine was analyzed using a boron-doped diamond thin film electrode doped with boron at a high concentration (hereinafter referred to as a conductive diamond electrode) as a working electrode in electrochemical measurements.

As the conductive diamond electrode, the same microwave plasma assisted CVD apparatus as described above was used.
What was produced by forming a film on a silicon substrate {Si (100)} was used. As a source for film formation, a mixture of acetone and methanol (liquid, mixing ratio 9: 1 by volume) is used, and boron oxide (B ₂ O ₃ ) is added to this mixture in a boron / carbon (B / C) ratio. A solution obtained by dissolving 10 ⁴ ppm was used.

The conductive diamond electrode prepared under the above conditions was used as a working electrode of an electrochemical measuring device.
Was analyzed for histamine at a concentration of 100 μM in 0.1 M phosphate buffer.

For comparison with a diamond electrode,
The analysis was also performed under the same conditions using a glassy carbon electrode as the working electrode.

FIG. 7 shows a linear sweep voltammogram (relationship between current and potential) analyzed under the above-mentioned conditions. From the results, it can be seen that the use of the conductive diamond electrode resulted in the use of the glassy carbon electrode. No background current (background current) appears up to a higher potential than in the case, for example, a potential of 1300 mV
It was confirmed that the background current in (VS. SCE) was larger in glassy carbon than in the conductive diamond electrode, and that the conductive diamond electrode had a wider potential window than the glassy carbon electrode.

That is, when the conductive diamond electrode is used, the background current does not appear up to a higher potential than when the glassy carbon electrode is used, and the conductive diamond electrode has a wider potential window than the glassy carbon electrode. (A region in which the solvent does not decompose).

When 500 μM histamine was analyzed, the S / B (signal / background current) ratio of the diamond electrode was 10 times that of glassy carbon even without pretreatment (anodizing treatment described later). large.

Next, histamine flow injection analysis was performed by an electrochemical measurement method using a conductive diamond electrode.

A conductive diamond electrode was used as a working electrode of the flow cell, and 100 μM histamine 2 was used as a sample.
0 μl was injected at 1 minute intervals, and the current characteristics were measured.
The experimental conditions used were a phosphate buffer as a buffer, a set potential of 1.3 V (VS. Ag / AgCl), and a flow rate of 0.5 ml / min. FIG. 8 shows the result.

As is clear from the results shown in FIG. 8, when histamine was injected, a peak current was confirmed each time the histamine was injected, and it was confirmed from this result that histamine analysis was performed reliably.

That is, from these results, it was confirmed that the conductive diamond electrode used as the working electrode in the electrochemical measurement device was extremely effective for histamine analysis.

Further, using this electrochemical measurement apparatus, 1
An attempt was made to analyze very small amounts (low concentrations) of histamine such as μM, 10 μM, 20 μM, and 50 μM.

1 μM in 0.1 M phosphate buffer
, 10 μM, 20 μM, and 50 μM of histamine of each concentration were sequentially injected from the injection valve 3 at one-minute intervals, and the change in the current value was measured. As shown in FIG. Peak current was detected.

The experimental conditions were set at a set potential of 1275 mV.
(VS. Ag / AgCl), and the flow rate was 1 ml / min.

Further, under the same conditions as above, 100 μm
When a histamine at M concentration was injected and the peak current value was measured, the peak current value was 437.096 nA.

FIG. 9 (b) shows the relationship between each concentration and the peak current value based on the results shown in FIG. 9 (a) and the results when 100 μM histamine was injected. From the graph and the empirical formula described in the graph, it was found that the concentration of histamine and the peak current value were in a proportional relationship, and it was confirmed that from a very low concentration of histamine to a high concentration of histamine, accurate measurement was possible. .

As described above, according to the present invention, by using a conductive diamond electrode doped with boron as the working electrode of the flow cell, the accurate electric potential of histamine can be improved due to the wide potential window of the conductive diamond electrode. An electrochemical measurement device capable of performing a chemical measurement can be obtained.

Further, when the potential windows of the conductive diamond electrode, glassy carbon electrode, platinum electrode, and gold electrode were compared in a 0.5 M sulfuric acid aqueous solution, the results shown in FIG. 10 were obtained. In addition, it was confirmed that the potential window of the conductive diamond electrode was much wider than that of the glassy carbon electrode, the platinum electrode, and the gold electrode.

When the residual current (current used for double layer charging) density in the potential window region was measured, the diamond electrode had a density of several tens to several hundreds nA / cm ² and a residual current density of several μA / cm ^2. It was confirmed that it was extremely small as compared with other metal electrodes of cm ² .

The electrochemical response of the conductive diamond electrode to the redox species was good, and the current density flowing according to the redox reaction was comparable to that of the metal electrode.

An attempt was made to apply anodizing treatment to the conductive diamond electrode, and various analyzes and the like as described above were performed using the conductive diamond electrode subjected to the anodizing treatment. Was obtained.

In particular, when an attempt was made to analyze uric acid contained in urine, uric acid which was difficult to discriminate with a conductive diamond electrode which had not been oxidized, and ascorbic acid which coexisted in urine, were used. Could be identified and detected.

From these results, it was found that it is more preferable to use a conductive diamond electrode subjected to anodic oxidation treatment as the working electrode of the flow cell when, for example, combining with liquid chromatography.

As a method of anodizing the conductive diamond electrode, the conductive diamond electrode is set up in an electrolytic solution of either acid or alkali, for example, a 0.1 M KOH solution, and is set to 2.4 V (VS. (SCE) for 75 minutes. At this time, if necessary, from +4 V to -4 V in a 0.1 M KOH solution.
After sweeping (VS. SCE) three times at a speed of 0.1 V / sec, a process of holding at 4 V for one minute is performed. In the present embodiment, a 0.1 M KOH solution was used as an electrolytic solution, but H ₂ SO ₄ , HClO ₄ , H
NO ₃ and HCl can be used, and NaOH and the like can be used as the alkali.

From the above results, the conductive diamond electrode has a wide potential window and is extremely superior to other electrodes used as a sensor material, and it can be used in a flow cell for electrochemical measurement. Due to the unique characteristics of conductive diamond electrodes, such as that the sample does not adhere to the electrode surface, the value of the background current is extremely small, and the influence of pulsation is extremely small, the flow cell for electrochemical measurement and the electrochemical measurement device are used. It was confirmed that it was obtained.

Then, by combining this with liquid chromatography, various electrochemical measurements can be performed.

[0075]

As described above, according to the present invention, by using a boron-doped conductive diamond electrode as a working electrode of a flow cell, it is possible to obtain a stable electrochemical for a long time without leaving a history of the analyzed sample. The flow cell for electrochemical measurement and the electrochemical measuring device capable of performing electrochemical measurement and capable of electrochemical measurement of a wide variety of chemical species can be obtained from the wide potential window of the conductive diamond electrode.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing an electrochemical oxidation reaction of NADH (50 μM) at a conductive diamond electrode in a 0.1 M aqueous buffer (pH 7).

FIG. 2: NA analyzed using a conductive diamond electrode
FIG. 4 is a characteristic diagram showing a result of measuring a relationship between a DH concentration and a peak current.

FIG. 3 is a conceptual diagram of an electrochemical measurement device (flow injection analyzer) using a conductive diamond electrode according to an embodiment of the present invention.

FIG. 4 shows a result of measuring a change in a current value when 20 μl of NADH having a concentration of 100 μM was injected from an injection valve at an interval of 1 minute in a 0.1 M phosphate buffer using an electrochemical measurement apparatus according to an embodiment of the present invention. FIG.

FIG. 5 shows a diagram of an electrochemical measurement apparatus according to an embodiment of the present invention.
FIG. 11 is a characteristic diagram showing the results of measuring the change in current value when 20 μl of NADH at each concentration of nM and 50 nM is injected from the injection valve at one-minute intervals.

FIG. 6: 100 μM NAD in 0.1 M phosphate buffer using an electrochemical measurement device according to an embodiment of the present invention.
FIG. 6 is a characteristic diagram showing the results of measuring the relationship between current and potential when a sample solution into which 20 μl of H was injected was flowed at a flow rate of 0.5 ml / min.

FIG. 7 is a graph showing a pH value of pH 7 measured by an electrochemical measurement apparatus using a conductive diamond electrode and a glassy carbon electrode.
FIG. 9 is a characteristic diagram showing the results of measuring the relationship between current and voltage when 100 μM histamine was injected into a 1 M phosphate buffer.

FIG. 8 is a characteristic diagram showing a result of measuring current characteristics by injecting 100 μM histamine as a sample at one-minute intervals using the electrochemical measurement device according to the embodiment of the present invention.

FIG. 9 (a) shows an example of the use of an electrochemical measurement apparatus according to an embodiment of the present invention, wherein 50 μm
M, 20 μM, 10 μM, and 1 μM histamine at a concentration of 20 μl were injected from the injection valve at 1-minute intervals from the injection valve to obtain a characteristic diagram showing the results of measurement of the change in current value. FIG. Graph.

FIG. 10 is a diagram showing a comparison result of potential windows of a conductive diamond electrode, a glassy carbon electrode, a platinum electrode, and a gold electrode in a 0.5 M sulfuric acid aqueous solution.

FIG. 11: 50 μm in a 0.1 M buffer at pH 7 by an electrochemical measurement device using a glassy carbon electrode.
FIG. 9 is a characteristic diagram showing the result of analyzing M concentration of NADH.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Buffer layer 2 ... Pump for liquid chromatography 3 ... Injection valve 4 ... Flow cell 5 ... Counter electrode 6 ... Working electrode (conductive diamond electrode) 7 ... Reference electrode 8 ... Potential galvanostat 9 ... Analysis device 10 ... Measuring device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tata Narasinga Lao Room No. 22, 610, Honari 4-chome, 4-Chome, Misato-shi, Saitama Prefecture Room F term (reference) 2G060 AA06 AD06 AE17 AF02 AF15 AG01 FA01 FB02 HE01 KA06

Claims (5)

[Claims] 1. A sample solution is introduced, a voltage is applied between a working electrode and a counter electrode, the sample solution is analyzed electrochemically, and then the sample solution is discharged to perform a continuous electrochemical measurement. The flow cell for electrochemical measurements to be performed, wherein a conductive diamond electrode is used as the working electrode. 2. The flow cell for electrochemical measurements according to claim 1, wherein the conductive diamond electrode is a boron-doped diamond electrode doped with boron. 3. An anodizing treatment is performed on the surface of the conductive diamond electrode by placing the conductive diamond electrode in an electrolytic solution of either an acid or an alkali, and supplying an amount of electricity that causes an oxidation reaction to the conductive diamond electrode. The flow cell for electrochemical measurements according to claim 1 or 2, wherein the flow cell is applied. 4. A sample solution is introduced, a voltage is applied between the working electrode and the counter electrode, the sample solution is analyzed electrochemically, and then the sample solution is discharged to perform the electrochemical measurement continuously. An electrochemical measurement apparatus comprising: a flow cell for electrochemical measurement to be performed; and a measurement device connected to the flow cell and controlling, detecting, and analyzing a signal from an electrode of the flow cell. 3
An electrochemical measurement apparatus characterized in that an electrochemical measurement flow cell using a conductive diamond electrode as the working electrode according to (1) is used. 5. A method according to claim 1, further comprising a buffer introducing means for introducing a buffer into the flow cell, a sample injection valve for injecting a sample to be analyzed provided between the buffer introducing means and the flow cell, and a sample injected from the sample injection valve. The electrochemical measurement device according to claim 4, wherein the sample solution is introduced into the flow cell by injecting the sample solution.