JPH07134116A - Chemical substance detecting method - Google Patents

Abstract

PURPOSE:To identify chemical substances in gas phase. CONSTITUTION:Measuring electrodes 20, 22 and a reference electrode 26 are formed in the lower face of a measuring part 10 and a solution supplying pipe is opened in the lower face. Attributed to the surface tension, the electrolytic solution is kept on the electrolytic solution keeping surface 21 at the lower end of the measuring part 10 by suppling the predetermined electrolytic solution from the solution supplying pipe and thus a gas reception part is obtained. Since the electrolytic solution is directly exposed to air, substances in the gas phase (especially odorous substances) are diffused to the part. The electric condition alteration of the measuring electrodes 20, 22 attributed to the diffusion is detected. Since the electric condition alteration with the lapse of time is different depending on each chemical substance, the chemical substance in the gas phase can be identified by distinguishing the pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a chemical substance by a gas phase sensor for detecting a substance contained in a gas phase.

[0002]

2. Description of the Related Art Conventionally, gas chromatography or the like has been used to detect substances contained in a gas phase, and the concentrations of various substances in sampled gases are detected. However, this method using gas chromatography is based on the fact that a person samples a sample, and is not suitable for automatically detecting a substance in a gas phase.

Therefore, depending on the concentration of the substance in the gas phase,
A plurality of electrodes whose electric state (normally, potential / current depending on changes in redox potential) change are installed in the gas phase,
A gas phase sensor is known which detects the amount of a substance in the gas phase by detecting this electrical state. If such a gas phase sensor is used, the desired gas concentration can be detected simply by installing the sensor in the atmosphere to be detected. The concentration of the gas to be measured can be measured by using a gas-selective film or the like.

Such a gas phase sensor is disclosed, for example, in Japanese Patent Laid-Open Nos. 5-10905, 5-60727, and 5-45321.

[0005]

However, the detection of a chemical substance by such a conventional sensor basically only measures a change in potential or current, and one sensor can measure: There is a problem in that it is not possible to identify a substance because it is only the change in the concentration of a single gas or the total potential or current of a plurality of gases.

[0006] It is an object of the present invention to provide a method for detecting a chemical substance capable of identifying the chemical substance contained in the gas phase.

[0007]

A method for detecting a chemical substance according to the present invention comprises a step of holding an electrolyte solution having a surface which is in direct contact with a gas phase around an electrode, and a chemical substance in the gas phase being dissolved in the electrolyte solution. Having a step of diffusing into it, and a step of detecting an electrical state at an electrode present in this electrolyte solution as a time-dependent change based on diffusion of the chemical substance and adsorption to the electrode, based on the detected time-dependent change It is characterized by detecting a chemical substance in the gas phase (Claim 1).

Further, the step of holding the electrolyte solution around the electrodes is to hold the electrolyte solution by utilizing its surface tension. By supplying the electrolyte solution from the electrolyte solution supply source, a new electrolyte solution is prepared. It is characterized in that the detection is repeated by holding it (Claim 2).

Further, the method for identifying a chemical substance according to the present invention is a method for identifying a chemical substance contained in a gas phase,
A step of holding an electrolyte solution having a surface that is in direct contact with the gas phase around the electrode, and a step of obtaining a predetermined fitting function and parameters from a chemical substance selected as a reference substance, the chemistry selected as the reference substance. A step of diffusing a substance in an electrolyte solution, and detecting an electrical state at an electrode present in the electrolyte solution as a temporal change due to diffusion of the chemical substance and adsorption to the electrode, and a pattern of the temporal change of the electrical state. And a step of setting a fitting function based on this pattern and obtaining a parameter of each reference substance for this fitting function, and a step of obtaining a predetermined parameter from the chemical substance to be measured. The process of diffusing the chemical substance to be measured into the electrolyte solution and the electrodes present in this electrolyte solution. An electrical state is detected as a change over time based on adsorption to diffusion and electrode of the chemicals,
A step of creating a parameter of the measurement target substance for the fitting function; and calculating a distance between various parameters of the reference substance and the parameter of the measurement target substance, and measuring the reference substance having the minimum distance. And a step of determining that it is most similar to the target substance (claim 3).

[0010]

In the method of detecting a chemical substance according to the present invention having the above-described structure, the change with time of the changing electrical state is detected by the chemical substance that diffuses into the retained electrolyte solution. Then, this change with time differs depending on each chemical substance. Therefore, the chemical substance can be identified by this change.

In this case, if the electrolyte solution is held by the surface tension (claim 2), it can be updated by supplying the electrolyte solution. Therefore, analysis of a new pattern and identification of chemical substances are possible. Can be repeated.

Further, in the chemical substance identifying method according to the third aspect, the homology of the temporal change pattern of the electrical state is quantified and presented, and the degree of similarity of the chemical substances is judged based on the quantified homology. Specifically, the patterns of changes in the electrical state with time are compared by comparing the distances of the parameters with respect to the fitting function.
Pattern homology is quantified as the distance between the parameters.

That is, according to the method for identifying a chemical substance according to claim 3, the patterns of the reference substance and the substance to be measured (patterns of change in electrical state with time) are respectively obtained by using the detection method according to claim 1. Created. Then, for these reference substances, an appropriate fitting function is derived based on the patterns of a plurality of different reference substances, and at the same time, the parameters of each reference substance for the fitting function are calculated. On the other hand, also for the chemical substance to be measured, the parameter for the fitting function is calculated. Then, the distance between the parameters of the reference substance and the measurement target substance is calculated, and those having a short distance are determined as substances having a high degree of similarity. For example, a measurement target substance having a parameter close to that of ethanol is determined to be a compound similar to ethanol, and a substance having a distant parameter is determined not to be similar to ethanol. Of course, if the parameters are the same, it is identified as ethanol. The distance between parameters can be calculated from n parameters. Examples of the method (measurement method) of calculating the distance between the parameters include Euclidean distance, square Euclidean distance, Chebyshev distance, or 1-correlation coefficient calculation method.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

[Apparatus Configuration] FIG. 1 is a diagram showing the overall configuration of a gas phase sensor according to an embodiment, and FIG. 2 is an enlarged view showing the configuration of a measuring unit 10.

The measuring unit 10 includes two platinum electrodes 12, 14
And two fluororesin pipes 16 and 18 with epoxy resin 19
Is formed by solidifying with the lower surface of the electrolyte solution holding surface 21.
Is formed. Then, the first and second measurement electrodes 20 and 22 made of different conductive polymer films are formed on the lower surfaces of the platinum electrodes 12 and 14, respectively. That is, in the present embodiment, the first measuring electrode 20 made of a PPy / PVS (polypyrrole sulfate ion-doped polypyrrole) film is formed on the lower surface of the platinum electrode 12, and PPy / is formed on the lower surface of the platinum electrode 14.
The second measurement electrodes 22 are each formed of a Cl (chloride ion-doped polypyrrole) film. The platinum electrodes 12 and 14 may be formed of platinum disks only at their lower ends. Further, the conductive polymer film is formed by electrolytic polymerization or chemical polymerization.

Further, 3M (mo
A salt bridge 29 made of 1 / l) KCl (potassium chloride) and 3% agar is provided, and a silver-silver chloride electrode 24 is attached to the other end of the salt bridge 29 to form a reference electrode 26. ing. Generally, the silver-silver chloride electrode 24 and the entire solution containing chloride ions are referred to as reference electrodes, but since they are substantially the same, the lower end of the salt bridge 29 is referred to as the reference electrode 26 as it is in this embodiment. The operation will be described. On the other hand, the fluororesin pipe 18 is connected to the electrolyte solution supply unit 28 via the electrolyte solution supply pipe 18a, and the electrolyte solution is supplied from the lower end of the fluororesin pipe 18 to the electrolyte solution holding surface 21. There is. Electrolyte solution supply unit 2
8 is composed of, for example, an appropriate metering pump and a solution tank. Therefore, when the electrolyte solution is supplied from the lower end to the electrolyte solution holding surface 21, the fluororesin pipe 18 and the lower surface of the salt bridge 29 are electrically connected, and the potential of the electrolyte solution with respect to the reference electrode 26 can be detected. It will be possible. In addition,
In this example, a 1 M KCl aqueous solution is used as the electrolyte solution, but this electrolyte solution may be changed according to the measurement object. When the measurement object is water-insoluble, a suitable solvent other than water is used. select.

The electrolyte solution supply unit 28 stops the supply of a predetermined amount of the electrolyte solution and seals it in a liquid-tight manner. The electrolyte solution is used as the first and second measurement electrodes 20 and 22, and two fluororesin pipes 16 and 18
The electrolyte solution holding surface 21 composed of the lower surface and the lower surface of the epoxy resin 19 is held by its surface tension, and this surface constitutes a gas receiving portion 23 which is a portion directly exposed to the gas phase.

The silver-silver chloride electrode 24 and the platinum electrodes 12 and 14 are connected to the reference electrode input terminal (re) of the amplifier 30.
f), channels 1 (ch1) and 2 (ch2). Then, the amplifier 30 compares the potential of the reference electrode 26 with the potentials of the first and second measurement electrodes 20 and 22, amplifies the difference voltage, and supplies it to the recorder 32. In addition,
The amplifier 30 employs a low-noise DC amplifier and incorporates a filter for extracting a frequency signal of 300 Hz to 1 kHz or less.

The recorder 32 records the signal supplied from the amplifier 30. Further, the control unit 34 controls the electrolyte solution supply unit 2 at predetermined time intervals or in response to a predetermined operator input.
Control the supply of electrolyte solution by 8. The control unit 3
In 4, the measurement result obtained by the recorder 32 is analyzed, and the substance is specified by the method described later.

In addition, in this embodiment, the difference in film composition is 2
It has two measuring electrodes 20, 22. Therefore, simultaneous measurement using the first and second measurement electrodes 20 and 22 makes it possible to know the difference in response due to the difference in film composition. Further, in actual measurement, it is also possible to perform the measurement by utilizing the more suitable measurement result of the measurement electrode 20 or 22.

[Measurement Operation] Detection of a chemical substance using the gas phase sensor having the above-described structure will be described with reference to FIG. First, a predetermined amount of electrolyte solution is supplied from the electrolyte solution supply unit 28, and a predetermined amount of electrolyte solution is held on the electrolyte solution holding surface 21, thereby forming the gas receiving unit 23 (S11).

Next, air containing a stimulating substance is blown onto the gas receiving portion 23 for a predetermined time (S12). This operation is performed as follows, for example. First, 100 μl of a stimulating solution containing a predetermined chemical substance was measured and deodorized filter paper 4
0 (area 5 cm ² ). And this filter paper 40
Is placed in a Pasteur pipette 42, and the rear end of this Pasteur pipette 42 is connected to a pump (not shown) via an odorless tube (not shown).

In this state, air is sent from the pump to cause the stimulating substance evaporated from the filter paper 40 to pass through the gas receiving portion 2 of the gas phase sensor.
Sprinkle on 3. The stimulation time for blowing this gas is 1
~ 20 seconds, flow rate 90 ml / min (wind speed about 1.9 m / s
ec). The stimulation time is controlled by the control unit 34, the flow velocity is monitored by the flow meter, and the control unit 34 performs feedback control. Also, between the pump and the pipette,
A deodorizing pipe containing activated carbon and a dehydrating pipe containing silica gel are arranged, and air from which odor and water vapor are removed is used.

Then, the measurement electrodes 20 and 22 and the reference electrode 2
The change over time of the potential difference of 6 is detected by the recorder (S1
3). Further, the detection result is supplied to the control unit 34,
The control unit 34 analyzes the detection result to identify the chemical substance (S14). An example of the chemical substance identification method will be described later.

When one measurement is completed in this way, it is determined whether or not the next measurement is to be performed (S15), and if it is to be performed, the process returns to S11 to supply the electrolyte solution. As a result, the electrolyte solution held on the electrolyte solution holding surface 21 falls as a cleaning solution, a new electrolyte solution is held on the electrolyte solution holding surface 21, and the gas receiving portion 21 is renewed. Therefore, in this gas sensor, the gas receiving portion 23 is updated by the operation of supplying the electrolyte solution,
The following measurements can be easily performed. In this example, the method of blowing the air containing the stimulating substance to the gas receiving portion 23 is used, but the chemical substance in the gas can be detected by blowing the sampled gas.
Further, by placing the gas sensor in the atmosphere in which the measurement is desired and replacing the electrolyte solution, the chemical substance in the atmosphere can be measured at any time.

[Experimental Results] Next, actual measurement results and identification of chemical substances will be described. Detection was performed using two kinds each of ketones, alcohols, esters, amides, and sulfur-containing compounds as the stimulating liquid. The response is shown in FIG. Here, the vertical axis represents the potential of the measurement electrode and the horizontal axis represents time. The stimulation time was 3 seconds, and the first measurement electrode 20 made of PPy / PVS was used as the measurement electrode.

As shown in FIG. 4, potential responses were obtained for all substances. Moreover, since the response pattern differs depending on the substance, if the patterns of various substances are measured in advance, the chemical substance can be identified by comparing the pattern of the substance to be inspected with the pre-existing pattern. .

Further, since the response patterns of the substances having the same chemical structure (the same kind) with the passage of time have the similar patterns, the identification of the substances to a certain extent, for example, by performing the analysis as described later, for example, When ethanol is given, it can be identified to the extent that it can be identified as alcohols. That is, according to the method of this example, at least the functional group of the compound can be identified.

Further, even when a plurality of chemical substances are mixed, the plurality of chemical substances can be recognized by the predetermined pattern recognition.

As described above, according to the method for detecting a chemical substance of this embodiment, the chemical substance in the gas phase can be identified, so that, for example, the odorant can be identified.

[Analysis of Pattern] As described above, the odorant substance can be identified by observing the homology between the obtained odorant substance pattern and that of the reference substance. Such pattern matching is convenient if it can be quantified, and it is easy to make a judgment. In this embodiment, the pattern homology is mechanically quantified by the following method.

<Reference substance and fitting function> In this example, ethanol, acetone, ethyl acetate and dimethylformamide were used as the reference substances, and a pattern of their changes with time was created, and factors common to these patterns were considered. However, the following fitting function was set. Therefore, by appropriately selecting the parameters of this fitting function, it is possible to create a pattern of any of these four kinds of substances (FIG. 5).

[0034]

[Equation 1] Further, in the embodiment, the parameter specified when setting the fitting function (hereinafter referred to as the first parameter) is processed for analysis to create a new parameter (hereinafter referred to as the second parameter), and based on this, We try to judge the similarity between chemical substances (Fig. 6). In the present embodiment, the first parameter includes factors that require relative comparison, so these are normalized to create the second parameter. In the example, the second parameter is stored in the database (FIG. 6).

<Judgment of Similarity; Cluster Analysis> In this embodiment, the judgment of similarity is performed by the cluster analysis described below. That is, since the number of the second parameters specified in this embodiment is five, the Euclidean distance in five dimensions is calculated and regarded as the similarity. Specifically, the shorter the distance, the higher the similarity. As shown in FIG. 7, the similarity between ethyl acetate and dimethylformamide was about 7 according to this analysis.
It can be seen that it is the most similar chemical substance. Furthermore, acetone has a similarity of about 7 to the closest of ethyl acetate and dimethylformamide. Ethanol shows a similarity of about 11 with the closest one among acetone, ethyl acetate or dimethylformamide.

In this embodiment, ethyl acetate is selected as a representative substance of esters, dimethylformamide as a representative substance of amides, acetone as a representative substance of ketones, and ethanol as a representative substance of alcohols. From the results shown in FIG. 7, it can be generalized that the ester and the amide have the highest similarity, and the ester or the amide is more similar to the ketone than the alcohol. This suggests that classification can be performed according to the type of functional group that the chemical substance has.

In the present embodiment, the Euclidean distance calculation method is adopted as the calculation method (measurement method) of the distance between the parameters, but the calculation method is not limited to this, and in addition to this, Squared Euclidean distance,
A Chebyshev distance or a 1-correlation coefficient calculation method can also be used.

<Example of Identification of Chemical Substance> Next, an example of identifying the substance A to be measured will be described with reference to FIG. In the examples, 2-heptanone is used as the substance A. When the Euclidean distance between the parameters of the substance A and the parameters of the reference substances (ethanol, acetone, ethyl acetate, dimethylformamide) was calculated, a value of about 2.8 was obtained for acetone,
Greater values are obtained for other reference substances. Therefore, it can be seen that the substance A is the compound most similar to acetone among the reference substances, and the similarity to acetone is about 2.8. From this result, it is only known that the substance A is a substance similar to acetone, and its specific chemical structure cannot be determined, but at least it can be inferred that it is a ketone. In this case, substance A is actually 2-heptanone, so this conjecture is correct. It is also understood that the closest similarity between the elements of the group [acetone, substance A] and the group [ethyl acetate, dimethylformamide] is about 7. Therefore, taking this fact into consideration, the chemical structure of substance A is also taken into consideration. It is also effective to use for the judgment of.

When dimethylacetamide is used as the substance B as identification example 2 (FIG. 9), this substance B is judged to be the substance closest to dimethylformamide (similarity about 1). That is, the parameter of substance B is the closest to that of dimethylformamide, and its Euclidean distance is about 1.

<Update of Database> The database can be updated. For example, 1-propanol can be added as the alcohol in addition to ethanol, 2-heptanone as the ketone in addition to acetone, isoamyl acetate as the ester in addition to ethyl acetate, and dimethylacetamide as the amide in addition to dimethylformamide. Here, when ethanol and 1-propanol are added as data, in addition to the identification that the substance to be measured is alcohol, it is possible to identify whether it is closer to ethanol or 1-propanol. Become. For example, when the substance to be measured was methanol, it was identified as closer to ethanol than 1-propanol, and when 1-butanol was measured, it was identified as closer to 1-propanol than ethanol. It In this way, by adding data and updating the database, it becomes possible to identify more finely divided chemical substances.

[Difference in Electrode Film Composition and Difference in Response Pattern] FIG. 11 shows two types of measurement electrodes (PPy / P) for the same substance (in this case, 2-heptanone and ethanol).
The response pattern of VS, PPy / Cl) 20, 22 is shown.

As is apparent from the figure, in 2-heptanone, in PPy / PVS, the response is in the positive direction.
The PPy / Cl film showed no significant response. Regarding ethanol, the PPy / PVS film shows a positive response, while PPy / Cl shows a negative response.

As described above, by changing the kind of the measuring electrode, that is, the kind of the electrolytically polymerized film, different responses can be obtained for the same chemical substance. It is considered that this difference in responsiveness reflects the difference in physicochemical properties of the electropolymerized film. Electropolymerized membranes have different physicochemical properties depending on the ions to be doped, so the response characteristics of more types of membranes should be investigated in advance, and by using a gas phase sensor equipped with these multiple measurement electrodes, The accuracy of chemical substance identification can be improved. Furthermore, the analysis and identification when a plurality of chemical substances are mixed becomes easy.

[Response Amount of Various Substances] Not only the response pattern differs depending on the various substances, but also the amount of potential change at the peak differs. Therefore, the amount of potential change at the peak also serves as a parameter for identifying a substance, like the response pattern. In the present specification, the potential change amount at the peak is expressed as “response amount”.

FIG. 1 shows the response amounts of various substances.
2 shows. Since the amount of response varies depending on the substance in this way, the chemical substance can be detected using this.

Further, FIG. 13 shows response amounts for various alcohols having different carbon numbers. In this way, the response amount increases as the alcohol number decreases. This is considered to reflect the ease of dissolution into the electrolyte solution. Therefore, by changing the composition of the electrolyte solution, it is considered possible to deal with chemical substances having a large carbon number (or molecular weight). For example, by using a solvent that dissolves a hydrophobic substance, a substance having a large number of carbon atoms is likely to be dissolved, and it is considered that this can be easily detected.

Further, FIG. 14 shows the measurement results obtained by using 100 μl of a solution prepared by diluting ethanol with pure water as a stimulating liquid. The vertical axis represents the maximum amount of response, and the horizontal axis represents the dilution ratio of ethanol in logarithm. As you can see from this measurement result,
The sensor of this example exhibits a response that is approximately proportional to the concentration. Therefore, it is understood that the substance can be quantified by utilizing this property.

Here, the measurement of the potential change in FIGS. 12 to 14 is performed by the first measuring electrode 20 made of PPy / PVS.
Is the measurement result.

[Preparation of Measurement Electrode] Next, the measurement electrode 20,
The production of the electropolymerized film in No. 22 will be described based on FIG. Working electrode 5 in which a desired monomer solution 51 is housed in a container 50 and an electrolytic polymerized film is to be formed therein
2 (for example, a platinum electrode) and a counter electrode 54 (counter electrode) are inserted and arranged. Here, the working electrode 52 is formed in a cylindrical shape, and the counter electrode 54 is formed in a hollow cylindrical shape with a partial opening surrounding the working electrode 52. In addition, in the monomer solution 51, the salt bridge 57
It is connected to the reference electrode 56 via. The working electrode 52, the counter electrode 54, and the reference electrode 56 are connected to the power source 58. It should be noted that nitrogen gas is introduced into the container 50.

When forming an electrolytically polymerized film,
First, the monomer solution 51 is stirred with nitrogen gas to remove dissolved oxygen. Next, while maintaining the working electrode 52 at a constant potential with respect to the reference electrode 56 from the power source 58, a desired current is caused to flow by using the working electrode as a positive electrode and the counter electrode as a negative electrode, and the electrolytic polymerized film is formed on the surface of the working electrode 52. Form 60. Here, as a method of applying a voltage, the working electrode 52 and the counter electrode 5 are set so that the working electrode 52 and the reference electrode 56 have a desired constant potential.
A constant potential method for controlling the potential between the four electrodes and a constant current method for flowing a desired constant current between the working electrode 52 and the reference electrode 56 between the working electrode 52 and the counter electrode 54. is there.

In this way, the monomer activated by setting the potential of the working electrode 52 to a predetermined potential (eg, 0.6 V) or more with respect to the reference electrode 56 forms a polymer and deposits on the working electrode 52. . Since this polymer is electrically conductive, when a potential is continuously applied, a new polymer is laminated on this, and an electrolytic polymerized film 60 having a thickness corresponding to the amount of current is formed.

The conditions for producing the electrolytically polymerized film used in this example are shown below.

Monomer solution: electrolytically polymerized film PPy / PV
In the case of S, 0.1M pyrrole + 0.1M potassium polyvinylsulfate (PVS
Aqueous solution of K) Electrolytic polymerized film PPy / Cl 0.1M pyrrole + 0.1MKCl aqueous solution Electrode: Working electrode (+) Platinum disk with a diameter of 1 mm
(Area 0.00785 cm ² ) Counter electrode (−) Platinum plate ・ Electrolysis conditions: Constant current electrolysis ^2.5 mA / cm ²・ Amount of electricity: For example, the following film thickness can be obtained and used. When an experiment was conducted, the sensitivity was better when the film thickness was thinner, but the stability of the measured potential became worse. And it turned out that about 0.25-2.5 C / cm < ² > is preferable.

Film thickness 1 (0.25 C / cm ² , energization time 1
Minute 40 seconds) Film thickness 2 (1.0 C / cm ² , energization time 6 minutes 40 seconds) Film thickness 3 (2.5 C / cm ² , energization time 16 minutes 40 seconds) Film thickness 4 (105 C / cm ² , energization In this way, anions (PVS ⁻ and Cl ⁻ ) in the monomer solution are taken in when the pyrrole becomes polypyrrole. Then, due to the presence of this anion, the bipolaron exists in a stable state, so that the electropolymerized film has conductivity. The physical properties of the electrolytically polymerized film differ depending on the type of anion.

By using polypyrrole, the following advantages can be obtained. 1. It is possible to easily form a film by electrolytic polymerization. 2. It can be fixed on the electrode as a conductive thin film. 3. The film thickness can be controlled electrochemically. 4. Substitution of the dopant is easy, and the dopant can be selected according to the measurement target. Here, thiophene and its derivatives can be used as the monomer for forming the electropolymerized film, and potassium chloride, sodium paratoluenesulfonate (TsONa), and quaternary alkylammonium nitrate (R) can be used as the supporting electrolyte. ₄ NNO ₃ ) or the like can be used, and as the solvent, acetonitrile, propylene carbonate or the like can be used in addition to water.

[0056]

As described above, according to the method for detecting a chemical substance of the present invention, the chemical substance can be identified from the detection pattern by the single measuring section. Furthermore, renewing the electrolyte solution enables repeated measurement.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a gas phase sensor suitable for the present invention.

FIG. 2 is a diagram showing a configuration of a measuring unit 10.

FIG. 3 is a flowchart showing a measurement operation of the present invention.

FIG. 4 is a diagram showing response patterns of various substances.

FIG. 5 is a diagram showing a fitting result when parameters of various reference substances are substituted into a fitting function.

FIG. 6 is a diagram showing contents of a database storing parameters.

FIG. 7 is a diagram showing an example of classification of reference substances by cluster analysis.

FIG. 8 is a diagram showing an identification example 1 (an example in which a chemical substance A is identified) by cluster analysis.

FIG. 9 is a diagram showing an identification example 2 by cluster analysis (an example in which a chemical substance B is identified).

FIG. 10 is a diagram for explaining updating of a database (updating by adding data).

FIG. 11 is a diagram showing a response pattern when the type of measurement electrode is changed.

FIG. 12 is a diagram showing response amounts of various substances.

FIG. 13 is a diagram showing response amounts of various alcohols.

FIG. 14 is a diagram showing the relationship between the concentration of ethanol and the response amount.

FIG. 15 is a diagram for explaining the production of an electropolymerized film.

[Explanation of symbols]

 10 Measuring Section 20 First Measuring Electrode 21 Electrolyte Solution Holding Surface 22 Second Measuring Electrode 23 Gas Receptor 28 Electrolyte Solution Supplying Section 32 Recorder 34 Control Section

Claims (3)

[Claims] 1. A step of holding an electrolyte solution having a surface in direct contact with a gas phase around an electrode, a step of diffusing a chemical substance in the gas phase into the electrolyte solution, and an electrode existing in the electrolyte solution. And detecting the electrical state of the chemical substance as a temporal change based on the diffusion of the chemical substance and the adsorption to the electrode. The chemical substance in the gas phase is detected based on the detected temporal change. Method of detecting chemical substances. 2. The detection method according to claim 1, wherein the step of holding the electrolyte solution around the electrode holds the electrolyte solution by utilizing its surface tension, and the electrolyte solution is supplied from the electrolyte solution supply source. A method for detecting a chemical substance, characterized in that a new electrolyte solution is retained by being supplied to update the electrolyte solution retained around the electrode, and detection is repeated. 3. A method for identifying a chemical substance contained in a gas phase, comprising: (1) holding an electrolyte solution having a surface in direct contact with the gas phase around an electrode; and (2) as a reference substance. The step of obtaining the predetermined fitting function and parameters from the selected chemical substance, the step of diffusing the chemical substance selected as the reference substance into the electrolyte solution, and the electrical state at the electrodes present in this electrolyte solution Detecting as a change over time based on the diffusion of the chemical substance and adsorption to the electrode, forming a pattern of change over time of the electrical state, and setting a fitting function based on this pattern,
A step of obtaining a parameter of each reference substance with respect to this fitting function, a step including: (3) a step of obtaining a predetermined parameter from the chemical substance to be measured, the step of diffusing the chemical substance to be measured into an electrolyte solution And a step of detecting an electrical state at an electrode present in the electrolyte solution as a change over time due to diffusion of the chemical substance and adsorption to the electrode, and creating a parameter of a substance to be measured with respect to the fitting function, And (4) calculating distances between various parameters of the reference substance and parameters of the measurement target substance, and determining that the reference substance having the smallest distance is the most similar to the measurement target substance, A method for identifying a chemical substance, which comprises: