JP3218032B1 - Ethylene gas sensor, ethylene gas determination method and apparatus - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide an ethylene gas sensor for detecting ethylene in a gas, a method and an apparatus for measuring an ethylene gas concentration using the ethylene gas sensor. An ethylene gas sensor characterized by holding a pressure. A method and apparatus for measuring the concentration of ethylene gas in a gas using such an ethylene gas sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ethylene gas sensor for detecting ethylene in a gas, and a method or an apparatus for measuring the concentration of ethylene gas in a gas.

[0002]

2. Description of the Related Art Conventionally, gas sensors have a large market for harmful gases such as flammable gas, oxygen, humidity, CO, etc. However, new needs are generated one after another, and active research is still ongoing. Continued. One of the recent major needs is the detection of odors, which has specific applications such as risk management and food management, as well as being part of a new theme in information science, sensitivity sensing.

[0003] Materials conventionally used for odor sensors include metal oxide semiconductors and organic materials. Smell sensors using metal oxide semiconductors mainly use a sintered body of oxide particles, and the odor molecules adsorb or react on the surface of the semiconductor particles, causing the electrical resistance of the semiconductor to change. It is extracted as a signal. On the other hand, when using an organic material, the odor component is adsorbed on the organic material,
The mass or absorbance changes, and the change is physically measured.

[0004] Smell components detected include trimethylamine (TMA) and dimethylamine (DMA) related to the freshness of fish and shellfish, and ethyl acetate and acetoin related to beef freshness, such as methylpyrazine and acetone contained in consommé soup. Such as H ₂ S and N
A fairly extensive study has been made on H ₃ , fruit oil, methyl mercaptan, aliphatic amines and the like.

A method using a quartz oscillator as a sensor using an organic material (Quartz Crystal Microbalance method (QC
M method)) is known (G. Sauerbrey "Verwendung von
Schwingquartzen zur Wagung dunner Schichten und z
ur Mikrowagung ", Zeitshriftfur Physik, Vol.155, pp.20
6-222, 1959). This method is a method applied as a high-sensitivity gas sensor element, since the quartz oscillator can detect a minute mass change on the oscillator electrode due to gas adsorption or the like as a resonance frequency change by a mass load effect. Further, in this QCM method, sensors having various characteristics can be easily realized by changing the sensitive film applied on the electrodes. A polymer or lipid is mainly used for the membrane material. When the odor is identified using this sensor, a method of pattern recognition of outputs from a plurality of sensors coated with different sensitive films by multivariate analysis or a neural network is used.

On the other hand, it is known that plants such as fruits, vegetables and flowers generate ethylene gas by fermentation and the fermentation proceeds further by the released ethylene gas. Therefore, to control the fermentation of fruits, vegetables, flowers, etc., and to maintain the freshness, it is important to detect and measure the concentration of ethylene gas in the gas in storages and transport shelves. In reality, no suitable simple and accurate ethylene gas sensor has been developed.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ethylene gas sensor for detecting ethylene gas in a gas, and a method and an apparatus for measuring the concentration of ethylene gas using the ethylene gas sensor.

[0008]

Means for Solving the Problems The present invention is dedicated to solving the above-mentioned problems, and an ethylene monooxygenase which biochemically adsorbs ethylene gas may be used as an organic material used for an ethylene gas sensor. It was made as a result of finding. That is, the present inventors were conducting research on the use of activated carbon obtained by steaming bamboo to adsorb ethylene gas, and found that raw bamboo itself adsorbs ethylene gas, and the raw bamboo itself is contained in raw bamboo. The present inventors came to the conclusion that the use of ethylene monooxygenase, which is an ethylene oxidase, would make it possible to adsorb ethylene gas more efficiently. As a result, the present invention was achieved.

That is, the present invention relates to an ethylene gas sensor characterized in that a quartz oscillator holds ethylene monooxygenase. It is preferable that the ethylene gas sensor of the present invention further include a coenzyme (NADPH) in ethylene monooxygenase.
The present invention also relates to an ethylene gas sensor obtained by applying a bamboo vinegar solution containing ethylene monooxygenase to a quartz oscillator. Further, the present invention relates to an ethylene gas sensor obtained by applying a bamboo vinegar solution to a quartz oscillator via a gel-forming substance having an amino group. Furthermore, the present invention also relates to a method and an apparatus for measuring the concentration of ethylene gas in gas using such an ethylene gas sensor.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The mechanism of ethylene metabolism in plant tissues is shown below. In the following “Mechanism of CH ₂ CH ₂ metabolism in plant tissue”, [O] represents ethylene oxidase (ethylene monooxygenase). As shown below,
There are two active sites in the plant to metabolize ethylene. At the active site I, ethylene is oxidized and converted to ethylene oxide, and further oxidized to carbon dioxide via ethylene glycol. At the active site II, after conversion to ethylene glycol, it is further bound to glucose to form an ethylene glycol-glucose conjugate.

[0011]

The mechanism of metabolism of ethylene is described in more detail below. Ethylene is converted to ethylene oxide by ethylene oxidase (ethylene monooxygenase) and binds to a receptor to cause a biochemical reaction.
At that time, NADPH is required as a coenzyme. The coenzyme performs a chemical reaction using the energy released when it is oxidized and decomposed. Ethylene oxide becomes ethylene glycol at another site and is metabolized to carbon dioxide. This carbon dioxide has the effect of increasing ethylene monooxygenase activity. Glyoxylation of ethylene glycol is a pathway for detoxification of ethylene ("Ethylene" by Takayuki Shimokawa, University of Tokyo Press, 76
Pp. 80 (1988)).

[0013]

[0014] The present inventors initially obtained an ethylene gas adsorbent for maintaining the freshness of plants such as fruits, vegetables, flowers, etc. by cutting raw bamboo as it is and cutting raw bamboo into slices. A test using the activated carbon thus obtained was conducted.
For this purpose, raw bamboo and 300 ° C, 1000 ° C, and 200 ° C were placed in a closed container filled with 50 ppm ethylene gas.
Activated carbon (bamboo charcoal) obtained by steaming at 0 ° C
Was put in each 25 g, and air was circulated by a fan to perform an ethylene gas removal test. FIG. 1 shows the result of the ethylene gas removal test. According to the result of FIG. 1, it was confirmed that raw bamboo removed ethylene best. From this, it was predicted that the removal of ethylene gas might be related to bamboo plant metabolism instead of physical adsorption by activated carbon.

However, raw bamboo cannot be used as it is in an ethylene gas sensor, and as a result of researching a liquid material that can be made into a thin film and having an ethylene gas removing effect equivalent to that of raw bamboo, furthermore, raw bamboo was carbonized. Or, we focused on the bamboo vinegar solution obtained by extraction. In the present invention,
Bamboo vinegar refers to a liquid obtained by dry distillation or extraction from raw bamboo. More specifically, raw bamboo is powdered, and
A liquid obtained by dry distillation at a temperature of 00 ° C. by applying a pressure of 3 to 5 atm, or a liquid obtained by powdering raw bamboo and extracting it with alcohol, water, or an aqueous enzyme solution such as cellulase. .

Next, the present inventors conducted an experiment for removing ethylene gas using bamboo vinegar obtained from raw bamboo. 100 ml of bamboo vinegar obtained by carbonizing raw bamboo is diluted with 300 ml of ultrapure water, and the biodegradable resin foam granules are immersed for 24 hours.
Thereafter, the filter was naturally dried for 24 hours to produce a filter. The prepared filter was placed in a closed container filled with about 50 ppm of ethylene, and air was circulated by a fan. The results obtained by measuring the ethylene gas removal rate after 3 hours are shown in Table 1.

[0017]

[Table 1] From this result, it was found that when the bamboo vinegar solution was immersed in the foam, the removal rate was significantly increased as compared with the foam alone.

As described above, ethylene is contained in a plant body.
It is converted to ethylene oxide by ethylene oxidase (ethylene monooxygenase), further converted to ethylene glycol, and metabolized to carbon dioxide. From this, and from the test results that the raw bamboo or bamboo vinegar liquid of the present inventors have an ethylene gas adsorption effect,
The present inventors have presumed that the decomposition and metabolism of ethylene by enzymes contained in raw bamboo or bamboo vinegar may contribute to the ability of raw bamboo or bamboo vinegar to remove ethylene gas.

On the other hand, the present inventors have analyzed raw bamboo or bamboo vinegar, and as a result, have confirmed that the raw bamboo or bamboo vinegar contains ethylene monooxygenase which is an ethylene oxidase.

From the above test and analysis, the present inventors have found that
Not only raw bamboo or bamboo vinegar but also a material containing ethylene monooxygenase was effective as an ethylene gas adsorbent, and it was found that the material could be held in a quartz oscillator and applied to an ethylene gas sensor.

In order to hold the bamboo vinegar solution on the crystal oscillator, the bamboo vinegar solution may be cast or coated as it is. However, it is better to hold the bamboo vinegar solution on the substrate through a gel-forming substance having an amino group. This is preferable because the adsorption rate of the compound increases. Since the amino group can react with the carboxyl group of the enzyme protein in the bamboo vinegar to immobilize the enzyme, when the bamboo vinegar is held on the base material through the gel-forming substance having the amino group, ethylene gas It is assumed that the adsorption rate is increased. Preferred substances for the gel-forming substance having an amino group are polyallylamine, polyethyleneimine and chitosan. Chitosan is more preferred because it has two amino groups in the molecule and is harmless.
When using chitosan, it is preferable to add a weak acid which is harmless to the human body such as acetic acid and citric acid to chitosan and use it as a transparent solution.

The bamboo vinegar and the gel-forming substance may be mixed and held on a quartz oscillator, or the gel-forming substance may be held on a quartz oscillator and the bamboo vinegar may be held thereon. May be laminated. For example, the sensor of the present invention can be manufactured by coating or casting a quartz oscillator using a solution obtained by mixing a bamboo vinegar solution with an aqueous solution of polyallylamine or an aqueous solution obtained by adding citric acid to chitosan. Further, the sensor of the present invention is coated with a solution obtained by adding citric acid to polyallylamine or chitosan on a quartz oscillator and dried,
It can also be produced by coating a bamboo vinegar solution thereon and drying.

[0023]

EXAMPLES The test examples and examples of the present invention are described below, but the present invention is not limited thereto.

Example 1 (Preparation of Sensor) A bamboo vinegar solution was obtained by placing Moso bamboo powder in a basket and carbonizing at 300 ° C. and 5 atm for 4 hours. 0.2 μl of this bamboo vinegar solution was cast on an electrode of a quartz oscillator, and was naturally dried for 24 hours to obtain a sensor.

(Ethylene Gas Adsorption Test) The samples thus obtained were subjected to ethylene gas concentrations of 150, 300 and 8
Insert into a sealed container maintained at a constant concentration of
After 00 seconds, it was released into the atmosphere. This measurement was performed three times.

(Test Method of Adsorption Amount) The adsorption amount of ethylene gas was measured using a quartz crystal microbalance (Quartz Crystal M).
icrobalance) method (QCM method). QC
The M method utilizes the fact that the natural frequency of a crystal resonator changes due to a change in mass attached to an electrode.
When a trace substance adheres to the crystal resonator electrode by gas adsorption or the like, the minute mass change can be detected as a resonance frequency change by a mass load effect.

FIG. 2 shows a schematic diagram of an apparatus for the QCM method. 1 is a quartz oscillator casting ethylene monooxygenase, 2 is an oscillation circuit, 3 is a resonance frequency detector, and 4 is a computer. The frequency change appearing on the quartz oscillator 1 due to the ethylene gas supplied from the ethylene gas supply source 5 to the closed container 6 being adsorbed on the quartz oscillator 1 is detected.

(Results) The results are shown in FIG. In FIG. 3, (1) shows an ethylene gas concentration of 150 ppm,
(2) shows a case of 300 ppm, and (3) shows a case of 800 ppm. From these results, the ethylene gas concentration was 15
In any of the cases of 0, 300, and 800 ppm, when the quartz oscillator in which the bamboo vinegar solution is cast is put in a closed container, adsorption of ethylene gas starts, and the exposed ethylene gas is desorbed by exposure to the atmosphere. You can see that. From this, it was found that the crystal oscillator cast with the bamboo vinegar solution was used as an ethylene gas sensor.
According to (1) to (3) of FIG. 3, the saturated adsorption amounts are almost equal in each case, and the difference is small.

[0028]

Example 2 Example 2 shows an ethylene gas sensor using a composite film using a gel-forming substance having an amino group.
Before casting the bamboo vinegar solution on the quartz oscillator, polyallylamine hydrochloride (PAH) was used as a binder, and the bamboo vinegar solution was cast thereon to produce a composite film of the PAH and the bamboo vinegar solution. First, a quartz oscillator was subjected to hydrophilic treatment with KOH, and 0.2 μl of a PAH solution was cast and naturally dried for 24 hours to form a thin film. Then, 0.2μl bamboo vinegar
Was cast and air-dried for 24 hours to produce a composite membrane. The prepared quartz-crystal vibrator having the composite film, the PAH single film, and the bamboo vinegar solution single film was put in and out of a closed container having an ethylene concentration of 200 ppm, and the adsorption and desorption responses were observed. FIG. 4 shows the results. In FIG. 4, the vertical axis represents the ethylene adsorption amount (ng / ng) with respect to the adsorption film amount. From these results, it was found that when a composite membrane was formed with PAH interposed, the adsorption ability was increased as compared with a single membrane of bamboo vinegar solution, and the function as an ethylene gas sensor was further improved.

[0029]

Embodiment 3 Next, an application as an ethylene gas concentration measuring method and apparatus will be described. The sensor obtained in Example 2 using the composite membrane of PAH and bamboo vinegar was used for the concentration of 8, 25, 30,
Response was observed in a closed container filled with 40, 200, and 600 ppm of ethylene gas. The same ethylene gas measuring apparatus as that shown in FIG. The ethylene gas concentration in the closed vessel was measured using a commercially available detector tube (manufactured by Gastec). The results of the obtained adsorption isotherm are shown in FIG. The horizontal axis in FIG. 5 is the ethylene gas concentration in the closed container, and the vertical axis is the ethylene gas adsorption amount measured by the QCM method. As can be seen from FIG. 5, it shows a Langmuir-type adsorption isotherm, has linearity at an ethylene gas concentration of 40 ppm or less, and can be used as a simple ethylene gas concentration measuring device with the same accuracy as a commercially available detector tube. Also 40
When it exceeds ppm, it is non-linear, but it can be similarly used for concentration measurement by conversion using a calibration curve.

[0030]

Embodiment 4 It is shown that the ethylene gas sensor of the present invention is specific to ethylene gas. QCM similar to Example 1
Using a device, formaldehyde 3
ppm, trichloromethane 80ppm, ethylene 40p
pm. The results are shown in FIG. The horizontal axis is time,
The vertical axis is the ethylene adsorption amount. As can be seen from FIG. 6, the sensor of the present invention adsorbed ethylene gas, but did not adsorb other formaldehyde and trichloromethane. From this result, it can be seen that the sensor in which the bamboo vinegar solution was formed into a film and adhered to the quartz oscillator had selectivity for ethylene gas.

[0031]

As described in detail above, the quartz oscillator holding ethylene monooxygenase or bamboo vinegar can efficiently and selectively adsorb ethylene gas, so that the ethylene gas sensor or ethylene gas concentration Applicable to measurement methods and devices.

[Brief description of the drawings]

FIG. 1 is a reference diagram showing an ethylene gas adsorption rate by bamboo or bamboo charcoal.

FIG. 2 is a schematic view of an ethylene gas concentration measuring device of the present invention.

FIG. 3 shows the ethylene gas adsorption ability of a sensor holding a bamboo vinegar solution of the present invention.

FIG. 4 shows the ethylene gas adsorption ability of a sensor holding a bamboo vinegar solution with a gel-forming substance interposed.

FIG. 5 shows the amount of ethylene gas adsorbed depending on the ethylene gas concentration using the sensor of the present invention.

FIG. 6 shows a comparison between the amount of ethylene gas adsorbed and the amount of other odor gas adsorbed using the sensor of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-186139 (JP, A) JP-A-4-105061 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 30/00 G01N 5/02 JICST file (JOIS)

Claims (7)

(57) [Claims] 1. An ethylene gas sensor comprising an ethylene monooxygenase held in a quartz oscillator. 2. The ethylene gas sensor according to claim 1, further comprising NADPH as a coenzyme. 3. An ethylene gas sensor in a gas, wherein a bamboo vinegar solution is applied to a quartz oscillator. 4. The ethylene gas sensor according to claim 2, wherein a bamboo vinegar solution is applied to the crystal unit via a gel-forming substance having an amino group. 5. A method for measuring the concentration of ethylene gas in a gas using the ethylene gas sensor according to claim 1. 6. The method for measuring the concentration of ethylene gas according to claim 5, wherein the concentration of ethylene gas is quantified by measuring a change in the natural frequency of the crystal unit. 7. An ethylene gas sensor formed by applying a bamboo vinegar solution to a quartz oscillator, a natural frequency measuring device of the quartz oscillator, a device for measuring a change in the natural frequency, and converting the change value into an ethylene gas concentration. And a device for measuring the concentration of ethylene gas.