JPH11304761A - Monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect dioxin or the like without using a high-resolution magnetic field type mass spectrograph by ionizing dioxin or the like that is an organic chlorine compound using negative corona discharge and observing the change in the amount of current due to the generated negative ion. SOLUTION: A gas sample through a sample heating furnace 3 is introduced to a corona discharge part 7 for ionization. The tip of a gas sample introduction path 8 is located near a wire electrode 11 for corona discharge and the diameter of the tip is small with a constriction, thus securing introducing the gas sample to a discharge region. Temperature is maintained at 50-300 deg.C by a corona discharge part heating heater power supply 10 and a corona discharge part heating heater 9. A negative high voltage is applied to the wire electrode 11 by a power supply 12 for corona discharge. The high voltage depends on the distance between the wire electrode 11 and a counter electrode 16 but is approximately -1--6 kV. The distance should be approximately several mm. A metal wire heater 5 for heating a gas sample is controlled to 50-400 deg.C by a metal wire heater heating power supply 6, thus preventing particles from being introduced into a corona discharge region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a monitor device,
Specifically, it contains vapors from hazardous materials such as dioxins and explosives represented by nitro compounds, which are a type of organochlorine compounds that are known to be highly toxic, generated from incineration facilities, etc., and contains chlorine and phosphorus elements The present invention relates to a monitor device for detecting a pesticide or the like.

[0002]

2. Description of the Related Art As a conventional technique for analyzing dioxin, a method using a gas chromatograph mass spectrometer using a high-resolution magnetic field type mass spectrometer is known. In this method, a dioxin mixture concentrated through a complicated pretreatment process is introduced into a gas chromatograph, separated, and then irradiated with an electron beam to convert dioxin into positive ions, which are then subjected to high-resolution magnetic field mass spectrometry. It is a method of detecting by a meter. In this method, dioxin can be qualitatively analyzed based on the mass number of the detected ion, and the number of bound chlorine and which skeleton of dibenzoparadioxin or dibenzofuran can be known. In addition, there is a feature that dioxin can be quantitatively analyzed from the intensity of the detected ions.

[0003]

However, in the above-mentioned conventional dioxin analysis method using a high-resolution magnetic field type mass spectrometer, since the apparatus is large and a high vacuum is required, it is necessary to use the on-line or on-site method. There was a problem that it was difficult to analyze.

An object of the present invention is to solve the above-mentioned problems in the conventional dioxin analysis, and to facilitate online and on-site analysis without using a large-sized and high-vacuum-requiring apparatus such as a high-resolution magnetic field mass spectrometer. It is to provide a monitor device such as dioxin which can be used for a computer.

[0005]

In order to solve the above-mentioned problems, a monitor device according to the present invention comprises a means for introducing a sample to be measured through an inlet, and a negative corona discharge of the introduced gas sample. A corona discharge unit and means for measuring a current amount of ions generated by the negative corona discharge are provided, and a desired substance in the gas sample is monitored from a change in the current amount.

[0006] That is, dioxin, which is a kind of organochlorine compound, has a property that it is easily converted to negative ions by negative corona discharge. On the other hand, when a negative gas is caused to flow by flowing a standard gas such as a nitrogen gas, the amount of current of ions generated at that time changes when there is a substance that easily becomes a negative ion. Therefore, the presence or absence of dioxin can be known by performing a negative corona discharge using nitrogen or the like as a standard gas and measuring the amount of generated ions.

As an actual monitor device, for example, FIG.
As shown in the figure, an introduction pump 2 for introducing a gas sample to be measured through an introduction port 1, a corona discharge section 7 for performing a negative corona discharge, electrodes necessary for measuring a corona discharge current, and the like. A high-resolution magnetic field type mass spectrometer that requires a large vacuum and a high vacuum is not used, and is much simpler than the above-mentioned conventional technology.

The monitoring device of the present invention can monitor dioxins, nitro compounds and pesticides as the above-mentioned desired substances.

In the monitor device of the present invention, a sample heating furnace for heating the introduced gas sample to a desired temperature can be arranged between the introduction pump and the corona discharge section. It is extremely useful in practice to raise the introduced gas sample to a predetermined temperature prior to corona discharge, and extremely favorable results are obtained as described below.

Further, when a heater for heating the corona discharge section is provided and a corona discharge is performed to raise the introduced gas sample to a predetermined temperature, the following extremely favorable results can be obtained. The negative corona discharge can be performed by applying a predetermined discharge voltage between a wire electrode provided in the corona discharge portion and a counter electrode, and using a needle electrode instead of the wire electrode. A negative corona discharge may be performed by applying a predetermined discharge voltage between the electrode and the counter electrode.

In order to cope with the case where the number of ions to be measured is not one but a plurality of types, a means for separating a plurality of types of ions generated by the negative corona discharge from each other can be further provided.

As means for separating a plurality of types of ions from each other, a shutter electrode and a counter electrode provided at a position downstream of the corona discharge section can be used.
Further, a deflection electrode and a detection electrode may be provided at a position downstream of the corona discharge section, and these may be used.

[0013] The change in the current value is a decrease in the current value caused by the introduction of the sample. Detection of an object to be monitored such as dioxin or trichlorobenzene is performed based on the decrease in the ion current value.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, when a sample to be measured is a gas, a gas sample introduction pump may be used as a means for introducing the gas. When the sample is a liquid, the solution sample is atomized by the atomizer, and a high-speed jet is generated at that time, so that it is not necessary to use a gas sample introduction pump.

To heat the introduced gas sample, a coiled metal wire heater is disposed in the gas sample passage,
It is practically convenient to heat the sample by bringing it into contact with a gas sample.

In order to perform negative corona discharge, a wire electrode or a needle electrode is arranged in a gas passage, and a counter electrode is arranged at a position corresponding to the wire electrode or the needle electrode on the wall of the passage. A predetermined corona discharge voltage may be applied between the electrodes. The ionic current generated by the negative corona discharge is easily measured by a microammeter connected to the counter electrode.

[0017]

Embodiment 1 A first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram schematically illustrating a monitor device according to the present embodiment. The gas sample to be measured is introduced from the gas sample introduction port 1 by the gas sample introduction pump 2.
In this embodiment, a gas introduction pump having a mechanical mechanism such as a diaphragm pump is used as the gas sample introduction pump 2, and the gas sample introduction flow rate is about several liters to several tens of liters per minute.

In order to prevent the gas sample from being adsorbed on the inner wall of the monitor device, in this embodiment, as shown in FIG.
The gas sample introduced by the gas sample introduction pump 2 was first introduced into the gas sample heating furnace 3 to raise the temperature of the gas sample. In this gas sample heating furnace 3, an insulating pipe 4 made of a material that can withstand high temperatures such as quartz is provided in a metal block, and a metal wire heater 5 for heating a gas sample provided therein is electrically heated. Then, the gas sample passing through this region was heated to a high temperature. As the metal wire heater 5 for heating a gas sample, a metal wire such as a nichrome wire wound in multiple layers was used. The diameter of the insulating pipe depends on the amount of gas flowing in, but is about 5 mm when about 2 liters of gas is introduced per minute. The length of the insulating pipe was about 10 cm. The heating temperature of the gas sample varies depending on the type of the sample to be measured.
~ 400 ° C.

When the introduced gas sample is directly introduced into the corona discharge region, particles (including moisture) are directly introduced into the corona discharge region, and corona discharge becomes unstable, which is not preferable. However, in the present embodiment, as shown in FIG. 1, the metal wire heater 5 for heating the gas sample was provided in front of the corona discharge unit 7, so that even if the above particles were introduced, they were heated to a high temperature. Since the particles collide with the gas sample heating metal wire heater 5 and are vaporized in this region, there is no possibility that the particles are introduced into the corona discharge region. The temperature of the gas sample heating metal wire heater 15 is controlled by a metal wire heater heating power supply 16.
And the temperature in this region was kept at about 50 to 400 ° C.

The gas sample that has passed through the sample heating furnace 13 is introduced into the corona discharge section 7 and ionized. In order to efficiently send the gas sample to the corona discharge region of the corona discharge wire electrode 11, the position of the tip of the gas sample introduction path 8 was set near the corona discharge wire electrode 11. As shown in FIG. 1, in this embodiment, a gas sample introduction path 8 having a small diameter at the tip and having a throttle is used. For example, when the inside diameter of the gas sample introduction path 8 in the middle is about 5 mm, the inside diameter of the tip is made about 1 mm, and the introduced gas sample can be surely and efficiently supplied to the corona discharge wire electrode 1.
One corona discharge region was introduced. In this case, the length of the gas sample introduction path 8 was set to about 5 cm.

As the gas sample introduction path 8, a material made of an insulating material such as Teflon, Macor glass, ceramic, or the like was used so as not to weaken the electric field at the tip of the corona discharge wire electrode 11. It is also effective to heat this region. In this embodiment, the corona discharge unit heater power supply 10 and the corona discharge unit heater 9 are used to heat the region.
It was kept at 300 ° C.

The corona discharge wire electrode 11 provided in the corona discharge section 7 can be applied with a high negative voltage by a corona discharge power supply 12. This high voltage
Although it depends on the distance between the corona discharge wire electrode 11 and the counter electrode 16, about -1 to -6 kV was appropriate. The distance between the corona discharge wire electrode 11 and the counter electrode 16 is several meters.
m.

Using the monitoring device of this embodiment, dioxin at the ppm level could be reliably detected from ppt contained in the air.

<Embodiment 2> In this embodiment, as shown in FIG. 2, a corona discharge needle electrode 14 is used instead of the corona discharge wire electrode 11 used in the first embodiment. In this embodiment, as shown in FIG. 2, the corona discharge needle electrode 14 is arranged at a position oblique to the flow of the gas sample. In the present embodiment, only the tip of the corona discharge needle electrode 14 is exposed, and the root portion is coated with Teflon to improve the uniformity of the electric field between the tip of the corona discharge needle electrode 14 and the counter electrode 16.

As in the case of the first embodiment, the ppm level of dioxin could be reliably detected from ppt contained in the air by using the monitor device of the present embodiment.

<Embodiment 3> This embodiment is an example in which the gas sample introduction pump 2 is arranged at a downstream position of the corona discharge section 7 as shown in FIG. Even with such an arrangement, the gas sample could be introduced from the gas sample introduction port 1 without any trouble. Moreover, since the gaseous sample is introduced into the corona discharge unit 7 without passing through the inside of the gas sample introduction pump 2, there is no possibility that the gaseous sample will be adsorbed inside the gas sample introduction pump 2.

Even with the use of the monitor of this embodiment, as in the case of the first and second embodiments, the ppm level of dioxin could be reliably detected from the ppt contained in the air.

<Embodiment 4> This embodiment is an example in which the lid electrode 15 is provided after the corona discharge section 7 as shown in FIG. According to this embodiment, the corona discharge unit 7 and the lid electrode 15
The gaseous sample is discharged out of the system through the gap between
Since the pressure in the corona discharge region increases and the molecular density in the corona discharge region increases, the ionization efficiency increases. In addition, there is a feature that it becomes difficult for extra gas to flow into the corona discharge portion from the outside.

Using the monitoring device of this embodiment, dioxin at the ppm level could be reliably detected from ppt contained in the air.

In each of the first to fourth embodiments shown in FIGS. 1 to 4, the ions of the negative corona discharge generated by the corona discharge wire electrode 11 and the corona discharge needle electrode 14 are used. Some are counter electrodes 16
And is detected by the minute ammeter 13.

<Embodiment 5> Using the apparatus shown in FIG.
FIG. 5 shows the results obtained by measuring the time change of the negative corona discharge current at a flow rate of the dry air of 5 liters per minute. As is apparent from FIG. 5, a sharp rise in the current value occurs in the first minute or so, indicating the start of the negative corona discharge. A needle electrode was used for corona discharge, and the applied voltage was -2.
5 kV, the temperature of the gas sample heating furnace 3 was 150 ° C.

However, when 1, 2, and 3 trichlorobenzene are introduced into the dry air at the start of the sample introduction shown in FIG. 5 (at a position of about 6 minutes), the current value of the corona discharge rapidly decreases, When the introduction of 1, 2, and 3 trichlorobenzene was stopped at the time when the introduction of the sample was stopped, the current value returned to the value before the introduction.

That is, since 1,2,3 trichlorobenzene is a substance that easily becomes negative ions by negative corona discharge, the current value detected by the counter electrode 16 is 1,
It was reduced by a few trichlorobenzenes.
Therefore, by measuring the amount of change in the corona discharge current in the standard gas when a certain gaseous sample is introduced, the amount of the gaseous sample can be estimated.

The reason why the negative corona discharge current decreases when 1, 2, 3 trichlorobenzene is introduced is as follows.
It is considered as follows. That is, from small ions such as oxygen ions observed using dry air, 1, 2,
A large ion such as 3 trichlorobenzene has a lower drift speed in the atmosphere (the speed at which the ion travels in an electric field under a certain atmospheric pressure). Therefore, the distance between the tip of the corona discharge needle electrode 14 and the counter electrode 16 It takes time to travel through the electric field formed by In the meantime, ions generated in the vicinity of the corona discharge needle electrode due to the gas flow perpendicular to the electric field formed by the gas sample introduction pump 2 become difficult to reach the counter electrode 16 when the drift velocity is low, and the ions are observed accordingly. The amount of ions decreases.

In FIG. 5, the rise in the corona discharge current observed at a position of about 8 minutes was obtained when methanol vapor was introduced. For small molecules such as methanol, the drift speed is high, and in the case of a large amount, it may be observed in the form of an increase in current.

The same results were obtained with the devices shown in Examples 2 to 4.

<Embodiment 6> 1, 2, and 3 trichlorobenzene vapors were introduced into the monitoring apparatus shown in the above-described embodiment 1,
The result of measuring the temporal change of the corona discharge current value will be described with reference to FIG. The decrease of the corona discharge current obtained by introducing 1,2,3 trichlorobenzene vapor is shown in FIG.
As shown in FIG. 6B, based on the corona discharge current in the situation where the standard gas is flowing, as shown in FIG.
It can also be considered that a peak due to 2,3 trichlorobenzene vapor appears. That is, assuming that the current obtained by corona discharge is I, this corresponds to displaying the current as AI (A is a certain constant). Displaying in this manner makes it easier to see the detection result. FIG. 7 shows an example. This is an example in which a sample bottle containing 1, 2, and 3 trichlorobenzene was placed in a heating furnace, and generated vapor was detected. As the temperature of the heating furnace is increased, the vapor from the sample increases, and it can be considered that the observed peak intensity increases accordingly. The results also show the importance of heating the sample to be measured.It is also important to use means such as heating the solid sample using a lamp when sampling vapor from the solid sample. It is. Although the results of chlorobenzene have been described in the examples so far, it is needless to say that the present invention is also effective for detecting an organic chlorine compound such as dioxin having chlorine and a nitro compound having a nitro group. It is also effective for detecting pesticides containing phosphorus and chlorine.

<Embodiment 7> This embodiment is an example in which a separating means is provided after the corona discharge section 7 so that when the gas sample to be introduced is a mixture, it can be detected separately from each other. This will be described with reference to FIG.

In the present embodiment, an ion mover is provided which utilizes the fact that the drift speed in the atmosphere varies depending on the ion species. In this part, the corona discharge needle electrode 14
The ions generated by the meshing focusing electrode 17
After that, the mesh-shaped shutter electrode 18 was opened for a certain time (about several microseconds to several tens of microseconds), and the mesh-shaped shutter electrode 18 and the mesh-shaped counter electrode 19 were simultaneously drifted. In order to drift ions, a voltage of the order of several kV is applied between the mesh-shaped shutter electrode 18 and the mesh-shaped counter electrode 19, and the magnitude of the voltage applied to the mesh-shaped counter electrode is The voltage is set lower than the voltage applied to the shutter electrode 18. The voltages applied to these electrodes 18 and 19 were controlled by an ion mobility meter control circuit 21. At this time, a standard gas such as dry nitrogen was flown in a direction opposite to the traveling direction of the ions.

The ions that have reached the collector electrode 20 are amplified and sent to the data processor 22. By using such an ion mobility meter, as is apparent from the two peaks shown in FIG. 9, for example, when the number of components is 2, the two components are separated from each other and detected. You. Since the time required for detection is the same under certain conditions, the type of substance can be estimated from this time. The separation time is about several milliseconds to several tens of milliseconds, and the detection time is as short as about several seconds including data processing, so that it can be used as a monitor.

<Embodiment 8> An embodiment using another ion separating means will be described with reference to FIG. A part of the ions generated by the corona discharge needle electrode 14 are detected by the counter electrode 16 and directed to the deflection electrode 23. When a negative voltage is applied to the deflection electrode 23 when negative ions are introduced, a force is generated that moves in the direction of the detection electrode 25 against the flow of gas. At this time, if the mobility of the introduced ions is high (small ions), the ions reach the detection electrode 25 and are observed even if the voltage applied to the deflection electrode 23 is low. Conversely, when the mobility of ions is low (large ions), the voltage applied to the deflection electrode must be increased.

Therefore, when the voltage applied to the deflection electrode is scanned, a current-voltage curve as shown in FIG. 9 is obtained. In this case, when the flow rate of the gas sample introduction pump 2 is about several liters per minute and the distance between the deflection electrode 23 and the detection electrode 26 is about several millimeters, the voltage applied to the deflection electrode is about several hundred volts to several kilovolts.

The data processor 22 may display the final display in a more simplified manner, instead of the chromatogram shown in FIG. For example, in the case of a dangerous substance detection device, it may be only necessary to display whether or not a nitro compound in question has been detected.

When there is a predetermined noise level with respect to a certain ion to be detected, it is determined that the ion has been detected when a signal at or above this noise level is detected.
In this case, in order to distinguish the signal from a mere spike noise, an algorithm is used which regards a signal having a noise level or higher as a signal when the signal is observed for a certain period of time or longer. By adding such an algorithm, malfunctions can be reduced. At this time, as a final display, an indicator of a substance corresponding to a certain ion to be detected is displayed on a display device, and for example, if A is detected by the above algorithm, A is blinked. Causes A to be detected. At this time, an indicator of an amount for notifying the concentration (for simplicity, information indicating whether the amount is large or small) or an alarm may be provided at the same time.

In each of the above embodiments, the case where a gas sample was used was shown, but not only a gas sample but also a solution sample (dioxin may be dissolved in an organic solvent. In this case, For example, if a solution sample is atomized using a gas atomizer or a heat atomizer, and the solution sample is introduced into a gas sample heating furnace 3 as shown in FIG. 2, analysis is performed in the same manner as in the case of a gas sample. At this time, there is no need to use a gas sample introduction pump, since a high-speed jet is generated from the atomizer.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram showing a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a fifth embodiment of the present invention.

FIG. 6 is a diagram showing a sixth embodiment of the present invention.

FIG. 7 is a diagram showing a sixth embodiment of the present invention.

FIG. 8 is a diagram showing a seventh embodiment of the present invention.

FIG. 9 is a diagram showing a seventh embodiment of the present invention.

FIG. 10 is a diagram showing an eighth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Gas sample introduction port, 2 ... Gas sample introduction pump, 3 ... Gas sample heating furnace, 4 ... Insulation pipe, 5 ... Metal wire heater for gas sample heating, 6 ... Metal wire heater heating power supply, 7 ... Corona discharge part, 8: gas sample introduction path, 9: corona discharge section heater, 10: corona discharge section heater power supply, 11: corona discharge wire electrode, 12: corona discharge power supply, 13
a, b: microammeter, 14: needle electrode for corona discharge, 15
... Lid electrode, 16 counter electrode, 17 mesh focusing electrode, 18 mesh shutter electrode, 19 mesh counter electrode, 20 collector electrode, 21 ion mobility meter control circuit, 22 data processing device, 23 ... deflecting electrode,
24: power supply for deflection electrode; 25: detection electrode.

Claims (10)

[Claims] 1. A means for introducing a sample to be measured through an inlet, a corona discharge section for performing a negative corona discharge on the introduced gas sample, and a current amount of ions generated by the negative corona discharge. A monitor for measuring a desired substance in the gas sample from the change in the amount of current. 2. The monitor device according to claim 1, wherein said desired substance is selected from the group consisting of dioxins, nitro compounds and pesticides. 3. A sample heating furnace for heating the introduced gas sample to a desired temperature is disposed between the introduction pump and the corona discharge section. A monitoring device according to claim 1. 4. The monitor device according to claim 1, further comprising a heater for heating the corona discharge unit. 5. The method according to claim 1, wherein said negative corona discharge is performed by applying a predetermined discharge voltage between a wire electrode and a counter electrode provided in said corona discharge portion. The monitor device according to any one of the above. 6. The method according to claim 1, wherein said negative corona discharge is performed by applying a predetermined discharge voltage between a needle electrode and a counter electrode provided in said corona discharge portion. The monitor device according to any one of the above. 7. The monitor device according to claim 1, further comprising means for separating a plurality of types of ions generated by the negative corona discharge from each other. 8. The monitor device according to claim 7, wherein the means for separating the plurality of types of ions from each other is a shutter electrode and a counter electrode provided at a position downstream of the corona discharge section. 9. The monitor device according to claim 7, wherein the means for separating the plurality of types of ions from each other is a deflection electrode and a detection electrode provided at a position downstream of the corona discharge section. 10. The monitor device according to claim 1, wherein the change in the current value is a decrease in the current value caused by the introduction of the sample.