JP2001351569A - On-line monitor for measuring gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably ionize a sample in exhaust gas with high efficiency, to transport the ion to a mass spectrometer with a high transmission factor and further to prevent intrusion of corrosive gas in the exhaust gas to improve the durability of the mass spectrometer. SOLUTION: A device for ionizing sample gas under the atmospheric pressure and measuring and analyzing components in the sample gas is provided with means 33, 34 for leading in the sample gas. At least one gas ionizing means 10 is provided on one face side of the means for leading in the sample gas, and an initial stage of a differential exhaust part comprising relatively low vacuum chambers 50, 60, 70 constituted stepwise to inject the ionized sample gas into a mass spectrometric part 80 disposed in a high vacuum region, is disposed on the other face side of the means 10 for leading in the sample gas. A mass spectrometric part 80 of high vacuum is disposed at the final stage part of the differential exhaust part of the low vacuum chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atmospheric pressure ionization mass spectrometer, and more particularly to an on-line gas measurement online for measuring and analyzing dioxins and the like in gas discharged from an incinerator or the like using the same. It relates to a monitoring device.

[0002]

2. Description of the Related Art In recent years, mass spectrometers have been widely used as a method for detecting trace components with high sensitivity, such as in gases and liquids.
It is an analyzer.

[0003] This type of apparatus ionizes a sample to be measured and analyzes the generated ions in a mass spectrometer, and contains a sample component and a solvent component flowing out from a liquid chromatograph (LC) or the like. For mass spectrometry of fluids,
Atmospheric pressure ionization (API) is often used as the ionization method.

In the atmospheric pressure ionization method, since excessive energy is not given to the sample molecules, the decomposition of the sample ions is small and the original structure of the sample ions can be easily observed. Further, since the ionization is performed under a high pressure (atmospheric pressure), the ionization rate is high even for a substance having a low ionization potential, and high sensitivity analysis can be expected. Regarding atmospheric pressure ionization, Analytical Chemistry, 1990, Vol. 62, No. 13, 713A-725.
It is described in detail on page A.

The method of ionizing a sample at atmospheric pressure has been variously improved, and one of them is an atmospheric pressure chemical ionization method using corona discharge.

According to this method, as described in JP-A-51-008996, a sample is introduced into a corona discharge region generated at the tip of a needle electrode by applying a high voltage and ionized. At this time, in addition to the case where the sample is directly ionized by corona discharge (primary ionization),
Since there is ionization (secondary ionization) by the ion molecule reaction, the sample molecules are ionized with high efficiency as a result.

An apparatus utilizing the corona discharge is described in Japanese Patent Application Laid-Open No. 60-241634.
This apparatus is composed of an ion generating section, a sample introducing section, and a mass analyzing section having pores for introducing ions and being evacuated by a vacuum pump. A primary ion generating gas such as nitrogen gas is introduced into the ion generating section, and primary ions are generated by corona discharge or the like. The generated primary ions are ejected into the atmosphere together with the primary ion generating gas. On the other hand, the sample gas is ejected from the sample introduction part. At atmospheric pressure, just before the pores of the mass spectrometer, the primary ions mix with the sample gas and collide with a small amount of the target substance molecules contained in the sample gas to cause an ion-molecule reaction, causing the target substance to react. Of ions. The generated ions are sucked into the high-vacuum mass spectrometer from the pores, and mass-separated and detected by the mass spectrometer.

Further, as an ionization method by corona discharge, there has been proposed a method of ionizing a sample gas without directly introducing it into a corona discharge region as described in JP-A-6-310091. That is, a method is used in which sample molecules that do not pass through the corona discharge region due to the ion molecule reaction are efficiently secondary ionized by using primary ions generated in a separately provided corona discharge region. Thus, direct ionization using corona discharge, such as silane gas, is very effective in the case where the ion source is extremely contaminated by discharge products and cannot be ionized.

Further, there is a method described in US Pat. No. 4,023,398. In this example, a method of flowing a curtain gas between a corona discharge region and pores for taking ions into a vacuum in order to prevent a carrier gas for transporting a sample from being introduced into a mass spectrometer under a vacuum. Is disclosed.
With this contrivance, the evacuation efficiency can be improved when a vacuum evacuation system such as a cryopump is used.

In order to perform mass spectrometry on ions generated under atmospheric pressure, it is necessary to introduce the ions into a mass spectrometer having a high degree of vacuum. However, if ions generated under the atmospheric pressure are immediately introduced into the high vacuum chamber, the high vacuum chamber is easily contaminated, noise is generated, and the frequency of failure of the first exhaust pump increases. For this reason, an intermediate vacuum chamber of a low vacuum chamber is usually provided between the atmospheric pressure and the high vacuum chamber, and the gas is exhausted by an exhaust pump so that the pressure gradually decreases from the atmospheric pressure to the high vacuum. At this time, in order to simplify the evacuation system, as in Japanese Patent Nos. 2828402 and 2913924, a ventilation part is provided separately from the ion passage opening in the partition of the low vacuum chamber and the intermediate vacuum chamber, and the low vacuum chamber and the intermediate Simplified evacuation methods, such as evacuation of the vacuum chamber by a common evacuation pump, have also been studied.

On the other hand, in recent years, when waste is incinerated at a garbage incineration plant, highly toxic dioxin is generated in the exhaust gas,
It causes environmental pollution and is a serious social problem.
Here, dioxin refers to polychlorinated dibenzoparadioxins (PCDDs) having 75 isomers and 13
Polychlorinated dibenzofuran with 5 isomers (PCD
Fs), and may include coplanar polychlorinated biphenyls (Coplanar PCBs) in a broader sense.
Hereinafter, dioxins and a group of compounds related thereto will be abbreviated as dioxins.

Quantitative analysis of dioxins is carried out using extremely complicated chemical treatments and expensive analytical instruments.
Therefore, it takes one week / one sample to obtain the analysis result.

Therefore, it is naturally impossible to perform real-time monitoring under actual operating conditions of the incinerator. Also, JP-A-9
The technique described in Japanese Patent No. 243601 is to measure chlorobenzenes and chlorophenols in exhaust gas in real time and to continuously obtain the concentration of dioxins. The exhaust gas is led to a laser ionization mass spectrometer, and ionization and mass spectrometry are performed to determine the concentration of chlorobenzenes and chlorophenols, and indirectly to obtain the concentration of dioxins.

[0014]

The above-mentioned JP-A-51-0
In the conventional examples described in JP-A-08996 and JP-A-6-310091, when the concentration of the measurement sample is extremely low (for example, when measuring a minor component in air,
In the case of measuring a trace component in a liquid, etc.), the intensity of ions of components present in a larger amount or ions derived from components present in a larger amount (for example, ions generated by an ion molecule reaction) as compared with ions of a measurement sample. Becomes extremely strong.

Therefore, when the sensitivity of the detector is set in accordance with the ions of a small amount of the measurement sample, ions of components present in a large amount or ions derived from components present in a large amount reach the detector, and a large current flows at once. Therefore, there is a problem that the detector is damaged, the amplification factor of the current gradually deteriorates, and ions of the measurement sample cannot be detected.

Further, when a molecule corresponding to a component present in a large amount or a molecule corresponding to an ion derived from a component existing in a large amount is easily ionized by a molecule of a target sample,
There has been a problem that the ion generation efficiency of the target sample is deteriorated, and as a result, the sensitivity is lowered.

Further, in an ion trap type mass spectrometer which performs mass analysis of the stored ions by scanning a high frequency voltage after storing the ions, a mass corresponding to the amplitude of the applied high frequency voltage when the ions are stored. Less than a few ions reach the detector directly after passing through the ion trap mass analyzer. Therefore, when the ions are present in a large amount, the detector is damaged, and there has been a problem that the current amplification factor gradually deteriorates.

Further, in the method described in US Pat. No. 4,023,398, the use of a curtain gas to prevent the carrier gas from being introduced into a vacuum is devised. This was essentially the same as the one described above, and contained the same problems as in the above conventional example.

Therefore, development of an ion source using corona discharge under atmospheric pressure for generating ions of a target sample as efficiently as possible has been an issue.

Furthermore, when a gas having a high acidity or a foreign gas such as an exhaust gas is contained, there is a high possibility that the amplification factor of ionization is reduced by the foreign gas. Further, if the corona discharge electrode becomes dirty, the corona discharge becomes unstable, the primary ionization efficiency changes, and finally, there is a problem that the discharge does not occur.

In order to mass-analyze the ions in the sample with high sensitivity, it is necessary to finally improve the ion transmittance at the opening between the vacuum chambers provided with the pressure gradient.
However, the opening diameter of each vacuum chamber and the distance between each opening for obtaining a high ion transmittance at the opening between the vacuum chambers have not been studied so far. For this reason,
In the case of measuring and analyzing an extremely small amount of a sample such as dioxins and chlorophenols which are precursors of dioxins, detection was impossible due to insufficient sensitivity.

The technique described in JP-A-9-243601 suggests the possibility of real-time concentration measurement of chlorobenzenes. However, the ionization in this mode is multiphoton ionization. In this ionization, monochlorobenzenes can be measured to some extent. However, in this multiphoton ionization, every time the number of chlorines substituted on the benzene nucleus increases by one, it is reduced from 1/7 to 1/10.
Is considered to cause a decrease in sensitivity. Trichlorobenzene is ionized only with about 1/100 the efficiency of monochlorobenzene. That is, it can be said that trichlorobenzene has only about 1/100 sensitivity of monochlorobenzene.

On the other hand, 2,3,7,8-tetrachlorodibenzo-P-, which is known as the most toxic dioxin,
Dioxin (2, 3, 7, 8-TCDD) is a compound in which four hydrogens at positions 2, 3, 7, and 8 of dioxin are substituted with chlorine. All toxic dioxins are dioxins in which four or more chlorine atoms have been substituted. This highly toxic dioxin must be a precursor of chlorophenols and chlorobenzenes.

In the multiphoton ionization system shown in this proposal, a polysubstituted chlorine compound cannot be ionized efficiently. That is, the concentration in the combustion furnace exhaust gas is 1000 ng / Nm ³ (1p
It is very difficult to measure chlorophenols and chlorobenzenes on the order of pb).

As described above, to date, no means or apparatus has been disclosed for sampling exhaust gas online and measuring dioxins or their precursors in real time. Further, even if the prior arts of the above-mentioned parts are integrated, they cannot be easily realized.

For this reason, there is no real-time monitoring method for dioxins, so that the following problems have occurred.

It has not been known how much dioxins are contained in the exhaust gas from incinerators and the like, and how much fluctuations are present.

From the start of combustion in the incinerator until the exhaust gas is discharged from the chimney into the atmosphere, the exhaust gas passes through many spaces at different temperatures and is discharged through many chemical reaction processes in the exhaust gas. It is not possible to track the generation and decomposition of dioxins in each of these complicated processes. In addition, it is impossible to change and optimize the process conditions to reduce dioxins.

Since real-time monitoring of dioxins cannot be performed, the concentration of dioxins cannot be measured at many places in the incinerator. Dioxin generation status in each part cannot be grasped.

The present invention has been made in view of the above-mentioned problems, and improves the ionization efficiency in the path from the ion source to the mass spectrometer and transports it to the mass spectrometer with high efficiency. Atmospheric pressure ionization mass spectrometry for real-time measurement of gas, realizing highly sensitive measurement and analysis of extremely small amounts, and stably measuring exhaust gas that is likely to cause contamination in the ion source continuously for a long time. It is intended to provide a meter and an online monitoring device.

[0031]

[Means for Solving the Problems] (Structure of Ion Source Section) The present invention can be broadly classified by directly guiding a sample gas through a pipe.
A sample introduction unit for collecting and introducing the exhaust gas to be measured, and dioxins in the exhaust gas introduced from the sample introduction unit,
Actively utilizing the fact that chlorophenols and chlorobenzenes are likely to become negative ions, an ion source part that ionizes and secondary reacts under atmospheric pressure by negative corona discharge, and an ion generated in the ion source part It has a differential pumping section for transporting to a mass spectrometry section in a high vacuum region, and the mass spectrometry section is configured to detect an ion current of the generated negative ions.

In the ion source section, a corona discharge is generated between the needle-shaped electrode and the counter electrode by applying a high voltage between the tip of the needle-shaped electrode provided in the ion source section and the counter electrode. .

The sample introduced from the sample introduction part into the corona discharge area comes into contact with the corona discharge area, and an ion molecule reaction occurs. For example, when chlorophenols (CP) in dry air are introduced from the sample introduction section, the main ion / molecule reactions are as follows.

[0034] ^{_{O 2 + e - → O 2}} - ( primary ionization by thermal electrons generated by corona _{discharge) O 2 + N 2 → 2NO} ( primary ionization by thermal electrons generated by corona ^{_{discharge) O 2 - + NO → NO}} 3 - O ^{_{2 - + CP → (CP-}} H) - + HO 2 ion-molecule reactions (secondary ionization) where, (CP-H) ^- represents a negative ion which exits from the CP of protons.

N ₂ easily changes to NO ₃ − via the intermediate NO by a reaction with O ₂ under negative corona discharge, and is observed as a strong ion.

Next, chlorophenols (C
When P) is introduced from the sample introduction section, the following main reactions of ions and molecules are added by impurities such as hydrogen chloride, sulfuric acid, and bromine.

O ₂ ⁻ + HCL → CL ⁻ + HO ₂ ion molecule reaction (secondary ionization) CL ⁻ + CP ⇔ (CP-H) ⁻ + HCL ion molecule reaction Therefore, (1) ion to be detected (CP-H) ^- there is a high possibility that the amplification efficiency is lowered.

(2) If the needle electrode becomes dirty, the discharge becomes unstable, and the primary ionization (O ₂ ⁻ ) efficiency changes.

If the reaction of O ₂ ⁻ + NO ---> NO ₃ ⁻ can be suppressed in the ion / molecule reaction process as shown in the above equation, the decrease of O ₂ ⁻ can be suppressed.

Thus, O ₂ ⁻ + CP ---> (CP
-H) ^- + HO ₂ reaction proceeds.

[0041] The NO ₃ ^- To suppress generation reaction, O
It is important that the existence areas of ₂ ^- and NO do not overlap,
One method is to accelerate ions by a potential difference, and the ion acceleration force gives an ion acceleration force that exceeds the flow velocity in the traveling direction of the sample, thereby minimizing the existence time of the intermediate in the corona discharge region. .

In the above configuration, in the ion source section, an electric field is applied between the needle electrode and the electrode, the electrode is provided with a pore and communicates with the sample introduction section, and the sample flows into the pore. , The end of which is in contact with the corona stream.

Next, with respect to the stabilization of the corona discharge, a double tube or the like is used except for the tip of the needle electrode, so that the pure gas is opposed to the sample gas only at the tip of the needle tip. Is provided separately to the tip of the needle tip.

Further, as a countermeasure configuration when an impurity such as hydrogen chloride is interposed, the following are possible. (1) The impurity such as a removing material is removed before flowing into the sample introduction section.

(2) Alternatively, dilute the concentration of the contaminants,
Reduce its effects.

(3) The efficiency of corona discharge is increased.

Although there are other means, the present part of the present invention is mainly provided with the means described in (2) and (3) above.

That is, the corona stream is centralized,
The sample is introduced into the centralized portion.

Alternatively, the sample introduced into the sample introduction section is divided, and a corona stream is brought into contact with each of the divided sample fluids to multiply the sample fluid by n times.

Alternatively, the ionization section where the corona discharge proceeds and the chamber where the ions can be efficiently extracted are separated and independent.

Further, by providing a bypass pipe capable of supplying a pure gas to the sample introduction section, it is possible to dilute contaminants and efficiently extract ions.

(Air Curtain Unit) The first stage of the differential exhaust unit that takes in the ionized sample of the sample is located on the other surface of the sample introduction unit (the surface facing the corona discharge area). And A pore is provided at the first stage of the differential pumping section, and the counter electrode (first electrode) in the corona discharge area is provided.
And an electric field is formed between them. Generally, there is a parallel electric field, and the ions are concentrated in the pores by the aid of the electric field.

The flow of the sample is generally divided into the flow to the ionization section and the flow to the first-stage fine holes in the differential pumping section.
For this reason, when highly corrosive molecules such as hydrogen chloride, hydrogen sulfide, and bromine chloride are present in the exhaust gas, these molecules flow into each chamber of the differential exhaust unit and the mass spectrometric unit. At this time, the detection sensitivity is lowered, and at the same time, the high vacuum chamber is corroded, and the frequency of maintenance is increased. If the inflow of such corrosive fluid can be prevented, improvement in maintainability can be expected, and stable measurement can be continued without deterioration of the background of the mass spectrometer.

According to the present invention, at least one separator (second electrode) is added to the first stage of the differential pumping section, and a hole for taking the ionized sample is provided on the axis thereof.
A chamber formed between the facing surface side of the separator and the first stage (first pore) of the differential exhaust section is filled with a pure gas such as dry air. In addition, a voltage is applied to the separator (second electrode), and the generated sample ions are extracted by a potential difference from the first electrode. The ions are mixed with a pure gas such as the dry air and flow into the differential exhaust unit.

As a result, only the secondary ionized sample ions are separated, the background is improved, and since corrosive gas does not flow, stable measurement can be continued.

(Differential Exhaust Portion) In the present invention, ions generated by the ionization portion under atmospheric pressure are passed through the first vacuum chamber and the second vacuum chamber, which are gradually reduced in pressure, and the mass of the high vacuum chamber is reduced. With respect to the shape and arrangement of the exhaust system to be introduced into the analysis unit, a configuration capable of further improving ion permeability is achieved by the following means.

(1) The portion between the portion in contact with the sample ionized under atmospheric pressure (the first stage of the differential pumping portion) and the final portion in contact with the mass spectrometer is divided into at least two or more chambers. The pressure was set to an ion beam shape (a viscous flow), and the opening diameter for passing ions was set.

(2) The pressure at the first stage in the above item (1) is 0.1 to 10 Torr. Knudsen number (K
n) The diameter and pressure satisfying ≦ 1.

(3) The pressure at the last stage of the differential pumping section in contact with the mass analysis section in the high vacuum region in the above item (1) is determined by: The Knudsen number (Kn) is set to a diameter and a pressure satisfying 1 <Kn <15 by the pressure of the chamber.

(4) The pressure decay rate of the differential pumping section in the above items (2) and (3) is 1/10 to 1/100.

The sample ions ionized under the atmospheric pressure are as follows:
The light passes through the first stage (first pore) of the differential pumping section and enters the first stage low vacuum chamber (first chamber) at a pressure lower than the atmospheric pressure. At this time, the gas molecules become a supersonic jet, and a shock wave and a Mach disk depending on the pressure (P1) of the first chamber are generated.

That is, gas molecules entering the first chamber from the atmospheric pressure through the first pores are rapidly cooled by adiabatic expansion, adiabatically compressed on the Mach disk surface, and rapidly heated. As for the shape of such a shock wave, as described in detail in the Transactions of the Japan Society of Mechanical Engineers (B), Vol. 50, No. 449, pp. 223-240 (Showa 59-1), the diameter Db of the shock wave (barrel) Shock diameter), Mach disk surface position X
An empirical formula for obtaining m is obtained as the following formula.

Db = 0.78 * d1 * (P0 / P1) ^0.41 (1) Xm = 0.28 * d1 * (P0 / P1) ^0.68 (2) where P0 is the atmospheric pressure and P1 Represents the pressure in the first chamber, and d1 represents the first pore diameter.

The mean free path and Knudsen index corresponding to the molecular pressure can be expressed by the following equations.

Λ = 0.05 / Pi (3) Kn = λ / di (Knussen number: index of molecular flow and viscous flow) (4) Kn <1 Nozzle beam flow (viscous flow) Kn ≧ 1 Here, Pi represents the pressure of a certain vacuum chamber, and di represents the pore diameter provided.

Equation (3) shows the mean free path of molecules in the differential pumping section and is expressed as a function of pressure. Further, there is a Knudsen number (Kn) as shown in Expression (4) as a discrimination index between the nozzle beam flow and the molecular flow. Under the condition of Kn ≦ 1, when a gas is ejected into a vacuum from a fine hole such as a nozzle, molecules in the gas expand adiabatically while colliding with each other. At the end of the adiabatic expansion, there is no collision between the molecules, suggesting that it can be taken out as a molecular flow through the pores.

From the above equations (1) and (2), the diameter Db of the shock wave in the first chamber and the generation position Xm of the Mach disk surface are as follows:
It depends on the first pore d1 and the pressure P1 in the low vacuum chamber.

Inside the shock wave, that is, in the jet, ions and other molecules are rapidly cooled, and solvent molecules such as water and alcohol are added to the ions to generate cluster ions. If mass analysis is performed with such cluster ions, there arises a problem that information on the molecular weight of the original ions cannot be obtained. Therefore, it is necessary to remove molecules such as water and alcohol added from such cluster ions (desolvation). However, as described above, the molecular flow cooled by adiabatic compression and adiabatic expansion on the Mach disk surface is , Is adiabatically compressed on the Mach disk surface and is rapidly heated, so that the desolvation of cluster ions is promoted.

For this reason, the position of the second pore located behind the first pore is set to a value equal to or greater than the value determined by the equation (2).

This can be achieved most easily without the need for a special energy supply or the like. However, behind the Mach disk surface, the flow of molecules is free jet (dispersed),
There is also a disadvantage that the amount of ions incident on the second pore is reduced. Therefore, based on the shape of the generated shock wave, each pore diameter and its position were set so that ion desolvation was promoted and the amount of ions incident on the second pores was improved.

In addition, the ions that have been in a gas molecular fluid behavior under a high pressure have a longer mean free path as the pressure gradually decreases. At this time, when an electric field is generated in the direction in which the ions are accelerated, the ions accelerate in the electric field and fly repeatedly to collide with neutral molecules. By this collision, water molecules and the like can be desorbed. Therefore, in order to generate an ion accelerating electric field in the low vacuum chamber, intermediate vacuum chamber, and high vacuum chamber,
A voltage of V1V2V3 is applied to each of the first pore electrode, the second pore electrode, and the third pore electrode from the ion acceleration power supply. Here, when the ions are positive ions, the application is performed so that V1>V2> V3, and when the ions are negative, the application is performed so that V1 <V2 <V3. By adjusting and setting these potentials, the degree of desolvation due to collision between ions and neutral molecules can be changed.

Further, the ionized molecular flow becomes a nozzle beam or a molecular flow depending on the pressure setting of each chamber and the provided pore diameter and position, and changes depending on the provided pore diameter and position and the exhaust capacity of the first pump.

The inventors of the present invention have obtained various parameters by experiments and found that the following means can be used to improve the amount of ions passing through each chamber of the differential pumping section. That is, (1) the final stage chamber of the differential pumping section is set to have a pore diameter and a pressure that do not cause a molecular flow, using the Kn value determined by the equation (4) as an index.

(2) The pore diameter of each chamber is equal to or larger than the barrel shock diameter (Db) determined from the pressure difference and the pore diameter determined by the equation (1), and the interval is determined by the equation (2). Secure several times the distance.

(3) The pressure gradient ratio (P0 / P1) of the differential pumping section, which is provided between the first stage chamber in contact with the ion source under the atmosphere and the last stage in contact with the high vacuum section, is 1/10 to 1/100.
It was made to decrease gradually to the extent. The limit number of rooms was two or more.

(Apparatus) The concentration of dioxins in exhaust gas is less than 1 ppt, and the concentration of chlorophenols and chlorobenzenes is said to be about 1 ppb.
In order to monitor such a trace amount of components, the following two items are important.

(1) Efficiently emit a signal from a trace component.

(2) The components (nitrogen, oxygen, carbon dioxide, etc.), which are much more abundant than the trace components, do not generate an interference signal, that is, a high S / B ratio (B: background) We need a technique that can be achieved.

As a result of many experiments, the present inventors have found that atmospheric pressure chemical ionization in the negative ion mode is most suitable for selective ionization and detection of dioxins and the like in exhaust gas.

Further, as described above, by providing the ion source and the differential pumping unit, even a very small amount of components such as dioxins can be efficiently used by thermoelectrons generated by negative corona discharge at atmospheric pressure. Well, stably ionized,
The ions can be transported to the mass spectrometer with high transmittance. Therefore, stable high-sensitivity measurement can be performed continuously for a long time.

With the above configuration, in the present invention,
First, a sample is introduced from the sample introduction unit into the ion source unit, and is ionized by ionization means such as corona discharge to generate primary ions. The primary ions ionize a target substance in the sample gas by a secondary reaction (ion / molecular reaction) with the sample gas continuously supplied from the sample introduction unit.

The generated ions are taken out to the ion collection pores provided on the surface of the sample introduction section facing the corona discharge area. The sample ions passing through the pores are taken into a chamber filled with pure dry gas provided at the first stage of the differential pumping section. Since this pure gas is continuously flowing due to the pressure difference between the first pores of the differential exhaust portion, it is taken into the differential exhaust portion along the flow. Since this portion includes only the pure gas and the sample ions, the exhaust gas does not flow in (air curtain). Therefore, the exhaust gas does not flow into the differential exhaust portion and the mass analysis portion further downstream.

In the sample introduction section, the exhaust gas and the secondary ions are mixed, and the ions are transported by the potential difference (electric field force) applied to the Gorona discharge electrode and the electrode having the ion collection pores. . Therefore, even if the flow of the exhaust gas is disturbed, the ions are efficiently transported to the ion collection pores.

Alternatively, the ion generating section and the sample introducing section are arranged coaxially in the mixing section, and the sample introducing section is arranged so as to include the ion generating section (double tube structure), so that the primary ion is formed. The flow of the gas for generation and the flow of the sample gas are made parallel, and the flow of this gas is set so as to be directed to the pores. Even when the gas flows are parallel, mixing by diffusion of gas molecules is performed, so that ions of the target substance are generated.

With this configuration, the turbulence of the gas flow due to mixing can be reduced, so that the dissipation of ions is reduced and the amount of ions reaching the pores can be prevented from being reduced. By making the flow rates of the sample gas and the gas for generating primary ions substantially the same, the turbulence of the gas flow can be further reduced.

In the mixing section, a gas outlet is provided in the direction along the surface having the pores, so that the gas does not recirculate in the direction of the gas outlet of the sample introduction section or the ion generation section. Can be reduced, the ions are efficiently transported to the pores, and the amount of detected ions increases.

As described above, the ions ionized under the atmospheric pressure pass through the first vacuum chamber and the second vacuum chamber, which are gradually reduced in pressure, and are introduced into the mass analysis section of the high vacuum chamber. With respect to the shape and arrangement, the above-mentioned means are used to improve the ion permeability.

For example, the pore diameter d2 of the second pore is at least three times the pore diameter d1 of the first pore, and the transmittance is improved as the pore diameter of the second pore increases. This is because, even if the size Db (barrel shock diameter) of the jet generated in the first chamber changes in pressure, the value of d1 becomes 3 to 5 times as large, By increasing the pore diameter d2 of the sample, the ion transmittance was improved.

According to the equation (2), the position Xm of the Mach disk surface generated in the first vacuum chamber, that is, the distance from the first pore to the Mach disk surface, is determined by the following equation. The higher, the shorter. Accordingly, when the pressure P1 in the first vacuum chamber is relatively high, the position Xm of the Mach disk surface generated in the low vacuum chamber is short, whereas the pressure P1 in the first vacuum chamber is relatively low. If so, the second pore position is long. For this reason, the dispersion of the molecular flow became prominent behind the Mach disk surface, and the amount of ions incident on the second pores decreased.

If the position of the second pore is long, the kinetic energy of the ions is likely to be consumed due to collision with the neutral gas, so that the ions hardly reach the second pore, and the pressure dependence of the low vacuum chamber is reduced. Got higher.

Therefore, the position of the second pore is defined as the first pore diameter d1.
By setting the distance to be at least several times as large as the above, the dependence of the ion transmittance on the first vacuum chamber pressure P1 and the position at which the Mach disk is generated can be reduced, and a stable high ion transmittance was obtained.

Further, the pressure and the pore diameter of the final chamber in contact with the mass spectrometry section of the differential pumping section are set by the following equation (4):
When each vacuum chamber was formed so that the pressure decay ratio was 1/10 to 1/100, a stable and high ion transmittance was obtained.

By providing the above-mentioned ion source and differential pumping unit, it is possible to detect dioxins, chlorophenols and chlorobenzenes having plural chlorine and oxygen elements in the exhaust gas with high sensitivity. Was.

The chlorine and oxygen are elements having a high electronegativity, and organic compounds containing many of these elements tend to capture low-energy thermoelectrons and become negative ions. Chlorophenols have at least one chlorine atom and one oxygen atom in the molecule. Chlorobenzenes have a chlorine atom in the molecule.
I have one or more. The highly toxic dioxins have from 4 to 8 chlorine atoms and 2 oxygen atoms in the molecule.

For this reason, dioxins and the like are efficiently ionized by thermionic electrons generated by negative corona discharge at atmospheric pressure, and can be continuously monitored by incorporating them into a mass spectrometer without attenuating the amount of ions.

[0096]

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

(Ion Source Unit) FIG. 1 is a view showing the entire configuration of an apparatus to which an ion source unit and a differential exhaust unit according to the present invention are applied.

The sample introduced through the sample connection pipe 400 is supplied to the sample introduction pipe 34 provided on the sample introduction flange 33.
Through the sample introduction flange 33. Part of the sample introduced into the sample introduction flange 33,
The sample is introduced into the ionization chamber 10 and the rest is the sample introduction flange 3.
The liquid is discharged from the discharge pipe 36 provided in 3.

The sum of the flow rate introduced into the ionization chamber 10 and the flow rate discharged from the discharge pipe 36 is about 1-2 liters.
(Liter) / min (minute). These flow rates are set by a flow meter 402 and a variable throttle device 401 provided in the sample connection pipe 400. The flow meter 402 and the variable aperture device 401 may be integrated by a mass flow controller.

The sample to be introduced into the ionization chamber 10 flows out through the pores 21 of the first electrode 2 provided on one surface of the sample introduction flange 33, and its stream lines do not diffuse through the pores 21.

The sample containing the detector is ionized in a corona discharge region generated between the first electrode 2 and the needle-shaped electrode 1 to which a high voltage has been applied. This part corresponds to the “ionization part” shown in FIG. The voltage applied to the needle electrode 1 is about 1 to 6 kV when generating positive ions and about -1 to -6 kV when generating negative ions. Supply by the method.

The ionization and molecular reaction occur in a corona discharge region generated between the first electrode 2 and the needle electrode 1 to which a high voltage is applied.

[0103] The NO ₃ ^- To suppress generation reaction, O
₂ ^- and since the existing area of NO is important not to overlap, by increasing the sample rate flowing out through the pores 21, O ₂ ^- + NO -> NO ₃ ^- reaction was inhibition of.

[0104] In ^{_{addition, O 2 - + CP ->}} (CP-H) -
It was confirmed that the ions generated by + HO ₂ were able to overcome the flow and extract ions by the electric field generated between the first electrode 2 and the needle electrode 1 to which a high voltage was applied.

The above O ₂ ⁻ + HCL ---> CL ⁻ + H
The reaction of O ₂ can be reduced to some extent by the removing agent provided in the sample connection tube 400. However, since a 100% removal rate cannot be expected, even if corrosive gas such as HCL is present to some extent, it can be put to practical use in continuous measurement as long as the efficiency of the ionization section is constant and stable. For this reason, it is desirable that the ion source be configured to ensure stable corona discharge and durability.

In the present invention, a means for separately supplying a pure gas such as dry air or argon to the ionization section where the needle electrode 1 is located is provided to the ionization section in order to secure the corona discharge and durability. This supply amount is generally set lower than the flow rate flowing out of the pores 21.

The description will be made with reference to FIG. The needle electrode 1 is fixed to the tip of the needle holder tube 11 and the needle holder tube 11 is fixed.
One end is connected to a back gas supply pipe 12, and the other end is provided with an HV terminal 13 for supplying power.

At the end of the back gas 2 supply pipe 12, a back gas connection pipe 300 for supplying a gas such as dry air or argon from the outside, and a flow meter 3 for controlling the amount thereof.
02 and a variable aperture device 301 are provided.

In such a configuration, the gas having a known component such as the dry air or argon is always supplied as a parallel flow through the needle holder tube 11 to the needle electrode 1.
In particular, when the supply fluid is dry air, oxygen, which is a seed source of primary ionization, can be continuously supplied to the corona discharge region, so that a constant primary ion independent of the oxygen concentration in the sample gas is supplied. Can be generated. Therefore, corona discharge is stabilized. Further, since this supplied gas serves as a siled gas for isolating the needle tip, which is at the highest temperature, the gas is further stabilized and the needle electrode 1 is prevented from being corroded. Therefore, continuous use and maintenance costs can be saved.

The needle holder tube 11 is attached to a needle fixing bracket 14, and the needle fixing bracket 14 is configured to be attached to an ionization flange 15 so as to be detachable. With this configuration, even in the event that the corona discharge portion is hindered, only this portion can be easily regenerated by replacement, cleaning, or the like, so that the maintainability is improved.

The sample that has passed through the ionization section is discharged from a first discharge pipe 6 provided on the ionization flange 15. On the other hand, the first heater 7 is further mounted on the ionization flange 15. This is provided to keep the ionization temperature of the ionization section constant. This further stabilizes ionization.

Further, the ionization flange 15 is attached to the sample introduction flange 33 via the terminal plate 22. The first electrode 2 is mounted inside the terminal plate 22, and terminals of the terminal plate 2 are connected to a drift power supply 120 via a power supply line 121.

Further, in such a configuration, the needle electrode 1, the pore 21, the ionization flange 15, and the sample introduction flange 33 are coaxially arranged, and are unitized by function (corona needle discharge section, sample exhaust / (Hot section, corona discharge electrode section, sample introduction section), so that disassembly, reassembly, and replacement work can be performed in each unit.

The ionized molecules such as the detector, oxygen, and HCL pass through the fine holes 21 and flow into the sample introduction flange 33 in the diameter range of the fine holes 21. This is because the flow velocity in the sample introduction flange 33 is lower than the flow velocity in the corona discharge region, and the kinetic energy of the ionized molecules is large, so that ions can be extracted even when the flow reverses to the flow of the sample. Means

Next, these ionized molecules may be taken into the first stage of the differential pumping section described later.
There is no problem if the diameter of the first stage portion of the differential pumping section is the same as the diameter of the fine hole 21, but generally the pumping capacity of the pump provided in the differential pumping section is limited. ~ 1mm
About. Therefore, it is necessary to converge the generated ions before taking them into the first stage of the differential pumping section. Further, corrosive gas such as HCL is also contained in the generated ions. When these gases flow into the differential exhaust section or the mass spectrometry section described later, the detection sensitivity is deteriorated and the durability of the apparatus itself is reduced. Further, there is a concern that replacement and regeneration of each component in the vacuum chamber will greatly deteriorate maintenance. For this reason, in the present invention, means for converging ions flowing out to the sample introduction flange 33 and a configuration in which corrosive gas such as HCL is not allowed to flow into a vacuum chamber described later.

A description will be given with reference to FIGS. As mentioned above,
The flow velocity in the sample introduction flange 33 is lower than the flow velocity in the corona discharge region, and the kinetic energy of the ionized molecules is large. Therefore, the other surface of the sample introduction flange 33 (the surface facing the pore 21)
An electrode may be formed on the side, and acceleration and convergence may be achieved by electric energy.

In the present invention, the second electrode 3 is provided on the other surface (the surface facing the pore 21) of the sample introduction flange 33. Therefore, a potential difference is generated between the first electrode 2 and the second electrode 3, and the ions are accelerated by the potential difference. An example of the equipotential line is indicated by “potential line 1-2” in FIG. According to this potential line, the contour lines are curved in the radial region of the pores 21 and the pores 31 of the second electrode. I was able to confirm that. That is, the first electrode 2 and the second electrode 3 are arranged in parallel, and only the shape of the hole through which the ions pass through the pores 31 concentrates the potential, for example, an acute angle (see FIG. 2). 31a) Alternatively, the end faces are positively made convex to converge. Further, by arranging the pores 31 and 21 coaxially,
Since there is no eccentricity in the ion passage portion of the “ion drift A portion”, the ions can drift efficiently. In the figure, “-----
The symbol ">" indicates the trajectory of ions at the outermost periphery when the tip of the pore 31 is not made to be a convex portion. Since there is no convergence and the ions are absorbed by the second electrode 3, the efficiency is improved. Is reduced.

(Air Curtain Section) Next, ions that have passed through the ion drift A section 20 in the sample introduction flange 33 flow into the fine holes 31 of the second electrode 3. At this time, the corrosive gas is provided on the other surface side of the second electrode 3 (on the back side of the surface through which the sample gas flows) by providing a pure gaseous substance having a pressure equal to the pressure of the chamber 33 for introducing the sample. Can be prevented from flowing in, and this is convenient for a differential exhaust unit and a mass spectrometer described later.

In the present invention, the pure gas body is drawn into a sealed micro space between the second electrode 3 and the first flange 4 of the first fine hole of the differential pumping section. This space is provided between the second electrode 3 and the first pore 4 by the terminal plate 32.
Alternatively, a back gas supply pipe 44 is provided at a position other than the first fine hole 41 of the first fine hole first flange 4 with a seal member interposed therebetween, and dry air is provided at the tip of the back gas supply pipe 44 from the outside. A back gas connecting pipe 303 for supplying a gas having a known component such as argon, nitrogen, helium, etc., a flow meter 305 for controlling the amount thereof, and a variable throttle device 304
Is provided.

In this configuration, pure gas such as dry air, argon, nitrogen, helium or the like is always supplied into the space via the back gas supply pipe 44, and is supplied from the first fine holes 41. It flows into the differential exhaust part. At this time, by setting the flow rate substantially equal to the flow rate drawn into the differential chamber, the sample gas does not flow at all. Further, as shown in FIG. 2, since the position of the back gas supply pipe 44 and the position of the first fine hole 41 are isolated, the stream lines thereof are concentrated on the first fine hole 41. Also, the first pores 41 and the pores 31 of the second electrode 3 are formed.
Are arranged coaxially to prevent diffusion of ions.

On the other hand, the ionized molecules drawn out to the pores 31 of the second electrode 3 are mixed in the gas stream of the dry air, argon, nitrogen, helium or the like.
At this time, since the streamlines are concentrated in the first pores 41, they are efficiently taken into the first pores 41 (since they are mixed along the streamlines).

Further, as shown in FIG.
Applies a voltage from outside via the terminal plate 32 and the first drift power supply 120 and the connection line 122. At this time, a potential difference is generated between the first pore 41 and the second electrode 3 and the potential is accelerated, and ions can be converged on the first pore 41 by the convex shape of the first pore 41. (Refer to the shape of the ion drift B portion 30 in FIG. 2) That is, the ionized molecules extracted to the pores 31 of the second electrode 3 flow through the gas flow such as dry air, argon, nitrogen, and helium. Physical strength, the first pores 41 and the second electrode 3
With the help of the electric field force, the particles are transported to the first pores 41 with high efficiency. Also, since the sample gas does not flow, the vacuum chamber is filled only with a high-purity inert gas dilute fluid,
The influence of the chemical noise or the back gas is reduced, and a long-term continuous operation is possible.

In such a configuration, when measuring positive ions, the voltage of the first electrode 2 is set higher than that of the second electrode 3.
The voltage of the electrode 3 is about 300 V, and the voltage of the first flange first flange 4 is about 50 V. Conversely, when measuring negative ions, the first electrode 2 is opposite to the case of measuring positive ions.
Is set higher than that of the second electrode 3, and actually the first
The electrode 2 is about -1000 V, the second electrode 3 is about -300 V,
The voltage of the first pore first flange 4 is about -50V.

Further, the ion drift A portion 20 in the sample introduction flange 33 and the ion drift B portion 30 between the second electrode 3 and the first fine hole first flange are more stable when the temperature is made uniform. Therefore, a heater 35 is provided at one end of the sample introduction flange 33 and a heater 4 is provided at the first pore first flange 4.
2 to control the outside and make the temperature uniform.
(Not shown) (Differential Exhaust Portion) As described above, the generated positive or negative ions are taken into the first pore 41. In the present invention, the shape and arrangement of an exhaust system in which the ions captured by the first pores 41 are passed through a vacuum chamber whose pressure is gradually reduced and introduced into a mass spectrometer (chamber) of a high vacuum chamber. As a result, a differential exhaust unit configuration capable of further improving ion permeability has been achieved. Hereinafter, description will be made with reference to FIGS.

The sample ions ionized under the atmospheric pressure enter the first vacuum chamber (first chamber 50) at a pressure lower than the atmospheric pressure through the first pores 41 of the differential pumping section. At this time, the gas molecules become a supersonic jet, and the shock wave 53 depending on the pressure (P1) of the first chamber 50 and the Mach disk surface (D
b1) occurs.

That is, gas molecules entering the first chamber 50 from the atmospheric pressure through the first pores 41 are rapidly cooled by adiabatic expansion and adiabatically compressed on the Mach disk surface (Db1).
Suddenly overheated.

As described above, the diameter Db of the shock wave and the generation position Xm of the Mach disk depend on the first pore d1 and the pressure P1 in the low vacuum chamber. Inside the shock wave, that is, in the jet, ions and other molecules are rapidly cooled, and solvent molecules such as water and alcohol are added to the ions to generate cluster ions. If mass analysis is performed with such cluster ions, there arises a problem that information on the molecular weight of the original ions cannot be obtained.

At this time, generally, it is necessary to remove molecules such as water and alcohol added from such cluster ions (desolvation). However, as described above, the adiabatic compression and adiabatic expansion on the Mach disk surface is required. Is cooled adiabatically on the Mach disk surface and rapidly heated, thereby promoting the desolvation of cluster ions. For this reason, the second pores 5 arranged behind the first pores 41
The position of 1 is set to be equal to or larger than the value obtained by the equation (2).

However, this method does not require a special energy supply or the like, and is most easily achieved. However, the flow of molecules behind the Mach disk becomes free jet (dispersion).
However, there is also a disadvantage that the amount of ions incident on the second pore 51 decreases. Therefore, based on the shape of the generated shock wave, the pore diameter, position, and pressure (exhaust method) are adjusted so that ion desolvation is promoted and the amount of ions incident on the second pore 51 is improved. Need to optimize.

As a result of various experiments, the diameter of the second pores 51 was three times or more the diameter of the first pores 41. As the diameter of the second pores 51 increased, the transmittance improved. . This is because, as shown in equation (1), the size Db (barrel shock diameter) of the jet generated in the pressure chamber of the first chamber 50 is:
Even if the pressure changes, the value of d1 becomes 2.4 to 4.6 times as large, and the diameter of the second pore 51 is set to be large in accordance with the change, thereby improving the ion transmittance.

The position Xm of the Mach disk surface generated in the first chamber 50, that is, the distance from the first fine hole 41 to the Mach disk surface is determined by the equation (2) as follows: The higher, the shorter.

Therefore, the position Xm of the Mach disk surface generated in the first chamber 50 depends on the pressure P1 of the first chamber 50.
Is relatively high, Xm is short. On the other hand, when the pressure is low, Xm becomes a much larger value, and the dispersion of the molecular flow becomes remarkable behind the Mach disk surface.
The amount of ions incident on the diameter of decreases.

Further, if the position of the second pore 51 is long, the kinetic energy of the ions is likely to be consumed due to collision with the neutral gas, so that the ions hardly reach the second pore 51, and Pressure dependency increases.

Therefore, by setting the position of the second pore 51 at a distance equal to or more than Xm obtained from the equation (2) and at most 35 times the diameter of the first pore 41, the position of the first chamber 50 is reduced. Since the dependency of the ion transmittance on the internal pressure and the position at which the Mach disk was generated can be reduced, a stable and high ion transmittance was obtained.

The pressure in the first chamber 50 is 0.1 to 1
0 Torr, and as shown in FIG. 3, the second drift power supply 130 connects between the first pore first flange 4 (via the first pore second flange 43) and the second pore flange 5. A potential difference is given. Therefore, as shown in FIG. 3, the ions once diffused to the dB diameter exhibit an orbit converged by the electric field and converge within the diameter of the second pore 51.

[0136] Such a configuration method may be applied to each chamber of the differential evacuation section sequentially. However, as described above, since the pressure is gradually reduced, the opening diameter increases, and the first The pumping capacity of the pump is increasing, which is not advisable. On the other hand, the pressure of the mass spectrometer is generally 1 × 10 ⁻⁶ to
A pressure of 1 × 10 ⁻⁴ Torr was required. In this pressure range, ions were extracted as a molecular stream having excellent directivity and whose orbit could be easily controlled by an electric field.

Therefore, according to the present invention, the ion beam flow (jet flow) is successively performed up to the last stage chamber (70 in FIG. 3) of the differential chamber.
And converging by electric field assistance, and ejecting a molecular flow of ions from the opening diameter to the mass spectrometer. In such a method, it is necessary to determine the pressure and the diameter of the jet at the final stage of the differential exhaust section. For this reason, generally, it can generally be determined by equation (4).

From the equation (4), di is φ0.2 to 1.5 m from the practical pumping capacity of the first pump and the pressure of the mass spectrometer.
m is the limit. For this reason, the boundary pressure between the nozzle beam and the molecular flow in such a diameter range is expressed by the equation (3) and 1 <Kn <15.
By analogy with the range of about 0.25 to 0.001 Torr
Becomes This value is the pressure set value of the final stage chamber of the differential chamber, and is (0.1 to 0.1) relative to the initial stage pressure of the differential chamber.
10 Torr), by sequentially determining the barrel shock diameter (Db) and its position, it is possible to configure a differential exhaust unit in which the amount of ion transmission is not attenuated.

As a result of various experiments and calculations of the set parameters, at least two chambers were set between the part in contact with the sample ionized under the atmospheric pressure (the first stage of the differential pumping unit) and the last stage in contact with the mass spectrometer. And the pressure at the first stage in the differential chamber is set to 0.1 to 10 Torr, and the pressure at the final stage of the differential exhaust unit in contact with the mass analysis unit in the high vacuum region is set to 0.25 to 0.001 Torr. By setting the pressure decay rate between the differential exhaust portions to 1/10 to 1/100,
High ion permeation was obtained.

FIGS. 1 and 3 are diagrams showing the configuration of a differential exhaust unit composed of three chambers based on the index.
Shows the ion orbit in detail.

In such a configuration, the pressure in the first differential chamber 50 between the first and second fine holes 41 and 51 is about 0.1 to 3
Torr, the pressure attenuation ratio of the second differential chamber 60 between the second pore 51 and the third pore 61 is about 1/10 to 1/20, and the third pore 61 and the fourth The pressure in the third differential chamber 70 between the holes 71 is about 1/10 to 1/20 by making the pressure attenuation ratio 0.001 to 1/20.
It was possible to reduce the pressure to 0.01 Torr, and the ions were extracted as a converged ion beam flow having a diameter of about 0.2 to 0.6. This ion beam is applied to the fourth pore 71
(Φ0.2-1.0), and becomes a molecular flow in the mass spectrometer 80.

In such a configuration, the ions that have been in an ion beam flow (viscous flow) behavior under a high pressure have a longer mean free path as the pressure gradually decreases. At this time, when an electric field is generated in the direction in which the ions are accelerated, the ions accelerate in the electric field and fly repeatedly to collide with neutral molecules. By this collision, water molecules and the like can be desorbed, and the convergence thereof is improved as the pressure becomes lower, as in the above-mentioned ionized portion. Then, the first fine pores of the first fine pores 41 that form the respective qualities of the differential chamber are first.
In order to generate an ion accelerating electric field in the flange 4, the second pore flange 5 of the second pore 51, the third pore flange 6 of the third pore 61, and the fourth pore flange 7 of the fourth pore 71, The second drift power source 130 applies voltages V1, V2, V3, and V4 to the respective pore flanges. Here, when the ion is a positive ion, V1>V2>V3> V4, and when the ion is negative, V1 <V2 <V3 <V
4 was applied.

Each of the pores in each of these flanges is arranged coaxially to suppress misalignment of the ion transmission region due to eccentricity. Furthermore, by adjusting and setting these potentials from the outside, the degree of desolvation caused by collision of ions with neutral molecules is changed.Furthermore, even if convergence of ions and errors during assembly occur. The error is absorbed.

The exhaust pump provided in the differential pumping section includes:
An exhaust pump such as a rotary pump, a scroll pump, a mechanical booster pump, or a turbo molecular pump can be applied. In FIG. 1, the scroll pump 210 is used for exhausting the differential exhaust unit (the exhaust amount is 300 to 900 l / mi).
n), and the case where a turbo molecular pump 220 (discharge amount is about 150 to 300 l / s (second)) is used for exhausting the mass spectrometric unit 80. The back pressure of the turbo molecular pump 220 is shared by the scroll pump 210 by the connecting pipe B76. Further, each of the flanges is provided with fine holes 52, 62, 72 for adjusting the respective pressures, so that the pressure of each chamber can be adjusted according to the capacity of the applied exhaust pump.

(Mass Spectrometer) The ions in the molecular stream region flowing out of the final stage of the differential pumping section are first
The light is converged by a first converging lens 81 provided at the entrance of “0”. This converging lens usually has three lenses (81,
82, 83) are used.

Next, the focused ions further pass through a lens electrode 84 having a slit. The convergent lens 8
By the electrodes 1, 82, and 83, the ions passing through the fourth pore 71 converge at the lens electrode 84, and neutrons and the like that do not converge collide with the slit portion of the lens electrode 84, and move toward the mass analyzer. It is difficult to access.

The ions passing through the lens electrode 84 are
The light is polarized and converged by a double-cylindrical polarizer comprising an inner cylinder electrode 86 and an outer cylinder electrode 85 having a large number of openings. In the double-cylindrical polarizer, the light is deflected and converged by using the electric field of the outer cylinder electrode 85 that has permeated through the opening of the inner cylinder electrode 86.

The ions having passed through the double cylindrical polarizer are introduced into the ion trap mass spectrometer. The ion trap mass analyzer includes a gate electrode 91a, an end cap electrode 92, a ring electrode 94, a brim electrode 921, an insulating ring 93, and an ion extraction lens 91b.

The gate electrode 91a serves to prevent external ions from being introduced into the mass spectrometer when the ions trapped in the ion trap mass spectrometer are taken out of the ion trap mass spectrometer.

The pore 92a of the end cap electrode 92
The ions introduced into the ion trap mass spectrometer through the ionizer collide with a buffer gas such as helium introduced into the ion trap mass spectrometer, and their trajectories are reduced, and then applied between the end cap electrode 92 and the ring electrode 94. By scanning the high frequency voltage thus extracted, the ions are discharged out of the ion trap mass spectrometry section through the pores 92b of the end cap electrode 92 for each mass analysis number, passed through the ion extraction lens 91b, and then converted into the ion converter 101 and the ion detector 2.
00 is detected. The buffer gas is continuously supplied from a back gas cylinder 105 such as He provided outside via a back gas connection pipe 104 and a back gas supply pipe 103.

The pressure inside the ion trap mass spectrometer when the buffer gas was introduced was 10 ⁻³ to 10 ⁻⁴ To
rr. The ion trap mass spectrometer is controlled by a mass spectrometer controller (not shown).

One of the merits of the ion trap mass spectrometer is that it has a characteristic of trapping ions, so that even if the concentration of the sample is low, it can be detected by extending the accumulation time. Therefore, even when the sample concentration is low, the ion can be concentrated at a high magnification at the ion trap mass spectrometer, and the pretreatment of the sample such as concentration can be greatly simplified.

For mass analysis of the generated ions, various types of mass spectrometers can be applied. For example, a quadrupole mass spectrometer that performs mass separation using the same high-frequency electric field, a mass spectrometer in a magnetic field, and the like. The same applies to the case where a magnetic field type mass spectrometer using mass dispersion of the above or another mass spectrometer is used.

FIGS. 4A to 4D show other examples of the configuration of the ionization unit.

The configuration illustrated in FIG. 4A is different from the embodiment of FIG. 1 in that the needle electrode 1 is eliminated and the tip of the tubular needle holder 11 is positively shaped into a knife edge or a convex portion. The configuration is such that corona discharge is performed in the portion 11a.
The material of the needle holder 11 is preferably stainless steel, Hastelloy, copper, or the like having excellent corrosion resistance.

In such a configuration, the function of generating the corona discharge and the function of the back gas flow path for stabilizing only the front end portion thereof are not changed, but have an effect of being more economical.

The configuration illustrated in FIG. 4B has a double tube configuration in which the needle electrode 1 is extended to the base of the HV terminal 13 and housed in the needle holder 1 as compared with the embodiment of FIG. . Further, a throttle portion 11b is provided at the outlet of the back gas of the needle holder 11. Therefore, the back gas can be supplied only to the tip of the needle electrode 1. Corona discharge can be more stabilized, and there is an effect that continuous operation can be performed for a longer time. The material of the needle electrode 1 is preferably stainless steel, Hastelloy, copper, or iridium having excellent corrosion resistance, an Fe alloy having low corrosion resistance, or Pt or Pt-Ir which is a noble metal.

In such a configuration, the function of generating the corona discharge and the function of the back gas flow path for stabilizing only the tip portion thereof are not changed, but the corona discharge can be further stabilized and the effect of continuous operation for a longer time can be obtained. There is.

The configuration illustrated in FIG. 4C is different from the embodiment of FIG. 1 in that the tubular needle holder 11 is omitted, the needle electrode 1 is extended to the root of the HV terminal 13, and the needle is fixed. Pores 1 for supplying back gas to metal fittings 14
41 is provided. The material of the needle electrode 1 is preferably stainless steel, Hastelloy, copper, iridium, or a noble metal such as Pt or Pt-Ir, which has excellent corrosion resistance.

In this configuration, the function of generating the corona discharge described above does not change, but the back gas can be filled in a wider range and a wider corona discharge region can be secured, so that the efficiency is improved. is there. In addition, since the configuration is simple, there is an effect that the maintainability is excellent.

The configuration illustrated in FIG. 4D differs from the embodiment of FIG. 1 in the tip of the needle electrode 1. The tip of the needle electrode 1 is formed of a cap-shaped thin plate member 1b,
A needle-like electrode 1a having a knife edge or a convex shape is joined to the center thereof, and a hole 1c through which the back gas flows is provided in a portion other than the center. The material of the electrode 1a is stainless steel, hastelloy, copper, iridium, or a noble metal such as Pt, P, which is excellent in corrosion resistance.
t-Ir and the like are preferred.

In such a configuration, the function of generating the corona discharge and the function of the back gas flow path for stabilizing only the tip portion thereof remain unchanged, but the back gas can be more concentratedly jetted to the needle electrode. Therefore, corona discharge can be further stabilized. Furthermore, there is an effect that the size can be reduced, the maintainability is excellent, and the economy is richer.

FIGS. 5A to 5F show other examples of the configuration of the ion drifts A and B, respectively.

The configuration illustrated in FIG. 5A is different from the embodiment of FIG.
The configuration is such that the flange 4 and the second electrode 3 are joined to have the same potential. Further, the fact that the first electrode and the second electrode form parallel equipotential lines is not different from the embodiment (FIG. 1). In this embodiment, the flow of the sample gas flowing into the ionization unit is By providing a gradient in the direction of the ionization section by the first electrode 2 and the second electrode 3, the flow of gas flowing into the ionization section is rectified. Further, the space formed between the second electrode 3 and the first pore first flange 4 is minimized, and the flow rate of the back gas 1 is accelerated. For this reason, the divergence of the ions flowing into the ion drift B portion can be suppressed.

Therefore, even with this configuration, the function of preventing the inflow of the sample gas and the function of the drift force of the ions are not changed, but there is an effect that the economy is enhanced, the sealing performance is improved, and the reliability is improved.

The configuration illustrated in FIG. 5B is different from the embodiment of FIG.
One part is formed of a component member 411 having the first fine hole 41 therein, the tip of the part is sharpened, and the part is detachable from the first fine hole first flange 4. In addition, the first pore first flange 4 and the member 41
Reference numeral 1 is sealed by a sealing means such as an O-ring.

In this configuration, the function is the same as in FIG. 1, but since the member 411 is formed as a single item,
This has the effect of improving maintainability.

Further, by making the tip of the member 411 sharp, an electric field is concentrated at the entrance of the first pore 41, so that the convergence of ions is increased and the transmittance is improved.

The configuration illustrated in FIG. 5C is different from the embodiment of FIG. 1 in that the first fine holes 41 in the first fine holes first flange 4 are provided with a large number of inflow paths 414 and first fine lines. It is formed of a member 411 having a hole 41, the tip of which is sharpened, and is detachable from the first flange first flange 4. In addition, the first pore first flange 4 and the member 4
11 are communicated by a predetermined gap 415 so that the member 416 does not come off.

In such a configuration, the function is the same as that of FIG. 1, but since the member 411 is formed as a single item,
This has the effect of improving maintainability.

Further, by sharpening the tip of the member 411, the electric field is concentrated at the entrance of the pore 41, so that the convergence of ions is increased and the contact area of the ion drift B can be increased. Therefore, there is an effect that the collection rate is increased and the ion transmittance is further improved.

The configuration illustrated in FIG. 5D is different from the embodiment in FIG. 1 in that the buffer gas inflow portion is provided in the sample flange 33, and the second electrode 3 and the terminal plate 32 are provided.
Has been deleted.

Therefore, in this configuration, the ion drift B portion is not provided. However, there is a potential difference between the first electrode 2 and the first small hole first flange 4, and the electric field is equal to the electric field. Since it is concentrated at the tip of the first pore 41, there is basically no difference in terms of ion convergence.

In this configuration, a part of the sample gas flows into the first pores 41 in the first pores first flange 4, but the concentration of the corrosive gas is also diluted with the buffer gas. Therefore, the same is true even with a dilution of about 2 to 10 times. This is a practical scale. In addition, in this configuration, if maintenance is performed up to the sample introduction flange 33, the vacuum chamber will not be broken, so that the instrument can be easily restarted.

On the other hand, since there is no decrease in transmittance due to the absence of one ion drift portion, the transmittance is almost the same as described above. Further, since the configuration is extremely simple and the number of components is small, there is an effect that the reliability of the device is improved and the economy is excellent.

The structure illustrated in FIG. 5E is different from the embodiment of FIGS. 1 and 5D in that the buffer gas inflow portion is provided in the sample flange 33, and the first pore first flange 14 A hole 41 for lowering the pressure of the ion drift B portion is formed in a hole 41 communicating with the first stage chamber (first chamber) 50 of the differential exhaust portion in the first fine hole first flange 4.
3 is provided.

In such a configuration, a pressure difference between the ion drift A and the ion acceleration force caused by the potential difference between the second electrode 3 and the first fine hole first flange 4 is added.

[0178] Therefore, there is an effect that the ion collection rate is further increased and the ion transmittance is further improved as compared with FIG. 5D.

The structure illustrated in FIG. 5F rectifies the flow of the first back gas between the second electrode 3 and the first flange first flange 4 as compared with the embodiment of FIG. The structure 37 is provided for efficiently taking the ions into the first pores 41 of the first pores first flange 4.

5A and 5D.
In the embodiment of the present invention, a metal mesh or sintered body is preferable,
In the embodiments of FIGS. 5B, 5C and 5E, a porous ceramic or a porous filter or filter made of glass is suitable.

In this configuration, the flow of the first back gas can be made uniform (rectified), so that the flow of the ions flowing into the ionization section is not adversely affected. For this reason, diffusion of ions can be suppressed, and there is an effect that the transmittance and collection rate of ions are further improved.

FIGS. 6A and 6B show another example of the structure of the corona discharge region.

The configuration illustrated in FIG. 6A differs from the embodiment of FIG. 1 only in the shape of the first electrode 2. In addition, the ion drifts A and B are exemplified in the configuration of FIG. 5B.

In this embodiment, the corona discharge region is generated on the inner surface of the cylindrical portion 21 of the needle electrode 1 and the first electrode 2. As described above, this cylindrical portion 21 has
Since the sample fluid is flowing in, the reaction zone is always constant and concentrated as compared with the embodiment of FIG. 1, so that more stable ionization can be performed and the efficiency is also stabilized. This has the effect.

The configuration illustrated in FIG. 6B differs from the embodiment of FIGS. 1 and 6A in the shape of the first electrode 2 and the shape of the terminal plate 22. In addition, the ion drifts A and B are exemplified in the configuration of FIG. 5B.

In this configuration, only a part of the first electrode 2 on the surface side in the direction of the needle electrode 1 is exposed, and the other area is covered by the terminal plate 22. Therefore, a corona discharge region is generated only between the exposed surface of the needle electrode 1 and the terminal plate 22. Further, the position is near an opening (exit) from which the sample fluid is jetted, and is a region where the diffusion of the sample is extremely small.

Accordingly, the reaction zone is always constant and concentrated, so that more stable ionization can be performed.
The effect is that the efficiency is further stabilized.

FIGS. 7A to 7D show other examples of the configuration of the differential pumping section.

The differential exhaust configuration illustrated in FIG. 7A minimizes the number of stages in each chamber (2
This is an embodiment of the present invention.

The first pump 210 employs a scroll pump (displacement is about 300-900 l / min).
The second pump 220 shows a case where a turbo-molecular pump (discharge amount is about 200 l / s) is used for exhausting the mass spectrometric unit 80. The back pressure of the turbo molecular pump 220 is shared by the scroll pump 210 by the connecting pipe B76. Further, the flanges are provided with fine holes 52 and 72 for adjusting respective pressures, so that the first chamber 50 and the second chamber 7 can be adjusted.
0 pressure adjustment is possible. The pressure in each chamber, the diameter of each pore, and the position thereof were set in accordance with the above-mentioned index.

In such a configuration, since the ion transmission amounts were the same, it was confirmed that the permeability function was the same. Further, according to this configuration, the pump 210 can be applied even if the pumping capacity is small. Further, material costs can be reduced by the small number of rooms. Therefore, there is an effect that the economy is excellent as compared with the embodiment of FIG.

The differential exhaust configuration illustrated in FIG. 7B is an embodiment in which the exhaust is performed by an independent exhaust pump for each chamber as compared with the embodiment of FIG. 7A. As shown in the drawing, the first chamber 50 is connected to the connecting pipe 77 via the connecting pipe 77.
, The second chamber 70 is evacuated from the pump 210 via the connecting pipe 76, and the mass spectrometer 80 is
The air is exhausted to zero. Further, each of the chambers is newly provided with connection pipes 741 and 742 so that the pressure can be externally adjusted. These connecting pipes include a flow meter 3
01, 305 and variable valves 301, 304 are provided.

The first feature of this configuration is that the second chamber 7
0 means that the pressure of the differential pumping section can be set with a pump having a capacity at least equal to or less than the pumping capacity of the pump applied to the first chamber 50.

That is, as in the embodiment shown in FIG. 1, a pump having a relatively large pumping capacity is generally expensive in proportion to its capacity, so that the cost is generally high. However, even if the exhaust capacity is small, it suggests the possibility of applying a relatively inexpensive rotary pump or the like that matches the pressure of each chamber. Therefore, even if the number of pumps is increased, if the cost does not increase, there is an effect that the function is the same and the economy is more excellent.

The second feature of this configuration is that the connecting pipe 7
With the provision of 41 and 742, it is possible to easily and individually adjust the pressure of each of the differential chambers from the outside. That is, if the pressure in the mass chamber 80 fluctuates for some reason and its output changes, the pressure in each chamber of the differential chamber also fluctuates. For this reason, stable measurement cannot be continued. At this time, by adjusting the pressure of the differential chamber,
It would be advantageous to be able to recover quickly. Even in such a case, in this embodiment, this operation can be easily realized from outside. Further, although not shown, if the connecting pipe is provided with a pressure gauge, an automatic variable valve linked to the indicated value of the pressure is provided, and the pressure of each internal chamber is controlled, the labor can be further reduced.

As described above, in such a configuration, there is an effect that, as compared with FIG.

The differential exhaust configuration illustrated in FIG. 7C is an embodiment in which only the shape of the pore diameter portion of each pore flange of each chamber is different from the embodiment of FIG.

In such a configuration, the tip of each pore provided in each chamber is a knife edge (the wall thickness is almost zero).
Of the shape. In this shape, each electric field concentrates at the tip, and the ions converge more. In addition, even when positional deviation due to eccentricity occurs during assembly of each of the pore flanges, the possibility that ions come into contact with the wall surface of each of the pores is reduced.

Therefore, in such a configuration, there is an effect that the ion transmission amount is further increased and the sensitivity is improved as compared with FIG.

The differential exhaust configuration illustrated in FIG. 7D is an embodiment in which the pore flanges of the respective chambers are formed as a unit as compared with the embodiment of FIG.

In such a configuration, the pressure in each chamber is adjusted according to the exhaust capacity to be applied by the pumps 210 and 220 and the pore diameter 51 of the first chamber and the hole 741 provided in the member 741.
1, 7412, 7413, the third pore 71, and the pore diameter of each pore are determined according to the above-mentioned index. The voltage at each flange is applied via hermetic seal terminals 134.

Accordingly, in this configuration, the differential exhaust unit can be handled as a unitized unit as compared with FIG. 1, so that the size can be reduced and the maintenance and assembling properties are excellent. For this reason, there is an effect that the economy is further enhanced.

Next, the mass spectrometer using the mass spectrometer from the ion source in the present invention can be directly connected to an incinerator or the like to continuously monitor exhaust gas components from the incinerator or the like. is there. In particular, if dioxins discharged from the incinerator and chlorobenzenes, chlorophenols, and hydrocarbons that are precursors of the dioxins are measured and the combustion state of the incinerator is controlled based on the results, dioxin from the incinerator can be measured. It is possible to greatly reduce the amount of generated species.

FIG. 8 is a block diagram showing an application example of the present invention to an online monitor analyzer for gas measurement for automatically analyzing chlorobenzenes, chlorophenols, and hydrocarbons in exhaust gas.

This analyzer is composed of the following components. That is, a collection pipe 1000 that directly samples the exhaust gas to be measured from a pipe or a chimney of a plant,
A filter 1004 for removing dust, oil, mist, and hydrogen chloride in the collected exhaust gas, and a sample connection pipe 400 provided separately from an apparatus main body for introducing the collected exhaust gas to the mass spectrometer main body; A first sample transport pipe 1001 is connected to the main body of the apparatus, and at one end of the first sample transport pipe 1001, branches to a sample connection pipe 400 for taking an exhaust gas sample into the apparatus, and dioxins having a predetermined flow rate Exhaust gas containing chlorophenols and chlorobenzenes into the main body of the apparatus,
3 is connected to the sample introduction tube 34.

The gas molecules ionized by the ion source and the unreacted gas are discharged through the second discharge pipe 36 of the sample introduction flange 33 and the first discharge pipe 16 of the ionization flange 15 to the discharge pipe 1005. Is discharged from The discharged gas is returned to the second sample transport pipe 1003.

Further, this gas is supplied to the sample transport tube 100.
1, a suction pump 10 provided in the 1003 system (piping)
02, and further sent out by an exhaust fan 1006 located downstream of the suction pump.
A piping system is configured to discharge the exhaust gas to a pipe or a chimney of a plant via a discharge pipe 1007.

Further, one end of the sample connection pipe 400 is connected upstream of the second sample transport pipe 1003, and a differential pressure generator (throttle mechanism) 1008 is provided downstream thereof, and the discharge pipe is provided downstream thereof. 1005 are connected. The flow rate of the sample connection pipe 400 is set based on the amount of differential pressure generated by the differential pressure generator 1008.

A pump 1009 is provided upstream of the back gas connection pipes 300 and 303, and a filter 1004 for sucking air and removing mist is provided downstream thereof.
And is supplied as a back gas to the ion source and the ion drift B.

The measuring / analyzing section corresponds to a mass spectrometer using the ion section and differential pumping section of the present invention.

The piping system (1001 to 1007, 10
The flow path constituted by 08) serves to send the collected sample gas to the monitor at a constant flow rate stably, without loss due to adsorption or condensation of the substance to be measured, and the like. For this purpose, the entire sampling section should be between 100 ° C and 3 ° C.
It is heated to about 00 ° C.

The monitor section selectively and efficiently ionizes the substance to be measured in the fed sample gas, and mass-analyzes the generated ions by the mass spectrometry section.
The object to be measured is continuously detected.

The amount of the target substance can be determined from the ion current value at the mass number derived from the object to be measured, and the relationship (calibration curve) between the amount of the standard substance prepared in advance and the ion current value. For example, in the case of 2,3-dichlorophenol (molecular weight 162, observed ion mass number 161), a change in ion intensity with respect to the concentration of the sample gas is measured, and a calibration curve is created. From this calibration curve and the observed ion intensity, the concentration data of the sample gas at that time is estimated. The data obtained is further organized and continuously displayed and stored with the concentrations of the components and other parameters.
Alternatively, the data is sent to the combustion control device as data for controlling combustion in the refuse incineration plant.

In order to estimate the dioxin concentration from the concentrations of chlorobenzene and chlorophenols, the concentration is estimated by using a previously determined correlation between the two.

When an ion trap mass spectrometer is used, higher selectivity can be obtained as compared with a normal mass spectrum. This is an MS / MS method in which energy is injected into molecular ions trapped inside the ion trap mass spectrometer, and the molecular ions are dissociated by collision with buffer gas (such as He) molecules in the electrode. For organic chloride compounds,
An ion from which one or two chlorine atoms are eliminated from the molecular ion is observed by the MS / MS method. For example, in the case of 2,4-dichlorophenol, when ionization is performed using negative corona discharge, negative ions (MH) ⁻ and (M: molecule, H: hydrogen) are generated. When this negative ion is dissociated by the MS / MS method, a negative ion from which one chlorine atom has been eliminated is generated. Observing this negative ion can provide very high selectivity. By quantifying the amount of negative ions from which one chlorine atom has been eliminated from the peak intensity, the amount of dichlorophenol in the exhaust gas can be estimated. This measurement process is repeated when there are a plurality of molecular species to be measured.

While the above description has been made mainly on the case where the atmospheric pressure chemical ionization method in the negative ionization mode is used,
The exhaust gas contains various components. For this reason, for the hydrocarbon-based compounds of aromatic compounds represented by benzene and the like and the compounds having a small number of chlorines, this apparatus is used.
Continuous measurement in positive ionization mode is also possible. For example,
In benzene and monochlorobenzene, M ⁺ ion species are generated by the positive pressure ionization mode atmospheric pressure chemical ionization method.

Therefore, in actual sample gas measurement, it is also effective to increase the amount of information in the sample gas by alternately measuring the positive and negative ionization modes.

FIGS. 9 (a) and 9 (b) show examples of characteristic confirmation results of the present apparatus alone. The measurement conditions were as follows: dichlorophenol (concentration: 5
μg / Nm ³ ) was mixed with air, and the concentration was changed by changing the mixing ratio. At this time, the flow rate was 1 l / min, the corona discharge current of the needle electrode was 5 to 10 μA, the ion uptake time was 0.1 second, and the temperature was 150 ° C.
In the figure, the vertical axis indicates the relative ionic strength normalized by the ionic strength.

FIG. 9A shows the change in the density. As can be seen from the figure, the resolution was about 0.1 μg / Nm ³ , the linearity was 2 to 5% or less, and a good linear relationship was obtained.

FIG. 9B shows an output example of a mass spectrum. The measurement conditions were the same as above, except that trichlorophenol and tetrachlorophenol were added in addition to dichlorophenol as a sample. In the figure, the vertical axis indicates the relative ionic strength normalized by the ionic strength.

As shown in the figure, dichlorophenol (D
It can be seen that the peaks of the mass spectra of CP), trichlorophenol (TCP) and tetrachlorophenol (TeCP) are clearly analyzed. Furthermore, the spectra of oxygen and nitrogen in the air, which is the medium of the sample, were also observed, and an extremely good mass spectrum was obtained.

The configuration of the ion source section illustrated in FIG. 10 is an embodiment in which the sample is provided with a large number of ionization / reaction regions by the corona discharge as compared with the embodiment of FIG.

The sample introduced through the sample connection pipe 400 is applied to the sample introduction pipe 3 provided on the sample introduction flange 33.
4 and is introduced into the sample introduction flange 33.
The introduced sample gas flows in the sample flange 33 and the pores 21 (a, a) of the many first electrodes (a, b, c, d, e) 2.
b, c, d, and e) (1/1 in the figure)
5).

The separated sample gas is supplied to the needle electrodes 1 (a, b, c, d, e) provided for each of the pores 21 of each electrode.
In the meantime, as described above, corona discharge is generated, and the introduced sample gas is ionized. The rest is the sample introduction flange 3
3 are discharged from the first discharge pipes 6a and 6b.

The sample to be introduced into each ionization chamber 10 is filled with the pores 21 (a) of a large number of first electrodes (a, b, c, d, e) 2 provided on one surface of the sample introduction flange 33. , B,
c, d, and e) are separated and flow out, and each streamline is not diffused by each of the pores 21. The sample including the detector is ionized in a corona discharge region generated between each first electrode 2 and each needle electrode 1 to which a high voltage is applied. This part corresponds to the ionization part shown in FIG. The needle electrode 1
The voltage applied to (a, b, c, d, e) is about 1 to 6 kV when generating positive ions and about -1 to -6 kV when generating negative ions. 11
It is supplied from 0 by a constant voltage or constant current method.

The generated ions overcome the flow due to the electric field generated between each first electrode 2 and the needle electrode 1 to which a high voltage is applied, and the ions are extracted to the outlet of each electrode.
Further, as described above, in order to secure the stability and durability of the corona discharge, a means for separately supplying a pure gas such as dry air or argon to the ionization section where the needle electrodes 1 are located is provided. And is similar to the configuration of FIG.

The molecules of the ionized detector, oxygen, HCL, and the like pass through the pores 21 and flow into the sample introduction flange 33 in the pore diameter region of the pores 21.

The ions are supplied to the sample introduction flange 33.
Are arranged on the other surface side (opposite surface of the pores 21), and a number of pores 31 are arranged coaxially with the pores of the first electrodes 2.
A second electrode 3 having (a, b, c, d, e) is provided, and a potential difference is generated between each pore 21 of each first electrode 2 and each pore of the second electrode 3. The ions are accelerated by the potential difference and converge. That is, each pore of each first electrode 2 and each pore provided in the second electrode 3 are arranged in parallel, and the potential is applied only to the shape of the pore through which the ions of each pore 31 pass. The convergence is achieved by a shape that is not concentrated, for example, an acute angle (31a in FIG. 2) or an end face thereof is positively formed into a convex portion. Subsequent drift of ions is omitted because high transmittance can be ensured as described above.

In this configuration, the amount of ionization of the sample gas is greatly increased as compared with the configuration in FIG. 1, so that there is an effect that gas analysis with extremely high sensitivity becomes possible.

Next, in the configuration examples of the ion source section and the differential exhaust section illustrated in FIGS. 1 to 7A to 7D, although not shown, between the illustrated chambers or the connection of the members, the illustration is omitted. At least one sealing means is provided to ensure sealing and isolation. In the present invention, each configuration for analyzing the exhaust gas with high sensitivity has been exemplified. However, in the case of the exhaust gas, the exhaust gas needs to be treated at a high temperature as compared with the general analysis. The most feared items in the case of processing at this high temperature are the gas output from the constituent members and the gas output from the sealing means. If the generation amount is large, the background rises, and in many cases, a predetermined sensitivity cannot be secured. By performing a pretreatment such as a heat treatment on the constituent members, the outgassing thereof can be suppressed.

However, since the sealing means generally uses a flexible organic elastomer O-ring, there is no fear of assembling or maintenance, but a large amount of gas is generated. There is a problem. On the other hand, there is also a metal type O-ring, but it is expensive and the tightening force is large, so it is assumed that the misalignment at the time of assembly becomes large and the required sensitivity cannot be secured, and the work at the time of maintenance is not labor-saving. Not a good idea.

For this reason, the present invention employs sealing means having a structure as shown in FIG. That is, a double structure, the inside of which uses a sealing material which is a flexible member such as the O-ring, and in the case where the inside is negative pressure, a thin metal plate such as aluminum or the like, which is rich in plastic deformation toward the low pressure side on the outside. If you cover with a cover material such as copper and the inside is positive pressure,
It has a double configuration in which the metal cover is inserted inside.

With this configuration, by tightening the members A and B with the tightening bolts, the sealing member, which is the inner member, is sufficiently deformed even with a low tightening force. Since a material capable of large deformation and excellent in plastic flow are applied, the cover material, which is the outer metal, also undergoes large deformation, so that a large contact area, that is, a large contact portion can be secured. For this reason, there is an effect that the outgassing can be greatly reduced without deteriorating the sealing property and the exposed surface is a metal body, and the background is not reduced.

This embodiment is different from the embodiment shown in FIG. 1 in that the sample is provided with a large number of ionization and reaction zones by the corona discharge. This background can be further reduced by improving the performance of the gas purifying device, or by performing electrolytic polishing or passivation on the inside of the ion source and the inner surface of the gas introduction pipe. As described above, this monitor enables continuous and direct grasp of how many dioxins are contained in the exhaust gas from incinerators and the like, and how much there is fluctuation.Furthermore, the exhaust gas component can be detected with high sensitivity and in real time. Measurement and analysis, and the concentration of dioxins and other gas components in the incinerator can be measured.

[0235]

According to the present invention, dioxins, chlorophenols and chlorobenzenes can be continuously collected directly from the flue, and can be monitored continuously.

In addition, according to the present invention, an inhibitory gas that affects the measured substances of dioxins, chlorophenols and chlorobenzenes, and an inhibitory gas such as hydrogen chloride that affects the operation time of the apparatus are supplied to the mass spectrometer. Intrusion prevention and stabilization of corona discharge in the ionization region can be achieved.

Therefore, there is an effect that the detection accuracy of dioxins, chlorophenols and chlorobenzenes is high and stable analytical values can be continuously obtained. Also,
The continuous operation time can be extended,
There is an effect that the maintainability is excellent.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of an ion source, a differential exhaust, and a mass spectrometer in the present invention.

FIG. 2 is a diagram showing a configuration example of an ion source in detail.

FIG. 3 is a diagram showing an example of the configuration of a differential exhaust unit in detail.

FIG. 4A is a diagram showing another configuration example (1) of the ionization unit.

FIG. 4B is a diagram showing another configuration example (2) of the ionization unit.

FIG. 4C is a diagram showing another configuration example (3) of the ionization unit.

FIG. 4D is a diagram showing another configuration example (4) of the ionization unit.

FIG. 5A is a diagram showing another configuration example (1) of the ion source unit.

FIG. 5B is a diagram showing another configuration example (2) of the ion source unit.

FIG. 5C is a diagram showing another configuration example (3) of the ion source unit.

FIG. 5D is a diagram showing another configuration example (4) of the ion source unit.

FIG. 5E is a diagram showing another configuration example (5) of the ion source unit.

FIG. 5F is a diagram showing another configuration example (6) of the ion source unit.

FIG. 6 is a diagram showing another configuration example of the ionization / ion source unit.

FIG. 7A is a diagram showing another configuration example (1) of the differential exhaust unit.

FIG. 7B is a diagram showing another configuration example (2) of the differential exhaust unit.

FIG. 7C is a diagram showing another configuration example (3) of the differential exhaust unit.

FIG. 7D is a diagram showing another configuration example (4) of the differential exhaust unit.

FIG. 8 is a diagram showing a measurement path and configuration of exhaust gas.

FIG. 9 is a diagram showing an example of characteristics of the device.

FIG. 10 is a diagram illustrating a configuration example of a multi-ion source unit.

FIG. 11 is a diagram showing a configuration example of a sealing unit.

[Explanation of symbols]

1: needle electrode, 2: first electrode, 3: second electrode, 4: first pore first flange, 5: second pore flange, 6: third pore flange, 7: fourth pore flange , 10: ionization room,
11: Needle holder, 12: Back gas supply pipe, 13: H
V terminal, 14: needle fixing bracket, 15: ionized flange,
16: first discharge pipe, 17: heater, 20: ion drift A portion, 21: first electrode pore, 22: terminal plate, 30:
Ion drift B part, 31: pore in second electrode, 32: terminal plate, 33: sample introduction flange, 34: sample introduction, 3
5: heater, 36: second discharge pipe, 37: mesh, 4
1: first pore, 42: spacer, 43: second flange second flange, 44: back gas supply pipe, 50: first chamber, 5
1: second pore, 52: side hole 2, 60: second chamber, 6
1: third pore, 62: side hole 3, 70: third chamber, 7
1: fourth pore, 72: side hole 4, 73: heater, 7
4: connecting pipe for differential exhaust unit, 76: connecting pipe B, 80: mass spectrometer, 81, 82, 83: converging lens, 84: lens electrode, 86: inner cylinder electrode, 85: outer cylinder electrode, 91a: gate Electrode, 91b: ion extraction lens, 92: end cap electrode, 93: insulating ring, 94: ring electrode, 1
01: ion converter, 105: cylinder, 104: back gas connection pipe, 103: third back gas supply pipe, 110:
Analysis unit housing, 111: HV power supply line, 120: drift power supply 1, 121, 122: power supply line, 130: second drift power supply, 134: hermetic seal terminal, 200: ion detector, 210: first pump, 220 : 2nd pump,
300: back gas connection pipe, 301: variable throttle device, 3
02: flow meter, 400: sample connection tube, 401: variable aperture device, 402: flow meter, 411: member, 4
14: inflow path, 415: gap, 416: member, 921:
Spit electrode, 1000: collection tube, 1001: first sample transport tube, 1002: suction pump, 1003: second sample transport tube, 1004: filter, 1005: discharge tube, 100
6: exhaust fan, 1007: exhaust gas exhaust pipe, 1008:
Differential pressure generator (throttle mechanism), 1009: pump.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01N 27/62 ZAB H01J 49/04 H01J 49/04 49/10 49/10 G01N 1/28 T (72) Inventor Koji Tachibana 882 Ma, Hitachinaka-shi, Ibaraki Pref. Hitachi, Ltd. Instrument group (72) Inventor Hiroaki Hashimoto 882 Mo, Hitachinaka-shi, Ibaraki pref. F-term in Hitachi measuring instrument group (reference) 5C038 EE01 GG08 GH04 GH08 GH11 GH13 HH02 HH03 HH16 HH30 JJ02

Claims (30)

[Claims] 1. An exhaust gas measuring apparatus comprising: means for introducing a sample gas; ionizing means for ionizing the sample gas under substantially atmospheric pressure; and a mass spectrometer for analyzing components in the ionized sample gas. In the online monitor, the ionization means has at least one ionization chamber on one surface side of the sample gas introduction means, and the other surface side of the sample gas introduction means, In order to make the ionized sample gas incident on the mass spectrometer arranged in the high vacuum region, the first stage of the differential pumping section consisting of a multistage low vacuum chamber configured in a stepwise manner is arranged, and the final stage of the differential pumping section. An on-line monitoring device for gas measurement, wherein the mass spectrometer in a high vacuum region is arranged in a section. 2. The apparatus according to claim 1, wherein said ionization means ionizes said sample gas using corona discharge generated by applying a high voltage to a needle-like electrode.
The online monitoring device for gas measurement according to the above. 3. The sample gas is prevented from being mixed between the means for introducing the sample gas and the first stage of the differential pumping section which transmits and transports the ionized sample gas to the mass spectrometer. 2. The online monitoring device for gas measurement according to claim 1, further comprising a space, wherein a gas having a known component is introduced into the space, and the gas is constantly replaced. 4. An on-line monitoring apparatus for gas measurement according to claim 1, wherein said differential pumping section comprises at least two low vacuum chambers. 5. A means for introducing the sample gas, an ionizing means for ionizing the sample gas on one surface of the means for introducing the sample gas, and another surface of the means for introducing the sample gas. The differential exhaust unit composed of a relatively low vacuum chamber configured in a stepwise manner for entering the mass spectrometer arranged in a high vacuum region with the ionized sample gas, and the high vacuum mass spectrometer are coaxial. The on-line monitoring device for gas measurement according to claim 1, wherein the on-line monitoring device is arranged above. 6. An on-line monitoring apparatus for gas measurement according to claim 2, wherein said ionization means comprises means for supplying a gas having a known component to the tip of said needle-shaped electrode. . 7. The method according to claim 1, wherein the ionization means comprises:
3. The online monitoring device for gas measurement according to claim 2, wherein the online monitoring device is made of any one of stainless steel, copper, platinum, and platinum-iridium. 8. The ionization means protects the needle-shaped electrode with a member different from the needle-shaped electrode member, and the component is known in advance in a gap between the member and the needle-shaped electrode. The on-line monitoring device for gas measurement according to claim 2, wherein the gas is supplied. 9. The ionization means is provided with a throttle or notch for concentrating and supplying the flow rate of the gas whose component is known in advance to the tip of the needle-shaped electrode. The online monitoring device for gas measurement according to claim 8. 10. The ionization means uses a tubular member as the needle-like electrode member, sharpens the tip end,
The on-line monitoring device for gas measurement according to claim 2, wherein the corona discharge is generated at the tip. 11. The ionization means includes a fixing member for fixing the needle-shaped electrode member, and at least one means for supplying a pure gas having a known component to the fixing member side. The on-line monitoring device for gas measurement according to claim 2, wherein the needle-shaped electrode member is made of any one of stainless steel, copper, platinum, and platinum-iridium. 12. Preventing the sample gas from being mixed between the means for introducing the sample gas and the first stage of the differential pumping section which transmits and transports the ionized sample gas to the mass spectrometer. 2. A space is provided, wherein a gas having a known component is flowed into the space, and the space is constantly replaced, and the space is made to have the same potential. Online monitoring device for gas measurement. 13. An on-line monitoring apparatus for gas measurement according to claim 12, further comprising means for rectifying the flow of the gas whose components are known in advance in said space. 14. A mixture of the sample gas is prevented between the means for introducing the sample gas and the first stage of the differential pumping section which transmits and transports the ionized sample gas to the mass spectrometer. A means for introducing a gas having a known component into the space and constantly replacing the space, and at least one member for insulating the space, and introducing the sample gas into the space. The on-line monitoring device for gas measurement according to claim 1, wherein a potential difference is generated between a surface on the side of the differential exhaust unit and a surface on the side of the differential exhaust unit. 15. An on-line monitoring apparatus for gas measurement according to claim 14, further comprising means for rectifying the flow of the gas whose components are known in advance in said space. 16. A member provided on a surface of the space on the side of the means for introducing the sample gas, and a member provided on a surface of the space on the side of the corona discharge of the means for introducing the sample gas, 15. The online monitoring device for gas measurement according to claim 14, wherein another potential difference is provided, and equipotential lines generated between both members are made parallel. 17. A member provided on the surface of the corona discharge side of the means for introducing the sample gas is disposed obliquely in the corona discharge area, and the sample gas is supplied to the member for generating the corona discharge. 17. The on-line monitoring apparatus for gas measurement according to claim 16, further comprising at least one outflow means for causing the corona discharge to flow out to a tip end side of the member. 18. An on-line monitoring apparatus for gas measurement according to claim 3, wherein said gas having a known component is supplied via a member at a first stage of said differential exhaust unit. 19. The apparatus according to claim 19, further comprising: a means for supplying a new gas for diluting the concentration of the corrosive gas in the sample gas between the means for introducing the sample gas and the first stage of the differential pumping section. 2. The online monitoring device for gas measurement according to claim 1, wherein the online monitoring device is provided in a means for introducing gas. 20. A corrosive gas in the sample gas between a means for introducing the sample gas and a first stage of the differential pumping section which transmits and transports the ionized sample gas to the mass spectrometer. Means for supplying a new gas for diluting the concentration of the sample gas is provided in the means for introducing the sample gas, and a mixed gas of the new gas and the sample gas is supplied to a first stage of the differential pumping section. 2. The online monitoring device for gas measurement according to claim 1, further comprising a hole or a cutout communicating with a means for introducing the sample gas at a first stage of the differential pumping section for taking in the sample gas. 21. A space for preventing the sample gas from being mixed between the means for introducing the sample gas and the first stage of the differential pumping section which transmits and transports the ionized sample to the mass spectrometer. A gas having a component known in advance is introduced into the space, and the gas is constantly replaced, and the gas is supplied through a member at a first stage of the differential exhaust unit. The online monitoring device for gas measurement according to claim 1, wherein 22. The online monitoring device for gas measurement according to claim 21, wherein the front end of the first stage of the differential exhaust section is formed to have an acute angle. 23. The low vacuum chamber formed between the first stage and the last stage of the differential pumping section, wherein the tip of the ion passage hole is formed to be acute. Online monitoring device for gas measurement. 24. Each of the low vacuum chambers formed between the first stage and the last stage of the differential exhaust section is independently evacuated by an exhaust pump corresponding to each chamber. Claim 1
The online monitoring device for gas measurement according to the above. 25. Each of the low vacuum chambers formed between the first stage and the last stage of the differential pumping section is evacuated by an exhaust pump to a predetermined pressure, and the pressure of each chamber is reduced. 2. An on-line monitoring apparatus for gas measurement according to claim 1, wherein said chambers are provided with means which can be adjusted from outside. 26. Each of the low vacuum chambers formed between the first stage and the last stage of the differential pumping section is constituted by a unitized member, and each of the unitized members has a pressure adjusting member. 2. An on-line monitoring apparatus for gas measurement according to claim 1, wherein said differential pressure section is constituted by providing a hole for each chamber and incorporating said unit as one pressure chamber. . 27. Means for introducing exhaust gas as a sample sample, and a plurality of ionization chambers provided on one surface side of the sample sample introduction means for ionizing the sample sample under atmospheric pressure. An ionization means, comprising a mass spectrometer for analyzing components in the ionized sample sample, and on the other surface side of the means for introducing the sample sample, the ionized sample sample In order to enter the mass spectrometer in a high vacuum region, a first stage of a differential pumping unit consisting of a relatively low vacuum chamber configured in a stepwise manner is arranged, and the mass spectrometer is disposed at a final stage of the differential pumping unit. An on-line monitoring device for gas measurement, comprising: 28. The apparatus according to claim 28, further comprising: means for introducing the sample sample; and a first stage of an interface of the differential pumping section for transmitting or transporting the ionized sample sample to the high vacuum mass spectrometer. 28. The online monitor for gas measurement according to claim 27, further comprising a space for preventing mixing, wherein a gas having a known component is introduced into the space, and the gas is constantly replaced. apparatus. 29. The apparatus according to claim 29, wherein the ionization means is independently ionized for each sample sample which flows into each of the ionization chambers by using corona discharge generated by applying a high voltage. The online monitoring device for gas measurement according to claim 27, wherein 30. A means for introducing a sample gas, and at least one ionization means provided before the means for introducing the sample gas and ionizing the sample gas under substantially atmospheric pressure.
A differential exhaust unit, which is provided at a stage subsequent to the means for introducing the sample gas and comprises a multi-stage vacuum chamber whose pressure is reduced stepwise, and introduces ions of the sample gas that has passed through the differential exhaust unit to A mass spectrometer for analyzing the components of the sample gas; and, between the means for introducing the sample gas and the differential exhaust unit, the sample gas is supplied to the differential exhaust unit. An on-line monitoring apparatus for gas measurement, wherein a space for preventing mixing is provided, and a gas having a known component is introduced into the space, and the gas is constantly replaced.