JPS63300956A - Analyzer directly coupled to gas chromatograph mass spectrometer - Google Patents

Abstract

PURPOSE:To improve the efficiency of capturing a sample component to a mass spectrometer by attaching an ionization mechanism which can ionize only the sample component to a separator so that electric charge is applied on the sample component. CONSTITUTION:The sample injected into gas chromatograph is separated by a sepn. column 3 and flows together with a carrier gas He to a carrier gas removing section. The sample can then be introduced into the mass spectrometer with high efficiency by the fluid dynamical division system of capillary tubes 17, 18 in the carrier gas removing section and the effect of the electric field by the ionization. The sample component introduced therein is ionized by receiving the UV light of a light source 37 in an ionization chamber 16 and the ions flow into the mass spectrometric section 12 where the ions are detected by an electron multiplier 13 and are recorded in a recording section. A high vacuum state is maintained at all times in the chamber 16 and the section 12 by rotary oil diffusion pumps 8-10 and a rotary vacuum pump 11. The sample component is thus ionized and the charge is provided on the ions, by which the selective introduction of only the sample component by the electrical effect into the mass spectrometer is enabled.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is an analytical device for analyzing the structure or clarifying the physical properties of organic compounds, which has been developed as a conventional analytical device. By combining the two, it is possible to compensate for the deficiencies of each device, and at the same time, make the best use of the characteristics of each individual analyzer.

[Conventional technology]

Naturally, the performance of GC-MS depends on the performance of each GC and MS device.

This is often due to the performance of the carrier gas separator used at the connection point between the GC and MS.

The basic principles of GC are described in the explanatory book Latest Gas Chromatography (Basics and Applications, edited by Watari Funasaka and Nobuo Ikeyo), and here we will only touch on the setting conditions when 6C is generally used.

GC consists of a sample injection section 9, a separation column, and a mobile phase (carrier gas).While the injected sample passes through the separation column together with the carrier gas, each component in the sample is separated, and each component is separated. This is an analyzer that generates an electrical signal proportional to the concentration of Therefore, the carrier gas flow is typically operated at a pressure that is always above atmospheric pressure.

On the other hand, the basic principles of a mass spectrometer (MS) are described in detail in the "Mass Spectrometers Edition" in the Experimental Chemistry Course edited by the Chemical Society of Japan.

Here I will only give an overview and describe only the main points of MS.

From a functional concept, MS consists of three functions: ionization, mass separation, and detection/recording. That is, a molecule with a mass m generates a charge e by ionization,
It is accelerated by the given accelerating voltage V, and at the speed V, the formula (
Obtain the kinetic energy eV shown in 1).

This ionized molecule has a magnetic velocity density B and a circular orbit radius r
When guided between the magnetic poles of the ion, the ion receives a force Beυ and flies in a circular orbit. This force is equal to mυZ/r. That is, m u ”/r = Rev −
-(2) The important equation (3) is obtained from equations (1) and (2).

e 2V The relational expression (3) shows the principle of MS. That is, when the ion accelerating voltage is kept constant and the magnetic velocity density is continuously changed, ions of m/e corresponding to B at that time can be detected one after another, and a mass spectrum can be obtained. Conversely, when the magnetic velocity density B is kept constant and the accelerating voltage (2) is continuously varied, a mass spectrum can be similarly obtained. In MS based on this principle, it is necessary to create a high vacuum so that collisions between ions do not occur while the ions pass between the magnetic poles from the ion source for ion generation and acceleration. Although the degree of vacuum required for an MS varies depending on the purpose of measurement, a degree of vacuum of 110-7 aiH or more is often required for the analysis tube section under measurement conditions.

By the way, in order to connect GC, which requires operation under atmospheric pressure, and MS, which requires operation under high vacuum, the carrier gas used in GC must be removed, and the concentration of the sample component to be measured must be as high as possible. It is necessary to introduce the gas into the MS in the same state and maintain a high degree of vacuum in the MS.

Therefore, in the prior art, a carrier gas removal section indicated by reference numeral 6 in FIG. 6 is provided. The carrier gas removing section is provided with hollow capillary tubes (tubes 17 and 18 in FIG. 6), and the carrier gas flowing out from the GC is further evacuated by a vacuum pump shown in No. 7 of the 6th cylinder. method is adopted. The separation mechanism between the sample component and the carrier gas in this carrier gas removal section utilizes the difference in kinetic energy (mυ2/2) resulting from the difference in mass. In other words, the carrier gas used in GC is helium (He), which is inert and has a small mass, while the sample components are often organic compounds, which have a much larger mass than He. The amount introduced into the sample component is stochastically large. The kinetic energy given to the carrier gas and sample components is determined by the flow rate determined by the set pressure of the carrier gas, and the ratio of the amount of sample components introduced into the MS to the amount of carrier gas is determined by the mass m of the sample components and the mass of the carrier gas He. It is concerned only with the ratio to m2.

Ionization of a sample in MS is performed by accelerating thermal electrons with a voltage and causing them to collide with sample molecules.

On the other hand, an infrared absorption spectrophotometer (IR) is a type of analyzer for obtaining information reflecting the chemical structure of a compound.

Although some positions of absorption bands in infrared absorption spectra are determined theoretically, most of the positions are determined empirically by comparing the absorption spectra of a large number of similar compounds.

In conventional technology, it is commonly used as an analyzer called a gas chromatograph-infrared spectrophotometer (hereinafter abbreviated as GC-IR), which directly connects a gas chromatograph (GC) and an infrared absorption spectrophotometer (hereinafter abbreviated as IR). has been made into This GC-
The role of an IR analyzer is to continuously separate a multi-component sample into single components using GC, flow the separated components into the IR, and obtain the infrared absorption spectrum of the separated single components. Attribution of the compound is performed based on the obtained information on the chemical structure of the compound. Therefore, it is a type of complex analyzer that is indispensable as a means of identifying unknown substances. However, G
Gas chromatograph-infrared absorption spectrophotometer-mass spectrometer (hereinafter referred to as GC-I) directly connected to C, IR, and MS analyzers.
A composite analyzer to be called R-MS (abbreviated as R-MS) has not yet been realized.

[Problem that the invention seeks to solve]

1) In conventional GC-MS, the amount of sample injected into the MS has been controlled by dividing the carrier gas and sample components using only the action of hydrodynamic kinetic energy. With the above method alone, the sample components flowing out from the GC can be efficiently
There is a limit to how much it can be introduced into S, and MS information cannot be obtained from samples with a small amount of components.

2) In addition, in conventional GC-MS, when the GC alone is sufficient, the MS is activated and the MS is used as a GC detector.
However, the present invention has a function that can be used independently as a GC.

3) In conventional MS, the method of ionizing sample molecules is to accelerate thermionic electrons using a voltage and collide them with the sample molecules to ionize them. In some cases, the number of fragment ions increases and no molecular ions are generated.

Specific examples in which parent ions are not generated are often observed in ester compounds.

4) GC-MS separates a multi-component sample into individual components, and it has become possible to determine the mass of pure substances from mixtures, as well as the elemental composition and partial molecular structure of molecules using recent advanced information processing methods. However, verification with reference substances is required, and there are limits to attributing unknown substances using GC-MS alone, and information that reflects the chemical structure is required.

The present invention was made by focusing on the above-mentioned problems of GC-MS. It adds new functions to the conventional technology, improves both the quality and quantity of basic physical and chemical information about substances, and The aim was to further ensure the attribution of substances.

[Means for solving problems]

In GC-MS, sample components flowing out from GC are analyzed by MS.
In order to introduce the sample with high efficiency, in the same way as using the hydrodynamic kinetic energy of molecules in the conventional method, only the sample components are ionized and charged, and an accelerating voltage V is applied to them to ionize them. This can be achieved by accelerating molecules by applying kinetic energy eV to them.

Furthermore, by applying an electrode to the introduction part of the MS and collecting ionized molecules, it is possible to grasp the amount of ion molecules introduced into the MS. This is also possible without activating MS.
It acts as a detector for the effluent components of C and can be used independently by GC.

The main purpose of MS is to measure the molecular weight of components, so if a parent peak is not obtained, the molecular weight cannot be determined. In order to prevent this, the sample molecules were ionized using a photoionization method, and an MS ionization chamber was used to mainly obtain parent ions. There are limitations to the identification of unknown substances using GC-MS, so by newly combining IR, we confirmed the attribution of unknown substances.

[Effect]

In GC-MS, the separation mechanism of the carrier gas and sample components according to the present invention uses the difference in kinetic energy depending on the flow rate of the carrier gas determined by the GC pressure setting, and selects sample components by ionizing only the sample components and applying an electric field. M
Introduce it to S. Ionization potential of organic compounds (
The work function) is around 10 eV, while the ionization potential of helium He, which is a carrier gas, is 24 eV. Therefore, it is possible to ionize only organic compounds by irradiating ultraviolet light with an energy of about 10 eV. Furthermore, by measuring the ion current of this ionized molecule, it can be operated as a GC detector.

On the other hand, in conventional MS, thermionic electrons of 20aV to 70eV are used to ionize the sample in the ionization chamber.
Even if it is set to 20 eV, the energy width is large, molecules are destroyed, and it is difficult to generate a parent peak.

To avoid this, an ultraviolet lamp was installed in the ionization chamber, and the ionization potential of the molecule was irradiated with light in the vicinity, allowing the parent peak to be obtained.

On the other hand, in GC-MS, infrared absorption spectrum measurement is possible by installing an IR between GC and MS.
This made the attribution of unknown samples more certain.

〔Example〕

The effectiveness of the present invention will be explained in detail below based on examples.

An embodiment based on the present invention is shown in FIG. It combines GC and MS, and is roughly divided into a GC section, a carrier gas removal section, and an MS section.

The GC is the same as a general gas chromatograph, and the temperature of a gas chromatograph constant temperature bath 2 is controlled by a temperature controller 1. The thermostatic chamber 2 is accompanied by a separation column 3 and a sample injection section 4 for separating sample components. The gas supplied from the carrier gas supply tube 5 required for separation contains H.
e was used.

The sample injected into the GC is separated by the column and flows into the carrier gas removal section together with the carrier gas Ha.

This carrier gas removal section is provided with opposing capillary tubes 17 and 18, and this space is evacuated by a rotary vacuum pump 7. Also capillary tube 17.1
8 is provided with electrodes 34 and 35 so that a photoionization detector 30 ionizes the sample flowing in from the GC, and an electrometer 33 can measure an electric signal proportional to the amount of the ionized sample.

The light source used in the photoionization detector is ultraviolet light that can ionize organic compounds, but there are also light sources of about 600 V (20 e V) obtained by He discharge, neon Ne (1
Light sources such as the Lyman line of hydrogen (9,5 eV), Ar (11,5 eV), and hydrogen (9,5 eV) can be used. These organic compounds ionized by the ultraviolet light are introduced into the MS section with high efficiency by the action of the electric field of the electrodes 34 and 35. Unlike the case of conventional hydrodynamic action only, the electrode 34.35
It is also possible to adjust the amount introduced into the MS by adjusting the strength of the electric field.

The mechanism of the carrier gas removal section according to the present invention is as described above, and the sample can be introduced into the MS with high efficiency by the hydrodynamic division method using the capillary tubes 17 and 18 and the action of the electric field due to ionization.

The sample components introduced into the MS section are ionized by the ultraviolet light from the light source 37 in the ionization chamber 16 in FIG. be done. The ionization chamber 16 and the mass spectrometer 12 are constantly maintained in a high vacuum state by rotary oil diffusion pumps 8, 9, and 10 and a rotary vacuum pump 11.

In ionizing the sample component in the ionization chamber 16, it is important to increase the amount of molecular ions (parent ions) produced in order to know the molecular weight of the component. Until now, attempts have been made to generate molecular ions only by thermionic irradiation. However, in the case of compounds in which it is difficult to generate parent ions, such as ester compounds, the energy distribution of thermionic electrons is large, resulting in decomposition of the components, making it difficult to measure the molecular weight. However, by ionizing using an ultraviolet light source with a small energy distribution as in the present invention, it has become possible to detect the group peaks of the majority of ester compounds.

Although the light source is not limited in the present invention, the light source for the ionization chamber may be He, Ne, Ar, or mixed gas H.
E-Ne and Hz-Ne discharge lamp light sources were effective. Of course, a laser light source can also be used. Further, in order to increase the applicability of MS, thermal electron irradiation is also necessary, and it is desirable that the MS be able to select an ionization method depending on the purpose.

In order to continuously separate a multi-component sample and assign components only from the mass spectrum, it is necessary to check the mass spectra of many similar compounds. If an analytical device is available, the time required for attribution will be reduced, and the accuracy of the attribution itself will be increased. From this point of view, the composite analyzer according to the present invention, which can obtain a lot of information from a negative sample, will be described below.

FIG. 3 is a configuration diagram of an analyzer that directly connects GC, IR, and MS. The configuration of the GC and the role of the GC in this analyzer are the same as in FIG. 1, and detailed explanation will be omitted.

In FIG. 3, sample components flowing out of the GC flow into a 41 sample measurement cell, where an infrared absorption spectrum is measured.

The configuration of the infrared absorption spectrum includes an infrared light source 42, a spectroscopic and light receiving element 43, and a spectral characteristic recording section. In addition, both ends of the sample measurement cell 41 are infrared light transmitting windows 45, 4.
6 and has a structure that prevents gas leakage.

Additionally, gold was deposited on the inner surface of the measurement cell to prevent thermal decomposition of the sample. This measurement cell 41 is kept at a constant temperature by a constant temperature bath 47, and has a structure in which the sample does not solidify within the measurement cell 41.

The sample that has flown out of the IR further flows into the MS, but the configurations and functions of the carrier gas removal device and the MS are the same as those described in conjunction with FIG. 1, and the following explanation will be omitted.

It is clear that the composite analyzer according to the present invention has the above-described device configuration, and can further expand the range of applications of conventional analyzers. Furthermore, considering the combination of the composite measurement device according to the present invention and the data processing device based on recent advances in electrotechnology, information from a new database for attributing the structure of chemical substances that combines IR information and MS information can be used. It is thought that processing devices will also be realized in the near future.

In the explanation of MS based on the present invention, only MS using an electromagnetic field was mentioned, but the present invention does not limit the principle of MS, and when using a quadrupole mass spectrometer, is also applicable. In other words, the same effect can be obtained by applying a photoionization method to the ionization method of a quadrupole mass spectrometer.

The capture of the carrier gas by the carrier gas removing section in the embodiment shown in FIG. 1 will be explained with reference to FIG. 2. FIG. 2 is an enlarged view of the carrier gas removal section of FIG. 1, showing the electrode structure and the connection mechanism between the capillary tubes 17 and 18 and the electrodes 34 and 35. The heat-resistant connection mechanism works by compressing and fixing the O-ring 51 with mechanical pressure.

Although the material of the electrodes 34 and 35 is not particularly limited, it is necessary that they are electrically conductive, and in particular, the inner surface has a structure in which gold is vapor-deposited so that the sample components change due to the solvation effect.

〔Effect of the invention〕

Based on the present invention, the carrier gas removal device adopted in the GC-MS has a new function that ionizes sample components to give them an electric charge, and selectively introduces only the sample components into the MS using electrical action. There is an effect that can be done. FIG. 4 shows the results obtained in an example to demonstrate this effectiveness. In FIG. 4, a is a signal obtained when 44pentylcyclohexylanobenzene was measured using a total immotor in the MS in a GC-MS obtained by a conventional technique. It was found that when the same sample was used in combination with the ionization electric field method based on the present invention and the conventional method, the signal on the total ion monitor increased by 40% compared to the conventional method, demonstrating the effectiveness of the present invention. has been demonstrated.

In order to demonstrate the effectiveness of employing the photoionization method in the ionization chamber of MS, we measured mass fragments when ionized by thermionic electrons in the conventional method and fragments when the photoionization method according to the present invention was employed. Figure 5 shows mass fragments obtained using the photoionization method, and the molecular ion (parent ion) is clearly visible in both cases of Cl5H11k CNe C3H7% coo sha○CxHs and csHl-t-o%cN. . On the other hand, an example of measurement of mass fragments obtained by the conventional method, that is, the thermionic ion method, is shown in Figure 7. > The signal intensity of the molecular ion of QOCzHs is extremely weak and unclear. In addition, in Figure 7, the intensity of the molecular ion of C:1lH17-0 (currently CN) is weak and unclear.In other words, this indicates that the probability of generation of the molecular ion of an ester or ether compound is very weak. In the ion method according to the present invention, the molecular ion is detected as the main ion in any compound, and it is sufficient to measure the original molecular weight.

Furthermore, by directly connecting IR to such GC-MS, it is possible to perform IR measurement and simultaneous MS measurement with one sample, and there is no doubt that this method is effective for fixing substances. perhaps.

In the future, it is thought that the use of multiple analyzers that perform different measurements will become more complex, and the GC-IR-MS, based on the present invention, is considered to be a pioneer in the use of multiple types of analyzers.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a GC-MS based on the present invention, FIG. 2 is an enlarged explanatory diagram of the carrier gas removal section in FIG. 1, and FIG. 3 is a configuration diagram of a GC-IR-MS based on the present invention. , Fig. 4 is a diagram showing a demonstration example of the photoionization method in the present invention of the carrier gas removal section, Fig. 5 is a diagram showing a demonstration example of photoionization in the ionization chamber, and Fig. 6 is a diagram showing a demonstration example of the photoionization method in the present invention in the carrier gas removal section. The configuration diagram and FIG. 7 are diagrams showing an example of measurement of mass fragments by conventional ionization in an ion chamber. DESCRIPTION OF SYMBOLS 1... Temperature control part, 2... Gas chromatograph constant temperature bath, 3... Separation column, 4... Sample injection part, 5...
・Carrier gas supply tube, 6...Carrier gas removal section, 7...Rotary vacuum pump, 8,9.10...
・Oil diffusion pump, 11...Rotary vacuum pump, 12
...Mass spectrometry section, 13...Electron multiplier tube, 14...
Recording section, 15... Ion detection section, 16... Ionization chamber, 17.18... Capillary tube, 3o...
Photoionization detector, 31゜32...DC power supply section, 33...
- Electrometer, 34... positive electrode, 35... negative electrode, 36... positive discharge electrode, 37... light source, 41...
- Sample measurement cell, 42... Infrared light source, 43... Spectroscopic and light receiving element, 44... Spectral characteristic recording section, 45...
- Infrared light transmitting window, 46... Infrared light transmitting window.

Claims (1)

[Claims] 1. In a gas chromatograph-mass spectrometer (hereinafter abbreviated as GC-MS) that directly connects a gas chromatograph (hereinafter abbreviated as GC) and a mass spectrometer (hereinafter abbreviated as MS), GC
In a method in which the carrier gas and sample components that are more eluted are introduced into a separator (or separator), the concentration of the sample components in the carrier gas is increased, and the sample components are introduced into the MS, the carrier gas and the sample components are separated. The device is equipped with an ionization mechanism that can ionize only the sample component, which imparts a charge to the sample component, and the charged sample component is subjected to MS using an electric field.
This analyzer is directly connected to a gas chromatograph/mass spectrometer, which is characterized by its ability to lead to higher concentration of sample components and increase the collection efficiency of sample components to MS.