JP2002329475A - Gas chromatograph mass spectroscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure analytical accuracy also by generating of stable thermoelectrons, while preventing undesired consumption of a filament according to an evaporated solvent. SOLUTION: A control part 30 supervises pressure change in a vacuum container 21 of an MS section 20 by a pressure gauge 23, after pouring a liquid sample into a sample evaporation chamber 11a. When the pressure rises temporarily and returns back approximately to the original pressure, the control part 30 determines that the elution of the evaporated solvent from a column 12 has finished. And at the time the filament for emitting thermoelectrons in an ion source 24 of the MS section 20 is made to turn on, and control is started so as to cerise a predetermined heating current flows. Since the generation of the evaporated solvent is already finished, this can prevent unnecessary consumption of the filament. Also, since stabilized thermoelectron are emitted at the time when a target ingredient eluted from the column later that the evaporated solvent is introduced into the ion source 24, ionization is also stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas chromatograph mass spectrometer for introducing a sample separated by gas chromatography into a mass spectrometer for analysis.

[0002]

2. Description of the Related Art A gas chromatograph / mass spectrometer (hereinafter referred to as "GC / MS") is a mass spectrometer which separates a sample gas, which has been subjected to component separation in a column of a gas chromatograph (hereinafter referred to as "GC"), through an interface. ("MS
Unit ”). In the GC section, a sample vaporization chamber is provided at the inlet of the column, and when a liquid sample is injected into the sample vaporization chamber using a microsyringe and vaporized and introduced into the column, most of the liquid sample is a solvent.
A large amount of vaporized solvent will be introduced into the column. Usually, such a solvent passes through the column first and is introduced into the MS part, and the target component to be originally analyzed reaches the MS part sequentially later than that.

[0003] The MS section including the ion source is disposed in a vacuum vessel maintained in a vacuum state. However, as described above, when a large amount of vaporized solvent passes through the column and is introduced into the MS section. The degree of vacuum in the vacuum vessel rapidly decreases. In the configuration in which ionization is performed by the so-called electron impact method in the ion source, when a large amount of the vaporized solvent flows in as described above, the current flowing due to the thermionic current suddenly decreases, and the generation of thermionic electrons is further compensated for. The heating current flowing through the filament is abruptly increased in order to promote the heating. For this reason, there is a problem that the consumption of the filament becomes severe and the life until the wire breaks or the like becomes extremely short.

On the other hand, it takes a certain amount of time for the emission state of thermoelectrons to stabilize after the filament is turned on.
If the emission state of the thermoelectrons is not yet stable at the time when the target component is introduced into the MS part after the lighting of the filament is delayed,
There is a problem that ionization becomes unstable and analysis accuracy is reduced.

[0005]

SUMMARY OF THE INVENTION
In GC / MS, it is desirable to wait for the solvent component to elute from the column after sample injection, and then turn on the filament of the ion source as soon as possible.
The solvent elution time after the sample injection until the solvent component exits the column depends not only on the setting conditions such as the temperature and pressure of the GC, but also on the conditions such as the type and dimensions of the column, and there are individual differences for each device. are doing. For this reason, conventionally, it has to be determined based on theoretical calculations and experience, and requires some skill.

In addition, when the elution of the target component is relatively quick, the filament is often turned on earlier in consideration of the error in estimating the solvent elution time, with priority given to ensuring the accuracy of the analysis. Often, the life of the filament is shortened.

[0007] The present invention has been made in view of the above points, and a purpose thereof is to provide an ion source, particularly without an operator having experience or skill or performing complicated calculations. An object of the present invention is to provide a gas chromatograph mass spectrometer capable of accurately and easily determining a lighting time of a filament, and preventing unnecessary consumption of a filament while maintaining high analysis accuracy and reproducibility.

[0008]

According to the present invention, which has been made to solve the above-mentioned problems, a sample separated by a column of a gas chromatograph unit having a sample vaporizing unit at an inlet is provided in a vacuum vessel. In the gas chromatograph mass spectrometer to be introduced into the ion source of the mass spectrometry unit, which performs ionization using thermoelectrons generated in a filament as the ion source, a) reducing the gas pressure in the vacuum vessel Pressure measuring means for measuring, b) based on a change in the measured gas pressure by the pressure measuring means after injecting a sample into the sample vaporizing section,
And estimating means for estimating the end time of the elution of the solvent from the column, wherein timing for lighting the filament is determined based on the estimation by the estimating means.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS That is, after a liquid sample is injected into a sample vaporizing section, the solvent contained in the sample vaporized in the sample vaporizing section starts to elute from the column earliest, and the vaporized solvent is introduced into the mass spectrometric section. During the operation, the degree of vacuum in the vacuum vessel is deteriorated and the gas pressure measured by the pressure measuring means is increased. The estimating means estimates a period during which the solvent is introduced into the mass spectrometric unit due to such a change in gas pressure, that is, a point in time at which the solvent is completely eluted from the column.

According to one embodiment of the present invention, there is provided a control means for automatically turning on a filament at a time when the estimating means estimates that the elution of the solvent from the column is completed, or at a time later than that. Can be provided. Further, as another embodiment, a condition storage means for calculating the solvent elution time based on the estimation by the estimation means and storing this value in association with, for example, the analysis conditions at that time, Further, a search means for searching for a solvent elution time corresponding to the analysis condition from the condition storage means when the analysis condition is input and set is further provided, and an operator or automatically sets the filament lighting timing based on the search result. The configuration may be determined.

[0011]

As described above, the gas chromatograph mass spectrometer according to the present invention accurately measures the solvent elution time,
Based on this, the lighting timing of the filament of the ion source is determined automatically or according to the setting operation of the operator. Therefore, the filament can be turned on after the solvent is completely eluted from the column, thereby preventing the filament from being undesirably consumed due to a rapid inflow of the vaporized solvent. This extends the life of the filament,
The reliability can be increased and the analysis cost can be reduced. In addition, since the filament can be turned on sufficiently prior to the analysis of the target component, thermoelectrons are stably generated, ionization is stabilized, and as a result, analysis accuracy can be improved. Further, in order to determine the appropriate filament lighting timing as described above, complicated calculation and operator skill are not required.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the gas chromatograph mass spectrometer according to the present invention will be described below with reference to the drawings.
FIG. 1 is an overall configuration diagram of main parts of the GC / MS.

In the GC unit 10, a column oven 13
Column (capillary column) 12 heated to an appropriate temperature by a carrier gas (He gas) at a predetermined flow rate through a sample vaporization chamber 11a which is a part of the injector 11.
Is supplied, and the sample vaporization chamber 11 is
The liquid sample injected into a is immediately vaporized and carried into the column 12 along with the carrier gas flow. While passing through the column 12, each component in the sample gas is temporally separated and reaches the outlet thereof.
4 through the sample introduction tube 16 to the ion source 2 of the MS section 20.
4 is introduced.

In the MS section 20, the ion source 24 is provided with a filament 25 for generating thermoelectrons, and the component molecules introduced into the ion source 24 are ionized by contact with the thermoelectrons. The generated ions are extracted outside the ion source 24, converged by the ion lens 26, and introduced into the space in the longitudinal direction of the quadrupole filter (or other mass separator) 27. A voltage obtained by superimposing a DC voltage and a high-frequency voltage is applied to the quadrupole filter 27, and only ions having a mass number (mass m / charge z) corresponding to the applied voltage pass through the space in the long axis direction. , Reaches the detector 28 and is detected. Ion source 24, ion lens 26,
The quadrupole filter 27 and the detector 28 are
The vacuum degree in the vacuum vessel 21, that is, the gas pressure, is measured by the pressure gauge 23.

The temperature of the column 12 depends on the kind of the target component and the like (mainly in accordance with the boiling point of the target component), and is usually 100.
The temperature is appropriately set within the range of about 300 ° C. Column 1
When the temperature of the sample gas that has reached the outlet 2 decreases, the flow of the gas deteriorates, which causes deterioration of analysis accuracy and the like. Therefore, also in the interface unit 14, the heater 1 disposed around the sample introduction tube 16 connected to the outlet of the column 12.
By 5, the sample introduction tube 16 is heated so as to maintain the temperature substantially equal to the maximum temperature of the column 12. Thereby, the sample gas is introduced from the outlet of the column 12 to the ion source 24 without any delay. The ion source 24 is also heated to an appropriate temperature for stably ionizing, for example, a temperature several tens of degrees lower than the interface unit 14.

The GC unit 10, the interface unit 14, and the M
The operation of each component of the S unit 20 is generally controlled by a control unit 30 embodied by a personal computer. The control unit 30 is connected to an operation setting unit 31 for setting analysis conditions and the like by an operator, a display unit 32 for displaying setting contents, displaying analysis results, and the like.

Next, an example of a characteristic operation of the GC / MS will be described with reference to FIG. FIG. 2A is a chromatogram showing the signal intensity of the eluted component at the outlet of the column 12, and FIG. 2B is a graph showing a pressure change in the vacuum vessel 21 of the MS section 20. Note that this GC / MS
Since no detector other than the MS part is provided at the outlet of the column 12, a chromatogram as shown in FIG. 2A is not actually obtained.

Prior to performing an analysis in the present apparatus, the operator inputs analysis conditions such as various parameters necessary for the analysis through the operation setting section 31. For example, regarding the GC unit 10, the sample vaporization chamber 11a and the column oven 13
(The temperature profile or the like), the supply pressure (or flow rate) of the carrier gas flow, the type and size (inner diameter and length) of the column 12, and the like. As for the MS unit 20, it is necessary to set temperature conditions and the like,
It is not necessary to set conditions regarding the lighting time (timing) of the filament 25.

When the start of the analysis is instructed, the control unit 30
Is controlled by controlling the inlet gas pressure or the gas flow rate so that the carrier gas flows at a constant flow rate through the column 12 in the GC unit 10, and the vacuum pump 22 performs vacuum control so that the pressure detected by the pressure gauge 23 is maintained substantially constant. The inside of the container 21 is exhausted. At time t0, a control signal is sent to the injector 11 to inject the liquid sample into the sample vaporizing chamber 11a. At that time, the pressure detected by the pressure gauge 23 is temporarily stored in the internal memory as the initial pressure P0. After the sample is injected, the pressure detected by the pressure gauge 23 is monitored every moment and compared with the initial pressure P0 stored in the internal memory.

Generally, most of the liquid sample injected into the sample vaporization chamber 11a is a solvent, and the target sample component is a very small amount. Since such a solvent component passes quickly without being adsorbed on the inner wall of the column 12, it elutes from the column 12 earliest before other target components. Therefore, the chromatogram is as shown in FIG. 2 (a). After the injection of the sample, a large amount of the solvent component first flows out, and a large peak appears, followed by the peak of the target component to be originally analyzed. Appears in

Since the amount of the vaporized solvent is large, if the vaporized solvent is eluted from the column 12 and introduced into the ion source 24 after the sample injection, the evacuation by the vacuum pump 22 cannot catch up, and the pressure in the vacuum vessel 21 is reduced as shown in FIG. It rises temporarily as shown in (b). This pressure increase continues until the time when the solvent has completely exited the column 12 or a little later, after which the pressure almost returns to the value before the increase. Therefore, the controller 30 determines that the elution of the solvent from the column 12 has been completed when the difference between the detected pressure and the initial pressure P0 becomes larger than the predetermined value again after the difference becomes larger. That is, the time from the sample injection time t0 to the time t1 when it is determined that the solvent has been eluted is the solvent elution time T.

In the MS section 20, it is not necessary to perform mass spectrometry while the vaporized solvent is being introduced into the ion source 24, and it is sufficient to perform the analysis after the introduction of the target component. However, the filament 25 for emitting thermoelectrons needs to have a certain time margin from when it is turned on until the temperature rises sufficiently and thermoelectrons are stably generated. Therefore, the control unit 30 turns on the filament 25 when it is determined that the solvent has been eluted (or when it is delayed by an appropriate time). Then, a normal heating current is controlled such that the current flowing by the thermoelectrons becomes a predetermined value.
As a result, when the first target component starts to elute from the column 12 and is introduced into the ion source 24, thermoelectrons are stably emitted from the filament 25, and the target component molecules or atoms are stably ionized.

Thus, the GC / M according to the present embodiment is
In S, without the operator inputting and setting the lighting time of the filament 25, after the time when the elution of the vaporized solvent from the column 12 is completed, and sufficiently before the first target component starts to elute, The filament 25 of the ion source 24 can be turned on. Therefore, the filament 25 is not consumed by the vaporized solvent, and can stably emit thermoelectrons during ionization of the target component to perform appropriate ionization.

In the apparatus according to the above embodiment, the pressure change in the vacuum vessel 21 is monitored for each analysis, and the lighting timing of the filament 25 is automatically determined based on the pressure change. However, in some cases, it may be preferable to give the operator room to adjust the lighting time of the filament 25. Even in such a case, the following control may be performed so that the operator does not need to perform complicated calculations or perform calculations and does not need to be skilled.

That is, the GC according to another embodiment of the present invention
In the / MS configuration, similarly to the apparatus according to the above-described embodiment, when the time t1 at which the elution of the solvent is completed based on the pressure change in the vacuum vessel 21 after the sample injection is determined, the solvent elution time T is then set. calculate. If the same analysis conditions have not been set in the past when the analysis conditions were initially set, the solvent elution time T at that time must be determined. The elution time is stored in a non-volatile memory.

If analysis conditions are set by the operation setting section 31 prior to the analysis, it is searched whether or not the same analysis conditions exist in the past. If the same analysis conditions exist, the corresponding analysis conditions are determined. The solvent elution time is read out and displayed on the display unit 32. The operator determines the filament lighting time using the displayed solvent elution time as a guide, and inputs and sets it as one of the analysis conditions from the operation setting unit 31. Thus, the operator can make his / her own judgment and set the filament lighting time to be earlier or later. For example, if it is known that the elution of the first target component is considerably slow, the filament 25 may be used immediately after the elution of the solvent is completed.
Is turned on, the time during which the filament 25 is turned on is uselessly lengthened. Therefore, it is possible to intentionally turn on the filament 25 with a considerably long delay from the end of the solvent elution.

The above embodiment is merely an example, and it is apparent that modifications and changes can be made within the spirit of the present invention.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a gas chromatograph mass spectrometer according to one embodiment of the present invention.

FIG. 2 is a diagram showing an example of a chromatogram at the time of analysis and an example of a change in gas pressure in a vacuum vessel of an MS unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Gas chromatograph part (GC part) 11 ... Injector 11a ... Sample vaporization chamber 12 ... Column 14 ... Interface part 20 ... Mass spectrometry part (MS part) 21 ... Vacuum container 22 ... Vacuum pump 23 ... Pressure gauge 24 ... Ion source 25 ... filament 30 ... control unit 31 ... operation setting unit

Claims (1)

[Claims] 1. A gas chromatograph mass spectrometer for introducing a sample separated by a column of a gas chromatograph section having a sample vaporizing section at an inlet into an ion source of a mass spectrometric section disposed in a vacuum vessel. A method for performing ionization using thermoelectrons generated by a filament as the ion source, a) pressure measuring means for measuring a gas pressure in the vacuum vessel, and b) a sample was injected into the sample vaporizing section. Estimating means for estimating the end time of elution of the solvent from the column, based on a change in the measured gas pressure by the pressure measuring means after,
A gas chromatograph mass spectrometer characterized in that the timing for lighting the filament is determined based on the estimation by the estimating means.