JP2001126658A - Mass spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mass spectrometer that may be performed before calibration of the magnetic field intensity, and reduce the chemical noise resulting from the standard specimen on measuring high fidelity and high resolution SIM by lock mass method. SOLUTION: The ion source is provided with multiple standard specimen inlet parts, one of which is used for introducing the standard specimen for compensating for the magnetic field into the ion source, and the other for introducing the standard specimen for lock mass to the ion source on measuring the high fidelity and high resolution SIM by lock mass method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass spectrometer, and more particularly to a mass spectrometer for measuring a highly sensitive SIM by the rock mass method.
The present invention relates to a mass spectrometer capable of reducing chemical noise.

[0002]

2. Description of the Related Art There are two methods for detecting ions using a double focusing mass spectrometer, a SIM method and a scanning method.

[0003] The SIM method is called Selected Ion Monitoring.
This is an abbreviation of the method (selection ion detection method), as shown in FIG. This is a method of increasing the ion detection sensitivity by repeating the operation of switching the mass number.
It is used for mass spectrometry by gas chromatography / mass spectrometry (GC / MS), particularly when quantifying ions having a predetermined mass number. Then, by arranging the ion intensity data obtained by sequentially repeating the switching as a function of time, a SIM chromatogram representing the retention time of the target component on the GC column can be obtained.

[0004] On the other hand, in the scanning method, the mass distribution of ions is measured as a series of spectra while continuously sweeping the magnetic field strength or the acceleration voltage strength for components flowing out of the GC. In the case of the scanning method,
A chromatogram can be obtained by displaying the peak intensity of a predetermined peak of the detected ion as a function of time. In this case, this is called a mass chromatogram and is distinguished from a SIM chromatogram.

[0005] The SIM method can provide a sensitivity 100 times or more higher than that of the scanning method due to the difference in the method of detecting ions. Widely applied to measurement.

[0006] In quantitative analysis of dioxin, which has recently attracted attention, SIM measurement is often performed with high resolution in order to properly separate contaminant components and target components by mass. In SIM measurement under high-resolution conditions, the ion peak becomes very sharp, and it is extremely difficult to always accurately capture the peak top of the target component. Therefore, in order to accurately capture the peak top of each ion, before starting the SIM measurement, a standard sample having a known mass in advance, for example, perfluorokerosine (PFK) is introduced into the ion source and the mass spectrum is measured. Then, calibration of the magnetic field strength is performed.

During the high-resolution SIM measurement, a standard sample having a known mass-to-charge ratio, for example, the above-mentioned PFK is appropriately used as an ion source in order to prevent the ion mass setting position from changing with time due to drift of the magnetic field. While monitoring the position of the signal from the standard
Correction for drift of the magnetic field and the like is performed. This technique is called the Rockmass method.

[0008]

In such a configuration, the PFK used for the calibration of the magnetic field intensity performed before the start of the high-resolution SIM measurement is a standard sample having many ion peaks in a wide mass range. Therefore, from those ion peaks, select an ion peak that is relatively close to the ion peak of the target component,
It is a standard sample that can be calibrated for magnetic field strength and is extremely suitable for magnetic field strength calibration.

However, when this PFK is used as a standard sample for rock mass, there is an advantage that the same standard sample introduction part can be used for both calibration of the magnetic field intensity and measurement by the rock mass method. On the other hand, PFK is scattered in the ion source while measuring the ions of the target component by the rock mass method, and many ion peaks derived from the PFK are mixed into the ion peaks derived from the target component. SIM quantitative measurement often causes chemical noise, and as a result, S
There is a problem that the / N ratio is lowered.

In view of the foregoing, it is an object of the present invention to perform calibration of magnetic field strength before measurement,
At the time of high-sensitivity high-resolution SIM measurement by the rock mass method,
An object of the present invention is to provide a mass spectrometer capable of reducing chemical noise derived from a standard sample.

[0011]

In order to achieve the above object, a mass spectrometer according to the present invention is characterized in that a plurality of reservoirs are connected to an ion source.

A magnetic field calibration standard sample for connecting a plurality of reservoirs to the ion source to calibrate the magnetic field,
It is characterized in that a standard sample for rock mass for performing high-sensitivity quantitative measurement using the rock mass method is supplied to the ion source from a separate reservoir.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing one embodiment of the mass spectrometer according to the present invention. In the figure, reference numeral 1 denotes an ion source of the double focusing mass spectrometer. The ion source 1 is provided with an ionization chamber 2. The ionization chamber 2 is connected via a needle valve 3 and a cut valve 4 to a reservoir 5 storing a standard sample for calibration of the magnetic field strength. The reservoir 5 is provided with a sample introduction port (not shown). The piping 6 connecting the ionization chamber 2 and the reservoir 5 is evacuated to about 100 Pa by a rotary pump (not shown). The needle valve 3, cut valve 4, reservoir 5, and pipe 6 are integrated to form a first
A standard sample introduction part is formed. The first standard sample introduction part is exactly the same as the conventional standard sample introduction part,
In the M measurement and the scan measurement, it is used for the calibration of the magnetic field strength of the double focusing mass spectrometer.

An auxiliary reservoir 9 storing a standard sample for lock mass is connected to the ionization chamber 2 via another needle valve 7 and a cut valve 8. Also,
A pipe 10 connecting the ionization chamber 2 and the auxiliary reservoir 9 is evacuated to about 100 Pa by a rotary pump (not shown). The needle valve 7, the cut valve 8, the auxiliary reservoir 9, and the pipe 10 are integrally formed to form a second standard sample introduction section. The second standard sample introduction part is newly provided in the present invention, and is used at the time of high-sensitivity SIM measurement by the rock mass method.

In such a configuration, the reservoir 5 and the auxiliary reservoir 9 contain different types of standard samples, respectively. That is, a standard sample suitable for calibration of magnetic field strength such as PFK having many ion peaks in a wide mass range, an auxiliary reservoir 9 is provided in the reservoir 5.
Stores a standard sample of a type suitable for the rock mass method having a limited number of ion peaks in the vicinity of a predetermined mass number.

When calibrating or tuning the magnetic field strength of the double focusing mass spectrometer, the cut valve 4 connected to the reservoir 5 of the first standard sample introduction unit is opened, and the flow rate is adjusted by the needle valve 3, The calibration standard sample is introduced into the ionization chamber 2 through the pipe 6. Since the inside of the pipe 6 is under reduced pressure,
The calibration standard sample contained in the reservoir 5 is easily introduced into the ionization chamber 2 via the pipe 6. At this time, since the auxiliary reservoir 9 for the lock mass is not used, it is closed by the cut valve 8 on the second standard sample introduction part side.

In the case of the high-sensitivity SIM quantitative measurement by the rock mass method, the auxiliary reservoir 9 of the second standard sample introduction part is used.
By opening the cut valve 8 connected to, and adjusting the flow rate with the needle valve 7, the standard sample for rock mass is introduced into the ionization chamber 2 through the pipe 10. Since the inside of the pipe 10 is under reduced pressure, the lock mass standard sample contained in the auxiliary reservoir 9 is easily introduced into the ionization chamber 2 via the pipe 10. At this time, since the calibration reservoir 5 is not used, it is closed by the cut valve 4 on the first standard sample introduction unit side.

As described above, in the present invention, since a plurality of reservoirs are provided in the ionization chamber 2, only one standard sample can be used.
It is not limited to the kind, and it becomes possible to use a standard sample having properties suitable for the purpose of use. As a result, at the time of high-sensitivity SIM measurement using the rock mass method, it is possible to introduce a standard sample that gives a minimum necessary number of ion peaks from the auxiliary reservoir 9 of the second standard sample introduction unit into the ionization chamber 2. It is possible to reduce the chemical noise since it is not necessary to use a standard sample that gives many ion peaks such as PFK. In addition, since the standard sample has a small number of peaks, a strong peak intensity can be obtained with a small amount and the amount of the standard sample introduced can be reduced, which is also effective in preventing contamination of the ion source.

In this embodiment, a double focusing mass spectrometer having two standard sample introduction sections has been described. However, only one standard sample introduction section is provided, and a plurality of reservoirs are switched by a switching valve. You may comprise so that it may be connected. In such a case, since the needle valve and the pipe are shared by a plurality of standard samples, the standard sample remains as a memory in the shared portion.

In this embodiment, the cut valve and the needle valve are also provided on the side of the second standard sample introduction section. However, the standard sample introduction section for the lock mass is provided with the impurity ions from the cut valve and the needle valve. The cut valve and the needle valve may be omitted in order to prevent the occurrence of the above.

Further, in this embodiment, the case where two reservoirs are connected to the ion source has been described, but the present invention is not limited to this. It goes without saying that the number of reservoirs may be further increased as necessary.

[0022]

As described above, according to the mass spectrometer of the present invention, a plurality of reservoirs are provided in the ion source.
It is not necessary to use a standard sample that gives many ion peaks such as PFK at the time of high-sensitivity SIM measurement by the rock mass method, and it is possible to reduce chemical noise at the time of high-sensitivity SIM measurement. Further, since the amount of the standard sample to be introduced can be reduced, it is effective in preventing contamination of the ion source.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a SIM method and a scanning method.

FIG. 2 is a diagram showing one embodiment of a mass spectrometer according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ion source, 2 ... Ionization chamber, 3 ... Needle valve, 4 ... Cut valve, 5 ... Reservoir, 6 ... Piping,
7: Needle valve, 8: Cut valve, 9: Auxiliary reservoir, 10: Piping.

Claims (2)

[Claims] 1. A mass spectrometer in which a plurality of reservoirs are connected to an ion source. 2. A plurality of reservoirs are connected to an ion source, and a standard sample for magnetic field calibration for calibrating a magnetic field and a standard sample for rock mass for performing high-sensitivity quantitative measurement using a rock mass method are separately provided. A mass spectrometer characterized in that the ion source is supplied from a reservoir of the mass spectrometer.