JP3885185B2 - Mass spectrometer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mass spectrometer, and more particularly, to a mass spectrometer suitable for analyzing the mass of a substance to be analyzed using explosives or narcotics as analysis targets.
[0002]
[Prior art]
When detecting a dangerous object, for example, an X-ray inspection apparatus is generally employed as in baggage inspection at an airport. In addition, when detecting explosives among dangerous substances, a method using a gas chromatography electron capture detector and a method using a plasma chromatography mass spectrometer using β-rays are employed. However, in any of these methods, it is theoretically difficult to detect RDX (hexogen) or PETN (pen slit) having a low vapor pressure, for example, 10 ⁻⁷ Pa level, which is a main component of a plastic bomb, Moreover, since analysis takes several seconds to several tens of seconds, it has not been used for baggage inspection at airports that require real-time monitoring.
[0003]
On the other hand, for example, a device described in Japanese Patent Application Laid-Open No. 7-134970 is known as a device using a mass analyzer for a dangerous substance detection device.
[0004]
[Problems to be solved by the invention]
In a dangerous substance detection device using a conventional mass spectrometer, the detection object detects the detection object such as explosives by utilizing the property that the detection object easily generates negative ions and positive ions. It is not sensitive enough to be used for baggage inspection at airports.
[0005]
An object of the present invention is to provide a mass spectrometer capable of removing unnecessary substances prior to mass analysis of substances in a sample gas containing substances to be analyzed.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a sample separation means for introducing and ionizing a sample gas containing a substance to be analyzed from a sample and separating the ionized sample gas into a positive ion substance and a negative ion substance. In addition, the mass spectrometer is configured to include one ion substance separated by the sample separation means and ionize it, and also to mass analysis means for analyzing the mass of the ionized ion substance.
[0007]
In configuring the mass spectrometer, a sample gas generating means for generating a sample gas containing a substance to be analyzed from a sample by bringing a gas into contact with the sample is provided, and the sample gas from the sample gas generating means is sample-separating means. It is also possible to adopt the configuration introduced in
[0008]
In configuring each mass spectrometer, the following elements can be added.
[0009]
(1) The sample separation means includes a corona discharge electrode for generating a corona discharge in the gas. The corona discharge electrode is negatively excited when a substance having a strong binding to negative ions is to be analyzed. When a substance having a strong bond with the target is analyzed, it is positively excited.
[0010]
(2) The sample separation means includes an auxiliary electrode having a polarity different from that of the corona discharge electrode, and the auxiliary electrode is an ionic material having a polarity different from an ionic material generated by ionizing a substance to be analyzed. To capture.
[0011]
(3) The sample separation means includes a polarity switching means for switching the polarity of the corona discharge electrode, and the polarity switching means switches the polarity of the corona discharge electrode according to a specified timing to make the corona discharge electrode negative. Excited or positively excited.
[0012]
(4) The sample separation unit includes an auxiliary polarity switching unit that switches the polarity of the auxiliary electrode, and the auxiliary polarity switching unit sets the polarity of the auxiliary electrode at a specified timing in conjunction with the polarity switching unit. Switch.
[0013]
According to the above-described means, the ion gas obtained by ionizing the substance to be analyzed (detection target) is ionized by the mass analyzing means and ionized by the sample gas and the ionized sample prior to the mass analysis. Gas is separated with positive and negative ion substances to remove unnecessary substances, and one of the separated ion substances is introduced into the mass spectrometry means, thus increasing the analysis sensitivity (detection sensitivity) for the substance to be analyzed. be able to.
[0014]
In addition, when analyzing (detecting) nitro compounds as substances to be analyzed, the corona discharge electrode is excited positively, unnecessary substances are positively ionized, and nitro compounds are negatively ionized to easily detect nitro compounds. can do. On the other hand, in the case of a substance that easily generates positive ions, such as narcotics, narcotics can be easily detected by negatively exciting the corona discharge electrode and negatively ionizing unnecessary substances.
[0015]
In addition, even when the characteristics of the substance to be analyzed or detected are unknown, the polarity of the corona discharge electrode and auxiliary electrode can be switched at the specified timing to easily detect substances that are easily positively or negatively ionized. can do.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a mass spectrometer showing an embodiment of the present invention. In FIG. 1, a mass spectrometer includes a sample gas generation unit 10 as a sample gas generation unit, a sample separation unit 12 as a sample separation unit, and a mass analysis unit 14 as a mass analysis unit constituting a mass spectrometer. It is prepared for.
[0017]
The sample gas generator 10 includes an air cylinder 16 and a sample container 18, and the air cylinder 16 and the sample container 18 are connected via a cylindrical pipe 20. The air cylinder 16 supplies air as a gas (gas) into the sample container 18 via the pipe 20. A sample container 18 containing an explosive, for example, an organic nitro compound, is stored in the sample container 18. When the air from the air cylinder 16 is blown onto the sample 22 and the air contacts the sample 22, the sample 22 analyzes the sample 22. A sample gas containing the target substance (detection target) is generated. This sample gas is introduced into the sample separation unit 12 through a cylindrical pipe 24.
[0018]
As shown in FIG. 2, a plurality of partition plates 26, 28, and 30 are arranged at intervals in the pipe 24, and a different ion detection electrode 32 as an auxiliary electrode is inserted. Through holes 34 and 36 are respectively formed in the central portions of the partition plates 26 and 30. A shaft-like corona discharge electrode 38 is fixed to the central portion of the partition plate 24, and the corona discharge electrode 38 is connected to a corona discharge power source 40 through the partition plate 28. Furthermore, a plurality of through holes 42 are formed in the partition plate 28. A pipe 44 is connected between the partition plates 28 and 30 in the pipe 24, and a pipe 46 is connected between the partition plate 30 and the different ion detection electrode 32. Further, the different ion detection electrode 32 is connected to a different ion detection power supply 48. In addition, the outer peripheral side of the different ion detection electrode 32 is fixed to the pipe 24 via an insulator 50.
[0019]
Here, as a substance to be analyzed, for example, when it is assumed that the sample 22 contains an organic nitro compound, the nitro compound has an elemental composition close to oxygen equilibrium, and easily generates negative ions with corona discharge. To generate. Therefore, the corona discharge electrode 38 is positively excited by the power supply 40 to positively ionize unnecessary substances, and negatively excited by applying a negative voltage from the power supply 48 to the different ion detection electrode 32 to remove the positively ionized unnecessary substances. Capture by the different ion detection electrode 32 is performed.
[0020]
Specifically, when the sample gas from the sample container 18 is introduced into the pipe 24, the sample gas is introduced into the region between the partition plate 26 and the partition plate 28 through the through hole 34 of the partition plate 26. The At this time, when corona discharge is generated in the gas by the corona discharge electrode 38, the sample gas is ionized by oxygen ions generated by the corona discharge in the gas. At this time, the nitro compound is fed as a negative ionic substance to the region of the partition plate 28 and the partition plate 30 through the through hole 42, and the unnecessary substance is a positive ion substance through the through hole 42 and the partition plate 28 and the partition plate. To the area between 30. Among these positive ion substances and negative ion substances, positive ion substances (unnecessary substances) are adsorbed by the negative voltage of the different ion detection electrode 32 and captured (adsorbed) by the different ion detection electrode 32 through the through hole 36. A part of the positive ion substance is discharged through the pipe 46, and the negative ion substance is supplied to the mass analyzer 14 through the pipe 44.
[0021]
As shown in FIG. 1, the mass analyzer 14 includes an ion source 52, a mass analyzer 54, an amplifier 56, and a measurement processing display 58. The ion source 52 is connected to a pipe 44, and the ion source The negative ion substance in the pipe 44 is introduced into the pipe 52. The ion source 52 includes a corona discharge electrode 60. The negative ion material introduced from the pipe 44 is introduced, the corona discharge electrode 60 generates a corona discharge to ionize the negative ion material, and the ionized negative ion material is converted into an ion source. For example, it is emitted to the mass analyzer 54 as an ion beam. The mass analyzer 54 includes a permanent magnet 62, an ion detector 64, and the like, and the mass analyzer 54 is evacuated to a high vacuum state by a vacuum evacuation device (not shown). In the process of passing between the magnets 62, the ion beam from the ion source 52 is input to the ion detector 64 along a trajectory corresponding to its mass. The ion detector 64 outputs a signal corresponding to the input position of the ion beam. The electric signal output from the ion detector 64 is amplified by the amplifier 56 and then input to the measurement processing display 58. The measurement processing indicator 58 processes the signal from the amplifier 56 and displays an image of the measurement value corresponding to the mass. When the sample 22 contains a nitro compound, the measured value of the mass corresponding to the nitro compound is displayed, and it can be understood from this display result that the sample 22 contains the nitro compound.
[0022]
Thus, in the present embodiment, prior to performing mass analysis on the substance to be analyzed (detection target) in the mass analyzer 14, the substance contained in the sample gas is converted into a positive ion substance and a negative ion in the sample separator 12. Since it is separated into substances, positive ion substances that are unnecessary substances are removed, and negative ion substances are sent to the mass analyzer 14, the analysis (detection) sensitivity can be increased, and the time required for analysis is also increased. Can be shortened.
[0023]
In the above embodiment, the detection of the nitro compound is described as the dangerous substance detection. However, when detecting a substance having a characteristic of easily generating positive ions in association with the corona discharge, for example, narcotics, the nitro compound is detected. Contrary to the case of detecting a compound, a negative voltage is applied to the corona discharge electrode 38 and negative excitation is performed, and a positive voltage is applied to the different ion detection electrode 32 to perform positive excitation. Since the substance is captured by the different ion detection electrode 32 and the positive ion substance is fed to the mass analyzer 14, the narcotic can be detected or analyzed with high sensitivity and high speed.
[0024]
On the other hand, when explosives or narcotics are detected at an arbitrary time period, a positive voltage or a negative voltage is applied to the corona discharge electrode 38 and the different ion detection electrode 32 at an arbitrary timing or at a designated timing, thereby causing narcotics or narcotics. Explosives can be detected simultaneously.
[0025]
Specifically, as shown in FIG. 3, a power supply switching circuit 66 is inserted between the corona discharge electrode 38 and the power supply 40 and a power supply switching circuit 68 is inserted between the different ion detection electrode 32 and the power supply 48. .
[0026]
The power supply switching circuits 66 and 68 can be configured using, for example, a positive excitation circuit 70, a negative excitation circuit 72, and power transistors (power MOSFETs) Q1, Q2, Q3, and Q4 as shown in FIG. As shown in FIG. 5, the positive excitation circuit 70 outputs a positive pulse to the transistors Q1 and Q4 for 2 seconds at a designated timing, and the negative excitation open circuit 72 is at a designated timing, that is, positive excitation. After the pulse signal is output from the circuit 70, an ON pulse is output to the transistors Q2 and Q3 for 2 seconds after 2 seconds.
[0027]
Therefore, when detecting a negative ion substance, the corona discharge electrode 38 is positively excited for 2 seconds and the different ion detection electrode 32 is negatively excited. In order to detect, the power source switching circuits 66 and 68 are switched, the corona discharge electrode 38 is negatively excited for 2 seconds and the different ion detection electrode 32 is positively excited, and then the cycle of the non-excitation period for 2 seconds is repeated. Thus, the negative ion substance and the positive ion substance can be detected simultaneously. Also in this case, the negative ion substance and the positive ion substance can be detected with high sensitivity and high speed.
[0028]
In the case where the positive ion substance and the negative ion substance are detected simultaneously, an element having the same function as that of the power supply switching circuit 66 is connected to the corona discharge electrode 60, and the excitation state of the corona discharge electrode 60 is positive excitation or negative excitation. It is desirable to switch to a state.
[0029]
In addition, the present invention can be used for baggage inspection at an airport by installing the sample container 18 in a baggage conveyance path such as an airport.
[0030]
【The invention's effect】
As described above, according to the present invention, the sample gas is ionized prior to ionization and mass analysis of the ion substance obtained by ionizing the substance to be analyzed (detection object) by the mass analyzing means. The sample gas ionized together with the positive ion substance and the negative ion substance is separated to remove unnecessary substances, and one of the separated ion substances is introduced into the mass spectrometry means. Detection sensitivity).
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a mass spectrometer showing an embodiment of the present invention.
2A is an enlarged view of a main part of a sample separation unit, and FIG. 2B is a front view of a different ion detection electrode.
FIG. 3 is a configuration diagram when a power source switching circuit is provided in a sample separation unit.
FIG. 4 is a circuit configuration diagram of a power supply switching circuit.
FIG. 5 is a time chart for explaining the operation when a positive ion substance and a negative ion substance are detected simultaneously.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Sample gas generation part 12 Sample separation part 14 Mass analysis part 16 Air cylinder 18 Sample container 26,28,30 Partition plate 32 Different ion detection electrode 38 Corona discharge electrode 52 Ion source 54 Mass analyzer 56 Amplifier 58 Measurement process indicator

Claims (6)

Sample separation means for introducing and ionizing a sample gas containing a substance to be analyzed from a sample and separating the ionized sample gas into a positive ion substance and a negative ion substance, and one ion separated by the sample separation means A mass spectrometer comprising: a mass analyzing means for introducing and ionizing a substance and analyzing the mass of the ionized ion substance. A sample gas generating means for generating a sample gas containing a substance to be analyzed from the sample by bringing the gas into contact with the sample; and introducing the sample gas from the sample gas generating means to ionize the ionized sample gas as a positive ion substance A sample separation means for separating the ionic substance into a negative ion substance, and a mass analysis means for introducing and ionizing one of the ionic substances separated by the sample separation means and analyzing the mass of the ionized ionic substance. A mass spectrometer. The sample separation means includes a corona discharge electrode for generating a corona discharge in the gas. The corona discharge electrode is negatively excited when a substance having a strong binding to negative ions is to be analyzed. The mass spectrometer according to claim 1, wherein the mass spectrometer is positively excited when a strong substance is to be analyzed. The sample separation means includes an auxiliary electrode having a polarity different from that of the corona discharge electrode, and the auxiliary electrode captures an ionic substance having a polarity different from an ionic substance generated by ionizing the substance to be analyzed. The mass spectrometer according to claim 3. The sample separation means includes polarity switching means for switching the polarity of the corona discharge electrode, and the polarity switching means switches the polarity of the corona discharge electrode according to a specified timing to negatively or positively correlate the corona discharge electrode. The mass spectrometer according to claim 3 or 4, wherein the mass spectrometer is excited. The sample separation means includes auxiliary polarity switching means for switching the polarity of the auxiliary electrode, and the auxiliary polarity switching means switches the polarity of the auxiliary electrode at a specified timing in conjunction with the polarity switching means. The mass spectrometer according to claim 5.

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