JP5663725B2 - Sample introduction device for mass spectrometer - Google Patents

Description

  The present invention relates to a sample introduction device for a mass spectrometer, and more particularly to a sample introduction device for a mass spectrometer that atomizes a sample with an ultrasonic sound source.

  It has been pointed out that foods such as vegetables, cereals, and processed foods have recently been contaminated with contaminants such as agricultural chemicals, insecticides, antibiotics, environmental hormones, dioxins, surfactants, and plastic additives. Has been. There are various difficulties when analyzing pollutants. A sample to be analyzed (qualitative, quantitative analysis, etc.) usually contains a plurality of test components. Many of these contaminants are organic compounds. And even if these organic compounds have a similar molecular structure, the toxicity is often greatly different. Therefore, when performing analysis, it is necessary to separate a plurality of test components individually and identify each of them.

  It is also desired to analyze what beneficial components are contained in food, for example, organic acids such as vitamins, peptides, saccharides, amino acids, and fatty acids, and biological substances such as proteins. Biologically related substances are not limited to foods, but are also included in blood and body fluids, body tissues, and the like of human bodies and animals, and therefore human bodies and animals can also be samples to be analyzed.

  Mass spectrometry is widely used to identify such test components. When applying mass spectrometry, a sample often contains a plurality of test substances as described above, so a gas chromatograph (GC) or liquid chromatograph (LC) is used before mass analysis. Mass spectrometry is performed after each test component is separated and ionized.

  More specifically, in the case of GC, a liquid sample containing a test component is gasified by heating and then introduced into a separation column using a carrier gas to separate each test component. Each test component is then ionized by, for example, an electron impact method, and the ions are subjected to mass analysis.

  In the case of LC, a liquid sample containing test components is introduced into a separation column using a carrier solvent, and each test component is separated. The carrier solvent containing each test component is gasified and ionized, and the ions are subjected to mass spectrometry. At this time, since it is necessary to gasify a large amount of the carrier solvent, before heating and gasifying, the carrier solvent containing the test component is made into fine droplets (atomized), for example, with a nebulizer or the like. For example, it is gasified by heating to about 200 ° C to 500 ° C.

  Here, what atomizes uses the ultrasonic vibration. Compared to nebulizer atomization, atomization using ultrasonic vibration generally has the advantage that the particle size of the droplets can be made relatively small and the particle size is uniform. For example, Patent Document 1 discloses an ion source that ionizes a test component before mass-analyzing a carrier solvent containing each test component processed by LC. This ion source has an ultrasonic atomizing section, and atomizes a liquid sample by atomizing a liquid jet nozzle by ultrasonic vibration and applying a high voltage to the liquid jet nozzle. Is charged. Then, the charged droplets and the heated nitrogen gas are mixed, mixed, and ejected in a mixed manner to further refine the droplets.

JP-A-6-310088

  However, in the heat treatment during the separation or gasification of the test component as described above, there is a possibility that the heat unstable component or the hardly volatile component is decomposed by heat. For this reason, in conventional techniques, for example, in order to analyze organic acids such as amino acids and fatty acids, vitamins, peptides, saccharides, surfactants, and other thermally unstable components and hardly volatile components, it is relatively difficult to perform separation processing. After separating the test components by using LC that can be used in a low temperature range, the test components including the carrier solvent are gasified using a nebulizer or ultrasonic vibration and detected by a mass spectrometer. ing. On the other hand, since separation processing such as LC is necessary, the analysis operation involves a lot of time and troublesome operations, so that it is a conventional technology to meet the need to quickly analyze thermally unstable components and hardly volatile components. It was difficult.

  In the case of mass analysis of a liquid sample with no separation treatment for a thermally unstable component or a hardly volatile component, use the apparatus of Patent Document 1 or an electrospray ionization method that has an ultrasonic atomization unit that can form microdroplets. Can be considered. However, in the apparatus and the electrospray ionization method of Patent Document 1, since a droplet is charged by applying a high voltage, the test component easily generates multivalent ions, and the generated ions are also proton adducts, alkali metal ions. When adducts are mixed, the mass spectrum becomes complicated. For this reason, analysis without separation processing becomes difficult. Moreover, in order to simultaneously gasify a large amount of liquid as a carrier solvent together with the test component, a large amount of heat energy is required, and the thermally unstable component may be decomposed by this heat energy.

  In addition, atomization is performed by bringing a liquid sample into direct contact with the ultrasonic vibration surface without using a carrier solvent, thereby minimizing the heat energy required for gasification and massing the gasified test component by the carrier gas. A device that transports to an analytical device can also be envisaged. However, in this case, a part of the test component may remain attached to the ultrasonic vibration surface. This remaining component to be tested can cause contamination problems the next time another sample is analyzed. In order to avoid contamination, it is necessary to separately perform a cleaning operation, but this complicates the analysis process and the analysis apparatus. In addition, since the cleaning process requires time, it becomes difficult to meet the demand for quick analysis.

  In view of such circumstances, the present invention is intended to provide a sample introduction device for a mass spectrometer capable of gasifying a thermally unstable component and a hardly volatile component at a relatively low temperature while suppressing decomposition. is there.

  In order to achieve the above-described object of the present invention, a sample introduction device for a mass spectrometer according to the present invention includes a vibrator, a vibration transmission unit connected to the vibrator, and a vibrator of the vibration transmission unit. A diaphragm connected to the opposite side to the opposite side, and a reflector provided in parallel with the diaphragm, and providing at least one node of a standing wave sound field between the diaphragm and the reflector An ultrasonic sound source unit configured to atomize a solution passing through a node of the standing wave sound field, and at least one of a standing wave sound field between a diaphragm and a reflector of the ultrasonic sound source unit In one section, a sample introduction part for introducing a sample solution, a gasification part for gasifying the sample atomized by the ultrasonic sound source part, and a carrier gas for transporting the sample gasified by the gasification part And a gas supply unit for supplying the gas.

  Furthermore, what is necessary is just to comprise the ionization part which ionizes the sample gasified by a gasification part.

  Furthermore, what is necessary is just to comprise the ion source part which generates ion.

  Here, the ion source unit may supply ions to the sample after gasification by the gasification unit, and the ionization unit may ionize the sample after gasification.

  The ion source unit may supply ions to the sample before being gasified by the gasification unit, and the ionization unit may ionize the sample when it is gasified.

  In addition, the ultrasonic sound source unit may be any one in which the vibrator is a bolted Langevin type vibrator, the vibration transmitting part is an exponential horn and a half-wave resonator, and the diaphragm is a rectangular flexible diaphragm. .

  In the ultrasonic sound source unit, the distance between the vibration plate and the reflection plate is ½ wavelength of the resonance frequency of the ultrasonic sound source unit, and the sample introduction unit introduces the sample to the center between the vibration plate and the reflection plate. I need it.

  The sample introduction device for a mass spectrometer of the present invention has an advantage that a thermally unstable component and a hardly volatile component can be gasified while suppressing decomposition at a relatively low temperature.

FIG. 1 is a schematic configuration diagram for explaining a sample introduction device for a mass spectrometer according to the present invention. FIG. 2 is a schematic configuration diagram for explaining a sample introduction device for a mass spectrometer according to another embodiment of the present invention.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram for explaining a sample introduction device for a mass spectrometer according to the present invention. The sample introduction device for a mass spectrometer is used for introducing a sample containing a test component into the mass spectrometer, and as shown in the drawing, the sample introduction device for a mass spectrometer of the present invention is an ultrasonic sound source. The unit 10, the sample introduction unit 20, the gasification unit 30 and the gas supply unit 2 are mainly configured. These are assembled to the housing 1.

  The ultrasonic sound source unit 10 atomizes the solution in a non-contact manner. Here, in order to perform ultrasonic atomization, the ultrasonic sound source unit 10 provides a strong sound field. Further, since the ultrasonic sound source unit 10 applied to the sample introduction device for the mass spectrometer is used for atomizing the sample solution from the sample introduction unit 20, it is powerful only at the point where the solution in the housing 1 is introduced. It is only necessary to provide a sound field. Therefore, for example, a conventional point-focusing type ultrasonic sound source is unsuitable for application in such applications because the apparatus is large. In addition, since the fringe mode flexural diaphragm type ultrasonic sound source can provide a powerful aerial sound field in combination with a reflector, it is applicable to the sample introduction device for a mass spectrometer of the present invention. Since the area of the flexure diaphragm is large, there is a possibility that the apparatus will become large when applied to a sample introduction apparatus.

  In the sample introduction device for a mass spectrometer of the present invention, the ultrasonic sound source unit 10 includes a vibrator 11, a vibration transmission unit 12, a vibration plate 13, and a reflection plate 14. The vibration transmission unit 12 is connected to the vibrator 11. The diaphragm 13 is connected to the side of the vibration transmitting unit 12 opposite to the side to which the vibrator 11 is connected. The reflector 14 is provided to face the diaphragm 13 in parallel. The ultrasonic sound source unit 10 is configured to provide at least one node of the standing wave sound field between the diaphragm 13 and the reflecting plate 14, and atomizes the solution passing through the node of the standing wave sound field. It is. Specifically, for example, the vibrator 11 is a bolted Langevin type vibrator. Moreover, the vibration transmission part 12 consists of the exponential horn 12a and the half wavelength resonance rod 12b. An example of the exponential horn 12a is made of duralumin and has an amplitude expansion ratio of about 5.0. Further, the half-wave resonator rod 12b may be made of, for example, duralumin. Note that the resonance frequency can be adjusted by adjusting the length of the half-wave resonance rod 12b. The diaphragm 13 is a rectangular flexible diaphragm. The diaphragm 13 may also be a duralumin plate. The reflection plate 14 may be any plate as long as it can reflect ultrasonic waves, and may be a plate made of duralumin, for example. And it is comprised so that a standing wave sound field may be produced | generated in the meantime by adjusting the distance between the diaphragm 13 and the reflecting plate 14. FIG. It is sufficient that at least one node of the standing wave sound field is provided between the diaphragm 13 and the reflector 14. Specifically, the diaphragm 13 and the reflector 14 may be arranged so that the distance between the diaphragm 13 and the reflector 14 is n · λ / 2 (n is a natural number). For example, when n = 1, a standing wave sound field is generated between the diaphragm 13 and the reflector 14, and one node is formed at the center thereof. When n = 2, two nodes are formed.

  Using the ultrasonic sound source unit 10 configured as described above, each dimension may be adjusted so that a strong standing wave sound field is generated between the diaphragm 13 and the reflector 14. For example, when the resonance frequency is 28 kHz, the half-wave resonance rod 12b may have a length of 76 mm and a diameter of 8 mm, for example. Moreover, the dimension of the diaphragm 13 should just be a board of length 45mm, width 25mm, and thickness 3mm, for example. At this time, if the distance between the diaphragm 13 and the reflecting plate 14 is 6.5 mm, the wavelength becomes ½ wavelength and one node can be centered. Moreover, if it is set to 13 mm, it will become a standing wave sound field of 1 wavelength, and two nodes will be made.

  Note that the present invention is not limited to the specific configuration of the ultrasonic sound source unit 10 described above. In the sample introduction device for a mass spectrometer according to the present invention, the supersonic wave is configured so that the sound pressure of the standing wave field generated between the diaphragm and the reflector of the ultrasonic sound source is high, and the solution passing therethrough can be atomized. Any configuration may be used as long as it is a sound source.

  The sample introduction unit 20 introduces a sample solution into at least one node of the standing wave sound field between the diaphragm 13 and the reflection plate 14 of the ultrasonic sound source unit 10. The sample introduction unit 20 includes a needle 21 and a needle seal 22 as shown in the figure, for example, and a liquid sample is introduced into the housing 1 through these. The tip of the needle 21 is connected to the node of the standing wave sound field between the diaphragm 13 and the reflector 14 of the ultrasonic sound source unit 10, more specifically, for example, the distance between the diaphragm 13 and the reflector 14 is an ultrasonic wave. In the case of ½ wavelength of the resonance frequency of the sound source, the ultrasonic sound source unit 10 is configured to atomize the solution that passes through the node portion in alignment with the center between the vibration plate 13 and the reflection plate 14.

  When a liquid sample is introduced from the sample introduction unit 20 into the ultrasonic sound source unit 10, the ultrasonic sound source unit 10 atomizes the liquid with a particle size of, for example, 100 μm or less, preferably 30 μm or less. Thereby, the sample can be easily gasified, and the test component contained in the sample can be divided into individual molecules. Then, the sample atomized in this way is moved to the gasification unit 30 by the air flow by the gas supply unit 2 connected to the housing 1. The gas supply unit 2 supplies a carrier gas for transporting the sample gasified by the gasification unit 30. For example, the gas supply unit 2 is connected to the housing 1 via a valve, and introduces a carrier gas such as nitrogen, helium, or air into the housing 1. Further, a valve 3 for introducing purge gas into the housing 1 may be provided. Examples of the purge gas include nitrogen, helium, and air.

  The gasification unit 30 gasifies the sample atomized by the ultrasonic sound source unit 10. The gasification unit 30 includes an insert 31, an O-ring 32, and a heater 33 as shown in FIG. An insert 31 is fixed in the housing 1 via an O-ring 32, and the atomized sample passing through the insert 31 is gasified by being heated by a heater 33. At this time, since the sample is atomized with a fine particle size by the ultrasonic sound source unit 10, the gasification unit 30 can gasify the sample at a relatively low temperature. For example, the heating temperature may be 200 ° C. or lower, more preferably about 80 ° C. to 150 ° C. The gasification unit 30 decomposes the test component contained in the sample into individual molecules.

  Now, the sample gasified by the sample introduction device for a mass spectrometer of the present invention configured as described above is then introduced into the ionization section 40 under reduced pressure as shown in FIG. The ionization part 40 ionizes the sample gasified by the gasification part 30, for example. For example, the ionization unit 40 is connected to an ion source unit 41 that generates ions for ionizing a test component. The ion source unit 41 may be built in the ionization unit 40. In the example of FIG. 1, the ion source unit 41 supplies ions to the sample after being gasified by the gasification unit 30, and ionizes the sample after being gasified in the ionization unit 40. That is, the test component contained in the sample gasified by the gasification unit 30 is introduced into the ionization unit 40 in a state where it is not yet ionized, and the test component is ionized using ions generated from the ion source unit 41. . Alternatively, ionization may be performed by destroying a part (usually proton) of the molecule of the test component by photon energy or the like irradiated from the ion source 41 to the test component.

  The ionization in the ionization unit 40 is performed in order to simplify the mass spectrum obtained in the mass analysis unit 50. This may be performed by, for example, a soft ionization method. More specifically, among the soft ionization methods, a soft ionization method capable of detecting only the quasi-molecular ion spectrum is used. Examples of such soft ionization methods include ionization by ion attachment to the test component, ionization by photoelectron emission from the test component, and ionization by proton transfer reaction to the test component.

  In such a soft ionization method capable of mainly detecting a quasi-molecular ion spectrum, the test component (molecule) is not decomposed into fragments, or is only decomposed into large fragments. For this reason, even if it ionizes a some test component simultaneously, possibility that the ion of the same molecular weight will arise is small. Therefore, individual test components (molecules) can be identified completely or to some extent.

  The test component ionized by the ionization unit 40 in this way is introduced into the mass analysis unit 50, mass analysis is performed, and a mass spectrum or the like is obtained.

  As described above, according to the sample introduction device for a mass spectrometer of the present invention, it is possible to gasify at a relatively low temperature without contact, and therefore it is possible to analyze a thermally unstable component and a hardly volatile component. Further, since the atomization can be performed without contact, the problem of contamination hardly occurs, and the atomization part is not required to be cleaned, and a rapid analysis is possible. In addition, the separation process becomes unnecessary due to soft ionization.

  Next, a sample introduction device for a mass spectrometer according to another embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic configuration diagram for explaining a sample introduction device for a mass spectrometer according to another embodiment of the present invention. In the figure, the parts denoted by the same reference numerals as those in FIG. In the embodiment shown in FIG. 1, the example in which the sample after gasification is ionized has been described. However, the embodiment shown in FIG. 2 is ionized simultaneously when gasified. Hereinafter, a description will be given with reference to FIG.

  In the sample introduction device for a mass spectrometer of the present invention shown in FIG. 2, the carrier gas supplied into the housing 1 by the gas supply unit 2 is introduced into the discharge unit of the ion source unit 44 and applied to the needle electrode. An active chemical species in an ion or excited state is generated by a voltage. That is, the ion source unit 44 supplies ions and excited molecules to the sample before being gasified by the gasification unit 30. The carrier gas and the purge gas from the valve 3 are filled in the housing 1 and moved to the gasification unit 30 together with the sample atomized by the ultrasonic sound source unit 10. In the gasification unit 30, the ions and excited molecules are heated together with the atomized sample, whereby ionization occurs simultaneously with the gasification of the test component. This occurs when ions adhere to the test component contained in the sample or when the test component and the excited molecule react in a gas phase.

  The test component ionized in the gasification unit 30 in this way is directly introduced into the mass analysis unit 50, mass analysis is performed, and a mass spectrum or the like is obtained.

  Thus, in the sample introduction device for a mass spectrometer of the present invention, various ionization methods can be used.

  It should be noted that the sample introduction device for a mass spectrometer of the present invention is not limited to the illustrated examples described above, and it is needless to say that various modifications can be made without departing from the scope of the present invention. In addition, the specific dimensions, temperatures, and the like described above are merely given as examples, and it is clear that the present invention is not limited to these.

DESCRIPTION OF SYMBOLS 1 Housing 2 Gas supply part 3 Valve 10 Ultrasonic sound source part 11 Vibrator 12 Vibration transmission part 12a Exponential horn 12b Half wavelength resonance rod 13 Diaphragm 14 Reflecting plate 20 Sample introduction part 21 Needle 22 Needle seal 30 Gasification part 31 Insert 32 O-ring 33 Heater 40 Ionization part 41 Ion source part 44 Ion source part 50 Mass analysis part

Claims (7)

A sample introduction device for a mass spectrometer for introducing a sample containing a test component into a mass spectrometer, wherein the sample introduction device for a mass spectrometer is
Vibrator and a vibration transmitting portion to be connected to the oscillator, to the side where the vibrator of the vibration transmitting portion is connected to the opposite side connected to the vertical direction and arranged Ru diaphragm parallel to the said vibrating plate opposed to vertically disposed Ru reflector consists, an ultrasonic tone generator configured to provide at least one node of the standing wave field to the diaphragm and the reflecting plates, the standing An ultrasonic sound source that atomizes the solution passing through the nodes of the wave field;
A sample introduction unit for introducing a sample solution vertically downward into at least one node of a standing wave sound field between the diaphragm and the reflection plate of the ultrasonic sound source unit;
A gasification unit for gasifying a sample atomized by the ultrasonic sound source unit;
A gas supply unit for supplying a carrier gas for transporting the sample gasified by the gasification unit;
A sample introduction device for a mass spectrometer, comprising:   2. The sample introduction device for a mass spectrometer according to claim 1, further comprising an ionization unit that ionizes a sample gasified by the gasification unit.   The sample introduction device for a mass spectrometer according to claim 2, further comprising an ion source unit for generating ions.   4. The sample introduction apparatus for a mass spectrometer according to claim 3, wherein the ion source section supplies ions to the sample after gasification by the gasification section, and the ionization section is sampled after gasification. A sample introduction device for a mass spectrometer characterized by ionizing a gas.   The sample introduction device for a mass spectrometer according to claim 3, wherein the ion source unit supplies ions to the sample before being gasified by the gasification unit, and the ionization unit is a sample when gasified. A sample introduction device for a mass spectrometer characterized by ionizing a gas.   The sample introduction device for a mass spectrometer according to any one of claims 1 to 5, wherein the ultrasonic sound source section includes a bolt-clamped Langevin type vibrator, and a vibration transmission section including an exponential horn and A sample introduction device for a mass spectrometer, comprising a half-wave resonance rod, wherein the diaphragm is a rectangular flexible diaphragm.   The sample introduction device for a mass spectrometer according to any one of claims 1 to 6, wherein the ultrasonic sound source unit has a distance between a diaphragm and a reflector at a half wavelength of a resonance frequency of the ultrasonic sound source unit. A sample introduction unit for introducing a sample into a center between a diaphragm and a reflector;