JP2003202325A - Liquid chromatography mass spectrometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid chromatography mass spectrometer with easy maintenance. <P>SOLUTION: Sample solution is atomized as a charged droplet in an interface 1 with an electrospray (ESI) probe 2 with an applied high voltage to a top end. When mass analysis is not done, a shutter 3 is closed with a shutter opening/closing mechanism 4 and atmosphere air is not entered into a mass analyzer 10 in a decompression state. When the shutter is closed with the shutter opening/closing mechanism 4 and a detector 5 detects that the shutter 3 is closed and sends the signal to a controller 27. The controller 27 opens a ballast valve 27 with a solenoid valve 22 and carries out cleanup in a rotary pump 20. With this control, condensed exhaust gas in the rotary pump 20 can be automatically cleaned up by automatically opening the ballast valve 21 for a fixed time when it is not in analyzing state. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid chromatograph mass spectrometer (hereinafter referred to as LC / MS). 2. Description of the Related Art In LC / MS, a method of ionizing a component separated in a liquid chromatograph under atmospheric pressure and introducing it into a mass spectrometer may be used. In this case, an interface for ionizing the components separated by the column of the liquid chromatograph unit is required. There are several types of interfaces commonly used for LC / MS, such as an electrospray interface (ESI) and an atmospheric pressure chemical ionization interface (APCI). In the ESI method, a liquid sample is sent to the tip of a thin nozzle, and a high voltage is applied to the tip of the nozzle. As a result, a strong non-uniform electric field is formed at the tip of the nozzle, and the liquid sample is sprayed as charged droplets by the strong electric field, and the droplets are further divided by the Coulomb repulsion of the ions in the droplets to ionize. Is performed. On the other hand, in the APCI method, a liquid sample is forcibly sprayed by a gas flow in a nebulizer (atomizer), and the droplet is desolvated by heating the liquid sample. Then, the sample is ionized by buffer ions generated by corona discharge. (Chemical ionization). FIG. 2 is a diagram showing a general configuration of a conventional LC / MS. 31 is a liquid chromatograph unit, 40
Denotes a mass spectrometer. Reference numeral 50 denotes an interface unit. In the figure, an electrospray ionization unit 52 using the ESI method is used. Further, a heater (not shown) is attached to the thin tube 54 provided after the electrospray ionization unit 52, and this heater mechanism is for promoting the desolvation of the charged droplets generated in the electrospray ionization unit 52. Functions as a desolvation means. In the liquid chromatograph unit 31, the sample injected from the sample introduction unit 35 is separated in the column 36 on the flow of the mobile phase 33 sent by the liquid sending pump 34.
The electrospray probe 53 has a pipe through which the sample liquid sent from the liquid chromatograph unit 31 passes. The tip of the electrospray probe 53 on the side facing the thin tube 54 has a needle shape. It is to be spouted from the part. Then, a high voltage of about several KV is applied to the electrospray probe 53 from a high voltage generating circuit (not shown). With such a structure, the liquid sample sent from the liquid chromatograph unit 31 is drawn out in a spray form by a strong electric field formed near the nozzle at the tip of the needle. At this time, a part of the liquid sample is ionized. And into the thin tube 54 as charged droplets. [0005] The charged droplets are heated by the heater in the thin tube 54 to evaporate the solvent, collide with other particles, etc., and are further miniaturized to promote ionization.
The generated ions are extracted from the thin tube 54 and sent to the mass analyzer 40. [0006] In this way, ions are introduced into the mass spectrometer 40 after desolvation and ionization are promoted when passing through the thin tube 54. The mass analyzer 40 is depressurized by a rotary pump 44, and further depressurized by turbo molecular pumps 45 and 46. The ionized sample introduced into the mass spectrometer 40 maintained in such a reduced pressure state is converged and detected by the lens effect of the converging lens 42 and the quadrupole rod 43. On the other hand, when performing ionization by the APCI method, an atmospheric pressure chemical ionization unit 60 as shown in FIG. 3 is attached instead of the electrospray ionization unit 52 of FIG. That is, a probe 62 having a pipe through which a sample liquid passes and having a needle-like tip, an atomization chamber 61 provided so as to surround the needle portion of the probe 62, and a discharge electrode 63 attached to the front surface of the opening of the atomization chamber Is attached. The atomization chamber 61 is heated by a heater (not shown), and a voltage of several KV is applied to the discharge electrode 63. In this way, the liquid sample sent from the liquid chromatograph unit 31 is supplied to the probe 62 by atomizing gas from a gas line separately connected to the probe.
Is sprayed into the atomization chamber 61 from the nozzle at the tip of the needle,
After being desolvated by the heater, it is ionized by contact with buffer ions generated at the discharge electrode. Then, the generated ions and charged droplets are transferred to the heated thin tube 5.
4 and sent to the mass spectrometer 40 while desolvation and ionization are promoted in the same manner as in the ESI method described above. [0008] In the conventional LC / MS, elution was carried out from the column regardless of whether it was in the electrospray ionization section, the atmospheric pressure chemical ionization section, or provided with another ionization section. The mobile phase solvent containing the sample is converted into droplets at the interface, ionized, and then introduced into the mass spectrometer. In any of the ionization methods, a desolvation step of the mobile phase solvent is included in the interface portion, but it is difficult to completely remove the solvent. If the desolvation is not sufficient, the solvent will be condensed in the rotary pump after being introduced into the mass spectrometer, thereby deteriorating the oil and reducing the exhaust capacity. For this reason, the gas ballast valve attached to the rotary pump must be manually opened each time to clean up the pump, which requires time and cost for maintenance. [0009] The present invention has been made to solve the above problems, and has as its object to provide a liquid chromatograph mass spectrometer which is easy to maintain. [0010] In order to solve the above problems, a liquid chromatograph mass spectrometer of the present invention comprises a liquid chromatograph section and a liquid chromatograph mass spectrometer having a rotary pump. Liquid chromatograph mass equipped with an interface unit for ionizing the liquid sample sent from the graph unit by means of ionization and introducing the generated ions or charged droplets to the mass spectrometry unit while desolvating by means of desolvation means In the analyzer, a thin tube portion for spraying and ionizing the liquid sample into the interface portion and introducing the liquid sample into the mass spectrometry portion is provided, and a shutter that can be opened and closed is provided at the end of the thin tube portion on the interface side. Is provided. Further, a ballast valve that can be opened and closed is provided in the rotary pump of the mass spectrometry unit, means for opening and closing the ballast valve is provided, and means for controlling the opening and closing of the ballast valve by a signal obtained from the means for detecting the opening and closing of the shutter. Is provided. The means for opening and closing the shutter may be manual or an electromagnetic valve. A detector such as a micro switch can be used as a means to detect the opening and closing of the shutter, and when the detector detects the opening, the ballast valve is closed and normal exhaust is performed, and then the shutter opening and closing detector detects the closing At this point, the ballast valve is controlled to open for a certain period of time. However, if the detector that detects the opening and closing of the shutter again detects the opening, the control is performed so that the ballast valve is closed immediately. As a means for opening and closing the ballast valve, an electromagnetic valve can be used. With such a control, the exhaust gas condensed in the rotary pump can be cleaned up by automatically opening the ballast valve for an appropriate time during a period in which no analysis is performed. In addition to the above control, if the time during which the shutter is open is shorter than a predetermined time, control is performed so that the ballast valve does not open. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a liquid chromatograph mass spectrometer according to the present embodiment. As shown in the figure, an interface unit 1 includes an electrospray (ESI) probe 2, a shutter 3, a shutter opening / closing device 4, and a detector 5 for detecting opening and closing of the shutter.
, A CDL thin tube 6 which is a thin tube portion, a drain 7, a block heater 8 and a chip 9. The mass analyzer 10 includes a Q array 11a, 11b, 11c, a skimmer 12, an octapole 13, and a focus lens 1.
4, an entrance lens 15, a pre-rod 17, a quadrupole rod 18, a detector 19, a rotary pump 20 and turbo molecular pumps 24 and 25.
The rotary pump 20 is provided with a ballast valve 21 and an electromagnetic valve 22 for opening and closing the ballast valve 21. Further, a control unit 27 that controls the operation of the electromagnetic valve 22 based on a signal from the detector 5 is provided. The sample solution eluted from the liquid chromatograph (LC) is sprayed into the interface 1 as charged droplets by an electrospray (ESI) probe 2 having a high voltage applied to its tip. When mass spectrometry is not performed, the shutter 3 is closed by the shutter opening / closing device 4, and the air does not flow into the mass spectrometer 10 in a reduced pressure state. At this time, the sprayed and ionized sample ions are discharged from the drain 7. In this embodiment, the shutter opening / closing device 4 manually opens and closes the shutter 3. At this time,
The detector 5 detects that the shutter 3 is closed, and sends a signal to the control unit 27. In this embodiment, a microswitch is used for the detector 5. When performing mass spectrometry,
The shutter 3 is opened by the shutter opening / closing device 4.
At this time, the sprayed and ionized sample is introduced into the CDL capillary 6 via the chip 9. The solvent is evaporated by being heated by the block heater 8 in the ionized CDL thin tube 6, and is further miniaturized by collision with other particles to promote ionization.
It is pulled out from the DL capillary 6 and sent to the mass spectrometer 10. The neutral solvent heated and evaporated in the CDL thin tube 6 is exhausted by the rotary pump 20. These exhaust gases condense in the rotary pump 20. The sample ions introduced into the mass spectrometer 10 are Q arrays 11a, 11b, 11c arranged in a tapered shape.
And converge on the central skimmer 12. The sample ions passing through the skimmer 12 are further converged by the octapole 13, pass through the focus lens 14 and the entrance lens 15, and then pass through the pre-rod 17 and the quadrupole rod 1.
At 8, mass separation is performed and detected by the detector 19. The mass analyzer 10 is kept at reduced pressure by a rotary pump 20 and turbo molecular pumps 24 and 25. The rotary pump 20 is provided with a ballast valve 21. An electromagnetic valve 22 is provided at the outlet of the ballast valve 21, and opens and closes the ballast valve 21. The solenoid valve 22 is controlled by the control unit 27. When the ballast valve 21 is open, the exhaust capacity decreases,
When mass spectrometry is performed and the shutter 5 is detected to be open by the detector 5, the control unit 27 closes the ballast valve 21 by the electromagnetic valve 22, the analysis ends, and the shutter opening / closing device 4 controls the shutter. 3 is closed, the detector 5 detects that the shutter 3 is closed, and sends a signal to the control unit 27.
The ballast valve 21 is opened with the rotary pump 2
Clean up within 0. With such a control, the exhaust gas condensed in the rotary pump 20 can be automatically cleaned up by automatically opening the ballast valve 21 for a proper time during a period in which the analysis is not performed. After detecting that the shutter 3 is closed by the detector 5, the control unit 27 opens the ballast valve 21 by the solenoid valve 22, and then the shutter 5 is opened again by the detector 5 without a fixed time. When it is detected that the electromagnetic wave is detected, the control unit 27 closes the solenoid valve 22 so as not to hinder the analysis. When the time during which the shutter 3 is open is short, a method of omitting the operation of opening the solenoid valve 22 can be adopted. If the time during which the mass spectrometry is being performed is short, it is not necessary to clean up the rotary pump 20 every time the analysis is completed, so the detector 5 detects that the shutter 3 is open. The control unit 27 controls the control unit 27 to open the ballast valve 21 by the electromagnetic valve 22 when the integrated value reaches a certain time, and controls the rotary pump 20 to clean up. You may. Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various changes may be made within the scope of the present invention described in the appended claims. be able to. For example, as a means for detecting the opening and closing of the shutter 3, a vacuum gauge such as a Pirani gauge is provided near the rotary pump 20 in the mass spectrometer 10 because the degree of vacuum is lower when the shutter 3 is normally open than when it is closed. It is also possible to detect the opening and closing of the shutter 3 from a change in the degree of vacuum by installing the shutter. According to the present invention, a shutter is provided in a thin tube section for introducing an ionized sample from the interface section to the mass spectrometry section, and the opening and closing of the shutter is detected. Since the opening and closing of the ballast valve is controlled and the cleanup inside the rotary pump can be automatically performed, maintenance can be performed very easily.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram of one embodiment of a liquid chromatograph mass spectrometer of the present invention. FIG. 2 is a schematic configuration diagram of a conventional liquid chromatograph mass spectrometer using the ESI method. FIG. 3 is a schematic configuration diagram of an interface section of a conventional liquid chromatograph mass spectrometer using the APCI method. [Description of Signs] 1 --- Interface unit 2 --- ESI probe 3 --- Shutter 4 --- Shutter opening / closing device 5 --- Detector 6 --- CDL capillary 8 --- Block heater 9-- -Mass analysis unit 20 --- Rotary pump 21 --- Ballast valve 22 --- Solenoid valve 27 --- Control unit

Claims (1)

Claims: 1. A liquid sample sent from a liquid chromatograph section is ionized between a liquid chromatograph section and a mass spectrometry section having a rotary pump by means for ionizing the liquid sample. In a liquid chromatograph mass spectrometer equipped with an interface for introducing the ions or charged droplets into the mass spectrometer while desolvating the ions or charged droplets by the desolvation means, a liquid sample is sprayed on the interface,
A thin tube portion for ionization and introduction into the mass spectrometric unit is provided, a shutter that can be opened and closed is provided at the interface side end of the thin tube portion, and a means for opening and closing the shutter and a means for detecting opening and closing are provided. A ballast valve that can be opened and closed is provided, and a means for opening and closing the ballast valve is provided, and a means for controlling the opening and closing of the ballast valve by a signal obtained from a means for detecting the opening and closing of the shutter is provided. Liquid chromatograph mass spectrometer.