JP4407486B2 - Time-of-flight mass spectrometer - Google Patents

Description

  The present invention relates to a time-of-flight mass spectrometer.

  The structure and operation of a conventional time-of-flight mass spectrometer will be described with reference to FIG. An ion source 31, an ion accelerator 32 and an ion detector 33 are provided at one end in the vacuum chamber 30, and a reflectron (ion reflector) 34 is provided at the other end. As the ion source, a sample ionization unit such as MALDI (Matrix Assisted Laser Desorption / Ionization) or an ion introduction unit such as LCMS is used. A vacuum pump 35 such as a turbo molecular pump capable of achieving a high vacuum is connected to the vacuum chamber 30.

Ions generated by the ion source 31 are given kinetic energy by a predetermined acceleration voltage in the ion accelerator 32 and fly in the flight space 37 toward the reflectron 34. The ions are reflected by the gradient electric field in the reflectron 34, return to the flight space 37, and detected by the ion detector 33. Since the time required for the ions to travel back and forth in the flight space 37 depends on the mass of the ions ( strictly, m / z, where z is a charge), the amount of ions detected by the ion detector 33 is continuously measured. A mass spectrum of ions generated in the ion source 31 is obtained. There is a one-way type in which an ion accelerator and an ion detector are arranged at both ends, and detection is performed after ions fly in only one direction in the flight space.

In such an apparatus, even if the same energy is given, the flight time of ions naturally changes according to the flight distance. Therefore, when the positional relationship of the ion optical system including the ion accelerator 32, the flight space 37, the reflectron 34, the ion detector 33, and the like, in particular, the length of the flight space 37 changes, the ion detector even if the ions have the same mass . The time to reach 33 is shifted and the mass axis of the measured spectrum is shifted. Therefore, the entire vacuum chamber 30 is housed in a thermostatic chamber 36 covered with a heat insulating material 38, and control is performed so that the temperature of the ion optical system becomes constant during measurement.

  The time stability required for a high-performance time-of-flight mass spectrometer is normally about 20 ppm. However, if the time-of-flight deviation due to the change in the length of the flight space 37 is to be reduced below this, the vacuum chamber 30 Even if it is made of a material with a low coefficient of thermal expansion (usually stainless steel is used), the temperature change must be about 1 ° C. On the other hand, some commercially available time-of-flight mass spectrometers have an ion flight space 37 of about 1 m, so that the thermostatic chamber 36 that accommodates the entire vacuum chamber 30 that contains the ion flight space 37 is considerably large. I cannot help it. In order to control such a large thermostatic chamber 36 with an allowable width of 1 ° C. or less, it is necessary to make the thermal capacity of the thermostatic chamber 36 considerably large and to provide a highly accurate temperature control device.

  So, to solve such problems. As shown in FIG. 4, a tubular part (flight tube) 40 constituting a flight space 37 is provided in a vacuum chamber 30, a reflectron 34 is provided at one end of the flight tube 40, and an ion accelerator 32 and an ion detector are provided at the other end. 33 is fixed, and the flight tube 40 is held in the vacuum chamber 30 with a material 41 having a low thermal conductivity, whereby a change in mass spectrum due to thermal expansion of the ion optical system can be reduced. An apparatus has been developed (Patent Document 1). Since both the ion accelerator 32 and the ion detector 33 are fixed to the flight tube 40, the length of the ion flight space 37 between them (the flight distance of ions) depends on the length of the flight tube 40. Since the flight tube 40 is held inside the vacuum chamber 30 through the holding member 41 made of a low thermal conductivity material as described above, it is hardly affected by heat transfer from the air from the vacuum chamber 30. Since it is hardly affected by the heat conduction through the holding member 41, even if the temperature fluctuation range of the thermostatic chamber 36 surrounding the vacuum chamber 30 is somewhat large, the temperature fluctuation of the flight tube 40 inside the vacuum chamber 30 is suppressed. Can do.

JP 2003-151488 A

However, in the time-of-flight mass spectrometer as described above, although the propagation of heat due to heat conduction and convection can be suppressed, the constant temperature by switching on / off of the temperature adjusting heater 42 provided in the constant temperature bath 36 is used. In some cases, a minute temperature change in the tank 36 is transmitted to the ion optical system as radiant heat through the vacuum chamber 30 and a stable mass spectrum cannot be obtained.
Therefore, the problem to be solved by the present invention is to reduce the radiant heat to the ion optical system through the vacuum chamber due to a minute temperature change in the thermostat, stabilize the temperature in the vacuum, and improve the reproducibility of mass spectrometry. It is to provide a time-of-flight mass spectrometer that can be improved.

  A time-of-flight mass spectrometer according to the present invention, which has been made to solve the above-mentioned problems, sandwiches a thermostat bath provided with a temperature control means having a heater, and an ion flight space held and contained in the thermostat bath. In the time-of-flight mass spectrometer equipped with a vacuum chamber provided with at least an ion accelerator and an ion detector, the outer wall of the vacuum chamber is covered with a heat insulating material.

In addition, the mass spectrometer according to the present invention includes a thermostat equipped with a temperature control means having a heater, a vacuum chamber held in the thermostat, and a holding member made of ceramic or resin inside the vacuum chamber. In a time-of-flight mass spectrometer equipped with a flight tube in which at least an ion accelerator and an ion detector are fixed with an ion flight space held in between, the outer wall of the vacuum chamber is covered with a heat insulating material It may be characterized by that.

  In addition, if the entire outer wall of the vacuum chamber is covered with the above heat insulating material, the stability of temperature can be increased, but the time-of-flight mass spectrometer of the present invention is set at a predetermined operating temperature (mass analysis is performed before starting mass analysis). It takes a lot of time to heat up to the temperature when performing. Therefore, in order to prevent a minute heating time required at the time of starting the apparatus from being prolonged while suppressing a minute temperature change in the thermostatic chamber due to the heater on / off being transmitted to the vacuum chamber, the heat insulating material is used for the heater. It is desirable to provide it only in a partial region of the vacuum chamber outer wall in the vicinity. In general, as shown in FIGS. 3 and 4, the vacuum chamber includes an acceleration / detection unit provided with an ion accelerator 32 and an ion detector 33 (however, in the case of the above-described one-way type, the acceleration unit and the detection unit are detected. 30a and a flight separation unit 30b that includes a flight space 37 between the ion accelerator 32 and the ion detector 33. Generally, the space in the thermostat 36 is For this reason, the temperature adjusting heater 42 is often provided in a region close to the flight separation unit 30b. Therefore, in this case, it is desirable to provide the heat insulating material only on the outer wall of the flight separation unit 30 b of the vacuum chamber 30.

  In the above-mentioned “vacuum chamber (or flight tube) in which at least the ion accelerator and the ion detector are fixed across the ion flight space”, the ion accelerator is provided at one end of the vacuum chamber or the flight tube, and the ion detector is provided at the other end. In addition to the one-way type in which a vacuum chamber or a flight tube is provided, an ion accelerator and an ion detector are provided at one end and an ion reflector is provided at the other end. Further, a multiple reciprocating type in which ions reciprocate in the flight space via a plurality of ion reflectors is also included.

  As described above, the outer wall of the vacuum chamber is covered with a heat insulating material to prevent a minute temperature change of the thermostat from being transmitted to the vacuum chamber, thereby preventing a temperature change of the ion optical system due to radiant heat from the vacuum chamber. be able to. For this reason, the distance between the ion accelerator and the ion detector becomes very stable, and the accuracy of reproducibility of mass spectrometry can be improved.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to examples.

[Example]
FIG. 1 shows a schematic configuration diagram of a reciprocating time-of-flight mass spectrometer which is an embodiment of the present invention. In this embodiment, an ion accelerator 12 and an ion detector 13 are provided at one end of a flight tube 20 held in the vacuum chamber 10, and a reflectron 14 is provided at the other end of the flight tube 20. The holding member 21 that holds the flight tube 20 is made of a low thermal conductivity material (for example, ceramic or resin). The ion source (not shown) may be fixed to the flight tube 20 or may be fixed to the vacuum chamber 10 independently of the flight tube 20.

  The vacuum chamber 10 is housed in a thermostatic chamber 16 covered with a heat insulating material 18, and the thermostatic chamber 16 is provided with a temperature adjusting device including a heater 22, a fan 23, a temperature sensor 24, and the like. In the vacuum chamber 10, the outer wall portion of the flight separation unit 10 b is covered with a heat insulating material 27. The vacuum pump 15 provided in the vacuum chamber 10 and the temperature adjusting device provided in the thermostat 16 are controlled by an operation control unit 25 including a computer. Separately from this, a measurement control unit 26 is also provided, which is connected to the ion accelerator 12 and the ion detector 13 (and an ion source not shown) and performs mass analysis of the sample.

  As described above, the time-of-flight mass spectrometer of the present embodiment has a configuration in which changes in the external temperature are not easily transmitted to the flight tube 20. On the contrary, this causes the temperature raising time to be prolonged. Therefore, in the mass spectrometer of the present embodiment, the operation control unit 25 controls to start heating the thermostatic chamber 16 at the start, and to start evacuation in the vacuum chamber 10 after a predetermined time has elapsed. Is desirable. Thereby, the heat of the thermostatic chamber 16 is given to the flight tube 20 from the vacuum chamber 10 by conduction accompanied by air convection when the apparatus is started, and the flight tube 20 can rise to a predetermined temperature relatively quickly. The “predetermined time” includes a time point when the evacuation of the vacuum chamber 10 is completed and a time point when the flight tube 20 reaches a predetermined operation temperature (usually set to a value 5 to 10 ° C. higher than room temperature). Although it is desirable to set the time so that it is almost the same time, it may be after the time when the flight tube 20 is considered to have reached the operating temperature. Alternatively, instead of determining by time, evacuation may be started when the thermostatic chamber 16, the vacuum chamber 10 or the flight tube 20 reaches a predetermined temperature (the operation temperature or a temperature close thereto). Good.

  Thereafter, when the temperature in the thermostatic chamber 16 detected by the temperature sensor 24 reaches the above operating temperature, and the degree of vacuum in the vacuum chamber 10 detected by a vacuum gauge (not shown) reaches a predetermined value, Mass analysis of the sample is started under the control of the measurement control unit 26. During the analysis, the operation controller 25 controls the temperature in the thermostatic chamber 16. At this time, heat is transferred from the vacuum chamber 10 to the flight tube 20 by conduction and convection by the holding member 21 made of a low heat transfer coefficient material and by vacuum. In addition, the heat insulating material 27 provided on the outer wall of the vacuum chamber 10 suppresses thermal fluctuations in the vacuum chamber 10 due to minute temperature changes in the thermostatic bath 16, and the vacuum chamber 10 to the flight tube 20 due to radiant heat. It is also possible to suppress the heat transfer. Therefore, the temperature fluctuation of the thermostatic chamber 16 affects the temperature fluctuation of the flight tube 20 only with a very long time constant. Thereby, the temperature fluctuation range of the flight tube 20 can be suppressed more than before, and a stable mass spectrum can be obtained.

  As described above, the best mode for carrying out the present invention using the reciprocating time-of-flight mass spectrometer which is an embodiment of the present invention has been described. However, the present invention is not limited to this, and the present invention is not limited thereto. Within the range, various changes are allowed. For example, in the above embodiment, an example in which the present invention is applied to a time-of-flight mass spectrometer having a flight tube inside a vacuum chamber has been described. However, as shown in FIG. The present invention may be applied to a time-of-flight mass spectrometer of the type in which the ion accelerator 12, the ion detector 13, and the reflectron 14 are fixed. In the above-described embodiment, the reciprocating type has been described. Of course, the present invention can be applied to a unidirectional type in which an ion detector is placed at the position of the reflectron.

1 is a schematic configuration diagram of a reciprocating time-of-flight mass spectrometer that is an embodiment of the present invention. The schematic block diagram which shows another example of the time-of-flight mass spectrometer of this invention. 1 is a schematic configuration diagram of a conventional reciprocating time-of-flight mass spectrometer. 1 is a schematic configuration diagram of a conventional reciprocating time-of-flight mass spectrometer equipped with a flight tube.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 30 ... Vacuum chamber 10b, 30b ... Flight separation part 11 ... Ion source 12, 32 ... Ion accelerator 13, 33 ... Ion detector 14, 34 ... Reflectron 15, 35 ... Vacuum pump 16, 36 ... Constant temperature bath 17, 37 ... Ion flight space 18, 38, 27 ... Insulation material 20, 40 ... Flight tube 21, 41 ... Holding member 22, 42 ... Heater 23, 43 ... Fan 24, 44 ... Temperature sensor 25, 45 ... Operation control unit 26, 46. Measurement control unit

Claims (5)

A time-of-flight type comprising a thermostat equipped with a temperature control means having a heater, and a vacuum chamber provided with at least an ion accelerator and an ion detector sandwiching an ion flight space contained in the thermostat and enclosing it In the mass spectrometer,
A time-of-flight mass spectrometer characterized in that an outer wall of the vacuum chamber is covered with a heat insulating material. A thermostat equipped with a temperature control means having a heater, a vacuum chamber held in the thermostat, and an ion flight space held and contained in the vacuum chamber via a holding member made of ceramic or resin. In a time-of-flight mass spectrometer equipped with a flight tube having at least an ion accelerator and an ion detector fixed therebetween,
A time-of-flight mass spectrometer characterized in that an outer wall of the vacuum chamber is covered with a heat insulating material.   The time-of-flight mass spectrometer according to claim 1 or 2, wherein the heat insulating material is provided only in a partial region of the outer wall of the vacuum chamber near the heater.   The time-of-flight mass spectrometer according to any one of claims 1 to 3, wherein the heat insulating material is provided only on the outer wall of the flight separation unit of the vacuum chamber.   2. The reciprocating time-of-flight mass spectrometer in which the ion accelerator and the ion detector are provided at one end in the apparatus and an ion reflector is provided at the other end. 5. A time-of-flight mass spectrometer according to any one of 4 above.

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