JPH1164282A - Adjustment method of mass spectrometer - Google Patents

Abstract

(57) [Summary] (with correction) [Problem] In a liquid chromatograph / mass spectrometer, capillary electrophoresis / mass spectrometer, and plasma / mass spectrometer, the degree of vacuum inside the ion trap mass spectrometer is sufficiently improved. Until then, there was a drawback that the adjustment of the device could not be started and the device could not be efficiently loaded. SOLUTION: The apparatus parameters are divided into those that cannot be executed until the degree of vacuum inside the ion trap mass spectrometer becomes sufficiently high and those that cannot be executed until the degree of vacuum inside the ion trap mass spectrometer is sufficiently improved. [Effect] The start-up time required for carrying in the apparatus is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid chromatograph / mass spectrometer in which a substance in a solution is separated by a liquid chromatograph, and the separated components are ionized and detected by a mass spectrometer. The present invention also relates to a capillary electrophoresis / mass spectrometer using capillary electrophoresis as a separation means. further,
The present invention also relates to a plasma / mass spectrometer that mass-analyzes ions generated by ionizing a sample in a solution by plasma.

[0002]

2. Description of the Related Art The prior art includes Rapid Communication Mass Spectrometry, No. 6, 1992, 31.
There is a method disclosed on page 3. FIG. 6 shows a configuration of a conventional example for reference. In this method, using a syringe pump, ions generated by an electrospray method, which is an ionization method utilizing an electrostatic spray phenomenon, are introduced into a high vacuum through a differential evacuation unit. At this time, an electrostatic lens is provided in the differential evacuation section to converge the ions, thereby improving the transmittance of the ions in this region. The ions that have passed through the differential evacuation unit are further converged by an electrostatic lens and introduced into an ion trap mass spectrometer including a pair of bowl-shaped end cap electrodes and a donut-shaped ring electrode. The ions introduced into the ion trap mass spectrometer are mass-separated by sweeping the amplitude of the high-frequency voltage applied to the ring electrode, taken out of a pore existing at the center of the end cap electrode, and extracted. Detected by the detector. In this method, since ions are temporarily stored in the ion trap mass spectrometer and then mass separation is performed, there is an advantage that a signal amount particularly when a mass spectrum is measured is greatly improved.

[0003]

In the above prior art, as shown in FIG. 6, the inside of the end cap electrode 11 is filled with a damping gas for converging ions.
a, 11b and the ring electrode 12 are electrically insulated and held for two reasons.
a, 11b and the ring electrode 12, an insulating ring 22
a, 22b. However, in this structure, in order to exhaust the inside of the ion trap mass analyzer surrounded by the end cap electrodes 11a and 11b and the ring electrode 12, once the entire apparatus is exposed to the atmospheric pressure, the end cap electrodes 11a, 11a, Since the gas is exhausted only through the pores for taking in the ions provided in 11b and the narrow holes for extracting the ions, the exhaust efficiency is poor, and it takes a very long time before the measurement can be substantially started. Become.
This is especially true when the disassembled ion trap mass spectrometer is loaded, assembled and evacuated, and the ion source, ion accelerating voltage, ion lens, etc. are adjusted so that measurement can be performed again. It takes a long time, so that it takes a long time to restart the apparatus.

[0004]

In order to solve the above-mentioned problems in the prior art, after starting the evacuation of the apparatus, the vacuum inside the ion trap mass spectrometer among the parameters that need to be adjusted does not completely rise. For those that need to be used (ion source, ion lens, etc.), adjustments are mainly made at that stage, and adjustments are made separately from parameters (such as ion acceleration voltage) that must be reached after the vacuum has completely risen. Shortens the time required for starting up the entire equipment.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. In FIG. 1, an electrospray method using an electrostatic spray phenomenon is used as a method for ionizing a sample molecule in a solution under an atmospheric pressure, but an atmospheric pressure chemical ionization method using a corona discharge and a heated spray are used. The same effect can be obtained by using another atmospheric pressure ionization method such as an atmospheric pressure spray method or a sonic spray ionization method using a high-speed gas flow. A similar effect can be obtained in a plasma / mass spectrometer using inductively coupled plasma or microwave plasma.

FIG. 1 shows a configuration diagram of an ion trap mass spectrometer provided with an electrospray ion source. This device operates as follows. A sample solution introduced from a liquid chromatograph or a syringe pump for separating a mixed sample is sent to a capillary 2 provided in an electrospray ion source 1. This capillary 2
Is applied with a high voltage, and charged micro droplets are generated from the tip of the capillary due to the electrostatic spray phenomenon. The generated charged droplets pass through the first pores 3, the second pores 4, and the skimmer 5 of the differential pumping section heated by the heaters 6a and 6b, and are heated or collided with neutral molecules. It is vaporized and produces ions. Further, a voltage can be applied between the first pore 3 and the second pore 4 and between the second pore 4 and the skimmer 5, so that the ion permeability is improved and the collision with the remaining molecules is achieved. To cleave the cluster. The differential pumping section is usually evacuated by a roughing pump 18 such as a rotary pump, a scroll pump, a mechanical booster pump, or the like. It is also possible to use turbo molecular pumps.

After the generated ions pass through the skimmer 5, they are converged by the electrostatic lens 7. Usually, an Einzel lens, which is a set of three electrodes, is used. After further passing through the slit 8, the ions are deflected by the deflector 9, pass through the gate electrode 10, and are introduced into the ion trap mass spectrometer including the pair of bowl-shaped end cap electrodes 11 a and 11 b and the ring electrode 12. End cap electrode 11
a, 11b and the ring electrode 12 for introducing a damping gas such as helium gas for converging ions in a region surrounded by these electrodes, and after electrically insulating these electrodes. Insulation ring 2 to hold
8a and 28b are provided (see FIG. 2). Usually, the insulating rings 28a and 28b are made of a material such as quartz. The ions are introduced from the ion intake port 23 of the end cap electrode 11a, are collected by a high frequency electric field formed by the high frequency voltage applied to the ring, and are provided on the end cap electrode 11b by scanning the high frequency voltage. Ion extraction pore 31
(See FIG. 5). The slit 8 limits the solid angle of the jet including the microdroplets flowing from the skimmer, and prevents extra microdroplets and the like from being introduced into the ion trap mass spectrometer. The deflector 9 is used in order to prevent microdroplets that have passed through the skimmer from being directly introduced into the ion trap mass analyzer through the pores of the end cap electrode. Here, a double-cylindrical deflector 9 composed of an inner cylinder and an outer cylinder provided with a number of openings is used, and deflection is performed using an electric field of the outer cylinder that has oozed from the openings of the inner cylinder. . The gate electrode 10 serves to prevent external ions from being introduced into the mass analysis unit when the ions stored in the ion trap mass analysis unit are taken out of the system.

[0008] The ions introduced into the ion trap mass spectrometer collide with a gas such as helium introduced into the ion trap mass spectrometer to reduce the trajectory thereof, and then apply a high-frequency voltage applied to the ring electrode. Is scanned out of the system through the ion extraction pores 32 of the end cap electrode 11b,
Through 3 is detected by the ion detector. Gas such as helium is supplied from a source such as a cylinder 26 to the regulator 2.
5 is supplied. In this case, the ion detector converts ions into electrons at the conversion dynode 14, and detects the electrons with a scintillation counter. The obtained signal is amplified by the amplifier 16 and sent to the data processing device 18. The voltage applied to the conversion dynode 14 is applied by the high voltage power supply 17, and by changing the polarity, positive or negative ions can be measured. When the scintillation counter 15 is used for feedthrough for applying a voltage from outside the vacuum, attention must be paid to light leakage from the outside which causes noise in the detector. Here, in order to prevent light from leaking, a polymer material containing a filler such as molybdenum disulfide is used, and a black cover is used.

Normally, the relationship between mass number / charge and ion intensity (mass spectrum) and the time change of ion intensity at a certain mass number / charge (mass chromatogram) are displayed. The chamber in which the electrostatic lens, the slit, the deflector, the gate electrode, the ion trap mass analyzer, and the ion detector are located is evacuated by the turbo molecular pump 22. The turbo molecular pump 22 requires an auxiliary pump on the back pressure side, but it can also be used as the roughing pump 21 used for the differential pumping section. In this embodiment, a scroll pump having an exhaust capacity of about 900 liter / minute is provided in the differential exhaust section, and a 200 liter / minute is used as an exhaust device for the chamber.
A turbo molecular pump for about a second is used, and a scroll pump is also used as an auxiliary pump of the turbo molecular pump. With such a system, the exhaust system of the atmospheric pressure ionization mass spectrometer, which tends to be complicated, can be greatly simplified.

The main instrument parameters for adjusting the entire ion trap mass spectrometer are an ion source, an ion accelerating voltage,
It is divided into four parts: an ion lens and an ion trap mass spectrometer. This reference diagram is shown in FIG.

When the electrospray method utilizing the electrostatic spraying phenomenon is used as the ion source, the voltage applied to the capillary for electrostatically spraying the sample solution, the amount of the auxiliary spray gas flowing around the capillary tip, the capillary Mainly the positional relationship between the tip and the first pore, the voltage between the first pore 3 and the second pore 4 in the differential pumping section, the voltage between the second pore 4 and the skimmer 5 in the differential pumping section, etc. Parameters. When other ion sources are used, the atmospheric pressure chemical ionization method (atomizer temperature for atomizing the sample solution, vaporizer temperature for vaporizing the generated droplets, needle electrode for corona discharge) , A sonic spray method (eg, a spray gas amount for gas-spraying a sample solution), and an atmospheric pressure spray method (eg, an atomizer temperature for heating and spraying a sample solution).

The ion accelerating voltage is for giving energy for driving generated ions into the ion trap mass spectrometer, and is actually a voltage applied to the skimmer 5.

The ion lens is a lens for efficiently transporting the ions that have passed through the skimmer to the ion trap mass analyzer. In FIGS. 1 and 2, ions from the skimmer 5 are converged by an electrostatic lens 7 called an Einzel lens composed of three electrodes and passed through a slit. In this case, ions are introduced into the ion trap mass spectrometer except for neutral particles. Of course, it goes without saying that another lens such as a quadrupole lens or an octapole lens may be used for this part. In the adjustment of the ion lens, the voltage of the electrostatic lens and the voltage of the deflection lens are changed so that the amount of transmitted ions is maximized.

The adjustment of the ion trap mass spectrometer includes adjustment of a high-frequency voltage, a storage time of ions, and a gas pressure of helium or the like introduced into the ion trap mass spectrometer.

Among the above-mentioned apparatus parameters, the ion source and the ion lens can be adjusted to some extent even when the degree of vacuum inside the ion trap mass spectrometer is not sufficiently raised. Based on this idea, the procedure for loading and starting up the device is different from the conventional case shown in FIG.
Will be different.

[0016] As in the prior art, the apparatus is carried in and assembled.
When the vacuum inside the ion trap mass spectrometer is sufficiently improved (at least one hour from the start of evacuation), it is attempted to adjust the ion source, ion acceleration voltage, ion lens, and device parameters of the ion trap mass spectrometer. ,
On the first day of carrying in the equipment, carry it in to the place of use of the equipment,
After assembling the apparatus, it is necessary to wait several hours or more until the inside of the ion trap mass spectrometer is sufficiently exhausted. Therefore, the adjustment of the apparatus is practically the second day. In this case, if there is a plurality of ion sources to be adjusted, the adjustment becomes more difficult.

On the other hand, according to the procedure of the present invention, after the apparatus has been carried into the place of use, the apparatus has been assembled, and the apparatus has been evacuated, the ion trap mass spectrometry section is not sufficiently exhausted. The adjustment of the ion source and the ion lens, which are parameters independent of the pressure inside the unit, is started. At this time, what is important is that the end cap electrodes 11a and 11a used in the ion trap mass spectrometer are used.
Applying not the high frequency voltage but the ground potential or the DC voltage to b and the ring electrode 12. This means that, at this stage, the end cap electrodes 11a and 11b and the ring electrode 12 are not used as mass spectrometers but as mere electrodes. At this time, ions generated by the ion source pass through the end cap electrodes 11a and 11b and the ring electrode 12, and the total amount of current not mass-separated is detected by the ion detector.
First, the ion source and the ion lens are adjusted so that the amount of current becomes maximum. The voltage of the end cap electrode and the ring electrode at this adjustment stage is not a problem with the ground potential, but if the amount of transmitted ions in this portion is small, the ring electrode 12 and the end cap electrode 11b on the detector side are connected. Alternatively, a voltage may be applied. For example, when observing positive ions, a voltage of minus several hundred volts may be applied. Negative ions have the opposite polarity.

If the pressure inside the ion trap mass spectrometer becomes sufficiently high during such adjustment,
It is possible to shift to the adjustment of the ion accelerating voltage and the ion trap mass analyzer, which are the remaining apparatus parameters.
In FIG. 3, these parameters are performed on the second day. However, compared to the conventional procedure, the procedure according to the present invention enables the first day to be used effectively and reduces the work on the second day. This has the advantage that the start-up of the device is faster.

In the adjustment of the acceleration voltage of the ions, the incident energy of the ions to the ion trap mass spectrometer is determined. In this case, the ion trap mass spectrometer is operated to maximize the mass-separated ions. Will be adjusted. The voltage set by the ion source and the ion lens determined before the adjustment may be translated in parallel by almost the acceleration voltage. In addition, the parameters of the ion trap mass spectrometer (e.g., high-frequency voltage, ion accumulation time, adjustment of the pressure of gas such as helium introduced into the ion trap mass spectrometer) are also examined. As described above, at this stage, the adjustment of the ion source and the ion lens is almost completed, so that the adjustment is easier than in the related art.

In the above example, one ion source is provided. However, a plurality of atmospheric pressure ion sources 30a and 30b are installed at the same time for the first pore, and the This is particularly effective in the case where the ion source can be rotated around the center 29, and when it is necessary to adjust a plurality of ion sources at the same time.

In the above example, the ions that have flowed through the skimmer from the differential evacuation unit are deflected and then introduced into the ion trap mass analysis unit. However, it goes without saying that the same effect can be obtained even when the deflection is not performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus according to the present invention.

FIG. 2 is a diagram showing the configuration of an apparatus according to the present invention.

FIG. 3 is an adjustment procedure.

FIG. 4 shows an ion source.

FIG. 5 is a configuration diagram of a conventional device.

[Explanation of symbols]

1 ---- electrospray ion source, 2 ---- capillary, 3 ---- first pore, 4 ---- second pore, 5 ----
-Skimmer, 6a, 6b-heater, 7-electrostatic lens, 8--slit, 9--deflector, 10---
Gate electrode, 11a, 11b --- end cap electrode, 12 --- ring electrode, 13 --- extraction lens, 14 --- conversion dynode, 15 ---
Scintillation counter, 16 --- amplifier, 17-
--- High voltage power supply, 18 --- Data processing device, 19 ---
Ion trap mass spectrometer control power supply, 20 --- PC /
MS interface, 21 --- roughing pump, 22
--- Turbo molecular pump, 23 --- Ion source control power supply, 24--Ion acceleration voltage control power supply, 25--Regulator, 26--cylinder, 27--Ion lens control power supply, 28 a, 28 b --- Quartz ring, 29-
--- rotating shaft, 30a, 30b--atmospheric pressure ion source, 3
1 ---- Ion taking-in pore, 32 ---- Ion taking-out pore.

Claims (1)

[Claims] 1. An ion source for generating ions at atmospheric pressure;
A differential evacuation unit for introducing ions generated from the ion source into a high vacuum region, a converging lens unit for extracting and converging ions introduced through the differential evacuation unit into the high vacuum region, An ion trap mass spectrometer comprising a mass spectrometer for mass-analyzing the ions converged by the lens unit with an ion trap mass spectrometer comprising a pair of end cap electrodes and a ring electrode and an insulating ring for insulating both ends, A method in which a ground voltage or a DC voltage is applied to a cap electrode and a ring electrode to measure and adjust a total ion current amount of ions generated by the ion source.