JP7199878B2 - Mass spectrometer and method - Google Patents

Description

The present invention relates to mass spectrometers and methods, and more particularly to controlling the operation of a quadrupole mass spectrometer.

A mass spectrometer has an ion source, a mass spectrometer, and a detector. Various mass spectrometers have been proposed. Among them, the quadrupole mass spectrometer has a mass filter (main filter) composed of four electrodes. A mass filter allows only ions having a selected mass (hereinafter "selected mass") to pass. In scan mode, selected masses are scanned, thereby obtaining a mass spectrum.

A quadrupole mass spectrometer generally has a pre-filter in front of the mass filter. The pre-filter is originally provided to efficiently guide the ions from the ion source to the main filter, in other words, to optimize the ion transmittance for each mass. The pre-filter, for example, consists of four electrodes, similar to the mass filter. By varying the bias voltage applied to the prefilter, the ion transmittance of the prefilter is changed, that is, the amount of ions entering the main filter is changed. For example, the bias voltage is dynamically changed according to the selected mass so that the sensitivity of the main filter is flattened regardless of the selected mass, ie the mass dependence in the main filter is relaxed.

Patent Documents 1 and 2 disclose a quadrupole mass spectrometer equipped with a prefilter. However, these patent documents do not disclose a mechanism for suppressing specific ions from passing through the main filter. Patent document 3 discloses a mass spectrometer having a function of removing interfering ions. The device utilizes a collision cell to remove interfering ions.

JP-A-8-293282 JP-A-7-245080 Japanese Patent Publication No. 2017-535040

When the sample introduced into the ion source contains a high-concentration substance that is not the object of analysis, it is desirable to prevent ions generated from the high-concentration substance from being detected as much as possible. For example, in thin film production by a chemical vapor deposition method such as CVD (chemical vapor deposition), a raw material gas, a reaction gas, a transport gas, and the like are introduced into a container containing an object to be vapor-deposited. In order to identify and analyze reaction products, impurities, etc. contained in the gas in the container, the gas in the container is taken out as a sample gas, and the sample gas is introduced into the ion source. In that case, the source gas, the reaction gas, the transport gas, etc., which are known high-concentration gases other than the analysis target, are also ionized in the ion source. A large amount of ions generated by the ionization can be called "interfering ions" from the perspective of the ions that are the original target of analysis. The interfering ions pass through the mass spectrometer when the mass selected by the mass spectrometer matches the mass of the interfering ions, and are detected by the detector. As a result, undulations and bulges occur in the baseline of the mass spectrum, and wear and deterioration of the detector also occur. If the amount of all ions is limited so as not to cause these problems, the ions to be analyzed cannot be detected with high sensitivity.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate or reduce the problems caused by interfering ions. Alternatively, an object of the present invention is to simply suppress passage of interfering ions through the main filter.

A mass spectrometer according to an embodiment includes a mass filter for passing ions having a selected mass from among a group of incoming ions, and a mass filter provided upstream of the mass filter. and a suppression unit for suppressing the group of ions entering the mass filter.

According to the above configuration, when the selected mass in the mass filter matches the mass of the interfering ions, the group of ions entering the mass filter is temporarily suppressed, so the amount of interfering ions passing through the mass filter is small. Become. As a result, undulations and bulges occurring in the baseline of the mass spectrum can be eliminated or reduced, and the detection section can be protected to prevent its sensitivity from deteriorating. Note that the mass handled by the mass spectrometer is actually the mass-to-charge ratio (m/z) defined by dividing the mass number m by the charge z.

In an embodiment, the mass filter is a main filter of a quadrupole mass spectrometer, and the suppressor is a prefilter of the quadrupole mass spectrometer. According to this configuration, it is possible to easily suppress passage of interfering ions by using the pre-filter. A configuration other than the pre-filter may be used as means for temporarily suppressing the entry of ion groups.

A mass spectrometer according to an embodiment includes a storage unit that stores a profile defining operating conditions of the prefilter for each selected mass, and a control unit that sets the operating conditions of the prefilter according to the profile, The profile includes a suppression pulse to suppress the interfering ions. The suppression pulse temporarily and sharply suppresses the amount of ions in a group of ions input to the mass filter, and corresponds to a suppression line, a suppression peak, and the like.

A mass spectrometer according to an embodiment includes means for generating a base profile for adjusting the characteristics of the main filter, and means for generating the profile by superimposing the suppression pulse on the base profile. The base profile varies the operating conditions with changes in selected masses to, for example, optimize the ion transmission of the mass filter for each mass or relax the mass filter's mass dependence. A suppression pulse is superimposed on such a base profile. The above configuration suppresses passage of interfering ions by extensively or progressively utilizing the function for adjusting or calibrating the mass filter.

A mass spectrometer according to an embodiment defines means for specifying the mass of the interfering ions and the degree of suppression of the interfering ions, and defines the suppression pulse based on the mass of the interfering ions and the degree of suppression of the interfering ions. and means.

In an embodiment, the operating condition of the prefilter is the bias voltage of the prefilter, and the bias voltage of the prefilter is changed according to the profile during the scanning of the selected masses. In embodiments, the profile includes multiple suppression pulses corresponding to multiple interfering ions.

A method according to an embodiment comprises the steps of: introducing a sample containing a low-concentration substance and a high-concentration substance into an ion source to generate an ion population containing interfering ions originating from the high-concentration substance; adjusting the amount of ions entering the mass filter by changing the transmission of ions from the ion source between and C. abruptly dropping the transmittance at a point in time.

According to the present invention, problems caused by interfering ions can be eliminated or reduced. Alternatively, according to the present invention, passage of interfering ions in the main filter can be easily suppressed.

1 is a block diagram showing a mass spectrometer according to an embodiment; FIG. It is a schematic diagram which shows a pre-filter. 4 is a flowchart showing an operation example of the mass spectrometer according to the embodiment; FIG. 4 is a diagram for explaining creation of a base profile; FIG. FIG. 4 is a diagram for explaining creation of a profile having suppression pulses; FIG. It is a figure which shows the mass spectrum which concerns on a comparative example. It is a figure which shows the mass spectrum which concerns on embodiment. It is a figure which shows the structural example of a control part. FIG. 4 is a diagram for explaining synthesis of a base profile and a pulse train; It is a figure which shows the modification of a mass spectrometer.

Hereinafter, embodiments will be described based on the drawings.

FIG. 1 shows a mass spectrometer according to an embodiment. A mass spectrometer is a device that analyzes and measures the mass of each substance in a sample. A mass spectrometer according to an embodiment has a function of generating a mass spectrum.

The ion source 10 ionizes a sample to generate ions. Electron ionization, chemical ionization, electrospray ionization, and the like are known as ionization methods. The sample is gas, liquid or solid. In an embodiment, the sample is an externally introduced sample gas, indicated at 12 .

For example, in thin film production by a chemical vapor deposition method such as CVD, a raw material gas, a reaction gas, a transport gas, and the like are introduced into a container containing an object to be vapor-deposited. In order to identify and analyze reaction products and impurities contained in the gas inside the container, the gas inside the container is taken out as a sample gas. The sample gas is introduced directly into ion source 10 . In this case, the ion source also ionizes the source gas, the reaction gas, the transport gas, etc., which are known high-concentration gases other than the analysis target. A large amount of ions produced by the ionization are called interfering ions as described above. For example, such ions are argon ions. Thus, the group of ions generated by the ion source 10 includes a plurality of ions generated from the low-concentration gas to be analyzed, as well as interfering ions generated from the high-concentration gas not to be analyzed. A gas chromatograph, a liquid chromatograph, or the like may be connected upstream of the ion source 10 .

In FIG. 1, an ion converging lens 18, a quadrupole mass spectrometer 20, and a detector 26 are provided on the ion trajectory 16 as the optical axis. A collision cell, another quadrupole mass spectrometer, or the like may be further arranged on the ion trajectory 16 . The ion converging lens 18 converges a group of ions entering the quadrupole mass spectrometer 20 .

The illustrated quadrupole mass spectrometer 20 has a main filter 22 and a prefilter 24 . The main filter 22 has four electrodes (poles) and functions as a mass filter. That is, it has a function of passing only ions having a selected mass (selected mass). As is well known, the four electrodes are roughly divided into two electrode pairs, one electrode pair is supplied with a drive signal of one polarity (e.g., positive) and the other electrode pair is supplied with the other polarity (e.g., negative). of drive signals are supplied. Each drive signal has an AC component and a DC component. Additionally, each drive signal has a bias voltage that defines an axis voltage on the central axis. A bias voltage is common between the four electrodes. For example, in the scan mode, the selected mass is scanned by continuously changing the amplitude value of each drive signal and the voltage of the DC component. In SIM (Selective Ion Monitoring) mode, a plurality of prespecified masses are cyclically selected.

The pre-filter 24 is a sub-filter or an entrance electrode section provided before the main filter 22 . The pre-filter 24 is provided for optimizing the transmittance for each mass in the main filter 22 . In other words, the pre-filter 24 has the function of adjusting the amount of ions entering. The pre-filter 24, like the main filter 22, consists of four electrodes (poles), that is, two electrode pairs. A driving signal for one electrode is supplied to one electrode pair, and a driving signal for the other electrode is supplied to the other electrode pair. Each drive signal has an AC component as described above and a bias voltage that defines an axial voltage on the central axis. A bias voltage is common between the four electrodes. The bias voltage of the main filter 22 and the bias voltage of the pre-filter 24 are set independently. Note that the pre-filter 24 is configured to be easier to attach and detach than the main filter 22 in order to clean it.

Since the potential difference from the bias voltage of the main filter 22 changes due to the variation of the bias voltage of the pre-filter 24, the potential barrier when the ion group passes through fluctuates up and down. That is, the transmittance of the ion group passing through the pre-filter 24 varies. This makes it possible to control the amount of ions entering the main filter 22 . The pre-filter 24 essentially manipulates the characteristics of the main filter 22 by manipulating the amount of ions entering the main filter 22 according to the selected mass. For example, the sensitivity is made constant by reducing the mass dependency in the main filter 22 . In an embodiment, the pre-filter 24 also temporarily plumbs the ion abundance of the group of ions entering the main filter 22 when the selected mass matches the mass of the interfering ions, causing the interfering ions to pass through the main filter 22 . It has the function of minimizing or reducing the amount of ions. Although the pre-filter 24 itself does not have a mass selection function, by synchronizing with the mass selection of the main filter in the subsequent stage and narrowing down the entire group of ions incident on the main filter, as a result, the detection unit 26 It prevents a large amount of interfering ions from reaching. Thus, in the embodiment, the pre-filter 24 functions as interfering ion suppressing means or an interfering ion suppressing section. Other configurations may be employed for interfering ion suppression. For example, the amount of ions in a group of ions may be reduced by varying the bias voltage of the ion converging lens 18 .

The detector 26, in embodiments, includes a conversion dynode and an electron multiplier. The conversion dynode converts incoming ions into electrons, which are detected by an electron multiplier. The detection signal is sent to the calculation section 30 . An A/D converter or the like for processing the detection signal is provided between the detection section 26 and the calculation section 30, but they are omitted from the drawing. A configuration other than the configuration described above may be adopted as the detection unit 26 .

The control unit 32 is configured by, for example, a personal computer, and controls the operation of each configuration shown. The calculation unit 30 is configured by, for example, a personal computer. The control unit 32 and the calculation unit 30 may be configured by a single personal computer. The calculation unit 30 has a function of analyzing the detection signal, and more specifically has a function of generating a mass spectrum based on the detection signal. An input device 38 and a display device 40 are connected to the control unit 32, and the storage unit 34 is also connected. The input device 38 is configured by a keyboard, pointing device, etc., and the display device 40 is configured by a display device such as an LCD. In the embodiment, the display screen of the display 40 stores a plurality of profiles 36 defining the operating conditions of the pre-filter 24 . Each profile 36 is a parameter table that defines operating conditions or bias voltages for each selected mass.

The power supply circuit 28 is a circuit that supplies drive signals or power necessary to drive each component. A pair of drive signals are supplied from the power supply circuit 28 to the main filter 22 , and a bias voltage is supplied from the power supply circuit 28 to the prefilter 24 . Drive signals, voltages, etc. required for the operation are also supplied to other configurations. The operation of the power supply circuit 28 is controlled by the controller 32 .

In embodiments, the controller 32 controls the ion transmission rate of the prefilter 24 according to the selected profile. For example, when the scan mode is selected as the operation mode of the quadrupole mass spectrometer 20 , the controller 32 continuously changes the selected mass of the main filter 22 . Along with this, the control unit 32 dynamically changes the bias voltage of the prefilter 24 . As a result, the amount of ions entering the main filter 22 is adjusted. As a result, the mass dependent characteristic of the main filter 22 is improved or flattened. Also, a large amount of interfering ions are prevented from passing through the main filter 22 and reaching the detector 26 . However, if there are no interfering ions in the ion group, the function of suppressing passage of specific ions does not work.

FIG. 2 shows a configuration example of the pre-filter 24. As shown in FIG. FIG. 2 shows a plane perpendicular to the ion trajectory 16 . As already explained, the pre-filter 24 consists of four electrodes 24a-24d, which form two electrode pairs. A signal line 42 for supplying a driving signal is connected to one electrode pair, and a signal line 44 for supplying a driving signal is connected to the other electrode pair. For example, two high-frequency signals and bias voltages with different polarities are supplied to two electrode pairs via two signal lines 42 and 44 . When the four electrodes forming the main filter and the four electrodes forming the pre-filter 24 are AC-coupled, the AC component in the pair of drive signals supplied to the main filter is also supplied to the pre-filter 24. In that case, a common signal line should be connected to the four electrodes 24a to 24d. A bias voltage is applied to each electrode 24a-24d via a common signal line.

FIG. 3 shows an operation example of the mass spectrometer shown in FIG. 1 as a flow chart. In S10, the user selects whether or not to execute the adjustment mode. When executing the adjustment mode, a profile is created in S12, or an already generated profile is modified. The profile, as described above, corresponds to a table, curve or function for defining the operating conditions of the prefilter, and defines the bias voltage for each selected mass in the main filter.

In S12, when creating a profile, provisional measurement using a calibration sample or an actual sample is performed as necessary, and the bias voltage is specified or changed while referring to or confirming the mass spectrum as the provisional measurement result. creates a base profile. A base profile may be defined by one or more straight lines. A base profile may be created without taking preliminary measurements.

In S12, if necessary, a suppression pulse is defined based on the user-specified mass and degree of suppression, and the suppression pulse is superimposed and added to the base profile. This creates a multi-function profile. A suppression pulse may be added by partial modification of the waveform of the base profile. Temporary measurements may be performed when defining or adding suppression pulses. In S12, the already created profile may simply be corrected in the measurement where interfering ions are not a problem. As exemplified later, multiple suppression pulses corresponding to multiple interfering ions may be added to the base profile.

In S14, the created or modified profile is registered in the storage unit. A plurality of profiles may be registered in the storage unit, and the profile to be actually used may be manually or automatically selected from among the plurality of profiles according to the sample, interfering substance, or the like.

At S16, the profile created as described above is selected or designated and applied. A profile to be used may be preset. At S20, mass spectrometry is performed on the sample. At that time, the scan mode is executed. That is, the main filter is scanned with selected masses to acquire a mass spectrum. The prefilter bias voltage is then set for each selected mass according to a selected or specified profile. In situations where only the base profile is applied, the bias voltage is slowly changed or kept constant. When the selected mass matches the mass of the interfering ions, a bias voltage defined by the suppression pulse is set. This blocks or reduces all of the ions entering the main filter. The bias voltage temporarily steeply changes at the time of transition from immediately before the suppression pulse to the suppression pulse and at the time of transition from the suppression pulse to immediately after the suppression pulse.

It should be noted that the scan of the selected mass is repeatedly executed as necessary. In SIM mode, the profile is also applied, but in that case the interfering ions are usually not monitored, so the suppression pulse has virtually no effect. However, it can be said that the advantage of the above configuration is that a common profile can be used regardless of the operation mode.

Next, an example of creating a profile will be described with reference to FIGS. 4 and 5. FIG. 4 and 5 show a display screen 50 as a user interface for profile creation. Display screen 50 includes a first window 52 and a second window 54 .

In FIG. 4, profile 56 is displayed in first window 52 . The horizontal axis is the mass axis (more precisely, the m/z axis), and the vertical axis represents the bias voltage. The bias voltage is usually expressed as a relative value, but it may be expressed as an absolute value. Profile 56 is smoothly varying along the horizontal axis and it contains no suppression pulses. Profile 56 corresponds to the base profile. A base profile can be created or modified by a user by specifying numerical values or otherwise.

A second window 54 displays a mass spectrum 58 obtained by applying the profile 56 . The horizontal axis is the mass axis (more precisely, the m/z axis), and the vertical axis represents the ion intensity. The center mass of the display range is specified by entering a numerical value in box 61 or the like. In the illustrated example, mass 40 is specified. Mass spectrum 58 is an extended spectrum corresponding to a portion of the mass spectrum. In the illustrated example, the interfering ions are argon ions and have a mass of 40. A large amount of argon ions are included in the group of ions entering the main filter. of argon ions pass therethrough to the detector where they will be detected. In the illustrated example, the argon ion peak is saturated (see reference numeral 58a).

On the other hand, in FIG. 5, the first window 52 displays a profile 60 with a suppression pulse 60b. Specifically, the profile 60 consists of a base profile 60a and a suppression pulse 60b. When defining the suppression pulse 60b, the user specifies the mass and degree of suppression (bias voltage) for each interfering ion. In the illustrated example, the suppression pulse 60b constitutes a positively elongated peak, assuming that the group of ions is a group of positive ions. It is superimposed at the position corresponding to mass 40 and the peak level is maximum. When limiting negative ions, the suppression pulse is configured as a negatively stretched peak.

Window 54 shows the spectrum 62 resulting from application of profile 60 . A strong peak occurs at mass 40 in spectrum 58 shown in FIG. 4, but a peak 62a occurs at mass 40 in spectrum 62 shown in FIG. very small. That is, as a result of the application of the suppression pulse 60b, when the selected mass coincides with the mass 40 of argon, the amount of ions in the group of ions incident on the main filter is significantly suppressed or minimized, and as a result, the output from the main filter The amount of argon ions absorbed is minimized. As a result, it is possible to effectively prevent the detection unit from being consumed and degraded due to a large amount of interfering ions.

In the adjustment mode, while referring to the mass spectrum displayed in the window 54, the magnitude of the suppression pulse 60b displayed in the window 52 (the degree of suppression of interfering ions) and the like are specified or modified. Note that the base profile may be automatically created. Also, the suppression pulse may be automatically defined according to the sample or interfering ion designation.

FIG. 6 shows a mass spectrum 64 according to a comparative example. FIG. 7 shows a mass spectrum 66 according to the embodiment. A mass spectrum 64 is a mass spectrum acquired without application of a suppression pulse, and a mass spectrum 66 is a mass spectrum acquired with application of a suppression pulse.

In the mass spectrum 64 shown in FIG. 6, the peak A of argon ions, which are interfering ions, is very large, and the peak B of the bivalent argon (argon ions of mass 20) is also prominent. In that case, an argon dimer (argon ion of mass 80) peak may also occur (see C). A plurality of peaks indicated by D and E are peaks to be analyzed (detected).

In the mass spectrum 66 shown in FIG. 7, the peak A of argon ions, which are interfering ions, is very small. The argon dimer peak B is maintained. If suppression control is applied to this, it is possible to easily reduce peak B to an arbitrary level. Several peaks indicated by D and E are maintained.

FIG. 8 shows a specific configuration example of the control unit. In FIG. 8, the same reference numerals are assigned to the components shown in FIG. 1, and the description thereof will be omitted. In FIG. 8, the control section 32A creates a profile, and particularly includes a profile synthesizing section 68. FIG.

The operation of the profile synthesizer 68 is shown in FIG. In FIG. 9, a suppression pulse train 72 is synthesized with an already created base profile 70 to generate a profile 74 . The suppression pulse train 72 is composed of three suppression pulses 72a, 72b and 72c in the illustrated example. The individual suppression pulses 72a, 72b, 72c have different peak levels. For example, if the mass of the interfering ions suppressed by the suppression pulse 72a is M, the suppression pulse 72b suppresses interfering ions having a mass of M/2, and the suppression pulse 72c suppresses interfering ions having a mass of 2M. is suppressed. Based on such relationships, the specification of M may automatically generate three suppression pulses 72a, 72b, 72c. The width of each suppression pulse 72a, 72b, 72c corresponds to the smallest unit in mass selection. You may make it expand the width as needed. The heights of the individual suppression pulses 72a, 72b, and 72c are desirably set individually, but they may be of uniform height.

A variant is shown in FIG. In addition, in FIG. 10, the same reference numerals are given to the same configurations as those shown in FIG. 1, and the description thereof will be omitted.

In the mass spectrometer shown in FIG. 10, a first quadrupole mass spectrometer 20, a quadrupole collision cell 80, and a second quadrupole mass spectrometer are provided between the ion converging lens 18 and the detector 26. A pole type mass spectrometer 86 is provided. The first quadrupole mass spectrometry section 20 has a main filter 22 , a pre-filter 24 as an entrance electrode section, and an exit electrode section 25 . The pre-filter 24 functions as the interfering ion suppressing means already explained.

The quadrupole collision cell 80 has a main unit 83 , an entrance electrode section 82 and an exit electrode section 84 . The main unit 83 operates in all ion passage mode and has a collision gas introduced therein. Product ions are generated from the precursor ions in the main unit 83 . The second quadrupole mass spectrometry unit 86 has the same configuration as the first quadrupole mass spectrometry unit 20, that is, a main filter 89, an entrance electrode unit 88, and an exit electrode unit 90. have. Mass selection is performed on the product ions in the second quadrupole mass spectrometer 86 .

A plurality of profiles 36A are stored in the storage section 34A, and the control section 32A controls the operation of the prefilter 24 according to a profile selected from among them. That is, when the mass selected in the main filter 22 matches the mass of the interfering ions, the pre-filter 24 restricts passage of the group of ions, and the amount of interfering ions discharged from the main filter 22 is reduced. As a result, the amount of product ions generated from interfering ions in the quadrupole collision cell 80 is also reduced.

The pre-filter 24 in the first quadrupole mass spectrometry unit 20 functions as interfering ion suppressing means, and the entrance electrode unit 88 in the second quadrupole mass spectrometry unit 86 functions as interfering ion suppressing means. good too. In that case, specific product ions are suppressed as interfering ions. With two stages of suppression, the effects of interfering ions can be largely eliminated. It is also conceivable to make the individual exit electrode portions 25, 84, 90 function as interfering ion suppressing means.

According to the above embodiment, when the selected mass in the mass filter matches the mass of the interfering ions, the group of ions entering the mass filter is suppressed, so the amount of interfering ions exiting the mass filter can be reduced, or , can be practically zero. This makes it possible to prevent or reduce the deterioration of the detector due to interfering ions. Moreover, since the above effects can be obtained simply by expanding or developing a profile that defines the operating conditions of a prefilter that is generally provided, the above embodiment can be realized at a low cost and is of practical value. is high.

10 ion source, 20 quadrupole mass spectrometer, 22 main filter (mass filter), 24 pre-filter, 26 detector, 28 power supply circuit, 32 controller, 36 profile.

Claims (4)

a mass filter that passes ions having a selected mass from among the group of ions that have entered;
a suppression unit provided in front of the mass filter and suppressing a group of ions entering the mass filter when the selected mass matches the mass of interfering ions;
a control unit that sets the bias voltage of the suppression unit according to a profile that defines the bias voltage for each selected mass;
Designating means for a user to designate the mass of the interfering ions and the degree of suppression of the interfering ions;
profile creation means for creating the profile by adding a suppression pulse for suppressing interfering ions defined based on the mass of the interfering ions and the degree of suppression of the interfering ions to the base profile;
display means for displaying a first window containing the profile and a second window containing the mass spectrum obtained by applying the profile when the profile is created;
including
When the selected mass matches the mass of the interfering ions, the action of the suppression pulse temporarily increases the potential barrier in the suppression section, thereby suppressing the group of ions entering the mass filter. ,
modifying the suppression pulse displayed in the first window with reference to the mass spectrum displayed in the second window;
A mass spectrometer characterized by: The apparatus of claim 1, wherein
The mass filter is a main filter of a quadrupole mass spectrometer,
The suppression unit is a prefilter of the quadrupole mass spectrometer,
A mass spectrometer characterized by: The apparatus of claim 1 , wherein
wherein the profile includes multiple suppression pulses corresponding to multiple interfering ions;
A mass spectrometer characterized by: introducing a sample containing a low-concentration substance and a high-concentration substance into an ion source to produce an ion population comprising interfering ions originating from the high-concentration substance;
The amount of ions entering the mass filter is adjusted by changing the transmittance of the ions from the ion source by changing the bias voltage of a prefilter provided between the ion source and the mass filter. a step of abruptly dropping the transmittance when the selected mass matches the mass of the interfering ions in scan mode;
including
setting the bias voltage of the prefilter according to a profile defining the bias voltage for each selected mass;
the profile includes a suppression pulse for suppressing entry of the interfering ions into the mass filter;
when the selected mass matches the mass of the interfering ions, the action of the suppression pulse temporarily raises a potential barrier in the prefilter, thereby suppressing ions entering the mass filter ;
the mass of the interfering ions and the degree of suppression of the interfering ions are specified by the user;
creating the profile by adding to the base profile the suppression pulse defined based on the mass of the interfering ions and the degree of suppression of the interfering ions;
When creating a profile, a first window containing the profile and a second window containing the mass spectrum obtained by applying the profile are displayed,
modifying the suppression pulse displayed in the first window with reference to the mass spectrum displayed in the second window;
A mass spectrometry method characterized by:

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