JP6870406B2 - Tandem quadrupole mass spectrometer and control parameter optimization method for the device - Google Patents

Description

The present invention relates to a technique for determining control parameters when performing multiple reaction monitoring (MRM) measurement in a tandem quadrupole mass spectrometer (also called a triple quadrupole mass spectrometer).

One of the methods of mass spectrometry is called "MS / MS analysis (tandem analysis)", and in performing this MS / MS analysis, for example, a tandem quadrupole mass spectrometer is used.
In MS / MS measurement in a general tandem quadrupole mass spectrometer, ions derived from a compound generated by an ion source are first described as a quadrupole mass filter (conventionally referred to as "Q1") in the previous stage. ), Where ions having a specific mass-to-charge ratio m / z are selected as precursor ions. This precursor ion is introduced into a collision cell equipped with a quadrupole (or higher multi-pole) ion guide (conventionally described as "q2"). A collision-induced dissociation (CID) gas such as argon is supplied into the collision cell, and the precursor ions introduced into the collision cell collide with the CID gas and cleave, thereby generating various product ions. To. This product ion is introduced into a subsequent quadrupole mass filter (conventionally described as "Q3"), where product ions with a specific mass-to-charge ratio are sorted and reach the detector. Detected.

In a tandem quadrupole mass spectrometer, for example, the mass-to-charge ratio of ions that can pass through the quadrupole mass filter in the front stage and the quadrupole mass filter in the rear stage is fixed, and a specific product for a specific precursor ion is used. So-called "multiple reaction monitoring measurement (MRM measurement)" for measuring the intensity (amount) of ions can be performed. In the MRM measurement, a compound to be measured, ions derived from contaminants, neutral particles, and the like can be removed by a two-step mass filter, so that an ionic strength signal having a high SN ratio can be obtained. Therefore, MRM measurement is particularly effective for quantification of trace components.

Further, the tandem quadrupole mass spectrometer may be used alone, but is often used in combination with a liquid chromatograph (LC) or a gas chromatograph (GC). For example, LC / MS / MS using a tandem quadrupole mass spectrometer as a liquid chromatograph detector is often used for quantitative analysis of compounds in a sample containing a large number of compounds or a sample containing impurities (for example, See Patent Document 1).

When performing MRM measurement in LC / MS / MS (or GC / MS / MS), the mass-to-charge ratio of the target precursor ion and the product are associated with the retention time of each target compound (target compound). The combination of mass-to-charge ratios of ions (so-called "MRM transitions") is specified (or automatically determined) by the analyst. At this time, for the specified MRM transition, various control parameters in MRM measurement (specifically, the prerod voltage of the quadrupole mass filter in the front stage (so-called "Q1 Prerod Bias"), the rear stage Adjust the prerod voltage of the quadrupole mass filter (so-called "Q3 Prerod Bias") and the collision energy in the collision cell (so-called "Collision Energy", etc.) to the optimum values. Thereby, the signal intensity of the ion derived from each target compound can be obtained with high accuracy and sensitivity, and the quantification of the compound can be performed with high accuracy and high sensitivity.

Therefore, there is a mass spectrometer having a function of automatically optimizing each of these control parameters so as to be optimal for the MRM transition.

In a conventional mass spectrometer, this optimization is performed as follows, for example.
First, for the target compound, when an MRM transition is specified, for example, by an analyst, an MRM measurement is performed on a known sample (standard sample) containing the target compound (first MRM measurement). In this MRM measurement, each of the Q3 pre-rod voltage and the collision energy is fixed to a predetermined default value set in advance by an analyst or the like, and only the Q1 pre-rod voltage is changed one after another. When this MRM measurement is completed and the measurement result is obtained, the value of the Q1 prerod voltage that gave the strongest detection signal is specified, and this is determined as the optimum value.

Subsequently, another standard sample is prepared and the MRM measurement is performed again (second MRM measurement). In this MRM measurement, the Q1 prerod voltage is fixed to the optimum value determined earlier, and the collision energy is fixed to the same default value as in the first MRM measurement. Then, only the Q3 pre-rod voltage is changed one after another. When this MRM measurement is completed and the measurement result is obtained, the value of the Q3 prerod voltage that gave the strongest detection signal (that is, the value of the Q3 prerod voltage that gave the strongest detection signal under the optimum Q1 prerod voltage). ) Is specified, and this is determined as the optimum value.

Subsequently, another standard sample is prepared and the MRM measurement is performed again (third MRM measurement). In this MRM measurement, each of the Q1 pre-rod voltage and the Q3 pre-rod voltage is fixed to the optimum value determined in advance, and only the collision energy is changed one after another. When this MRM measurement was completed and the measurement result was obtained, the strongest detection signal was given under the collision energy value that gave the strongest detection signal (that is, under the optimum Q1 prerod voltage and the optimum Q3 prerod voltage). Collision energy value) is specified and this is determined to be the optimum value.

JP-A-2015-76338

In the conventional method, only one type of control parameter for one compound can be optimized in one MRM measurement. Therefore, in order to optimize each of the three control parameters of Q1 prerod voltage, Q3 prerod voltage, and collision energy for one compound, three standard samples and three MRM measurements are required. For example, 30 standard samples and 30 MRM measurements are required to optimize each control parameter for 10 compounds. As described above, in the past, optimization of control parameters for MRM measurement required a great deal of time and cost.

An object to be solved by the present invention is to provide a technique capable of optimizing control parameters for MRM (multiple reaction monitoring) measurement in a short time and at low cost.

The present invention made to solve the above problems
This is a control parameter optimization method that determines the optimum control parameters for a compound in a tandem quadrupole mass spectrometer that has a quadrupole mass filter equipped with prerod electrodes in front of and behind the collision cell that cleaves ions. hand,
a) A measurement step for performing MRM measurement on a sample containing the compound, and
b) A determination step of determining the optimum value of the control parameter based on the measurement result obtained by the measurement step, and a determination step.
With
The measurement process
a1) While fixing the collision energy value to a predetermined value, changing the combination of the pre-rod voltage value of the quadrupole mass filter in the front stage and the pre-rod voltage value of the quadrupole mass filter in the rear stage, the MRM The first measurement step to perform the measurement,
With
The determination process
b1) In the first measurement step, the combination that gives the strongest detection signal is the combination of the optimum value of the prerod voltage of the quadrupole mass filter in the first stage and the optimum value of the prerod voltage of the quadrupole mass filter in the second stage. The first decision process to decide,
To be equipped.

According to the present invention, the optimum value of the prerod voltage of the quadrupole mass filter in the front stage and the optimum value of the prerod voltage of the quadrupole mass filter in the rear stage are simultaneously determined by one MRM measurement. Therefore, the control parameters can be optimized in a short time and at low cost.
In the present invention, in the first measurement step, the collision energy value is arbitrarily selected from an appropriate range (that is, at least a range of collision energy capable of cleaving precursor ions to generate product ions). Can be done. Therefore, here, the collision energy is not always fixed at the optimum value in the first measurement step. However, according to various experiments and discussions, the inventors of the present case have shown that the pre-rod voltage of each of the quadrupole mass filters in the first and second stages affects the ion introduction mode, and the collision energy affects how the precursor ions are destroyed. However, it has been found that the former and the latter are independent control parameters without correlation, and from this finding, even if the collision energy is not fixed to the optimum value in the first measurement step, It was speculated that each optimum value of each prerod voltage could be specified with sufficient accuracy. Then, the inventors have experimentally confirmed that the optimum value of each pre-rod voltage can be specified with sufficient accuracy according to the aspect of the present invention.
Further, the MRM measurement is performed while fixing one of the Q1 pre-rod voltage and the Q3 pre-rod voltage to a constant value and changing only the other voltage by the conventional method described above (that is, the measurement result). In the method of determining the optimum value of the other voltage based on the above), there are many combinations of voltage values that are not applicable in MRM measurement, but according to the present invention, all possible combinations are covered. Therefore, the optimum value of each pre-rod voltage can be accurately determined.

In the method for optimizing the control parameters, the optimum value of the collision energy may be determined, for example, by performing a separate measurement or the like (or theoretically by calculation), but it is preferable.
The measurement process
a2) The MRM measurement while changing the value of the collision energy while fixing each value of the pre-rod voltage of the quadrupole mass filter in the first stage and the pre-rod voltage of the quadrupole mass filter in the second stage to a constant value. Second measurement step,
With
The determination process
b2) In the second measurement step, the second determination step of determining the value of the collision energy to which the strongest detection signal is given as the optimum value.
To be equipped.

According to the present invention, one MRM measurement determines not only the optimum value of the prerod voltage of the quadrupole mass filter in the first stage and the prerod voltage of the quadrupole mass filter in the second stage, but also the optimum value of collision energy. Will be done. Therefore, the control parameters can be optimized in a particularly short time and at low cost.
In the present invention, in the second measurement step, the pre-rod voltages of the quadrupole mass filters in the front stage and the rear stage are not always fixed to the optimum values. However, as described above, the inventors of the present case have obtained the finding that each pre-rod voltage and the collision energy are independent control parameters having no correlation, and from this finding, in the second measurement step. It was speculated that the optimum value of collision energy could be specified with sufficient accuracy even if each prerod voltage was not fixed to the optimum value. Then, the inventors have actually confirmed by experiments that the optimum value of each collision energy can be specified with sufficient accuracy according to the aspect of the present invention.

Preferably, in the control parameter optimization method,
In the measurement step, MRM measurement is performed on a sample containing a plurality of types of compounds.
In the determination step, the optimum value of the control parameter is determined for each of the plurality of types of compounds.

According to the present invention, the optimum value of the control parameter is determined for each of the plurality of types of compounds in one MRM measurement. Therefore, the control parameters can be optimized in a particularly short time and at low cost.

The present invention also covers a tandem quadrupole mass spectrometer. The tandem quadrupole mass spectrometer according to the present invention
A tandem quadrupole mass spectrometer having a quadrupole mass filter equipped with a pre-rod electrode in front of and behind a collision cell that cleaves ions.
a) A measuring unit that performs MRM measurement on a sample containing a compound,
b) An optimum value determination unit that determines the optimum value of the control parameter for the compound based on the measurement result obtained by the measurement step.
With
The measuring unit
While fixing the collision energy value to a constant value, the MRM measurement is performed while changing the combination of the pre-rod voltage value of the quadrupole mass filter in the front stage and the pre-rod voltage value of the quadrupole mass filter in the rear stage. Do,
The decision part
In the MRM measurement, the combination that gives the strongest detection signal is determined as the combination of the optimum value of the prerod voltage of the quadrupole mass filter in the first stage and the optimum value of the prerod voltage of the quadrupole mass filter in the second stage.

Since the optimum value of the prerod voltage of the quadrupole mass filter in the first stage and the optimum value of the prerod voltage of the quadrupole mass filter in the second stage are determined at the same time by one MRM measurement, the optimization of the control parameters can be performed in a short time. And it can be done at low cost.

The block diagram of the main part of the liquid chromatograph mass analyzer which concerns on embodiment. The figure which shows the flow of the process which concerns on the optimization of a control parameter. The figure which shows the configuration example of the reception screen for accepting various input operations related to the setting of a method file from an operator. The figure for demonstrating the mode of setting each value of Q1 pre-rod voltage, Q3 pre-rod voltage, and collision energy for each channel.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiments are examples that embody the present invention and do not limit the technical scope of the present invention.

<1. Device configuration>
The configuration of the liquid chromatograph mass spectrometer according to the embodiment will be described with reference to FIG. FIG. 1 is a block diagram of a main part of the liquid chromatograph mass spectrometer 100.

The liquid chromatograph mass spectrometer 100 includes a liquid chromatograph unit 1, a mass spectrometer 2, and a control unit 3.

<Liquid chromatograph unit 1>
The liquid chromatograph unit 1 injects a predetermined amount of a mobile phase container 10 in which the mobile phase is stored, a pump 11 that sucks the mobile phase and feeds it at a constant flow rate, and a sample prepared in advance in the mobile phase. It includes an injector 12 and a column 13 that separates various compounds contained in the sample in the time direction.

In this configuration, the mobile phase stored in the mobile phase container 10 is sucked by the pump 11 and fed to the column 13 at a constant flow rate. During this feeding, a certain amount of sample liquid is introduced into the mobile phase from the injector 12, and the sample is introduced into the column 13 along with the flow of the mobile phase. Then, while passing through the column 13, various compounds in the sample are separated in the time direction, eluted from the outlet of the column 13, and introduced into the mass spectrometer 2.

<Mass spectrometer 2>
The mass spectrometer 2 is a tandem quadrupole mass spectrometer having quadrupole mass filters 231 and 234 provided with pre-rod electrodes 2312 and 2342 in front of and behind the collision cell 232 for cleaving ions.

Specifically, the mass spectrometer 2 has a stepwise degree of vacuum between the ionization chamber 20, which has a substantially atmospheric pressure, and the high-vacuum analysis chamber 23, which is evacuated by a high-performance vacuum pump (not shown). It is provided with a configuration of a multi-stage differential exhaust system in which the first intermediate vacuum chamber 21 and the second intermediate vacuum chamber 22 are arranged.

In the ionization chamber 20, an electrospray ionization probe 201 that sprays the sample solution while applying an electric charge is installed. Further, the ionization chamber 20 and the first intermediate vacuum chamber 21 in the next stage communicate with each other through a small-diameter heating capillary 202. Further, ion guides 211 and 221 for transporting ions to the subsequent stage while converging the ions are installed in the first intermediate vacuum chamber 21 and the second intermediate vacuum chamber 22, respectively. Further, the first intermediate vacuum chamber 21 and the second intermediate vacuum chamber 22 are separated by a skimmer 212 having a small hole at the top.

In the analysis chamber 23, a front-stage quadrupole mass filter 231 that separates ions according to the mass-to-charge ratio, a collision cell 232 in which a multi-pole ion guide 233 is installed inside, and ions are separated according to the mass-to-charge ratio. The subsequent quadrupole mass filter 234 and the ion detector 235 are installed in this order.

The collision cell 232 is connected to a CID gas supply mechanism (not shown) such as argon or nitrogen so that the CID gas is continuously (or intermittently) supplied to the inside of the collision cell 232. It has become.

Each of the electrospray ionization probe 201, the ion guides 211,221,233, and the quadrupole mass filter 231,234 is connected to the power supply unit 24. The power supply unit 24 applies a predetermined voltage to each of these units 2011, 211, 221, 233, and 231, 234, respectively. However, each of the front and rear quadrupole mass filters 231 and 234 has a main rod electrode 2311 and 341 and a pre-rod electrode arranged in front of the main rod electrode (that is, a pre-rod for correcting electric field disturbance at the inlet end). Electrodes) 2312, 2342 are provided, and the power supply unit 24 can apply different voltages to the main rod electrodes 2311, 2341 and the pre-rod electrodes 2312, 2342, respectively.

A mode in which analysis is performed by the mass spectrometer 2 according to the above configuration will be described.
When the eluate from the column 13 reaches the electrospray ionization probe 201, the eluate is sprayed while being charged at the tip of the probe 201. The droplets (charged droplets) formed by spraying are subdivided while being divided by the action of electrostatic force due to the applied electric charge, and in the process, the solvent is vaporized and the ions derived from the compound are ejected. The ionization method is not limited to this electrospray ionization method, and an atmospheric chemical ionization method, an atmospheric photoionization method, or the like may be used.

The generated ions are sent to the first intermediate vacuum chamber 21 through the heating capillary 202, where they are converged by the ion guide 211, and then sent to the second intermediate vacuum chamber 22 through the small holes at the top of the skimmer 212. The compound-derived ions are then converged by the ion guide 221 and then sent to the analysis chamber 23 to be introduced into the space in the major axis direction of the pre-stage quadrupole mass filter 231.

When performing MS / MS analysis, a predetermined DC voltage is applied from the power supply unit 24 to the pre-rod electrodes 2312 and 2342 of the front-stage quadrupole mass filter 231 and the rear-stage quadrupole mass filter 234, respectively. Further, each main rod electrode 2311, 341 of the front quadrupole mass filter 231 and the rear quadrupole mass filter 234 also receives a predetermined voltage (voltage in which a high frequency voltage and a DC voltage are superimposed) from the power supply unit 24, respectively. It is applied. A predetermined voltage is also applied from the power supply unit 24 to the electrodes (not shown) arranged in the collision cell 232. Further, the CID gas is continuously (or intermittently) supplied into the collision cell 232 at a predetermined pressure.

Therefore, among the various ions sent to the front-stage quadrupole mass filter 231, only the ions having a specific mass-to-charge ratio according to the voltage applied to the main rod electrode 2311 of the front-stage quadrupole mass filter 231 are the only ions. It passes through the filter 231 and is introduced into the collision cell 232 as precursor ions. The precursor ions are accelerated in the collision cell 232 to an acceleration corresponding to the voltage applied to the electrodes arranged therein, collide with the CID gas with a predetermined collision energy, and dissociate. As a result, various product ions are generated. When various generated product ions are introduced into the rear quadrupole mass filter 234, a product having a specific mass-to-charge ratio according to the voltage applied to the main rod electrode 2341 of the rear quadrupole mass filter 234. Only ions pass through the filter 234 and reach the ion detector 235 for detection. The ion detector 235 is, for example, a pulse count type detector, and outputs a number of pulse signals corresponding to the number of incident ions to the control unit 3 as detection signals.

<Control unit 3>
The control unit 3 is configured with a personal computer as a hardware resource, and is connected to a display unit 31 including a display and the like and an input unit 32 including a keyboard and a mouse. The control unit 3 is electrically connected to the liquid chromatograph unit 1 and the mass spectrometer 2, and manages the analysis work, analyzes and processes the data obtained by the ion detector 235, and the like.

The liquid chromatograph mass spectrometer 100 has a function of determining an optimum value of a control parameter related to MRM measurement (hereinafter, also referred to as a “control parameter optimization function”). The control parameters to be optimized here are the voltage applied to the prerod electrode 2312 of the front-stage quadrupole mass filter 231 (hereinafter, also referred to as "Q1 prerod Bias"), and the rear-stage quadrupole mass filter. The voltage applied to the prerod electrode 2342 of 234 (hereinafter, also referred to as "Q3 Prerod Bias") and the energy when the precursor ion collides with the CID gas in the collision cell 232 (specifically, this is). (Defined by the voltage applied to the electrodes arranged in the collision cell 232) (hereinafter, also referred to as "collision energy (CE)").

In the control unit 3, a method file setting unit 301, a measurement control unit 302, and an optimum value determination unit 303 are realized as functional blocks related to the control parameter optimization function. At least a part of each of these parts 301, 302, and 303 is realized by executing the dedicated control / processing software installed in the personal computer on the computer.

The method file setting unit 301 sets the method file. The "method file" is a file that describes the operation contents and measurement conditions of the liquid chromatograph unit 1 and the mass spectrometer 2 in the MRM measurement.

The measurement control unit 302 operates the operations of each part of the liquid chromatograph unit 1 and each part of the mass spectrometer 2 (specifically, the operation of the pump 11, the injector 12, the power supply unit 24, the CID gas supply unit (not shown), and the like. ) Is controlled according to the method file, and the liquid chromatograph unit 1 and the mass spectrometer 2 are made to perform the MRM measurement in the mode described in the method file.

The optimum value determination unit 303 determines the optimum value of each parameter to be optimized based on the measurement data obtained by the MRM measurement.

<2. Control parameter optimization>
The flow of processing related to the optimization of control parameters will be described with reference to FIG. FIG. 2 is a diagram showing the flow of the process.

Step S1: Setting the method file First, the method file setting unit 301 sets a method file for MRM measurement of a sample (hereinafter, also referred to as “target sample”) used for processing related to optimization of control parameters. However, it is assumed that this target sample contains a plurality of types of compounds.
The process of step S1 will be specifically described with reference to FIGS. 3 and 4 in addition to FIG. FIG. 3 is a diagram showing a configuration example of a reception screen 9 for receiving various input operations related to the setting of the method file from the operator. FIG. 4 is a diagram for explaining a mode in which each value of the Q1 prerod voltage, the Q3 prerod voltage, and the collision energy is set for each channel.

Step S11: Creation of event When the analyst inputs an instruction to start setting the method file via the input unit 32, the method file setting unit 301 displays various types related to the method file setting on the display unit 31. The reception screen 9 for accepting the input operation of is displayed from the operator. On the reception screen 9, fields for accepting input of various setting items are displayed, and the analyst can set various measurement conditions and the like by inputting desired numerical values and the like in each input field. Since there are a wide variety of setting items, only some of the setting items are shown in the example shown in the figure.

The analyst specifies and inputs one or more compounds (target compounds) to be quantified contained in the target sample on the reception screen 9 via the input unit 32 (item 91). Further, the analyst specifies and inputs one or more mass-to-charge ratios (MRM transitions) of the target precursor ions and product ions for each target compound (item 92). Further, the analyst specifies and inputs a measurement time range for each MRM transition (item 93).

The method file setting unit 301 receives the information specified and input by the analyst in each item 91, 92, 93 and sets it in the method file. At this time, the method file setting unit 301 accepts one MRM transition as one event and manages it in the method file. In the liquid chromatograph mass spectrometer 100, for example, about 1000 events are stored in one method file (that is, a method file that describes the operation contents and measurement conditions related to MRM measurement associated with one sample introduction). It is possible to set a plurality of channels for which different measurement conditions are specified for each event.

Step S12: Channel setting Next, the method file setting unit 301 assigns a plurality of channels to each of the one or more events set in step S11, and assigns the Q1 prerod voltage, the Q3 prerod voltage, and the Q3 prerod voltage to each channel. Set each value of collision energy. Hereinafter, the process of step S12 will be described more specifically.

Step S121: Setting of First Channel Group First, the method file setting unit 301 specifies a candidate value of a group of Q1 prerod voltage and a candidate value of a group of Q3 prerod voltage, respectively. The candidate value may be, for example, a value obtained by taking a range in which the Q1 prerod voltage (or the Q3 prerod voltage) can be taken at predetermined intervals (for example, in 5V increments). Then, the method file setting unit 301 creates all combinations (Q1-Q3 combinations) of the candidate values of the group of Q1 pre-rod voltages and the candidate values of the group of Q3 pre-rod voltages.

Subsequently, the method file setting unit 301 sets the same number of channels as the number of created Q1-Q3 combinations based on each event created in step S11, and is created for each of the group of channels. Assign one of a group of Q1-Q3 combinations. That is, each candidate value of the Q1 pre-rod voltage and the Q3 pre-rod voltage related to each Q1-Q3 combination is set in the value of each voltage of each channel.

Further, the method file setting unit 301 sets the collision energy of the same value in all the channels of the group (that is, all the channels of the group to which different Q1-Q3 combinations are assigned). The collision energy value set here can be arbitrarily selected from an appropriate range (that is, a range of collision energy such that precursor ions can be cleaved to generate product ions).

As a result, a group of channels (that is, a group of channels in which different Q1-Q3 combinations are assigned and the same collision energy values are set for each other) are assigned to each of the one or more events created in step S11. Set. These groups of channels are also hereinafter referred to as "first channel groups".

Step S122: Setting of Second Channel Group Next, the method file setting unit 301 identifies a candidate value of a group of collision energies. As described above, the candidate value may be, for example, a value obtained by taking a range in which collision energy can be taken at predetermined intervals (for example, in 5V increments).

Subsequently, the method file setting unit 301 sets the same number of channels as the number of candidate values of the group of collision energies based on each event created in step S11, and sets the collision energy in each of the channels of the group of collision energies. Assign one of the candidate values for. That is, each candidate value is set for the collision energy value of each channel.

Further, the method file setting unit 301 sets the Q1 prerod voltage of the same value to all the channels of the group (that is, all the channels of the group to which different collision energy values are assigned). Further, the same value of Q3 prerod voltage is set for all the channels of the group. Each value of the Q1 pre-rod voltage and the Q3 pre-rod voltage set here can also be arbitrarily selected from an appropriate range.

As a result, each of the one or more events created in step S11 is assigned a group of channels (ie, different collision energy values, the same Q1 prerod voltage values are set for each other, and the same Q3 prerod voltage values for each other. A group of channels with the value of) set. These groups of channels are also hereinafter referred to as "second channel groups".

The method file setting unit 301 further sets other setting items (for example, each channel included in the first channel group and each channel included in the second channel group) set for each event. The execution time per channel (so-called dwell time, etc.) is set, and the process of step S12 is completed thereby.

This completes the method file settings. The set method file is preferably displayed on the reception screen 9 in response to an instruction from the analyst, for example. For example, as illustrated in FIG. 3, on the reception screen 9, a column (first column) 901 for displaying a group of events is provided, and when an analyst selects one of the events from this column (in the illustrated example, in the illustrated example). (Event No. 1 is selected), a group of channels set for the selected event may be displayed in the second column 902.

Step S2: MRM measurement A method file for MRM measurement of the target sample is set, and when the analyst inputs an instruction to start measurement, the measurement control unit 302 performs the liquid chromatograph unit 1 and the mass in response to the instruction. Have the analyzer 2 perform the MRM measurement in the manner described in the method file. That is, here, the mass spectrometer 2 and the measurement control unit 302 cooperate to form a measurement unit that performs MRM measurement on the target sample.

Specifically, in the liquid chromatograph unit 1, under the control of the measurement control unit 302, the pump 11 feeds the mobile phase stored in the mobile phase container 10 toward the column 13, and the movement to be fed. The target sample is introduced from the injector 12 during the phase. While the target sample passes through the column 13, various compounds in the target sample are separated in the time direction and sequentially introduced into the mass spectrometer 2.

In the mass spectrometer 2, the measurement related to each event (specifically, each channel set for each event) specified in the method file is executed within the measurement time range set for each event. ..
Specifically, the compound introduced into the mass spectrometer 2 is ionized in the ionization chamber 20, converged in the first intermediate vacuum chamber 21 and the second intermediate vacuum chamber 22, and then sent to the analysis chamber 23. Be done. The measurement control unit 302 controls each unit of the analysis chamber 23 according to the information set for the channel to be executed. For example, at the time when the measurement related to "ch3 of event No. 1" is executed in the example of FIG. 3, an ion having a mass-to-charge ratio of "111.30" is selected as a precursor ion for the main rod electrode 2311 of the previous quadrupole mass filter 231. A voltage is applied to the main rod electrode 2341 of the subsequent quadrupole mass filter 234 so as to select an ion having a mass-to-charge ratio of "27.60" as a product ion. Further, a voltage of "-30V" is applied to the pre-rod electrode 2312 of the front-stage quadrupole mass filter 231 and a voltage of "-20V" is applied to the pre-rod electrode 2342 of the rear-stage quadrupole mass filter 234. Further, a voltage of "-25V" is applied to the electrodes in the collision cell 232. In this way, the MRM measurement related to each event (specifically, each channel set in each event) specified in the method file is executed. Note that each event is allowed to overlap in the measurement time range, and in the time zone in which the measurement time ranges of a plurality of events overlap, the channels set for the plurality of events are switched in a predetermined short cycle. Will be executed.

As mentioned above, multiple events include those that target different compounds. That is, here, MRM measurements for each of the plurality of types of compounds are performed sequentially (or in parallel).

Further, as described above, a first channel group and a second channel group are set for each event. Therefore, in step S2, for each event, the first measurement step of performing MRM measurement while fixing the collision energy value to a constant value and changing the combination of the Q1 prerod voltage value and the Q3 prerod voltage value. (Step S21) and the second measurement step (step S22) of performing MRM measurement while changing the collision energy value while fixing each value of the Q1 prerod voltage and the Q3 prerod voltage to a constant value are executed. Will be. However, the first measurement step and the second measurement step do not necessarily have to be performed in this order, but may be performed in the reverse order, or in parallel (that is, the channel included in the first channel group and the first measurement step). It may be performed (while switching between the channels included in the two-channel group and the channels included in a predetermined short cycle).

Step S3: Determining the optimum value of each control parameter When the MRM measurement of the target sample is completed, the optimum value determining unit 303 determines the optimum value of each control parameter based on the measurement data obtained for each event.

Specifically, the optimum value determination unit 303 identifies the channel to which the strongest detection signal is given in the first measurement step (step S21), and sets the value of the Q1 prerod voltage set in the channel to Q1. The optimum value of the prerod voltage is determined, and the value of the Q3 prerod voltage set in the channel is determined as the optimum value of the Q3 prerod voltage (first determination step) (step S31). Further, the optimum value determination unit 303 identifies the channel to which the strongest detection signal is given in the second measurement step (step S22), and sets the collision energy value set in the channel to the optimum value of the collision energy. (Second determination step) (step S32). However, the first determination step and the second determination step do not necessarily have to be performed in this order, and may be performed in the reverse order or may be performed in parallel.

By executing the processes of steps S31 to S32 for the measurement data obtained in each event, the optimum value of each control parameter corresponding to the MRM transition specified in each event is determined. .. As mentioned above, multiple events include those that target different compounds. That is, here, the optimum value of each control parameter is determined for each of the plurality of types of compounds (more specifically, each of the MRM transitions set for each compound).

As described above, here, the optimum value of each control parameter is determined after the first measurement step (step S21) and the second measurement step (step S22) are completed. That is, the optimum value of the collision energy has not yet been specified at the stage where the first measurement step (step S21) is being performed, and the Q1 prerod is still at the stage where the second measurement step (step S22) is being performed. Optimal values for voltage and Q3 prerod voltage have not been specified. That is, in the first measurement step (step S21), the collision energy is not always fixed to the optimum value, and in the second measurement step (step S22), the Q1 prerod voltage and the Q3 prerod voltage are fixed to the optimum values, respectively. It is not always done.
According to various experiments and discussions, the inventors of the present case have shown that each value of the Q1 prerod voltage and the Q3 prerod voltage affects the ion introduction mode, and the collision energy value affects the way the precursor ions are destroyed. , It has been found that each pre-rod voltage and collision energy are independent control parameters without correlation, and from this knowledge, the optimum value of each control parameter is specified with sufficient accuracy even in the above embodiment. I guessed it could be done. Then, the inventors have actually confirmed by experiments that the optimum value of each control parameter can be specified with sufficient accuracy by the above-mentioned embodiment.

<3. Time required for MRM measurement>
For example, when the target sample contains 500 compounds (target compounds), the analyst specifies and inputs one mass-to-charge ratio of the target precursor ion for each target compound, and 1 for each precursor ion. It is assumed that the mass-to-charge ratio of the product ions is specified and input (that is, 500 MRM transitions are specified and input). In this case, in step S1 above, 500 events are set in the method file, and a plurality of channels are set for each event. Then, in step S2 above, the 500 events are executed in the MRM measurement of the target sample. Then, in step S3 above, the optimum value of each control parameter corresponding to each of the 500 events (that is, each of the 500 MRM transitions) (that is, each optimum value of the three types of control parameters) is determined. To. As described above, according to the above configuration, the optimum value of each control parameter corresponding to each of 500 (or more) target compounds can be determined by one MRM measurement accompanying one sample introduction.

Conventionally, in order to determine the optimum value of each control parameter corresponding to one MRM transition, three MRM measurements associated with three sample introductions have been required. That is, conventionally, in order to determine the optimum value of each control parameter corresponding to each of 500 target compounds, for example, 1500 times of sample introduction and 1500 times of MRM measurement (temporarily for one MRM measurement). Assuming that the required time is 0.5 minutes, a measurement time of 750 minutes) was required. According to the above embodiment, since this requires only one sample introduction and one MRM measurement, the number of required samples is reduced from 1500 to 1, and the time required for MRM measurement is reduced from 750 minutes to 0. It will be shortened to 5 minutes.

<4. Other embodiments>
In the above embodiment, the control parameters to be optimized are the Q1 pre-rod voltage, the Q3 pre-rod voltage, and the collision energy, but there are other control parameters (for example, DL bias, etc.). Qarray bias, etc.) may be added to the optimization target.

Further, in the above embodiment, the column 13 of the liquid chromatograph unit 1 is not essential, and the target sample does not necessarily have to pass through the column 13. When the target sample is introduced into the mass spectrometer 2 without passing through the column 13, various compounds in the target sample are introduced into the mass spectrometer 2 at the same time. In this case, the measurements related to each event specified in the method file are executed in parallel (more accurately, the measurements are performed in order while switching the channels set for each event).

Further, in the above embodiment, the target sample may contain only one kind of compound.

Further, since the above embodiment is an example of the present invention, it is clear that even if it is appropriately modified, added, or modified within the scope of the purpose of the present invention, it is included in the scope of claims of the present application.

100 Liquid chromatograph mass spectrometer 1 Liquid chromatograph unit 2 Mass spectrometer 20 Ionization chamber 21 First intermediate vacuum chamber 22 Second intermediate vacuum chamber 23 Analysis chamber 231 First stage quadrupole mass filter 2311 Main rod electrode 2312 Pre-rod electrode 232 Collision Cell 234 Rear quadrupole mass filter 2341 Main rod electrode 2342 Pre-rod electrode 235 Ion detector 3 Control unit 301 Method file setting unit 302 Measurement control unit 303 Optimal value determination unit

Claims (4)

This is a control parameter optimization method that determines the optimum control parameters for a compound in a tandem quadrupole mass spectrometer that has a quadrupole mass filter equipped with prerod electrodes in front of and behind the collision cell that cleaves ions. hand,
a) A measurement step for performing MRM measurement on a sample containing the compound, and
b) A determination step of determining the optimum value of the control parameter based on the measurement result obtained by the measurement step, and a determination step.
With
The measurement process
a1) Change the combination of the pre-rod voltage value of the quadrupole mass filter in the front stage and the pre-rod voltage value of the quadrupole mass filter in the rear stage while fixing the collision energy value to a constant value that is not limited to the optimum value. While the first measurement step of performing the MRM measurement,
With
The determination process
b1) In the first measurement step, the combination that gives the strongest detection signal is the combination of the optimum value of the prerod voltage of the quadrupole mass filter in the first stage and the optimum value of the prerod voltage of the quadrupole mass filter in the second stage. The first decision process to decide,
Control parameter optimization method. The control parameter optimization method according to claim 1.
The measurement process
a2) The MRM measurement while changing the value of the collision energy while fixing each value of the pre-rod voltage of the quadrupole mass filter in the first stage and the pre-rod voltage of the quadrupole mass filter in the second stage to a constant value. Second measurement step,
With
The determination process
b2) In the second measurement step, the second determination step of determining the value of the collision energy to which the strongest detection signal is given as the optimum value.
Control parameter optimization method. The control parameter optimization method according to claim 1 or 2.
In the measurement step, MRM measurement is performed on a sample containing a plurality of types of compounds.
A control parameter optimization method in which an optimum value of a control parameter is determined for each of the plurality of types of compounds in the determination step. A tandem quadrupole mass spectrometer having a quadrupole mass filter equipped with a pre-rod electrode in front of and behind a collision cell that cleaves ions.
a) A measuring unit that performs MRM measurement on a sample containing a compound,
b) An optimum value determination unit that determines the optimum value of the control parameter for the compound based on the measurement result obtained by the measurement step.
With
The measuring unit
While fixing the collision energy value to a constant value that is not limited to the optimum value, changing the combination of the pre-rod voltage value of the quadrupole mass filter in the front stage and the pre-rod voltage value of the quadrupole mass filter in the rear stage. , Perform the MRM measurement
The decision part
In the MRM measurement, the combination that gives the strongest detection signal is determined as the combination of the optimum value of the prerod voltage of the quadrupole mass filter in the first stage and the optimum value of the prerod voltage of the quadrupole mass filter in the second stage. Tandem quadrupole mass spectrometer.

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