阅读说明：本技术 质量分析装置及质量分析方法 (Mass spectrometer and mass spectrometry method ) 是由 桥本雄一郎 于 2019-07-24 设计创作，主要内容包括：本发明实现廉价且能获得高精度的定量结果的质量分析装置。小区间测量指令部(101)指令检测器(9)在信道(4)中的多个小区间(5)中实施测量,将由检测器(9)检测到的信号存储在数据存储部(102)中,利用小区间信号量累计部(103)对信号进行累计,利用信号偏差计算部(104)计算所累计的信号的偏差。信号偏差评价部(105)评价每个小区间5的信号在同一信道4中的信号偏差。在评价为稳定时,动作控制部(106)控制离子源(6)的动作,以无警告的方式直接继续测量。在评价为不稳定时,在测量中或测量后实施警告。(The invention provides a mass spectrometer which is cheap and can obtain high-precision quantitative results. An inter-cell measurement instruction unit (101) instructs a detector (9) to perform measurement in a plurality of cells (5) in a channel (4), stores a signal detected by the detector (9) in a data storage unit (102), integrates the signal by an inter-cell signal amount integration unit (103), and calculates the deviation of the integrated signal by a signal deviation calculation unit (104). A signal deviation evaluation unit (105) evaluates the signal deviation of the signal in each cell 5 in the same channel 4. When the evaluation is stable, the operation control unit (106) controls the operation of the ion source (6) and directly continues the measurement without warning. If the evaluation is not stable, a warning is given during or after the measurement.)

1. A mass spectrometry apparatus comprising: an ion source that ionizes a measurement sample sent from a chromatography device; a mass analysis section having a detector that detects ions generated by the ion source and that analyzes mass; and a controller for generating a plurality of data including elution time and signal intensity for the ions analyzed by the mass spectrometer, wherein,

the controller divides the plurality of data into a plurality of channels, divides each of the plurality of channels into a plurality of cells, controls the detector to detect data for each of the divided plurality of cells, and determines whether the ion source is stable or unstable based on the data for the divided plurality of cells.

2. The mass spectrometry apparatus according to claim 1,

the controller calculates a mean and a standard deviation of data among a plurality of the cells, and determines whether the ion source is stable or unstable based on the mean and the standard deviation.

3. The mass spectrometry apparatus according to claim 2,

also comprises a display part which is used for displaying the information,

the controller displays on the display whether the ion source is stable or unstable.

4. The mass spectrometry apparatus according to claim 2,

the controller changes ion generation conditions of the ion source when it is determined that the ion source is unstable.

5. The mass spectrometry apparatus according to claim 3 or 4,

the controller includes a data storage part storing data between the cells, and deletes the data between the cells stored in the data storage part after completing calculation of an average value and a standard deviation of the data between the cells.

6. The mass spectrometry apparatus according to any one of claims 1, 2, 3, 4, and 5,

the chromatography apparatus is a liquid chromatography apparatus.

7. A mass spectrometry method for detecting ions generated by an ion source for ionizing a measurement sample sent from a chromatography apparatus, analyzing the mass of the ions, and generating a plurality of data including elution time and signal intensity for the analyzed ions,

the method includes dividing the plurality of data into a plurality of channels, dividing each of the plurality of channels into a plurality of cells, detecting data for each of the plurality of divided cells, and determining whether the ion source is stable or unstable based on the data for the plurality of divided cells.

8. The mass spectrometry method according to claim 7,

calculating a mean and a standard deviation of data across a plurality of the cells, and determining whether the ion source is stable or unstable based on the mean and the standard deviation.

9. The mass spectrometry method according to claim 8,

displaying whether the ion source is stable or unstable on a display.

10. The mass spectrometry method according to claim 8,

the controller changes ion generation conditions of the ion source when it is determined that the ion source is unstable.

11. The mass spectrometry method according to claim 9 or 10,

and storing the data of the cells in a data storage unit, and deleting the data of the cells stored in the data storage unit after the calculation of the average value and the standard deviation of the data of the cells is completed.

12. The mass spectrometry method according to any one of claims 7, 8, 9, 10, and 11,

the chromatography apparatus is a liquid chromatography apparatus.

Technical Field

The present invention relates to a mass spectrometer and a mass spectrometry method, which are combined with a chromatograph, such as a gas chromatography mass spectrometer (GC/MS) or a liquid chromatography mass spectrometer (LC/MS).

Background

As one method of mass analysis, a method called MS/MS analysis (tandem analysis) is widely used. As a mass spectrometer for performing MS/MS analysis, there are various structures, but a triple quadrupole mass spectrometer is relatively simple in structure and easy to operate.

Patent document 1 and non-patent document 1 describe the structure and operation method of a general triple quadrupole mass spectrometer. Ions from a sample component generated by an ion source are introduced into a pre-stage quadrupole mass filter (Q1), and ions having a specific mass-to-charge ratio (m/z) are classified as precursor ions. The precursor ions are introduced into a collision cell (Q2). Nitrogen gas or the like is supplied into the collision cell, and the precursor ions collide with the gas in the collision cell to be dissociated (CID), thereby generating product ions. The product ions are mass-classified by a post-quadrupole mass filter (Q3) and passed to a detector for detection.

The triple quadrupole mass spectrometer may be used alone, but is generally used in combination with a chromatograph such as a Gas Chromatograph (GC) or a Liquid Chromatograph (LC).

The MS/MS analysis in the triple quadrupole mass spectrometer includes measurement modes such as an MRM (Multiple Reaction Monitoring) measurement mode, an SIM (Selected Ion Monitoring) measurement mode, a precursor Ion scanning measurement mode, a product Ion scanning measurement mode, and a neutral loss scanning measurement mode.

In the triple quadrupole mass spectrometer, since various components in a sample are temporally separated in a chromatograph, ion intensity signals from different compounds can be obtained by sequentially switching and continuously performing a SIM measurement mode or an MRM measurement mode for ions of different mass-to-charge ratios. In particular, in measurements requiring quantitative accuracy, the following method is generally used: the accuracy of quantification is improved by performing calibration after MRM measurement corresponding to each compound is performed using a compound to be measured and a similar compound (isotope or the like) of a known concentration.

When these measurements are performed, the signal intensity in the mass spectrometer may become unstable due to instability of ionization, contamination of voltage electrodes of the mass spectrometer, or instability of applied voltage.

Since a correct result cannot be obtained using a mass spectrometer when the signal intensity becomes unstable, it is important to suppress inaccurate measurement by preventing it from occurring and quickly monitoring and giving a warning when these situations actually occur.

In particular, as for instability of ionization, since it is not monitored as easily as the applied voltage, a current monitoring method and constant fluidization of an ion source are being studied.

Patent document 2 describes that a stable atmospheric pressure chemical ion source is realized by monitoring a discharge current of corona discharge for ionization of the atmospheric pressure chemical ion source and changing an applied voltage to keep the current constant.

Patent document 3 describes that a stable electrospray ion source is realized by monitoring a probe current for ionization of the electrospray ion source and changing a probe application voltage to keep the current constant.

However, in the ion source for liquid, it is known that ionization efficiency varies depending on the spray state of the spray of the liquid sample, and even when a discharge current or a probe current is monitored and made constant, stable signal intensity may not be obtained.

Patent document 4 describes a method of monitoring the spray state in addition to monitoring the probe current of the electrospray ion source, and controlling the probe position and the probe applied voltage to return to the normal state.

Further, a method of obtaining a predetermined signal intensity by controlling the position of the ion source and applying a voltage by using a known sample such as a calibration sample is described.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2003-172726

Patent document 2: japanese patent laid-open No. 2008-262922

Patent document 3: U.S. Pat. No. 6452166 publication

Patent document 4: U.S. patent application publication No. 20050072915

[ non-patent document ]

Non-patent document 1: anal. chem.1990, 62.2162-2172 Tandem-in-Space and Tandem-in-Time Mass Spectrometry: triple quadrupololes and quadrupolole Ion trains Jodie V.Johnson and Richard A.Yost

Disclosure of Invention

Technical problem to be solved by the invention

However, the correlation between the measurement of the current value of the ion source, the observation of the spray state, and the actually obtained signal intensity, which is used as the monitoring method for the stabilization of the ion source in the related art, is low. Therefore, in the mass analysis section, when the ion source becomes unstable due to contamination of the ionization probe or the like, a correct quantitative result cannot be obtained, and high quantitative accuracy cannot be obtained.

Further, in the prior art, a current measuring device, a CCD device for spray measurement, and the like are necessary, and corresponding costs are required.

Further, in order to improve the correlation with the signal intensity, when measurement is performed using a known sample such as a calibration sample, the following problems arise: special sample introduction units are required, or in order to measure samples of known concentration, restrictions on the schedule of normal measurements are imposed, etc.

The purpose of the present invention is to realize a mass spectrometer and a mass spectrometry method that are inexpensive and can obtain quantitative results with high accuracy.

Technical scheme for solving technical problem

To achieve the above object, the present invention is configured as follows.

A mass spectrometry apparatus comprising: an ion source that ionizes a measurement sample sent from a chromatography device; a mass analysis section having a detector that detects ions generated by the ion source and that analyzes mass; and a controller that generates a plurality of data including an elution time and a signal intensity for the ions analyzed by the mass analyzer, wherein the controller divides the plurality of data into a plurality of channels, divides each of the plurality of channels into a plurality of cells, controls the detector to detect data for each of the plurality of divided cells, and determines whether the ion source is stable or unstable based on the data of the plurality of divided cells.

A mass spectrometry method for detecting ions generated by an ion source that ionizes a measurement sample sent from a chromatography apparatus, analyzing the mass of the ions, and generating a plurality of data including elution time and signal intensity for the analyzed ions, wherein the plurality of data are divided into a plurality of channels, each of the plurality of channels is divided into a plurality of cells, the data are detected for each of the plurality of divided cells, and whether the ion source is stable or unstable is determined based on the data of the plurality of divided cells.

Effects of the invention

According to the present invention, a mass spectrometer and a mass spectrometry method can be realized which are inexpensive and can obtain quantitative results with high accuracy.

Drawings

Fig. 1 is a diagram showing a schematic configuration of a liquid chromatography mass spectrometer.

Fig. 2 is an explanatory diagram of a data structure in the liquid chromatography mass spectrometer in example 1 of the present invention.

Fig. 3 is an operation flowchart of embodiment 1.

Fig. 4 is an internal functional block diagram of the controller in embodiment 1.

Fig. 5 is a graph showing an example of signals in a cell obtained in a cycle around a peak of a chromatogram.

Fig. 6 is a graph showing other examples of inter-cell signals obtained in a cycle around a chromatographic peak.

FIG. 7 is an operation flowchart of embodiment 2.

Detailed Description

Embodiments of the present invention are explained with reference to the drawings.

[ examples ]

(example 1)

An example in which the present invention is applied to a liquid chromatography mass spectrometer is described below.

Fig. 1 is a diagram showing a schematic configuration of a liquid chromatography mass spectrometer 100.

In fig. 1, a liquid chromatography mass spectrometer 100 includes a liquid chromatography device 11, an ion source 6, a mass spectrometer 8, and a controller 10. The mass analyzing section 8 includes a mass separating section 7 and a detector 9.

In the liquid chromatography mass spectrometer 100, a solution (measurement sample) sent from the liquid chromatography apparatus 11 is ionized by the electrospray ion source or the atmospheric pressure chemical ion source plasma source 6.

Ions generated by the ion source 6 are introduced into the mass spectrometer 8 in vacuum, separated by various mass separators 7 such as a quadrupole type, a time-of-flight type, and a magnetic field type, and detected as a signal by the detector 9. The signal detected by the detector 9 is processed by the controller 10, and a plurality of data including the elution time and the signal intensity are generated for the ions analyzed by the mass spectrometer 8, and the generated data is divided into a plurality of channels.

The controller 10 may control the ion source 6, the mass separating portion 7, the detector 9, and the like in addition to the signal processing.

Fig. 2 is an explanatory diagram of a data structure in the liquid chromatography mass spectrometer 100 in example 1 of the present invention. The example shown in fig. 2 shows a typical chromatogram obtained when measurement is performed with the liquid chromatography mass spectrometry apparatus 100.

In fig. 2, the horizontal axis of the chromatogram represents the elution time indicating the elution timing of LC and GC, and the vertical axis represents the total value of signal intensity.

In the example shown in fig. 2, chromatographic peak 1 is detected. In the MRM measurement, measurement is performed by changing measurement conditions such as (m/z) to be measured and lens voltage conditions associated with the (m/z) for each channel (also referred to as a zone). For each point of these signals, the integrated value of the measured signal amount in a plurality of channels having different measurement methods is plotted.

Generally, the signal accumulation time of one channel 4 of these plural channels is set to about 1 to 100 ms. In addition, the number of channels is set to about 1 to 100. One period of the channel set where one measurement is made is called a cycle. One cycle is usually set to about 50 to 1000 ms. The nth cycle 2 and the N +1 th cycle 3 are shown enlarged in fig. 2.

The above description is of a measurement method generally performed in a chromatography mass spectrometer.

In embodiment 1 of the present invention, the inside of a channel 4 measured under the same measurement condition is divided into a plurality of cell segments 5, and a measurement value is obtained in each of them. The measurement conditions are the same in the cells 5 of the same channel. The time between the cells 5 is typically about 10 to 1000 us. In these cells 5, the signal amounts (data amounts) are accumulated to determine their deviations.

As the index of the deviation, there are indices such as the difference between the maximum value and the minimum value, the standard deviation, the kurtosis, and the distortion degree, and it is possible to determine whether the deviation is significantly deteriorated with respect to a reference value obtained from a statistical randomness, an empirical rule, and the like by using these indices.

Therefore, it can be determined whether or not ions are stably generated in the ion source 6.

Fig. 3 is an operation flowchart of embodiment 1 of the present invention, and is an explanatory diagram of an operation capable of ensuring measurement reliability and making a user know maintenance timing. Fig. 4 is an internal functional block diagram of the controller 10 according to embodiment 1.

In fig. 4, the controller 10 includes an inter-cell measurement command unit 101, a data storage unit 102, an inter-cell signal amount accumulation unit 103, a signal deviation calculation unit 104, a signal deviation evaluation unit 105, and an operation control unit 106.

In fig. 3 and 4, the inter-cell measurement instructing unit 101 instructs the detector 9, and controls the detector 9 to detect data for each of the plurality of inter-cells 5 in the channel 4 in which the measurement conditions are the same (step S1). Then, the signal detected by the detector 9 is stored in the data storage unit 102, the signal (data) stored in the data storage unit 102 is accumulated by the inter-cell signal amount accumulation unit 103, and the deviation of the accumulated signal is calculated by the signal deviation calculation unit 104 (step S2).

Then, the signal deviation evaluation unit 105 evaluates the signal deviation of the signal of each cell 5 in the same channel 4 (step S3). In the evaluation (determination) of the signal deviation, the stability is evaluated based on a predetermined deviation evaluation method (determination of whether the ion source 6 is stable or unstable).

When the ion source is judged to be stable in step S3, the operation controller 106 controls the operation of the ion source 6 and directly continues the measurement without warning (step S4). As a result, the ion source 6 in the measurement is stable, and becomes proof (evidence) of measurement validity. The validity of the measurement can be verified by issuing a command from the signal deviation evaluation unit 105 to the display unit 20 and displaying that the measurement is appropriate.

In the example shown in fig. 4, the display unit 20 is disposed separately from the controller 10, but the display unit 20 may be integrated with the controller 10. Instead of the display unit 20, a storage unit may be used to store the measured signal as appropriate.

On the other hand, when it is evaluated as unstable in step S3, a warning is given during or after the measurement (step S5).

As a method of warning, there are a method of displaying attention to measurement accuracy on the display unit 20 and a method of issuing a warning to a user to suggest maintenance. Alternatively, a method of operating an automatic maintenance function built in the liquid chromatography mass spectrometer 100 may be used. One or more of the above may be performed based on an alarm issued by the functionality of the present invention.

Next, an example of practical application to measurement in embodiment 1 will be explained.

Fig. 5 is a graph showing the intra-cell signal (signal) obtained in the cycle around the chromatographic peak when LC mass analysis of testosterone was performed. The channel measurement time in the data shown in fig. 5 is 40ms, and the time width of the inter-cell 5 is 0.4 ms. The average value of the signal for each cell 5 was 10.4, and the standard deviation as an index of deviation was 3.5.

The above signal mean, standard deviation can be explained by the poisson distribution observed when measuring rare phenomena. It is well known that in a poisson distribution, the standard deviation is the square root of N for an event whose mean is N.

In the example shown in fig. 5, the standard deviation predicted from the average value 10.4 of the signal is 3.2, and the obtained measurement value 3.5 is judged as a normal state that is not regarded as a significant deviation.

Fig. 6 is a graph showing other examples of inter-cell signals obtained in a cycle around a chromatographic peak. The channel measurement time in the data shown in fig. 6 is 40ms, and the time width of the inter-cell 5 is 0.4 ms.

As compared with the example shown in fig. 5, it can be seen that the signal greatly fluctuates in the example shown in fig. 6. The average value of the signal for each cell 5 was 4.5, and the standard deviation as an index of deviation was 4.1. In the same estimation as the example shown in fig. 5, the standard deviation predicted from the average value 4.5 is 2.1, whereas the standard deviation 4.1 of the obtained measurement values can be judged to be significantly large. As a result, it can be judged that the ion source 6 is unstable in the measurement shown in fig. 6.

By applying example 1 of the present invention to a liquid chromatography mass spectrometer in this manner, a mass spectrometer and a mass spectrometry method that are inexpensive and can obtain quantitative results with high accuracy can be realized without using special equipment. In addition, an inexpensive and highly accurate method of monitoring the stability of the device can be provided and can be fed back into the maintenance and optimization of the device.

Further, after the indexes and the total values of the deviations are calculated by measuring the cell segments 5 (after the average value and the standard deviation of the data are calculated), the respective signal amounts of each cell segment 5 may be deleted from a storage and storage device (data storage unit 102) such as a hard disk.

Therefore, the signal data accumulated in each cell 5 can be greatly reduced, and the present invention can be implemented even with a small number of memory storage devices.

(example 2)

Next, example 2 of the present invention is explained.

Fig. 7 is an operation flowchart of embodiment 2 of the present invention, and is an explanatory diagram of an operation capable of automatically adjusting the measurement conditions of the ion source 6.

As in example 1, example 2 is an example of a case where it is applied to the liquid chromatography mass spectrometer 100. Since the schematic configuration of the liquid chromatography mass spectrometer 100 and the internal functional blocks of the controller 10 are the same as those shown in fig. 1 and 3, the illustration and detailed description thereof are omitted.

The measurement condition (ion generation condition) of the ion source 6 is determined by a voltage applied to the ion source 6, a gas flow rate for spraying, heating, a temperature of the ion source 6, and the like. These parameter adjustments are typically performed by a user, but can be automated by using embodiment 2 of the present invention.

In fig. 7 and 4, the inter-cell measurement command unit 101 instructs the detector 9 to perform measurement in a plurality of inter-cells 5 in the channel 4 under the same measurement condition (step S1). Then, the signal detected by the detector 9 is stored in the data storage unit 102, the signal (data) stored in the data storage unit 102 is accumulated by the inter-cell signal amount accumulation unit 103, and the deviation of the accumulated signal is calculated by the signal deviation calculation unit 104 (step S2).

Then, the signal deviation evaluation unit 105 evaluates the signal deviation of the signal of each cell 5 in the same channel 4 (step S3). Evaluation of signal deviation stability was evaluated based on a predetermined deviation evaluation method.

When the signal deviation evaluation unit 105 evaluates that the signal deviation is stable in step S3, the adjustment is completed (step S6)).

On the other hand, when the signal deviation evaluation unit 105 evaluates that the signal deviation is unstable in step S3, the operation control unit 106 changes conditions (ion generation conditions) such as the voltage and position applied to the ion source 6, the gas flow rate for spraying or heating, and the temperature of the ion source 6 (step S7), and performs measurement again (step S1).

By repeatedly performing these processes (steps S1 to S3, S7), the optimum measurement conditions (ion generation conditions) can be automatically set.

In example 2, as in example 1, after the cell 5 is measured and the index of the deviation and the total value are calculated, the respective signal amounts for each cell 5 may be deleted from the storage and storage device (data storage unit 102) such as a hard disk, thereby significantly reducing the data.

By applying example 2 of the present invention to a liquid chromatography mass spectrometer in this manner, it is possible to realize a mass spectrometer and a mass spectrometry method that are inexpensive and can obtain quantitative results with high accuracy without using special equipment, as in example 1.

Further, according to embodiment 2, when the signal is unstable, the above-described parameter adjustment is automatically performed, and the optimum measurement condition can be automatically set.

In addition, the change of the measurement condition in step S7 may be configured such that a voltage value to be adjusted (changed), or the like is determined in advance by an average value, a standard deviation, or the like of the measured signal in an experiment and is performed according to the voltage value.

The above example is an example of a case where the present invention is applied to a liquid chromatography mass spectrometer, but the present invention is applicable not only to a liquid chromatography mass spectrometer but also to a mass spectrometer and a mass analysis method combined with a chromatography apparatus such as a gas chromatography mass spectrometer.

In particular, the present invention is also applicable to a chromatography mass spectrometer that performs measurements such as Selective Ion Monitoring (SIM) measurement and Multiple Reaction Monitoring (MRM) measurement.

Description of the reference symbols

1 … chromatographic peak, 2 … nth cycle, 3 … N +1 th cycle, 4 … channel, 5 … cell, 6 … ion source, 7 … mass separation unit, 8 … mass separation unit, 9 … detector, 10 … controller, 11 … liquid chromatography device, 100 … liquid chromatography mass analysis device, 101 … cell measurement command unit, 102 … data storage unit, 103 … cell signal quantity accumulation unit, 104 … signal deviation calculation unit, 105 … signal deviation evaluation unit, 106 … operation control unit.