WO2017179147A1

WO2017179147A1 - Isomer analysis method using mass spectrometry, and tandem mass spectrometer

Info

Publication number: WO2017179147A1
Application number: PCT/JP2016/061876
Authority: WO
Inventors: 雄紀坂本
Original assignee: 株式会社島津製作所
Priority date: 2016-04-13
Filing date: 2016-04-13
Publication date: 2017-10-19

Abstract

In the present invention, measurement conditions such as the precursor ion m/z, collision energy (CE) range, and the CE step width, are determined according to the compound for isomer identification (S1). Mass spectrums are obtained through product ion scan measurement of the target sample while the CE is changed in accordance with the conditions (S2). A prescribed value, such as the peak intensity ratio at a specific m/z, is determined from the obtained mass spectrums, and an isomer is identified through the comparison of the variation of the prescribed value in relation to the CE variation with a prescribed reference (S3-S5). For example, of the three positional isomers of cresol, the size relationship between the peak intensities when m/z = 77 and m/z = 79 reverses within a lower CE value range for the p- isomer than for the m- and o- isomers. Further, the increase in the intensity of the peak when m/z = 89 in relation to a base peak in the range of CE = 28-29 V is more pronounced for the o- isomer than for the p- and m- isomers. Thus, multiple conditions such as these are comprehensively assessed to identify the positional isomer of the target sample.

Description

Isomer analysis method using mass spectrometry and tandem mass spectrometer

The present invention relates to an isomer analysis method for analyzing an isomer of a predetermined compound using a tandem mass spectrometer and a tandem mass spectrometer for carrying out the method, and more particularly, a main chain and a ring structure The present invention relates to an analysis method and a tandem mass spectrometer for identifying regioisomers that differ only in the bonding position of a substance bonded to the.

Many compounds such as pharmaceuticals, agricultural chemicals, and drugs have different pharmacological actions and effects depending on isomers having the same composition but different structures. Therefore, it is very important to identify isomers of such compounds in the development of pharmaceuticals and agricultural chemicals, production, and quality control. In addition, some compounds are regulated only in specific isomers by the Drug Control Law, and it is important to accurately identify isomers in fields such as illegal drug testing.

The isomers are roughly classified into structural isomers and stereoisomers. Structural isomers often have very different chemical properties. Among the structural isomers, for example, isomers with different main chains and isomers with different functional groups, such as chain compounds, mass spectra and gas chromatograph tandems obtained by scanning measurement with a gas chromatograph mass spectrometer (GC-MS) In many cases, identification is possible by using a mass spectrum obtained by product ion scan measurement in a scanning mass spectrometer (GC-MS / MS).

Specifically, the structural isomers are identified as follows, for example (see Patent Document 1).
Various components in the sample to be measured are separated by a gas chromatograph and introduced into a triple quadrupole mass spectrometer in which a quadrupole mass filter is arranged before and after the collision cell. In a triple quadrupole mass spectrometer, product ion scan measurement is repeated. In other words, among the ions derived from the sample generated in the ionization section, ions having a specific mass-to-charge ratio are selected by the quadrupole mass filter in the previous stage, and the selected ions are dissociated in the collision cell. Produces product ions. The product ions are separated for each mass-to-charge ratio by a quadrupole mass filter at the subsequent stage and detected by an ion detector. Based on the detection signal, the data processing unit creates a mass spectrum in which the relative intensity with respect to the peak (base peak) in the mass-to-charge ratio at which the maximum signal intensity is obtained is the intensity of the peak in each mass-to-charge ratio.

In the data processing unit, the similarity SI between the measured mass spectrum obtained in this way and the mass spectrum stored in a library in which standard mass spectra for various compounds are stored in a database is expressed by, for example, the following equation (1): Calculate according to the formula shown in
SI = {1− [Σ | Iu (m / z) −It (m / z) |] / [Σ | Iu (m / z) + It (m / z) |]} (1)
Here, Iu (m / z) is the relative intensity of the peak at the mass-to-charge ratio m / z on the mass spectrum for an unknown sample, and It (m / z) is on the mass spectrum of a specific compound registered in the library. The relative intensity of the peak at the mass to charge ratio m / z. Further, Σ in the equation (1) is the sum of all m / z.
In general, it is determined whether the unknown sample is a specific compound based on the similarity SI, and the unknown sample is identified (qualitative). Among the isomers having different main chains and functional groups as described above, since there is often a certain difference in the similarity SI between the isomers, it is relatively easy to identify the isomers.

However, in the case of so-called positional isomers that differ only in the substitution positions, such as disubstituted and trisubstituted aromatic compounds, it is difficult to make a significant difference in the peak pattern of the mass spectrum between the isomers. In the above equation (1), a slight difference in relative intensity on the mass spectrum does not significantly affect the similarity SI. Have difficulty. Therefore, conventionally, regioisomers are often identified by the difference in retention time by chromatography. For this purpose, it is necessary to accurately grasp the retention time of each positional isomer by measuring a standard sample under the same analysis conditions as the target sample to be measured.

However, in the case of intermediates and illegal drugs in the pharmaceutical manufacturing process, there are many cases where standard samples are not sold. Therefore, in such compounds, it is usually difficult to distinguish positional isomers from retention time information by chromatography. In addition to chromatography, an effective means for recognizing positional isomers is a nuclear magnetic resonance apparatus (NMR), which is quite expensive and requires special skills and experience to properly analyze NMR spectra. is necessary. In addition, since it is necessary to isolate and purify the target compound in order to perform the measurement by NMR, there are restrictions on the samples that can be analyzed.

International Publication No. 2015/033397

The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to make it possible to easily identify regioisomers that have been difficult to identify using mass spectrometry. It is therefore an object of the present invention to provide an isomer analysis method capable of easily identifying isomers at low cost without preparing a standard sample, and a tandem mass spectrometer for the same.

An isomer analysis method according to the present invention made to solve the above problems is a tandem mass spectrometer capable of dissociating ions derived from a compound and performing mass analysis of product ions generated thereby. An analysis method for identifying positional isomers of a given compound, comprising:
a) Product ion scan measurement in which one of the ion dissociation conditions is changed by a predetermined range within a range of values according to the target compound, and the mass-to-charge ratio according to the target compound is used as the mass-to-charge ratio of the precursor ion. A measurement execution step of acquiring a mass spectrum by executing
b) Regarding the mass spectrum for different ion dissociation condition values obtained in the measurement execution step, the intensity ratio or intensity magnitude relationship of specific peaks according to the target compound with respect to the change of the ion dissociation condition value A processing step of determining which of the plurality of positional isomers of the target compound is based on at least any change;
It is characterized by having.

A tandem mass spectrometer according to the present invention, which has been made to solve the above problems, is a mass spectrometer for carrying out the isomer analysis method according to the present invention, and ionizes a compound in a sample. An ionization unit, a pre-stage mass separation unit that separates ions generated by the ionization unit according to a mass-to-charge ratio, and ions having a specific mass-to-charge ratio selected by the pre-stage mass separation unit with a predetermined collision energy A collision cell to be dissociated below, a rear-stage mass separation unit that separates various product ions generated in the collision cell according to a mass-to-charge ratio, and an ion detection unit that detects product ions separated by the rear-stage mass separation unit A tandem mass spectrometer comprising:
a) While changing one of the ion dissociation conditions in the collision cell within a range of a value corresponding to the target compound with a predetermined width, the mass-to-charge ratio corresponding to the target compound was set as the mass-to-charge ratio of the precursor ion. An analysis control unit for controlling the operation of each unit so as to obtain a mass spectrum by performing a product ion scan measurement;
b) For mass spectra for different ion dissociation condition values obtained under the control of the analysis control unit, the intensity ratio of specific peaks according to the target compound with respect to changes in the ion dissociation condition values Or a data processing unit that determines which of the plurality of positional isomers of the target compound is based on a change in at least one of the magnitude relationships of the strengths;
It is characterized by having.

The tandem mass spectrometer used in the isomer analysis method according to the present invention or the tandem mass spectrometer according to the present invention is typically a quadrupole mass filter in both the former mass separator and the latter mass separator. A triple quadrupole mass spectrometer, or a front mass separator is a quadrupole mass filter, and a rear quadrupole separator is a Q-TOF mass spectrometer which is a time-of-flight mass spectrometer.

In such a tandem mass spectrometer, when the collision energy applied to the ions is changed in order to dissociate the ions in the collision cell, or the gas pressure of the collision gas (generally argon) in the collision cell is changed. It is known that the mode of ion dissociation is different. Therefore, “one of the ion dissociation conditions in the collision cell” can be either collision energy or collision gas pressure. However, in order to change the gas pressure in the collision cell, it is necessary to change the gas supply amount and gas supply pressure to the collision cell. However, even if this is changed, the collision gas pressure in the collision cell immediately becomes a desired value. I'm not settled down. On the other hand, in order to change the collision energy, the voltage applied to the inlet electrode of the collision cell or the like may be changed, and the collision energy is immediately switched by the change. Therefore, in order to collect necessary data in a short time, it is better to perform product ion scan measurement while changing the collision energy.

For example, in cresols, which are known for three types of positional isomers, the fragment patterns differ slightly depending on the isomer, so the magnitude of the peak intensity at multiple specific mass-to-charge ratios is reversed or the relative intensity ratio is noticeable. The value of the collision energy that changes varies depending on the isomer. However, since the collision energy value at which such a change occurs is affected by fluctuations in the collision gas pressure, etc., a plurality of specific mass-to-charge ratios as described above are obtained from a mass spectrum under a specific collision energy value. It is difficult to grasp the magnitude relationship of peak intensities and the difference in relative intensity ratio.

In contrast, in the isomer analysis method and tandem mass spectrometer according to the present invention, product ion scan measurement is performed while changing the collision energy within a predetermined range within a predetermined collision energy range corresponding to the target compound, for example, cresol. Since a plurality of mass spectra obtained by performing the above are utilized, even if the collision energy value at which the magnitude relationship of the peak intensity and the relative intensity ratio change at a plurality of specific mass-to-charge ratios change to some extent, It is possible to reliably determine the collision energy value at which the change occurs. And it becomes possible to determine an isomer based on the collision energy value. Of course, in order to distinguish three or more kinds of isomers in cresol, it is necessary to use a collision energy value corresponding to at least two or more different changes for determination. Even when two types of isomers are identified, it is desirable to use a collision energy value corresponding to two or more different changes for determination in order to increase the reliability of the determination.

In the tandem mass spectrometer according to the present invention, it is preferable that the analysis control unit includes a condition determining unit that determines a range of collision energy to be changed and a change width thereof according to a target compound. For each compound in which positional isomers exist, it is possible to experimentally determine the range of collision energy and the range of change appropriate for identifying the positional isomers. By storing the information in the storage unit, the condition determination unit can easily obtain an appropriate collision energy range corresponding to the target compound and its change range from the storage unit.

Further, in the tandem mass spectrometer according to the present invention, the data processing unit is a collision in which a change that matches a criterion set in advance according to a target compound is generated based on a plurality of mass spectra for different collision energy values. It can be set as the structure which extracts an energy value and determines a positional isomer using the extracted energy value.
Here, the “predetermined criterion” is, for example, a change in the magnitude relationship of peak intensities at a plurality of specific mass-to-charge ratios described above. Such a determination criterion may be stored in the storage unit together with a collision energy range suitable for identifying the above-described positional isomers and a change width thereof.

According to this configuration, even when the collision energy value that causes the change characterizing the positional isomer fluctuates to some extent, the change can be automatically found and the isomer can be accurately determined.

In addition, in order to obtain a mass spectrum that can identify positional isomers by the isomer analysis method according to the present invention, a fragment is generated during ionization, and one of the fragment ions generated thereby is collision cell. It is desirable to perform product ion scan measurement after dissociation in the inside. Therefore, in the tandem mass spectrometer according to the present invention, the ionization unit preferably performs ionization by an electron ionization method.

According to the isomer analysis method and the tandem mass spectrometer according to the present invention, it is possible to identify positional isomers that are difficult to identify from a peak pattern of a certain mass spectrum. This identification eliminates the need for the user to prepare a standard sample in advance because the standard sample does not need to be analyzed in advance, which saves the labor of the standard sample and enables isomer analysis of compounds that are generally difficult to obtain. It becomes. In addition, since analysis for a sample is not different from ordinary mass spectrometry, isomers can be easily identified at low cost.

1 is a schematic configuration diagram of an embodiment of a GC-MS / MS system for carrying out an isomer identification method according to the present invention. The conceptual diagram which shows an example of the setting range of the collision energy at the time of measuring in the GC-MS / MS system of a present Example. The flowchart which shows the procedure of the isomer identification process in the GC-MS / MS system of a present Example. Explanatory drawing of the isomer identification processing method in the GC-MS / MS system of a present Example. The figure which shows the actual measurement example of the product ion spectrum which can identify p-cresol. The figure which shows the actual measurement example of the product ion spectrum which can identify o-cresol. The figure which shows the actual measurement example of the product ion spectrum which can identify m-cresol. The figure which shows the product ion spectrum of each isomer of cresol measured by the several collision energy.

First, the principle of isomer identification in the isomer identification method according to the present invention will be described. Here, a triple quadrupole mass spectrometer, which will be described later, is used as a tandem mass spectrometer for measuring a sample. However, if a similar mass spectrum can be obtained, a Q-TOF mass spectrometer or the like can be used. Obviously, it may be used.

In triple quadrupole mass spectrometers, when the collision energy (CE) applied to the ions is changed when the ions are dissociated in the collision cell, the dissociation mode is different. A change occurs in the pattern of the obtained mass spectrum. In general, collision induced dissociation (CID) used for ion dissociation in a triple quadrupole mass spectrometer is called low energy CID, and the collision energy is in the range of several eV to several tens eV. The unit of collision energy is eV. Usually, the collision energy is determined by the acceleration voltage when ions are incident on the collision cell. Therefore, the collision energy is conventionally expressed by this acceleration voltage. . Therefore, in the following description, the collision energy is expressed by the value of the acceleration voltage.

FIG. 8 shows the collision energy of a precursor ion having a mass-to-charge ratio of 108 for isomers of ortho (o), meta (m), and para (p) positions of cresol, which is a typical example of aromatic disubstituted compounds. This is an example of a mass spectrum obtained by performing product ion scan measurement by changing the measurement (hereinafter, the mass spectrum refers to a product ion spectrum). Here, the collision energy is set in three stages of 10V, 15V, and 20V. Comparing the patterns of the three mass spectra for each collision energy shows little difference in the observed mass-to-charge ratio of the ions and the relative intensity ratio of the peaks of the ions, from which the three isomers are identified. It is difficult.

FIGS. 5 to 7 are actual mass spectra of three isomers of cresol, which were collected by performing product ion scan measurement while changing the collision energy (CE) with a finer step width.

FIG. 5 is a mass spectrum in the range of CE: 21V to 27V. When the relative intensity is compared between the peak at m / z = 77 and the peak at m / z = 79 when CE = 22V, the signal intensity is higher at the peak at m / z = 79 for o-cresol and m-cresol. On the other hand, with p-cresol, m / z = 77 has a higher signal strength. Looking at the collision energy before and after the CE value, when CE = 23V, the signal intensity is higher at the peak of m / z = 77 for all isomers. On the other hand, when CE = 21 V, the signal intensity is higher at the peak of m / z = 79 for all isomers.

For example, the ratio I (77) / I (79) between the peak intensity I (77) at m / z = 77 and the peak intensity I (79) at m / z = 79 and the CE energy: collision energy around 22V The relationship is shown in a graph as shown in FIG. That is, when the collision energy is gradually increased from about 20 V, the magnitude relationship between the relative intensities of the m / z = 77 peak and the m / z = 79 peak is reversed in the middle of the three types of isomers ( In other words, the intensity ratio exceeds 1), but it can be seen that p-cresol has the fastest reversal compared to o-cresol and m-cresol, that is, the lowest collision energy.

Further, when searching for a base peak having the maximum intensity when CE = 26 V, the base peak of o-cresol and m-cresol is a peak of m / z = 77, whereas the base peak of p-cresol is The peak is m / z = 107. Looking at the collision energy before and after this CE value, when CE = 25 V, the peak of m / z = 107 is the base peak for all isomers. On the other hand, when CE = 27V, the peak at m / z = 77 is the base peak for all isomers. That is, when the collision energy is increased from 25 V to 27 V, the mass-to-charge ratio of the base peak is changed from m / z = 107 to m / z = 79 in the middle of the three isomers. It can be seen that the turnover is the slowest compared to o-cresol and m-cresol, that is, occurs at the highest collision energy. This relationship can also be expressed by a graph similar to FIG.

The p-cresol specificity as described above is difficult to grasp by looking at the mass spectrum at a certain collision energy as in the example shown in FIG. 8, but the value of the collision energy with a fine step width. It is possible to grasp by extracting the above-mentioned feature points from the mass spectrum collected while changing and capturing the change. Specifically, by obtaining a collision energy value with an intensity ratio exceeding 1 from the graph as shown in FIG. The mode of ion dissociation is also affected by factors other than collision energy, such as the collision gas pressure in the collision cell and the type of gas. For this reason, there is a possibility that the collision energy value that causes a specific change in the positional isomer as described above may fluctuate (fluctuate) due to such a variation in conditions or a difference in apparatus. Even in such a case, by acquiring a mass spectrum for each collision energy with a fine step width within a predetermined collision energy range in which such variation is assumed in advance, it is possible to find a change specific to the positional isomer without leaking.

FIG. 6 shows mass spectra of CE: 28V and 29V. Below each mass spectrum, the relative intensity ratio of the peak at m / z = 89 to the base peak at m / z = 77 is shown. When CE: 28V to 29V, m-cresol and p-cresol have a relative intensity ratio of only a few dozen%, whereas in o-cresol, the relative intensity ratio is about 30%, which is about twice as large. Yes. Although not shown here, no significant difference is seen in the relative intensity ratio with the collision energy far from the CE value. Therefore, the mass spectrum is collected while changing the collision energy with a fine step width in a predetermined collision energy range including CE: 28V to 29V, the relative intensity ratio is calculated, and the change is observed to detect o-cresol. It can be distinguished from the other two isomers.

FIG. 7 shows mass spectra of CE: 41V and 42V. When the relative intensity is compared between the peak at m / z = 39 and the peak at m / z = 51 when CE = 41V and 42V, the signal intensity is higher at the peak at m / z = 51 for o-cresol and p-cresol. On the other hand, in m-cresol, the signal intensity is larger at m / z = 39. Although not shown here, at the collision energy far from the CE value, the signal intensity is larger at the peak of m / z = 51 for any isomer. Therefore, the mass spectrum is sampled while changing the collision energy with a fine step width within a predetermined collision energy range including CE: 41V to 42V, and whether there is a change in the magnitude relationship of the signal intensity at the peak of m / z = 39, 51 Can be distinguished from the other two isomers.

In the case of cresol, three kinds of positional isomers can be identified by combining features that can be grasped on the mass spectrum in the above-described three mutually separated collision energy ranges.
In this way, even for positional isomers that are difficult to identify simply by observing the mass spectrum at a single collision energy, each mass spectrum is collected under multiple collision energies with a narrow width, and the mass-to-charge ratio of the base peak is switched. The position isomers can be identified by examining the relative intensity ratio of peaks and the change in the magnitude relationship at a specific mass-to-charge ratio.
In addition, these mass spectra are unlikely to differ in the conventional similarity calculation, but by determining in advance an index for comparing signal intensities at a plurality of specific mass-to-charge ratios, differences specific to positional isomers can be obtained. It is possible to judge. Although the above example is cresol, it can be presumed that the same aromatic di-substituted product such as xylene can be identified by the same method.

Hereinafter, an embodiment of a GC-MS / MS system that executes isomer identification processing based on the above-described principle will be described. FIG. 1 is a schematic configuration diagram of the GC-MS / MS system of the present embodiment, FIG. 2 is a conceptual diagram showing an example of a collision energy setting range, and FIG. 3 is an isomer identification process in the GC-MS / MS of the present embodiment. FIG. 4 is an explanatory diagram of an isomer identification processing method in GC-MS / MS of this example.

The GC-MS / MS system of this embodiment includes a GC unit 1 and an MS / MS unit 2. The GC unit 1 includes a sample vaporizing chamber 10 that vaporizes a small amount of sample, a column 12 that separates compounds in the sample in a time direction, and a column oven 11 that controls the temperature of the column 12. The MS / MS unit 2 includes an ionization unit 21 that ionizes a compound by an electron ionization (EI) method in a chamber 20 that is evacuated by a vacuum pump (not shown), and a front quadrupole that includes four rod electrodes. A mass filter 22 and a subsequent quadrupole mass filter 25; a collision cell 23 in which a multipole ion guide 24 is disposed; and a detector 26 that detects ions and outputs a detection signal corresponding to the amount of ions. .

The control unit 4 to which the input unit 6 and the display unit 7 that are user interfaces are connected operates the power supply unit 5 that applies a predetermined voltage to each unit of the GC unit 1 and each unit of the MS / MS unit 2. Each has a function to control. The control unit 4 includes an isomer identification time control unit 40 and a compound correspondence MS / MS condition storage unit 41 as characteristic blocks in the system of this embodiment. The data processing unit 3 includes a spectrum data collection unit 30 that collects and stores data obtained by measurement, a compound database (DB) 32, and a compound DB 32 as characteristic blocks of the system of the present embodiment. A compound identification unit 31 that identifies a target compound by using, an isomer identification information storage unit 34 that stores information for identifying an isomer of a predetermined compound, and an isomer identification information storage unit 34. And an isomer identification unit 33 for identifying an isomer by using the existing information. In the compound DB 32, mass spectra obtained by product ion scan measurement using a plurality of characteristic ion species as precursor ions are recorded in advance for various compounds.

Note that at least a part of the control unit 4 and the data processing unit 3 may be embodied by executing a dedicated control / processing software installed in the computer using a personal computer as hardware. it can. In this case, the input unit 6 is a keyboard or a pointing device (such as a mouse), and the display unit 7 is a display monitor.

The operation of the product ion scan measurement which is one of the MS / MS analyzes in the GC-MS / MS system of the present embodiment will be schematically described.
When a small amount of sample liquid is dropped into the sample vaporizing chamber 10, the sample liquid is vaporized in a short time, and the compound in the sample is sent into the column 12 on a carrier gas such as helium. While passing through the column 12, each compound in the sample reaches the outlet of the column 12 with a different delay. The column oven 11 is heated according to a predetermined temperature profile. The ionization unit 21 sequentially ionizes compounds in the gas supplied from the column 12 outlet. Since the ionization unit 21 is an EI ion source, a part of the compound bond is cleaved during ionization (that is, fragmentation occurs), and ions of various fragments derived from one compound are generated.

Under the control of the control unit 4, the power supply unit 5 applies a voltage that allows ions having a specific mass-to-charge ratio to pass through the rod electrodes of the front-stage quadrupole mass filter 22 and the rear-stage quadrupole mass filter 25. Apply. Thereby, ions having a specific mass-to-charge ratio among various ions derived from the compound pass through the front quadrupole mass filter 22 and are introduced into the collision cell 23. A collision gas is introduced into the collision cell 23, and the ions introduced into the collision cell 23 come into contact with the collision gas and are cleaved by collision-induced dissociation.

Various product ions generated by this cleavage are introduced into the rear quadrupole mass filter 25 while being converged by the multipole ion guide 24, and product ions having a specific mass-to-charge ratio pass through the rear quadrupole mass filter 25. The detector 26 is reached. A detection signal from the detector 26 is input to the data processing unit 3, and the data processing unit 3 creates a mass spectrum, a mass chromatogram, and the like, and performs a compound identification process as described later.

Next, characteristic compound identification processing and isomer identification processing performed in the GC-MS / MS system of this example will be described. As shown in the cresol example, in order to identify a plurality of types of isomers, it is necessary to perform a product ion scan measurement while changing the collision energy with a fine step width in a plurality of different collision energy ranges. In addition to the collision energy range and step width, the analysis conditions such as the mass-to-charge ratio of the target precursor ion and the retention time range in which the corresponding compound is introduced into the MS / MS unit 2 are associated with the compound, and the MS / MS corresponding to the compound When the measurement target compound is stored in advance in the condition storage unit 41 and specified by the user from the input unit 6, the analysis conditions corresponding to the compound are read from the compound correspondence MS / MS condition storage unit 41, It is set in the isomer identification control unit 40.
The analysis conditions as described above can be checked by the user through experiments and registered in the storage unit 41. In general, however, the manufacturer who provides the system checks through experiments and the like when providing the system. Alternatively, it can be registered in the storage unit 41 at an appropriate time after the system is provided.

On the other hand, in the isomer identification information storage unit 34, information necessary for identifying the isomer when the mass spectrum of the product ion scan measurement is acquired while the collision energy is changed with a fine step width as described above. (Hereinafter referred to as “isomer identification information”) is stored in association with the compound. The isomer identification information includes index value calculation information for calculating an index value used for identifying the isomer, and determination conditions such as a threshold value and a range for determining the index value.

For example, as described above, in order to distinguish between p-cresol and the other two cresols, the intensity ratio between the peak at m / z = 77 and the peak at m / z = 79 is less than 1. It is sufficient to determine the collision energy value when the state exceeds 1. However, the determination of the collision energy value is index value calculation information, and the collision energy range in which it can be determined that the measurement target cresol is p-cresol is determined. Condition. The determination condition may be determined with an appropriate margin in consideration of, for example, a change in collision gas pressure within a range in which isomers can be identified.

When it is desired to identify an isomer of a certain compound, when the user designates the compound from the input unit 6, the analysis conditions corresponding to the compound are read from the compound correspondence MS / MS condition storage unit 41 and the isomer is read out. On the other hand, the isomer identification information corresponding to the compound is read from the isomer identification information storage unit 34 and set in the isomer identification unit 33 (step S1). When the analysis is started, the isomer identification control unit 40 changes the collision energy within the holding time range set as the analysis condition by the step width ΔCE set in order from the lower limit CEmin of the collision energy range. While reaching the upper limit CEmax (see FIG. 2), the product ion scan measurement is performed for each collision energy. The spectrum data collection unit 30 acquires and stores mass spectrum data over a predetermined mass-to-charge ratio range for each product ion scan measurement (step S2). Thereby, a large number of mass spectrum data are obtained.

When the analysis is completed, the compound identification unit 31 identifies the compound by collating the peak pattern of one or a plurality of mass spectra obtained with the peak pattern of the mass spectrum in the compound database 32 (step S3). This makes it possible to confirm whether the measured compound is indeed the measurement target compound. However, since the isomer cannot be determined here, for example, it is not clear which isomer is the compound to be measured, but it can only be confirmed as cresol.

Thereafter, the isomer identification unit 33 calculates an index value for identifying the isomer based on the index value calculation information from the mass spectra respectively obtained corresponding to different collision energies (step S4). Then, the isomer is determined by comparing the obtained index value with the determination condition (step S5), and the isomer identification result is output from the display unit 7 (step S6).

In the case of the above cresol, the collision energy value when the intensity ratio of the peak of m / z = 77 and the peak of m / z = 79 is changed from less than 1 to more than 1 in step S4. Is calculated. Then, in step S5, if the collision energy value obtained as the index value is within a predetermined range, it is determined as p-cresol. As described above, p-cresol can also be determined based on the intensity ratio between the peak at m / z = 107 and the peak at m / z = 79 in the vicinity of CE: 25 to 27 V. In order to increase, p-cresol may be determined when both of the two conditions are satisfied. In addition, as described above, o-cresol and m-cresol can be determined according to different index values and determination conditions. Based on the determination results, it is determined which isomer is finally attributed. It may be. Of course, it may be judged that it is not assigned to any isomer.

As described above, according to the GC-MS / MS system of the present embodiment, it is possible to identify regioisomers that were conventionally difficult to identify. As is clear from the above description, in order to identify the isomer as described above, a characteristic measurement in which the product ion scan measurement is sequentially performed while changing the collision energy, and a characteristic measurement based on the measurement result are received. Data processing may be performed, and this can be dealt with by changing software (programs) installed in the computers constituting the control unit 4 and the data processing unit 3.

In the above examples, the GC-MS / MS system was used on the assumption that the sample contains various compounds other than the measurement target compound for which isomers are to be identified. If there is, it is not necessary to separate the components in the GC unit 1, and the vaporized sample may be directly introduced into the MS / MS unit 2.

Further, the above-described embodiment is merely an example of the present invention, and it will be understood that the present invention is encompassed in the scope of the claims of the present application even if it is appropriately changed, modified, or added within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... GC part 10 ... Sample vaporization chamber 11 ... Column oven 12 ... Column 2 ... MS / MS part 20 ... Chamber 21 ... Ionization part 22 ... Pre-stage quadrupole mass filter 23 ... Collision cell 24 ... Multipole ion guide 25 ... Subsequent quadrupole mass filter 26 ... detector 3 ... data processing unit 30 ... spectral data storage unit 31 ... compound identification unit 32 ... compound database (DB)
33 ... Isomer identification unit 34 ... Isomer identification information storage unit 4 ... Control unit 40 ... Isomer identification control unit 41 ... Compound-compatible MS / MS condition storage unit 5 ... Power supply unit 6 ... Input unit 7 ... Display unit

Claims

An analysis method for identifying positional isomers of a predetermined compound using a tandem mass spectrometer capable of dissociating ions derived from a compound and performing mass analysis of product ions generated thereby,
a) Product ion scan measurement in which one of the ion dissociation conditions is changed by a predetermined range within a range of values according to the target compound, and the mass-to-charge ratio according to the target compound is used as the mass-to-charge ratio of the precursor ion. A measurement execution step of acquiring a mass spectrum by executing
b) Regarding the mass spectrum for different ion dissociation condition values obtained in the measurement execution step, the intensity ratio or the magnitude relationship of the intensity of specific peaks according to the target compound with respect to the change of the ion dissociation condition value A processing step of determining which of a plurality of positional isomers of the target compound is based on at least any change in
An isomer analysis method using mass spectrometry, comprising:
An isomer analysis method using mass spectrometry according to claim 1,
One of the ion dissociation conditions is a collision energy when dissociating ions, and the isomer analysis method using mass spectrometry.
An ionization unit that ionizes a compound in a sample, a pre-stage mass separation unit that separates ions generated in the ionization part according to a mass-to-charge ratio, and a specific mass-to-charge ratio selected by the pre-stage mass separation unit A collision cell that dissociates ions under a predetermined collision energy, a rear-stage mass separation unit that separates various product ions generated in the collision cell according to a mass-to-charge ratio, and a product separated by the rear-stage mass separation unit In a tandem mass spectrometer having an ion detector that detects ions,
a) While changing one of the ion dissociation conditions in the collision cell within a range of a value corresponding to the target compound with a predetermined width, the mass-to-charge ratio corresponding to the target compound was set as the mass-to-charge ratio of the precursor ion. An analysis control unit for controlling the operation of each unit so as to obtain a mass spectrum by performing a product ion scan measurement;
b) For mass spectra for different ion dissociation condition values obtained under the control of the analysis control unit, the intensity ratio of specific peaks according to the target compound with respect to changes in the ion dissociation condition values Or a data processing unit that determines which of the plurality of positional isomers of the target compound is based on a change in at least one of the magnitude relationships of the strengths;
A tandem mass spectrometer comprising:
The tandem mass spectrometer according to claim 3,
One of the ion dissociation conditions is a collision energy for dissociating ions, and a tandem mass spectrometer.
The tandem mass spectrometer according to claim 4,
The analysis control unit includes a condition determination unit that determines a range of collision energy to be changed and a change width thereof according to a target compound.
The tandem mass spectrometer according to claim 4,
The data processing unit extracts, based on a plurality of mass spectra for different collision energy values, a collision energy value that causes a change that matches a determination criterion set in advance according to the target compound, and the extracted energy value A tandem mass spectrometer characterized by determining a positional isomer using
A tandem mass spectrometer according to any one of claims 3 to 6,
The tandem mass spectrometer is characterized in that the ionization unit performs ionization by an electron ionization method.