Mass analysis method and mass analysis program

Abstract

To provide a mass analysis method capable of correctly determining molecular mass of a sample molecule.SOLUTION: A method comprises: a mass spectrum acquiring step S1 in which, a reaction gas ion is generated by ionization of a molecule of a prescribed reaction gas, and a sample molecule and the reaction gas ion contact for adding an additional ion to the sample molecule for generating an ion added molecule, then a mass spectrum of the ion added molecule is acquired; an ion added molecule m / z value acquiring step S3 of acquiring a value of m / z for each peak out of a plurality of peaks which appears on the mass spectrum; an added ion m / z value acquiring step S5 of acquiring a value of m / z of each added ion out of a plurality of kinds of added ions corresponding to the prescribed reaction gas, from an added ion database for storing the value of m / z of the plurality of kinds of added ions which may be generated for each reaction gas; and a sample molecular mass identifying step S6 of identifying molecular mass of the sample molecule, on the basis of the value of m / z of each added ion out of the plurality of kinds of added ions acquired in the m / z value acquiring step and the value of m / z in each peak.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a mass spectrometry method and a mass spectrometry program, which is a program for causing a computer to execute the method. [Background technology]

[0002] In mass spectrometry, the molecules of a gaseous or vaporized liquid sample (sample molecules) are generally ionized, and then, using electrical and magnetic forces, the ions are separated and detected according to their mass-to-charge ratio (m / z), which is determined by their mass and charge. This yields a mass spectrum showing the relationship between m / z and detection intensity. Various methods are used to ionize the molecules, including electron ionization (EI) and chemical ionization (CI).

[0003] The electron-electron emission (EI) method ionizes sample molecules by colliding them with thermionic electrons emitted from a heated filament. In this method, electrons are knocked out of the sample molecule, generating ions with approximately the same mass as the sample molecule. In many cases, fragmentation occurs, also generating fragment ions with a smaller mass than the sample molecule. Since the type of fragment ions generated depends on the type of sample molecule, the detected fragment ions provide useful information for identifying the type of sample molecule from among several candidate molecules with the same molecular weight. However, the mass spectrum obtained by the EI method contains a mixture of peaks from the sample molecule (which is ionized without fragmentation) and peaks from fragment ions, making it difficult to identify the peak from the sample molecule. In particular, in sample molecules that are prone to fragmentation, most of them may be fragmented by thermionic electron collisions. In such cases, it becomes difficult to determine the molecular weight of the sample molecule from the peak detection results, and consequently, it becomes difficult to identify the type of sample molecule.

[0004] In contrast, the CI method generates reaction gas ions by colliding thermionic electrons with molecules of a reaction gas different from the sample molecule, and then brings these reaction gas ions into contact with the sample molecule to cause an ionic-molecular reaction, thereby generating protons (H) in the sample molecule. + This process generates a protonated molecule with one proton attached (see, for example, Patent Document 1; note that the reaction gas ion is usually a different ion from a proton). The protonated molecule behaves as a monovalent cation as a whole. The mass spectrum obtained by the CI method shows a peak due to the protonated molecule, while the peak due to fragment ions is almost nonexistent because cleavage is difficult to occur in the CI method. Therefore, the m / z value of the protonated molecule can be easily determined, and the molecular weight of the sample molecule can also be easily determined by subtracting 1 from that m / z value.

[0005] Therefore, conventionally, mass spectra have been obtained from the same sample using both the CI method and the EI method, and the type of sample molecule has been identified based on the molecular weight of the sample molecule determined from the mass spectrum obtained by the CI method and the m / z value of the fragment ion determined from the mass spectrum obtained by the EI method (Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-064285 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the mass spectrum obtained by the CI method, ideally, there should be almost no peaks other than those caused by protonated molecules. However, in reality, reaction gas ions directly attach to the sample molecule, generating ionized molecules other than protonated molecules (note that protonated molecules are also a type of ionized molecule), which can result in peaks in the mass spectrum with m / z values ​​larger than those caused by protonated molecules. In such cases, the analyst may mistakenly identify the ionized molecule, caused by the addition of reaction gas ions, as a peak caused by a protonated molecule, potentially leading to an incorrect determination of the sample molecule's molecular weight. If the determined molecular weight of the sample molecule is incorrect, even if the m / z value of the fragment ion is obtained by the EI method, the type of sample molecule cannot be identified, or may be incorrectly identified.

[0008] The problem that this invention aims to solve is to provide a mass spectrometry method and a mass spectrometry program that can accurately determine the molecular weight of a sample molecule. [Means for solving the problem]

[0009] The mass spectrometry method according to the present invention, which was developed to solve the above problems, A mass spectrum acquisition step in which reaction gas ions are generated by the ionization of molecules of a predetermined reaction gas, and the mass spectrum of an ion-added molecule is obtained when the sample molecule is brought into contact with the reaction gas ions, thereby adding an adduct ion to the sample molecule. An ion addition molecule m / z value acquisition step, which acquires the m / z value for each of the multiple peaks that appeared in the mass spectrum, An addition ion m / z value acquisition step is to acquire the m / z value of each of the multiple types of addition ions corresponding to the predetermined reaction gas from an addition ion database in which the m / z values ​​of multiple types of possible addition ions are recorded for each reaction gas, A sample molecular weight identification step is performed to identify the molecular weight of the sample molecule based on the m / z values ​​of each of the multiple peaks and the m / z values ​​of each of the multiple types of adduct ions obtained in the m / z value acquisition step. It holds.

[0010] The mass spectrometry program according to the present invention causes a computer to acquire a mass spectrum of an ion-added molecule generated by generating reaction gas ions by ionizing molecules of a predetermined reaction gas, and adding added ions to the sample molecules by bringing the sample molecules into contact with the reaction gas ions; a mass spectrum acquisition step; an ion-added molecule m / z value acquisition step of acquiring an m / z value for each of a plurality of peaks appearing in the mass spectrum; an added ion m / z value acquisition step of acquiring an m / z value for each of a plurality of types of added ions corresponding to the predetermined reaction gas from an added ion database in which m / z values of a plurality of types of possible added ions are recorded for each reaction gas; a sample molecular weight identification step of identifying the molecular weight of the sample molecule based on the m / z value of each of the plurality of peaks and the m / z value of each of the plurality of types of added ions acquired in the m / z value acquisition step and is a program for executing the steps.

Advantages of the Invention

[0011] In this invention, first, similar to the conventional CI method, an ion-adducted molecule is generated by ionizing a predetermined reaction gas molecule, and then the sample molecule is brought into contact with the reaction gas ions to form an ion-adducted molecule to which an adduct ion (which is not necessarily the same as the reaction gas ion, as described later) is attached, and a mass spectrum is obtained. Then, the m / z value is obtained for each of the multiple peaks that appear in this mass spectrum. Each of the multiple m / z values ​​obtained from the mass spectrum is obtained by adding the molecular weight of the sample molecule to the m / z value of the multiple types of adduct ions that are generated by the contact between the reaction gas ions and the sample molecule. Therefore, if the m / z values ​​of each of the multiple types of adduct ions are known, the molecular weight of the sample molecule can be determined based on the m / z value obtained from the mass spectrum and the m / z value of the adduct ions. Therefore, an adsorption ion database is created in advance, in which the m / z values ​​of multiple types of adsorption ions for each reaction gas are recorded. By obtaining the m / z values ​​of each of the multiple types of adsorption ions corresponding to the reaction gas used in the analysis (the predetermined reaction gas) from this adsorption ion database, the molecular weight of the sample molecule can be determined based on the m / z values ​​of each peak in the mass spectrum and the m / z values ​​of each adsorption ion.

[0012] According to the present invention, it is possible to prevent analysts from mistakenly identifying an ion-adjusted molecule, to which an adsorption ion with a larger m / z value than the peak due to the proton-adjusted molecule is attached, as the peak due to the proton-adjusted molecule, thereby enabling the accurate determination of the molecular weight of the sample molecule. [Brief explanation of the drawing]

[0013] [Figure 1] A schematic diagram showing an example of a mass spectrometer used when carrying out the mass spectrometry method according to the present invention. [Figure 2] A flowchart illustrating the operation of embodiments of the mass spectrometry method and mass spectrometry program according to the present invention. [Figure 3] This figure shows an example of data contained in the addition ion database used in the mass spectrometry method and mass spectrometry program of this embodiment. [Figure 4]A figure showing an example of a CI mass spectrum obtained by the mass spectrometry method of this embodiment. [Figure 5] This figure shows an example of data contained in the fragment ion database used in the mass spectrometry method and mass spectrometry program of this embodiment. [Figure 6] A figure showing an example of an EI mass spectrum obtained by the mass spectrometry method of this embodiment. [Figure 7] A figure showing another example of a CI mass spectrum obtained by the mass spectrometry method of this embodiment. [Modes for carrying out the invention]

[0014] Embodiments of the mass spectrometry method and mass spectrometry program according to the present invention will be explained using Figures 1 to 7.

[0015] (1) An example of a mass spectrometer Before describing the mass spectrometry method and mass spectrometry program of this embodiment, we will first describe a gas chromatograph-mass spectrometer (GC-MS) 1, which is an example of a mass spectrometer. This GC-MS 1 is the device used when carrying out the mass spectrometry method of this embodiment, and part of the operation of this device is performed by the mass spectrometry program of this embodiment.

[0016] Figure 1 shows the schematic configuration of GC-MS1. GC-MS1 comprises a gas chromatograph (GC) unit 10, a mass spectrometry (MS) unit 20, a data processing unit 30, and a database 40.

[0017] The GC unit 10 includes an injector 11, a sample vaporization chamber 12, a capillary column 13, and a column oven 14. The injector 11 drops the liquid sample into the sample vaporization chamber 12. The sample vaporization chamber 12 vaporizes the liquid sample and is connected to the inlet end of the capillary column 13. The capillary column 13 separates the gaseous sample introduced from the sample vaporization chamber 12 into its components over time as it passes through. The capillary column 13 is housed in the column oven 14 and is heated by the column oven 14.

[0018] The MS unit 20 includes an ion source 21, a lens electrode 22, a quadrupole mass filter 23, and an ion detector 24. These are housed within a vacuum chamber 25.

[0019] The ion source 21 is a CI / EI dual-purpose ion source and includes an ionization chamber 211 into which a sample gas containing the sample molecules to be analyzed is introduced, a filament 212 that generates thermionic electrons, a reaction gas flow path 213 with a valve 214 in the middle, and a filament power supply unit 215. When a predetermined current is supplied from the filament power supply unit 215 to the filament 212, the filament 212 is heated and thermionic electrons are generated.

[0020] When ionization is performed by the CI method, current is supplied to the filament 212 with valve 214 open (on). This supplies the reaction gas into the ionization chamber 211 through the reaction gas channel 213, and thermionic electrons collide with the molecules of the reaction gas, generating reaction gas ions. These reaction gas ions react with the sample molecules in the sample gas to produce ion-added molecules in which adducted ions are attached to the sample molecules. On the other hand, when ionization is performed by the EI method, current is supplied to the filament 212 with valve 214 closed (off). Thermionic electrons are accelerated by the electric field formed by the DC voltage applied to electrodes (not shown), the ionization chamber 211, and the filament 212 itself, and enter the ionization chamber 211. These thermionic electrons then collide with the sample molecules introduced into the ionization chamber 211, ionizing the sample molecules, and further ion cleavage occurs, generating fragment ions. In both the CI method and the EI method, the ions (ion-added molecules or fragment ions) generated in the ionization chamber 211 are ejected from the ionization chamber 211 by the action of the electric field formed by the repeller electrode located inside the ionization chamber 211.

[0021] The lens electrode 22 focuses the ions ejected from the ionization chamber 211 through the action of the electric field it forms. The quadrupole mass filter 23 has four rod-shaped electrodes, and a predetermined voltage, which is the sum of a DC voltage and a high-frequency voltage, is applied to each of these rod-shaped electrodes. The quadrupole mass filter 23 selectively passes only the ions focused by the lens electrode 22 that have an m / z corresponding to this voltage. By changing this voltage within a predetermined range, the m / z of the ions passing through the quadrupole mass filter 23 is scanned within a predetermined range. The ion detector 24 outputs a detection signal corresponding to the amount of incident ions.

[0022] The data processing unit 30 includes a mass spectrum acquisition unit 31, an m / z value acquisition unit 32, a sample molecular weight identification unit 33, a sample molecule candidate data acquisition unit 34, and a sample molecule identification unit 35. The data processing unit 30 is comprised of hardware such as a CPU and memory, and the mass spectrometry program (software) of this embodiment. The database 40 is a combination of an addition ion database (addition ion DB) 41 and a fragment ion database (fragment ion DB) 42, and is composed of a storage device such as a hard disk (HD) or solid state drive (SSD), or a storage medium such as a CD or DVD. Details of the data processing unit 30 and the database 40 will be described later along with the description of the mass spectrometry method and mass spectrometry program of this embodiment.

[0023] In addition, the GC-MS1 includes an analysis control unit 50 that controls the operation of the GC unit 10 and the MS unit 20, a display unit 51 that displays analysis results, etc., and an input unit 52 consisting of a keyboard, mouse, etc., for user input. The display unit 51 and the input unit 52 may be integrated by using a touch panel. The data processing unit 30, database 40, analysis control unit 50, display unit 51, and input unit 52 are combined and implemented by a computer such as a PC.

[0024] (2) Operation of the mass spectrometry method and the mass spectrometry program of this embodiment The mass spectrometry method of this embodiment will be explained with reference to the flowchart in Figure 2. In the following description, the operations performed by each part of the data processing unit 30 are controlled by the mass spectrometry program of this embodiment.

[0025] First, the analytical control unit 50 controls the GC / MS measurement using the CI method and acquires a mass spectrum (Step 1: Mass Spectrum Acquisition Step). The GC / MS measurement using the CI method is performed as follows.

[0026] In the GC unit 10, a liquid sample is dropped from the injector 11 into the sample vaporization chamber 12. The liquid sample vaporizes in a short time and becomes a sample gas, which is then fed into the sample vaporization chamber 12 from a carrier gas source (not shown) and carried by the flow of a carrier gas such as He gas into the capillary column 13. The various molecules (sample molecules) contained in the sample gas fed into the capillary column 13 are separated over time as they pass through the capillary column 13 and are sequentially introduced into the ion source 21 of the MS unit 20.

[0027] As described above, in the ion source 21, thermionic electrons generated by the filament 212 collide with molecules of the reaction gas supplied into the ionization chamber 211 (CI method), thereby generating ion-added molecules in which adducting ions are attached to sample molecules. The generated ion-added molecules are ejected from the ionization chamber 211, focused by the lens electrode 22, and incident on the quadrupole mass filter 23. The molecules pass through the quadrupole mass filter 23 and are detected by the ion detector 24 only when the voltage applied to the rod-shaped electrode of the quadrupole mass filter 23 is a predetermined value corresponding to the m / z of the ion. Here, as the voltage applied to the rod-shaped electrode of the quadrupole mass filter 23 changes over time within a predetermined range, the type of ion incident on the ion detector 24 changes according to its m / z value. Therefore, the mass spectrum acquisition unit 31 receives the detection signal sent from the ion detector 24 and acquires a mass spectrum showing the relationship between the m / z of the ion and the detection intensity based on the time change in the intensity of the detection signal.

[0028] In the following, the mass spectrum obtained when ionization is performed by the CI method as in Step 1 will be called the "CI mass spectrum," and the mass spectrum obtained when ionization is performed by the EI method as in Step 7 described later will be called the "EI mass spectrum."

[0029] Next, the m / z value acquisition unit 32 detects a peak from the CI mass spectrum acquired by the mass spectrum acquisition unit 31 (step 2) and acquires the m / z value at that peak (step 3: ion addition molecule m / z value acquisition step). The detection of these peaks and the acquisition of the m / z value can be performed using conventional methods.

[0030] Next, the sample molecular weight identification unit 33 acquires information (reaction gas identification information) to identify the reaction gas used when acquiring the CI mass spectrum (step 4). This information is typically the name of the reaction gas, but it may also be identified by the molecular formula of the molecules the reaction gas contains. The operator may directly input the name of the reaction gas, etc., using the input unit 52, or the operator may select from the candidates for reaction gas identification information displayed on the display unit 51 using the input unit 52.

[0031] Then, the sample molecular weight identification unit 33 obtains the m / z values ​​of each of the multiple types of adductions corresponding to the reaction gas identification information from the adduction ion DB 41 (Step 5: Adduction ion m / z value acquisition step). Figure 3 shows an example of the data recorded in the adduction ion DB 41. In this example, methane (CH4) and isobutane (C4H4) are used as reaction gases. 10 The database includes methane, ammonia (NH3), methanol (CH4O), and acetonitrile (C2H3N), and for each of these reaction gases, it contains three m / z values ​​and ionic formulas for the adduct ions. For example, if the reaction gas is methane, the adduct ion DB41 contains the m / z value of 1 (ionic formula H3). + ), 17 (same CH5 + ) and 29 (same C2H5 + ) is included.

[0032] Taking the case where the reaction gas is methane as an example, the process of generating ion-added molecules will be described. The methane molecule collides with a thermal electron and reacts according to the following equation (1): CH4+e - (thermal electron)→CH4 +* +2e - …(1) By reacting in this way, CH4 +* (radical cation) is generated. This CH4 +* further reacts with a methane molecule according to the following equation (2): CH4 +* +CH4→CH5 + +CH3 * …(2) By reacting in this way, CH5 + and CH3 * (radicals) are generated. When CH5 + among these reacts with the sample molecule M, M+CH5 + →MH + +CH4…(3) results. As a result, an ion-added molecule in which the proton H + as an added ion is added to the sample molecule M is generated. On the other hand, an ion-added molecule in which CH5 + generated in equation (2) is directly added to the sample molecule M as an added ion is also generated.

[0033] Furthermore, from CH4 +* generated in equation (1), the following reaction of equation (4) CH4 +* +CH4→CH3 + +CH5 * …(4) occurs, but CH3 + further reacts with a methane molecule according to the following equation (5): CH3 + +CH4→C2H5 + +H2 and C2H5 + is generated. An ion-added molecule is also generated when this C2H5 + is directly added to the sample molecule M as an added ion.

[0034] Next, the sample molecular weight identification unit 33 identifies the molecular weight of the sample molecule based on the m / z values ​​of each of the multiple peaks that appeared in the CI mass spectrum and the m / z values ​​of each of the multiple types of adduct ions obtained in step 5 (step 6: sample molecular weight identification step).

[0035] Figure 4 shows an example of a CI mass spectrum when methane is used as the reaction gas. The m / z values ​​of the peaks appearing in this CI mass spectrum obtained in Step 3 are 343, 359, and 371. In contrast, the m / z values ​​of the adduct ions obtained in Step 5 when methane is the reaction gas are 1, 17, and 29. When the m / z values ​​of these three peaks appearing in the CI mass spectrum are matched to the m / z values ​​of the adduct ions in ascending order, the difference between the former and latter values ​​is 342 for all three. From this, the molecular weight of the sample molecule can be determined to be 342 (Step 6 above). Furthermore, H is added to the sample molecule as an adduct ion. + CH5 + and C2H5 + It can be seen that an adduct has been added (however, in order to identify the type of sample molecule, it is not necessary to identify the type of adduct ion attached to the sample molecule using the CI method). However, at this point, the type of sample molecule (name, molecular formula, structural formula, etc.) has not yet been identified.

[0036] Next, the analysis control unit 50 controls the GC / MS measurement using the EI method, and the mass spectrum acquisition unit 31 acquires the EI mass spectrum (Step 7: EI mass spectrum acquisition step). In the EI method, the GC unit 10 introduces the sample molecules into the ion source 21 of the MS unit 20 in the same manner as in the CI method. As described above, the sample molecules are ionized by thermionic electrons colliding with them in the ion source 21 (EI method), and fragment ions are generated by further ion cleavage. The generated fragment ions are focused by the lens electrode 22 and incident on the quadrupole mass filter 23, and the mass spectrum is acquired in the same manner as in the CI method.

[0037] Next, the m / z value acquisition unit 32 detects a peak from the EI mass spectrum acquired by the mass spectrum acquisition unit 31 (step 8) and acquires the m / z value at that peak (step 9: fragment ion m / z value acquisition step).

[0038] Next, the sample molecule candidate data acquisition unit 34 acquires molecular identification information and the m / z value of the fragment ion generated from the molecule from the fragment ion DB 42 for multiple molecules having the molecular weight identified in step 6 (step 10: sample molecule candidate data acquisition step). Molecular identification information includes the name of the molecule, molecular formula (composition formula), and structural formula of the molecule.

[0039] Figure 5 shows an example of data stored in the Fragment Ion DB42. The upper part of Figure 5 shows Table 421, which contains the compound name, molecular weight, and molecular formula of numerous compounds, each assigned a unique serial number. Although only eight compounds are shown in the table in Figure 5, data for many more compounds is actually stored, and data for other compounds can be displayed by sliding the scroll bar 422 displayed on the right end of the table. From Figure 5, it can be seen that there are multiple types of molecules with a molecular weight of 342, as shown in the example in Step 6.

[0040] The Fragment Ion DB42 further contains mass spectral data for each compound listed in the table above, measuring the fragment ions generated from the molecule of that compound. The m / z values ​​at the peaks are identified in each mass spectral data. When Table 421 is displayed on the display unit 51, selecting one of the data using the input unit 52 indicates that the data has been selected by highlighting 423 (a different color from the surrounding area) behind the selected data on Table 421. Furthermore, the mass spectral data 424 measuring the fragment ions generated from the molecule of the compound highlighted 423 is displayed in the lower part of Figure 5. In the mass spectral data 424, peaks appear at m / z values ​​of 69, 103, 115, 131, and 229, and these m / z values ​​are also displayed within the mass spectral data 424. The peak at m / z 342 is a peak due to an ion-adduct molecule that reached the ion detector 24 without cleavage. The mass spectrum 424 further displays the serial number, molecular formula, structural formula (with symbol 425), and molecular weight of the compound highlighted 423.

[0041] Next, the sample molecule identification unit 35 extracts the m / z values ​​of the fragment ions generated from each molecule obtained from the fragment ion DB 42 in step 10 that match the m / z values ​​at the peaks of the EI mass spectrum obtained in step 9. For the molecules whose values ​​match, the sample molecule is identified using the molecular identification information obtained in step 10 (step 11: sample molecule identification step).

[0042] For example, as shown in Figure 6, if the EI mass spectrum obtained in step 7 has peaks at m / z values ​​of 69, 103, 115, 131, and 229, then the molecule C is highlighted as 423 in Figure 5. 13 This matches the m / z value of the fragment ions generated from H8F6O4. Based on this result, the sample molecule in this example is C 13 It can be identified as H8F6O4.

[0043] Furthermore, if, due to measurement accuracy issues or other reasons, the m / z values ​​stored in the fragment ion DB42 and the multiple m / z values ​​in the measured EI mass spectrum do not perfectly match for any of the molecules (molecules with molecular weights identified by the CI method) from which data was obtained in step 10, the molecule with the greatest degree of agreement calculated using a known method should be identified as the sample molecule.

[0044] Subsequently, post-processing is performed, such as displaying the information of the identified sample molecules on the display unit 51 or storing it in the data storage unit (not shown). At the same time, the CI mass spectrum and / or EI mass spectrum used for the analysis may also be displayed on the display unit 51. With this, the series of operations of the mass spectrometry method according to this embodiment is completed.

[0045] The present invention is not limited to the embodiments described above, and various modifications are possible.

[0046] For example, in the above embodiment, CI mass spectra and EI mass spectra were obtained using GC-MS1, but instead, a liquid chromatograph-mass spectrometer (LC-MS) may be used, in which the liquid sample passes through the liquid chromatograph column and is then vaporized by the ion source of the mass spectrometer. Alternatively, a mass spectrometer without a chromatograph may be used.

[0047] In the above description of the embodiment, it was explained that by using a chromatograph, only one peak from one type of sample molecule appears in one CI mass spectrum obtained at one retention time. However, the present invention can also be applied when multiple types of sample molecules appear in one CI mass spectrum. In the example shown in Figure 7, when methane, which produces three types of adduct ions, is used as the reaction gas, six peaks appear in the CI mass spectrum, so it is estimated that there are 6 / 3 = 2 types of sample molecules. If we assume that the peak with the smallest m / z value among these six peaks, m / z = 322, is due to an ion-adduct molecule in which a proton is added to the first sample molecule, then the molecular weight of the first sample molecule is M = 321. The m / z values ​​of the ion-adduct molecule in which two types of adduct ions other than a proton are added to the M = 321 sample molecule are m / z = 321 + 17 = 338 and m / z = 321 + 29 = 350, which correspond to the second and fourth peaks from the left in the CI mass spectrum in Figure 7. Furthermore, the remaining peaks in the CI mass spectrum, at m / z = 343, 359, and 371, can be explained as being due to a second sample molecule with a molecular weight M = 342. The same applies when peaks from three or more sample molecules appear in the CI mass spectrum.

[0048] In the above embodiment, the ionic formula of each adduction is recorded in the adduction DB41 along with the m / z value of the adduction; however, recording the ionic formula is not mandatory. Similarly, the m / z value (and ionic formula) of adductions can also be recorded in the adduction DB41 for reaction gases other than the five types listed in Figure 3. Furthermore, although three types of adductions are listed for one type of reaction gas in Figure 3, two types or (if there are four or more types of adductions) four or more types may also be listed.

[0049] In the above embodiment, the CI mass spectrum is obtained first, the molecular weight of the sample molecule is determined, and then the EI mass spectrum is obtained. However, it is also possible to obtain the CI mass spectrum and the EI mass spectrum first, and then determine the molecular weight of the sample molecule based on the CI mass spectrum and identify the sample molecule based on the EI mass spectrum.

[0050] In the above embodiment, the molecular weight of the sample molecule is identified based on the CI mass spectrum using the mass spectrometry method according to the present invention, and then the name of the sample molecule is identified based on this molecular weight and the EI mass spectrum. However, instead, only the identification of the molecular weight of the sample molecule based on the CI mass spectrum may be performed.

[0051] [Pattern] It will be obvious to those skilled in the art that the exemplary embodiments described above are specific examples of the following embodiments.

[0052] (Section 1) A mass spectrometry method according to one aspect of the present invention is: A mass spectrum acquisition step in which reaction gas ions are generated by the ionization of molecules of a predetermined reaction gas, and the mass spectrum of an ion-added molecule is obtained when the sample molecule is brought into contact with the reaction gas ions, thereby adding an adduct ion to the sample molecule. An ion addition molecule m / z value acquisition step, which acquires the m / z value for each of the multiple peaks that appeared in the mass spectrum, An addition ion m / z value acquisition step is to acquire the m / z value of each of the multiple types of addition ions corresponding to the predetermined reaction gas from an addition ion database in which the m / z values ​​of multiple types of possible addition ions are recorded for each reaction gas, A sample molecular weight identification step is performed to identify the molecular weight of the sample molecule based on the m / z values ​​of each of the multiple peaks and the m / z values ​​of each of the multiple types of adduct ions obtained in the m / z value acquisition step. It holds.

[0053] (Section 4) A mass spectrometry program according to another aspect of the present invention is provided for a computer, A mass spectrum acquisition step in which reaction gas ions are generated by the ionization of molecules of a predetermined reaction gas, and the mass spectrum of an ion-added molecule is obtained when the sample molecule is brought into contact with the reaction gas ions, thereby adding an adduct ion to the sample molecule. An ion addition molecule m / z value acquisition step, which acquires the m / z value for each of the multiple peaks that appeared in the mass spectrum, An addition ion m / z value acquisition step is to acquire the m / z value of each of the multiple types of addition ions corresponding to the predetermined reaction gas from an addition ion database in which the m / z values ​​of multiple types of possible addition ions are recorded for each reaction gas, A sample molecular weight identification step is performed to identify the molecular weight of the sample molecule based on the m / z values ​​of each of the multiple peaks and the m / z values ​​of each of the multiple types of adduct ions obtained in the m / z value acquisition step. This is a program that executes [the command / action].

[0054] In the mass spectrometry method described in paragraph 1 and the mass spectrometry program described in paragraph 4, first, similar to the conventional CI method, an ion-adducted molecule is generated by ionizing a predetermined reaction gas molecule, and then the sample molecule is brought into contact with the reaction gas ions to add an adduct ion (which is not necessarily the same as the reaction gas ion, as described later) to the sample molecule, and a mass spectrum is obtained. Then, the m / z value is obtained for each of the multiple peaks that appear in this mass spectrum. Each of the multiple m / z values ​​obtained from the mass spectrum is obtained by adding the molecular weight of the sample molecule to the m / z value of the multiple types of adduct ions that are generated by the contact between the reaction gas ions and the sample molecule. Therefore, if the m / z values ​​of each of the multiple types of adduct ions are known, the molecular weight of the sample molecule can be determined based on the m / z value obtained from the mass spectrum and the m / z value of the adduct ions. Therefore, an adsorption ion database is created in advance, in which the m / z values ​​of multiple types of adsorption ions for each reaction gas are recorded. By obtaining the m / z values ​​of each of the multiple types of adsorption ions corresponding to the reaction gas used in the analysis (the predetermined reaction gas) from this adsorption ion database, the molecular weight of the sample molecule can be determined based on the m / z values ​​of each peak in the mass spectrum and the m / z values ​​of each adsorption ion.

[0055] According to the mass spectrometry method described in paragraph 1 and the mass spectrometry program described in paragraph 4, it is possible to prevent the analyst from mistakenly identifying an ion-adducted molecule with an adduct ion whose m / z value is larger than that of a proton-adducted molecule as a peak due to a proton-adducted molecule, thereby enabling the accurate determination of the molecular weight of the sample molecule.

[0056] As mentioned above, the reaction gas ion and the adduct ion are not necessarily the same. For example, if the reaction gas is methane, the reaction gas ion is CH5 + and C2H5 + A reaction occurs, and the adduct ion is H + (Proton. Different from a reactive gas ion.) CH5 + and C2H5 + Here, the adduct ion H is formed. + M(sample molecule)+CH5 + →[M+H] + It is produced by the reaction with +CH4.

[0057] In the mass spectrometry method described in paragraph 1, the step for obtaining the m / z value of the ion-adducted molecule must be performed after the step for obtaining the mass spectrum (because processing is performed using the mass spectrum), and the step for determining the sample molecular weight must be performed after each of these steps (because the m / z values ​​of the ion-adducted molecule and the adducted ion are used). On the other hand, the order in which the step for obtaining the m / z value of the adducted ion is performed does not matter as long as it is performed before the step for determining the sample molecular weight. The same applies to the mass spectrometry program described in paragraph 4.

[0058] (Paragraph 2) The mass spectrometry method relating to Paragraph 2 is further the mass spectrometry method relating to Paragraph 1, An EI mass spectrum acquisition step is to acquire an EI mass spectrum, which is a mass spectrum obtained by cleaving the sample molecules by an electron ionization method, A fragment ion m / z value acquisition step is to acquire the m / z value of the peak that appeared in the EI mass spectrum, A sample molecule candidate data acquisition step obtains molecular identification information and the m / z value of the fragment ions generated from a fragment ion database, which records information identifying the molecule, the molecular weight of the molecule, and the m / z value of the fragment ions generated from the molecule for each molecule, for multiple molecules having the same molecular weight as the sample molecule identified in the sample molecular weight identification step. For each of the aforementioned plurality of molecules, the sample molecule identification step involves comparing the m / z value of the fragment ion obtained in the sample molecule candidate data acquisition step with the m / z value obtained in the fragment ion m / z value acquisition step, and identifying the sample molecule using the molecular identification information of the molecule whose two m / z values ​​match among the plurality of molecules. It holds.

[0059] (Article 5) The mass spectrometry program relating to Article 5 further includes the following in the mass spectrometry program relating to Article 4: An EI mass spectrum acquisition step is to acquire an EI mass spectrum, which is a mass spectrum obtained by cleaving the sample molecules by an electron ionization method, A fragment ion m / z value acquisition step is to acquire the m / z value of the peak that appeared in the EI mass spectrum, A sample molecule candidate data acquisition step obtains molecular identification information and the m / z value of the fragment ions generated from a fragment ion database, which records information identifying the molecule, the molecular weight of the molecule, and the m / z value of the fragment ions generated from the molecule for each molecule, for multiple molecules having the same molecular weight as the sample molecule identified in the sample molecular weight identification step. For each of the aforementioned plurality of molecules, the sample molecule identification step involves comparing the m / z value of the fragment ion obtained in the sample molecule candidate data acquisition step with the m / z value obtained in the fragment ion m / z value acquisition step, and identifying the sample molecule using the molecular identification information of the molecule whose two m / z values ​​match among the plurality of molecules. This is a program that executes [the command / action].

[0060] Here, molecular identification information includes the name of the molecule, its molecular formula (composition formula), and its structural formula.

[0061] According to the mass spectrometry method described in paragraph 2 and the mass spectrometry program described in paragraph 5, the molecular weight of the sample molecule can be correctly determined, and then the sample molecule can be accurately identified by using molecular identification information for multiple molecules having the same molecular weight, specifically those whose m / z values ​​of fragment ions obtained from a fragment ion database match those values ​​obtained from the EI mass spectrum of the sample molecule using the electron ionization method.

[0062] In the mass spectrometry method described in paragraph 2, the fragment ion m / z value acquisition step must be performed after the EI mass spectrum acquisition step (because processing is performed using the EI mass spectrum), and the sample molecule candidate data acquisition step must be performed after the sample molecular weight identification step (because processing is performed using the molecular weight of the sample). Furthermore, the sample molecule identification step must be performed after each of the other steps (because the m / z values ​​obtained in the sample molecule candidate data acquisition step and the fragment ion m / z value acquisition step are used). On the other hand, the order in which the sample molecule candidate data acquisition step is performed does not matter as long as it is performed before the sample molecule identification step. Moreover, each step using the CI method described in paragraph 1 may be performed first, followed by each step using the EI method described in paragraph 2, or the mass spectrum acquisition step (using the CI method) and the EI mass spectrum acquisition step may be performed first, followed by the remaining steps described in paragraphs 1 and 2 other than these two steps. In the latter case, either the mass spectrum acquisition step (using the CI method) or the EI mass spectrum acquisition step may be performed first. In short, the order in which each step is performed is not limited as long as it does not contradict the order relationships described in each step in paragraphs 1 and 2. The same applies to the mass spectrometry program related to item 5.

[0063] (Clause 3) The mass spectrometry method relating to paragraph 3 is the mass spectrometry method relating to paragraph 1 or paragraph 2, wherein the sample molecules are molecules of the components of the sample that have passed through the column of a gas chromatograph or liquid chromatograph.

[0064] According to the mass spectrometry method described in paragraph 3, since the sample molecules are molecules of the components of the sample that have passed through the column, even if the sample contains molecules of multiple components, the sample molecules are separated from the molecules of other components in the sample by passing through the column, and a mass spectrum is obtained by the CI method for the sample molecules alone, making it easier to determine the molecular weight. [Explanation of Symbols]

[0065] 1. Gas chromatograph-mass spectrometer (GC-MS) 10…Gas Chromatography (GC) Section 11…Injector 12…Sample vaporization chamber 13… Capillary column 14… Column oven 20…Mass spectrometry (MS) department 21…Ion source 211... Ionization Chamber 212… Filament 213… Reaction gas flow path 214… Valve 215... Filament power supply 22...Lens electrode 23... Quadrupole Mass Filter 24... Ion detector 25… Vacuum Chamber 30...Data Processing Unit 31...Mass spectrum acquisition unit 32...m / z value acquisition section 33... Sample Molecular Weight Identification Section 34…Sample Molecular Candidate Data Acquisition Unit 35... Sample Molecular Identification Section 40…Database 41… Addition Ion Database (Addition Ion DB) 42…Fragment Ion Database (Fragment Ion DB) 421... Table 422... Scroll bar 423…Highlight 424... Mass spectrum 425...Structural formula of a compound with highlighting 50…Analysis and Control Section 51...Display section 52...Input section

Claims

1. a mass spectrum acquisition step of acquiring a mass spectrum of an ion adduct molecule generated by ionizing a predetermined reaction gas molecule to generate a reaction gas ion, and adding an adduct ion to the sample molecule by contacting the sample molecule with the reaction gas ion; an ion adduct molecule m / z value acquisition step of acquiring an m / z value for each of a plurality of peaks appearing in the mass spectrum; an adduct ion m / z value acquisition step of acquiring the m / z value of each of the plurality of adduct ions corresponding to the predetermined reaction gas from an adduct ion database in which the m / z values ​​of the plurality of adduct ions that can be generated are recorded for each reaction gas; a sample molecular weight determination step of determining a molecular weight of the sample molecule based on the m / z value of each of the plurality of peaks and the m / z value of each of the plurality of adduct ions acquired in the m / z value acquisition step; The mass spectrometry method according to claim 1,

2. moreover, an EI mass spectrum acquisition step of acquiring an EI mass spectrum, which is a mass spectrum when the sample molecule is cleaved by electron ionization; a fragment ion m / z value acquisition step of acquiring the m / z value of a peak appearing in the EI mass spectrum; a sample molecule candidate data acquisition step of acquiring molecular identification information for identifying a molecule and m / z values ​​of fragment ions generated from the molecule for a plurality of molecules having the same molecular weight as the sample molecule identified in the sample molecular weight identification step from a fragment ion database in which information for identifying the molecule, the molecular weight of the molecule, and the m / z values ​​of fragment ions generated from the molecule by electron ionization are recorded; a sample molecule identifying step of comparing the m / z value of the fragment ion acquired in the sample molecule candidate data acquiring step with the m / z value acquired in the fragment ion m / z value acquiring step for each of the plurality of molecules, and identifying the sample molecule based on molecular identifying information of a molecule among the plurality of molecules in which the two m / z values ​​match; The method of mass spectrometry according to claim 1 , comprising:

3. 3. The mass spectrometry method according to claim 1, wherein the sample molecules are molecules of components of a sample that has passed through a column of a gas chromatograph or a liquid chromatograph.

4. On the computer, a mass spectrum acquisition step of acquiring a mass spectrum of an ion adduct molecule generated by ionizing a predetermined reaction gas molecule to generate a reaction gas ion, and adding an adduct ion to the sample molecule by contacting the sample molecule with the reaction gas ion; an ion adduct molecule m / z value acquisition step of acquiring an m / z value for each of a plurality of peaks appearing in the mass spectrum; an adduct ion m / z value acquisition step of acquiring the m / z value of each of the plurality of adduct ions corresponding to the predetermined reaction gas from an adduct ion database in which the m / z values ​​of the plurality of adduct ions that can be generated are recorded for each reaction gas; a sample molecular weight determination step of determining a molecular weight of the sample molecule based on the m / z value of each of the plurality of peaks and the m / z value of each of the plurality of adduct ions acquired in the m / z value acquisition step; A mass spectrometry program which is a program for executing the above.

5. In addition, the computer an EI mass spectrum acquisition step of acquiring an EI mass spectrum, which is a mass spectrum when the sample molecule is cleaved by electron ionization; a fragment ion m / z value acquisition step of acquiring the m / z value of a peak appearing in the EI mass spectrum; a sample molecule candidate data acquisition step of acquiring molecular identification information for identifying a molecule and m / z values ​​of fragment ions generated from the molecule for a plurality of molecules having the same molecular weight as the sample molecule identified in the sample molecular weight identification step from a fragment ion database in which information for identifying the molecule, the molecular weight of the molecule, and the m / z values ​​of fragment ions generated from the molecule by electron ionization are recorded; a sample molecule identifying step of comparing the m / z value of the fragment ion acquired in the sample molecule candidate data acquiring step with the m / z value acquired in the fragment ion m / z value acquiring step for each of the plurality of molecules, and identifying the sample molecule based on molecular identifying information of a molecule among the plurality of molecules in which the two m / z values ​​match; The mass spectrometry program according to claim 4, which is a program for causing a user to execute the following:

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