Analytical device and analytical method

Abstract

To improve accuracy of estimating a composition of a compound.SOLUTION: A retention index is calculated on the basis of a detection time of a compound (specifically, the retention time). A molecular weight range and carbon atom number range are identified on the basis of the retention index. A search range is determined based on the molecular weight range. A molecular peak searcher 42 searches for molecular peaks within the search range set with respect to a mass spectrum of the compound. A composition estimator 48 estimates the composition of the compound on the basis of the precise mass identified from the molecular peak. During this process, the carbon atom number range is considered.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an analytical device and an analytical method, and in particular to a technique for estimating the composition of a compound. [Background technology]

[0002] Various analytical systems for qualitatively analyzing compounds are known, including an analytical system (GC-MS analytical system) that is composed of a gas chromatograph, a mass spectrometer, and an information processing device.

[0003] In a GC-MS analysis system, a gas chromatograph separates multiple compounds contained in a sample over time. A mass spectrometer performs mass analysis on each compound. An information processing device functions as a compound analysis device. Specifically, the information processing device generates a mass spectral sequence consisting of multiple mass spectra arranged in chronological order based on data output from the mass spectrometer, and generates a chromatogram based on the mass spectral sequence. For each peak included in the chromatogram, the composition (composition formula) of the compound is estimated based on the corresponding mass spectrum.

[0004] In the above-mentioned GC-MS analysis system, the time from when a sample is injected into the gas chromatograph until the compounds extracted from the sample by the gas chromatograph are detected by the mass spectrometer is generally called the retention time. The retention time is also called the elution time. The retention time varies depending on various conditions in the gas chromatograph (e.g., column type, column length, heating temperature).

[0005] The retention index is known as an alternative index to retention time. The retention index is an index calculated based on a series of retention times determined by introducing a reference substance (e.g., n-alkane) into a gas chromatograph (see, for example, Patent Document 1). The retention index is used to identify compounds. For example, when multiple compound candidates are selected based on the mass spectrum of an unknown compound, the multiple compound candidates are narrowed down by the retention index of the unknown compound (see, for example, Patent Document 2).

[0006] In the above-mentioned GC-MS analysis system, the mass spectrometer has an ion source for ionizing compounds. There are various known ionization methods. Among these, electron ionization (EI) is a type of hard ionization method. When EI is used, molecular ions of compounds may or may not be detected. In other words, a mass spectrum generated using an ion source conforming to EI (EI mass spectrum) may or may not contain a molecular peak (molecular ion peak).

[0007] It is extremely difficult for a user looking at an EI mass spectrum of an unknown compound to determine whether or not the EI mass spectrum contains a molecular peak of the unknown compound. Similarly, it is difficult to automatically identify molecular peaks in the EI mass spectrum of an unknown compound. Similar problems arise, depending on the circumstances, when using ionization methods other than EI. There is a need for technology that can accurately determine whether or not a molecular peak is present (and, if so, which one is the molecular peak) based on the mass spectrum of an unknown compound.

[0008] The information processing device in the above-mentioned GC-MS analysis system generally has a composition estimation function. Specifically, when the mass spectrum of an unknown compound includes a molecular peak, the exact mass corresponding to the molecular peak is identified, and multiple composition formula candidates are calculated based on the exact mass. Prior to this, the user specifies the atomic number range (lower and upper limits) for each representative element as a composition formula estimation condition. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 4438674 [Patent Document 2] Special Publication No. 2014-524568 Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to improve the accuracy of estimating the composition of a compound. Alternatively, an object of the present invention is to provide a technique for accurately identifying molecular peaks contained in the mass spectrum of a compound. Alternatively, an object of the present invention is to provide a technique for narrowing down the conditions for estimating the composition of a compound. [Means for solving the problem]

[0011] The analytical device according to the present invention comprises: An analyzer connected to a gas chromatograph and a mass spectrometer, wherein a conversion formula generated based on a reference detection time from when a reference substance is injected into the gas chromatograph until a compound in the reference substance passes through the gas chromatograph and is detected by the mass spectrometer is used to convert the sample into the gas chromatograph in the sample after being injected into the The compound Passing through the gas chromatograph Detected by mass spectrometry Until Detection Time of , the above in the sample Compound retention index Convert to a generator that generates a mass spectrum of the compound based on data obtained by mass analysis of the compound; a setter that sets a search range for the mass spectrum of the compound based on the retention index; and an estimator that, when a molecular peak corresponding to the compound is present within the search range in the mass spectrum of the compound, estimates the composition of the compound based on a molecular mass identified from the molecular peak.

[0012] The analytical method according to the present invention comprises: A conversion formula is generated based on a reference detection time from when a reference substance is injected into a gas chromatograph until a compound in the reference substance passes through the gas chromatograph and is detected by a mass spectrometer, and the sample is converted into the above gas chromatograph in the sample after being injected into the The compound Passing through the gas chromatograph Detected by mass spectrometry Until Detection Time of , the above in the sample Compound retention index Convert to generating a mass spectrum of the compound based on data obtained by mass spectrometry of the compound; setting a search range for the mass spectrum of the compound based on the retention index; and, when a molecular peak corresponding to the compound is present within the search range in the mass spectrum of the compound, estimating the composition of the compound based on the molecular mass identified from the molecular peak. [Effects of the Invention]

[0013] According to the present invention, it is possible to improve the accuracy of estimating the composition of a compound, or to correctly identify molecular peaks contained in the mass spectrum of a compound, or to narrow down the conditions for estimating the composition of a compound. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a block diagram illustrating an analysis system according to an embodiment. [Figure 2] FIG. 1 is a first scatter plot showing the relationship between retention index and molecular weight. [Figure 3] FIG. 10 is a second scatter plot showing the relationship between the retention index and the number of carbon atoms. [Figure 4] FIG. 10 is a diagram showing statistical information relating to molecular mass for each retention index interval. [Figure 5] FIG. 10 is a diagram showing statistical information relating to the number of carbon atoms for each retention index interval. [Figure 6] FIG. 10 is a diagram showing an example in which a molecular peak exists within a molecular mass range. [Figure 7] FIG. 10 is a diagram showing an example in which no molecular peak exists within the molecular mass range. [Figure 8] FIG. 10 is a diagram showing a partial change of the composition estimation conditions. [Figure 9] FIG. 1 is a diagram illustrating a composition estimation method. [Figure 10] FIG. 1 is a flowchart showing an analysis method according to an embodiment. [Figure 11] FIG. 1 shows an example of searching for monoisotopic peaks: DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment will be described with reference to the drawings.

[0016] (1) Overview of the embodiment An analytical apparatus according to an embodiment includes a calculator, a generator, a setter, and an estimator. The calculator calculates a retention index of a compound based on a detection time at which the compound is detected by a mass spectrometer from a gas chromatograph. The generator generates a mass spectrum of the compound based on data obtained by mass analysis of the compound. The setter sets a search range for the mass spectrum of the compound based on the retention index. When a molecular peak corresponding to the compound is present within the search range in the mass spectrum of the compound, the estimator estimates the composition of the compound based on a molecular mass identified from the molecular peak.

[0017] According to the above configuration, since a molecular peak is searched for within the search range, the accuracy of identifying the molecular peak can be improved, which in turn improves the accuracy of estimating the composition of the compound.

[0018] The time from when a sample is injected into a gas chromatograph until a compound extracted from the sample in the gas chromatogram is detected by a mass spectrometer is generally referred to as retention time. The detection time is the retention time or a time equivalent to the retention time. The search range is the range in which a molecular peak is searched for, specifically, a mass-to-charge ratio range. In an embodiment, the search range is set based on a molecular weight range or a molecular mass range. The lower and upper limits of the search range are specified by molecular weight, integer mass, or exact mass. The molecular mass for composition estimation, which is specified from the molecular peak, is usually an exact mass. The molecular peak is specified automatically or by the user. The processor described below corresponds to the calculator, generator, setter, and estimator.

[0019] In an embodiment, the setting unit sets the search range according to a first mathematical model that determines the upper and lower limits of the search range based on the retention index. The first mathematical model is configured by, for example, one or both of a table and a formula.

[0020] In an embodiment, the first mathematical model is a mathematical model generated based on information on a plurality of compounds registered in a compound database, each of which includes a retention index and information indicating a molecular mass.

[0021] The analytical apparatus according to the embodiment further includes a searcher that searches for a molecular peak within a search range in the mass spectrum of the compound. With this configuration, the molecular peak is automatically identified.

[0022] In an embodiment, the searcher identifies, as a candidate peak, a peak that satisfies a peak intensity condition for peak intensity and is located on the highest mass side among one or more peaks within the search range. If a peak that satisfies the peak intensity condition and the monoisotopic condition exists on the lower mass side of the candidate peak, the searcher determines the peak as a molecular peak. If no peak that satisfies the peak intensity condition and the monoisotopic condition exists on the lower mass side of the candidate peak, the searcher determines the candidate peak as a molecular peak. This configuration makes it possible to determine a monoisotopic peak as a molecular peak, thereby enabling accurate composition estimation. The monoisotopic condition is a condition for identifying a monoisotopic peak from among multiple isotopic peaks.

[0023] In an embodiment, when a molecular peak is not present within the search range of the mass spectrum of a compound, information indicating non-detection of a molecular ion is provided to the user, which can encourage the adoption of other composition estimation methods that do not rely on molecular peaks.

[0024] The analytical instrument according to the embodiment further includes a display processor that displays a range image indicating the search range together with the mass spectrum. This configuration allows the user to easily identify molecular peaks or to confirm that the search range has been set correctly.

[0025] In an embodiment, the setter is a first setter, and a second setter is provided that sets a carbon atom number range based on the retention index. The estimator estimates the composition of the compound according to composition estimation conditions including the carbon atom number range. This configuration improves the accuracy of estimating the composition of the compound.

[0026] In an embodiment, the second setter sets the carbon atom number range according to a second mathematical model that determines the lower and upper limits of the carbon atom number range based on the retention index, and the second mathematical model is configured by one or both of a table and a calculation formula.

[0027] In an embodiment, the second mathematical model is a mathematical model generated based on information on a plurality of compounds registered in a compound database, each of which includes a retention index and information indicating the number of carbon atoms.

[0028] The analytical method according to the embodiment includes a calculation step, a generation step, a setting step, and an estimation step. In the calculation step, a retention index of the compound is calculated based on the detection time at which the compound from the gas chromatograph is detected by a mass spectrometer. In the generation step, a mass spectrum of the compound is generated based on data obtained by mass analysis of the compound. In the setting step, a search range is set for the mass spectrum of the compound based on the retention index. In the estimation step, when a molecular peak corresponding to the compound is present within the search range in the mass spectrum of the compound, the composition of the compound is estimated based on the molecular mass identified from the molecular peak. The detection time is the retention time or a time equivalent to the retention time.

[0029] The above-described analysis method can be realized as a hardware function or a software function. In the latter case, a program for executing the above-described analysis method is installed in an information processing device via a network or a portable storage medium. The information processing device is provided with a non-transitory storage medium for storing the program. The information processing device is, for example, a computer, an analysis system, etc. Part of the analysis system may be configured by a computer on the network.

[0030] (2) Details of the embodiment An analytical system according to an embodiment is shown in Figure 1. The analytical system is a system that performs mass spectrometry and composition estimation on each compound separated from a sample.

[0031] 1, the analysis system includes a gas chromatograph (GC) 10, a mass spectrometer 12, and an information processing device 14. The information processing device 14 is an analysis device that executes the analysis method according to the embodiment. The GC 10 includes a column that temporally separates multiple compounds contained in a sample. The separated multiple compounds are sequentially introduced into the mass spectrometer 12.

[0032] The mass spectrometer 12 has an ion source 16, a mass analyzer 18, and a detector 20. The ion source 16 is an ion source that complies with electron ionization (EI). Ion sources that complies with other ionization methods may also be used. In the ion source 16, each compound is ionized. The ions thus generated are introduced into the mass analyzer 18. The mass analyzer 18 is, for example, a time-of-flight mass analyzer or a quadrupole mass analyzer. The ions that pass through the mass analyzer 18 are detected by the detector 20. A detection signal output from the detector 20 is input to the information processing device 14 via a signal processing circuit (not shown).

[0033] The information processing device 14 is configured, for example, by a computer, which has an information processing unit 22, a memory unit 24, an input unit 26, and a display unit 28. The information processing unit 22 has a processor that executes a program. The processor is, for example, a CPU. In FIG. 1, the multiple functions performed by the information processing unit 22 are represented by multiple blocks. The memory unit 24 is configured by a semiconductor memory, a hard disk, etc. The input unit 26 is configured by a keyboard, etc. The display unit 28 is configured by a liquid crystal display, etc.

[0034] The mass spectrum generator 30 generates a mass spectrum train consisting of a plurality of mass spectra arranged on a time axis based on a series of detection signals generated by mass analysis of a plurality of compounds. The mass spectrum train is sent to the chromatogram generator 32 and a display processor 44. The chromatogram generator 32 generates a total ion chromatogram (TICC), which is a type of chromatogram, for example, by integrating each mass spectrum that makes up the mass spectrum train.

[0035] The chromatogram contains multiple compound peaks corresponding to multiple compounds separated from the sample. The compound peak detector 34 detects the multiple compound peaks contained in the chromatogram. The compound peak detector 34 identifies the retention time corresponding to a representative point (e.g., peak top) in each compound peak. The retention time can also be referred to as the detection time. The retention time is an index that varies depending on the column length, column type, column temperature, etc.

[0036] The retention index calculator 36 converts the retention time into a retention index for each compound peak. In this embodiment, a reference substance is measured prior to the measurement of a sample. Based on a plurality of retention times corresponding to a plurality of peaks included in the chromatogram generated by the measurement, parameters (conversion formula) for converting the retention time into a retention index are specified in advance. During the measurement of the sample, the retention index calculator 36 uses the parameters to calculate the following for each compound: retentionThe retention time is converted into a retention index. n-Alkanes are known as typical reference substances. The sample and reference substance may be measured simultaneously. The retention index is an objective index that is not dependent on the column length, column type, column temperature, etc.

[0037] In an embodiment, when estimating the composition of each compound, a molecular weight range and a carbon atom number range are determined based on the retention index, and a search range is set based on the molecular weight range.

[0038] The first setter 38 is a search range setter. For each compound peak included in the chromatogram (i.e., for each unknown compound), the first setter 38 sets a search range for the mass spectrum corresponding to that compound peak based on the retention index corresponding to that compound peak. More specifically, the first setter 38 determines a molecular weight range from the retention index and sets the search range based on the molecular weight range. The search range is a mass-to-charge ratio range. A molecular mass range may be determined instead of the molecular weight range, or the search range may be determined directly instead of the molecular weight range.

[0039] The search range is the range in which the molecular peak (molecular ion peak) is searched. By searching for the molecular peak within the search range, the molecular peak can be correctly identified. This in turn improves the accuracy of estimating the composition of the compound.

[0040] As will be described later, the average molecular weight (μa) and standard deviation of molecular weight (σa) are determined in advance for each retention index interval. Based on the average (μa) and standard deviation (σa) associated with the retention index interval to which the calculated retention index belongs, the lower and upper limits of the molecular weight range are determined as follows:

[0041] Lower limit of molecular weight range: μa-k1×σa (1-1) Upper limit of molecular weight range: μa + k1 × σa (1-2)

[0042] Here, k1 is, for example, 3. k1 can be changed by the user. For example, k1 may be set to 1 or 2. The search range on the mass-to-charge ratio axis is uniquely determined from the molecular weight range.

[0043] The second setter 40 is an atom number range setter. The second setter 40 sets a carbon atom number range for each compound peak included in the chromatogram (i.e., for each unknown compound) based on the retention index corresponding to that compound peak. The carbon atom number range constitutes part of the composition estimation conditions. By estimating the composition of a compound according to the composition estimation conditions including the automatically determined carbon atom number range, the accuracy of estimating the composition of the compound can be improved.

[0044] As will be described later, the average number of carbon atoms (μb) and the standard deviation (σb) of the number of carbon atoms are determined in advance for each retention index interval. From the average (μb) and standard deviation (σb) associated with the retention index interval to which the calculated retention index belongs, the lower and upper limits of the range of the number of carbon atoms are determined as follows:

[0045] Lower limit of carbon atom number range: μb-k2×σb (2-1) Upper limit of carbon atom number range: μb + k2 × σb (2-2)

[0046] Here, k2 is, for example, 3. k2 can be changed by the user. For example, k2 may be set to 1 or 2.

[0047] The molecular peak searcher 42 searches for a molecular peak within a search range set in the mass spectrum of each compound. The mass spectrum is typically an integrated mass spectrum generated by integrating multiple mass spectra corresponding to compound peaks. As described below, the molecular peak is searched for so that both the peak intensity condition and the monoisotopic condition are satisfied.

[0048] The composition estimator 48 estimates the composition (composition formula) of the unknown compound based on the molecular mass (accurate mass) identified from the molecular peak of the unknown compound in accordance with the composition estimation conditions. The composition estimation conditions include multiple atomic number ranges corresponding to multiple elements. Within the multiple atomic number ranges, the upper and lower limits of the range of carbon atom numbers are determined by the second setter 40, as described above. The other multiple atomic number ranges are typically determined by the user.

[0049] The display processor 44 generates an image to be displayed on the screen of the display 28. The display processor 44 has a range image generator 46. The range image generator 46 generates a range image that indicates a search range set for the mass spectrum of an unknown compound.

[0050] The display 28 displays a chromatogram, a compound peak table, and the like. The compound peak table includes multiple rows corresponding to multiple compounds. Each row includes a retention time, a retention index, and the like. When a row is selected, information associated with that row is displayed. In this case, for example, a mass spectrum, a list showing the composition estimation results, and the like are displayed. The mass spectrum includes a range image. The mass spectrum may also include information specifying the identified molecular peaks.

[0051] 2 and 3 show two scatter plots created based on information on multiple compounds registered in an existing compound database. The information on each compound includes retention index, molecular weight, molecular mass, compositional formula, etc. The molecular weight and molecular mass are both information that indicates the mass of a molecule. The compositional formula is information that indicates the number of carbon atoms. The existing compound database is, for example, a mass spectrum database provided by NIST (National Institute of Standards and Technology).

[0052] In the scatter diagram shown in Figure 2, the horizontal axis represents molecular weight, and the vertical axis represents retention index. The axis representing molecular mass may be used instead of the axis representing molecular weight. In this case, the molecular mass is an integer mass or an exact mass. As shown in Figure 2, a positive correlation is observed between retention index and molecular weight.

[0053] In the scatter diagram shown in Figure 3, the horizontal axis represents the number of carbon atoms, and the vertical axis represents the retention index. As shown in Figure 3, a positive correlation is observed between the retention index and the number of carbon elements. For other elements, a correlation like that shown in Figure 3 is usually not observed.

[0054] 4 and 5 show two tables 50 and 60 created based on information on a plurality of compounds registered in the compound database.

[0055] Table 50 shown in Fig. 4 is a table for identifying the average (μa) and standard deviation (σa) of molecular weight from the retention index. Table 60 shown in Fig. 5 is a table for identifying the average (μb) and standard deviation (σb) of the number of carbon atoms (number of C atoms) from the retention index.

[0056] The two tables 50 and 60 are stored in the memory unit shown in Figure 1. The above calculation formulas (1-1), (1-2), (2-1), and (2-2) are also stored in the memory unit shown in Figure 1. The first mathematical model is configured by table 50 and the above calculation formulas (1-1) and (1-2). The second mathematical model is configured by table 60 and the above calculation formulas (2-1) and (2-2).

[0057] Specifically, in the table 50 shown in FIG. 4, the retention index (RI) interval column 52 is composed of a plurality of retention index intervals 52A. For each retention index interval 52A, the average (μa) and standard deviation (σa) of the molecular weight are registered. When the retention index of an unknown compound is identified, the average (μa) and standard deviation (σa) are identified based on the retention index by referring to the table 50. The molecular weight range is calculated by substituting these into the above formulas (1-1) and (1-2). The search range is determined from the molecular weight range.

[0058] In the table 60 shown in Fig. 5, the retention index (RI) interval column 62 is composed of a plurality of retention index intervals 62A. For each retention index interval 62A, the average (μb) and standard deviation (σb) of the number of carbon atoms are registered. When the retention index of an unknown compound is identified, the average (μb) and standard deviation (σb) are identified based on the retention index by referring to the table 60. The range of the number of carbon atoms is calculated by substituting these values ​​into the above formulas (2-1) and (2-2).

[0059] 6 and 7 show two mass spectra 69 and 81 displayed on a display. In each of the mass spectra 69 and 81, the horizontal axis is the mass-to-charge ratio (m / z) axis, and the vertical axis is the intensity axis.

[0060] A search range 70 is set in the mass spectrum (EI mass spectrum) 69 shown in Fig. 6. For example, when the retention index is 1500, the lower limit of the molecular weight range is set to 150, and the upper limit of the molecular weight range is set to 250. The lower and upper limits of the search range 70 are set based on these lower and upper limits.

[0061] A search range 70 is represented by a range image 71. In the illustrated example, the range image 71 includes two lines 72A and 72B and a colored area 76 between them. Line 72A represents the lower limit of the search range 70, and line 72B represents the upper limit of the search range 70. Within the search range 70, a molecular peak that satisfies the peak intensity condition and the monoisotopic condition is searched for. In the illustrated example, a molecular peak 78 has been identified. In this case, an accurate mass 80 is identified from the mass-to-charge ratio corresponding to the molecular peak 78. The accurate mass is used to estimate the composition of the unknown compound.

[0062] A search range 82 is set in a mass spectrum (EI mass spectrum) 81 shown in Fig. 7. For example, when the retention index is 1950, the lower limit of the molecular weight range is determined to be 220, and the upper limit of the molecular weight range is set to 320. The lower and upper limits of the search range 82 are set based on these lower and upper limits.

[0063] Search range 82 is represented by range image 71A. In the illustrated example, range image 71A includes two lines 83A and 83B and a colored area 84. Search range 82 does not include any molecular peaks.

[0064] In Figure 8, composition estimation conditions 86 are set by the user. The composition estimation conditions 86 have multiple atomic number ranges corresponding to multiple elements. Each atomic number range is defined by a lower limit and an upper limit. For carbon, the lower limit is 0 and the upper limit is 50 (see symbols 90a and 92a).

[0065] 8, composition estimation conditions 88 are composition estimation conditions that have been changed based on the range of the number of carbon atoms set as described above. The lower limit of the range of the number of carbon atoms has been changed to 7 (see reference numeral 90b), and the upper limit has been changed to 15 (see reference numeral 92b).

[0066] FIG. 9 shows a composition estimation method. The left side of formula 94 is the molecular mass (exact mass). The molecular mass is determined from the mass-to-charge ratio corresponding to the molecular peak (see reference numeral 102). More specifically, the molecular mass is determined by adding the mass of an electron to the mass corresponding to the mass-to-charge ratio corresponding to the molecular peak. The right side of formula 94 includes C atomic mass (exact mass) 96, H atomic mass (exact mass) 98, O atomic mass (exact mass) 100, etc. The right side of formula 94 also includes coefficient n1 by which C atomic mass 96 is multiplied, coefficient n2 by which H atomic mass 98 is multiplied, coefficient n3 by which O atomic mass 100 is multiplied, etc.

[0067] Each coefficient n1, n2, n3,... is an integer equal to or greater than 0 and within each atomic number range defined by the composition estimation condition 104. In an embodiment, n1 is assigned an integer that falls within the range of the number of carbon atoms determined based on the retention index of the unknown compound (see reference numeral 106). Each coefficient is adjusted so that the formula 94 holds true, and the atomic number of each element is narrowed down. This allows the composition of the unknown compound to be estimated. Multiple compositions may be estimated.

[0068] The analytical method according to the embodiment is shown as a flowchart in Figure 10. The series of steps shown in Figure 10 is executed for each unknown compound.

[0069] In S10, the retention index (RI) is calculated from the retention time (RT). A pre-specified conversion formula is used. In S12, a search range based on the retention index is set for the mass spectrum of the unknown compound. In S13, a molecular peak is searched for within the search range. In this case, a peak that satisfies the peak intensity condition and the monoisotopic condition is determined to be a molecular peak.

[0070] The peak intensity condition is a condition that the intensity of a molecular peak must satisfy. In an embodiment, the maximum intensity is identified from among the intensities of the peaks contained in the mass spectrum. Then, a threshold value corresponding to α% (e.g., α=10) of the maximum intensity is set. α is specified or changed by the user. Peaks that exceed the threshold value are peaks that satisfy the peak intensity condition. Other conditions may also be defined as the peak intensity condition.

[0071] Monoisotopic conditions are conditions for identifying a monoisotopic peak as a molecular peak. If any element contained in an unknown compound has multiple isotopes, multiple isotopic peaks will occur. Among the multiple isotopic peaks, the peak corresponding to the highest abundance ratio is the monoisotopic peak. With some exceptions, the isotopic peak with the lowest mass among the multiple isotopic peaks is the monoisotopic peak, and the conditions for identifying it are monoisotopic conditions.

[0072] In S14, it is determined whether or not a molecular peak exists within the search range. If a molecular peak is not identified, a message to that effect is displayed in S16. In other words, a message indicating that a molecular ion has not been detected is displayed. This prompts the user to apply another composition estimation method. Examples of other composition estimation methods include composition estimation methods based on fragment peaks and neutral losses.

[0073] If a molecular peak is identified within the search range, in S18, the molecular mass (accurate mass) is identified based on the mass-to-charge ratio corresponding to the molecular peak. In S20, the carbon atom number range is set according to the retention index, and the composition estimation conditions set by the user are partially changed accordingly. In S22, the composition is estimated based on the molecular mass. If the composition estimation fails, this is determined in S24, and then information indicating the failure of the composition estimation is provided to the user in S26. On the other hand, if the composition estimation is successful, this is determined in S24, and then the composition estimation result is displayed in S28.

[0074] A specific example of S13 above will be explained using Figure 11. Figure 11 shows the mass spectrum of an unknown compound. A search range 108 has been set for it. A threshold value α for determining whether the peak intensity condition is satisfied is also shown.

[0075] First, within the search range 108, a peak 111 on the highest mass side exceeding the threshold α is identified as a primary candidate peak. A first sub-search range 114 and a second sub-search range 116 are set based on the primary candidate peak 111. Masses mi-1 and mi-2 are identified based on the mass mi corresponding to the peak 111. The first sub-search range 114 is a local range centered on the mass mi-1. The second sub-search range 116 is a local range centered on the mass mi-2.

[0076] If a peak 112 exceeding the threshold value α exists within the first sub-search range 114, the peak 112 is determined to be a secondary candidate peak. If a peak 113 exceeding the threshold value α exists within the second sub-search range 116, the peak 113 is determined to be a tertiary candidate peak. Of the one or more candidate peaks included in the search range 108, the peak with the lowest mass is considered to be the molecular peak. In the example shown in FIG. 11, peak 113 is determined to be the molecular peak of an unknown compound. If a primary candidate peak cannot be identified within the search range 108, information indicating that a molecular ion was not detected is provided to the user.

[0077] As a result, a molecular peak that satisfies the peak intensity condition and the monoisotopic condition is correctly identified.

[0078] According to the above embodiment, molecular peaks contained in the mass spectrum of a compound can be correctly identified, and conditions for estimating the composition of the compound can be narrowed down, thereby improving the accuracy of estimating the composition of the compound. In the above embodiment, the gas chromatograph may be replaced with a liquid chromatograph. Even in such a modified example, composition estimation similar to that described above can be performed. Only one of the above techniques for setting the search range and the above technique for setting the carbon atom number range may be employed. [Explanation of symbols]

[0079] 10 gas chromatograph, 12 mass spectrometer, 14 information processing device, 32 chromatogram generator, 34 compound peak detector, 36 retention index calculator, 38 first setter (molecular weight range setter), 40 second setter (carbon atom number range setter), 42 molecular peak searcher, 44 display processor, 46 range image generator, 48 composition estimator.

Claims

1. An analytical device connected to a gas chromatograph and a mass spectrometer, comprising: a calculator that converts a detection time from when a reference substance is injected into the gas chromatograph until a compound in the reference substance passes through the gas chromatograph and is detected by the mass spectrometer into a retention index of the compound in the sample, using a conversion formula generated based on a reference detection time from when a reference substance is injected into the gas chromatograph until a compound in the reference substance passes through the gas chromatograph and is detected by the mass spectrometer; a generator for generating a mass spectrum of the compound based on data obtained by mass analysis of the compound; a setting unit that sets a search range for the mass spectrum of the compound based on the retention index; an estimator that, when a molecular peak corresponding to the compound is present within the search range in the mass spectrum of the compound, estimates the composition of the compound based on a molecular mass identified from the molecular peak; An analytical device comprising:

2. 2. The analyzer according to claim 1, the setter sets the search range according to a first mathematical model that determines a lower limit and an upper limit of the search range based on the retention index; An analytical device characterized by:

3. 3. The analyzer according to claim 2, the first mathematical model is a mathematical model generated based on information on a plurality of compounds registered in a compound database, The information on each compound includes a retention index and information indicating a molecular mass. An analytical device characterized by:

4. 2. The analyzer according to claim 1, a searcher that searches for the molecular peak within the search range in the mass spectrum of the compound; An analytical device characterized by:

5. 5. The analyzer according to claim 4, The searcher Among the one or more peaks belonging to the search range, a peak that satisfies a peak intensity condition and is located on the highest mass side is identified as a candidate peak; If a peak that satisfies the peak intensity condition and the monoisotopic condition exists on the low mass side of the candidate peak, the peak is determined to be the molecular peak; If there is no peak on the low mass side of the candidate peak that satisfies the peak intensity condition and the monoisotopic condition, the candidate peak is determined to be the molecular peak. An analytical device characterized by:

6. 5. The analyzer according to claim 4, If the molecular peak is not present within the search range in the mass spectrum of the compound, information indicating non-detection of the molecular ion is provided to the user. An analytical device characterized by:

7. 2. The analyzer according to claim 1, a display processor that displays a range image showing the search range together with the mass spectrum; An analytical device characterized by:

8. 2. The analyzer according to claim 1, the setting device is a first setting device, a second setter that sets a range of the number of carbon atoms based on the retention index; the estimator estimates the composition of the compound according to composition estimation conditions including the range of the number of carbon atoms; An analytical device characterized by:

9. The analytical device according to claim 8, the second setter sets the range of the number of carbon atoms in accordance with a second mathematical model that determines a lower limit and an upper limit of the range of the number of carbon atoms based on the retention index. An analytical device characterized by:

10. 10. The analyzer according to claim 9, the second mathematical model is a mathematical model generated based on information on a plurality of compounds registered in a compound database, The information on each compound includes a retention index and information indicating the number of carbon atoms. An analytical device characterized by:

11. A process of converting the detection time from when a sample is injected into the gas chromatograph until when a compound in the sample passes through the gas chromatograph and is detected by the mass spectrometer into a retention index of the compound in the sample, using a conversion formula generated based on a reference detection time from when a reference substance is injected into the gas chromatograph until when a compound in the reference substance passes through the gas chromatograph and is detected by the mass spectrometer; generating a mass spectrum of the compound based on data obtained by mass spectrometry of the compound; setting a search range for the mass spectrum of the compound based on the retention index; a step of estimating the composition of the compound based on a molecular mass identified from a molecular peak when a molecular peak corresponding to the compound is present within the search range in the mass spectrum of the compound; An analytical method comprising:

12. A program executed in an information processing device, a function of converting a detection time from when a sample is injected into the gas chromatograph until when a compound in the sample passes through the gas chromatograph and is detected by the mass spectrometer into a retention index of the compound in the sample, using a conversion formula generated based on a reference detection time from when a reference substance is injected into the gas chromatograph until when a compound in the reference substance passes through the gas chromatograph and is detected by the mass spectrometer; a function of generating a mass spectrum of the compound based on data obtained by mass analysis of the compound; a function of setting a search range for the mass spectrum of the compound based on the retention index; a function of estimating the composition of the compound based on a molecular mass identified from a molecular peak when a molecular peak corresponding to the compound is present within the search range in the mass spectrum of the compound; and A program comprising:

Images