Optimal selection method and system for quantitative ions and qualitative ions in gas chromatography-mass spectrometry selected ion monitoring mode analysis method
By screening the characteristic ions of the analyte in the gas chromatography mass spectrometry combination selection ion monitoring mode, screening candidate ions using mass-charge ratio and relative abundance threshold, and verifying the specificity by matrix spiking method, the problem of low screening efficiency in the prior art is solved, and more efficient and accurate analysis results are achieved.
Patent Information
- Application Number
- CN202510184528.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-19
- Publication Date
- 2025-06-27
AI Technical Summary
In the existing gas chromatography mass spectrometry combined with selective ion monitoring mode, the characteristic ion efficiency of screening analytes is low, resulting in inaccurate quantitative and qualitative analysis results, and rely on experience and consume a lot of manpower and material resources.
By obtaining the mass spectral information of the analyte, candidate ions are selected and screened through mass-to-charge ratio and relative abundance threshold, the ion specificity is verified with matrix spiking method to ensure that the screened characteristic ions take into account both specificity and sensitivity.
It improves the screening efficiency and accuracy of characteristic ions of analytes, reduces experience dependence, saves labor and time costs, and improves the accuracy and sensitivity of the analytical methods.
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Figure CN120214130A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method and system for optimizing quantitative ions and qualitative ions in the analysis method of gas chromatography-mass spectrometry selective ion monitoring mode, and belongs to the technical field of analytical chemistry. Background Art
[0002] Gas chromatography-mass spectrometry (GC-MS) combines the characteristics of gas chromatography and mass spectrometry, and is mainly used for the analysis and identification of compounds in samples. At present, it has been widely used in many fields such as industrial detection, food safety, and environmental protection. Selective ion monitoring (SIM) as a working mode of GC-MS detection only detects the selected ions of the target compound, and other ions are not recorded. Compared with the full-scan technology, a large number of interfering ions are excluded, and the detection sensitivity is significantly improved, which is more advantageous for quantitative analysis. However, since the SIM mode can only detect a limited number of ions and cannot obtain a complete mass spectrum, if the selected ions have good specificity, the presence of the target substance (analyte) can be accurately determined; if the selected ions are non-specific ions, it will result in incorrect analysis results. Therefore, in order to ensure the accuracy of the analysis, it is of great significance to screen out characteristic ions with strong specificity and high sensitivity for the target substance.
[0003] The mass-to-charge ratio and response intensity of fragment ions directly affect the specificity and sensitivity of the target substance. At present, when chromatographic analysts analyze samples using the gas chromatography-mass spectrometry selective ion monitoring mode (GC-MS-SIM), the screening of quantitative ions and qualitative ions of the target substance mainly relies on work experience. According to the mass spectrum of the target substance in the collected standard solution, two fragment ions with higher response intensity and / or larger mass-to-charge ratio are selected as the quantitative ion and qualitative ion of the target substance respectively. However, usually, it is often impossible to have both a large response intensity and a large mass-to-charge ratio for fragment ions. At the same time, due to the very complex actual sample matrix and the requirement of simultaneous detection of multiple target substances, the phenomenon that the qualitative and quantitative ions screened by traditional work experience are non-specific ions or have insufficient sensitivity occurs. In the actual sample analysis process, chromatographic analysts often need to repeatedly test and verify the specificity and sensitivity of the selected ions for different target substances and different sample matrices, consuming a large amount of manpower and material resources. Summary of the Invention
[0004] The purpose of the present invention is to provide a method for optimizing quantitative ions and qualitative ions in the analysis method of gas chromatography-mass spectrometry selective ion monitoring mode, which can solve the problem of low efficiency in screening characteristic ions of analytes at present.
[0005] Another object of the present invention is to provide a preferred system for quantitative ions and qualitative ions in a gas chromatography-mass spectrometry selected ion monitoring mode analysis method, which can solve the problem of low efficiency in screening characteristic ions of analytes at present.
[0006] In order to achieve the above object, the technical solution adopted by the preferred method for quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method of the present invention is as follows:
[0007] A preferred method for quantitative ions and qualitative ions in a gas chromatography-mass spectrometry selected ion monitoring mode analysis method includes the following steps:
[0008] (1) Obtain the mass spectrometry information of the analyte, where the mass spectrometry information includes the mass-to-charge ratio, response intensity, and relative abundance of the fragment ions collected after the analyte is ionized;
[0009] (2) Select candidate ions from all the fragment ions corresponding to the analyte;
[0010] The method for selecting candidate ions is as follows:
[0011] S1, Set the relative abundance threshold and the mass-to-charge ratio threshold, and define the fragment ions with a relative abundance not less than the relative abundance threshold and a mass-to-charge ratio not less than the mass-to-charge ratio threshold among all the fragment ions corresponding to the analyte as the primary selected ions;
[0012] S2, Select the fragment ion with the largest relative abundance from all the primary selected ions as the candidate ion, and then select alternative ions from all the primary selected ions; alternative ions refer to fragment ions that meet the following conditions: if the difference between the mass-to-charge ratio of a certain fragment ion and the mass-to-charge ratio of the candidate ion is less than -6 or greater than 6, then the fragment ion is an alternative ion;
[0013] S3, Use the alternative ions obtained in step S2 as the new primary selected ions, repeat step S2, and obtain new candidate ions and alternative ions;
[0014] S4, Repeat step S3 until all candidate ions are selected;
[0015] (3) Use each candidate ion as the mass spectrometry detection ion, perform GC-MS analysis to obtain the chromatogram of the analyte under different candidate ions, then determine the characteristic ions, and finally select the quantitative ions and qualitative ions from the characteristic ions.
[0016] The preferred method for quantitative and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method of the present invention is simple and fast, and the selected candidate ions are comprehensive and without omission. In addition, the present invention verifies the ion specificity by matrix spike method, ensuring that the selected ions are not affected by the sample matrix, and improving the accuracy and sensitivity of the established analysis method. The preferred method for quantitative and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method of the present invention has the advantages of fast, efficient, time-saving and labor-cost-saving.
[0017] Preferably, when there are more than two analytes, after obtaining the candidate ions, all non-target ions are removed from the candidate ions to obtain the preferred candidate ions, and then the preferred candidate ions are used as the mass spectrometry detection ions to perform GC-MS analysis on the analyte solution and the sample matrix spike solution respectively. Then, the characteristic ions corresponding to each analyte are determined according to the method in step (3). Finally, the quantitative and qualitative ions are selected from the characteristic ions; the non-target ions refer to the candidate ions that meet the following conditions: if the difference in retention time between analyte A and analyte B is less than the retention time threshold, and the mass-to-charge ratio of candidate ion C corresponding to analyte A is the same as the mass-to-charge ratio of candidate ion D corresponding to analyte B, then candidate ion C is the non-target ion of analyte A.
[0018] Preferably, the retention time threshold is 0.1 - 0.3 min.
[0019] Preferably, in step (3), the objects of GC-MS analysis are the analyte solution and the sample matrix spike solution; the method for determining the characteristic ions is as follows: if there are no interference peaks in the chromatograms of the analytes obtained by performing GC-MS analysis on the analyte solution and the sample matrix spike solution with a certain candidate ion as the mass spectrometry detection ion, then the candidate ion is a characteristic ion; the number of the characteristic ions is not less than 2.
[0020] Preferably, the relative abundance threshold is 1% - 10%; the mass-to-charge ratio threshold is 40 - (A × 50%) m / z, where A is equal to the molecular weight of the analyte.
[0021] Preferably, the selection principle of the quantitative ion is as follows: if the chromatographic response intensity of the analyte corresponding to a certain characteristic ion is greater than the chromatographic response intensity of the analytes corresponding to other characteristic ions, then the characteristic ion is the quantitative ion of the analyte; the chromatographic response intensity of the analyte corresponding to the characteristic ion refers to the chromatographic response intensity of the analyte obtained by performing GC-MS analysis on the analyte solution and the sample matrix spike solution with the characteristic ion as the mass spectrometry detection ion.
[0022] Preferably, in step (1), the mass spectrometry information of the analyte is obtained by performing GC-MS analysis on the standard solution of the analyte.
[0023] Preferably, in the standard solution, the concentration of the analyte is 0.5 - 50 ppm.
[0024] Preferably, in step (1), the mass spectrometry scanning range during the GC-MS analysis is 30 - 700 amu; the mass spectrometry scanning mode used for the GC-MS analysis of the standard solution of the analyte is the full scan mode.
[0025] It can be understood that if there are only 2 characteristic ions, after selecting the quantitative ion, the remaining one characteristic ion is the qualitative ion of the analyte; if there are more than 2 characteristic ions, after selecting the quantitative ion, a characteristic ion with a relatively larger chromatographic response intensity of the analyte is selected from the remaining characteristic ions as the qualitative ion.
[0026] The technical solution adopted by the preferred system of the quantitative ion and qualitative ion in the gas chromatography - mass spectrometry selected ion monitoring mode analysis method of the present invention is as follows:
[0027] A preferred system of quantitative ions and qualitative ions in a gas chromatography - mass spectrometry selected ion monitoring mode analysis method, comprising a processor and a memory, the processor is used to execute instructions stored in the memory to implement the preferred method of quantitative ions and qualitative ions in the gas chromatography - mass spectrometry selected ion monitoring mode analysis method as described above.
[0028] The preferred system of quantitative ions and qualitative ions in the gas chromatography - mass spectrometry selected ion monitoring mode analysis method of the present invention can be simple and fast, and the selected candidate ions are comprehensive and without omission, improving the accuracy and sensitivity of the established analysis method.
[0029] The preferred system of quantitative ions and qualitative ions in the gas chromatography - mass spectrometry selected ion monitoring mode analysis method of the present invention includes a spectral graph digitization module, a candidate ion selection module, a non - target ion elimination module, and a characteristic ion confirmation module; the spectral graph digitization module is used to convert the format of the full - scan mass spectrometry graph of the analyte into digital mass spectrometry information; the candidate ion selection module is used to select candidate ions from all the fragment ions of the analyte; the non - target ion elimination module is aimed at avoiding the mutual interference between analytes with similar structures. When there are two or more analytes, after obtaining the candidate ions, all non - target ions are eliminated from the candidate ions to obtain the preferred candidate ions; the characteristic ion confirmation module is used to verify that the candidate ions are not interfered by the sample matrix through the sample matrix spike - addition method, then confirm the candidate ions as the characteristic ions of the analyte, and finally select the quantitative ions and qualitative ions from the characteristic ions.
[0030] The beneficial effects of the present invention are as follows:
[0031] The automatic screening system and method for characteristic ions of analytes in the selected ion monitoring mode of gas chromatography-mass spectrometry of the present invention, when screening the characteristic ions of analytes, not only based on the mass spectrometry fragmentation mechanism of the analytes themselves, but also avoids the mutual interference between structurally similar analytes and sample matrix interference during the simultaneous detection of multiple targets. The selected characteristic ions take into account both specificity and sensitivity; the present invention digitalizes, standardizes, and processes the characteristic ion screening process of analytes. Compared with traditional methods, it greatly reduces the dependence on the experience of chromatographic analysts, and at the same time, there is no need to repeatedly test and verify the specificity and sensitivity of the selected ions, improving work efficiency; when simultaneously determining dozens or even hundreds of analytes, since the method of the present invention automatically screens characteristic ions by digital calculation, compared with the manual screening method that needs to screen one compound by one, the method of the present invention can perform batch screening simultaneously, greatly saving labor and time costs. Description of the Drawings
[0032] Figure 1 It is a schematic flowchart of the preferred method for quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method of Embodiment 1 of the present invention;
[0033] Figure 2 It is the full-scan chromatogram of isobutyramide in Embodiment 1 of the present invention;
[0034] Figure 3 It is the full-scan mass spectrum of isobutyramide in Embodiment 1 of the present invention;
[0035] Figure 4 It is the chromatogram of isobutyramide under different candidate ions in Embodiment 1 of the present invention;
[0036] Figure 5 It is the full-scan mass spectrum of N-butyrylpyrrolidine in Embodiment 2 of the present invention;
[0037] Figure 6 It is the full-scan mass spectrum of N-isovalerylpyrrolidine in Embodiment 2 of the present invention;
[0038] Figure 7 Taking solanone as an example in Embodiment 3 of the present invention, it is the chromatogram of the tobacco matrix spiked solution under 9 preferred candidate ions;
[0039] Figure 8 It is the chromatogram of the tobacco matrix sample analyzed by GC-MS according to the selection results in Embodiment 1 in Experimental Example 1 of the present invention;
[0040] Figure 9 It is the chromatogram of the tobacco matrix sample analyzed by GC-MS with the ions selected according to the conventional method in Experimental Example 1 of the present invention. Detailed Embodiments
[0041] The preferred method for quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method of the present invention is a pioneering invention. When screening the characteristic ions of the analyte, the present invention not only bases on the mass spectrometry fragmentation mechanism of the analyte itself, but also avoids the mutual interference between structurally similar analytes and the sample matrix interference during the simultaneous detection of multiple target substances. The selected characteristic ions take into account both specificity and sensitivity; the present invention digitalizes, standardizes, and processes the characteristic ion screening process of the analyte. Compared with the traditional method, it greatly reduces the dependence on the experience of chromatographic analysts, and at the same time, there is no need to repeatedly test and verify the specificity and sensitivity of the selected ions, improving the work efficiency.
[0042] The technical solution of the present invention will be further described below in conjunction with specific embodiments.
[0043] I. The specific embodiments of the preferred method for quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method of the present invention are as follows:
[0044] Example 1
[0045] The preferred method for quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method of this example is as Figure 1 shown, and specifically includes the following steps:
[0046] (1) Prepare a standard solution of isobutyramide with a concentration of 10 ppm, and use a gas chromatography-mass spectrometer to collect the mass spectrometry information of isobutyramide to obtain the full-scan chromatogram and full-scan mass spectrum of isobutyramide. The results are as Figure 2-3 shown; the scanning mode of the mass spectrometry is the full-scan mode, and the mass spectrometry scanning range is 30 - 700 amu; it can be seen from Figure 2 that under the chromatographic conditions adopted in this step, the retention time of isobutyramide is 21.3 min;
[0047] (2) According to the full-scan mass spectrum of isobutyramide ( Figure 3 ), convert the format of the full-scan mass spectrum of isobutyramide into digital mass spectrometry information to obtain the fragment ion information of isobutyramide, including the mass-to-charge ratio m / z, response intensity, and relative abundance of the fragment ions; the fragment ion information of isobutyramide is shown in Table 1; then select candidate ions from the fragment ions of isobutyramide;
[0048] Table 1 Fragment ion information of isobutyramide
[0049] Sequence number of fragment ions Mass-to-charge ratio m / z Response intensity Relative abundance (%) 1 30 6.1E2 1.7 2 31 2.8E2 0.8 3 32 1.0E3 2.9 4 37 1.2E3 3.4 5 38 2.7E3 7.7 6 39 8.1E3 23.1 7 40 2.8E3 8.0 8 41 1.5E4 42.9 9 42 5.1E3 14.6 10 43 2.2E4 62.9 11 44 3.5E4 100.0 12 45 2.2E3 6.3 13 46 3.9E3 11.1 14 52 4.8E2 1.4 15 53 6.2E2 1.8 16 54 8.6E2 2.5 17 55 3.4E3 9.7 18 56 8.2E2 2.3 19 58 9.0E2 2.6 20 59 8.5E3 24.3 21 69 9.1E2 2.6 22 70 8.8E2 2.5 23 71 2.5E3 7.1 24 72 1.5E4 42.9 25 73 9.8E2 2.8 26 86 1.3E3 3.7 27 87 5.6E3 16.0
[0050] The method for selecting candidate ions is as follows:
[0051] S1. Set the relative abundance threshold to 5% and the mass-to-charge ratio (m / z) threshold to 50. Define the fragment ions with relative abundance not less than the relative abundance threshold and mass-to-charge ratio not less than the mass-to-charge ratio threshold among all the fragment ions of isobutyramide as the primary selected ions;
[0052] S2. Select the fragment ion with the largest relative abundance among all the primary selected ions as the candidate ion, and then select the alternative ions from all the primary selected ions; The alternative ions refer to the fragment ions that meet the following conditions: If the difference between the mass-to-charge ratio of a certain fragment ion and the mass-to-charge ratio of the candidate ion is less than -6 or greater than 6, then this fragment ion is an alternative ion;
[0053] S3. Use the alternative ions obtained in step S2 as the new primary selected ions, repeat step S2, and obtain the new candidate ion and alternative ions;
[0054] S4. Repeat step S3 until all the candidate ions are selected;
[0055] List the mass-to-charge ratio (m / z), response intensity, and relative abundance of all the selected candidate ions in Table 2;
[0056] Table 2 Mass-to-charge ratio (m / z), response intensity, and relative abundance of all candidate ions
[0057] Sequence number Mass-to-charge ratio m / z Response intensity Relative abundance % 1 59 8.5E3 24.3 2 72 1.5E4 42.9 3 87 5.6E3 16.0
[0058] (3) Use each candidate ion as the mass spectrometry detection ion, and perform GC-MS analysis on the isobutyramide standard solution and the flue gas matrix spiked solution (the concentration of isobutyramide added to the flue gas matrix is 10 ppm) respectively to obtain the isobutyramide chromatograms under different candidate ions. The results are as Figure 4 shown;
[0059] From Figure 4 it can be seen that when using the candidate ion with a mass-to-charge ratio of 87 or the candidate ion with a mass-to-charge ratio of 59 as the mass spectrometry detection ion, the chromatographic peaks and impurity peaks of isobutyramide obtained by GC-MS analysis of the isobutyramide standard solution and the flue gas matrix spiked solution can be completely separated without affecting the determination, that is, there are no interference peaks in the isobutyramide chromatogram. Therefore, these two candidate ions are the characteristic ions of isobutyramide; When using the candidate ion with a mass-to-charge ratio of 72 as the mass spectrometry detection ion, the chromatographic peaks and impurity peaks of isobutyramide obtained by GC-MS analysis of the flue gas matrix spiked solution cannot be completely separated, that is, there are interference peaks in the isobutyramide chromatogram, which affects the accuracy of the determination result. Therefore, the candidate ion with a mass-to-charge ratio of 72 is a non-characteristic ion of isobutyramide;
[0060] In addition, when the candidate ion with a mass-to-charge ratio of 59 was used as the mass spectrometry detection ion, the chromatographic peak response intensity of isobutyramide obtained by GC-MS analysis of the isobutyramide standard solution and the flue gas matrix spiked solution was relatively large. Therefore, the candidate ion with a mass-to-charge ratio of 59 was used as the quantitative ion of isobutyramide, and the candidate ion with a mass-to-charge ratio of 87 was used as the qualitative ion of isobutyramide.
[0061] Example 2
[0062] In the method for analyzing by selected ion monitoring mode of gas chromatography-mass spectrometry in this example, the preferred methods for quantitative ions and qualitative ions specifically include the following steps:
[0063] (1) Prepare a standard solution containing N-butyrylpyrrolidine and N-isovalerylpyrrolidine. The concentrations of N-butyrylpyrrolidine and N-isovalerylpyrrolidine in the standard solution are both 10 ppm. Use a gas chromatography-mass spectrometer to collect mass spectrometry information of N-butyrylpyrrolidine and N-isovalerylpyrrolidine, and obtain the full-scan chromatogram and full-scan mass spectrum of N-butyrylpyrrolidine and N-isovalerylpyrrolidine. The full-scan mass spectra of N-butyrylpyrrolidine and N-isovalerylpyrrolidine are as Figure 5-6 shown; the scanning mode of the mass spectrometry is the full-scan mode, and the mass spectrometry scanning range is 30 - 700 amu; under the chromatographic conditions used in this step, the retention times of N-butyrylpyrrolidine and N-isovalerylpyrrolidine are 23.82 min and 23.88 min respectively;
[0064] (2) According to the full-scan mass spectra of N-butyrylpyrrolidine and N-isovalerylpyrrolidine, respectively obtain the fragment ion information of N-butyrylpyrrolidine and N-isovalerylpyrrolidine, including the mass-to-charge ratio m / z, response intensity, and relative abundance of the fragment ions; then select the candidate ions of N-butyrylpyrrolidine and N-isovalerylpyrrolidine from the fragment ions of N-butyrylpyrrolidine and N-isovalerylpyrrolidine respectively;
[0065] The method for selecting candidate ions is as follows:
[0066] S1, set the relative abundance threshold to 5%, and the mass-to-charge ratio (m / z) threshold to 50. Define the fragment ions with a relative abundance not less than the relative abundance threshold and a mass-to-charge ratio not less than the mass-to-charge ratio threshold among all the fragment ions of the analyte (N-butyrylpyrrolidine, N-isovalerylpyrrolidine) as the primary selected ions; the mass-to-charge ratio m / z, response intensity, and relative abundance of all the primary selected ions corresponding to N-butyrylpyrrolidine and N-isovalerylpyrrolidine are shown in Table 3;
[0067] Table 3 Information of primary selected ions corresponding to N-butyrylpyrrolidine and N-isovalerylpyrrolidine
[0068]
[0069]
[0070] S2. Select the fragment ion with the largest relative abundance from all the initially selected ions as the candidate ion, and then select alternative ions from all the initially selected ions. An alternative ion refers to a fragment ion that meets the following conditions: If the difference between the mass-to-charge ratio of a certain fragment ion and the mass-to-charge ratio of the candidate ion is less than -6 or greater than 6, then this fragment ion is an alternative ion (set according to the smallest fragment in mass spectrometry fragmentation being -CH2-; if the difference in the mass-to-charge ratio between a fragment ion and the candidate ion is within the range of -6 to 6, this fragment ion is obtained from the mass spectrometry fragmentation of non-candidate ions).
[0071] S3. Use the alternative ions obtained in step S2 as the new initially selected ions, and repeat step S2 to obtain new candidate ions and alternative ions.
[0072] S4. Repeat step S3 until all candidate ions are selected.
[0073] The mass-to-charge ratio m / z, response intensity, and relative abundance of all candidate ions corresponding to N-butyrylpyrrolidine and N-isovalerylpyrrolidine are shown in Table 4.
[0074] Table 4 Information of all candidate ions corresponding to N-butyrylpyrrolidine and N-isovalerylpyrrolidine
[0075]
[0076] (3) Since the retention times of N-butyrylpyrrolidine and N-isovalerylpyrrolidine are 23.82 min and 23.88 min respectively; set the retention time threshold to 0.1 min, and the difference in the retention times of N-butyrylpyrrolidine and N-isovalerylpyrrolidine is less than the set retention time threshold. Therefore, eliminate all non-target ions from all candidate ions corresponding to N-butyrylpyrrolidine and N-isovalerylpyrrolidine to obtain the preferred candidate ions. A non-target ion refers to a candidate ion that meets the following conditions: If the difference in the retention times of analyte A and analyte B is less than the retention time threshold, and the mass-to-charge ratio of candidate ion C corresponding to analyte A is the same as the mass-to-charge ratio of the initially selected ion D corresponding to analyte B, then candidate ion C is a non-target ion of analyte A; similarly, if the mass-to-charge ratio of candidate ion E corresponding to analyte B is the same as the mass-to-charge ratio of the initially selected ion F corresponding to analyte A, then candidate ion E is a non-target ion of analyte B.
[0077] As can be seen from Table 3-4, among all the candidate ions corresponding to N-butyrylpyrrolidine and N-isovalerylpyrrolidine, the candidate ions with mass-to-charge ratios of 55, 70, 85, 98, and 113 are non-target ions; the candidate ions with mass-to-charge ratios of 126 and 141 are the preferred candidate ions corresponding to N-butyrylpyrrolidine, and the candidate ions with mass-to-charge ratios of 140 and 155 are the preferred candidate ions corresponding to N-isovalerylpyrrolidine;
[0078] (4) Using each of the preferred candidate ions as the mass spectrometry detection ions, GC-MS analysis was performed on the standard solutions and flue gas matrix spiked solutions containing N-butyrylpyrrolidine and N-isovalerylpyrrolidine (the concentrations of N-butyrylpyrrolidine and N-isovalerylpyrrolidine in the flue gas matrix spiked solutions were both 10 ppm), and the chromatograms of N-butyrylpyrrolidine and N-isovalerylpyrrolidine under different preferred candidate ions were obtained;
[0079] From the test results, when using the preferred candidate ions with mass-to-charge ratios of 126 and 141 as the mass spectrometry detection ions, there were no interfering peaks in the chromatograms of N-butyrylpyrrolidine obtained by GC-MS analysis of the standard solutions and spiked solutions containing N-butyrylpyrrolidine and N-isovalerylpyrrolidine. Therefore, these two preferred candidate ions are the characteristic ions of N-butyrylpyrrolidine. And when using the preferred candidate ion with a mass-to-charge ratio of 141 as the mass spectrometry detection ion, the chromatographic peak response intensity of N-butyrylpyrrolidine obtained by GC-MS analysis of the standard solutions and spiked solutions containing N-butyrylpyrrolidine and N-isovalerylpyrrolidine was the largest. Therefore, the preferred candidate ion with a mass-to-charge ratio of 141 was used as the quantitative ion of N-butyrylpyrrolidine, and the candidate ion with a mass-to-charge ratio of 126 was used as the qualitative ion of N-butyrylpyrrolidine.
[0080] When using the preferred candidate ions with mass-to-charge ratios of 140 and 155 as the mass spectrometry detection ions, there were no interfering peaks in the chromatograms of N-isovalerylpyrrolidine obtained by GC-MS analysis of the standard solutions and spiked solutions containing N-butyrylpyrrolidine and N-isovalerylpyrrolidine. Therefore, these two preferred candidate ions are the characteristic ions of N-isovalerylpyrrolidine. And when using the preferred candidate ion with a mass-to-charge ratio of 155 as the mass spectrometry detection ion, the chromatographic peak response intensity of N-isovalerylpyrrolidine obtained by GC-MS analysis of the standard solutions and spiked solutions containing N-butyrylpyrrolidine and N-isovalerylpyrrolidine was the largest. Therefore, the preferred candidate ion with a mass-to-charge ratio of 155 was used as the quantitative ion of N-isovalerylpyrrolidine, and the candidate ion with a mass-to-charge ratio of 140 was used as the qualitative ion of N-isovalerylpyrrolidine.
[0081] Example 3
[0082] In the method for analyzing the selected ion monitoring mode of gas chromatography - mass spectrometry in this embodiment, the preferred method for quantitative ions and qualitative ions specifically includes the following steps:
[0083] (1) Prepare a standard solution of 36 flavor components, and the concentration of each flavor component in the standard solution is 10 ppm. Use GC - MS to collect mass spectrometry information of 36 flavor components to obtain a full - scan chromatogram and a full - scan mass spectrum. The scanning mode of the mass spectrometry is the full - scan mode, and the mass spectrometry scanning range is 30 - 700 amu; Under the chromatographic conditions used in this step, the 36 flavor components and their corresponding retention times are shown in Table 5;
[0084] (2) According to the full - scan mass spectra of 36 flavor components, convert the format of the full - scan mass spectra of 36 flavor components into digital mass spectrometry information to obtain the fragment ion information of 36 flavor components, including the mass - to - charge ratio m / z, response intensity, and relative abundance of the fragment ions; Then, select candidate ions for each flavor component from the fragment ions of 36 flavor components respectively;
[0085] The method for selecting candidate ions is as follows:
[0086] S1, set the relative abundance threshold to 5% and the mass - to - charge ratio (m / z) threshold to 50. Define the fragment ions in all fragment ions of the analyte (36 flavor components) with a relative abundance not less than the relative abundance threshold and a mass - to - charge ratio not less than the mass - to - charge ratio threshold as primary selected ions;
[0087] S2, select the fragment ion with the largest relative abundance from all primary selected ions as the candidate ion, and then select alternative ions from all primary selected ions; An alternative ion refers to a fragment ion that meets the following conditions: If the difference between the mass - to - charge ratio of a certain fragment ion and the mass - to - charge ratio of the candidate ion is less than - 6 or greater than 6, then this fragment ion is an alternative ion (set according to the smallest fragment of mass spectrometry fragmentation being - CH2 -; If the difference in mass - to - charge ratio between a certain fragment ion and the candidate ion is within the range of - 6 - 6, this fragment ion is obtained from the fragmentation of non - candidate ions);
[0088] S3, use the alternative ions obtained in step S2 as the new primary selected ions, and repeat step S2 to obtain new candidate ions and alternative ions;
[0089] S4, repeat step S3 until all candidate ions are selected;
[0090] The mass - to - charge ratio m / z, response intensity, and relative abundance of all candidate ions corresponding to 36 flavor components are shown in Table 5;
[0091] Table 5 Candidate ion information of 36 flavor components
[0092]
[0093]
[0094]
[0095]
[0096]
[0097] Note: The numbers in bold and italic in Table 5 represent the information of non-target ions.
[0098] (3) Eliminate all non-target ions from the candidate ions to obtain the preferred candidate ions. Non-target ions refer to candidate ions that meet the following conditions: If the difference in retention times between analyte A and analyte B is less than the retention time threshold, and the mass-to-charge ratio of candidate ion C corresponding to analyte A is the same as the mass-to-charge ratio of the primary selected ion D corresponding to analyte B, then candidate ion C is a non-target ion of analyte A; similarly, if the mass-to-charge ratio of candidate ion E corresponding to analyte B is the same as the mass-to-charge ratio of the primary selected ion F corresponding to analyte A, then candidate ion E is a non-target ion of analyte B; in this embodiment, the retention time threshold is set to 0.2 min; the non-target ions of 36 flavor components are the ions corresponding to the numbers in bold and italic in Table 5.
[0099] (4) Use each of the preferred candidate ions as the mass spectrometry detection ions, and perform GC-MS analysis on the standard solution containing 36 flavor components and the tobacco matrix spiked solution (the concentration of 36 flavor components in the flue gas matrix spiked solution is 10 ppm) respectively to obtain the chromatograms of 36 flavor components under different preferred candidate ions; when there are no interfering peaks in the chromatograms of the analyte obtained by GC-MS analysis of the analyte standard solution and the sample matrix spiked solution, then this candidate ion is a characteristic ion.
[0100] Taking solanone as an example, the chromatograms of the tobacco matrix spiked solution under 9 preferred candidate ions are shown in Figure 7 . Among them, the chromatograms under the ions with mass-to-charge ratios of 136, 194, and 151 have no interfering peaks and are the characteristic ions of solanone. Select the ion with a mass-to-charge ratio of 136, which has the largest chromatographic response intensity among the characteristic ions, as the quantitative ion, and the characteristic ion with the second largest chromatographic response intensity as the qualitative ion.
[0101] In this embodiment, the quantitative and qualitative ion results of 36 flavor components in the tobacco matrix are shown in Table 6.
[0102] Table 6 Quantitative and Qualitative Ion Information of 36 Flavor Components
[0103]
[0104]
[0105] II. The specific embodiments of the preferred system for quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method of the present invention are as follows:
[0106] The preferred system for quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method of this embodiment includes a spectrum digitization module, a candidate ion selection module, a non-target ion elimination module, and a characteristic ion confirmation module; the spectrum digitization module is used to convert the full-scan mass spectrum format of the analyte into digital mass spectrometry information; the candidate ion selection module is used to select candidate ions from all the fragment ions of the analyte; the non-target ion elimination module is aimed at avoiding the mutual interference between analytes with similar structures. When there are two or more analytes, after obtaining the candidate ions, all non-target ions are eliminated from the candidate ions to obtain the preferred candidate ions; the characteristic ion confirmation module is used to verify that the candidate ions are not interfered by the sample matrix through the sample matrix spike addition method, and then confirm the candidate ions as the characteristic ions of the analyte, and finally select quantitative ions and qualitative ions from the characteristic ions.
[0107] Experimental Example 1
[0108] Taking the detection of isobutyramide in tobacco matrix as an example, the tobacco matrix sample was analyzed by GC-MS using the method of the present invention and the conventional method. Specifically, according to the selection results in Example 1, the fragment ion with a mass-to-charge ratio of 59 was used as the quantitative ion of isobutyramide, and the fragment ion with a mass-to-charge ratio of 87 was used as the qualitative ion of isobutyramide. The tobacco matrix sample was analyzed by GC-MS to obtain the chromatograms of the tobacco sample under different detection ions. The results are as Figure 8 shown; at the same time, according to the conventional method, the fragment ion with a larger response intensity was selected as the characteristic ion. The fragment ion with a mass-to-charge ratio of 44 was used as the quantitative ion of isobutyramide, and the fragment ion with a mass-to-charge ratio of 72 was used as the qualitative ion of isobutyramide. The tobacco matrix sample was analyzed by GC-MS to obtain the chromatograms of the tobacco sample under different detection ions. The results are as Figure 9 shown. Figure 8 and Figure 9 The abscissa in represents time, with the unit of min, and the ordinate represents intensity.
[0109] It can be seen from Figure 8 that there are no chromatographic peaks in the chromatograms of the tobacco sample at the mass-to-charge ratios of 59 and 87 ions, and it is judged that isobutyramide is not detected in this sample. It can be seen from Figure 9It can be seen that there are chromatographic peaks in the chromatogram of the tobacco sample at the ions with mass-to-charge ratios of 44 and 72, and it is judged that isobutylamide is detected in the sample. This is because the ions with mass-to-charge ratios of 44 and 72 are non-specific ions. When using the ions with mass-to-charge ratios of 44 and 72 as the mass spectrometry detection ions, matrix interference exists, resulting in a false positive determination result.
[0110] Experimental Example 2
[0111] In this experimental example, taking the detection of isobutylamide in tobacco matrix as an example, the method of the present invention and the conventional method were used to perform GC-MS analysis on the blank tobacco matrix spiked solution to determine the sensitivity of different methods. Specifically, according to the selection results in Example 1, the fragment ion with a mass-to-charge ratio of 59 was used as the quantitative ion of isobutylamide, and the fragment ion with a mass-to-charge ratio of 87 was used as the qualitative ion of isobutylamide. GC-MS analysis was performed on the blank tobacco matrix spiked solution (spiking concentration: 50 ng / mL) to obtain the chromatogram under different detection ions and the response intensity of the isobutylamide chromatographic peak. Taking 10 times the signal-to-noise ratio as the limit of quantification, the characterization results are shown in Table 7; at the same time, according to the conventional method, the fragment ion with a larger response intensity was selected as the characteristic ion, the fragment ion with a mass-to-charge ratio of 44 was used as the quantitative ion of isobutylamide, and the fragment ion with a mass-to-charge ratio of 72 was used as the qualitative ion of isobutylamide. GC-MS analysis was performed on the blank tobacco matrix spiked solution (spiking concentration: 50 ng / mL) to obtain the chromatogram under different detection ions and the response intensity of the isobutylamide chromatographic peak. Taking 10 times the signal-to-noise ratio as the limit of quantification, the characterization results are shown in Table 7.
[0112] Table 7 Comparison of the limits of quantification of isobutylamide by different detection methods
[0113] Example 1 Conventional method Quantitation limit ng / mL 32.8 66.9
[0114] As can be seen from Table 7, the sensitivity is higher when analyzing using the quantitative ions and qualitative ions determined by the present invention.
Claims
1. A method for optimizing quantitative ions and qualitative ions in a gas chromatography-mass spectrometry selected ion monitoring mode analysis method, characterized in that: The following steps are involved: (1) obtaining mass spectrum information of the analyte, wherein the mass spectrum information includes the mass-to-charge ratio, response intensity and relative abundance of fragment ions collected after the analyte is ionized; (2) selecting candidate ions from all fragment ions corresponding to the analyte; The candidate ions are selected as follows: S1, setting a relative abundance threshold and a mass-to-charge ratio threshold, defining the fragment ions whose relative abundance is not less than the relative abundance threshold and whose mass-to-charge ratio is not less than the mass-to-charge ratio threshold among all the fragment ions corresponding to the analyte as the primary selected ions; S2, selecting the fragment ion with the largest relative abundance from all the primary selected ions as the candidate ion, and then selecting the candidate ion from all the primary selected ions; the candidate ion refers to the fragment ion that meets the following conditions: if the difference between the mass-to-charge ratio of a fragment ion and the mass-to-charge ratio of the candidate ion is less than -6 or greater than 6, then the fragment ion is the candidate ion; S3, using the candidate ion obtained in step S2 as a new primary ion, repeating step S2 to obtain new candidate ions and candidate ions; S4, repeat step S3 until all candidate ions are selected; (3) Using each candidate ion as a mass spectrometry detection ion, GC-MS analysis is performed to obtain the chromatogram of the analyte under different candidate ions, and then the characteristic ions are determined. Finally, quantitative ions and qualitative ions are selected from the characteristic ions.
2. The method for optimizing quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method according to claim 1, characterized in that: When there are more than two analytes, after obtaining candidate ions, all non-target ions are eliminated from the candidate ions to obtain preferred candidate ions, and then the preferred candidate ions are used as mass spectrometry detection ions to perform GC-MS analysis on the analyte solution and the sample matrix spiked solution, respectively, and then the characteristic ions corresponding to each analyte are determined according to the method in step (3), and finally the quantitative ions and qualitative ions are selected from the characteristic ions; non-target ions refer to candidate ions that meet the following conditions: if the difference in retention time between analyte A and analyte B is less than the retention time threshold, and the mass-to-charge ratio of candidate ion C corresponding to analyte A is the same as the mass-to-charge ratio of candidate ion D corresponding to analyte B, then candidate ion C is a non-target ion of analyte A.
3. The method for optimizing quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method according to claim 2, characterized in that: The retention time threshold is 0.1 to 0.3 min.
4. The method for optimizing quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method according to any one of claims 1 to 3, characterized in that: In step (3), the objects of GC-MS analysis are the analyte solution and the sample matrix spiked solution; the method for determining the characteristic ion is as follows: if a candidate ion is used as the mass spectrometry detection ion, and there is no interfering peak in the chromatogram of the analyte obtained by GC-MS analysis of the analyte solution and the sample matrix spiked solution, then the candidate ion is the characteristic ion; the characteristic ions are no less than 2.
5. The method for optimizing quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method according to any one of claims 1 to 3, characterized in that: The relative abundance threshold is 1% to 10%; the mass-to-charge ratio threshold is 40 to (A×50%) m / z, where A is equal to the molecular weight of the analyte.
6. The method for optimizing quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method according to any one of claims 1 to 3, characterized in that: The selection principle of quantitative ions is as follows: if the chromatographic response intensity of the analyte corresponding to a characteristic ion is greater than the chromatographic response intensity of the analyte corresponding to other characteristic ions, then the characteristic ion is the quantitative ion of the analyte; the chromatographic response intensity of the analyte corresponding to the characteristic ion refers to the chromatographic response intensity of the analyte obtained by GC-MS analysis of the analyte solution and the sample matrix spiked solution when the characteristic ion is used as the mass spectrometry detection ion.
7. The method for selecting quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method according to any one of claims 1 to 3, characterized in that: In step (1), the mass spectrum information of the analyte is obtained by performing GC-MS analysis on a standard solution of the analyte.
8. The method for selecting quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method according to claim 7, characterized in that: The concentration of the analyte in the standard solution is 0.5 to 50 ppm.
9. The method for selecting quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method according to claim 7, characterized in that: In step (1), the mass spectrometry scanning range during the GC-MS analysis is 30 to 700 amu; and the mass spectrometry scanning mode used when the standard solution of the analyte is subjected to GC-MS analysis is a full scan mode.
10. A system for optimizing quantitative ions and qualitative ions in a gas chromatography-mass spectrometry selected ion monitoring mode analysis method, characterized in that: It comprises a processor and a memory, wherein the processor is used to execute instructions stored in the memory to implement the preferred method for quantitative ions and qualitative ions in the gas chromatography-mass spectrometry selected ion monitoring mode analysis method as described in any one of claims 1-9.