A method for calculating the molecular isotope abundances of Freon using a linear model

Abstract

The present invention discloses a method for calculating the molecular isotope abundances of Freons by a linear model, comprising the following steps: determining the types of ion fragments that can be formed by Freons during isotope analysis; selecting the ion fragments with strong ion signals among the ion fragments as the receiving ions for isotope abundance measurement; determining the number of isotopes and their mass numbers for each receiving ion; arranging and stratifying the isotopes of each receiving ion in ascending order of mass number, and measuring the isotope abundances of each receiving ion in the Freon sample; re-arranging the isotope abundances of each receiving ion according to the mass number levels in step 4; taking the number of carbon atoms as the abscissa and the isotope abundance as the ordinate, connecting the corresponding coordinate points into a line to obtain a graph of the change of fragment isotope abundance with the number of carbon atoms; and calculating the molecular isotope abundances of the same mass number levels in Freons by using a linear inference method. The analysis method of the present invention is simple and highly reliable.

Description

Technical Field

[0001] The present invention relates to the technical field of isotope analysis, and particularly to a method for calculating the molecular isotope abundance of Freon by a linear model. Background Art

[0002] Isotopes refer to different nuclides of the same element with the same number of protons but different numbers of neutrons. This definition of isotopes is limited to the same element and single nuclides, and this definition of isotopes can no longer meet the needs of the isotope field. For the sake of convenience, here the atomic substances composed of one nuclide are mutually called atomic isotopes, such as 14 N, 15 N, etc. The molecular substances composed of two or more nuclides are mutually called molecular isotopes, such as N 2 There are molecular isotopes 28 N 2 , 29 N 2 , 30 N 2 These three are mutually called nitrogen molecular isotopes; CF 4 There are molecular isotopes 88 CF 4 , 89 CF 4 These two are mutually called carbon tetrafluoride isotopes. The fragment ions composed of two or more nuclides that appear in the isotope analysis process are called fragment isotopes, such as CF 4 and C 6 F 14 The fragment isotopes that both appear in the isotope analysis process 69 CF 3 + , 70 CF 3 + .

[0003] Freon is a substance in which part or all of the hydrogen atoms in hydrocarbon substances are replaced by halogens such as fluorine, chlorine, and bromine. The Freon for which the present invention explores the isotope abundance analysis is a type of Freon in which all H in hydrocarbon substances is completely replaced by F, such as C 4 F 10 , C 5 F 12 , C 6 F 14 , C 7 F 16 , C 8 F 18 etc.

[0004] In isotope abundance analysis, it is necessary to find suitable ions to be received and collect the isotope ion intensity signals in order to measure the isotope abundance. The first ionization energy of carbon atoms is 1086.5 kJ / mol -1 , and the first ionization energy of fluorine atoms is 1681.0 kJ / mol -1 . The average bond energy of C-C is 347.3 kJ / mol -1 , and the average bond energy of C-F is 485.3 kJ / mol -1 . From these physical data, it can be seen that for C 4 F 10 , C 5 F 12 , C 6 F 14 , C 7 F 16 , C 8 F 18 and other such Freon molecules, after obtaining a certain amount of energy, C-C is preferentially broken rather than C-F, and it is easy to form fragment ions with fewer carbon atoms than those of the Freon molecule, and it is not easy to form molecular ions or fragment ions with the same number of carbon atoms as the Freon molecule. Or rather, the ion intensity of the ions formed with the same number of carbon atoms as the Freon is very weak and cannot be used for isotope abundance measurement, that is, the isotope abundance of C 4 F 10 , C 5 F 12 , C 6 F 14 , C 7 F 16 , C 8 F 18 and other such Freon molecules cannot be measured directly. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for calculating the molecular isotope abundance of Freon by a linear model in view of the technical defects existing in the prior art.

[0006] The technical solution adopted to achieve the purpose of the present invention is as follows:

[0007] A method for calculating the molecular isotope abundance of Freon by a linear model, where the Freon is Freon containing only carbon and fluorine, and includes the following steps:

[0008] Step 1, determine the types of ion fragments that can be formed by Freon during isotope analysis;

[0009] Step 2, select the ion fragments with strong ion signals among the ion fragments as the received ions for isotope abundance measurement;

[0010] Step 3, determining the number of isotopes and the mass number of each received ion;

[0011] Step 4, arranging and layering the isotopes of each received ion according to mass number from small to large, which can be divided into a minimum mass number layer, a second minimum mass number layer, a third minimum mass number layer, ..., an Nth minimum mass number layer, wherein the isotope mass number of each received ion with the smallest mass number is located in the minimum mass number layer, and the second smallest is located in the second minimum mass number layer, and so on;

[0012] Step 5, determining the isotopic abundance of each received ion in the Freon sample;

[0013] Step 6, re-arrange the isotopic abundance of each received ion according to the mass number level in step 4;

[0014] Step 7, using the number of carbon atoms as the horizontal coordinate and the isotope abundance as the vertical coordinate, connecting the corresponding coordinate points into a line to obtain a graph showing the change of fragment isotope abundance with the number of carbon atoms;

[0015] Step 8, use the linear inference method to calculate the molecular isotope abundance of the same mass number level in Freon.

[0016] In the above technical solution, in step 8, the linear inference method includes two methods: Excel image processing and establishing a linear equation.

[0017] In the above technical solution, the Excel image processing method is as follows:

[0018] In an Excel document, a straight line fitting is performed on the graph of isotope abundance varying with the number of carbon atoms for each minimum mass number layer of the received ions in the Freon sample to obtain a straight line of isotope abundance varying with the number of carbon atoms. The straight line segment is further extended to obtain an abundance value corresponding to the carbon number in Freon with the intersection of the straight line of isotope abundance varying with the number of carbon atoms as the center, and the carbon number is read as the abundance value corresponding to the carbon number in Freon, that is, the abundance corresponding to the minimum mass number in the Freon isotopes; and by analogy, the abundance corresponding to the second smallest mass number in the Freon isotopes is obtained, and so on, the abundance corresponding to the Nth smallest mass number layer is obtained.

[0019] In the above technical solution, the intersection of the straight line where the carbon number is the carbon number in Freon and the isotope abundance changes with the number of carbon atoms is taken as the center, local amplification is performed, and then the carbon atom number is read out as the abundance value corresponding to the carbon number in Freon.

[0020] In the above technical solution, the method of establishing the linear equation is as follows:

[0021] Step s1, design a linear equation according to the linear law of the change of isotope abundance of the same mass number level of the received ions with the number of carbon atoms:

[0022] Formula y n = y 1 + k(n - 1) is the calculation formula for the isotope abundance corresponding to the minimum mass number and the isotope abundance corresponding to the second smallest mass number of the molecular isotope of Freon with n carbon atoms;

[0023] Formula y n = y 1 + k(n - 2) is the calculation formula for the isotope abundance corresponding to the third smallest mass number;

[0024] In the above formulas, y is the isotope abundance of the received ions, n is the number of carbon atoms, and k is the slope of the straight line;

[0025] Step s2, calculate the slope of the linear equation:

[0026] Calculation of the slope of the straight line equation for the isotope abundance corresponding to the minimum mass number and the isotope abundance corresponding to the second smallest mass number: Taking the abundance point corresponding to C 1 as the reference, a straight line formed by the corresponding points of C 1 and C 2 , with a slope k 12 ,C 1 and a straight line formed by the corresponding points of C 3 , with a slope k 13 ; The average value k of k 12 and k 13 is the slope of a straight line passing through point 1 and between the straight line of point 1 and point 2 and the straight line of point 1 and point 3, that is, the slope of the linear equation for the isotope abundance corresponding to the minimum mass number and the isotope abundance corresponding to the second smallest mass number of the C 6 F 14 molecular isotope, and the calculation formulas for k 12 , k 13 and k are:

[0027]

[0028]

[0029]

[0030] Calculation of the slope of the straight line equation for the abundance corresponding to the third smallest mass number: Calculate the slope of the straight line of C 2 ~C 3 , and the calculation formula is:

[0031]

[0032] Step s3, calculate the molecular isotope of Freon from the linear equation in step s1 and the slope of the linear equation in step s2.

[0033] In the above technical solution, the Freon is C 4 F 10 、C 5 F 12 、C 6 F 14 、C 7 F 16 or C 8 F 18 .

[0034] In the above technical solution, when the Freon is C 6 F 14 , in step 2, the ion fragments CF 3 + 、C 2 F 5 + 、C 3 F 7 + are used as the received ions for isotope abundance measurement.

[0035] In the above technical solution, when the Freon is C 6 F 14 , in step 4, the mass numbers 69 of CF 3 + 、119 of C 2 F 5 + 、169 of C 3 F 7 + belong to the layer of the smallest mass numbers;

[0036] The mass numbers 70 of CF 3 + 、120 of C 2 F 5 + 、170 of C 3 F 7 + belong to the layer of the second smallest mass numbers;

[0037] C 2 F 5 + The mass number 121、171 of C 3 F 7 + belong to the layer of the third smallest mass numbers.

[0038] In the above technical solution, when the Freon is C 6 F 14 , in step 8, CF 3+ , C 2 F 5 + , C 3 F 7 + Perform a linear fit on the graph of the isotope abundances of the three fragment ions at the minimum mass number level as a function of the number of carbon atoms, and extend this line segment in the direction of C 6 , and read out the abundance value corresponding to 6 carbon atoms, which is the abundance corresponding to the minimum mass number 338 in the C 6 F 14 isotope;

[0039] For CF 3 + , C 2 F 5 + , C 3 F 7 + Process the graph of the isotope abundances of the three fragment ions at the second smallest mass number level as a function of the number of carbon atoms, and read out the abundance value corresponding to 6 carbon atoms, which is the abundance corresponding to the second smallest mass number 339 in the C 6 F 14 isotope;

[0040] For CF 3 + , C 2 F 5 + , C 3 F 7 + Process the graph of the isotope abundances of the three fragment ions at the third smallest mass number level as a function of the number of carbon atoms, and directly read out the abundance value corresponding to 6 carbon atoms, which is the abundance corresponding to the third smallest mass number 340 of the C 6 F 14 molecule.

[0041] In the above technical solution, when the freon is C 6 F 14 , in step 8, taking the abundance data of the minimum mass number of each fragment ion isotope of C 6 F 14 as an example, calculate the straight line slope k, and calculate the isotope abundance corresponding to the minimum mass number 338 of the C n = y 1 + k(n - 1); 6 F 14 isotope;

[0042] Taking C 6 F 14Calculate the slope k of the straight line from the abundance data of the second smallest mass number of the isotopes of each fragment ion. From the formula y n = y 1 + k(n - 1), calculate the abundance of the second smallest mass number 339 of the C 6 F 14 molecular isotope;

[0043] C 6 F 14 The slope of the straight line of the third smallest mass number of the isotopes of each fragment ion is directly obtained from two points of C 2 and C 3 . From the formula y n = y 1 + k(n - 2), calculate the abundance value of the third smallest mass number 340 of the C 6 F 14 molecular isotope.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] 1. Taking the isotope analysis of C 6 F 14 as an example, by finding the relationship between the isotope abundance of the C 6 F 14 fragment ions and the change in the number of carbon atoms, revealing the law therein, inferring the molecular isotope abundance of chlorofluorocarbons from the fragment isotope abundance of chlorofluorocarbons through this change law, and establishing a linear inference method to indirectly measure the molecular isotope abundance of chlorofluorocarbons, so as to solve the problem of measuring the isotope abundance of chlorofluorocarbon molecules such as C 4 F 10 , C 5 F 12 , C 6 F 14 , C 7 F 16 , C 8 F 18 etc.

[0046] 2. Both the "Excel image processing" and "establishing a linear equation" methods are reliable, and both methods meet the requirements of the daily analysis of chlorofluorocarbon molecule isotopes. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a graph showing the change of the abundance of the smallest mass number of three fragments of the 1 # sample in Example 1 with the number of carbon atoms;

[0048] Figure 2 is a graph showing the change of the abundance of the second smallest mass number of three fragments of the 1 # sample in Example 1 with the number of carbon atoms;

[0049] Figure 3 It is 1 in Example 1 # Graph showing the variation of the abundance of the third smallest mass number of the three fragments of the sample with the number of carbon atoms;

[0050] Figure 4 It is 2 in Example 1 # Graph showing the variation of the abundance of the smallest mass number of the three fragments of the sample with the number of carbon atoms;

[0051] Figure 5 It is 2 in Example 1 # Graph showing the variation of the abundance of the second smallest mass number of the three fragments of the sample with the number of carbon atoms;

[0052] Figure 6 It is 2 in Example 1 # Graph showing the variation of the abundance of the third smallest mass number of the three fragments of the sample with the number of carbon atoms;

[0053] Figure 7 It is 3 in Example 1 # Graph showing the variation of the abundance of the smallest mass number of the three fragments of the sample with the number of carbon atoms;

[0054] Figure 8 It is 3 in Example 1 # Graph showing the variation of the abundance of the second smallest mass number of the three fragments of the sample with the number of carbon atoms;

[0055] Figure 9 It is 3 in Example 1 # Graph showing the variation of the abundance of the third smallest mass number of the three fragments of the sample with the number of carbon atoms;

[0056] Figure 10 It is 4 in Example 1 # Graph showing the variation of the abundance of the smallest mass number of the three fragments of the sample with the number of carbon atoms;

[0057] Figure 11 It is 4 in Example 1 # Graph showing the variation of the abundance of the second smallest mass number of the three fragments of the sample with the number of carbon atoms;

[0058] Figure 12 It is 4 in Example 1 # Graph showing the variation of the abundance of the third smallest mass number of the three fragments of the sample with the number of carbon atoms;

[0059] Figure 13 It is 5 in Example 1 # Graph showing the variation of the abundance of the smallest mass number of the three fragments of the sample with the number of carbon atoms;

[0060] Figure 14 It is 5 in Example 1 # Graph showing the variation of the abundance of the second smallest mass number of the three fragments of the sample with the number of carbon atoms;

[0061] Figure 15 is the abundance variation diagram of the third smallest mass number of the three fragments of the sample in Example 1 with respect to the number of carbon atoms; # for the three fragments of the sample;

[0062] Figure 16 is the abundance variation diagram of the smallest mass number of the three fragments of the sample in Example 1 with respect to the number of carbon atoms; # for the three fragments of the sample;

[0063] Figure 17 is the abundance variation diagram of the second smallest mass number of the three fragments of the sample in Example 1 with respect to the number of carbon atoms; # for the three fragments of the sample;

[0064] Figure 18 is the abundance variation diagram of the third smallest mass number of the three fragments of the sample in Example 1 with respect to the number of carbon atoms; # for the three fragments of the sample;

[0065] Figure 19 is the extended diagram of the abundance of the smallest mass number of the sample in Example 1 with respect to the number of carbon atoms; # for the sample;

[0066] Figure 20 is the partially enlarged diagram of the abundance of the smallest mass number of the sample in Example 1 with respect to the number of carbon atoms; # for the sample;

[0067] Figure 21 is the extended diagram of the abundance of the second smallest mass number of the sample in Example 1 with respect to the number of carbon atoms; # for the sample;

[0068] Figure 22 is the partially enlarged diagram of the abundance of the second smallest mass number of the sample in Example 1 with respect to the number of carbon atoms; # for the sample;

[0069] Figure 23 is the extended diagram of the abundance of the third smallest mass number of the sample in Example 1 with respect to the number of carbon atoms; # for the sample;

[0070] Figure 24 is the partially enlarged diagram of the abundance of the second smallest mass number of the sample in Example 1 with respect to the number of carbon atoms; # for the sample;

[0071] Figure 25 is the isotope abundance marking point diagram corresponding to the number of carbon atoms in Example 1;

[0072] Figure 26 is the C in Example 2 6 F 14 is the variation and extended diagram of the abundance of the smallest mass number of the sample with respect to the number of carbon atoms;

[0073] Figure 27 is C in Example 2 6 F 14 Partial enlarged view of the abundance of the minimum mass number of the sample varying with the number of carbon atoms;

[0074] Figure 28 is C in Example 2 6 F 14 Graph of the abundance of the second smallest mass number of the sample varying with the number of carbon atoms and its extension;

[0075] Figure 29 is C in Example 2 6 F 14 Partial enlarged view of the abundance of the second smallest mass number of the sample varying with the number of carbon atoms;

[0076] Figure 30 is C in Example 2 6 F 14 Graph of the abundance of the third smallest mass number of the sample varying with the number of carbon atoms and its extension;

[0077] Figure 31 is C in Example 2 6 F 14 Partial enlarged view of the abundance of the second smallest mass number of the sample varying with the number of carbon atoms; Detailed implementation manners

[0078] The present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0079] Example 1

[0080] 1.1 C 6 F 14 Isotopic mass number

[0081] This example takes the isotopic analysis of C 6 F 14 as an example, and by revealing the fragment ions CF 6 F 14 of C 3 + 、C 2 F 5 + 、C 3 F 7 + the linear law that the fragment isotopic abundances of the same mass number level show a straight line with the number of carbon atoms, an indirect measurement method for the isotopic abundances of Freon molecules such as C 6 F 14 is established.

[0082] C has 12 C,13 Carbon has two natural isotopes with mass numbers 12 and 13 respectively. Fluorine has only one nuclide with a mass number of 19 and no isotopes. In the measurement of the isotope abundance of the fluoride of carbon, only carbon is considered and fluorine is not considered.

[0083] C 6 F 14 The molecule contains 6 carbons and 14 fluorines. It is a compound in which the 14 hydrogens in 6 H 14 are completely replaced by 14 fluorines. It is a molecular substance in the Freon category. It is a gas at room temperature and has a total of seven molecular isotopes. The 6 F 14 mass numbers of the seven isotopes are shown in Table 1.

[0084] Table 1 Mass numbers of the isotopes of 6 F 14 of carbon

[0085]

[0086] C 6 F 14 Among the seven isotopes of carbon

[0087] 1.2 Establish a linear model of the change of the fragment isotope abundance of 6 F 14 of carbon with the number of carbon atoms

[0088] Taking 6 F 14 as an example, reveal the variation rules of the fragment ion isotope abundance in 4 F 10 、 5 F 12 、 6 F 14 、 7 F 16 、 8 F 18 and other Freons with the change of the number of carbon atoms.

[0089] In the isotope analysis process of 6 F 14 of carbon, 6 F 14 can form CF 3 + 、 2 F 5 + 、 3 F 7 + 、4 F 9 + and C 5 F 11 + and many other kinds of ionic fragments. Among them, the ionic intensity signal of CF 3 + is the strongest, followed by C 2 F 5 + , and then C 3 F 7 + . The isotopic abundances of these three kinds of ions can all be accurately measured. C 4 F 9 + and C 5 F 11 + These two kinds of ions have very weak ionic intensity signals. If they are used as received ions, the errors of the measured isotopic abundances are relatively large, and it is not recommended to use them as received ions for isotopic abundance measurement.

[0090] C 6 F 14 The three fragment ions of 3 + C 2 F 5 + C 3 F 7 + The types and numbers of isotopes are different. CF 3 + has two isotopes with mass numbers of 69 and 70 respectively. C 2 F 5 + has three isotopes with mass numbers of 119, 120, and 121 respectively. C 3 F 7 + has four isotopes with mass numbers of 169, 170, 171, and 172 respectively. Arranging and stratifying the isotopes of the three fragment ions of C 6 F 14 in ascending order of mass number, they can be divided into the smallest mass number layer, the second smallest mass number layer, the third smallest mass number layer, and so on. The mass numbers of 69 of CF 3 + C 2 F 5 + C 3 F 7 + Arranging and stratifying the isotopes of the three fragment ions of C 3 + in ascending order of mass number, they can be divided into the smallest mass number layer, the second smallest mass number layer, the third smallest mass number layer, and so on. The mass number 69 of CF 2F 5 + Mass number 119, C 3 F 7 + Mass number 169, which is the smallest among their respective isotopes and belongs to the layer of the smallest mass number. CF 3 + The mass number of is 70, C 2 F 5 + Mass number 120, C 3 F 7 + Mass number 170, which is the second smallest among their respective isotopes and belongs to the layer of the second smallest mass number. CF 3 + There is no third mass number and no layer of the third smallest mass number; C 2 F 5 + Mass number 121, C 3 F 7 + Mass number 171 belongs to the layer of the third smallest mass number.

[0091] Six C 6 F 14 samples of CF 3 + 、C 2 F 5 + 、C 3 F 7 + The isotope abundances of three fragment ions were measured by a certain measurement method. Now, the mass numbers and their corresponding abundances of these three fragment ions are plotted in a table, as shown in Table 2.

[0092] Table 2 Mass numbers and abundance values of three fragment ion isotopes of six samples

[0093]

[0094] Re-arrange the isotope abundances of the three fragment ions of Sample 1 # in Table 2 according to the hierarchy of mass numbers. The abundance with the smallest mass number is arranged in the first row, the abundance with the second smallest mass number is arranged in the second row, and the abundance with the third smallest mass number is arranged in the third row. CF 3 + 、C 2 F 5 + 、C 3 F 7 + Respectively use C 1 、C 2 、C3 It is shown as in Table 3.

[0095] Table 3 1 # Table of the isotope abundances of the three fragment ions of the sample arranged in ascending order of mass number

[0096]

[0097]

[0098] According to 1 # Using the same treatment method for the sample, respectively for 2 # 、3 # 、4 # 、5 # 、6 # Re-arrange the fragment ion abundances of the samples, make tables, as shown in Tables 4 to 8. Draw the graph of the abundances of the corresponding fragment ion mass numbers changing with the number of carbon atoms, as Figures 4 to 18 shown.

[0099] Table 4 2 # Table of the isotope abundances of the three fragment ions of the sample arranged in ascending order of mass number

[0100]

[0101] Taking the number of carbon atoms as the abscissa and the abundance as the ordinate, plot the abundances of the minimum mass numbers of the three fragment ions of CF 3 + 、C 2 F 5 + 、C 3 F 7 + in Table 3, and connect the corresponding coordinate points into a line to obtain the graph of the fragment isotope abundances changing with the number of carbon atoms, as Figure 1 shown. Use the same method to plot the abundances of the second smallest mass number and the third smallest mass number of the three fragment ions of CF 3 + 、C 2 F 5 + 、C 3 F 7 + changing with the number of carbon atoms, as Figure 2 、 Figure 3 shown.

[0102] Table 5 3 # Table of the isotope abundances of the three fragment ions of the sample arranged in ascending order of mass number

[0103]

[0104] Table 6 4 # Table of the isotope abundances of the three fragment ions of the sample arranged in ascending order of mass number

[0105]

[0106] Table 7 5 # Table of the isotope abundances of the three fragment ions of the sample arranged in ascending order of mass number

[0107]

[0108]

[0109] Table 8 6 # Table of the isotope abundances of the three fragment ions of the sample arranged in ascending order of mass number

[0110]

[0111] From Figure 1 、 Figure 4 、 Figure 7 、 Figure 10 、 Figure 13 、 Figure 16 it can be seen that the three points in each figure are on a straight line, indicating that for samples 1 # ~6 # the isotope abundances of the smallest mass number of the three fragment ions CF 3 + 、C 2 F 5 + 、C 3 F 7 + show a good linear relationship with the number of carbon atoms. From Figure 2 、 Figure 5 、 Figure 8 、 Figure 11 、 Figure 14 、 Figure 17 it can be seen that the three points in each figure are on a straight line, indicating that for samples 1 # ~6 # the isotope abundances of the second smallest mass number of the three fragment ions CF 3 + 、C 2 F 5 + 、C 3 F 7 + also show a good linear relationship with the number of carbon atoms. Figure 3 、 Figure 6 、 Figure 9, Figure 12 , Figure 15 , Figure 18 Even if there are only two points on a straight line, it is also considered to have a good linear relationship.

[0112] By analyzing the variation law of the isotope abundances of different mass number levels of the three fragment ions CF 3 + , C 2 F 5 + , C 3 F 7 + in six Freon samples respectively with the change of the number of carbon atoms, it is concluded that for the same Freon sample, the isotope abundances of the CF 3 + , C 2 F 5 + , C 3 F 7 + fragment ions at the same mass number level show a good linear relationship with the number of carbon atoms. A linear model is established where the variation law of the isotope abundances of the C 6 F 14 fragment ions with the number of carbon atoms is a straight line.

[0113] 1.3 Establishing a linear extrapolation method for C 6 F 14 isotope abundances

[0114] Based on the law that the isotope abundances of the fragment ions of the same mass number level in Freon samples show a linear relationship with the number of carbon atoms as a straight line, the molecular isotope abundances of Freon at the same mass number level can be extrapolated by linear inference. The present invention designs two methods, "Excel image processing" and "establishing a linear equation", to infer the molecular isotope abundances of Freon. The following takes sample 1 # as an example for illustration.

[0115] 1.3.1 Method for inferring C 6 F 14 isotope abundances using the Excel image processing function

[0116] In the Excel document, plot the variation graphs of the isotope abundances of the three fragment ions CF # in sample 1 3 + , C 2 F 5 + , C 3 F 7 + at the minimum mass number level with the number of carbon atoms (Figure 1 ) Perform a linear fitting for the straight line and extend this straight line segment in the direction of C 6 , as shown in Figure 19 .

[0117] At the intersection point of the straight line where the carbon number is 6 and the isotope abundance changes with the number of carbon atoms in Figure 19 , perform a local magnification on Figure 19 to obtain a segment of the screenshot, as shown in Figure 20 .

[0118] Read directly from Figure 20 the abundance value 0.93226 corresponding to the carbon number of 6. The minimum mass number in the C 6 F 14 isotope is 338, which belongs to the same mass number level as the minimum mass levels of the three fragment ions of CF 3 + , C 2 F 5 + , C 3 F 7 + . Therefore, the abundance corresponding to the minimum mass number 338 in the C 6 F 14 isotope is 0.93226.

[0119] According to the same method, process the graph of the isotope abundance change with the number of carbon atoms for the second smallest mass number levels of the three fragment ions of CF # in the 1 3 + , C 2 F 5 + , C 3 F 7 + sample to obtain Figure 21 , Figure 22 .

[0120] Read directly from Figure 22 the abundance value 0.06622 corresponding to the carbon number of 6. The second smallest mass number in the C 6 F 14 isotope is 339, which belongs to the same mass number level as the second smallest mass number levels of the three fragment ions of CF 3 + , C 2 F 5 + , C 3 F 7 + . Therefore, the C 6 F 14The abundance corresponding to the second smallest mass number 339 in the isotope is 0.06622.

[0121] According to the same method, for 1 # the CF of the sample 3 + , C 2 F 5 + , C 3 F 7 + The graphs of the isotope abundances of the third smallest mass number levels of the three fragment ions of CF, C F, and C F versus the number of carbon atoms were processed to obtain Figure 23 , Figure 24 .

[0122] From Figure 24 the abundance value 0.00194 corresponding to 6 carbon atoms was directly read out. The third smallest mass number of the C F isotope is 340, which is the same as that of the third smallest mass number levels of the three fragment ions of CF, C F, and C F. Therefore, 6 F 14 the abundance corresponding to the third smallest mass number 340 of the C F molecule is 0.00194. 3 + , C 2 F 5 + , C 3 F 7 + belong to the same mass number level. Therefore, 6 F 14 the abundance corresponding to the third smallest mass number 340 of the C F molecule is 0.00194.

[0123] The abundances corresponding to the smallest mass number, the second smallest mass number, and the third smallest mass number of the obtained C F isotope were filled into the isotope and its abundance table of C F to obtain Table 9. 6 F 14 Table 9 Measurement Table of Isotopes and Their Abundance Values of C F 6 F 14 As can be seen from Table 9, the isotope abundance of the smallest mass number 338 in the C F isotope is the highest, with a value of 0.93226; the isotope abundance of the second smallest mass number 339 is the second highest, with a value of 0.06622; the isotope abundance of the third smallest mass number 340 is the third highest, with a value of 0.00194. From the trend of the abundance changes in Table 9, it can be seen that as the mass number increases, C

[0124] Table 9 Isotopes and Their Abundance Values of C F 6 F 14 F

[0125]

[0126] As can be seen from Table 9, the isotope abundance of the smallest mass number 338 in the C F isotope is the highest, with a value of 0.93226; the isotope abundance of the second smallest mass number 339 is the second highest, with a value of 0.06622; the isotope abundance of the third smallest mass number 340 is the third highest, with a value of 0.00194. From the trend of the abundance changes in Table 9, it can be seen that as the mass number increases, C 6 F 14 F 6 F 14The abundance of isotopes decreases exponentially. It can be inferred that the abundance of the isotope with a mass number of 341 should be less than 0.0001, and the abundances of isotopes with mass numbers of 342, 343, and 344 are even lower. From the perspective of practical applications, the abundances of isotopes with mass numbers 341, 342, 343, and 344 can be ignored, and only the abundances of the three isotopes with mass numbers 338, 339, and 340 need to be considered. Then Table 9 can be changed to Table 10, and Table 10 is C 6 F 14 Table of isotope abundance analysis results.

[0127] Table 10 Excel linear inference C 6 F 14 Table of isotope abundance results

[0128]

[0129]

[0130] As can be seen from Table 10, C 6 F 14 The sum of the abundances of each isotope of is 1.00042, which is very close to 1, and the overall abundance error is within ±0.05%. This indicates that the method of inferring the isotope abundances of C 6 F 14 molecules by Excel image processing in the present invention is accurate and reliable.

[0131] 1.3.2 Establish a linear equation to calculate C 6 F 14 Method for isotope abundance

[0132] 1.3.2.1 Establishment of a linear equation for isotope abundance calculation

[0133] According to the linear law of the isotope abundances of Freon fragment ions at the same mass number level changing with the number of carbon atoms, a linear equation can be designed, such as formula (1).

[0134] y = kx + b.........................(1)

[0135] Here, y is the isotope abundance, x is the number of carbon atoms, k is the slope of the straight line, and b is the intercept.

[0136] When the number of carbon atoms is 1, formula (1) becomes formula (2).

[0137] y 1 = k + b.........................(2)

[0138] When the number of carbon atoms is n, formula (1) becomes formula (3).

[0139] y n = kn + b.........................(3)

[0140] Equation (4) is obtained from Equation (2) and Equation (3).

[0141] y n - y 1 = k(n - 1)...................(4)

[0142] Equation (4) is transformed to obtain Equation (5).

[0143] y n = y 1 + k(n - 1)...................(5)

[0144] C 4 F 10 、C 5 F 12 、C 6 F 14 、C 7 F 16 、C 8 F 18 These Freon molecules such as C 3 + F can generally form fragment ions with 1, 2, or 3 carbon atoms. Among them, the fragment ion with 1 carbon atom, i.e., CF 3 + has the strongest signal and the most accurate measurement, and can be used as a reference point for inferring the molecular isotope abundance. Since CF

[0145] C 2 F 5 + has three mass numbers, for C 4 F 10 、C 5 F 12 、C 6 F 14 、C 7 F 16 、C 8 F 18 For calculating the abundance corresponding to the third smallest mass number of these Freon molecules such as C 2 F 5+ Start with the number of carbon atoms being 2 as the reference point. Thus, the calculation formula for the isotope abundance corresponding to the third smallest mass number changes from formula (5) to formula (6).

[0146] y n = y 2 + k(n - 2)...................(6)

[0147] 1.3.2.2 Calculation method for the slope k of the linear equation

[0148] 1.3.2.2.1 Calculation of the slope of the straight-line equation for the isotope abundance corresponding to the smallest mass number and the isotope abundance corresponding to the second smallest mass number

[0149] Mark three points with carbon atom numbers 1, 2, and 3 in the graph of the isotope abundance varying with the number of carbon atoms at the same mass number level (taking Figure 1 as an example), such as Figure 25 .

[0150] Taking the abundance point corresponding to C 1 as the reference, a straight line formed by the corresponding points of C 1 and C 2 , with slope k 12 ,C 1 and a straight line formed by the corresponding points of C 3 , with slope k 13 ; k 12 and k 13 The average value k of k 6 F 14 is the slope of a straight line passing through point 1 and between the straight line connecting point 1 and point 2 and the straight line connecting point 1 and point 3, which is the slope of the linear equation for the isotope abundance corresponding to the smallest mass number and the isotope abundance corresponding to the second smallest mass number of the C 12 molecule's isotope. k 13 The calculation formulas for k

[0151]

[0152]

[0153]

[0154] Accordingly, a record table for the slope of the linear equation of the isotope abundance corresponding to the smallest mass number and the isotope abundance corresponding to the second smallest mass number of C 6 F 14 can be designed, as shown in Table 11.

[0155] Table 11 C 6 F14 Table of the slope of the linear equation of the abundances of the minimum mass number and the second minimum mass number of the isotope

[0156]

[0157] According to the calculated slope k, calculate C according to formula (5). 6 F 14 The isotope abundances corresponding to the minimum mass number 338 and the second minimum mass number 339 of

[0158] 1.3.2.2.2 Calculation of the slope of the straight-line equation of the abundance corresponding to the third minimum mass number

[0159] For C 6 F 14 For the calculation of the slope of the abundance corresponding to the third minimum mass number of the C 2 ~C 3 The slope of the straight line, and the calculation formula is formula (10).

[0160]

[0161] C 6 F 14 The slope k of the abundance corresponding to the third minimum mass number of the C 23 The calculation results are shown in Table 12.

[0162] Table 12 Table of the slope of the linear equation of the abundance of the third minimum mass number of the C 6 F 14 isotope

[0163]

[0164] According to the calculated slope, calculate C according to formula (6). 6 F 14 The isotope abundance corresponding to the third minimum mass number 340 of 6 F 14 Calculation of the abundance of the C

[0165] Taking the abundance data of the minimum mass number of the fragment ions of the 1 6 F 14 sample of C # as an example to calculate the straight-line slope k, and the results are filled in Table 11 to obtain Table 13.

[0166] Table 13 Calculation of the straight-line slope k from the abundance data of the minimum mass number of the 1 # sample

[0167]

[0168] The slope k calculated according to Table 13 is -0.01119, and C is calculated from formula (5). 6 F 14 The isotope abundance corresponding to the minimum mass number 338 of the isotope, and its isotope abundance value is 0.93267.

[0169] Using the same method, calculate 1 # The abundance data of the second smallest mass number of each fragment ion of the sample is used to calculate the slope k of the straight line, and the results are filled in Table 11 to obtain Table 14.

[0170] Table 14 1 # The abundance data of the second smallest mass number of the isotope of the sample is used to calculate the slope k of the straight line

[0171]

[0172] The slope k calculated according to Table 14 is 0.01095, and C is calculated from formula (5). 6 F 14 The abundance of the second smallest mass number 339 of the molecular isotope.

[0173] 1 # The straight line slope of the third smallest mass number of the isotope of each fragment ion of the sample is directly obtained from C 2 and C 3 Two points, and the calculation results are filled in Table 12 to obtain Table 15.

[0174] Table 15 1 # The abundance data of the third smallest mass number of the sample is used to calculate the slope k of the straight line

[0175]

[0176] The slope k calculated according to Table 15 is 0.00045, and C is calculated from formula (6). 6 F 14 The abundance value of the third smallest mass number 340 of the molecular isotope, and its abundance value is 0.00196.

[0177] According to the calculated C 6 F 14 The isotope abundances of the minimum mass number of the molecular isotope, the second smallest mass number of the isotope, and the third smallest mass number of the isotope are filled in Table 10 to obtain Table 16, and Table 16 is the C calculated by the linear equation 6 F 14 The measurement results of the molecular isotope abundances.

[0178] Table 16 The C deduced by the linear equation 6 F 14 The isotope abundance result table

[0179]

[0180] As can be seen from Table 16, C 6 F 14 has a total molecular isotope abundance of 1.00076, which is very close to 1, and the overall abundance error is within ±0.1%, indicating that the linear equation established in the present invention for calculating the C 6 F 14 molecular isotope abundance is accurate and reliable.

[0181] Compare the molecular isotope abundances of the same Freon sample inferred by the two methods of "Excel image processing" and "establishing a linear equation", as shown in Table 17:

[0182] Table 17 Comparison of the results of two measurement methods

[0183]

[0184] As can be seen from the comparison in Table 17, the results obtained by the two methods are in good agreement, indicating that both methods are reliable and both methods meet the daily analysis requirements of C 6 F 14 molecular isotopes.

[0185] 3 Effects

[0186] The present invention reveals that the CF 6 F 14 of C 3 + 、C 2 F 5 + 、C 3 F 7 + fragment isotope abundances show a linear relationship with the carbon atom numbers 1, 2, and 3, and two methods of inferring the C 6 F 14 molecular isotope abundance are established, namely "Excel image processing" and "establishing a linear equation". The C 6 F 14 isotope abundances obtained by the two methods are in good agreement, the total molecular isotope abundance is very close to 1, and the overall abundance error is within ±0.2%. The established linear inference method is accurate and reliable and can be used for the measurement of C 6 F 14 molecular isotope abundance. C 4 F 10 、C 5 F 12 、C 6 F 14 、C 7 F 16 、C 8F 18 The molecular structures and properties of Freons such as C 6 F 14 are similar, and this linear inference method is also suitable for measuring the isotope abundances of these Freon molecules.

[0187] Example 2

[0188] In this example, the Excel image processing method was used to infer the isotope abundance of C 6 F 14

[0189] The CF 6 F 14 of the C 3 + sample, C 2 F 5 + and C 3 F 7 + fragment isotope abundances were measured by a certain measurement method. The isotope mass numbers of the fragments and their corresponding abundances are shown in Table 18.

[0190] Table 18 Measured values of the isotope abundances of three fragment ions of the C 6 F 14 sample

[0191]

[0192] The CF 6 F 14 of the C 3 + sample, C 2 F 5 + and C 3 F 7 + in Table 18 were re-arranged in ascending order of the mass numbers of the isotope abundances of the three fragment ions. The abundance with the smallest mass number was arranged in the first row, the abundance with the second smallest mass number was arranged in the second row, and the abundance with the third smallest mass number was arranged in the third row. CF 3 + C 2 F 5 + C 3 F 7 + are represented by C 1 C 2 C 3 respectively, as shown in Table 19.

[0193] Table 19 C 6 F 14 ​Table of the three fragment ion isotope abundances of the sample arranged in ascending order of mass number

[0194]

[0195] In the Excel document, with the number of carbon atoms as the abscissa and the abundance value as the ordinate, plot the abundances corresponding to the minimum mass number levels of the three fragment ions CF 3 + 、C 2 F 5 + 、C 3 F 7 + Connect the corresponding coordinate points into a line and extend the line segment to the position where the number of C atoms is 6 using linear extrapolation, as Figure 26 shown. Use the same method to plot the images of the isotope abundances corresponding to the second smallest mass number level and the third smallest mass number level of the three fragment ions CF 3 + 、C 2 F 5 + 、C 3 F 7 + showing the variation of the abundance with the number of carbon atoms, as Figure 28 、 Figure 30 shown. Respectively, in Figure 26 、 Figure 28 、 Figure 30 center on the intersection of the line of the abundance varying with the number of carbon atoms and the number of carbon atoms being 6, and zoom in on Figure 26 、 Figure 28 、 Figure 30 to obtain a segment of the screenshot, which are respectively as Figure 27 、 Figure 29 、 Figure 31 .

[0196] Read directly from Figure 27 the abundance value 0.93306 corresponding to the number of carbon atoms being 6. By the linear inference method, the minimum mass number 338 of the C 6 F 14 molecular isotope and the minimum mass numbers 69, 119, 169 of its fragment ions CF 3 + 、C 2 F 5 + 、C 3 F 7 + belong to the same mass number level, and it can be inferred that C 6 F 14The isotope abundance corresponding to the minimum mass number of 338 of the molecular isotope is 0.93306.

[0197] Read directly from Figure 29 the abundance value of 0.06545 corresponding to 6 carbon atoms, and by the linear inference method, C 6 F 14 The second smallest mass number of the molecular isotope, 339, and its fragment ions CF 3 + 、C 2 F 5 + 、C 3 F 7 + The second smallest mass numbers of 70, 120, and 170 belong to the same mass number level, and it can be inferred that the isotope abundance value of the second smallest mass number of 339 of the C 6 F 14 molecule is 0.6545.

[0198] Read directly from Figure 31 the abundance value of 0.00201 corresponding to 6 carbon atoms, and by the linear inference method, C 6 F 14 The third smallest mass number of the molecular isotope, 340, and its fragment ions C 2 F 5 + 、C 3 F 7 + The third smallest mass numbers of 121 and 171 belong to the same mass number level, and it can be inferred that the isotope abundance value of the third smallest mass number of 340 of the C 6 F 14 molecule is 0.00201.

[0199] Fill in the abundance values corresponding to the mass numbers 338, 339, and 340 of the C 6 F 14 molecular isotope into Table 10 to obtain Table 20, that is, the analysis result of the isotope abundance of C 6 F 14 measured by the Excel linear inference method.

[0200] Table 20 Excel Linear Inference of C 6 F 14 Isotope Abundance Result Table

[0201]

[0202] Example 3

[0203] This example uses a linear equation to calculate the isotope abundance of the C 6 F 14 sample.

[0204] The C was measured by a certain measurement method 6 F 14 The CF of the sample 3 + and C 2 F 5 + and C 3 F 7 + The isotope abundances of the fragments, the isotope mass numbers of the fragments and their corresponding abundances are shown in Table 21. (Using the Excel linear inference method for the same sample abundance data for easy comparison).

[0205] Table 21 C 6 F 14 Measured values of the isotope abundances of three fragment ions of the sample

[0206]

[0207] Re-arrange the isotope abundances of the three fragment ions of the C 6 F 14 sample in Table 21. The abundance with the smallest mass number is arranged in the first row, the abundance with the second smallest mass number is arranged in the second row, and the abundance with the third smallest mass number is arranged in the third row. CF 3 + and C 2 F 5 + and C 3 F 7 + Respectively represented by C 1 and C 2 and C 3 as shown in Table 22.

[0208] Table 22 C 6 F 14 Table of the isotope abundances of three fragment ions of the sample arranged in ascending order of mass number

[0209]

[0210] Using the isotope abundances corresponding to the smallest mass number level and the second smallest mass number level of the three fragments of the C 6 F 14 sample in Table 22, use formulas (7), (8) and (9) to calculate the slopes of the corresponding straight lines, and fill the calculation results into Table 11 to obtain Table 23 for calculating the slope of the linear equation corresponding to the smallest mass number level and Table 24 for calculating the slope of the linear equation corresponding to the second smallest mass number level.

[0211] Table 23 C 6 F14 Calculating the slope k of the straight line from the abundance data of the minimum mass number of the sample

[0212]

[0213] Table 24C 6 F 14 Calculating the slope k of the straight line from the abundance data of the second minimum mass number of the sample

[0214]

[0215] The slope k obtained from Table 23 is -0.01104. According to formula (5), the abundance value corresponding to C number 6 is calculated as 0.93356, i.e., C 6 F 14 The isotope abundance corresponding to the minimum mass number 338 of the isotope in the sample is 0.93356.

[0216] The slope k obtained from Table 24 is 0.01081. According to formula (5), the abundance value corresponding to C number 6 is calculated as 0.06529, i.e., C 6 F 14 The isotope abundance corresponding to the second minimum mass number 339 of the isotope in the sample is 0.06529.

[0217] C 6 F 14 The straight line slope of the abundance corresponding to the third minimum mass number of the sample isotope is directly obtained from C 2 and C 3 Two points are obtained and calculated according to formula (10). The calculation results are filled in Table 12 to obtain Table 25.

[0218] Table 25C 6 F 14 Calculating the slope k of the straight line from the abundance data of the third minimum mass number of the sample

[0219]

[0220] The slope k obtained from Table 25 is 0.00046. According to formula (6), the abundance value corresponding to C number 6 is calculated as 0.00200, which is C 6 F 14 The isotope abundance value corresponding to the third minimum mass number 340 in the sample is 0.00200.

[0221] According to the calculated abundances of the minimum mass, the second minimum mass number, and the third minimum mass number of the C 6 F 14 The isotope abundances are filled in Table 10 to obtain Table 26. Table 26 is the isotope abundance result of the C 6 F 14 sample calculated by the linear equation.

[0222] Table 26 Linear equation calculation C 6 F 14 Isotope abundance result table of

[0223]

[0224]

[0225] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for calculating the molecular isotope abundances of Freons using a linear model, characterized in that, the Freon is a Freon containing only carbon and fluorine, and the method includes the following steps: Step 1, determine the types of ion fragments that can be formed during the isotope analysis of Freons; Step 2, select the ion fragments with strong ion signals among the ion fragments as the receiving ions for measuring isotope abundances; Step 3, determine the number of isotopes and their mass numbers for each receiving ion; Step 4, arrange and layer the isotopes of each receiving ion in ascending order of mass number, divided into the smallest mass number layer, the second smallest mass number layer, the third smallest mass number layer,..., the Nth smallest mass number layer, where the isotope with the smallest mass number of each receiving ion is located in the smallest mass number layer, the second smallest is located in the second smallest mass number layer, and so on; Step 5, measure the isotope abundances of each receiving ion in the Freon sample; Step 6, re-queue the isotope abundances of each receiving ion according to the mass number levels in Step 4; Step 7, with the number of carbon atoms as the abscissa and the isotope abundance as the ordinate, connect the corresponding coordinate points into a line to obtain a graph of the change in fragment isotope abundance with the number of carbon atoms; Step 8, use the method of linear inference to calculate the molecular isotope abundances of Freons at the same mass number levels; In the said Step 8, the method of linear inference includes two methods: Excel image processing and establishing a linear equation; The method of the said Excel image processing is as follows: In an Excel document, perform a linear fit of the graph of the change in the isotope abundance of the smallest mass number layer of each receiving ion in the Freon sample with the number of carbon atoms to obtain a straight line of the change in isotope abundance with the number of carbon atoms. The straight line is extended, and with the intersection point of the number of carbon atoms being the number of carbon atoms in the Freon and the straight line of the change in isotope abundance with the number of carbon atoms as the center, read out the abundance value corresponding to the number of carbon atoms in the Freon, which is the abundance corresponding to the smallest mass number in the Freon isotope; and so on, to obtain the abundance corresponding to the second smallest mass number in the Freon isotope,..., the abundance corresponding to the Nth smallest mass number layer; The method of establishing a linear equation is as follows: Step s1, according to the linear law of the change in the isotope abundance of the receiving ions at the same mass number level with the number of carbon atoms, design a straight line equation: Formula y n = y 1 + k ( n -1)is the calculation formula for the isotope abundance corresponding to the minimum mass number and the isotope abundance corresponding to the second minimum mass number of the molecular isotope of Freon with n carbon atoms; Formula y n = y 1 + k ( n - 2) is the calculation formula for the isotope abundance corresponding to the third smallest mass number; In the above formula y is the isotope abundance of the received ions, n is the number of carbon atoms, k is the slope of the straight line; Step s2, calculate the slope of the linear equation; Calculation of the slope of the straight-line equation for the isotope abundance corresponding to the minimum mass number and the isotope abundance corresponding to the second minimum mass number: Taking C 1 corresponding abundance point as the reference, a straight line formed by the corresponding points of C 1 and C 2 , with slope k 12 , and a straight line formed by the corresponding points of C 1 and C 3 , with slope k 13 ; k 12 and k 13 average value k , k is the slope of a straight line passing through point 1 and between the straight line of point 1 and point 2 and the straight line of point 1 and point 3, which is the slope of the linear equation for the isotope abundance corresponding to the minimum mass number and the isotope abundance corresponding to the second minimum mass number of the C 6 F 14 molecule, k 12 , k 13 and k calculation formula is: ； Calculation of the slope of the straight-line equation corresponding to the abundance of the third smallest mass number: Calculate the slope of the straight line from C 2 to C 3 using the following formula: ； Step s3, calculate the molecular isotope of the Freon from the linear equation in Step s1 and the slope of the linear equation in Step s2.

2. The method for calculating the molecular isotope abundances of Freons using a linear model according to claim 1, characterized in that, with the intersection point of the number of carbon atoms being the number of carbon atoms in the Freon and the straight line of the change in isotope abundance with the number of carbon atoms as the center, perform local magnification, and then read out the abundance value corresponding to the number of carbon atoms in the Freon.

3. The method for calculating the molecular isotope abundances of Freons using a linear model according to claim 1, characterized in that, The Freon is C 4 F 10 、C 5 F 12 、C 6 F 14 、C 7 F 16 or C 8 F 18 。 4. The method for calculating the molecular isotope abundances of Freons using a linear model according to claim 1, characterized in that, When the Freon is C 6 F 14 In step 2, the ionic fragments CF 3 + and C 2 F 5 + and C 3 F 7 + are used as received ions for isotope abundance measurement.

5. The method for calculating the molecular isotope abundances of Freons using a linear model according to claim 1, characterized in that When the freon is C 6 F 14 in step 4, the mass number of CF 3 + is 69, the mass number of C 2 F 5 + is 119, and the mass number of C 3 F 7 + is 169, belonging to the minimum mass number layer; CF 3 + has a mass number of 70, C 2 F 5 + has a mass number of 120, C 3 F 7 + with a mass number of 170 belongs to the second smallest mass number layer; C 2 F 5 + has a mass number of 121, C 3 F 7 + with a mass number of 171 belongs to the third smallest mass number layer.

6. The method for calculating the molecular isotope abundance of Freon by the linear model according to claim 1, characterized in that When the freon is C 6 F 14 In step 8, the isotopic abundances of the three fragment ions with the smallest mass number levels of CF 3 + , C 2 F 5 + , C 3 F 7 + are linearly fitted with the graph of the change of the carbon atom number, and the straight line is extended in the direction of C 6 , and the abundance value corresponding to the carbon atom number of 6 is read out, that is, the abundance corresponding to the minimum mass number of 338 of the C 6 F 14 isotope; For CF 3 + 、C 2 F 5 + 、C 3 F 7 + Process the graph of the isotope abundances of the second smallest mass number level of the three fragment ions with respect to the number of carbon atoms, and read out the abundance value corresponding to 6 carbon atoms, that is, the abundance of the C 6 F 14 isotope with the second smallest mass number of 339; For CF 3 + 、C 2 F 5 + 、C 3 F 7 + Process the graph of the isotope abundances of the third smallest mass number level of the three fragment ions with respect to the number of carbon atoms, and directly read out the abundance value corresponding to 6 carbon atoms, that is, the abundance corresponding to the third smallest mass number of the C 6 F 14 isotope being 340.

7. The method for calculating the molecular isotope abundance of Freon by the linear model according to claim 1, characterized in that When the freon is C 6 F 14 In step 8, taking the abundance data of the minimum mass number of each fragment ion isotope of C 6 F 14 as an example, calculate the straight-line slope k , from the formula y n = y 1 + k ( n -1), calculate the abundance corresponding to the minimum mass number of 338 of the C 6 F 14 isotope; Taking C 6 F 14 the abundance data of the second smallest mass number of each fragment ion isotope to calculate the straight-line slope k, from the formula y n = y 1 + k ( n -1)calculate the abundance corresponding to the second smallest mass number of 339 for the C 6 F 14 isotope; C 6 F 14 The linear slope of the third smallest mass number of each fragment ion isotope is directly obtained from points C 2 and C 3 , and the abundance value corresponding to the third smallest mass number of 340 of the C y n = y 1 + k ( n -2)is calculated by the formula 6 F 14 isotope.

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