CN105486675A - Laser Raman Detection Method for Quantitative Analysis of Carbon Isotopic Composition of CO2 Gas - Google Patents

Abstract

The invention provides a laser Raman detection method for quantitatively analyzing the carbon isotope composition of _CO2 gas, comprising the following steps: 1. Calculating the Raman quantization factor _F12CO2 of ¹² CO2; _2. Calculating the Raman quantization factor of ¹³ _CO2 F _13CO2 ; 3. According to the formula C ^[12CO2] /C ^[13CO2] = (A _12CO2 /A _13CO2 )×(F _13CO2 /F _12CO2 ), calculate the molar ratio C of ¹² CO ₂ and ¹³ CO ₂ in the CO ₂ gas ^{[ 12CO2]} /C ^[13CO2] . The present invention performs microscopic laser Raman testing and analysis on ¹² CO ₂ /N ₂ mixed gas and ¹³ CO ₂ /N ₂ mixed gas in different proportions, and the microscopic laser Raman spectrometry adopted has high precision, in-situ, non-destructive and fast and other characteristics, the use of micro-laser Raman spectroscopy can quantitatively analyze the composition of carbon isotopes of CO ₂ , which has broad application prospects.

Description

Laser Raman Detection Method for Quantitative Analysis of Carbon Isotopic Composition of CO2 Gas

technical field

The invention belongs to the technical field of spectral analysis, and in particular relates to a laser Raman detection method for quantitatively analyzing the carbon isotope composition of _CO2 gas.

Background technique

Raman spectroscopy is an important modern molecular spectroscopy technology, which has been widely used in physics, chemistry, materials, petroleum, biology, environment, geology, astronomy and other fields. Microlaser Raman spectroscopy (LRM) is to focus the incident laser light on the sample through a microscope, and accurately obtain the relevant chemical composition, crystal structure, molecular interaction and molecular orientation of the illuminated sample micro-region without interference from surrounding substances. and other information. Laser Raman spectroscopy has gradually become an important analysis method in the basic research of earth science.

Fluid inclusions are the original geological fluids in which minerals are captured and preserved in the defects of mineral crystals during the crystal growth process. By studying the composition and properties of mineral fluid inclusions, we can understand the conditions of diagenesis and mineralization, fluid composition, material sources and geological conditions. function etc. CO ₂ is an important volatile component in fluid inclusions, and the stable isotopes of CO ₂ are ¹² CO ₂ and ¹³ CO ₂ . The carbon isotopic composition characteristics of CO ₂ gas in fluid inclusions are of great geological significance in the study of the origin of minerals and fluid evolution in the crust and upper mantle, and provide a basis for the study of mineralization of deposits, oil and gas migration and accumulation, and evolution of geological fluids. and tectonic dynamics provide important information.

At present, when analyzing and testing the isotope of inclusions, the traditional method is to open the inclusions by thermal explosion, grinding, crushing, etc., and then analyze the carbon isotopes of CO ₂ released from the inclusions by mass spectrometry. However, this method is used to obtain the CO ₂ carbon isotope mixing results of minerals in different stages and different genetic sources, and cannot obtain the CO ₂ carbon isotope composition of a single fluid inclusion in a mineral that represents a specific diagenetic ore-forming stage. However, microlaser Raman spectroscopy has the characteristics of high precision, in situ, non-destructive and fast. Therefore, the use of microlaser Raman spectroscopy to quantitatively analyze the composition of _CO2 carbon isotopes in individual fluid inclusions has a good application prospect.

Contents of the invention

The technical problem to be solved by the present invention is to provide a laser Raman detection method for quantitatively analyzing the carbon isotope composition of _CO2 gas in view of the above-mentioned deficiencies in the prior art. The micro-laser Raman spectroscopy used in this method has the characteristics of high precision, in-situ, non-destructive and fast. Therefore, this method can quantitatively analyze the composition of CO ₂ carbon isotopes in individual fluid inclusions by using micro-laser Raman spectroscopy. It has a good application prospect.

In order to solve the above-mentioned technical problems, the technical solution adopted in the present invention is: a kind of quantitative analysis CO _The laser Raman detection method of gas carbon isotope composition is characterized in that, the method comprises the following steps:

Step 1. Calculating the Raman quantification factor F _12CO2 of ¹² CO ₂ , the specific method is:

Step 101, using a gas mixing proportioner to uniformly mix ¹² CO ₂ and N ₂ in different volume ratios to obtain a series of ¹² CO ₂ /N ₂ mixed gases with different proportions;

Step 102: Use a microscopic laser Raman spectrometer to perform microscopic laser Raman detection on the ¹² CO ₂ /N ₂ mixed gas in step 101 in various ratios, and obtain the characteristic peak ν ^[N2] of N ₂ and ¹² CO ₂ Fermi resonance double characteristic peaks ν _- ^[12CO2] and ν ₊ ^[12CO2] , and then calculate the peak areas A _- ^[12CO2] and ν ₊ ^[12CO2 ] at ν _- ^[12CO2] under various ratio conditions The peak area _{A +} ^[12CO2] at the place and the peak area A1 ^[ N2] at the v ^[N2] place; The unit _of described ^v-[12CO2] , v ₊ ^[12CO2] and v ^[N2] is cm ^-1 ;

Step 103, according to A- ^[12CO2] and _{A +} ^[12CO2] described in step 102, calculate the peak area A ^[12CO2] _of the ^12CO2 characteristic peak under various proportioning conditions, and the _A ^[12CO2] =A- ^[12CO2] +A ₊ ^[12CO2] , then calculate the characteristic peak area ratio K ₁ of ¹² CO ₂ and N ₂ under various proportioning conditions according to the A ^[12CO2] , the K ₁ = [A ^{[12CO2 ]} /Σ _12CO2 )/A ₁ ^[N2] ; said Σ _12CO2 is ¹² CO ₂ relative Raman scattering cross section normalization factor;

Step 104, take K1 described in step 103 as the ordinate, and use the molar ratio C [ _12CO2 ^] /C ^[N2] _of ^12CO2 and _N2 as the abscissa to project a graph and perform linear fitting to calculate the fitted straight line The slope of F _12CO2 is obtained;

Step 2. Calculating the Raman quantification factor F _13CO2 of ¹³ CO ₂ , the specific method is:

Step 201, using a gas mixing proportioner to uniformly mix ¹³ CO ₂ and N ₂ in different volume ratios to obtain a series of ¹³ CO ₂ /N ₂ mixed gases with different proportions;

Step 202: Use a microscopic laser Raman spectrometer to perform microscopic laser Raman detection on the various ratios of ¹³ CO ₂ /N ₂ mixed gases in step 201, and obtain the characteristic peaks of N ₂ ν ^[N2] and ¹³ CO ₂ Fermi resonance double characteristic peaks ν _- ^[13CO2] and ν ₊ ^[13CO2] , and then calculate the peak areas A _- ^[13CO2] and ν ₊ ^[13CO2 ] at ν _- ^[13CO2] under various ratio conditions The peak area A ₊ ^[13CO2] at the place and the peak area A2 ^[ _N2 ] at the ν ^[N2] place; the units of _ν- ^[12CO2] and ν ₊ ^[12CO2] are cm ^-1 ;

Step 203, according to A- ^[13CO2] and _{A +} ^[13CO2] described in step 202, calculate the peak area A ^[13CO2] of the characteristic peak of ¹³ _CO2 under various proportioning conditions, the _A ^[13CO2] = A- ^[13CO2] +A ₊ ^[13CO2] , and then calculate the characteristic peak area ratio K ₂ of ¹³ CO ₂ and N ₂ under various proportioning conditions according to the A ^[13CO2] , the K ₂ = [A ^{[13CO2 ]} /Σ _13CO2 )/A ₂ ^[N2] ; said Σ _13CO2 is ¹³ CO ₂ relative Raman scattering cross section normalization factor;

Step 204, taking K2 mentioned in step 203 as the ordinate, and taking the molar ratio C [ ^{13CO2 ]} /C ^[N2] _{of 13CO2} and _N2 as the abscissa to project a graph and perform linear fitting to calculate the fitted straight line The slope of F _13CO2 is obtained;

Step 3, using a microscopic laser Raman spectrometer to perform microscopic laser Raman detection on the CO ₂ gas mixed with ¹² CO ₂ and ¹³ CO ₂ to obtain the peak area A _{12CO 2} of the characteristic peak of ¹² CO 2 in the CO ₂ gas and The peak area A _13CO2 ^{of the} characteristic peak of ¹³ CO ₂ , and _{then calculate the 12 CO 2} ^{and 13} The molar ratio of CO ₂ C ^[12CO2] /C ^[13CO2] .

The aforementioned laser Raman detection method for quantitatively analyzing the carbon isotope composition of CO ₂ gas is characterized in that in step 102, ν _- ^[12CO2] = 1287cm ^-1 , said ν ₊ ^[12CO2] = 1390cm ^-1 , said ν ^[N2] = 2332 cm ^-1 .

The above-mentioned laser Raman detection method for quantitatively analyzing the carbon isotope composition of CO ₂ gas is characterized in that Σ _12CO2 = 1.49 in step 103.

The above-mentioned laser Raman detection method for quantitatively analyzing the carbon isotope composition of CO ₂ gas is characterized in that in step 202, ν _- ^[13CO2] = 1267cm ^-1 , and ν ₊ ^[13CO2] = 1372cm ^-1 .

The aforementioned laser Raman detection method for quantitatively analyzing the carbon isotope composition of CO ₂ gas is characterized in that Σ _13CO2 = 1.437 in step 203 .

Compared with the prior art, the present invention has the following advantages:

The present invention prepares samples of ¹² CO ₂ /N ₂ and ¹³ CO ₂ /N ₂ mixtures in different proportions and conducts microscopic laser Raman test and analysis. The slope of the combined line is considered as the Raman quantization factor. The carbon isotope mole fraction ratio of CO ₂ gas can be obtained from the product of Raman peak area ratio and Raman quantization factor ratio. Because the micro-laser Raman spectroscopy adopted by the present invention has the characteristics of high precision, in-situ, non-destructive and fast, etc., the micro-laser Raman spectroscopy can be used to quantitatively analyze the composition of _CO2 carbon isotopes in a single fluid inclusion, which has the advantages of Wide application prospects.

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

Description of drawings

Figure 1 is a fitting line diagram of the characteristic peak area ratio K ₁ and the molar ratio C ^[12CO2] /C ^[N2] of ¹² CO ₂ and N ₂ in the present invention.

Fig. 2 is a fitting line diagram of the characteristic peak area ratio K ₂ and the molar ratio C ^[13CO2] /C ^[N2] of ¹³ CO ₂ and N ₂ in the present invention.

detailed description

The invention quantitatively analyzes the composition of the carbon isotope in the _CO2 gas through the method of microscopic laser Raman spectrum analysis and linear fitting. The present invention quantitatively analyzes CO _The laser Raman detection method of gas carbon isotope composition comprises the following steps:

Step 1. Calculating the Raman quantification factor F _12CO2 of ¹² CO ₂ , the specific method is:

Step 101, using a gas mixing proportioner to uniformly mix ¹² CO ₂ and N ₂ in different volume ratios to obtain a series of ¹² CO ₂ /N ₂ mixed gases with different proportions;

Step 102: Use a microscopic laser Raman spectrometer to perform microscopic laser Raman detection on the various ratios of ¹² CO ₂ /N ₂ mixed gases in step 101, and obtain the characteristic peak ν ^[N2] of N ₂ and ¹² CO ₂ Fermi resonance double characteristic peaks ν _- ^[12CO2] and ν ₊ ^[12CO2] , and then calculate the peak areas A _- ^[12CO2] and ν ₊ ^[12CO2 ] at ν _- ^[12CO2] under various ratio conditions The peak area _{A +} ^[12CO2] at the place and the peak area A1 ^[ N2] at the v ^[N2] place; The unit _of described ^v-[12CO2] , v ₊ ^[12CO2] and v ^[N2] is cm ^-1 ;

Step 103, according to A- ^[12CO2] and _{A +} ^[12CO2] described in step 102, calculate the peak area A ^[12CO2] _of the ^12CO2 characteristic peak under various proportioning conditions, and the _A ^[12CO2] =A- ^[12CO2] +A ₊ ^[12CO2] , then calculate the characteristic peak area ratio K ₁ of ¹² CO ₂ and N ₂ under various proportioning conditions according to the A ^[12CO2] , the K ₁ = [A ^{[12CO2 ]} /Σ _12CO2 )/A ₁ ^[N2] ; said Σ _12CO2 is ¹² CO ₂ relative Raman scattering cross section normalization factor;

Step 104, take K1 described in step 103 as the ordinate, and use the molar ratio C [ _12CO2 ^] /C ^[N2] _of ^12CO2 and _N2 as the abscissa to project a graph and perform linear fitting to calculate the fitted straight line The slope of F _12CO2 is obtained;

Step 2. Calculating the Raman quantification factor F _13CO2 of ¹³ CO ₂ , the specific method is:

Step 201, using a gas mixing proportioner to uniformly mix ¹³ CO ₂ and N ₂ in different volume ratios to obtain a series of ¹³ CO ₂ /N ₂ mixed gases with different proportions;

Step 202, using a micro-laser Raman spectrometer to perform micro-laser Raman detection on the ¹³ CO ₂ /N ₂ mixed gas in step 201 in various ratios, and obtain the characteristic peak ν ^[N2] of N ₂ and ¹³ CO ₂ Fermi resonance double characteristic peaks ν _- ^[13CO2] and ν ₊ ^[13CO2] , and then calculate the peak areas A _- ^[13CO2] and ν ₊ ^[13CO2 ] at ν _- ^[13CO2] under various ratio conditions The peak area A ₊ ^[13CO2] at the place and the peak area A2 ^[ _N2 ] at the ν ^[N2] place; the units of _ν- ^[12CO2] and ν ₊ ^[12CO2] are cm ^-1 ;

Step 203, according to A- ^[13CO2] and _{A +} ^[13CO2] described in step 202, calculate the peak area A ^[13CO2] of the characteristic peak of ¹³ _CO2 under various proportioning conditions, the _A ^[13CO2] = A- ^[13CO2] +A ₊ ^[13CO2] , and then calculate the characteristic peak area ratio K ₂ of ¹³ CO ₂ and N ₂ under various proportioning conditions according to the A ^[13CO2] , the K ₂ = [A ^{[13CO2 ]} /Σ _13CO2 )/A ₂ ^[N2] ; said Σ _13CO2 is ¹³ CO ₂ relative Raman scattering cross section normalization factor;

Step 204, taking K2 mentioned in step 203 as the ordinate, and taking the molar ratio C [ ^{13CO2 ]} /C ^[N2] _{of 13CO2} and _N2 as the abscissa to project a graph and perform linear fitting to calculate the fitted straight line The slope of F _13CO2 is obtained;

Step 3, using a microscopic laser Raman spectrometer to perform microscopic laser Raman detection on the CO ₂ gas mixed with ¹² CO ₂ and ¹³ CO ₂ to obtain the peak area A _{12CO 2} of the characteristic peak of ¹² CO 2 in the CO ₂ gas and The peak area A _13CO2 ^{of the} characteristic peak of ¹³ CO ₂ , and _{then calculate the 12 CO 2} ^{and 13} The molar ratio of CO ₂ C ^[12CO2] /C ^[13CO2] .

During the specific implementation process, when performing microscopic laser Raman detection of ¹² CO ₂ /N ₂ mixed gas: the laser Raman spectrum analysis is performed on ¹² CO ₂ /N ₂ mixed gas with different ratios, and it can be found on the spectrum: Two strong characteristic lines appear in the Raman spectrum of CO ₂ , which are the double peaks of the Fermi resonance of CO ₂ , and the frequencies are respectively at ^{1287cm -1} _{and 1390cm} ^{-1 (} i.e. ^] ). There is a very strong peak at the frequency of 2332cm ^-1 , which is the characteristic peak of N ₂ (ie ν ^[N2] ).

In the specific implementation process, when analyzing the characteristic peaks of the microscopic laser Raman spectrum of the ¹² CO ₂ /N ₂ mixed gas: the peak position, shape and intensity of the Raman band only depend on the molecular polarization of the molecule itself during the vibration process rate change. Therefore, every substance with Raman activity has its specific Raman spectrum characteristics. According to the characteristics of the substance, the Raman spectrum can identify the type of substance, which is the basic principle of qualitative analysis of Raman spectroscopy. Σ _j is the normalization factor of the relative Raman scattering cross-section, and the value of Σ _j for N ₂ is 1 according to the international standard, and the value of Σ _j for ¹² CO ₂ is 1.49 after many experiments under the conditions of the laboratory equipment. The ratio of the Raman characteristic peak area of a molecule to its corresponding relative Raman scattering cross section normalization factor Σ is A/Σ, which is proportional to the relative molar concentration of the molecule, namely: (A _a /Σ _a )/(A _b /Σ _b )=(C _a /C _b )·(F _a /F _b ), where A, C, and F are the Raman characteristic peak peak area, mole fraction, and Raman quantization factor, respectively. Table 1 lists the Raman spectrum data of ¹² CO ₂ /N ₂ mixed gas under different ratio conditions. With 1287cm ^-1 (ν _- ^[12CO2] ), 1390cm ^-1 (ν ₊ ^[12CO2] ) and 2332cm ^-1 (ν ^[N2] ) characteristic peak peak area is recorded as A _- ^[12CO2] , A ₊ ^{[ 12CO2]} and A ₁ ^[N2] .

Table 1 Raman spectrum data of ¹² CO ₂ /N ₂ mixed gases

During the specific implementation process, when the Raman quantification factor F _12CO2 is obtained by fitting a straight line: the Raman spectrum of ¹² CO ₂ appears Fermi vibration double peaks, when the characteristic peak area ratio K ₁ of ¹² CO ₂ and N ₂ is used as the ordinate , when the molar ratio C ^[13CO2] /C ^[N2] is used as the abscissa to project the graph (as shown in Figure 1), the linear equation of the zero-crossing point is obtained: y=1.16349x, and the correlation coefficient R2 is ^0.99919 . The slope of the fitted line is F _12CO2 , and its value is 1.16349.

During the specific implementation process, when performing microscopic laser Raman detection of ¹³ CO ₂ /N ₂ mixed gas, the laser Raman spectrum analysis of ¹³ CO ₂ /N ₂ mixed gas with different ratios can be found on the spectrum: Two strong characteristic lines appear in the Raman spectrum of CO ₂ , which are the Fermi resonance doublets of CO ₂ , and the frequencies are respectively at 1267cm ^-1 and 1372cm ^-1 (that is, ν _- ^[13CO2] and ν ₊ ^{[13CO2 ]} ). There is a very strong peak at the frequency of 2332cm ^-1 , which is the characteristic peak of N ₂ (ie ν ^[N2] ).

In the specific implementation process, when analyzing the characteristic peaks of the microscopic laser Raman spectrum of the ¹³ CO ₂ /N ₂ mixed gas: the peak position, shape and intensity of the Raman band only depend on the molecular polarization of the molecule itself during the vibration process rate change. Therefore, every substance with Raman activity has its specific Raman spectrum characteristics. According to the characteristics of the substance, the Raman spectrum can identify the type of substance, which is the basic principle of qualitative analysis of Raman spectroscopy. Σ _j is the normalization factor of the relative Raman scattering cross-section, and the value of Σ _j for N ₂ is set to be 1 internationally. After calculation and analysis, the value of Σ _j for ¹³ CO ₂ is 1.437. The ratio of the Raman characteristic peak area of a molecule to its corresponding relative Raman scattering cross section normalization factor Σ is A/Σ, which is proportional to the relative molar concentration of the molecule, namely: (A _a /Σ _a )/(A _b /Σ _b )=(C _a /C _b )·(F _a /F _b ), where A, C, and F are the Raman characteristic peak peak area, mole fraction, and Raman quantization factor, respectively. Table 2 lists the Raman spectrum data of ¹³ CO ₂ /N ₂ mixed gas molar ratios of 0, 0.166, 0.8, 1 and 1.5, respectively. With 1267cm ^-1 (ν _- ^[13CO2] ), 1372cm ^-1 (ν ₊ ^[13CO2] ) and 2332cm ^-1 (ν ^[N2] ) The characteristic peak peak area is recorded as A _- ^[13CO2] , A ₊ ^{[ 13CO2]} and A2[ _N2 ^] .

Table 2 Raman spectrum data of ¹³ CO ₂ /N ₂ mixed gases

In the specific implementation process, when the Raman quantization factor F _13CO2 is obtained by fitting a straight line, the Raman spectrum of ¹³ CO ₂ appears Fermi vibration doublets, when the sum of the peak areas of the ¹³ CO ₂ Fermi resonance doublets and the N ₂ When the peak area ratio K is used as the ordinate, and the molar ratio C ^[13CO2] /C ^[N2] _is used as the abscissa to project the graph (as shown in Figure 2), the linear equation of the zero-crossing point is obtained: y=1.61086x and the correlation coefficient R ² =0.99975. The slope of the fitted straight line equation is F _13CO2 , and its value is 1.61086.

During the specific implementation process, the molar ratio C ^[12CO2 of ¹² CO ₂ and ¹³ CO ₂ in the mixed gas is calculated according to the formula C ^[12CO2] /C ^[13CO2] = (A _12CO2 /A _13CO2 )×(F _13CO2 /F _12CO2 ) ^] /C ^[13CO2] : Specifically, the known Raman quantization factors F _13CO2 and F _12CO2 are respectively equal to 1.61086 and 1.16349, and their ratio F _13CO2 /F _12CO2 is 1.3845, which is a constant. Therefore, if the Raman characteristic peak area values of ¹³ CO ₂ and ¹² CO ₂ can be measured by micro-laser Raman spectroscopy, the molar ratio C _12CO2 /C _13CO2 can be calculated according to A _12CO2 /A _13CO2 and F _13CO2 /F The product of _12CO2 is obtained.

In the following, the quantitative analysis of the composition of carbon isotopes in CO ₂ gas will be illustrated by using the research results of the present invention.

Example 1

¹² CO ₂ / ¹³ CO ₂ mixed-type CO ₂ artificial inclusions were prepared in the laboratory. It is known that the molar ratio of ¹² CO ₂ to ¹³ CO ₂ in the CO ₂ artificial inclusions is C ^[12CO2] / C ^[13CO2] = 1, Then, according to the formula C ^[12CO2] /C ^[13CO2] = (A _12CO2 /A _13CO2 )×(F _13CO2 /F _12CO2 ), estimate the molar ratio of ¹² CO ₂ to ¹³ CO ₂ in the artificial inclusions, and compare the relative errors. In the Raman spectrum of ¹² CO ₂ / ¹³ CO ₂ artificial inclusions with a molar ratio of 1, it can be clearly seen that the peak positions are at 1267cm ^-1 (ν _- ^[13CO2] ), 1372cm ^-1 (ν ₊ ^{[ 13CO2]} ), the peaks at 1287cm ^-1 (ν _- ^[12CO2] ) and 1390cm ^-1 (ν ₊ ^[12CO2] ), they are the Raman characteristic peaks of ¹² CO ₂ and ¹³ CO ₂ , and the peak areas of the characteristic peaks are A _- ^[13CO2] , A ₊ ^[13CO2] , A _- ^[12CO2] , A ₊ ^[12CO2] , the sum of the peak areas A _- ^[12CO2] +A ₊ ^[12CO2] and A _- ^[13CO2] +A ₊ ^{[13CO2 ]} are respectively recorded as A _12CO2 and A _13CO2 . Table 3 lists the Fermi doublet peak area values of ¹² CO ₂ and ¹³ CO ₂ in artificial inclusions and the molar ratio estimated by the formula. After calculation, the molar ratio of artificial inclusions is 1.03542, and their relative error is 3.54%. This shows that when F _13CO2 and F _12CO2 are 1.61086 and 1.16349 respectively, if the Raman characteristic peak area values of ¹³ CO ₂ and ¹² CO ₂ are measured by micro-laser Raman spectroscopy, it can be calculated according to A _12CO2 /A The product of _13CO2 and F _13CO2 /F _12CO2 can estimate the molar ratio C ^[12CO2] /C ^[13CO2] of CO ₂ , so a quantitative analysis of CO ₂ gas carbon isotope laser Raman test method can be established.

Table 3 Examination data of inclusion samples in Example 1

Example 2

¹² CO ₂ / ¹³ CO ₂ mixed-type CO ₂ artificial inclusions were prepared in the laboratory, and the molar ratio of ¹² CO ₂ to ¹³ CO ₂ was known to be C ^[12CO2] / C ^[13CO2] = 2, and then according to the formula C ^{[12CO2 ]} /C ^[13CO2] = (A _12CO2 /A _13CO2 )×(F _13CO2 /F _12CO2 ), estimate the molar ratio of ¹² CO ₂ to ¹³ CO ₂ in artificial inclusions, and compare the relative errors. In the Raman spectrum of ¹² CO ₂ / ¹³ CO ₂ artificial inclusions with a molar ratio of 2, it can be clearly seen that the peak positions are at 1267cm ^-1 (ν _- ^[13CO2] ), 1372cm ^-1 (ν ₊ ^{[13CO2 ]} ), the peaks at 1287cm ^-1 (ν _- ^[12CO2] ) and 1390cm ^-1 (ν ₊ ^[12CO2] ), they are the Raman characteristic peaks of ¹² CO ₂ and ¹³ CO ₂ , and the peak area of the characteristic peaks is A _- ^[13CO2] , A ₊ ^[13CO2] , A _- ^[12CO2] , A ₊ ^[12CO2] , the sum of the peak areas A _- ^[12CO2] +A ₊ ^[12CO2] and A _- ^[13CO2] +A ₊ ^{[13CO2 ]} are respectively recorded as A _12CO2 and A _13CO2 . Table 4 lists the Fermi doublet peak area values of ¹² C and ¹³ C in the artificial inclusions and the molar ratio estimated by the formula. After calculation, the molar ratio of artificial inclusions is 1.93855, and their relative error is -1.53%. This shows that when F _13CO2 and F _12CO2 are 1.61086 and 1.16349 respectively, if the Raman characteristic peak area values of ¹³ CO ₂ and ¹² CO ₂ are measured by micro-laser Raman spectroscopy, it can be calculated according to A _12CO2 /A The product of _13CO2 and F _13CO2 /F _12CO2 can estimate the molar ratio C ^[12CO2] /C ^[13CO2] of CO ₂ , so a quantitative analysis of CO ₂ gas carbon isotope laser Raman test method can be established.

Table 4 Examination data of inclusion samples in Example 2

To sum up, the present invention is to perform microscopic laser Raman detection and analysis on the prepared mixed gas samples with different ratios of ¹² CO ₂ /N ₂ and ¹³ CO ₂ /N ₂ , and the Raman characteristic peak area ratio of the gas to its molar ratio In direct proportion, the slope of the fitted equation is considered as the Raman quantification factor. The carbon isotope molar ratio of CO ₂ gas can be calculated from the product of Raman peak area ratio and Raman quantization factor ratio. Because the micro-laser Raman spectroscopy adopted by the present invention has the characteristics of high precision, in-situ, non-destructive and fast, etc., the micro-laser Raman spectroscopy can be used to quantitatively analyze the composition of _CO2 carbon isotopes in a single fluid inclusion, which has the advantages of Very good application prospects.

The above descriptions are only preferred embodiments of the present invention, and do not limit the present invention in any way. All simple modifications, changes and equivalent changes made to the above embodiments according to the technical essence of the invention still belong to the protection scope of the technical solution of the invention.

Claims (5)

1. a kind of quantitative analysis CO _The laser Raman detection method that gas carbon isotope forms, it is characterized in that, the method comprises the following steps: Step 1. Calculating the Raman quantification factor F _12CO2 of ¹² CO ₂ , the specific method is: Step 101, using a gas mixing proportioner to uniformly mix ¹² CO ₂ and N ₂ in different volume ratios to obtain a series of ¹² CO ₂ /N ₂ mixed gases with different proportions; Step 102: Use a microscopic laser Raman spectrometer to perform microscopic laser Raman detection on the ¹² CO ₂ /N ₂ mixed gas in step 101 in various ratios, and obtain the characteristic peak ν ^[N2] of N ₂ and ¹² CO ₂ Fermi resonance double characteristic peaks ν _- ^[12CO2] and ν ₊ ^[12CO2] , and then calculate the peak areas A _- ^[12CO2] and ν ₊ ^[12CO2 ] at ν _- ^[12CO2] under various ratio conditions The peak area _{A +} ^[12CO2] at the place and the peak area A1 ^[ N2] at the v ^[N2] place; The unit _of described ^v-[12CO2] , v ₊ ^[12CO2] and v ^[N2] is cm ^-1 ; Step 103, according to A- ^[12CO2] and _{A +} ^[12CO2] described in step 102, calculate the peak area A ^[12CO2] _of the ^12CO2 characteristic peak under various proportioning conditions, and the _A ^[12CO2] =A- ^[12CO2] +A ₊ ^[12CO2] , then calculate the characteristic peak area ratio K ₁ of ¹² CO ₂ and N ₂ under various proportioning conditions according to the A ^[12CO2] , the K ₁ = [A ^{[12CO2 ]} /Σ _12CO2 )/A ₁ ^[N2] ; said Σ _12CO2 is ¹² CO ₂ relative Raman scattering cross section normalization factor; Step 104, take K1 described in step 103 as the ordinate, and use the molar ratio C [ _12CO2 ^] /C ^[N2] _of ^12CO2 and _N2 as the abscissa to project a graph and perform linear fitting to calculate the fitted straight line The slope of F _12CO2 is obtained; Step 2. Calculating the Raman quantification factor F _13CO2 of ¹³ CO ₂ , the specific method is: Step 201, using a gas mixing proportioner to uniformly mix ¹³ CO ₂ and N ₂ in different volume ratios to obtain a series of ¹³ CO ₂ /N ₂ mixed gases with different proportions; Step 202: Use a microscopic laser Raman spectrometer to perform microscopic laser Raman detection on the various ratios of ¹³ CO ₂ /N ₂ mixed gases in step 201, and obtain the characteristic peaks of N ₂ ν ^[N2] and ¹³ CO ₂ Fermi resonance double characteristic peaks ν _- ^[13CO2] and ν ₊ ^[13CO2] , and then calculate the peak areas A _- ^[13CO2] and ν ₊ ^[13CO2 ] at ν _- ^[13CO2] under various ratio conditions The peak area A ₊ ^[13CO2] at the place and the peak area A2 ^[ _N2 ] at the ν ^[N2] place; the units of _ν- ^[12CO2] and ν ₊ ^[12CO2] are cm ^-1 ; Step 203, according to A- ^[13CO2] and _{A +} ^[13CO2] described in step 202, calculate the peak area A ^[13CO2] of the characteristic peak of ¹³ _CO2 under various proportioning conditions, the _A ^[13CO2] = A- ^[13CO2] +A ₊ ^[13CO2] , and then calculate the characteristic peak area ratio K ₂ of ¹³ CO ₂ and N ₂ under various proportioning conditions according to the A ^[13CO2] , the K ₂ = [A ^{[13CO2 ]} /Σ _13CO2 )/A ₂ ^[N2] ; said Σ _13CO2 is ¹³ CO ₂ relative Raman scattering cross section normalization factor; Step 204, taking K2 mentioned in step 203 as the ordinate, and taking the molar ratio C [ ^{13CO2 ]} /C ^[N2] _{of 13CO2} and _N2 as the abscissa to project a graph and perform linear fitting to calculate the fitted straight line The slope of F _13CO2 is obtained; Step 3, using a microscopic laser Raman spectrometer to perform microscopic laser Raman detection on the CO ₂ gas mixed with ¹² CO ₂ and ¹³ CO ₂ to obtain the peak area A _{12CO 2} of the characteristic peak of ¹² CO 2 in the CO ₂ gas and The peak area A _13CO2 ^{of the} characteristic peak of ¹³ CO ₂ , and _{then calculate the 12 CO 2} ^{and 13} The molar ratio of CO ₂ C ^[12CO2] /C ^[13CO2] . 2. Quantitative analysis according to claim 1 The laser Raman detection method of gas carbon isotope composition of _CO2 , it is characterized in that, described in step 102 ^ν-[12CO2] =1287cm _- ¹ , described ν ₊ ^[12CO2] = 1390 cm ^-1 , the ν ^[N2] = 2332 cm ^-1 . 3. The laser Raman detection method for quantitatively analyzing the carbon isotope composition of CO ₂ gas according to claim 1, characterized in that Σ ₁₂ CO 2 =1.49 in step 103. 4. The laser Raman detection method for quantitative analysis of _CO2 gas carbon isotope composition according to claim 1, characterized in that, in step 202, ν _- ^[13CO2] = 1267cm ^-1 , said ν ₊ ^[13CO2] = 1372 cm ^-1 . 5. The laser Raman detection method for quantitatively analyzing the carbon isotope composition of CO ₂ gas according to claim 1, characterized in that Σ ₁₃ CO 2 =1.437 in step 203.