Method for measuring deuterium enrichment in hydrogen-deuterium mixed gas using low-resolution quadrupole mass spectrometer

Abstract

The application discloses a method for measuring the degree of deuteration in hydrogen-deuterium mixed gas by using a low-resolution quadrupole mass spectrometer, which comprises the following steps: (1) drying the hydrogen-deuterium mixed gas to be measured by using color-changing silica gel, and then detecting the hydrogen-deuterium mixed gas by using a low-resolution quadrupole mass spectrometer; (2) inputting the electric signal data detected by the low-resolution quadrupole mass spectrometer into a mathematical correction model for correcting H3 + and H2D + electric signals, so as to calculate the degree of deuteration in the hydrogen-deuterium mixed gas. The application has the advantages of low equipment cost, simple operation, real-time analysis of the degree of deuteration in the hydrogen-deuterium mixed gas, and accurate measurement of the degree of deuteration in the hydrogen-deuterium mixed gas by eliminating the influence of H3 + and H2D + .

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry, and in particular to a method for determining the degree of deuteration in a hydrogen-deuterium mixture using a low-resolution quadrupole gas mass spectrometer. Background Technology

[0002] Deuterium is an isotope of hydrogen, also known as heavy hydrogen. Currently, methods for analyzing hydrogen isotopes include low-temperature gas chromatography (GC) and mass spectrometry (MS). In GC, D2, HD, and H2 are separated using molecular sieves or alumina capillary columns cooled by liquid nitrogen (-95°C), and their deuteration degree is then analyzed using a plasma emission detector (PED). The principle of mass spectrometry analysis of hydrogen isotopes is based on the differences in their mass-to-charge ratios (m / z).

[0003] Among all methods in analytical science, GC has been widely used by researchers for hydrogen isotope analysis and has shown good quantitative results. However, because the chromatographic column needs to be immersed in liquid nitrogen, even small fluctuations in column temperature can cause significant deviations. Furthermore, GC analysis requires large quantities of sample, and most importantly, GC sampling is intermittent; therefore, GC is not suitable for online continuous analysis of trace hydrogen isotopes.

[0004] For the reasons mentioned above, mass spectrometry (MS) analysis shows significant advantages in determining deuteration. A hydrogen-deuterium mixture contains H₂, HD, and D₂. The interactions between the molecules and ions of these three substances produce other isotopic ions. During mass spectrometry analysis, different ions have different effects on the ion current signal (current signal at m / z=2, 3, and 4), as shown in the table below: .

[0005] Among them, H3 + and HD + Isotopic interference of ions will affect the current signal at m / z=3, D2 + and H2D + Isotopic interference from ions will affect the current signal at m / z=4, due to H3 + (m / z=3.023841) and HD + (m / z=3.0215002) and D2 + (m / z=4.027655) and H2D + The mass-to-charge ratios of these particles (m / z=4.029433) are very close, making them indistinguishable by low-resolution mass spectrometers. Therefore, accurate analysis requires high-resolution mass spectrometers, such as sector-field mass spectrometers and triple quadrupole tandem mass spectrometers (resolution > 2000). However, high-resolution mass spectrometers are expensive and complex to operate.

[0006] Therefore, when using low-resolution mass spectrometry to quantitatively determine the deuteration degree of a hydrogen-deuterium mixture, the low-resolution mass spectrometer cannot exclude H3. + H2D + Due to the influence of [the virus / condition], the accuracy of the test results cannot be effectively guaranteed. Summary of the Invention

[0007] To address the aforementioned issues and improve detection accuracy, this invention establishes a correction model based on the deuteration degree and electrical signal data of different samples to eliminate H3. + H2D + The influence of deuteration degree and electrical signal data. Since the relationship between deuteration degree and electrical signal data is not linear, if a conventional linear fitting is used during the model fitting stage, the correction model obtained can only correct the detection results within a very small range. Therefore, this invention uses a nonlinear fitting module to determine the model parameters, and the resulting correction model can be used to determine the deuteration degree in the hydrogen-deuterium mixture gas to be tested in the range of 3%-99.5%.

[0008] The technical solution adopted by this invention to solve its technical problem is: A method for determining the degree of deuteration in a hydrogen-deuterium mixture using a low-resolution quadrupole gas mass spectrometer includes the following steps: S10: Obtain multiple hydrogen-deuterium mixtures with different degrees of deuteration as samples: The deuteration degree C was obtained by detecting the pretreated sample using nuclear magnetic resonance spectroscopy. D样品 ; The sample was analyzed using a low-resolution quadrupole gas mass spectrometer to obtain electrical signal data. S20: Determine the degree of deuteration C corresponding to each of the samples. D样品 And electrical signal data input correction model: Where r1 is the first influence factor, r2 is the second influence factor, K1 is the first correction coefficient, K2 is the second correction coefficient, I2 is the electrical signal of the low-resolution quadrupole gas mass spectrometer at m / z=2, I3 is the electrical signal of the low-resolution quadrupole gas mass spectrometer at m / z=3, and I4 is the electrical signal of the low-resolution quadrupole gas mass spectrometer at m / z=4. Then, the values ​​of r1, r2, K1 and K2 are obtained by fitting through the nonlinear fitting module, and the correction model with determined coefficients is obtained. S30: The hydrogen-deuterium mixture to be tested is passed into a low-resolution quadrupole gas mass spectrometer to detect the electrical signal data, and the correction model determined by the above coefficients is input to calculate the degree of deuteration in the hydrogen-deuterium mixture.

[0009] In the above technical solution, in order to solve the problem that low-resolution mass spectrometry cannot be used to determine the degree of deuteration in a hydrogen-deuterium mixture, it is necessary to determine H3. + and H2D + The influence of this, and the electrical signals at m / z=3 and m / z=4 must be corrected; therefore, a low-resolution mass spectrometer was established for H3. + and H2D + A mathematical correction model for determining the degree of deuteration in a hydrogen-deuterium mixture after electrical signal correction was used, thus eliminating H3. + and H2D + The influence of [the following] was effectively corrected for the electrical signals at m / z=3 and m / z=4. This allows for a simpler and lower-cost method to determine the degree of deuteration in a hydrogen-deuterium mixture. After calculation, r1=1.17987; r2=2.14305; K1=467078.83821; K2=0.99973.

[0010] Furthermore, in S10, the degree of deuteration of the sample is 3.0%-99.5%; in S30, the degree of deuteration of the hydrogen-deuterium mixture to be tested is 3.0%-99.5%.

[0011] Furthermore, in S10, the deuteration degree C of the pretreated sample is determined using nuclear magnetic resonance spectroscopy. D样品 The specific pretreatment process is as follows: After drying the sample with color-changing silica gel, it is passed into a palladium catalyst fixed-bed reactor together with oxygen to obtain water. The deuteration degree of the combined water, i.e., the deuteration degree C of the sample, is determined by nuclear magnetic resonance spectroscopy. D样品 .

[0012] Furthermore, in S20, the nonlinear fitting module is the Origin nonlinear fitting module.

[0013] Furthermore, the low-resolution quadrupole gas mass spectrometer is a PM-QMS online gas mass spectrometer.

[0014] Furthermore, in S30, the injection flow rate of the hydrogen-deuterium mixture to be measured into the low-resolution quadrupole gas mass spectrometer is 1-2 sccm, and excess gas is discharged through the bypass.

[0015] Furthermore, the mass spectrometry parameters of the low-resolution quadrupole gas mass spectrometer are set as follows: capillary temperature: 120℃, chamber temperature: 35℃, capillary voltage: 24V; ion source ionization temperature: 2000℃; baking temperature: 200℃.

[0016] Furthermore, the resolution of the low-resolution quadrupole gas mass spectrometer is less than 1200.

[0017] The beneficial effects of this invention are: it can analyze the deuteration degree in hydrogen-deuterium mixed gas in real time; compared with chromatography and high-resolution mass spectrometry equipment, the low-resolution quadrupole mass spectrometer is easier to operate and has a lower equipment price; it has a wide detection range, capable of detecting hydrogen-deuterium mixed gas with a deuteration degree of 3.0%-99.5%, and the analysis error is less than 1.5%; it can analyze the deuteration degree in hydrogen-deuterium mixed gas at a wide flow rate range (80-500 sccm) without affecting the result error. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a process for determining deuteration degree according to the present invention; Figure 2 This is a graph showing the linear fitting results between the deuteration degree of combined water and the deuteration degree measured in this invention. Detailed Implementation

[0019] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0020] In this invention, unless otherwise specified, all raw materials and equipment used are commercially available or commonly used in the field. Unless otherwise specified, the methods in the following embodiments are conventional methods in the field.

[0021] Example 1: Methods for determining the degree of deuteration in a hydrogen-deuterium mixture using a low-resolution quadrupole gas mass spectrometer, such as... Figure 1 As shown: (1) Eighteen water samples with different deuteration degrees were prepared as external standards and electrolyzed through a proton exchange membrane to obtain corresponding hydrogen-deuterium mixed gases (deuteration degree 3.0%-99.5%). The obtained hydrogen-deuterium mixed gases were dried with color-changing silica gel and then passed into a low-resolution quadrupole gas mass spectrometer (Shanghai Jingpuruo Technology Co., Ltd., PM-QMS online gas mass spectrometer) to obtain mass spectrometry signal data. The injection flow rate was about 1-2 sccm, and the remaining gases were excluded through the bypass. The mass spectrometer capillary was set to 120℃, and the chamber temperature was set to 35℃.

[0022] (2) Mass spectrometry conditions: electron ionization of gas molecules; detection of gas phase products; sample injection: non-condensable gas; capillary temperature: 120℃, chamber temperature setting: 35℃, capillary voltage: 24V; ion source ionization temperature: 2000℃; baking temperature: 200℃.

[0023] (3) The hydrogen-deuterium mixed gas obtained from electrolysis was then introduced into a palladium catalyst fixed-bed reactor (palladium catalyst model D03-XLG2Q2-3 / LA, manufacturer: Shaanxi Ruike New Material Co., Ltd., palladium content 0.3 wt%, dosage 370g) at a flow rate of 500 sccm. The corresponding water was obtained by chemical reaction at 560℃, and its deuteration degree was analyzed by nuclear magnetic resonance spectroscopy (NMR) to obtain the deuteration degree data of the external standard sample.

[0024] (4) Model building process: The contributions of different ions to the ion current signals (current signals at m / z=2, 3, and 4) are shown in the table below. Since the contribution of monatomic ions is very small, it can be ignored.

[0025] .

[0026] Among them, H3 + H2D + The following reactions were performed in the ion source of the mass spectrometer: H2+ H2 + ⇌H3 + + H-form (I) H2+ HD + ⇌H2D + + H-type (II) H2+ D2 + ⇌H2D + + H type (III) HD+HD + ⇌H2D + + D type (IIII) According to equation (I), Equations (II), (III), and (IIII) will eventually reach equilibrium in the system. Using equation (IIII) for calculation: Combined equations 1-5 to obtain Among them, C D The deuteration degree / ppm of the hydrogen-deuterium mixture gas obtained by NMR measurement of the combined water in step (3) is given. I2 is the electrical signal from the mass spectrometer at m / z=2 / [A] I3 is the electrical signal from the mass spectrometer at m / z=3 / [A] I4 is the electrical signal from the mass spectrometer at m / z=4 / [A] S2 is the electrical signal response factor of the mass spectrometer at m / z=2. S3 is the electrical signal response factor of the mass spectrometer at m / z=3. S4 is the electrical signal response factor of the mass spectrometer at m / z=4. K1 is H3 + The correction factor for the I3 signal, K2 is H2D + Correction coefficients for the I4 signal.

[0027] (5) The degree of deuteration C corresponding to each sample D样品 and electrical signal data (I 2样品 I 3样品 I 4样品 Input the above correction model, and use the Origin nonlinear fitting module to determine the model parameters of the correction model: The first impact factor r1 = S2 / S3 = 1.17987; The second impact factor r2 = S2 / S4 = 2.14305; The first correction factor K1 = 467078.83821; The first correction factor K2 = 0.99973.

[0028] Example 2: A method for determining the degree of deuteration in a hydrogen-deuterium mixture using a low-resolution quadrupole gas mass spectrometer includes the following steps: (1) The hydrogen-deuterium mixture to be tested is first dried with color-changing silica gel, and then enters a low-resolution quadrupole gas mass spectrometer (Shanghai Jingpuruo Technology Co., Ltd., PM-QMS online gas mass spectrometer, resolution less than 100) for detection. The injection flow rate is about 1-2 sccm, and the excess gas is discharged from the bypass. The mass spectrometry parameters of the low-resolution quadrupole gas mass spectrometer are set as follows: capillary temperature: 120℃, chamber temperature setting: 35℃, capillary voltage: 24V; ion source ionization temperature: 2000℃; baking temperature: 200℃.

[0029] (2) Input the electrical signal data of the low-resolution quadrupole gas mass spectrometer into the correction model to calculate the degree of deuteration in the hydrogen-deuterium mixture; The correction model is as follows: Where r1=1.17987; r2=2.14305; K1=467078.83821; K2=0.99973.

[0030] Among them, C D The deuteration degree in the hydrogen-deuterium mixture to be tested is expressed in ppm. I2 is the electrical signal from the mass spectrometer at m / z=2 / [A] I3 is the electrical signal from the mass spectrometer at m / z=3 / [A] I4 is the electrical signal [A] of the mass spectrometer at m / z=4.

[0031] Example 3: A mixture of H2-D2 gas and oxygen was introduced into a palladium-catalyst fixed-bed reactor to react and produce water with the corresponding degree of deuteration. The method was then validated by comparing the results obtained by quadrupole mass spectrometry (QMS) with those obtained by nuclear magnetic resonance spectroscopy (NMR). The specific measurement results are shown in Table 1.

[0032] Table 1. Measurement results for samples 1 to 18: .

[0033] The deuteration degree (mass spectrometry) results of 18 external standard samples from Example 1 were obtained using the method of this invention (sixth column). Then, the 18 external standard samples were combined into water and analyzed by nuclear magnetic resonance (NMR) spectroscopy to obtain the deuteration degree (NMR) / [ppm] of the combined water (second column). We observed that the results obtained by the method of this invention are consistent with the NMR analysis results, with a relative error of less than 1.5% in the deuteration degree analysis. The deuteration degree of the combined water shows a linear correlation with the deuteration degree measured by this invention, and the linear regression coefficient (R0) is... 2 The accuracy of the method of the present invention is 0.99994, indicating that the method has high detection accuracy.

[0034] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A method for determining the degree of deuteration in a hydrogen-deuterium mixture using a low-resolution quadrupole gas mass spectrometer, characterized in that, Includes the following steps: S10: Obtain multiple hydrogen-deuterium mixtures with different degrees of deuteration as samples: The deuteration degree C was obtained by detecting the pretreated sample using nuclear magnetic resonance spectroscopy. D样品 ; The sample was analyzed using a low-resolution quadrupole gas mass spectrometer to obtain electrical signal data. S20: Determine the degree of deuteration C corresponding to each of the samples. D样品 And electrical signal data input correction model: Where r1 is the first influence factor, r2 is the second influence factor, K1 is the first correction coefficient, K2 is the second correction coefficient, I2 is the electrical signal of the low-resolution quadrupole gas mass spectrometer at m / z=2, I3 is the electrical signal of the low-resolution quadrupole gas mass spectrometer at m / z=3, and I4 is the electrical signal of the low-resolution quadrupole gas mass spectrometer at m / z=4. Then, the values ​​of r1, r2, K1 and K2 are obtained by fitting through the nonlinear fitting module, and the correction model with determined coefficients is obtained. S30: The hydrogen-deuterium mixture to be tested is passed into a low-resolution quadrupole gas mass spectrometer to detect the electrical signal data, and the correction model determined by the above coefficients is input to calculate the degree of deuteration of the hydrogen-deuterium mixture. In S10, the deuteration degree of the sample is 3.0%-99.5%; in S30, the deuteration degree of the hydrogen-deuterium mixture to be tested is 3.0%-99.5%. In S10, the deuteration degree C of the pretreated sample was determined using nuclear magnetic resonance spectroscopy. D样品 The specific pretreatment process is as follows: After drying the sample with color-changing silica gel, it is passed into a palladium catalyst fixed-bed reactor together with oxygen to obtain water. The deuteration degree of the combined water, i.e., the deuteration degree C of the sample, is determined by nuclear magnetic resonance spectroscopy. D样品 .

2. The method according to claim 1, characterized in that, In S20, the nonlinear fitting module is the Origin nonlinear fitting module.

3. The method according to claim 1, characterized in that, The low-resolution quadrupole gas mass spectrometer is a PM-QMS online gas mass spectrometer.

4. The method according to claim 1, characterized in that, In S30, the injection flow rate of the hydrogen-deuterium mixture to be measured into the low-resolution quadrupole gas mass spectrometer is 1-2 sccm, and excess gas is discharged through the bypass.

5. The method according to claim 1, characterized in that, The mass spectrometry parameters of the low-resolution quadrupole gas mass spectrometer are set as follows: capillary temperature: 120 ℃, chamber temperature: 35 ℃, capillary voltage: 24V; ion source ionization temperature: 2000℃; baking temperature: 200℃.

6. The method according to claim 1, characterized in that, The resolution of the low-resolution quadrupole gas mass spectrometer is less than 1200.

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