Method for measuring deuteration degree in hydrogen-deuterium mixed gas by using low-resolution quadrupole type gas mass spectrometer

Abstract

The invention discloses a method for measuring the deuteration degree of hydrogen-deuterium mixed gas by using a low-resolution quadrupole type gas mass spectrometer, which comprises the following steps: (1) drying the hydrogen-deuterium mixed gas to be measured by allochroic silica gel, and then detecting the hydrogen-deuterium mixed gas in the low-resolution quadrupole type gas mass spectrometer; and (2) inputting electric signal data detected by the low-resolution quadrupole rod type gas mass spectrometer into the mathematical correction model after correcting the H3 + and H2D + electric signals so as to calculate the deuteration degree in the hydrogen-deuterium mixed gas. The device is low in price and simpler to operate, the deuteration degree in the hydrogen-deuterium mixed gas can be analyzed in real time, and the influence of H3 + and H2D + can be eliminated, so that the deuteration degree in the hydrogen-deuterium mixed gas is accurately measured.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry, and in particular to a method for measuring the deuterium substitution degree in a hydrogen-deuterium mixed gas by using a low-resolution quadrupole gas mass spectrometer. Background Art

[0002] Deuterium is an isotope of hydrogen, also known as heavy hydrogen. Current methods for analyzing hydrogen isotopes include cryogenic gas chromatography (GC) and mass spectrometry (MS). The GC method uses a molecular sieve or alumina capillary column cooled by liquid nitrogen (-95°C) to separate D₂, H₂, and H₂. The deuterium substitution is then analyzed using a plasma emission detector (PED). The principle of hydrogen isotope analysis by mass spectrometry is based on differences in their mass-to-charge ratios (m / z).

[0003] Among all analytical methods, GC has been widely used by researchers for hydrogen isotope analysis, demonstrating excellent quantitative results. However, because the chromatographic column must be immersed in liquid nitrogen, even small fluctuations in column temperature can cause significant deviations. Furthermore, GC analysis requires large sample volumes, and most importantly, GC sampling is intermittent, making it unsuitable for online, continuous analysis of trace hydrogen isotopes.

[0004] For these reasons, mass spectrometry (MS) analysis demonstrates significant advantages in the determination of deuterium substitution. A hydrogen-deuterium mixture contains three substances: H₂, HD₂, and D₂. The interactions between the molecules and ions of these three substances produce ions of other isotopes. During mass spectrometry analysis, different ions have varying effects on the ion current signal (the current signal at m / z = 2, 3, and 4), as shown in the table below: .

[0005] Among them, H3 + and HD + Isobaric interference of ions will affect the m / z=3 current signal, D2 + and H2D + Isobaric interference of ions will affect the current signal of m / z=4. + (m / z=3.023841)and HD + (m / z=3.0215002) and D2 + (m / z=4.027655) and H2D + The mass-to-charge ratio of (m / z=4.029433) is very close and cannot be distinguished by low-resolution mass spectrometers. Therefore, accurate analysis requires a high-resolution mass spectrometer, such as a sector-field mass spectrometer and a triple quadrupole tandem mass spectrometer (resolution > 2000). However, high-resolution mass spectrometers are expensive and complex to operate.

[0006] Therefore, when low-resolution mass spectrometry is used to determine the deuterium substitution degree of hydrogen-deuterium mixture, the low-resolution mass spectrometer cannot exclude H3 + 、H2D + The accuracy of the test results cannot be effectively guaranteed. Summary of the Invention

[0007] In order to solve the above problems and improve the accuracy of detection, the present invention establishes a correction model based on the deuteration degree and electrical signal data of different samples to eliminate H3 + 、H2D + Because the relationship between deuterium substitution and electrical signal data is not linear, the correction model obtained by conventional linear fitting during model fitting can only correct the detection results within a very small range. Therefore, the present invention uses a nonlinear fitting module to determine the model parameters. The resulting correction model can be used to measure the deuterium substitution in hydrogen-deuterium mixed gases with a deuterium substitution degree within the range of 3%-99.5%.

[0008] The technical solution adopted by the present invention to solve its technical problem is: A method for measuring the deuterium content in a hydrogen-deuterium mixed gas using a low-resolution quadrupole gas mass spectrometer comprises the following steps: S10: Obtain multiple hydrogen-deuterium mixed gases with different deuterium substitution degrees as samples: The deuterated degree C was obtained by using a nuclear magnetic resonance spectrometer to detect the pre-treated samples. D样品 ; Using a low-resolution quadrupole gas mass spectrometer to detect the sample to obtain electrical signal data; S20: Deuterium substitution degree C corresponding to each sample D样品 And electrical signal data input correction model: , where r1 is the first influencing factor, r2 is the second influencing factor, K1 is the first correction coefficient, K2 is the second correction coefficient, I2 is the electrical signal of a low-resolution quadrupole gas mass spectrometer with m / z=2, I3 is the electrical signal of a low-resolution quadrupole gas mass spectrometer with m / z=3, and I4 is the electrical signal of a low-resolution quadrupole gas mass spectrometer with m / z=4; Then, the values ​​of r1, r2, K1 and K2 are obtained by fitting through the nonlinear fitting module to obtain the correction model with determined coefficients; S30: Passing the hydrogen-deuterium mixed gas to be measured into a low-resolution quadrupole gas mass spectrometer to detect and obtain electrical signal data, and inputting the data into a correction model determined by the above coefficients to calculate the deuterium substitution degree in the hydrogen-deuterium mixed gas.

[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 hydrogen-deuterium mixed gas, it is necessary to determine H3 + and H2D + The influence of m / z=3 and m / z=4 must be corrected, so a low-resolution mass spectrometer was established to calibrate the H3 + and H2D + The mathematical correction model for determining the deuterium substitution degree in hydrogen-deuterium mixed gas after electrical signal correction is used to exclude H3 + and H2D + The effect of the ionization process was eliminated, effectively correcting the electrical signals at m / z = 3 and m / z = 4. This enabled a simpler and more cost-effective method for determining the degree of deuteration in hydrogen-deuterium mixtures. The calculations yielded r1 = 1.17987; r2 = 2.14305; K1 = 467078.83821; and K2 = 0.99973.

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

[0011] Furthermore, in S10, the pre-treated sample is detected using a nuclear magnetic resonance spectrometer to obtain the deuterated degree C D样品 The specific pre-treatment process is as follows: the sample is dried on color-changing silica gel, and then introduced into a palladium catalyst fixed bed reactor together with oxygen to obtain the corresponding water. The deuterium degree of the combined water is measured by nuclear magnetic resonance spectrometer to obtain the deuterium degree C of the sample. D样品 .

[0012] Furthermore, in S20, the nonlinear fitting module is an 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 mixed gas to be measured into the low-resolution quadrupole gas mass spectrometer is 1-2 sccm, and excess gas is discharged from the bypass.

[0015] Furthermore, the mass spectrometry parameters of the low-resolution quadrupole gas mass spectrometer were set as follows: capillary temperature: 120°C, cavity temperature setting: 35°C, capillary voltage: 24V; ion source ionization temperature: 2000°C; and baking temperature: 200°C.

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

[0017] The beneficial effects of the present invention are: it can analyze the deuterium substitution 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 the equipment is cheaper; it has a wide detection range and can detect hydrogen-deuterium mixed gas with a deuterium substitution degree within the range of 3.0%-99.5%, and the analysis error is less than 1.5%; it can analyze the deuterium substitution degree in hydrogen-deuterium mixed gas within a wide flow range (80-500 sccm) without affecting the result error. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a process flow for determining the degree of deuteration of the present invention; Figure 2 It is a linear fitting result diagram of the deuterium substitution degree of combined water and the deuterium substitution degree measured by the present invention. DETAILED DESCRIPTION

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

[0020] In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the following examples, unless otherwise specified, are all conventional methods in the art.

[0021] Example 1: Method for determining the degree of deuterium in hydrogen-deuterium mixed gas using a low-resolution quadrupole gas mass spectrometer, such as Figure 1 As shown: (1) 18 water samples with different deuterated degrees were prepared as external standards and the corresponding hydrogen-deuterium mixed gas (3.0%-99.5% deuterated degree) was obtained by proton exchange membrane electrolysis. The obtained hydrogen-deuterium mixed gas was 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 approximately 1-2 sccm, and the remaining gas was discharged through the bypass. The mass spectrometer capillary temperature was set to 120°C and the cavity temperature was set to 35°C.

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

[0023] (3) The hydrogen-deuterium mixed gas obtained by electrolysis was then introduced into a palladium catalyst fixed bed reactor (palladium catalyst model D03-XLG2Q2-3 / LA, manufacturer: Shaanxi Ruike New Materials Co., Ltd., palladium content 0.3 wt%, amount 370 g) at a flow rate of 500 sccm. The corresponding water was reacted at 560°C, 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 following table shows the contributions of different ions to the ion current signal (current signals at m / z = 2, 3, and 4). Since the contribution of monatomic ions is very small, it can be ignored.

[0025] .

[0026] Among them, H3 + 、H2D + In the ion source of the mass spectrometer, the following reactions are performed: H2+ H2 + ⇌H3 + + H formula (I) H2+ HD + ⇌H2D + + H formula (II) H2+ D2 + ⇌H2D + + H formula (III) HD+HD + ⇌H2D + + D-type (IIII) According to formula (I), Formula (II), formula (III), and formula (IIII) will eventually reach equilibrium in the system. Formula (IIII) can be used to calculate: Combine 1-5 to get Among them, C D is the deuterium substitution degree of the hydrogen-deuterium mixed gas measured by NMR in step (3) / ppm I2 is the electrical signal of mass spectrometer m / z=2 / [A] I3 is the electrical signal of mass spectrometer m / z=3 / [A] I4 is the electrical signal of mass spectrometer m / z=4 / [A] S2 is the mass spectrometer's electrical signal response factor at m / z=2 S3 is the mass spectrometer's electrical signal response factor at m / z=3 S4 is the mass spectrometer's electrical signal response factor at m / z=4 K1 is H3 + Correction coefficient for I3 signal, K2 is H2D + Correction factor for I4 signal.

[0027] (5) The deuterium substitution degree 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 determine the model parameters of the correction model through the Origin nonlinear fitting module: The first impact factor r1=S2 / S3=1.17987; The second impact factor r2=S2 / S4=2.14305; The first correction coefficient K1=467078.83821; The first correction coefficient K2=0.99973.

[0028] Example 2: A method for measuring the deuterium content in a hydrogen-deuterium mixed gas using a low-resolution quadrupole gas mass spectrometer comprises the following steps: (1) The hydrogen-deuterium mixed gas to be tested was first dried by color-changing silica gel and then entered into 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 was about 1-2 sccm, and the excess gas was discharged from the bypass. The mass spectrometry parameters of the low-resolution quadrupole gas mass spectrometer were set as follows: capillary temperature: 120°C, cavity temperature setting: 35°C, capillary voltage: 24V; ion source ionization temperature: 2000°C; baking temperature: 200°C.

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

[0030] Among them, C D Deuterium substitution degree in the hydrogen-deuterium mixed gas to be measured / ppm I2 is the electrical signal of mass spectrometer m / z=2 / [A] I3 is the electrical signal of mass spectrometer m / z=3 / [A] I4 is the electrical signal of mass spectrometer m / z=4 / [A].

[0031] Example 3: A H₂-D₂ gas mixture, along with oxygen, was introduced into a palladium-catalyzed fixed-bed reactor, where it reacted to 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). Specific measurement results are shown in Table 1.

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

[0033] The 18 external standard samples of Example 1 were analyzed using the method of the present invention to obtain the deuteration degree (mass spectrometry) measurement results (the sixth column). The 18 external standard samples were then subjected to nuclear magnetic resonance (NMR) spectroscopy to obtain the deuteration degree of combined water (NMR) / [ppm] (the second column). We observed that the results determined by the method of the present invention were consistent with the results of the NMR analysis, and the relative error of the deuteration degree analysis was less than 1.5%. The deuteration degree of combined water and the deuteration degree determined by the present invention showed a linear correspondence, and the linear fitting regression coefficient (R 2 ) is 0.99994, indicating that the method of the present invention has high detection accuracy.

[0034] The embodiment described above is only a preferred solution of the present invention and does not limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solution described in the claims.

Claims

1. A method for measuring the degree of deuterium in a hydrogen-deuterium mixed gas using a low-resolution quadrupole gas mass spectrometer, characterized in that: The steps include: S10: Obtain multiple hydrogen-deuterium mixed gases with different deuterium substitution degrees as samples: The deuterated degree C was obtained by using a nuclear magnetic resonance spectrometer to detect the pre-treated samples. D样品 ; Using a low-resolution quadrupole gas mass spectrometer to detect the sample to obtain electrical signal data; S20: Deuterium substitution degree C corresponding to each sample D样品 And electrical signal data input correction model: , where r1 is the first influencing factor, r2 is the second influencing factor, K1 is the first correction coefficient, K2 is the second correction coefficient, I2 is the electrical signal of a low-resolution quadrupole gas mass spectrometer with m / z=2, I3 is the electrical signal of a low-resolution quadrupole gas mass spectrometer with m / z=3, and I4 is the electrical signal of a low-resolution quadrupole gas mass spectrometer with m / z=4; Then, the values ​​of r1, r2, K1 and K2 are obtained by fitting through the nonlinear fitting module to obtain the correction model with determined coefficients; S30: Passing the hydrogen-deuterium mixed gas to be tested into a low-resolution quadrupole gas mass spectrometer to detect and obtain electrical signal data, and inputting the data into a correction model determined by the above coefficients to calculate the deuterium degree of the hydrogen-deuterium mixed gas.

2. The method according to claim 1, characterized in that In S10, the deuterium substitution degree of the sample is 3.0%-99.5%; and in S30, the deuterium substitution degree of the hydrogen-deuterium mixed gas to be measured is 3.0%-99.5%.

3. The method according to claim 2, characterized in that In S10, the pre-treated sample is detected using a nuclear magnetic resonance spectrometer to obtain the deuterated degree C D样品 The specific pre-treatment process is as follows: the sample is dried on color-changing silica gel, and then introduced into a palladium catalyst fixed bed reactor together with oxygen to obtain the corresponding water. The deuterium degree of the combined water is measured by nuclear magnetic resonance spectrometer to obtain the deuterium degree C of the sample. D样品 .

4. The method according to claim 1, wherein In S20, the nonlinear fitting module is an Origin nonlinear fitting module.

5. The method according to claim 1, wherein The low-resolution quadrupole gas mass spectrometer is a PM-QMS online gas mass spectrometer.

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

7. The method according to claim 1, characterized in that The mass spectrometry parameters of the low-resolution quadrupole gas mass spectrometer were set as follows: capillary temperature: 120 °C, cavity temperature: 35 °C, capillary voltage: 24 V; ion source ionization temperature: 2000 °C; and bakeout temperature: 200 °C.

8. 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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