Data correction method for measuring hydrogen and oxygen isotope components of plant water

Abstract

The invention belongs to the technical field of isotope analysis, and particularly relates to a data correction method for measuring hydrogen and oxygen isotope components of plant water. The data correction method for measuring the hydrogen and oxygen isotope components of the plant water comprises the following steps: performing isotope spectrum measurement on the plant water to be measured to obtain delta18O plant water, delta2H plant water and residual R plant water; obtaining the corrected delta18O plant water in the to-be-detected plant water according to the correction curve formula 1; obtaining the corrected delta2H plant water in the plant water to be detected according to the correction curve formula 2; delta < 18 > O plant water correction = delta < 18 > O plant water-Y1 formula 1; delta 2H plant water correction = delta 2H plant water-Y2 formula 2. The correction method provided by the invention is simple to use, is widely applicable to the process of measuring the hydrogen and oxygen isotope component in the plant water by an isotope spectrometer, and can greatly improve the accuracy of a measurement result.

Description

Technical Field

[0001] The invention belongs to the technical field of isotope analysis, and in particular relates to a data correction method for determining hydrogen and oxygen isotope components of plant water. Background Art

[0002] Stable hydrogen and oxygen isotopes in plant leaves, stems, and soil water serve as key tracers for studying soil-plant-atmosphere ecohydrological processes. Studying these isotopes is of great ecological significance. However, during the vacuum and low-temperature extraction process, methanol (MeOH), which has spectral absorption peaks similar to those of water molecules, is often introduced into plants and soils, causing spectral contamination and isotope measurement errors. Recent advances in stable isotope infrared spectroscopy have provided new opportunities for the rapid determination of hydrogen and oxygen isotopes in plant and soil water. The Picarro L2140-i, with its superior drift performance and faster response time, is widely used for high-precision measurement and research of the three oxygen isotopes in water. The Picarro L2140-i measurement principle utilizes cavity ring-down spectroscopy (CRDS) technology, a stable isotope infrared spectrometer, to achieve an effective measurement path length of up to 20 kilometers in a compact chamber, providing exceptional accuracy and sensitivity. It primarily consists of an autosampler, vacuum pump, autosampler, high-precision vaporization unit, continuous sampling device, and micro-combustion module. During measurement, the autosampler injects 0.2μL of water sample from an analysis vial into the vaporization chamber for processing before entering the spectrometer for measurement. Throughout the measurement process, a customized injection port and continuous high-purity nitrogen carrier gas are used to effectively eliminate memory effects and ensure the independence of each measurement. The measurement results are calculated to determine the hydrogen and oxygen isotope values ​​in the water. Plant water contains methanol (MeOH), which causes spectral contamination and thus leads to isotope measurement errors. At present, for the treatment of methanol substances in plant and soil water, activated carbon adsorption method is generally used to remove some organic pollutants in water samples, but this method fails to significantly improve the measurement error. Therefore, it is of great significance to explore the numerical calibration curve of hydrogen and oxygen isotopes in plant water.

[0003] In summary, the difficulties in the existing technology are: 1) how to scientifically and reasonably correct the measurement results based on the test; 2) how to test the corrected results, and ultimately ensure the scientificity and accuracy of the results from these two aspects. Summary of the Invention

[0004] The purpose of the present invention is to provide a data correction method for determining the hydrogen and oxygen isotope components of plant water. The method provided by the present invention can accurately obtain δ 18 O 植物水 and δ 2 H 植物水 .

[0005] In order to achieve the above object, the present invention provides the following technical solutions: The present invention provides a data correction method for determining the hydrogen and oxygen isotope compositions of plant water, comprising the following steps: The plant water to be tested is subjected to isotope spectroscopy to obtain δ 18 O 植物水 , δ 2 H 植物水 and residual R 植物水 ; According to the calibration curve formula 1, the δ 18 O 植物水 ; According to the calibration curve formula 2, the δ 2 H 植物水 ; δ 18 O 植物水校正 =δ 18 O 植物水 -Y1 (Formula 1); Y1=6.254×R-15.797 (Formula 1-1); δ 2 H 植物水校正 =δ 2 H 植物水 -Y2 (Formula 2); Y2=10.4×R-27.994 (Formula 2-1); In formula 1-1 and formula 2-1, R is the residual R 植物水 .

[0006] Preferably, the isotope spectrum measurement uses N2 as the reference gas.

[0007] Preferably, the acquisition of Formula 1-1 and Formula 2-1 includes the following steps: The isotope spectrum of pure water is measured to obtain the δ 18 O 水 , δ 2 H 水 and residual R 水 ; δ in a series of methanol aqueous solutions 18 O 甲醇溶液 , δ 2 H 甲醇溶液 and residual R 甲醇溶液 ; The first series difference is the vertical axis, and the residual R of each concentration of methanol aqueous solution is 甲醇溶液 As the horizontal axis, linear fitting is performed to obtain formula 1-1; the first series of residual differences are δ 18 O甲醇溶液 and δ 18 O 水 The difference between The second series difference is the vertical axis, and the residual R of each concentration of methanol aqueous solution is 甲醇溶液 As the horizontal axis, linear fitting is performed to obtain formula 2-1; the second series difference is the δ of each concentration of methanol aqueous solution 2 H 甲醇溶液 and δ 2 H 水 The difference.

[0008] Preferably, the concentration of the methanol aqueous solution is 80~800μL·L -1 .

[0009] Preferably, the concentration gradient of the series of methanol aqueous solutions is 800 μL·L -1 , 727μL·L -1 , 667μL·L -1 , 533μL·L -1 , 400μL·L -1 , 320μL·L -1 , 267μL·L -1 , 200μL·L -1 , 133μL·L -1 , 100μL·L -1 and 80 μL·L -1 .

[0010] Preferably, the plant water comprises methanol, ethanol and water; the concentration of the methanol is in the range of 80 μL·L -1 ~800μL·L -1 between.

[0011] Preferably, the isotope spectrum measurement conditions include a room temperature of 25°C and a vaporization chamber temperature of 110°C.

[0012] Preferably, the isotope spectrometry is performed on a Picarro L2140-i instrument.

[0013] Preferably, the plant water is liquid water extracted from plant stems or leaves.

[0014] Preferably, the extraction is carried out in a vacuum condensation extraction system with a cold trap temperature of -95°C, a heating temperature of 120°C, a vacuum degree of less than 1500 Pa, and a heating time of 120 minutes.

[0015] The present invention provides a data correction method for determining the hydrogen and oxygen isotope components of plant water, which obtains δ 18 O 植物水 , δ2 H 植物水 and residual R; according to the calibration curve formula 1 and formula 2, the δ 18 O 植物水 , δ 2 H 植物水 The calibration method of the present invention is simple to use and is widely applicable to the determination of hydrogen and oxygen isotope components in extracted plant water using an isotope spectrometer. It is particularly suitable for the determination of stable hydrogen and oxygen isotope results using the Picarro L2140-i instrument. It can significantly improve the accuracy of the measurement results and minimize the impact of methanol on the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a flow chart of the data correction method for determining the hydrogen and oxygen isotope components of plant water provided by the present invention. DETAILED DESCRIPTION

[0018] The present invention provides a data correction method for determining the hydrogen and oxygen isotope compositions of plant water, comprising the following steps: The plant water to be tested is subjected to isotope spectroscopy to obtain δ 18 O 植物水 , δ 2 H 植物水 and residual R 植物水 ; According to the calibration curve formula 1, the δ 18 O 植物水 ; According to the calibration curve formula 2, the δ 2 H 植物水 ; δ 18 O 植物水校正 =δ 18 O 植物水 -Y1 (Formula 1); Y1=6.254×R-15.797 (Formula 1-1); δ 2 H 植物水校正 =δ 2 H 植物水 -Y2 (Formula 2); Y2=10.4×R-27.994 (Formula 2-1); In formula 1-1 and formula 2-1, R is the residual R 植物水 .

[0019] In one embodiment of the present invention, the plant water is liquid water extracted from plant stems or leaves. The extraction can be performed in a vacuum condensation extraction system. The parameters set for the vacuum condensation extraction system may include: cold trap temperature: -95°C, heating temperature: 120°C, vacuum degree less than 1500 Pa, and heating time: 120 minutes. The model of the vacuum condensation extraction system may be BJJL-2100.

[0020] As an embodiment of the present invention, the isotope spectrum measurement can use N2 as a reference gas.

[0021] As an embodiment of the present invention, the acquisition of Formula 1-1 and Formula 2-1 includes the following steps: The isotope spectrum of pure water is measured to obtain the δ 18 O 水 , δ 2 H 水 and residual R 水 ; δ in a series of methanol aqueous solutions 18 O 甲醇溶液 , δ 2 H 甲醇溶液 and residual R 甲醇溶液 ; The first series difference is the vertical axis, and the residual R of each concentration of methanol aqueous solution is 甲醇溶液 As the horizontal axis, linear fitting is performed to obtain the correction curve formula 1; the first series difference is the δ of each concentration of methanol aqueous solution 18 O 甲醇溶液 and δ 18 O 水 The difference between The second series difference is the vertical axis, and the residual R of each concentration of methanol aqueous solution is 甲醇溶液 As the horizontal axis, linear fitting is performed to obtain the correction curve formula 2; the first series difference is the δ of each concentration of methanol aqueous solution 2 H 甲醇溶液 and δ 2 H 水 The difference.

[0022] Figure 1 This is a flow chart of the data correction method for determining the hydrogen and oxygen isotope components of plant water provided by the present invention.

[0023] As an embodiment of the present invention, when isotope spectra are measured, each sample (pure water or methanol aqueous solutions of various concentrations) is preferably tested multiple times and an average value is taken.

[0024] As an embodiment of the present invention, the concentration of the methanol aqueous solution can be 80~800μL·L -1 Specifically, the concentration gradient of the series of methanol aqueous solutions can be 800 μL·L -1 , 727μL·L -1 , 667μL·L -1 , 533μL·L -1 , 400μL·L -1 , 320μL·L -1 , 267μL·L -1 , 200μL·L -1 , 133μL·L -1 , 100μL·L -1 and 80 μL·L -1 As an embodiment of the present invention, the purity of methanol in the methanol aqueous solution may be 99.9% chromatographically pure grade.

[0025] In order to further illustrate the present invention, the scheme of the present invention is described in detail below with reference to the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0026] Example 1 The hydrogen and oxygen isotopes of pure water samples were tested using an isotope spectrometer. Two replicates were set up, with 6 injections each time. The average of the values ​​of the last three injections (no memory effect, i.e., Ignore = 0) was taken to obtain the δ 18 O 水 , δ 2 H 水 and residual R 水 , the results are shown in Table 1, and the average value of the hydrogen and oxygen isotopes of pure water is obtained, that is, δ 18 O 水 = -7.40‰, δ 2 H 水 = -58.4‰.

[0027] Table 1 δ in pure water 18 O 水 , δ 2 H 水 and residual R 水

[0028] Note: Ignore (-1 indicates memory effect, 0 indicates normal).

[0029] (2) Mix chromatographic grade methanol and water to obtain a concentration gradient of 800 μL·L -1 , 727μL·L -1 , 667μL·L-1 , 533μL·L -1 , 400μL·L -1 , 320μL·L -1 , 267μL·L -1 , 200μL·L -1 , 133μL·L -1 , 100μL·L -1 and 80 μL·L -1 A series of methanol aqueous solutions with different concentrations were prepared. Two replicates were set for each concentration of methanol aqueous solution. Each concentration of methanol aqueous solution was measured six times. The average of the last three injections (without memory effect) was taken to obtain the δ 18 O 甲醇溶液 , δ 2 H 甲醇溶液 and the residual R 甲醇溶液 , the results are shown in Table 2.

[0030] Table 2 δ of methanol aqueous solution at various concentrations 18 O 甲醇溶液 , δ 2 H 甲醇溶液 and residual R 甲醇溶液

[0031] At each concentration, δ 18 O 甲醇溶液 -δ 18 O 水 The difference 1 is the vertical coordinate, and the residual R at each concentration 甲醇溶液 As the horizontal axis, linear fitting is performed, and the determination coefficient R of the fitting equation 2 = 0.9166, we get Y1=6.254×R-15.797 (Equation 1-1); At each concentration, δ 2 H 甲醇溶液 -δ 2 H 水 The difference 2 is the vertical axis, and the residual R at each concentration 甲醇溶液 As the horizontal axis, linear fitting is performed, and the determination coefficient R of the fitting equation 2 = 0.9612, and we get Y2=10.4×R-27.994 (Equation 2-1).

[0032] The method of the present invention was used to analyze the hydrogen and oxygen isotope values ​​of methanol solutions of different concentrations, and each concentration of methanol solution was measured twice, with 6 injections each time, and the average value of the isotope values ​​of the last three injections was taken as the measured value of stable hydrogen and oxygen isotopes. 甲醇溶液 Perform linear fitting and the R value of the calibration curve is 2The value exceeded 0.9, demonstrating a good linear relationship. The isotope values ​​after methanol-water solution correction reduced the difference with the isotope values ​​of pure water, eliminating the influence of methanol in the solution, and the data correction achieved ideal results.

[0033] Example 2 Obtaining plant water: The plant stems are extracted in a vacuum condensation extraction system BJJL-2100. The parameters set for the vacuum condensation extraction system can be: cold trap temperature: -95°C, heating temperature: 120°C, vacuum degree: 1000Pa, heating time: 120 minutes, to obtain the plant water S01 to be tested.

[0034] Take the plant water SO1 to be tested and perform isotope spectrum determination (high-purity N2 as carrier gas), and the test results are δ 18 O 植物水 , δ 2 H 植物水 , according to formula 1 (δ 18 O 植物水校正 =δ 18 O 植物水 -Y1), calculate the δ after water correction of the plant to be tested 18 O is -9.26‰; according to formula 2 (δ 2 H 植物水校正 =δ 2 H 植物水 -Y2), calculate the δ after water correction of the plant to be tested 2 H 植物水 The results are shown in Table 3.

[0035] Table 3 Data correction examples for isotope spectrometry of plant water

[0036] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A data correction method for determining the hydrogen and oxygen isotope compositions of plant water, comprising the following steps: The plant water to be tested is subjected to isotope spectroscopy to obtain δ 18 O 植物水 , δ 2 H 植物水 and residual R 植物水 ; According to the calibration curve formula 1, the δ 18 O 植物水 ; According to the calibration curve formula 2, the δ 2 H 植物水 ; δ 18 O 植物水校正 =δ 18 O 植物水 -Y1 (Formula 1); Y1=6.254×R-15.797 (Formula 1-1); δ 2 H 植物水校正 =δ 2 H 植物水 -Y2 (Equation 2); Y2=10.4×R-27.994 (Formula 2-1); In formula 1-1 and formula 2-1, R is the residual R 植物水 .

2. The data correction method according to claim 1, wherein: The isotope spectrum determination uses N2 as the reference gas.

3. The data correction method according to claim 1, wherein: The acquisition of Formula 1-1 and Formula 2-1 includes the following steps: The isotope spectrum of pure water is measured to obtain the δ 18 O 水 , δ 2 H 水 and residual R 水 ; δ in a series of methanol aqueous solutions 18 O 甲醇溶液 , δ 2 H 甲醇溶液 and residual R 甲醇溶液 ; The first series difference is the vertical axis, and the residual R of each concentration of methanol aqueous solution is 甲醇溶液 As the horizontal axis, linear fitting is performed to obtain formula 1-1; the first series of residual differences are δ 18 O 甲醇溶液 and δ 18 O 水 The difference between The second series difference is the vertical axis, and the residual R of each concentration of methanol aqueous solution is 甲醇溶液 As the horizontal axis, linear fitting is performed to obtain formula 2-1; the second series difference is the δ of each concentration of methanol aqueous solution 2 H 甲醇溶液 and δ 2 H 水 The difference.

4. The data correction method according to claim 3, wherein: The concentration of the methanol aqueous solution is 80~800μL·L -1 .

5. The data correction method according to claim 3, wherein: The concentration gradient of the series of methanol aqueous solutions is 800 μL·L -1 , 727μL·L -1 , 667μL·L -1 , 533μL·L -1 , 400μL·L -1 , 320μL·L -1 , 267μL·L -1 , 200μL·L -1 , 133μL·L -1 , 100μL·L -1 and 80 μL·L -1 .

6. The data correction method according to claim 3, wherein: The plant water includes methanol, ethanol and water; the concentration of the methanol is in the range of 80 μL·L -1 ~800μL·L -1 between.

7. The data correction method according to claim 3, wherein: The isotope spectrum measurement conditions include a room temperature of 25°C and a vaporization chamber temperature of 110°C.

8. The data correction method according to claim 3, wherein: The isotope spectrometry was performed on a Picarro L2140-i instrument.

9. The data correction method according to claim 3, wherein: The plant water is liquid water extracted from plant stems or leaves.

10. The data correction method according to claim 9, characterized in that: The extraction is carried out in a vacuum condensation extraction system, and the parameters set for the vacuum condensation extraction system are: cold trap temperature: -95°C, heating temperature: 120°C, vacuum degree less than 1500Pa, and heating time: 120 minutes.

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