Method for detecting organic carbon component in soil based on gas chromatography-mass spectrometry

Abstract

The invention discloses a method for detecting organic carbon components in soil based on gas chromatography-mass spectrometry, and particularly relates to the technical field of soil detection. The method comprises the following steps: pretreating fresh soil to obtain a fresh soil sample and an air-dried soil sample, respectively extracting organic carbon components to obtain a DOC extracting solution and an LOC extracting solution, and sequentially and respectively carrying out purification treatment, concentration treatment and derivatization on the DOC extracting solution and the LOC extracting solution to obtain a DOC to-be-detected solution and an LOC to-be-detected solution; respectively detecting the DOC to-be-detected liquid and the LOC to-be-detected liquid in a GC-MS instrument to obtain a total ion flow chromatogram, and carrying out qualitative and quantitative analysis to obtain organic carbon component data. Through step-by-step extraction, selective derivatization and GC-MS accurate analysis, molecular level separation, identification and quantification of water-soluble organic carbon DOC and oxidizable organic carbon LOC in soil are achieved, the method is particularly suitable for evaluating contribution of carbohydrate, amino acid and organic acid to the carbon turnover rate, and the method is good in selectivity and high in sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of soil detection, and in particular to a method for detecting soil organic carbon components based on gas chromatography-mass spectrometry. Background Art

[0002] Soil organic carbon is the core carrier of the carbon cycle in terrestrial ecosystems. The biological activity and turnover rate of its different components directly affect the carbon sequestration potential and greenhouse gas emissions. However, traditional soil organic carbon detection methods can only measure the total organic carbon content and cannot distinguish the molecular composition of the active carbon pool, making it difficult to reveal the microscopic mechanism of the carbon cycle. In recent years, researchers have tried to combine Although chemical extraction methods such as oxidation to measure LOC and water extraction to measure DOC can separate active carbon pools, they rely on colorimetry or TOC meters to measure the total amount and cannot analyze the contribution of specific compounds to carbon turnover. Py-GC-MS has poor quantitative accuracy and cannot distinguish carbon pool activity due to the decomposition of small molecular organic matter caused by high-temperature cracking. Nuclear magnetic resonance has difficulty detecting low-abundance active components due to its low sensitivity and cannot be associated with specific carbon pools.

[0003] Current GC-MS technology has significant flaws in soil analysis. It does not distinguish between the heterogeneity of active carbon pools of DOC and LOC, resulting in ambiguous analysis of carbon turnover pathways. Traditional derivatization methods have low efficiency in derivatizing polar components, resulting in severe tailing of chromatographic peaks. At the same time, residual oxidants in the LOC extract destroy the derivatization reaction, resulting in loss of target substances and prominent matrix interference. In view of this, the existing technology lacks an integrated method that can achieve fractionated extraction of carbon pools, selective derivatization, and precise quantification by GC-MS. It is difficult to meet the demand for high-sensitivity detection of soil active carbon components. There is an urgent need to develop an analytical method that provides molecular-level data support for carbon cycle rate research. To this end, a method for detecting soil organic carbon components based on gas chromatography-mass spectrometry is presented. Summary of the Invention

[0004] The present invention aims to provide a method for detecting soil organic carbon components based on gas chromatography-mass spectrometry to solve the problems raised in the above background technology.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for detecting soil organic carbon components based on gas chromatography-mass spectrometry comprises the following steps:

[0007] S1. Take fresh soil and pretreat the fresh soil to obtain fresh soil samples and air-dried soil samples;

[0008] S2. Extract organic carbon components from fresh soil samples and air-dried soil samples to obtain DOC extracts and LOC extracts;

[0009] S3. The DOC extract and the LOC extract are purified and concentrated in sequence to obtain a DOC derivative and a LOC derivative;

[0010] S4. Derivatizing the DOC derivative solution and the LOC derivative solution to obtain a DOC test solution and a LOC test solution;

[0011] S5. The DOC test solution and the LOC test solution are respectively injected into the GC-MS instrument for detection to obtain a total ion current chromatogram. Based on this, the total ion current chromatogram is qualitatively and quantitatively analyzed to obtain organic carbon component data.

[0012] Preferably, the method for obtaining fresh soil samples and air-dried soil samples is:

[0013] Fresh soil was sieved using a standard soil sieve with a pore size of 2 mm. The fresh soil was poured into the sieve and passed through a vibrating sieve machine at an amplitude of 10 mm and a frequency of 200 times / min, so that the soil particles of the fresh soil passed through the sieve holes and impurities were removed to obtain sieved fresh soil. The sieved fresh soil was accurately weighed using an electronic balance and evenly divided into two portions. One portion was placed in a 50 mL sterile centrifuge tube, sealed, and stored in a refrigerator at 4°C for no more than 7 days as a fresh soil sample.

[0014] The other part was used as the air-dried soil sample, which was evenly spread on a 316L stainless steel tray with a thickness of 2 cm. The tray was placed in a vacuum drying oven with a vacuum degree less than or equal to 10 Pa. The vacuum drying temperature was set to 40°C and the vacuum drying time was set to 24 hours for air drying. The air-dried soil sample was transferred to a planetary grinder, ground at 300 rpm for 5 minutes, passed through a 100-mesh standard sieve, and the sieve underflow was collected to obtain the air-dried soil sample.

[0015] Preferably, the method for obtaining the DOC extract is:

[0016] Prepare a fresh soil sample mixture in a ratio of 1:5 between fresh soil sample and ultrapure water. Use an electronic balance to weigh 10.00 g of fresh soil sample and place it in a centrifuge tube. Add 50.0 mL of ultrapure water and place the centrifuge tube symmetrically in a horizontal oscillator with an amplitude of 20 mm and a temperature of 25°C. Oscillate at 180 rpm for 1 hour to fully mix the fresh soil sample and ultrapure water. Place the centrifuge tube in a refrigerated centrifuge after the oscillation and centrifuge at 4°C and 4000 rpm for 15 minutes to obtain the fresh soil sample supernatant.

[0017] The supernatant of fresh soil sample was sucked by pipette and passed through 0.45 The DOC filtrate was collected in a 10 mL brown glass bottle to obtain the DOC extract.

[0018] Preferably, the method for obtaining the LOC extract is:

[0019] In a dark environment, the air-dried soil sample was mixed with 333mM The solution was prepared into an air-dried soil sample mixture at a ratio of 1:25. 5.000 g of air-dried soil sample was weighed using an analytical balance and placed in a brown centrifuge tube. 125.0 mL of Solution, symmetrically fix the centrifuge tube on a horizontal shaker with an amplitude of 30 mm and a temperature of 25°C, shake at a speed of 200 rpm for one hour, keep it away from light during the shaking process, transfer the shaken centrifuge tube into a refrigerated centrifuge, centrifuge at a temperature of 4°C and a speed of 4000 rpm for 15 minutes to obtain the air-dried soil sample supernatant;

[0020] The supernatant of the air-dried soil sample was sucked by a pipette and slowly passed through a 0.45 The LOC filtrate was collected in a 10 mL brown glass bottle to obtain the LOC extract.

[0021] Preferably, the method for obtaining the DOC derivative solution is:

[0022] Will The cation exchange resin was loaded into the chromatography column to obtain a cation exchange resin column, and the cation exchange resin column was rinsed with distilled water until the effluent was neutral. The cation exchange resin column is flushed with distilled water at a flow rate of 10000 until the effluent is neutral to remove metal ions and obtain a purified DOC extract;

[0023] The purified DOC extract was placed in a freeze drying bottle and freeze-dried in a freeze dryer under the following freeze drying conditions: pre-freezing temperature of -50°C, pre-freezing time of 2 hours, vacuum degree of less than 10 Pa, and drying time of 12 hours to obtain DOC freeze-dried powder. The DOC freeze-dried powder was dissolved in 50 Anhydrous pyridine to obtain DOC derivative solution.

[0024] Preferably, the method for obtaining LOC derivative solution is:

[0025] Add 0.1 mol / L of The solution was stirred with a magnetic stirrer until the color of the LOC extract changed from purple to colorless to obtain the reduced LOC extract. The reduced LOC extract was then The LOC extract was purified by passing it through a C18 SPE column pre-activated with 5 mL of methanol and 5 mL of ultrapure water at a flow rate of 100 nm.

[0026] The purified LOC extract was placed in a rotary evaporation bottle and subjected to rotary evaporation at 35°C and 80 rpm. When the volume of the purified LOC extract in the rotary evaporation bottle was concentrated to about 1 mL, it was transferred to a centrifuge tube and assisted in drying using a nitrogen blower at 30°C and a nitrogen pressure of 0.1 MPa until it was completely evaporated to obtain LOC dried powder. The LOC dried powder was dissolved in 50 Anhydrous pyridine was vortexed at 2000 rpm for 1 minute to obtain a LOC derivatized solution.

[0027] Preferably, the method for obtaining the DOC test solution is:

[0028] Weigh 200 mg of methoxyamine hydrochloride and dissolve it in 10 mL of anhydrous pyridine to prepare 20 Methoxyamine hydrochloride pyridine solution, 50 The methoxyamine hydrochloride pyridine solution was added to the reaction tube containing the DOC derivative solution, and the reaction tube was placed in a constant temperature shaker at 37°C and oscillated at 150 rpm for 90 minutes to obtain a DOC derivative solution that had undergone methoxyamination reaction;

[0029] Prepare BSTFA pyridine solution with a ratio of 9:1 of BSTFA containing 1% TMCS and anhydrous pyridine. The BSTFA pyridine solution was added to a reaction tube containing the DOC derivative solution subjected to the methoxyamination reaction, and the reaction tube was placed in a constant temperature drying oven at 70°C for 30 minutes for silanization reaction to convert sugars into TMS-oxime ether derivatives, amino acids into N,O-bisTMS derivatives, and organic acids into TMS esters to obtain a DOC test solution, wherein TMCS is trimethylchlorosilane and BSTFA is N,O-bistrifluoroacetamide.

[0030] Preferably, the method for obtaining the LOC test solution is:

[0031] Weigh 200 mg of methoxyamine hydrochloride and dissolve it in 10 mL of anhydrous pyridine to prepare 20 Methoxyamine hydrochloride pyridine solution, 50 The methoxyamine hydrochloride pyridine solution was added to the reaction tube containing the LOC derivative solution, and the reaction tube was placed in a constant temperature shaker at 37°C and oscillated at 150 rpm for 90 minutes to obtain a LOC derivative solution that had undergone methoxyamination reaction;

[0032] Prepare BSTFA pyridine solution with a ratio of 9:1 of BSTFA containing 1% TMCS and anhydrous pyridine. The BSTFA pyridine solution was added to a reaction tube containing the DOC derivative solution subjected to the methoxyamination reaction, and the reaction tube was placed in a constant temperature drying oven at 70°C for 30 minutes for silanization reaction to convert sugars into TMS-oxime ether derivatives, amino acids into N,O-bis-TMS derivatives, and organic acids into TMS esters to obtain the LOC test solution.

[0033] Preferably, the method for obtaining the total ion current chromatogram is:

[0034] The GC parameters, MS parameters and temperature program of the GC-MS instrument with a DB-5MS chromatographic column were set, and the DOC test solution and the LOC test solution were respectively injected into the set GC-MS instrument for detection to obtain a total ion current chromatogram including a DOC total ion current chromatogram and a LOC total ion current chromatogram;

[0035] The GC parameters include an injection port temperature of 280°C, an injection volume of , the injection mode was splitless mode and the carrier gas was high-purity helium at a flow rate of 1.0 mL / min;

[0036] The MS parameters include an EI source with an electron energy of 70 eV, an interface temperature of 280°C, an ion source temperature of 230°C, and a quadrupole temperature of 150°C;

[0037] The heating program is as follows: the initial temperature is 50°C, after holding for 1 minute, the temperature is increased to 150°C at a rate of 10°C / min, then to 250°C at a rate of 4°C / min, and finally to 320°C at a rate of 15°C / min and held for 5 minutes.

[0038] Preferably, the method for performing qualitative and quantitative analysis on the total ion current chromatogram to obtain organic carbon component data is:

[0039] The organic carbon component data includes carbohydrate component, amino acid component and organic acid component data, wherein the carbohydrate component data includes the concentrations of glucose, galactose, arabinose, xylose, fucose and mannose, the amino acid component data includes the concentrations of phenylalanine, glycine, serine and alanine, and the organic acid component data includes the concentrations of oxalic acid, acetic acid and succinic acid;

[0040] The peak positions of glucose, galactose, fucose, glycine, serine, alanine, oxalic acid and acetic acid were located by the retention time recorded in the DOC total ion current chromatogram, and the ion peak areas at the peak positions were obtained using the instrument workstation. , substitute the ion peak area into the corresponding standard curve equation to calculate the corresponding concentration , the concentrations of glucose, galactose, fucose, glycine, serine, alanine, oxalic acid and acetic acid were obtained, where the retention time of glucose was approximately 26.0±0.6min, the retention time of galactose was approximately 25.5±0.6min, the retention time of fucose was approximately 18.5±0.4min, the retention time of glycine was approximately 12.5±0.4min, the retention time of serine was approximately 16.0±0.5min, the retention time of alanine was approximately 14.0±0.3min, the retention time of oxalic acid was approximately 10.2±0.3min, and the retention time of acetic acid was approximately 11.0±0.3min. The standard curve equation for glucose is: The standard curve equation for galactose is: The standard curve equation for fucose is: The standard curve equation for glycine is: The standard curve equation for serine is: The standard curve equation for alanine is: The standard curve equation for oxalic acid is: The standard curve equation for acetic acid is ;

[0041] The peak positions of arabinose, xylose, mannose, phenylalanine and succinic acid were located by the retention time recorded in the LOC total ion current chromatogram, and the ion peak areas at the peak positions were obtained using the instrument workstation. , substitute the ion peak area into the corresponding standard curve equation to calculate the corresponding concentration , the concentrations of arabinose, mannose, xylose, phenylalanine and succinic acid were obtained, among which the retention time of arabinose was about 18.0±0.4min, the retention time of xylose was about 20.0±0.4min, the retention time of mannose was about 24.5±0.6min, the retention time of phenylalanine was about 22.5±0.5min and the retention time of succinic acid was about 15.0±0.3min. The standard curve equation of arabinose is: The standard curve equation for mannose is: The standard curve equation for xylose is: The standard curve equation for phenylalanine is: The standard curve equation for succinic acid is .

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention obtains DOC extract and LOC extract by step-by-step extraction of fresh soil samples and air-dried soil samples, respectively. After purification, concentration and derivatization, GC-MS detection is used to achieve molecular-level separation, identification and quantification of water-soluble organic carbon and easily oxidized organic carbon in the soil. It solves the problems of traditional methods that are unable to analyze the molecular composition of the activated carbon pool, fuzzy carbon turnover pathways, low derivatization efficiency, oxidant interference and insufficient sensitivity. It can simultaneously quantitatively analyze 13 organic carbon components, providing highly sensitive and selective molecular-level data support for carbon cycle rate research. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. 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.

[0045] Figure 1 The figure is a flow chart of the method steps of the present invention. DETAILED DESCRIPTION

[0046] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without inventive effort are within the scope of protection of the present invention.

[0047] Examples, such as Figure 1 As shown, a method for detecting soil organic carbon components based on gas chromatography-mass spectrometry includes the following steps:

[0048] S1. Take fresh soil and pretreat the fresh soil to obtain fresh soil samples and air-dried soil samples;

[0049] S2. Extract organic carbon components from fresh soil samples and air-dried soil samples to obtain DOC extracts and LOC extracts;

[0050] S3. The DOC extract and the LOC extract are purified and concentrated in sequence to obtain a DOC derivative and a LOC derivative;

[0051] S4. Derivatizing the DOC derivative solution and the LOC derivative solution to obtain a DOC test solution and a LOC test solution;

[0052] S5. The DOC test solution and the LOC test solution are respectively injected into the GC-MS instrument for detection to obtain a total ion current chromatogram. Based on this, the total ion current chromatogram is qualitatively and quantitatively analyzed to obtain organic carbon component data.

[0053] Furthermore, the working principle of the present invention is described below by way of examples:

[0054] Fresh soil from the 0 to 20 cm tillage layer of a farmland in the North China Plain was selected. The sampling time was after the autumn harvest in October 2024. The soil type was fluvo-aquic soil, with a pH of 7.2 and a total organic carbon content of 12.5 g / kg.

[0055] Take 500 g of fresh soil, pass it through a 2 mm standard soil sieve, remove roots and stones, and evenly divide the soil under the sieve into two parts, one fresh soil sample and the other air-dried soil sample. Weigh 10.00 g of fresh soil sample and put it into a centrifuge tube, store it at 4 ° C, spread the air-dried soil sample on a 316L stainless steel tray with a thickness of 2 cm, place it in a drying oven at 40 ° C and a vacuum degree of less than or equal to 10 Pa, air-dry it for 24 h, grind it through a 100 mesh sieve, and obtain 5.000 g of air-dried soil sample.

[0056] Fresh soil samples were mixed with ultrapure water at a ratio of 1:5, shaken at 25°C and 180 rpm for 1 h, centrifuged at 4°C and 4000 rpm for 15 min, and the supernatant of the fresh soil samples was filtered through 0.45 PTFE filter membrane, DOC extract 48mL; air-dried soil sample and 333mM The solutions were mixed in a ratio of 1:25, kept away from light, shaken at 25°C and 200 rpm for 1 hour, centrifuged at 4°C and 4000 rpm for 15 minutes, and the supernatant of the air-dried soil sample was filtered through 0.45 Filter through nylon membrane to obtain 120 mL of LOC extract.

[0057] The DOC extract was pretreated at a flow rate of 1.5 mL / min until the effluent was neutral. The purified DOC extract was pre-frozen at -50℃ for 2h and freeze-dried at a vacuum of less than 10Pa for 12h to obtain DOC freeze-dried powder, which was dissolved in 50 Anhydrous pyridine was added to obtain DOC derivative solution; 0.1 mol / L The solution was stirred until the purple-red color faded, and passed through an activated C18 SPE column at a flow rate of 1.5 mL / min to obtain a reduced LOC extract. The reduced LOC extract was rotary evaporated at 35°C and 80 rpm to 1 mL, evaporated to dryness with nitrogen, and LOC dried powder was obtained, which was dissolved in 50 Anhydrous pyridine to obtain LOC derivative solution.

[0058] Add 50% DOC to the derivatized solution 20mg / mL methoxyamine hydrochloride pyridine solution was shaken at 37℃ and 150rpm for 90min, and then 100 The BSTFA pyridine solution containing 1% TMCS was reacted in a 70℃ constant temperature drying oven for 30 minutes to obtain the DOC test solution. The same DOC derivatization step was used, except that the amount of BSTFA pyridine solution added was 150 , and obtain the LOC test solution.

[0059] The GC parameters, MS parameters and temperature program of the GC-MS instrument with DB-5MS column were set, with the injection port temperature at 280°C and the injection volume at 1. The injection mode was splitless mode, the carrier gas was high-purity helium at a flow rate of 1.0 mL / min, the ion source was an EI source with an electron energy of 70 eV, the interface temperature was 280 °C, the ion source temperature was 230 °C, and the quadrupole temperature was 150 °C. The heating program was an initial temperature of 50 °C, maintained for 1 minute, then heated to 150 °C at a rate of 10 °C / min, then heated to 250 °C at a rate of 4 °C / min, and finally heated to 320 °C at a rate of 15 °C / min and maintained for 5 minutes. Based on this, the DOC test solution and the LOC test solution were respectively injected into the set GC-MS instrument for detection, and the DOC total ion current chromatogram and the LOC total ion current chromatogram were obtained; the peak position of the component was located by the retention time of the DOC and LOC total ion current chromatograms, and the ion peak area was substituted into the corresponding standard curve equation to calculate the corresponding concentration, which was converted to the concentration in the soil, and the arabinose concentration was approximately 12.6 , mannose concentration is about 15.1 , xylose concentration is about 9.6 , phenylalanine concentration is about 8.1 , succinic acid concentration is about 9.2 , glucose concentration is about 23.3 , galactose concentration is about 18.7 , fucose concentration is about 8.8 , glycine concentration is about 5.3 , serine concentration is about 6.8 , alanine concentration is about 6.5 , oxalic acid concentration is about 10.7 and acetic acid concentration of about 13.5 .

[0060] The above-described embodiments are only used to illustrate the technical solutions of the present application, and not to limit them. Modifications to the technical solutions described in the aforementioned embodiments, or equivalent replacements of some of the technical features therein, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A method for detecting soil organic carbon components based on gas chromatography-mass spectrometry, characterized in that: The following steps are involved: S1. Take fresh soil and pretreat the fresh soil to obtain fresh soil samples and air-dried soil samples; S2. Extract organic carbon components from fresh soil samples and air-dried soil samples to obtain DOC extracts and LOC extracts; S3. The DOC extract and the LOC extract are purified and concentrated in sequence to obtain a DOC derivative and a LOC derivative; S4. Derivatizing the DOC derivative solution and the LOC derivative solution to obtain a DOC test solution and a LOC test solution; S5. The DOC test solution and the LOC test solution are respectively injected into the GC-MS instrument for detection to obtain a total ion current chromatogram. Based on this, the total ion current chromatogram is qualitatively and quantitatively analyzed to obtain organic carbon component data.

2. The method for detecting soil organic carbon components based on gas chromatography-mass spectrometry according to claim 1, characterized in that: The method for obtaining fresh soil samples and air-dried soil samples: The fresh soil was sieved with a standard soil sieve to obtain the sieved fresh soil, and the sieved fresh soil was evenly divided into two parts to obtain a fresh soil sample and a soil sample to be air-dried. The fresh soil sample was placed Store in refrigerator until ready to use; The air-dried soil sample is evenly spread on a tray with a specific thickness, and the tray is placed on a sample rack of a vacuum drying oven for air drying. The air-dried soil sample is ground to 100 meshes by a grinder to obtain an air-dried soil sample.

3. The method for detecting soil organic carbon components based on gas chromatography-mass spectrometry according to claim 2, characterized in that: The method for obtaining the DOC extract: Prepare a fresh soil sample mixture according to the ratio of fresh soil sample to ultrapure water at 1:5, put the fresh soil sample mixture into a centrifuge tube, and shake the centrifuge tube with a horizontal shaker, and centrifuge the shaken centrifuge tube with a centrifuge to obtain a fresh soil sample supernatant; The supernatant of the fresh soil sample was aspirated by a pipette and filtered through a polytetrafluoroethylene filter membrane to obtain the DOC extract.

4. The method for detecting soil organic carbon components based on gas chromatography-mass spectrometry according to claim 3, characterized in that: The method for obtaining the LOC extract: In a dark environment, the air-dried soil samples were The solution is in a ratio of 1:25, and an air-dried soil sample mixture is prepared. The air-dried soil sample mixture is put into a centrifuge tube, and the centrifuge tube is shaken by a horizontal oscillator. The centrifuge tube after the shaken treatment is centrifuged through a centrifuge to obtain an air-dried soil sample supernatant. Based on this, the air-dried soil sample supernatant is absorbed by a pipette, and the air-dried soil sample supernatant is filtered through a nylon filter membrane to obtain a LOC extract.

5. The method for detecting soil organic carbon components based on gas chromatography-mass spectrometry according to claim 4, characterized in that: The method for obtaining the DOC derivative solution: Will The type cation exchange resin is loaded into a chromatography column to obtain a cation exchange resin column, and the cation exchange resin column is rinsed with distilled water until the effluent is neutral. Based on this, the DOC extract is rinsed through the cation exchange resin column with distilled water at a set flow rate until the effluent is neutral, thereby obtaining a purified DOC extract; The purified DOC extract was placed in a freeze drying bottle and freeze dried in a freeze dryer according to the set freeze drying conditions to obtain DOC freeze dried powder. The DOC freeze dried powder was dissolved in 50 Anhydrous pyridine to obtain DOC derivative solution.

6. The method for detecting soil organic carbon components based on gas chromatography-mass spectrometry according to claim 5, characterized in that: The method for obtaining the LOC derivative solution: Add LOC extract The solution was stirred at the same time until the color of the LOC extract changed from purple-red to colorless to obtain a reduced LOC extract, and the reduced LOC extract was passed through a C18 SPE column activated with methanol and distilled water at a set flow rate to obtain a purified LOC extract; The purified LOC extract was placed in a rotary evaporation bottle and subjected to rotary evaporation. A nitrogen blower was used for auxiliary drying until the purified LOC extract was completely evaporated to obtain LOC evaporated powder. The LOC freeze-dried powder was dissolved in 50 Anhydrous pyridine to obtain LOC derivative solution.

7. The method for detecting soil organic carbon components based on gas chromatography-mass spectrometry according to claim 6, characterized in that: The method for obtaining the DOC test solution: Configuration 20 Methoxyamine hydrochloride pyridine solution, 50 The methoxyamine hydrochloride pyridine solution is added to the reaction tube containing the DOC derivative solution, and the reaction tube is shaken by a constant temperature oscillator to obtain the DOC derivative solution after methoxyamination reaction; Prepare BSTFA pyridine solution with a ratio of 9:1 of BSTFA containing 1% TMCS and anhydrous pyridine. The BSTFA pyridine solution was added to the reaction tube containing the DOC derivative solution subjected to the methoxyamination reaction, and the reaction tube was placed in a constant temperature drying oven for silanization reaction to obtain the DOC test solution.

8. The method for detecting soil organic carbon components based on gas chromatography-mass spectrometry according to claim 7, characterized in that: The method for obtaining the LOC test solution: Configuration 20 Methoxyamine hydrochloride pyridine solution, 50 The methoxyamine hydrochloride pyridine solution is added to the reaction tube containing the LOC derivative solution, and the reaction tube is shaken by a constant temperature oscillator to obtain the LOC derivative solution after methoxyamination reaction; Prepare BSTFA pyridine solution with a ratio of 9:1 of BSTFA containing 1% TMCS and anhydrous pyridine. The BSTFA pyridine solution was added to the reaction tube containing the DOC derivative solution subjected to the methoxyamination reaction, and the reaction tube was placed in a constant temperature drying oven for silanization reaction to obtain the LOC test solution.

9. The method for detecting soil organic carbon components based on gas chromatography-mass spectrometry according to claim 8, characterized in that: The method for obtaining the total ion current chromatogram: The GC parameters, MS parameters and temperature program of the GC-MS instrument with a DB-5MS chromatographic column were set, and the DOC test solution and the LOC test solution were respectively injected into the set GC-MS instrument for detection to obtain a total ion current chromatogram including a DOC total ion current chromatogram and a LOC total ion current chromatogram; The GC parameters include injection port temperature, injection volume, injection mode and carrier gas; The MS parameters include ion source temperature, interface temperature, ion source temperature and quadrupole temperature.

10. The method for detecting soil organic carbon components based on gas chromatography-mass spectrometry according to claim 9, characterized in that: The method for performing qualitative and quantitative analysis on the total ion current chromatogram to obtain organic carbon component data: The organic carbon component data includes carbohydrate component, amino acid component and organic acid component data, wherein the carbohydrate component data includes the concentrations of glucose, galactose, arabinose, xylose, fucose and mannose, the amino acid component data includes the concentrations of phenylalanine, glycine, serine and alanine, and the organic acid component data includes the concentrations of oxalic acid, acetic acid and succinic acid; The peak positions of glucose, galactose, fucose, glycine, serine, alanine, oxalic acid, and acetic acid were located by the retention time recorded in the DOC total ion current chromatogram, and the ion peak areas at the peak positions were obtained. The ion peak areas were substituted into the corresponding standard curve equation to calculate the concentrations of glucose, galactose, fucose, glycine, serine, alanine, oxalic acid, and acetic acid; The peak positions of arabinose, xylose, mannose, phenylalanine and succinic acid were located by the retention time recorded in the LOC total ion current chromatogram, and the ion peak areas at the peak positions were obtained. The ion peak areas were substituted into the corresponding standard curve equation to calculate the concentrations of arabinose, mannose, xylose, phenylalanine and succinic acid.

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