Detection method of landfill leachate

Abstract

The invention relates to a landfill leachate detection method which comprises the following steps: drying a sample to obtain a dried sample; testing the dried sample by adopting headspace gas chromatography-mass spectrometry to realize qualitative analysis of the low-boiling-point small-molecular organic matters; testing the dried sample by adopting pyrolysis gas chromatography-mass spectrometry to realize qualitative analysis of the high-molecular compound; extracting the dried sample to obtain an extract, testing the extract by adopting gas chromatography-mass spectrometry, and realizing qualitative analysis of the high-boiling-point small-molecular organic matter by combining a pyrolysis gas chromatography-mass spectrometry test result; calcining the sample to obtain a calcined sample; and testing the calcined sample by adopting an X-ray fluorescence spectrum and X-ray polycrystalline powder diffraction to realize qualitative analysis of inorganic matters. According to the method, comprehensive detection of the substances in the landfill leachate is realized through combined use of various test instruments, and the method is simple to operate, relatively high in detection speed and relatively good in application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of analysis and detection, and in particular to a method for detecting landfill leachate. Background Art

[0002] In modern society, garbage disposal is an unavoidable problem. Leachate is a liquid produced in landfills, which is produced by the decomposition of organic and inorganic matter in garbage. Leachate contains a large amount of organic and inorganic pollutants, such as organic acids, ammonia nitrogen, heavy metals, etc. These pollutants are very harmful to the environment and human health. Therefore, the treatment and monitoring of leachate has become an important topic in the field of environmental protection.

[0003] Existing landfill leachate monitoring technologies mainly include physical and chemical monitoring and biological monitoring. Physical and chemical monitoring mainly uses chemical analysis techniques, such as Fourier transform infrared spectrometer (FTIR), gas chromatography-mass spectrometer (GC-MS), X-ray fluorescence spectrometer (XRF), X-ray powder diffractometer (XRD), thermogravimetric analyzer (TG), etc. to detect the component information in landfill leachate. Biological monitoring mainly determines the degree of pollution of landfill leachate by the growth of microorganisms.

[0004] However, there are some technical problems with existing detection technologies: first, for the complex composition of leachate, a single detection method is not enough to analyze all the components; second, the sample contains some volatile harmful components, and traditional detection methods will cause secondary harm to the testers; finally, how to simplify the method while obtaining the approximate content of each component has become a more critical issue, which can provide better reference data for environmental monitoring.

[0005] Therefore, the existing landfill leachate monitoring technology still has certain limitations in practical applications, and there is an urgent need to provide a method that can comprehensively and quickly realize leachate detection. Summary of the invention

[0006] To solve the above technical problems, the present invention provides a method for detecting landfill leachate. The detection method provided by the present invention realizes comprehensive detection of substances in landfill leachate by combining multiple testing instruments, has simple operation, fast detection speed, and good application prospects.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for detecting landfill leachate, the method comprising the following steps:

[0009] (1) drying the sample to obtain a dried sample; testing the dried sample by headspace gas chromatography-mass spectrometry to achieve qualitative analysis of low-boiling point small molecular organic matter; and testing the dried sample by pyrolysis gas chromatography-mass spectrometry to achieve qualitative analysis of polymer compounds;

[0010] Extracting the dried sample to obtain an extract, and testing the extract by gas chromatography-mass spectrometry; combining the above pyrolysis gas chromatography-mass spectrometry test results to achieve qualitative analysis of high-boiling point small molecular organic matter;

[0011] (2) calcining the sample to obtain a calcined sample; testing the calcined sample by X-ray fluorescence spectroscopy and X-ray polycrystalline powder diffraction to achieve qualitative analysis of inorganic matter;

[0012] The low-boiling-point small-molecule organic matter in step (1) is a small-molecule organic matter with a boiling point below 100° C., and the high-boiling-point small-molecule organic matter is a small-molecule organic matter with a boiling point exceeding 100° C.;

[0013] Steps (1)-(2) are performed in no particular order.

[0014] In the present invention, the landfill leachate is derived from domestic waste or agricultural waste, and is a complex detection system containing small molecular organic matter (such as fatty acids, plasticizers, lubricants, antioxidants, additives, etc.), organic polymer compounds (such as saturated / unsaturated polyesters, polyolefins, etc.), inorganic matter and water, and the detection difficulty is relatively high.

[0015] In the present invention, the qualitative analysis of low-boiling-point small-molecule organic matter can be achieved by using headspace gas chromatography-mass spectrometry testing; the material information of high-boiling-point small-molecule organic matter and high-molecular compound can be obtained respectively by pyrolysis gas chromatography-mass spectrometry testing, but at this time, the information of high-boiling-point small-molecule organic matter fragments is obtained and cannot be accurately qualitatively determined; at this time, by further extracting the dried sample and combining the detection of the extract with gas chromatography-mass spectrometry, the accurate analysis of high-boiling-point small-molecule organic matter can be achieved; by calcining the sample and testing it with X-ray fluorescence spectroscopy and X-ray polycrystalline powder diffraction, the qualitative analysis of inorganic matter can be achieved.

[0016] The detection method provided by the present invention realizes comprehensive detection of substances in landfill leachate by combining multiple testing instruments, and has simple operation, fast detection speed, and good application prospect.

[0017] Preferably, the temperature of the drying treatment in step (1) is 100-120°C (for example, it can be 100°C, 105°C, 110°C, 115°C, 120°C, etc.), and the time is 1-4h (for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, etc.).

[0018] Preferably, in the headspace gas chromatography-mass spectrometry of step (1), the heating equilibrium temperature of the gas chromatography is 100-120°C (for example, it can be 100°C, 105°C, 110°C, 115°C, 120°C, etc.), and the heating equilibrium time is 25-35min (for example, it can be 25min, 27.5min, 30min, 32.5min, 35min, etc.).

[0019] Preferably, in the pyrolysis gas chromatography-mass spectrometry test in step (1), the thermal pyrolysis includes a first stage and a second stage.

[0020] Preferably, the cracking temperature of the first stage is 280-320°C (for example, it can be 280°C, 290°C, 300°C, 310°C, 320°C, etc.), and the time is 0.15-0.25min (for example, it can be 0.15min, 0.18min, 0.2min, 0.22min, 0.25min, etc.).

[0021] Preferably, the cracking temperature of the second stage is 550-650°C (for example, 550°C, 575°C, 600°C, 625°C, 650°C, etc.), and the time is 0.15-0.25min (for example, 0.15min, 0.18min, 0.2min, 0.22min, 0.24min, etc.).

[0022] Preferably, in the pyrolysis gas chromatography-mass spectrometry test in step (1), the split ratio of the gas chromatography is (10-100):1 (for example, it can be 10:1, 20:1, 50:1, 80:1, 100:1, etc.).

[0023] Preferably, in the pyrolysis gas chromatography-mass spectrometry test in step (1), the temperature raising program of the gas chromatography is: the initial temperature is 30-50°C (for example, it can be 30°C, 35°C, 40°C, 45°C, 50°C, etc.), maintained for 2-4min (for example, it can be 2min, 2.5min, 3min, 3.5min, 4min, etc.), and the temperature is raised to 130-150°C at 8-12°C / min (for example, it can be 8°C / min, 9°C / min, 10°C / min, 11°C / min, 12°C / min, etc.). (For example, it may be 130℃, 135℃, 140℃, 145℃, 150℃, etc.), then increase the temperature to 300-320℃ (for example, it may be 300℃, 305℃, 310℃, 315℃, 320℃, etc.) at 18-22℃ / min (for example, it may be 18℃ / min, 19℃ / min, 20℃ / min, 21℃ / min, 22℃ / min, etc.), and maintain for 5-10min (for example, it may be 5min, 6min, 7min, 8min, 9min, 10min, etc.).

[0024] Preferably, the solvent used for the extraction in step (1) comprises a combination of solvent one and solvent two.

[0025] The solvent one includes any one of methanol or ethanol or a combination of the two.

[0026] The second solvent includes any one of chloroform, dichloromethane or tetrahydrofuran, or a combination of at least two of them.

[0027] In the present invention, by rationally compounding the extraction solvent, it has a higher extraction efficiency for small molecular organic matter in the sample, which is helpful for subsequent comprehensive analysis of the substance.

[0028] Preferably, the volume ratio of the solvent one to the solvent two is (4-6):1 (for example, it can be 4:1, 4.5:1, 5:1, 5.5:1, 6:1, etc.).

[0029] In the present invention, when the ratio of the compound solvent is within the above-defined range, the extraction effect is better.

[0030] Preferably, the extraction method in step (1) includes ultrasound or Soxhlet extraction.

[0031] Preferably, the power of the ultrasound is 100-500 W (for example, 100 W, 200 W, 300 W, 400 W, 500 W, etc.), and the time is 2-4 h (for example, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, etc.).

[0032] Preferably, the temperature of the Soxhlet extraction is 100-120°C (for example, it can be 100, 102, 105, 107, 110, 112, 115, 117, 120°C, etc.), and the time is 5-8h (for example, it can be 5, 5.5, 6, 6.5, 7, 7.5, 8h, etc.).

[0033] Preferably, in the gas chromatography-mass spectrometry test in step (1), the split ratio of the gas chromatography is (30-60):1 (for example, it can be 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, 60:1, etc.).

[0034] In the present invention, a higher or lower split ratio will affect the peak shape. Within the range defined by the present invention, the detection effect is better.

[0035] Preferably, in the gas chromatography-mass spectrometry test in step (1), the temperature rising program of the gas chromatography is: the initial temperature is 40-60°C (for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, etc.), maintained for 1-3min (for example, it can be 1min, 1.5min, 2min, 2.5min, 3min, etc.), and the temperature is raised to 140-160°C (for example, it can be 140, 145, 150, 160, etc.) at a rate of 8-12°C / min (for example, it can be 8°C / min, 9°C / min, 10°C / min, 11°C / min, 12°C / min, etc.). 155, 160, etc.), hold for 0.5-2min (for example, 0.5min, 1min, 1.5min, 2min, etc.), then increase the temperature to 300-320℃ (for example, 300℃, 305℃, 310℃, 315℃, 320℃, etc.) at 18-22℃ / min (for example, 18℃ / min, 19℃ / min, 20℃ / min, 21℃ / min, 22℃ / min, etc.), hold for 4-6min (for example, 4min, 4.5min, 5min, 5.5min, 6min, etc.).

[0036] In the present invention, the gas chromatography adopts a two-stage temperature rising program, and the obtained peak shape is better, which is helpful for the qualitative analysis of small molecular organic matter.

[0037] Preferably, the calcination treatment in step (2) is carried out at a temperature of 560-850°C (for example, 560°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, etc.), and the time is 3-6h (for example, 3h, 4h, 5h, 6h, etc.).

[0038] Preferably, the detection method further comprises: testing the sample using the Karl Fischer method to obtain the percentage of water in the sample.

[0039] Preferably, the detection method further comprises: testing the sample by thermogravimetric analysis to obtain the sum of water and low-boiling-point small-molecule organic matter, high-boiling-point small-molecule organic matter, polymer compounds and inorganic salt percentages in the sample.

[0040] Compared with the prior art, the present invention has at least the following beneficial effects:

[0041] The detection method provided by the present invention realizes comprehensive detection of small molecular organic matter, organic polymer compounds and inorganic matter in landfill leachate by combining multiple testing instruments such as headspace gas chromatography-mass spectrometry, pyrolysis gas chromatography-mass spectrometry, gas chromatography-mass spectrometry, X-ray fluorescence spectroscopy and X-ray polycrystalline powder diffraction. The detection method is simple to operate and has a fast detection speed, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is the total ion current spectrum of headspace gas chromatography-mass spectrometry in Example 1.

[0043] Figure 2 It is the total ion current spectrum of the first section of pyrolysis gas chromatography-mass spectrometry in Example 1.

[0044] Figure 3 It is the total ion current spectrum of the second stage pyrolysis gas chromatography-mass spectrometry in Example 1.

[0045] Figure 4 It is the total ion current spectrum of gas chromatography-mass spectrometry in Example 1.

[0046] Figure 5 This is the X-ray polycrystalline powder diffraction pattern in Example 1.

[0047] Figure 6 This is the thermogravimetric analysis diagram in Example 1. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0049] Example 1

[0050] This embodiment provides a method for detecting landfill leachate, the detection method comprising the following steps:

[0051] (1) Weigh 6 g of sample and bake it at 110 °C for 2.5 h to obtain a dried sample;

[0052] (2) using headspace gas chromatography-mass spectrometry to test the dried sample obtained in step (1) to achieve qualitative analysis of low-boiling-point small-molecule organic matter; wherein the heating equilibrium temperature of the headspace gas chromatography is 120° C., and the heating equilibrium time is 30 min;

[0053] (3) using pyrolysis gas chromatography-mass spectrometry to test the dried sample obtained in step (1), wherein the first stage of pyrolysis can obtain material information of high-boiling point small molecular compounds, and the second stage of pyrolysis can achieve qualitative analysis of high molecular compounds;

[0054] The pyrolysis gas chromatography-mass spectrometry test conditions are as follows:

[0055] The pyrolysis temperature of the first stage was 300°C and the time was 0.2 min, and the pyrolysis temperature of the second stage was 600°C and the time was 0.2 min; the chromatographic column of the gas chromatography was Rtx-5MS (60m*0.25mm*0.25μm), the injection port temperature was 300°C, the carrier gas was helium, the flow rate was 1.5mL / min, the split ratio was 50:1, and the heating program was: the initial temperature was 40°C for 3 min, the temperature was increased to 140°C at 10°C / min, and then the temperature was increased to 310°C at 20°C / min, and maintained for 8 min; the ion source temperature of the mass spectrometer was 230°C, the interface temperature was 310°C, the ionization mode was electron bombardment (70ev), and the scanning range was 20-1000m / z;

[0056] (4) extracting the dried sample obtained in step (1) by ultrasonic extraction at 250W for 3h with a methanol and tetrahydrofuran composite solvent in a volume ratio of 5:1 to obtain an extract, removing excess solvent by nitrogen purging, and testing by gas chromatography-mass spectrometry; combining the pyrolysis gas chromatography-mass spectrometry test results of step (3) to achieve qualitative analysis of high-boiling point small molecular organic matter;

[0057] The gas chromatography-mass spectrometry test conditions are as follows:

[0058] The gas chromatographic column was Rtx-5MS (60m*0.25mm*0.25μm), the injection port temperature was 280°C, the carrier gas was helium, the flow rate was 1.5mL / min, the split ratio was 45:1, and the heating program was as follows: initial temperature 50°C was maintained for 2min, the temperature was increased to 150°C at 10°C / min, maintained for 1min, and then the temperature was increased to 310°C at 20°C / min, maintained for 5min;

[0059] (5) taking a sample and calcining it at 750° C. for 4.5 hours to obtain a calcined sample; testing the calcined sample by X-ray fluorescence spectroscopy and X-ray polycrystalline powder diffraction to achieve qualitative analysis of inorganic matter;

[0060] The X-ray fluorescence spectrometry test conditions are as follows: rhodium is used as the target material, 10 mm is used as the scanning diameter, the test environment is vacuum, the scanning range is from oxygen to uranium, and the mode is single element;

[0061] The X-ray polycrystalline powder diffraction test conditions are as follows: copper as target, scanning range 5-90°C, scanning speed 10° / min, continuous scanning step size 0.02°, tube voltage 40KV, tube current 50mA, divergence slit DS 1 / 2°, anti-scattering slit SS 10mm;

[0062] (6) taking samples and testing the moisture content using the Karl Fischer volumetric method to obtain the percentage of water in the samples;

[0063] (7) taking a sample for thermogravimetric testing, and combining the result of step (6) to obtain the percentage of water, low-boiling point small molecule organic matter, high-boiling point small molecule organic matter, polymer compound and inorganic salt in the sample.

[0064] The following is a detailed description of the test results with reference to the accompanying drawings:

[0065] In step (2), the total ion current spectrum obtained by headspace gas chromatography-mass spectrometry is as follows: Figure 1 As shown, it was concluded that the sample contained 2-butanone;

[0066] In step (3), the total ion current spectrum obtained by the first stage of thermal cracking is as follows: Figure 2 As shown, it was concluded that the sample contained terephthalate esters, fatty acids, and amide lubricants;

[0067] In step (3), the total ion current spectrum obtained by the second stage of thermal cracking is as follows: Figure 3 As shown, it was concluded that the sample contained terephthalate, long-chain alkanes, and polyolefins;

[0068] In step (4), the total ion current spectrum obtained by gas chromatography-mass spectrometry is as follows: Figure 4 As shown, it was concluded that the sample contained amide lubricants and fatty acids;

[0069] In step (5), the X-ray fluorescence spectrum test results are shown in Table 1, indicating that the sample contains sodium salt, potassium salt and calcium salt;

[0070] Table 1

[0071]

[0072] In step (5), the X-ray polycrystalline powder diffraction pattern is as follows: Figure 5 As shown, it is concluded that the sample contains sodium chloride and potassium chloride;

[0073] In step (7), the thermogravimetric analysis diagram is as follows Figure 6 As shown, combined with the water content obtained in step (6), the percentages of water, low-boiling point small-molecule organic matter, high-boiling point small-molecule organic matter, macromolecular compound and inorganic salt in the sample are 96.9%, 1.3%, 0.7%, 0.3% and 0.8% respectively.

[0074] Example 2

[0075] This embodiment provides a method for detecting landfill leachate, which differs from Embodiment 1 only in that, in step (4), a 4:1 composite solvent of ethanol and dichloromethane is used for extraction;

[0076] The gas chromatography-mass spectrometry test conditions are as follows:

[0077] The gas chromatography split ratio was 30:1, and the temperature program was as follows: initial temperature 40 °C, maintained for 1 min, heated to 140 °C at 8 °C / min, maintained for 0.5 min, then heated to 300 °C at 18 °C / min, maintained for 4 min;

[0078] For other details, refer to Example 1.

[0079] Example 3

[0080] This embodiment provides a method for detecting landfill leachate, which differs from Embodiment 1 only in that, in step (4), a 6:1 methanol and chloroform composite solvent is used for extraction at 105° C. for 6 h;

[0081] The gas chromatography-mass spectrometry test conditions are as follows:

[0082] The split ratio of the gas chromatograph was 60:1, and the temperature program was as follows: initial temperature 60 °C was maintained for 3 min, then the temperature was increased to 160 °C at 12 °C / min, maintained for 2 min, and then the temperature was increased to 320 °C at 22 °C / min, maintained for 6 min;

[0083] For other details, refer to Example 1.

[0084] Example 4

[0085] This embodiment provides a method for detecting landfill leachate, which differs from Embodiment 1 only in that, in step (4), only methanol is used for extraction. The rest is as in Embodiment 1.

[0086] Example 5

[0087] This embodiment provides a method for detecting landfill leachate, which differs from Embodiment 1 only in that, in step (4), only tetrahydrofuran is used for extraction, and the rest is as in Embodiment 1.

[0088] Example 6

[0089] This embodiment provides a method for detecting landfill leachate, which differs from Embodiment 1 only in that, in step (4), the split ratio of the gas chromatography is 10:1, and the rest is as in Embodiment 1.

[0090] Example 7

[0091] This embodiment provides a method for detecting landfill leachate, which differs from Embodiment 1 only in that, in step (4), the split ratio of the gas chromatography is 100:1, and the rest is referred to Embodiment 1.

[0092] Example 8

[0093] This embodiment provides a method for detecting landfill leachate, which differs from Embodiment 1 only in that, in step (4), the temperature raising program of the gas chromatography is: the initial temperature is 50°C, maintained for 2 min, then the temperature is raised to 310°C at a rate of 15°C / min, and maintained for 5 min. The rest is as in Embodiment 1.

[0094] The landfill leachate samples were tested using the method provided in Examples 1-8. The chromatogram information and extraction rate of the gas chromatography-mass spectrometry test results obtained in step (4) are shown in Table 2, where the extraction rate is the ratio of the weight difference before and after sample extraction to the original sample weight.

[0095] Table 2

[0096] Group Extraction rate Peak number Average half peak width Example 1 0.13 14 0.3 Example 2 0.12 13 0.5 Example 3 0.12 12 0.4 Example 4 0.09 7 0.4 Example 5 0.10 6 0.3 Example 6 0.13 13 1.0 Example 7 0.13 14 1.2 Example 8 0.13 13 1.1

[0097] By comparing Example 1 with Examples 4-5, it can be seen that the present invention has a higher extraction efficiency and a larger number of chromatographic peaks through the reasonable compounding of the extraction solvent, and can better realize the comprehensive analysis of the substance;

[0098] It can be seen from the comparison between Example 1 and Examples 6-8 that the present invention limits the split ratio and the temperature rise program of the gas chromatograph, so that the peak shape of the obtained gas chromatograph is better.

[0099] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for detecting landfill leachate, characterized in that: The detection method comprises the following steps: (1) drying the sample to obtain a dried sample; testing the dried sample by headspace gas chromatography-mass spectrometry to achieve qualitative analysis of low-boiling point small molecular organic matter; and testing the dried sample by pyrolysis gas chromatography-mass spectrometry to achieve qualitative analysis of polymer compounds; Extracting the dried sample to obtain an extract, and testing the extract by gas chromatography-mass spectrometry; combining the above pyrolysis gas chromatography-mass spectrometry test results to achieve qualitative analysis of high-boiling point small molecular organic matter; (2) calcining the sample to obtain a calcined sample; testing the calcined sample by X-ray fluorescence spectroscopy and X-ray polycrystalline powder diffraction to achieve qualitative analysis of inorganic matter; Steps (1)-(2) are performed in no particular order.

2. The detection method according to claim 1, characterized in that: The drying process in step (1) is carried out at a temperature of 100-120° C. for a period of 1-4 hours. Preferably, in the headspace gas chromatography-mass spectrometry of step (1), the heating equilibrium temperature of the gas chromatography is 100-120° C., and the heating equilibrium time is 25-35 min.

3. The detection method according to claim 1 or 2, characterized in that: In the pyrolysis gas chromatography-mass spectrometry test of step (1), the thermal pyrolysis includes a first stage and a second stage; Preferably, the cracking temperature of the first stage is 280-320°C and the time is 0.15-0.25min; Preferably, the second stage pyrolysis temperature is 550-650°C and the time is 0.15-0.25min; Preferably, in the pyrolysis gas chromatography-mass spectrometry test in step (1), the split ratio of the gas chromatography is (10-100):1; Preferably, in the pyrolysis gas chromatography-mass spectrometry test in step (1), the temperature rising program of the gas chromatography is: the initial temperature is 30-50°C, maintained for 2-4 minutes, heated to 130-150°C at 8-12°C / min, and then heated to 300-320°C at 18-22°C / min, and maintained for 5-10 minutes.

4. The detection method according to any one of claims 1 to 3, characterized in that: The solvent used for the extraction in step (1) comprises a combination of solvent one and solvent two; The solvent 1 includes any one of methanol or ethanol or a combination of the two; The second solvent includes any one of chloroform, dichloromethane or tetrahydrofuran or a combination of at least two thereof; Preferably, the volume ratio of solvent one to solvent two is (4-6):

1.

5. The detection method according to any one of claims 1 to 4, characterized in that: The extraction method in step (1) includes ultrasonic extraction or Soxhlet extraction; Preferably, the power of the ultrasound is 100-500W, and the time is 2-4h; Preferably, the temperature of the Soxhlet extraction is 100-120° C. and the time is 5-8 h.

6. The detection method according to any one of claims 1 to 5, characterized in that: In the gas chromatography-mass spectrometry test in step (1), the split ratio of the gas chromatography is (30-60):

1.

7. The detection method according to any one of claims 1 to 6, characterized in that: In the gas chromatography-mass spectrometry test of step (1), the temperature raising program of the gas chromatography is as follows: the initial temperature is 40-60°C, maintained for 1-3 min, heated to 140-160°C at 8-12°C / min, maintained for 0.5-2 min, and then heated to 300-320°C at 18-22°C / min, maintained for 4-6 min.

8. The detection method according to any one of claims 1 to 7, characterized in that: The calcination temperature in step (2) is 560-850°C and the calcination time is 3-6h.

9. The detection method according to any one of claims 1 to 8, characterized in that: The detection method also includes: testing the sample using the Karl Fischer method to obtain the percentage of water in the sample.

10. The detection method according to any one of claims 1 to 9, characterized in that: The detection method also includes: testing the sample by thermogravimetric analysis to obtain the percentage content of the total of water and low-boiling-point small-molecule organic matter, high-boiling-point small-molecule organic matter, high-molecular compound and inorganic salt in the sample.

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