Pretreatment method for dioxin in fly ash sample

Abstract

The invention discloses a pretreatment method for dioxin in a fly ash sample, and belongs to the technical field of environmental organic pollutant analysis and detection. The pretreatment method comprises the following steps: (1) pretreatment of a fly ash sample: drying, grinding and acidifying the fly ash sample, so that dioxin is easier to extract; (2) extracting a fly ash sample: filtering a product obtained in the step (1), performing Soxhlet extraction on a solid phase, performing liquid-liquid extraction on a liquid phase, merging, and performing rotary evaporation concentration; and (3) purifying the fly ash sample extracting solution, namely purifying the fly ash sample extracting solution obtained in the step (2), namely enabling the extracting solution to sequentially pass through a purification column and a purification column to obtain an analysis sample. According to the method, interference of polychlorinated biphenyl and polybrominated diphenyl ether on dioxin detection can be removed, the process is simple, operation is easy, the cost is greatly reduced, the detection accuracy is high, and the recovery rate is high.

Description

Technical Field

[0001] The present application relates to a method for pre-treating dioxins in fly ash samples, and belongs to the technical field of environmental organic pollutant analysis and detection. Background Art

[0002] Dioxin, also known as dioxin, is a colorless, odorless, teratogenic and carcinogenic fat-soluble substance. Dioxin is actually a general term for dioxins, which refers to aromatic organic compounds composed of two or one oxygen atom connecting two chlorine atoms substituted on a benzene ring. Dioxins have reproductive toxicity, neurotoxicity, endocrine toxicity and immunotoxicity effects. Another characteristic of the toxicity of dioxins is that dioxins are fat-soluble compounds, which are easily accumulated in the fat tissue of organisms, are not easily degraded and excreted, and can accumulate continuously in humans and animals to a high concentration. There is a long latent process before the organisms show obvious symptoms.

[0003] During the incineration process of domestic waste, industrial waste and electronic waste, the fly ash produced contains dioxins. The composition of fly ash is complex, and polychlorinated biphenyls and polybrominated diphenyl ethers coexist with dioxins and have similar structures. When detecting dioxins in fly ash samples, polychlorinated biphenyls and polybrominated diphenyl ethers are interference items. In addition, there are more and more methods for detecting dioxins at this stage, but no matter what method is used for detection, the sample needs to be pre-treated and purified. The traditional purification steps are complicated, especially when it comes to the separation of polychlorinated biphenyls and polybrominated diphenyl ethers, the pre-treatment steps are even more complicated. For the purification of the fully automatic purification system, a set of disposable purification columns are used, which are expensive and have high detection costs.

[0004] Chinese Patent CN 105510505 A is a method for determining the content of dioxins in tea and rice samples, wherein the sample pretreatment is: rapid solvent extraction - composite silica gel column purification - activated carbon column purification - nitrogen blowing concentration. The innovation of the invention is that it effectively reduces the extraction and purification time of the sample, reduces the amount of solvent used, and improves the pretreatment efficiency of the detection. However, the relatively simple silica gel column purification method cannot remove organic contamination in the test solution to the maximum extent, especially the incomplete removal of non-polar impurities such as polycyclic aromatic hydrocarbons, which has a great interference with the subsequent detection of dioxins. In addition, the pretreatment method is difficult to separate polychlorinated biphenyls and polybrominated diphenyl ethers, thereby interfering with the detection results of dioxins, so it is not suitable for fly ash sample detection. Summary of the invention

[0005] In order to solve the above problems, a method for pretreatment of dioxins in fly ash samples is provided, which can remove the interference of polychlorinated biphenyls and polybrominated diphenyl ethers on the detection of dioxins. The process is simple, easy to operate, and the cost is greatly reduced. In addition, the detection accuracy and recovery rate are high.

[0006] According to one aspect of the present application, the present application provides a method for pre-treatment of dioxins in a fly ash sample, comprising the following steps:

[0007] (1) Fly ash sample pretreatment: Dry, grind and acidify the fly ash sample to make dioxins easier to extract;

[0008] (2) Extraction of fly ash samples: The product obtained in step (1) is filtered, the solid phase is subjected to Soxhlet extraction, the liquid phase is subjected to liquid-liquid extraction, the samples are combined, and concentrated by rotary evaporation;

[0009] (3) Purification of fly ash sample extract: The fly ash sample extract obtained in step (2) is purified, including passing the extract through a purification column and a purification column in sequence to obtain an analytical sample.

[0010] Specifically, the acidification is performed by soaking the fly ash sample in a 2-3 mol / L hydrochloric acid solution for 4-5 hours, and the mass ratio of the fly ash sample to the hydrochloric acid solution is 1:10-20.

[0011] Specifically, the present application pre-treats the fly ash sample by performing drying, grinding, acidification and other steps to remove interference from a large amount of metal salts and carbonaceous substances covering the surface of the fly ash sample, so as to ensure that the organic matter in the fly ash sample can be completely extracted.

[0012] Optionally, the purification column includes a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer arranged in sequence from top to bottom; the purification column includes a glass fiber layer, a sulfuric acid silica gel layer, and an anhydrous sodium sulfate layer arranged in sequence from top to bottom; the purification column and the purification column are arranged in series.

[0013] Specifically, it includes a purification column and a purification column, and specific restrictions are made on the composition and arrangement order of the purification column and the purification column. The purification column is set to separate and adsorb impurities in dioxins, and the purification column is set to adsorb and separate polychlorinated biphenyls and polybrominated diphenyl ethers in fly ash, eliminating their interference with dioxin detection results and improving the accuracy of detection results.

[0014] Optionally, the height ratio of the purification column to the purification column is (5-3): (2-3).

[0015] The present application defines the height ratio of the purification column and the purification column to ensure the purification and purification effects, thereby improving the accuracy of the detection results.

[0016] Optionally, in the purification column, the mass ratio of the neutral silica gel layer, the activated carbon layer, the alkaline alumina layer, the Florisil layer, and the modified graphitized carbon black layer is (2-3):1:(3-5):(2-4):(2~3).

[0017] Specifically, the present application makes specific restrictions on the composition of each filler in the purification column and the mass ratio of the neutral silica gel layer, activated carbon layer, alkaline alumina layer, floral silica layer, and modified graphitized carbon black layer in the purification column, so as to separate and adsorb impurities in dioxins to the greatest extent, such as phenolic substances, highly polar compounds, polycyclic aromatic hydrocarbons and other impurities, ensure the purity of the sample, reduce the detection limit, and ensure the accuracy of the detection.

[0018] Optionally, in the purification column, the height ratio of the glass fiber layer, the sulfuric acid silica gel layer, and the anhydrous sodium sulfate layer is (2-4):(7-10):1.

[0019] Specifically, the present application makes specific restrictions on the composition and height ratio of the purification column to adsorb and separate polychlorinated biphenyls and polybrominated diphenyl ethers in fly ash, eliminate their interference with dioxin detection results, and improve the accuracy of detection results.

[0020] Optionally, the modified graphitized carbon black in the modified graphitized carbon black layer is prepared by modifying graphitized carbon black with alkylchlorosilane.

[0021] Specifically, the modified graphitized carbon black layer in the present application is modified by using alkylchlorosilane to modify the graphitized carbon black, introducing long-chain alkyl groups on the surface of the graphitized carbon black, increasing the hydrophobicity of the surface of the graphitized carbon black, thereby enhancing the van der Waals force and π-π interaction between the graphitized carbon black and non-polar impurities such as polycyclic aromatic hydrocarbons, thereby improving the adsorption and adsorption efficiency of non-polar impurities such as polycyclic aromatic hydrocarbons.

[0022] Optionally, the method for preparing the modified graphitized carbon black comprises the following steps:

[0023] S1 disperses graphitized carbon black in anhydrous ethanol;

[0024] Add alkyl chlorosilane to S2, stir evenly, and heat;

[0025] After S3 is cooled, it is filtered, washed and dried to obtain modified graphitized carbon black.

[0026] Optionally, the alkylchlorosilane includes octadecyltrichlorosilane or dodecyltrichlorosilane; the mass ratio of the alkylchlorosilane to the graphitized carbon black is (1.5-2.5):1.

[0027] Optionally, the temperature of the heating treatment in S2 is 60-80° C. and the time is 1-2 hours.

[0028] Optionally, the glass fiber layer also includes activated carbon and titanium dioxide, and the mass ratio of the glass fiber, activated carbon and titanium dioxide is (2-4): (1-3): (0.5-1).

[0029] Specifically, the glass fiber layer of the present application also includes activated carbon and titanium dioxide, and the mass ratio of the three is limited to improve the adsorption capacity.

[0030] The beneficial effects of this application include but are not limited to:

[0031] 1. According to the dioxin pretreatment method in the fly ash sample of the present application, the method can remove the interference of polychlorinated biphenyls and polybrominated diphenyl ethers on the detection of dioxins, the process is simple, easy to operate and the cost is greatly reduced, and the detection accuracy and recovery rate are high.

[0032] 2. According to the dioxin pretreatment method in the fly ash sample of the present application, a pretreatment step is set to destroy the complex matrix in the fly ash, dissolve the metal salts, and remove the interference of a large amount of metal salts and carbon-like substances covering the surface of the fly ash sample, thereby improving the extraction efficiency of dioxins in the fly ash; a purification column is used to separate and adsorb impurities in dioxins, and a purification column is used to adsorb and separate polychlorinated biphenyls and polybrominated diphenyl ethers in fly ash to eliminate their interference with the dioxin detection results and improve the accuracy of the detection results.

[0033] 3. According to the dioxin pretreatment method in the fly ash sample of the present application, specific restrictions are made on the composition, setting order, mass ratio and height ratio of the purification column and the purification column to ensure the effect of impurity adsorption and separation, and achieve the technical effects of high detection accuracy and high recovery rate.

[0034] 4. According to the dioxin pretreatment method in the fly ash sample of the present application, by setting a modified graphitized carbon black layer and limiting the preparation method of the modified graphitized carbon black, long-chain alkyl groups are introduced on the surface of the graphitized carbon black to increase the hydrophobicity of the surface of the graphitized carbon black, thereby enhancing the van der Waals force and π-π interaction between the graphitized carbon black and non-polar impurities such as polycyclic aromatic hydrocarbons, thereby improving the adsorption and adsorption efficiency of non-polar impurities such as polycyclic aromatic hydrocarbons. DETAILED DESCRIPTION

[0035] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0036] Unless otherwise specified, the raw materials in the examples and comparative examples of the present application were purchased through commercial channels.

[0037] Unless otherwise specified, the methods used in the examples and comparative examples of the present application are conventional methods in the prior art.

[0038] Example 1

[0039] A method for pre-treatment of dioxins in fly ash samples:

[0040] (1) Fly ash sample pretreatment: The fly ash sample is dried, ground, and acidified to make dioxins easier to extract; the acidification is performed by soaking the fly ash sample in a 2 mol / L hydrochloric acid solution for 4 h, and the mass ratio of the fly ash sample to the hydrochloric acid solution is 1:10;

[0041] (2) Extraction of fly ash samples: filtering the product obtained in step (1), subjecting the solid phase to Soxhlet extraction, subjecting the liquid phase to liquid-liquid extraction, combining the products, and concentrating them by rotary evaporation; wherein the Soxhlet extraction uses rapid solvent extraction with toluene as the solvent, and the liquid-liquid extraction solvent is dichloromethane;

[0042] (3) Purification of fly ash sample extract: purifying the fly ash sample extract obtained in step (2), including passing the extract through a purification column and a purification column in sequence to obtain an analytical sample; wherein the purification column includes a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer arranged in sequence from top to bottom, and the mass ratio of the neutral silica gel layer, the activated carbon layer, the alkaline alumina layer, the Florisil layer, and the modified graphitized carbon black layer is 2:1:3:2:2; the purification column includes a glass fiber layer, a sulfuric acid silica gel layer, and an anhydrous sodium sulfate layer arranged in sequence from top to bottom, and the height ratio of the glass fiber layer, the sulfuric acid silica gel layer, and the anhydrous sodium sulfate layer is 2:7:1; the height ratio of the purification column to the purification column is 5:2;

[0043] Preparation method of modified graphitized carbon black:

[0044] S1 disperses graphitized carbon black in anhydrous ethanol;

[0045] S2 adds octadecyltrichlorosilane, the mass ratio of octadecyltrichlorosilane to graphitized carbon black is 1.5:1, stirs evenly, and heats at a temperature of 60°C for 1 hour;

[0046] After S3 is cooled, it is filtered, washed and dried to obtain modified graphitized carbon black.

[0047] Example 2

[0048] A method for pre-treatment of dioxins in fly ash samples:

[0049] (1) Fly ash sample pretreatment: The fly ash sample is dried, ground, and acidified to make dioxins easier to extract; the acidification is performed by soaking the fly ash sample in a 3 mol / L hydrochloric acid solution for 4 h, and the mass ratio of the fly ash sample to the hydrochloric acid solution is 1:20;

[0050] (2) Extraction of fly ash samples: filtering the product obtained in step (1), subjecting the solid phase to Soxhlet extraction, subjecting the liquid phase to liquid-liquid extraction, combining the products, and concentrating them by rotary evaporation; wherein the Soxhlet extraction uses rapid solvent extraction with toluene as the solvent, and the liquid-liquid extraction solvent is dichloromethane;

[0051] (3) Purification of fly ash sample extract: purifying the fly ash sample extract obtained in step (2), including passing the extract through a purification column and a purification column in sequence to obtain an analytical sample; wherein the purification column includes a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer arranged in sequence from top to bottom, and the mass ratio of the neutral silica gel layer, the activated carbon layer, the alkaline alumina layer, the Florisil layer, and the modified graphitized carbon black layer is 3:1:5:4:3; the purification column includes a glass fiber layer, a sulfuric acid silica gel layer, and an anhydrous sodium sulfate layer arranged in sequence from top to bottom, and the height ratio of the glass fiber layer, the sulfuric acid silica gel layer, and the anhydrous sodium sulfate layer is 4:10:1; and the height ratio of the purification column to the purification column is 1:1;

[0052] Preparation method of modified graphitized carbon black:

[0053] S1 disperses graphitized carbon black in anhydrous ethanol;

[0054] S2 adds octadecyltrichlorosilane, the mass ratio of octadecyltrichlorosilane to graphitized carbon black is 2.5:1, stirs evenly, and heats at a temperature of 80°C for 2 hours;

[0055] After S3 is cooled, it is filtered, washed and dried to obtain modified graphitized carbon black.

[0056] Example 3

[0057] A method for pre-treatment of dioxins in fly ash samples:

[0058] (1) Fly ash sample pretreatment: The fly ash sample is dried, ground, and acidified to make dioxins easier to extract; the acidification is performed by soaking the fly ash sample in a 2.5 mol / L hydrochloric acid solution for 4 h, and the mass ratio of the fly ash sample to the hydrochloric acid solution is 1:15;

[0059] (2) Extraction of fly ash samples: filtering the product obtained in step (1), subjecting the solid phase to Soxhlet extraction, subjecting the liquid phase to liquid-liquid extraction, combining the products, and concentrating them by rotary evaporation; wherein the Soxhlet extraction uses rapid solvent extraction with toluene as the solvent, and the liquid-liquid extraction solvent is dichloromethane;

[0060] (3) Purification of fly ash sample extract: purifying the fly ash sample extract obtained in step (2), including passing the extract through a purification column and a purification column in sequence to obtain an analytical sample; wherein the purification column includes a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer arranged in sequence from top to bottom, and the mass ratio of the neutral silica gel layer, the activated carbon layer, the alkaline alumina layer, the Florisil layer, and the modified graphitized carbon black layer is 2:1:3:4:3; the purification column includes a glass fiber layer, a sulfuric acid silica gel layer, and an anhydrous sodium sulfate layer arranged in sequence from top to bottom, and the height ratio of the glass fiber layer, the sulfuric acid silica gel layer, and the anhydrous sodium sulfate layer is 3:8:1; and the height ratio of the purification column to the purification column is 5:3;

[0061] Preparation method of modified graphitized carbon black:

[0062] S1 disperses graphitized carbon black in anhydrous ethanol;

[0063] S2 adds octadecyltrichlorosilane, the mass ratio of octadecyltrichlorosilane to graphitized carbon black is 2:1, stir evenly, and heat treatment at a temperature of 70°C for 2h;

[0064] After S3 is cooled, it is filtered, washed and dried to obtain modified graphitized carbon black.

[0065] Example 4

[0066] A method for pre-treatment of dioxins in fly ash samples:

[0067] (1) Fly ash sample pretreatment: The fly ash sample is dried, ground, and acidified to make dioxins easier to extract; the acidification is performed by soaking the fly ash sample in a 2.5 mol / L hydrochloric acid solution for 4 h, and the mass ratio of the fly ash sample to the hydrochloric acid solution is 1:15;

[0068] (2) Extraction of fly ash samples: filtering the product obtained in step (1), subjecting the solid phase to Soxhlet extraction, subjecting the liquid phase to liquid-liquid extraction, combining the products, and concentrating them by rotary evaporation; wherein the Soxhlet extraction uses rapid solvent extraction with toluene as the solvent, and the liquid-liquid extraction solvent is dichloromethane;

[0069] (3) Purification of fly ash sample extract: purifying the fly ash sample extract obtained in step (2), including passing the extract through a purification column and a purification column in sequence to obtain an analytical sample; wherein the purification column includes a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer arranged in sequence from top to bottom, and the mass ratio of the neutral silica gel layer, the activated carbon layer, the alkaline alumina layer, the Florisil layer, and the modified graphitized carbon black layer is 2:1:3:4:3; the purification column includes a glass fiber layer, a sulfuric acid silica gel layer, and an anhydrous sodium sulfate layer arranged in sequence from top to bottom, and the height ratio of the glass fiber layer, the sulfuric acid silica gel layer, and the anhydrous sodium sulfate layer is 3:8:1; the height ratio of the purification column to the purification column is 5:3; the glass fiber layer also includes activated carbon and titanium dioxide, and the mass ratio of the glass fiber, the activated carbon, and the titanium dioxide is 2:1:0.5;

[0070] Preparation method of modified graphitized carbon black:

[0071] S1 disperses graphitized carbon black in anhydrous ethanol;

[0072] S2 adds octadecyltrichlorosilane, the mass ratio of octadecyltrichlorosilane to graphitized carbon black is 2:1, stir evenly, and heat treatment at a temperature of 70°C for 2h;

[0073] After S3 is cooled, it is filtered, washed and dried to obtain modified graphitized carbon black.

[0074] Example 5

[0075] A method for pre-treatment of dioxins in fly ash samples:

[0076] (1) Fly ash sample pretreatment: The fly ash sample is dried, ground, and acidified to make dioxins easier to extract; the acidification is performed by soaking the fly ash sample in a 2.5 mol / L hydrochloric acid solution for 4 h, and the mass ratio of the fly ash sample to the hydrochloric acid solution is 1:15;

[0077] (2) Extraction of fly ash sample: filtering the product obtained in step (1), performing Soxhlet extraction on the solid phase, performing liquid-liquid extraction on the liquid phase, combining the products, and performing rotary evaporation concentration; wherein the Soxhlet extraction adopts rapid solvent extraction, using toluene as the solvent, and the liquid-liquid extraction solvent is selected as dichloromethane;

[0078] (3) Purification of fly ash sample extract: purifying the fly ash sample extract obtained in step (2), including passing the extract through a purification column and a purification column in sequence to obtain an analytical sample; wherein the purification column includes a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer arranged in sequence from top to bottom, and the mass ratio of the neutral silica gel layer, the activated carbon layer, the alkaline alumina layer, the Florisil layer, and the modified graphitized carbon black layer is 2:1:3:4:3; the purification column includes a glass fiber layer, a sulfuric acid silica gel layer, and an anhydrous sodium sulfate layer arranged in sequence from top to bottom, and the height ratio of the glass fiber layer, the sulfuric acid silica gel layer, and the anhydrous sodium sulfate layer is 3:8:1; the height ratio of the purification column to the purification column is 5:3; the glass fiber layer also includes activated carbon and titanium dioxide, and the mass ratio of the glass fiber, the activated carbon, and the titanium dioxide is 4:3:1;

[0079] Preparation method of modified graphitized carbon black:

[0080] S1 disperses graphitized carbon black in anhydrous ethanol;

[0081] S2 adds octadecyltrichlorosilane, dodecyltrichlorosilane and graphitized carbon black in a mass ratio of 2:1, stirs evenly, and heats at a temperature of 70°C for 2 hours;

[0082] After S3 is cooled, it is filtered, washed and dried to obtain modified graphitized carbon black.

[0083] Example 6

[0084] The difference between Example 6 and Example 3 is that the purification column does not include a modified graphitized carbon black layer, and the rest is the same.

[0085] Example 7

[0086] The difference between Example 7 and Example 3 is that a graphitized carbon black layer is used in the purification column instead of a modified graphitized carbon black layer.

[0087] Example 8

[0088] The difference between Example 8 and Example 3 is that the graphitized carbon black layer, the Florisil layer, the alkaline alumina layer, the activated carbon layer, and the neutral silica gel layer are arranged in sequence from top to bottom in the purification column, and the rest are the same.

[0089] Example 9

[0090] The difference between Example 9 and Example 3 is that the height ratio of the purification column to the purification column is 1:2, and the rest are the same.

[0091] Example 10

[0092] The difference between Example 10 and Example 3 is that in the purification column, the mass ratio of the neutral silica gel layer, the activated carbon layer, the basic alumina layer, the floral silica layer, and the modified graphitized carbon black layer is 1:1:1:1:1, and the rest are the same.

[0093] Embodiment 11

[0094] The difference between Example 11 and Example 4 is that the glass fiber layer also includes activated carbon and titanium dioxide, and the mass ratio of glass fiber, activated carbon and titanium dioxide is 1:1:1, and the rest are the same.

[0095] Comparative Example 1

[0096] The difference between Comparative Example 1 and Example 3 is that the purification column is not included, and the rest is the same.

[0097] Comparative Example 2

[0098] The difference between Comparative Example 2 and Example 3 is that in step (3), the sample first passes through the purification column and then passes through the cleansing column, and the rest is the same.

[0099] Experimental Example 1

[0100] The internal standard recovery rate of the analysis samples obtained in Examples 1 to 11 and Comparative Examples 1 to 2 was tested, wherein the amount of the internal standard added was 1000 pg (5 μL, 200 ng / mL). The test results are shown in Table 1.

[0101] Table 1 Recovery test results

[0102]

[0103]

[0104] The present application provides a method for pre-treating dioxins in fly ash samples, which can remove the interference of polychlorinated biphenyls and polybrominated diphenyl ethers on the detection of dioxins. The process is simple, easy to operate, and the cost is greatly reduced. In addition, the detection accuracy and recovery rate are high.

[0105] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for pre-treating dioxins in fly ash samples, characterized in that: The following steps are involved: (1) Fly ash sample pretreatment: Dry, grind and acidify the fly ash sample to make dioxins easier to extract; (2) Extraction of fly ash samples: The product obtained in step (1) is filtered, the solid phase is subjected to Soxhlet extraction, the liquid phase is subjected to liquid-liquid extraction, the samples are combined, and concentrated by rotary evaporation; (3) Purification of fly ash sample extract: The fly ash sample extract obtained in step (2) is purified, including passing the extract through a purification column and a purification column in sequence to obtain an analytical sample.

2. The method for pre-treatment of dioxins in fly ash samples according to claim 1, characterized in that: The purification column comprises a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer arranged in sequence from top to bottom; the purification column comprises a glass fiber layer, a sulfuric acid silica gel layer, and an anhydrous sodium sulfate layer arranged in sequence from top to bottom; the purification column and the purification column are arranged in series.

3. The method for pre-treatment of dioxins in fly ash samples according to claim 2, characterized in that: The height ratio of the purification column to the purification column is (5-3): (2-3).

4. The method for pre-treatment of dioxins in fly ash samples according to claim 2, characterized in that: In the purification column, the mass ratio of the neutral silica gel layer, the activated carbon layer, the alkaline alumina layer, the Florisil layer, and the modified graphitized carbon black layer is (2-3):1:(3-5):(2-4):(2~3).

5. The method for pre-treatment of dioxins in fly ash samples according to claim 2, characterized in that: In the purification column, the height ratio of the glass fiber layer, the sulfuric acid silica gel layer, and the anhydrous sodium sulfate layer is (2-4):(7-10):

1.

6. The method for pre-treating dioxins in fly ash samples according to claim 4, characterized in that: The modified graphitized carbon black in the modified graphitized carbon black layer is prepared by modifying graphitized carbon black with alkylchlorosilane.

7. The method for pre-treating dioxins in fly ash samples according to claim 6, characterized in that: The preparation method of the modified graphitized carbon black comprises the following steps: S1 disperses graphitized carbon black in anhydrous ethanol; Add alkyl chlorosilane to S2, stir evenly, and heat; After S3 is cooled, it is filtered, washed and dried to obtain modified graphitized carbon black.

8. The method for pre-treating dioxins in fly ash samples according to claim 7, characterized in that: The alkyl chlorosilane includes octadecyltrichlorosilane or dodecyltrichlorosilane; the mass ratio of the alkyl chlorosilane to the graphitized carbon black is (1.5-2.5):

1.

9. The method for pre-treating dioxins in fly ash samples according to claim 7, characterized in that: The temperature of the heating treatment in S2 is 60-80°C and the time is 1-2h.

10. The method for pre-treating dioxins in fly ash samples according to claim 5, characterized in that: The glass fiber layer also includes activated carbon and titanium dioxide, and the mass ratio of the glass fiber, activated carbon and titanium dioxide is (2-4): (1-3): (0.5-1).

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