A method for purifying and separating dioxin-like substances

Abstract

This application relates to the field of separation technology, and in particular to a purification and separation method for dioxin-like substances, which is separated by a purification and separation column for dioxin-like substances. The purification and separation column includes the following series-connected glass packing columns: a first glass column, a second glass column, a third glass column and a connector; the bottom of the first glass column is directly connected to the top of the second glass column, the bottom of the second glass column is connected to the third glass column through a connector, and the two ends of the third glass column are the same. The method has the advantages of being fast, simple, low-cost and generating less solid waste through the designed three-series-connected glass packing columns and optimized packing materials.

Description

Technical Field

[0001] This application relates to the field of separation technology, and particularly to a purification and separation method for dioxin-like substances. Background Art

[0002] Dioxin-like substances refer to a general term for a large class of substances that can bind to the aryl hydrocarbon receptor and cause various biochemical changes in the body, including dioxins (PCDD / Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs). The detection of dioxin-like substances belongs to ultra-trace analysis. Dioxin-like substances with extremely low content in the sample need to undergo multiple purification operations after extraction to ensure that interfering impurities are fully removed. For purification operations, there are the following two typical schemes:

[0003] 1. FMS automatic purification scheme: After the sample is extracted with an extraction internal standard, concentrated and re-dissolved with n-hexane, it is purified using an FMS automatic purification device. The usual finished purification column selection scheme is 1 multi-layer silica gel column, 1 basic alumina column, and 1 activated carbon silica gel column. The three columns are connected in series through a special connecting pipeline. The automatic purification device will automatically activate, wash, and elute. The dioxin eluate is concentrated and then the dioxin injection internal standard is added, and dioxins are analyzed by injection. The polychlorinated biphenyl eluate is concentrated and then combined with the dioxin injection solution, and the polychlorinated biphenyl injection internal standard is added, and polychlorinated biphenyls are analyzed by injection. This method takes a relatively short time for a single sample, but consumes a large amount of reagents, has poor parallel processing ability, high purification cost, and generates more waste liquid and solid waste.

[0004] 2. Non-series hand-packed column purification scheme: After the sample is extracted and concentrated and re-dissolved with n-hexane, it is first purified with a multi-layer silica gel column. The eluate is concentrated by rotary evaporation to near dryness, and then purified with a basic alumina column. The basic alumina needs to be used as soon as possible after activation, otherwise it may absorb moisture and cause a decrease in activity, resulting in a weakened retention ability for polychlorinated biphenyls and abnormal recovery rates. The eluate is concentrated by rotary evaporation to near dryness, and an activated carbon silica gel column is used to separate polychlorinated biphenyls and dioxins. The dioxin eluate is concentrated and then the dioxin injection internal standard is added, and dioxins are analyzed by injection. The polychlorinated biphenyl eluate is concentrated and then combined with the dioxin injection solution, and the polychlorinated biphenyl injection internal standard is added, and polychlorinated biphenyls are analyzed by injection. The manual purification method has a lower cost, but various purification operations usually need to be carried out independently. Each purification operation needs to be connected to other steps through concentration. Not only is the efficiency relatively low, but the losses during the concentration process and the waste of organic reagents caused by repeated washing during the purification process also deserve attention.

[0005] Therefore, there is still an urgent need in this field to develop a rapid, simple, low-cost and less solid waste generating purification and separation method for dioxin-like substances to be applicable to the detection of dioxin-like substances. Summary of the Invention

[0006] This application aims to establish a purification and separation method for dioxin-like substances. By means of a designed series-connected glass-packed column and optimized packing materials, it has the advantages of being fast, simple, low-cost, and generating less solid waste.

[0007] In the first aspect, this application provides a purification and separation column for dioxin-like substances, adopting the following technical solutions:

[0008] A purification and separation column for dioxin-like substances includes the following series-connected glass-packed columns: a first glass column, a second glass column, a third glass column, and a connector; the bottom of the first glass column is directly connected to the top of the second glass column, the bottom of the second glass column is connected to the third glass column through the connector, and both ends of the third glass column are the same.

[0009] By adopting the above technical solutions, there is no need for connecting pipes to connect the glass columns, which is convenient to use and will not cause residue of substances on the connecting pipes; at the same time, both ends of the third glass column are the same, ensuring that both ends can be well connected to the bottom of the second glass column, realizing the forward and reverse connection of the third glass column, so that its packing material can be eluted forward and backward, achieving a better separation effect between dioxin and dioxin-like polychlorinated biphenyls; furthermore, using a glass-packed column will not generate a large amount of solid waste and cause environmental pollution.

[0010] Optionally, the first glass column includes 40% sulfuric acid silica gel.

[0011] Optionally, the second glass column includes acidic alumina.

[0012] By adopting the above technical solutions, using acidic alumina instead of the conventionally used basic alumina has a stronger anti-interference ability and is more convenient to use and store.

[0013] Optionally, the third glass column includes activated carbon silica gel or carbon nanotube / activated carbon composite microspheres.

[0014] By adopting the above technical solutions, a better separation between dioxin and dioxin-like polychlorinated biphenyls can be achieved.

[0015] In the second aspect, this application provides a purification and separation method for dioxin-like substances, adopting the following technical solutions:

[0016] S1: Load the sample to be processed containing dioxin-like substances onto the purification and separation column for dioxin-like substances described in the first aspect;

[0017] S2: Directly connect a separating funnel to the top of the first glass column and wash with n-hexane;

[0018] S3: Remove the first glass column, directly connect the separatory funnel to the top of the second glass column, and perform the first elution with a mixed solution of n-hexane and dichloromethane to collect the dioxin-like polychlorinated biphenyl component.

[0019] S4: Remove the second glass column, connect an empty second glass column, and at the same time invert the third glass column up and down, and perform the second elution with toluene to collect the dioxin component.

[0020] Optionally, the separatory funnel is provided with a piston, and the flow rates of S2 - S4 are controlled by the piston.

[0021] Optionally, the flow rate is controlled to be about 2.5 mL / min.

[0022] By adopting the above technical solutions, the top of the first glass column and the top of the second glass column can be directly connected to the separatory funnel, and the purification and separation using three series-connected and two series-connected glass-packed columns can be realized quickly and simply. At the same time, directly using the separatory funnel for rinsing or elution does not require connecting pipes and injection pumps, which is convenient to use and will not cause residue of substances on the connecting pipes.

[0023] In summary, the present application includes at least one of the following beneficial technical effects:

[0024] 1. Using acidic alumina instead of basic alumina has stronger anti-interference ability and is more convenient to use and store.

[0025] 2. The designed series-connected glass-packed column solves the efficiency problem of the non-series manual packing column purification method and the cost problem and environmental protection problem of the FMS automatic purification method. It can directly inject samples without pumps and corresponding connecting pipes, taking into account detection efficiency, environmental friendliness, and cost control.

[0026] 3. Compared with the automatic purification method, when detecting a large number of samples, multiple samples can be processed in parallel, greatly improving the purification efficiency.

[0027] 4. Using carbon nanotube / activated carbon composite microspheres instead of activated carbon silica gel provides selective adsorption for dioxin homologues and realizes better separation of dioxins and dioxin-like polychlorinated biphenyls. Description of the Drawings

[0028] Figure 1 It shows a structural schematic diagram of each component of the purification and separation column of the present application;

[0029] Figure 2 It shows an assembly drawing of the purification and separation column of the present application.

[0030] Description of the reference numerals: 1. First glass column; 2. Second glass column; 3. Third glass column; 4. Connector. Detailed Description of the Invention

[0031] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the following detailed description of the technical solution of the present invention is provided in conjunction with the following specific embodiments and the accompanying drawings of the specification, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0032] Materials

[0033] n-Hexane (pesticide residue grade, Shanghai Xingke High-Purity Solvents Co., Ltd.), toluene (pesticide residue grade, Shanghai Xingke High-Purity Solvents Co., Ltd.), dichloromethane (pesticide residue grade, Shanghai Xingke High-Purity Solvents Co., Ltd.), anhydrous sodium sulfate (analytical reagent grade, Sinopharm Chemical Reagent Co., Ltd.), concentrated sulfuric acid (analytical reagent grade, Yonghua Chemical Co., Ltd.), silica gel for chromatography packing column (70 mesh - 230 mesh, Merck Group), acidic alumina (Shanghai Macklin Biochemical Co., Ltd.), activated carbon silica gel (Kanto Chemical Co., Inc.), glass wool (Shanghai Anpel Laboratory Technologies Inc.), dioxin (Cambridge Isotope Laboratories, Inc.) and polychlorinated biphenyl standards (Wellington Well-labs).

[0034] Example 1

[0035] 1.1 Extraction

[0036] 10 g of the sample (the oil content should be less than 1 g, and the sampling amount of high-oil samples should be reduced as appropriate) is added with a dioxin or dioxin-like polychlorinated biphenyl extraction internal standard, and accelerated solvent extraction is used. After concentration, it is redissolved with 1 mL of n-hexane and awaits purification. The sample can be soil, sediment, solid waste, food (all foods, including poultry and livestock meat, eggs, milk, etc.), feed, and pesticides. In this example, the sample is soil.

[0037] 1.2 Purification

[0038] In the first glass column 1 (hereinafter referred to as column 1), glass wool, 1 g of anhydrous sodium sulfate, 1 g of neutral silica gel, 10 g of 40% sulfuric acid silica gel, and 1 g of anhydrous sodium sulfate are filled respectively, and activated with 10 mL of n-hexane; in the second glass column 2 (hereinafter referred to as column 2), glass wool, 1 g of anhydrous sodium sulfate, 10 g of acidic alumina, and 1 g of anhydrous sodium sulfate are filled respectively, and activated with 10 mL of n-hexane; in the third glass column 3 (hereinafter referred to as column 3), glass wool, 0.5 g of activated carbon silica gel, and glass wool are filled respectively, and activated with 10 mL of n-hexane. The sulfuric acid silica gel is prepared by adding analytical reagent grade concentrated sulfuric acid at 0.67 times the mass of silica gel after removing the background at 550 °C for 24 hours; the anhydrous sodium sulfate is activated at 550 °C for 24 hours.

[0039] Connect three purification columns from top to bottom as column 1, column 2, and column 3. For the specific details of the glass columns, see Figure 1 and Figure 2 , directly connect the bottom of column 1 to column 2. The tops of column 1 and column 2 can both be directly connected to small separatory funnels for containing organic reagents, and the dropping rate can be controlled by the pistons of the separatory funnels. Connect column 2 to column 3 through connector 4. Both ends of column 3 are the same.

[0040] After sample loading, first rinse with 120 mL of n - hexane. After the rinsing is completed, remove column 1 and discard the rinsing solution at the same time. Then rinse with 80 mL of a mixed solution of n - hexane and dichloromethane (1:1, v / v). The rinsing solution contains 8 components of dioxin - like polychlorinated biphenyls (DL - PCBs). After the rinsing is completed, remove column 2 and connect an empty column 2. At the same time, invert column 3 up and down, and rinse with 80 mL of toluene. The rinsing solution contains 17 components of dioxins (PCDD / Fs) and 4 components of dioxin - like polychlorinated biphenyls (DL - PCBs). By adjusting the opening of the valve of the separatory funnel containing the rinsing solution, control the flow rate at about 2.5 mL / min.

[0041] 1.3 Concentration and Detection

[0042] When only determining dioxins, concentrate the toluene eluate in step 1.3 and add the internal standard for instrument analysis. The internal standard for dioxins is EPA1613 ISS, and there are two 13 ¹³C - labeled dioxins: 13 ¹³C 12 - 2,3,7,8 - TCDD, 13 ¹³C 12 - 1,2,3,7,8,9 - HxCDD, and analyze using gas chromatography - tandem high - resolution magnetic mass spectrometry.

[0043] If it is necessary to simultaneously determine DL - PCBs, after the dioxin analysis is completed, concentrate the eluate of n - hexane and dichloromethane obtained in step 1.3 and combine it with the dioxin components, and add the internal standard for instrument analysis. The internal standard for polychlorinated biphenyls is PCB IS, and there are three 13 ¹³C - labeled polychlorinated biphenyls: 13 ¹³C 12 - PCB - 70, 13 ¹³C 12 - PCB - 111, 13 ¹³C 12 - PCB - 138, and analyze using gas chromatography - tandem high - resolution magnetic mass spectrometry.

[0044] Gas phase conditions: Injection mode: splitless injection 1 μL; Injection port temperature: 280 °C; Carrier gas flow rate: 1.0 mL / min; Chromatograph - mass spectrometer interface temperature: 280 °C; Chromatographic column: DB - 5 ms UI, column length 60 m, inner diameter 0.250 mm, film thickness 0.25 μm.

[0045] Dioxin temperature programming: Initial temperature is 150 °C, hold for 3 minutes, then heat at a rate of 25 °C / minute to 235 °C, stay for 8 minutes, then heat at a rate of 2 °C / minute to 275 °C, stay for 5 minutes, then heat at a rate of 1 °C / minute to 290 °C and stay for 1 minute, and then heat at a rate of 7 °C / minute to 310 °C and stay for 2 minutes.

[0046] Polychlorinated biphenyl temperature programming: Initial temperature is 100 °C, hold for 3 minutes, then heat at a rate of 30 °C / minute to 210 °C, stay for 1 minute, then heat at a rate of 2 °C / minute to 270 °C, stay for 0 minutes, then heat at a rate of 30 °C / minute to 310 °C and stay for 1 minute.

[0047] Mass spectrometry conditions: Ionization method: Electron impact ionization EI+; Ionization current: 0.900 mA; Ionization energy: 45 eV; Ion source temperature: 280 °C; Mass calibration substance: High-boiling PFK; Scanning mode: SIM (select appropriate mass-to-charge ratio); Resolution: >10000 (10% valley at m / z 331).

[0048] Example 2

[0049] The difference from Example 1 is that the activated carbon silica gel in column 3 is replaced with carbon nanotube / activated carbon composite microspheres, and heated under nitrogen protection at 200 - 270 °C for 10 - 12 h, and the rest is the same as Example 1. The preparation method of the carbon nanotube / activated carbon composite microspheres refers to the reference ("Preparation of Carbon Nanotube / Activated Carbon Composite Microspheres and Their Adsorption Application to VB12", Acta Physico-Chimica Sinica, 2009, 25(08):1697 - 1702.).

[0050] Example 3

[0051] The comparison of reagent consumption and purification time for detecting dioxin and dioxin-like polychlorinated biphenyls in each scheme is shown in Table 1. Compared with the FMS three-column scheme, in Example 1 and Example 2 of this application, the reagent usage and waste liquid generation amount during the purification process are reduced by 76.3%. Compared with the traditional non-series hand-packed column scheme, the main step duration including extraction is reduced by 31.9%, and the reagent usage and waste liquid generation amount during the purification process are reduced by 29.1%.

[0052] Table 1

[0053]

[0054] Example 4

[0055] The recovery rates and detection limits of each scheme were compared, and the results are shown in Table 2. When the pretreatment operation is ensured to be correct, Example 2 has significant improvements in both the recovery rate and the detection limit, and the performance of the remaining methods shows little difference. The possible reasons are as follows: on the one hand, the carbon nanotube / activated carbon composite microspheres can better adsorb grease; on the other hand, the carbon nanotube / activated carbon composite microspheres can perform fractional separation on dioxins. Non-ortho-substituted PCBs, PCDDs, and PCDFs will be adsorbed by the carbon nanotubes, while mono-ortho-substituted PCBs will be adsorbed by the activated carbon adsorption layer. This fractional separation method helps to more accurately analyze and process different types of DL-PCBs.

[0056] Table 2

[0057]

[0058] The above are all the preferred embodiments of this application, and the protection scope of this application is not limited thereby. Therefore, all equivalent changes made according to the principles of this application should be covered within the protection scope of this application.

Claims

1. A purification and separation column for dioxin-like substances, characterized in that, It includes the following series-connected glass-packed columns: the first glass column (1), the second glass column (2), the third glass column (3), and the connector (4); the bottom of the first glass column (1) is directly connected to the top of the second glass column (2), the bottom of the second glass column (2) is connected to the third glass column (3) through the connector (4), and both ends of the third glass column (3) are the same; The first glass column (1) includes 40% sulfuric acid silica gel, the second glass column (2) includes acidic alumina, and the third glass column (3) includes carbon nanotube / activated carbon composite microspheres; The carbon nanotube / activated carbon composite microspheres are obtained by the following preparation method: S1. Dissolve chitosan in a 2wt% acetic acid solution to form an acetic acid solution of chitosan, and then add multi-walled carbon nanotubes and mix to obtain a uniform aqueous phase; S2. Mix liquid paraffin and span80 to form a continuous oil phase; S3. Add the aqueous phase to the continuous oil phase obtained in step S2 under stirring, stir and mix for 40 min, then heat to 50 °C and dropwise add a 50wt% glutaraldehyde solution, stir at a constant temperature for 1 h, then add an alkaline solution to adjust the pH of the system to 10, wash the obtained network polymer to neutral and dry it to obtain carbon nanotube / chitosan composite microspheres, and then obtain carbon nanotube / activated carbon composite microspheres after carbonization and activation.

2. A purification and separation method for dioxin-like substances, characterized in that: It includes the following steps: S1: Load the sample to be treated containing dioxin-like substances onto a purification and separation column for dioxin-like substances as described in claim 1; S2: Directly connect the separatory funnel to the top of the first glass column (1) and elute with n-hexane; S3: Remove the first glass column (1), directly connect the separatory funnel to the top of the second glass column (2), and perform the first elution with a mixture of n-hexane and dichloromethane to collect the dioxin-like polychlorinated biphenyl component; S4: Remove the second glass column (2), connect an empty second glass column (2), and at the same time turn the third glass column (3) upside down, and perform the second elution with toluene to collect the dioxin component.

3. The purification and separation method of dioxin-like substances according to claim 2, characterized in that, The separatory funnel is provided with a piston, and the flow rates of S2 - S4 are controlled by the piston.

4. The purification and separation method of dioxin-like substances according to claim 3, characterized in that, The flow rate is controlled to be about 2.5 mL / min.

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