Method for purifying and separating dioxin substances

Abstract

The invention relates to the technical field of separation, in particular to a dioxin substance purification and separation method, separation is carried out through a dioxin substance purification and separation column, and the purification and separation column comprises the following glass packed columns connected in series: a first glass column, a second glass column, a third glass column and a connecting piece; the bottom of the first glass column is directly connected with the top of the second glass column, the bottom of the second glass column is connected with the third glass column through a connecting piece, the two ends of the third glass column are the same, and the method has the advantages of rapidness, simplicity, convenience, low cost and less solid waste generation through the designed three series glass packed columns and optimized filling materials.

Description

Technical Field

[0001] The present application relates to the field of separation technology, and in particular to a method for purifying and separating dioxin-like substances. Background Art

[0002] Dioxins refer to a large class of substances that can bind to aromatic hydrocarbon receptors and cause various biochemical changes in the body, including dioxins (PCDD / Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs). Dioxin detection belongs to ultra-trace analysis. Dioxins with extremely low content in samples need to undergo multiple purification operations after extraction to ensure that interfering impurities are fully removed. For purification operations, there are two typical solutions: 1. FMS automatic purification scheme: After the sample is extracted with the internal standard, it is concentrated and re-dissolved in n-hexane, and purified using the FMS automatic purification equipment. The usual finished purification column selection scheme is 1 multilayer silica gel column, 1 alkaline alumina column and 1 activated carbon silica gel column. The three columns are connected in series through a dedicated connecting pipeline. The automatic purification equipment will automatically activate, rinse and elute. After the dioxin eluate is concentrated, the dioxin internal standard is added to the machine, and the dioxin is analyzed on the machine. After the polychlorinated biphenyl eluate is concentrated, it is combined with the dioxin machine solution, and the polychlorinated biphenyl internal standard is added to the machine, and the polychlorinated biphenyl is analyzed on the machine. This method takes a short time for a single sample, but consumes a lot of reagents, has poor parallel processing capabilities, has a high purification cost, and generates more waste liquid and solid waste.

[0003] 2. Non-series hand-packed column purification scheme: After the sample is extracted, it is concentrated and re-dissolved in n-hexane, first purified with a multi-layer silica gel column, the eluent is concentrated by rotary evaporation to near dryness, and then purified by alkaline alumina column. Alkaline alumina needs to be used as soon as possible after activation, otherwise it may absorb moisture and cause the activity to decrease, and the retention capacity of polychlorinated biphenyls is weakened, resulting in abnormal recovery rate. The eluent is concentrated by rotary evaporation to near dryness, and polychlorinated biphenyls and dioxins are separated by activated carbon silica gel column. After the dioxin eluent is concentrated, the dioxin internal standard is added to the machine, and the dioxin is analyzed on the machine. After the polychlorinated biphenyl eluent is concentrated, it is combined with the dioxin machine solution, and the polychlorinated biphenyl internal standard is added to the machine, and the polychlorinated biphenyl is analyzed on the machine. The manual purification method has a lower cost, but various purification operations usually need to be performed independently, and each purification operation needs to be connected with other steps through concentration. Not only is the efficiency relatively low, but the loss in the concentration process and the waste of organic reagents caused by repeated elution during the purification process are also worthy of attention.

[0004] Therefore, there is still an urgent need in the art to develop a fast, simple, low-cost, and less solid waste-generating dioxin purification and separation method suitable for the detection of dioxin-like substances. Summary of the invention

[0005] The present application aims to establish a method for purifying and separating dioxin-like substances, which has the advantages of being fast, simple, low-cost and generating less solid waste through the designed series glass filling columns and optimized filling materials.

[0006] In the first aspect, the present application provides a purification and separation column for dioxin-like substances, which adopts the following technical solution: A purification and separation column for dioxin-like substances comprises the following series-connected glass-filled 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 both ends of the third glass column are the same.

[0007] By adopting the above technical solution, there is no need for connecting pipes to connect the glass columns, which is convenient to use and will not cause any residue on the connecting pipes. At the same time, the two ends of the third glass column are the same, which ensures 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 filling material can be eluted forward and reverse, achieving a better separation effect of dioxins and dioxin-like polychlorinated biphenyls. Furthermore, the use of glass filling columns will not generate a large amount of solid waste and cause environmental pollution.

[0008] Optionally, the first glass column comprises 40% sulfuric acid silica gel.

[0009] Optionally, the second glass column comprises acidic alumina.

[0010] By adopting the above technical solution, acidic alumina is used instead of the conventional alkaline alumina, which has stronger anti-interference ability and is more convenient to use and store.

[0011] Optionally, the third glass column includes activated carbon silica gel or carbon nanotube / activated carbon composite microspheres.

[0012] By adopting the above technical solution, better separation of dioxins and dioxin-like polychlorinated biphenyls can be achieved.

[0013] In the second aspect, the present application provides a method for purifying and separating dioxins, which adopts the following technical solution: S1: Loading a sample to be treated containing dioxins onto a dioxin purification and separation column as described in the first aspect; S2: Connect the separatory funnel directly to the top of the first glass column and elute with n-hexane; S3: Remove the first glass column, connect the separatory funnel directly to the top of the second glass column, use a mixture of n-hexane and dichloromethane for the first elution, and collect the dioxin-type polychlorinated biphenyl components; S4: Remove the second glass column, connect an empty second glass column, and at the same time turn the third glass column upside down, use toluene to perform a second elution, and collect the dioxin components.

[0014] Optionally, the separatory funnel is provided with a piston, and the flow rate of S2-S4 is controlled by the piston.

[0015] Optionally, the flow rate is controlled to about 2.5 mL / min.

[0016] By adopting the above technical solution, the top of the first glass column and the top of the second glass column can be directly connected to the separatory funnel, which can quickly and easily realize purification and separation using three series and two series glass filling columns respectively. At the same time, the separatory funnel is directly used for elution or washing, and the connecting tube and the injection pump are not required, which is convenient to use and will not cause the residue of substances on the connecting tube.

[0017] In summary, the present application includes at least one of the following beneficial technical effects: 1. Use acidic alumina instead of alkaline alumina, which has stronger anti-interference ability and is more convenient to use and store; 2. The designed cascaded glass-filled columns solve the efficiency problems of the non-cascaded hand-filled column purification method and the cost and environmental protection problems of the FMS automatic purification method. The sample can be directly injected without the need for a pump and corresponding connecting tubes, taking into account the detection efficiency, environmental friendliness and cost control; 3. Compared with the automatic purification method, multiple samples can be processed in parallel when testing large quantities of samples, greatly improving the purification efficiency; 4. Use carbon nanotube / activated carbon composite microspheres instead of activated carbon silica gel to provide selective adsorption of dioxin homologues and achieve better separation of dioxins and dioxin-like PCBs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Shown is a schematic diagram of the structure of the various components of the purification and separation column of the present application; Figure 2 Shown is the assembly diagram of the purification separation column of this application.

[0019] Explanation of the accompanying drawings: 1. first glass column; 2. second glass column; 3. third glass column; 4. connecting piece. DETAILED DESCRIPTION

[0020] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical scheme of the present invention is described in detail below in conjunction with the following specific embodiments and the accompanying drawings of the specification, but it should not be understood as limiting the scope of implementation of the present invention.

[0021] Material n-Hexane (pesticide grade, Shanghai Xingke High Purity Solvent Co., Ltd.), toluene (pesticide grade, Shanghai Xingke High Purity Solvent Co., Ltd.), dichloromethane (pesticide grade, Shanghai Xingke High Purity Solvent Co., Ltd.), anhydrous sodium sulfate (superior grade, Sinopharm Group), concentrated sulfuric acid (superior grade, Yonghua Chemical Co., Ltd.), silica gel for chromatography columns (70-230 mesh, Merck Group), acidic alumina (Shanghai MacLean Biochemical Technology Co., Ltd.), activated carbon silica gel (Kanto Chemical Co., Ltd.), glass wool (Shanghai Anpu Laboratory Technology Co., Ltd.), dioxins (Cambridge Isotope Laboratories, Inc.) and polychlorinated biphenyl standards (Wellington Well-labs).

[0022] Example 1

[0023] 1.1 Extraction 10g sample (the oil content must be less than 1g, and the sample with high oil content needs to reduce the sampling amount as appropriate) is added with dioxin or dioxin-like PCBs to extract the internal standard, and then extracted with accelerated solvent. After concentration, it is re-dissolved in 1mL of n-hexane and purified. The sample can be soil, sediment, solid waste, food (all foods, including poultry meat, eggs, milk, etc.), feed and pesticides. In this embodiment, the sample is soil.

[0024] 1.2 Purification In the first glass column 1 (hereinafter referred to as column 1), glass wool, 1g anhydrous sodium sulfate, 1g neutral silica gel, 10g 40% sulfuric acid silica gel, and 1g anhydrous sodium sulfate were filled respectively, and activated with 10 mL of n-hexane; in the second glass column 2 (hereinafter referred to as column 2), glass wool, 1g anhydrous sodium sulfate, 10g acidic alumina, and 1g anhydrous sodium sulfate were filled respectively, and activated with 10 mL of n-hexane; in the third glass column 3 (hereinafter referred to as column 3), glass wool, 0.5g activated carbon silica gel, and glass wool were filled respectively, and activated with 10 mL of n-hexane. The sulfuric acid silica gel is prepared by adding high-grade pure concentrated sulfuric acid at 0.67 times the mass of silica gel after neutral silica gel is subjected to background removal at 550°C for 24 hours; the anhydrous sodium sulfate is activated at 550°C for 24 hours.

[0025] Connect the three purification columns from top to bottom as column 1, column 2, and column 3. See the glass column for details. Figure 1 and Figure 2 The bottom of column 1 is directly connected to column 2, and the tops of columns 1 and 2 can be directly connected to small separatory funnels for holding organic reagents, and the dripping rate can be controlled by the piston of the separatory funnel. Column 2 is connected to column 3 through connector 4, and both ends of column 3 are the same.

[0026] After loading, first use 120mL of n-hexane for elution. After the elution, remove column 1 and discard the eluent. Then use 80mL of n-hexane and dichloromethane mixed solution for elution (1:1, v / v). The eluent contains 8 dioxin-like polychlorinated biphenyls (DL-PCBs) components. After the elution, remove column 2 and connect an empty column 2. At the same time, turn column 3 upside down and use 80mL of toluene for elution. The eluent contains 17 dioxins (PCDD / Fs) and 4 dioxin-like polychlorinated biphenyls (DL-PCBs) components. By adjusting the opening of the separatory funnel valve containing the eluent, the flow rate is controlled to be about 2.5mL / min.

[0027] 1.3 Concentration detection When only dioxins are determined, the toluene eluate from step 1.3 is concentrated and added to the internal standard. The internal standard for dioxins is EPA1613 ISS, which has two types. 13 C-labeled dioxins: 13 C 12 -2,3,7,8-TCDD, 13 C 12 -1,2,3,7,8,9-HxCDD, analyzed by gas chromatography-tandem high-resolution magnetic-mass spectrometry.

[0028] If DL-PCBs need to be determined simultaneously, after the dioxin analysis is completed, the n-hexane dichloromethane eluate obtained in step 1.3 is concentrated and combined with the dioxin component, and the internal standard is added. The polychlorinated biphenyl is PCB IS, which has three types 13 C-labeled PCBs: 13 C 12 -PCB-70, 13 C 12 -PCB-111, 13 C 12 -PCB-138, analyzed using gas chromatography-tandem high-resolution magnetic-mass spectrometry.

[0029] Gas phase conditions: injection mode: splitless injection 1 μL; injection port temperature: 280℃; carrier gas flow rate: 1.0 mL / min; chromatographic interface temperature: 280℃; chromatographic column: DB-5 ms UI, column length 60 m, inner diameter 0.250 mm, film thickness 0.25 μm.

[0030] Dioxin programmed temperature rise: initial temperature 150°C, hold for 3 minutes, then increase the temperature to 235°C at a rate of 25°C / min, hold for 8 minutes, then increase the temperature to 275°C at a rate of 2°C / min, hold for 5 minutes, then increase the temperature to 290°C at a rate of 1°C / min, hold for 1 minute, then increase the temperature to 310°C at a rate of 7°C / min, hold for 2 minutes.

[0031] PCB temperature program: initial temperature 100 °C, hold for 3 minutes, then increase the temperature to 210 °C at a rate of 30 °C / min, hold for 1 minute, then increase the temperature to 270 °C at a rate of 2 °C / min, hold for 0 minutes, then increase the temperature to 310 °C at a rate of 30 °C / min, and hold for 1 minute.

[0032] 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 material: high boiling point PFK; scan mode: SIM (select appropriate mass-to-charge ratio); resolution: >10000 (10% valley at m / z 331).

[0033] Example 2

[0034] The difference from Example 1 is that the activated carbon silica gel in column 3 is replaced by carbon nanotube / activated carbon composite microspheres, and the mixture is heated at 200-270°C under nitrogen protection for 10-12 hours. The rest is the same as Example 1. The preparation method of carbon nanotube / activated carbon composite microspheres is referred to the literature ("Preparation of carbon nanotube / activated carbon composite microspheres and their application in adsorption of VB12", Acta Physico-Chimica Sinica, 2009, 25(08):1697-1702.).

[0035] Example 3

[0036] The reagent consumption and purification time of each scheme for detecting dioxins and dioxin-like PCBs are compared, and the results are shown in Table 1. Compared with the FMS three-column scheme, the reagent usage and waste liquid generation in the purification process of Examples 1 and 2 of the present application are reduced by 76.3%, and compared with the traditional non-series hand-filled column scheme, the main steps including extraction are reduced by 31.9%, and the reagent usage and waste liquid generation in the purification process are reduced by 29.1%.

[0037] Table 1

[0038] Example 4

[0039] The recovery rate and detection limit of each scheme were compared, and the results are shown in Table 2. Under the condition of ensuring the correct pretreatment operation, Example 2 has significant improvements in recovery rate and detection limit, and the performance of the other methods is almost the same. The possible reasons are: on the one hand, carbon nanotube / activated carbon composite microspheres can better adsorb grease, and on the other hand, carbon nanotube / activated carbon composite microspheres can grade and separate dioxins. Non-ortho-substituted PCBs, PCDDs and PCDFs will be adsorbed by carbon nanotubes, while mono-ortho-substituted PCBs will be adsorbed by the activated carbon adsorption layer. This graded separation method helps to more accurately analyze and process different types of DL-PCBs.

[0040] Table 2

[0041] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, all equivalent changes made according to the principles of the present application should be included in the protection scope of the present application.

Claims

1. A purification and separation column for dioxin-like substances, characterized in that: The invention comprises the following series-connected glass filling columns: a first glass column (1), a second glass column (2), a third glass column (3) and a connecting piece (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) via the connecting piece (4), and both ends of the third glass column (3) are identical.

2. A dioxin purification and separation column according to claim 1, characterized in that: The first glass column (1) comprises 40% sulfuric acid silica gel.

3. A dioxin purification and separation column according to claim 1, characterized in that: The second glass column (2) comprises acidic alumina.

4. A dioxin purification and separation column according to claim 1, characterized in that: The third glass column (3) comprises activated carbon silica gel.

5. A dioxin purification and separation column according to claim 1, characterized in that: The third glass column (3) comprises carbon nanotube / activated carbon composite microspheres.

6. A method for purifying and separating dioxins, characterized in that: The following steps are involved: S1: Loading a sample to be treated containing dioxins onto a dioxin purification separation column as described in any one of claims 1 to 5; S2: Connect the separatory funnel directly to the top of the first glass column (1) and elute with n-hexane; S3: Remove the first glass column (1), connect the separatory funnel directly to the top of the second glass column (2), use a mixture of n-hexane and dichloromethane to perform the first elution, and collect the dioxin-type polychlorinated biphenyl components; 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, use toluene to perform a second elution, and collect the dioxin components.

7. A method for purifying and separating dioxins according to claim 6, characterized in that: The separating funnel is provided with a piston, and the flow rate of S2-S4 is controlled by the piston.

8. The method for purifying and separating dioxins according to claim 7, characterized in that: The flow rate was controlled at about 2.5 mL / min.

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