Cobalt-based porous carbon derivative for QuEChERS purification material and application of cobalt-based porous carbon derivative in sample pretreatment and tobacco pesticide residue detection

Abstract

The invention belongs to the technical field of pesticide residue detection, and particularly relates to a cobalt-based porous carbon derivative for a QuEChERS purification material and application of the cobalt-based porous carbon derivative in sample pretreatment and tobacco pesticide residue detection. The preparation method of the cobalt-based porous carbon derivative for the QuEChERS purification material comprises the following steps that ZIF-67 is calcined in an inert atmosphere to obtain a ZIF-67 derived carbon material, acid treatment is conducted on the ZIF-67 derived carbon material, the cobalt-based porous carbon derivative is obtained, and the total time of the acid treatment is 10-30 h. The ZIF-67 derived carbon material is subjected to acid treatment, unstable metal particles loaded on the porous material can be removed, the cobalt-based porous carbon derivative large in specific surface area and high in stability is obtained, a large number of adsorption sites released through acid treatment, stable metal sites and active sites of heteroatoms such as nitrogen achieve a synergistic effect, and the adsorption activity of the cobalt-based porous carbon derivative is improved. Wider matrix interferents can be removed, so that the capability of purifying the matrix interferents of the tobacco sample is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticide residue detection, and in particular to a cobalt-based porous carbon derivative for QuEChERS purification material and its application in sample pretreatment and tobacco pesticide residue detection. Background Art

[0002] Tobacco is susceptible to pests and diseases during planting and storage, and the use of pesticides can prevent and control pests and diseases, thereby improving the yield and quality of tobacco. However, the large-scale use of pesticides and the abuse of highly toxic pesticides have led to pesticide residues in tobacco. Since the pesticides that need to be analyzed and measured are often trace or even ultra-trace components in tobacco, and there are many types, chemical structures and properties, the complex matrix in tobacco samples poses a great challenge to their accurate quantitative detection. Therefore, compared with the rapidly developing analytical instruments, sample pretreatment technology is the key to determining the accuracy and efficiency of pesticide residue detection.

[0003] The QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method is a new rapid sample pretreatment technology developed by Professor Anastassiades of the United States Department of Agriculture and his collaborators in 2003. It has the advantages of being fast, simple, cheap, safe, reliable and having a high recovery rate. Its principle is similar to solid phase extraction, which uses the interaction between the purification material and the impurities in the matrix to adsorb impurities and achieve the purpose of impurity removal and purification. The technology is simple to operate and mainly includes three steps: (1) extracting residual pesticides using acetonitrile; (2) adding salting-out agents such as anhydrous magnesium sulfate for stratification; (3) adding purification materials such as ethylenediamine-N-propylsilane (PSA) for impurity removal. Given that many samples such as tobacco have complex matrices and more interferences, the impurity removal and purification steps are becoming increasingly important for the analysis and detection of residual pesticides in samples. This is because impurity removal and purification can remove impurities in the matrix, thereby helping to reduce the detection limit and ensure the accuracy of the test results.

[0004] In the classic QuEChERS method, N-propylethylenediamine (PSA), octadecylsilane bonded silica gel (C18) and graphitized carbon black (GCB) adsorbents are often used as purification materials. However, the disadvantage that conventional purification materials need to match the matrix limits the further application of QuEChERS technology in tobacco pesticide residue detection. The main reason is that the existing purification materials do not have a strong enough adsorption capacity for matrix interferences: on the one hand, they are restricted by the single active site of the purification material and can only adsorb and remove matrix interferences of specific properties; on the other hand, they are restricted by the limited specific surface area of ​​the purification material, and most two-dimensional materials are prone to agglomeration during actual use, resulting in a sharp drop in their actual specific surface area.

[0005] A Chinese patent application with application publication number CN116510691A, which was applied for and published on August 1, 2023, discloses an application of a ZIF-67-derived carbon material. The ZIF-67-derived carbon material is obtained by heating ZIF-67 to 600-800°C in an inert atmosphere for annealing and carbonization treatment, and is used as a magnetic purifier for QuEChERS pesticide residue analysis. The pesticide residues of crops such as celery are detected and analyzed. The ZIF-67-derived carbon constructed by high-temperature carbonization gives it sufficient magnetic strength to achieve efficient separation. In addition, the ZIF-67-derived carbon itself, as a porous carbon material, has a strong adsorption effect on interferences in the pesticide analysis process, and exhibits a good purification effect.

[0006] However, the above-mentioned ZIF-67 derived carbon material as QuEChERS purification material is still limited in its ability to purify impurities in the matrix when facing tobacco samples with complex matrices and more interferences. Summary of the invention

[0007] The object of the present invention is to provide a cobalt-based porous carbon derivative for QuEChERS purification material, so as to solve the problem that the prior art has poor purification ability for matrix interferents in tobacco samples.

[0008] The second object of the present invention is to provide a cobalt-based porous carbon derivative for QuEChERS purification material for use in sample pretreatment during tobacco pesticide residue detection, thereby solving the problem of poor purification ability of prior art for matrix interferences in tobacco samples.

[0009] The third object of the present invention is to provide a cobalt-based porous carbon derivative for QuEChERS purification material for use in tobacco pesticide residue detection, so as to solve the problem of poor detection accuracy in the prior art when detecting pesticide residues in tobacco samples.

[0010] In order to solve the above technical problems, the technical solution of the cobalt-based porous carbon derivative for QuEChERS purification material of the present invention is:

[0011] A cobalt-based porous carbon derivative for QuEChERS purification material, the preparation method comprising the following steps: calcining ZIF-67 in an inert atmosphere to obtain a ZIF-67-derived carbon material, then subjecting the ZIF-67-derived carbon material to at least one acid treatment, washing with water, and drying to obtain the cobalt-based porous carbon derivative for QuEChERS purification material, wherein the total time of the acid treatment is 10 to 30 hours.

[0012] The present invention is an improvement on the prior art, and provides a cobalt-based porous carbon derivative for QuEChERS purification material. By acid-treating the calcined ZIF-67, the acid treatment can remove the unstable metal particles loaded by the calcined porous material, thereby obtaining a cobalt-based porous carbon derivative with a large specific surface area and high stability. The acid treatment operation can release a large number of adsorption sites, thereby significantly improving its purification performance, and the presence of stable metal sites and heteroatoms such as nitrogen, so that the cobalt-based porous carbon derivative has a variety of active sites, which can remove a wider range of matrix interferents, thereby improving the purification ability of tobacco sample matrix interferents, and is very suitable as a pre-treatment process for QuEChERS purification materials for tobacco sample pesticide residue detection; and the cobalt-based porous carbon derivative has a three-dimensional porous structure, which avoids the disadvantage that conventional two-dimensional purification materials are easy to agglomerate during actual use. The preparation method of the QuEChERS purification material provided by the present invention is simple, easy to implement, and can realize batch amplification preparation.

[0013] In order to further improve the attachment of unstable nano-cobalt particles on the surface of the three-dimensional porous carbon, preferably, the calcination temperature is 900-1100° C., and the calcination time is 5-7 hours.

[0014] In order to further improve the removal rate of unstable cobalt particles and increase the adsorption sites of porous carbon derivatives, preferably, the concentration of the acid solution used in each acid treatment is 0.5 to 2 mol L -1 .

[0015] In order to further improve the removal efficiency of unstable cobalt particles, preferably, the acid solution used in the acid treatment is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.

[0016] The ZIF-67 can be prepared by simple wet chemistry. In order to further regulate the ratio of metal particles in the organic metal framework, preferably, the preparation method of the ZIF-67 is as follows: cobalt salt and 2-methylimidazole are reacted in a solvent, filtered, washed and dried, the molar ratio of cobalt ions in the cobalt salt and 2-methylimidazole is (0.2 to 0.25): 1, and the reaction time is 6 to 48 hours.

[0017] The technical solution of the application of the cobalt-based porous carbon derivative for QuEChERS purification material in the sample pretreatment for tobacco pesticide residue detection is as follows:

[0018] An application of the cobalt-based porous carbon derivative for QuEChERS purification material in sample pretreatment during tobacco pesticide residue detection.

[0019] The present invention uses cobalt-based porous carbon derivatives as QuEChERS purification materials in the sample pretreatment process, and utilizes the large number of adsorption sites possessed by the cobalt-based porous carbon derivatives to adsorb and purify a wider range of matrix interferents in tobacco samples, thereby improving the purification ability for tobacco samples with complex matrices and more interferences, thereby helping to reduce the detection limit and quantification limit in subsequent pesticide residue detection and improving the accuracy of the detection results.

[0020] In order to further improve the impurity removal and purification capability of sample pretreatment, preferably, the following steps are included:

[0021] 1) mixing the tobacco sample soaked in water with acetonitrile, adding a salting-out agent, mixing and centrifuging to obtain a first supernatant;

[0022] 2) Adding the cobalt-based porous carbon derivative and anhydrous magnesium sulfate used for QuEChERS purification material to the first supernatant, mixing and centrifuging to obtain a second supernatant, and filtering to obtain a sample solution for detection.

[0023] In order to further improve the extraction ability of pesticide residues in tobacco samples, preferably, the ratio of the mass of the tobacco sample, the volume of water, the volume of acetonitrile and the mass of the salting-out agent in step 1) is (2-4) g: (10-15) mL: (10-15) mL: (6-7) g.

[0024] In order to further improve the purification ability of matrix interferents in tobacco samples, preferably, the ratio of the volume of the first supernatant, the mass of the cobalt-based porous carbon derivative, and the mass of anhydrous magnesium sulfate is (1-2) mL: (10-15) mg: (150-200) mg.

[0025] In order to further improve the extraction efficiency, preferably, the salting-out agent is composed of anhydrous magnesium sulfate, sodium chloride, sodium citrate and disodium hydrogen citrate, and the mass ratio of anhydrous magnesium sulfate, sodium chloride, sodium citrate and disodium hydrogen citrate is (4-5):(1-2):(1-2):(0.5-1).

[0026] In order to further improve the extraction efficiency of pesticide residues in tobacco samples, preferably, the mixing in steps 1)-2) is performed by oscillation mixing, and the oscillation speed during oscillation mixing is 2000-2500 rpm and the oscillation time is 2-5 min.

[0027] The technical solution of the application of the cobalt-based porous carbon derivative for QuEChERS purification material in tobacco pesticide residue detection is as follows:

[0028] An application of the cobalt-based porous carbon derivative for QuEChERS purification material in tobacco pesticide residue detection.

[0029] The application of the cobalt-based porous carbon derivative provided by the present invention in the detection of tobacco pesticide residues can greatly improve the purification ability of matrix interferences in tobacco samples by using the cobalt-based porous carbon derivative with a large number of adsorption sites as the QuEChERS purification material in the pretreatment process of tobacco samples, and detect pesticide residues in the pretreated samples, reduce the detection limit and quantitative limit during the detection of pesticide residues, and improve the accuracy and sensitivity of the detection results. The detection method of the present invention can detect 46 pesticides, and the 46 pesticides have a good linear relationship within the range of 2 to 200 μg / L, and the linear correlation coefficient (R) is greater than 0.997, and the detection limit and quantitative limit are 0.01 to 0.89 μg / kg and 0.03 to 2.97 μg / kg, respectively.

[0030] In order to further improve the detection accuracy, preferably, the tobacco sample is treated by the sample pretreatment method to obtain a sample solution for detection, and the pesticide residues in the sample solution are analyzed by LC-Q-TOF MS.

[0031] In order to further improve the detection accuracy, preferably, the chromatographic conditions of LC-Q-TOF MS analysis are as follows: the chromatographic column is an Atlantis@T3 chromatographic column; the column temperature is 30-40°C; the flow rate is 0.2-0.3 mL / min; the injection volume is 10-15 μL; the elution method is gradient elution; the mobile phase is composed of mobile phase A and mobile phase B, mobile phase A is an ammonium acetate solution containing 0.1-0.2% formic acid, and mobile phase B is acetonitrile; the gradient elution method is: 0-1 min, 10%-50% B; 1-5 min, 50% B; 5-16 min, 50%-60% B; 16-25 min, 60%-80% B; 25-30 min, 80%-95% B; 30-40 min, 95% B; 40-40.1 min, 95%-10% B; 40.1-50.1 min, 10% B.

[0032] In order to further improve the detection accuracy, preferably, the mass spectrometry conditions of LC-Q-TOF MS analysis are: ion source: ESI source; scanning mode: positive ion scanning; scanning range: 100-1000 m / z; spray voltage: 5500 V; nebulizing gas pressure: 55 psi; curtain gas pressure: 35 psi; auxiliary gas pressure: 50 psi; ion source temperature: 450-500°C; cluster fragmentation voltage: 40 V; collision energy: 10 eV (MS), 35 eV (MS / MS); collision energy diffusion: 15 eV; detection mode: information association acquisition mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The SEM morphology images of CZIFB and CZIFA of Example 1 of the present invention;

[0034] Figure 2 XRD patterns of ZIF67, CZIFB and CZIFA in Example 1 of the present invention;

[0035] Figure 3 is the N of CZIFB and CZIFA in Example 1 of the present invention 2 Adsorption-desorption isotherms;

[0036] Figure 4 This is a comparison chart of purification ability test results of the purification material of Example 1 of the present invention and other purification materials. DETAILED DESCRIPTION

[0037] The technical concept of the cobalt-based porous carbon derivative for QuEChERS purification material of the present invention is as follows:

[0038] The prior art utilizes the high specific surface area imparted by the three-dimensional porous carbon material of ZIF-67-derived carbon itself to adsorb matrix interferents in the process of pesticide detection and analysis, and utilizes the cobalt metal in the ZIF-67-derived carbon to impart magnetism to it to achieve efficient separation; while the present invention further removes the unstable cobalt particles loaded on the ZIF-67-derived carbon to release a large number of adsorption sites, rather than utilizing the magnetism imparted by the cobalt particles in the prior art, and synergizing with the active adsorption sites doped with stable metals and nitrogen, thereby being able to adsorb a wider range of matrix interferents, thereby greatly improving the purification capacity of matrix interferents.

[0039] The cobalt-based porous carbon derivative for QuEChERS purification material provided by the present invention is obtained by calcining ZIF-67 in an inert atmosphere to obtain a ZIF-67 derived carbon material, then subjecting the ZIF-67 derived carbon material to at least one acid treatment, washing with water, and drying.

[0040] In a specific embodiment, the ZIF-67-derived carbon material is subjected to 1 to 3 acid treatments, each of which lasts for 8 to 10 hours. Compared with a single acid treatment, the 3 acid treatments can fully utilize the effect of the acid solution in removing cobalt particles and more quickly remove unstable cobalt particles supported by the ZIF-67-derived carbon.

[0041] When the cobalt-based porous carbon derivative provided by the present invention is used as a QuEChERS purification material for pretreatment, the tobacco sample soaked in water is first mixed with acetonitrile, a salting-out agent is added, the mixture is centrifuged to obtain a first supernatant; then the cobalt-based porous carbon derivative and anhydrous magnesium sulfate are added to the first supernatant, the mixture is centrifuged to obtain a second supernatant, and the sample solution for detection is obtained after filtration.

[0042] In a specific embodiment, the centrifugal speed is 5000-8000 rpm, and the centrifugal time is 3-5 min.

[0043] In a specific embodiment, the tobacco sample soaked in water is obtained by adding the tobacco sample into water and shaking until the sample is fully soaked.

[0044] In a specific embodiment, after acetonitrile is added to the tobacco sample, an internal standard solution may be added for quantitative analysis during pesticide residue detection; the internal standard solution is a triphenyl phosphate solution, and the concentration of the internal standard solution is (10-15) μg / mL.

[0045] The cobalt-based porous carbon derivative provided by the present invention is used as a QuEChERS purification material to complete pre-treatment of a tobacco sample to obtain a sample solution, and the pesticide residues in the sample solution are analyzed by LC-Q-TOF MS.

[0046] In a specific embodiment, the pesticide includes thiodicarb, pendimethalin, ethophos sulfoxide, bisbenzimidazole, fenthion sulfoxide, phoxim, quinalphos, triadimefon, isothiocarb, pyraclostrobin, profenofos, fluazifop-butyl, indoxacarb, penconazole, hexythiazox, difenoconazole, butalin, ethophos, fenamiphos, fenamiphos sulfone, methyl pirimiphos, phosalone, propamide, triazophos, oxadone, chlorpyrifos, methyl demeton, malathion, ethophos sulfone, chlorpyrifos, chlorpyrifos, methyl demeton, malathion, ethophos sulfone, chlorpyrifos, chlorpyrifos, methacryloylmorph, phosphamidon, bensulfuron, terbufos sulfone, spirotetramat, cypermethrin, cadastrefos, isopropylamine, emamectin benzoate, rice blast, myclobutanil, bispyribac, fenamidone, thiamethoxam, and diazinon.

[0047] The embodiments of the present invention are further described below in conjunction with specific examples. The chemical reagents involved in the following examples are all commercially available conventional products unless otherwise specified.

[0048] 1. Specific embodiments of the cobalt-based porous carbon derivatives for QuEChERS purification materials of the present invention

[0049] Example 1

[0050] The cobalt-based porous carbon derivative used for the QuEChERS purification material of this embodiment is prepared as follows:

[0051] 1) Preparation of ZIF-67

[0052] Weigh 2.32 g Co(NO 3 ) 2 6H 2O (8 mmol) and 2.62 g 2-methylimidazole (32 mmol) were dissolved in 50 mL methanol to obtain a first solution and a second solution, respectively. The second solution was added to the first solution under stirring at room temperature, and the reaction was continued for 24 h. The precipitate was collected by vacuum filtration using a 0.22 μm filter membrane, washed with water and methanol for several times, and dried in a vacuum drying oven at 35 °C to obtain ZIF-67.

[0053] 2) Preparation of Co-based Porous Carbon Derivatives

[0054] ZIF-67 was calcined in a nitrogen atmosphere tube furnace at 900 °C for 5 h to obtain a ZIF-67 derived carbon material, which was recorded as CZIFB. CZIFB was added with 1 mol L -1 In HCl solution, CZIFB was treated with acid for 10 h under magnetic stirring, then taken out and repeatedly treated with 1 mol L -1 The solution was treated with acid twice, each time for 10 hours, and then washed with water for several times and dried in a vacuum drying oven at 35° C. The obtained product is the cobalt-based porous carbon derivative for QuEChERS purification material of the present invention, which is denoted as CZIFA.

[0055] Example 2

[0056] The preparation method of the cobalt-based porous carbon derivative used for QuEChERS purification material in this embodiment is basically the same as that in Example 1, except that: -1 CZIFB was treated with acid in HCl solution under magnetic stirring for 10 h, and then taken out and the acid treatment was repeated twice, each time for 10 h.

[0057] Example 3

[0058] The preparation method of the cobalt-based porous carbon derivative used for QuEChERS purification material in this embodiment is basically the same as that in Example 1, except that: -1 CZIFB was treated with acid in HCl solution under magnetic stirring for 10 h, and then taken out and the acid treatment was repeated twice, each time for 10 h.

[0059] Example 4

[0060] The preparation method of the cobalt-based porous carbon derivative used for QuEChERS purification material in this embodiment is basically the same as that in Example 1, except that: -1 CZIFB was treated with acid once in HCl solution under magnetic stirring for 10 h.

[0061] Example 5

[0062] The preparation method of the cobalt-based porous carbon derivative used for QuEChERS purification material in this embodiment is basically the same as that in Example 1, except that: -1 CZIFB was treated with acid twice in HCl solution under magnetic stirring, and each treatment lasted for 10 h.

[0063] 2. Specific examples of the application of the cobalt-based porous carbon derivative for QuEChERS purification material of the present invention in sample pretreatment for tobacco pesticide residue detection

[0064] Example 2

[0065] The cobalt-based porous carbon derivative used for QuEChERS purification material in this embodiment is used in sample pretreatment for tobacco pesticide residue detection, and the specific method is as follows:

[0066] 1) Weigh about 2.00 g of cigarette dust sample into a 50 mL stoppered centrifuge tube, add 10 mL of water and shake until the sample is fully infiltrated, then let it stand for 10 min, then add 10 mL of acetonitrile and 20 μL of 10 μg / mL triphenyl phosphate internal standard solution, and shake at 2000 rpm for 2 min; after placing the centrifuge tube at -20°C for 10 min, add 4 g of anhydrous magnesium sulfate, 1 g of sodium chloride, 1 g of sodium citrate and 0.5 g of disodium hydrogen citrate in sequence, immediately shake at 2000 rpm for 2 min, and then centrifuge at 5000 rpm for 3 min to obtain a first supernatant.

[0067] 2) Take 1 mL of the first supernatant in step 1) in a 2 mL centrifuge tube, add 150 mg of anhydrous magnesium sulfate and 10 mg of CZIFA of Example 1, shake for 2 min and then centrifuge to obtain a second supernatant, and obtain a sample solution for detection after filtering through a membrane.

[0068] 3. Specific examples of the application of the cobalt-based porous carbon derivative for QuEChERS purification material of the present invention in tobacco pesticide residue detection

[0069] Example 3

[0070] The application of the cobalt-based porous carbon derivative used for QuEChERS purification material in tobacco pesticide residue detection in this embodiment is as follows:

[0071] The cobalt-based porous carbon derivative used for QuEChERS purification material in Example 2 was used for sample pretreatment in tobacco pesticide residue detection to obtain a sample solution for detection, and the pesticide residues in the sample solution were analyzed by LC-Q-TOF MS.

[0072] The chromatographic conditions for LC-Q-TOF MS analysis are as follows: the chromatographic column is an Atlantis@T3 chromatographic column (column length 150 mm, inner diameter 2.1 mm, stationary phase particles 3 μm); the column temperature is 40°C; the flow rate is 0.2 mL / min; the injection volume is 10 μL; the elution method is gradient elution; the mobile phase consists of mobile phase A and mobile phase B, mobile phase A is ammonium acetate solution (5 mmol / L) containing 0.1% formic acid, and mobile phase B is acetonitrile; the gradient elution method is: 0-1 min, 10%-50% B; 1-5 min, 50% B; 5-16 min, 50%-60% B; 16-25 min, 60%-80% B; 25-30 min, 80%-95% B; 30-40 min, 95% B; 40-40.1 min, 95%-10% B; 40.1-50.1 min, 10% B.

[0073] The mass spectrometry conditions for LC-Q-TOF MS analysis were as follows: ion source: ESI source; scanning mode: positive ion scanning; scanning range: 100-1000 m / z; spray voltage: 5500 V; nebulizer gas pressure: 55 psi; curtain gas pressure: 35 psi; auxiliary gas pressure: 50 psi; ion source temperature: 500 °C; cluster fragmentation voltage: 40 V; collision energy: 10 eV (MS), 35 eV (MS / MS); collision energy diffusion: 15 eV; detection mode: information-associated acquisition mode (intensity threshold: 10 cps; m / z range: 10-1000 Da; mass tolerance, 50 mDa; dynamic background subtraction).

[0074] 4. Comparative Proportion

[0075] Comparative Example 1

[0076] The application of the cobalt-based porous carbon derivative for QuEChERS purification material in the sample pretreatment for tobacco pesticide residue detection in this comparative example is basically the same as that in Example 2, except that CZIFA in step 2) is replaced by CZIFB.

[0077] Comparative Example 2

[0078] The application of the cobalt-based porous carbon derivative for QuEChERS purification material in the sample pretreatment for tobacco pesticide residue detection in this comparative example is basically the same as that in Example 2, except that: CZIFA in step 2) is replaced by PSA.

[0079] Comparative Example 3

[0080] The application of the cobalt-based porous carbon derivative for QuEChERS purification material in the sample pretreatment for tobacco pesticide residue detection in this comparative example is basically the same as that in Example 2, except that CZIFA in step 2) is replaced by GCB.

[0081] Comparative Example 4

[0082] The application of the cobalt-based porous carbon derivative for QuEChERS purification material in the sample pretreatment for tobacco pesticide residue detection in this comparative example is basically the same as that in Example 2, except that: CZIFA in step 2) is replaced by C18.

[0083] V. Experimental Examples

[0084] Experimental Example 1

[0085] This experimental example tests the physicochemical properties of cobalt-based porous carbon derivatives used as QuEChERS purification materials.

[0086] 1) SEM

[0087] The morphology and microstructure of CZIFB and CZIFA of Example 1 were characterized by scanning electron microscopy (SEM). Figure 1 For CZIFB( Figure 1 (a)) and CZIFA ( Figure 1 (b)) SEM morphology, from Figure 1 From the SEM morphology, it can be seen that both CZIFB and CZIFA have three-dimensional porous structures. Nanoparticles are attached to the three-dimensional porous carbon surface of CZIFB, while the nanoparticles on the surface of CZIFA disappear after acid washing. This shows that the acid treatment operation can remove the nanoparticles on the porous carbon surface.

[0088] 2) XRD

[0089] The crystal structures of CZIFB and CZIFA of Example 1 were characterized by XRD. Figure 2 The XRD patterns of ZIF67, CZIFB and CZIFA are shown in Figure 2. Figure 2It can be seen that the four diffraction peaks at 7.4°, 10.4°, 12.8° and 18.0° correspond to the (011), (002), (112) and (222) crystal planes of ZIF-67 crystals, respectively. This result directly proves the successful preparation of ZIF-67; the XRD spectrum of CZIFB obtained by directly calcining ZIF-67 in nitrogen atmosphere shows three diffraction peaks at 44.2°, 51.4° and 75.7°, which correspond to the (111), (200) and (220) crystal planes of face-centered cubic Co particles, respectively (JCPDS cardNo.15-0806); in the XRD spectrum of CZIFA obtained after acid treatment of CZIFB, the three diffraction peaks of the above cobalt particles all disappeared, which is consistent with the results of SEM; in addition, two new diffraction peaks appeared at ~25° and ~43°, which were respectively attributed to the (002) and (101) crystal planes of graphite carbon. Combined with the SEM image of CZIFB, it can be seen that the two diffraction peaks of graphite carbon were not observed in the XRD spectrum of CZIFB because a large amount of cobalt particles were filled and loaded on the porous carbon; after acid treatment, the diffraction peaks of cobalt particles disappeared, accompanied by a significant increase in the intensity of the diffraction peaks of graphite carbon, which also indicates that a large number of unstable cobalt particles have been removed by the acid treatment operation.

[0090] 3) BET

[0091] The specific surface area and pore size distribution of CZIFB and CZIFA were characterized by surface area analyzer. Figure 3 is the N of CZIFB and CZIFA in Example 1 2 According to the IUPAC classification standard, the adsorption-desorption isotherm is Figure 3 It can be seen that CZIFB and CZIFA present typical type IV isotherms with H3 hysteresis loops, which indicates that CZIFB and CZIFA have typical mesoporous structures. In addition, by measuring the nitrogen adsorption at different pressure points, the specific surface area of ​​CZIFA was fitted using the BET formula to be 430.0 m 2 g -1 , which is much larger than the specific surface area of ​​CZIFB (187.3m 2 g -1 ); In addition, after acid treatment, the pore volume of CZIFB increased from 0.182 cm 3 g -1 Increased to 0.419cm for CZIFA 3 g -1 , indicating that the acid treatment operation released a large number of adsorption sites.

[0092] Experimental Example 2

[0093] This experimental example tests the purification ability of cobalt-based porous carbon derivatives used as QuEChERS purification materials.

[0094] The effect of acid treatment on the purification performance of QuEChERS purification materials was evaluated by the evaporation residue weight method. The specific operation of the evaporation residue weight method is: after purifying the tobacco sample according to the pretreatment method of Example 2, take 0.5 mL of the purified extract (filtered sample solution) into a clean chromatographic bottle weighed in advance, blow it with nitrogen first, then put it in an 80°C oven for 2 hours, take it out and cool it in a desiccator, and weigh the chromatographic bottle containing the remaining co-extracts using an analytical balance. The difference between the two weighings is the amount of the co-extracted matrix, and repeat three times.

[0095] The purification ability test results of the cobalt-based porous carbon derivatives used for QuEChERS purification materials in Examples 1-5 are shown in Table 1. As can be seen from Table 1, the amount of matrix extracted by the purification materials provided by the present invention is less than 33 mg / g, showing good matrix interference purification ability. As the acid concentration used in the acid treatment increases, the amount of matrix extracted becomes lower and lower, but 1 mol L -1 and 2 mol L -1 After the acid treatment with the acid solution, the amount of matrix extracted by the purification material has not changed significantly; and as the acid treatment time increases, the amount of matrix extracted is getting lower and lower. It should be noted that as the number of acid washings increases, there is no negative effect on the performance of the purification material.

[0096] Table 1 Purification ability test results of purification materials of Examples 1-5

[0097]

[0098] also, Figure 4 This is a comparison chart of the purification ability test results of QuEChERS purification materials. Figure 4 It can be seen that the CZIFB before acid washing in Example 1 can only reduce the amount of co-extracted matrix from 61.4 mg / g to 48.8 mg / g, while the CZIFA after acid washing can further reduce the amount of co-extracted matrix to 27.9 mg / g, which indicates that CZIFB has poor purification ability compared with CZIFA. Combined with the characterization results of Experimental Example 1, it can be seen that the weak purification ability of CZIFB on tobacco matrix is ​​due to the large number of cobalt particles covering the adsorption sites. Therefore, the acid treatment strategy can indeed significantly improve the purification performance of CZIFA.

[0099] The purification performance of the obtained CZIFA was further compared with that of traditional purification materials such as GCB, C18 and PSA. Figure 4It can be seen that the prepared CZIFA exhibits better purification performance than traditional purification adsorbents and even classic PSA adsorbents.

[0100] Experimental Example 3

[0101] When using LC-Q-TOF MS to analyze pesticide residues in sample solutions, it is necessary to first create a working curve for the pesticide to be tested.

[0102] The process of making the working curve of the pesticide to be tested is as follows:

[0103] Accurately weigh 10.0 mg of triphenyl phosphate (TPP) standard, place it in a 10 mL volumetric flask, dilute it with acetonitrile and make up to volume to obtain an internal standard stock solution with a concentration of 1000 μg / mL, transfer 1.0 mL of the internal standard stock solution into a 100 mL volumetric flask, dilute it with acetonitrile and make up to volume to obtain an internal standard solution with a concentration of 10 μg / mL.

[0104] Weigh 0.01g (accurate to 0.0001g) of each pesticide standard substance in a 10mL volumetric flask, dilute with acetonitrile to make a 1000μg / mL single stock standard solution, transfer 0.5mL of each pesticide single stock standard solution to a 100mL volumetric flask, dilute to the mark with acetonitrile, and make a mixed standard working solution (5μg / mL) of each pesticide. Dilute the mixed standard working solution with a concentration of 5μg / mL with acetonitrile to obtain a series of standard solutions with concentrations of 2, 5, 10, 20, 50, 100 and 200ng / mL (add 0.5mL of 10μg / mL internal standard solution to each volumetric flask, and the internal standard concentration is 20ng / mL).

[0105] The blank tobacco sample (without pesticide residue) was purified by the pretreatment method of Example 2 to obtain the purified blank extract. 0.5 mL of the blank extract was taken, blown to dryness with nitrogen, and then redissolved with 0.5 mL of a series of standard solutions to obtain a series of matrix-matched standard solutions with concentrations of 2, 5, 10, 20, 50, 100 and 200 ng / mL, respectively. After LC-Q-TOF MS analysis of the above series of matrix-matched standard solutions, linear regression analysis was performed, and the detection limit and quantification limit were determined by 3 times and 10 times the signal-to-noise ratio, respectively. At the same time, the spiked recovery rates of 3 addition levels (20, 50 and 200 μg / kg) were also investigated. The test results are shown in Table 2.

[0106] As can be seen from Table 2, the 46 pesticides had a good linear relationship in the range of 2-200 μg / L, and the linear correlation coefficients (R) were all greater than 0.997. The detection limits and quantification limits were 0.01-0.89 μg / kg and 0.03-2.97 μg / kg, respectively.

[0107] The mixed standard working solutions of low, medium and high mass concentration levels were added to the blank tobacco samples to prepare spiked samples of 20, 50 and 200 μg / kg, respectively. The spiked samples were treated according to the pretreatment method in Example 2, and the pesticides in the solution to be tested were analyzed by the LC-Q-TOF MS method in Example 3 after the sample pretreatment, and then the concentration of each pesticide was calculated according to the prepared working curve, and then the spiked recovery was calculated. Each level was repeated 6 times, and the recovery and relative standard deviation (RSD) are shown in Table 2. The spiked recovery at the three spiked levels was between 80.4% and 119.4%, and the relative standard deviation (RSD, n=6) was less than 11.9%. It can be seen that the recovery and precision of the detection method established by the pretreatment method provided by the present invention are good.

[0108] Table 2 Retention time (RT), linear correlation coefficient (R), spike recovery (n=6), RSD, detection limit and quantification limit test results of 46 pesticides

[0109]

[0110]

[0111] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A cobalt-based porous carbon derivative for QuEChERS purification material, characterized in that: The preparation method comprises the following steps: calcining ZIF-67 in an inert atmosphere to obtain a ZIF-67-derived carbon material, then subjecting the ZIF-67-derived carbon material to at least one acid treatment, washing with water, and drying to obtain a cobalt-based porous carbon derivative for QuEChERS purification material, wherein the total time of the acid treatment is 10 to 30 hours.

2. The cobalt-based porous carbon derivative for QuEChERS purification material according to claim 1, characterized in that: The calcination temperature is 900-1100° C., and the calcination time is 5-7 hours.

3. The cobalt-based porous carbon derivative for QuEChERS purification material according to claim 1, characterized in that: The acid solution concentration used in each acid treatment was 0.5~2 mol L -1 .

4. The cobalt-based porous carbon derivative for QuEChERS purification material according to claim 1 or 3, characterized in that: The acid solution used in the acid treatment is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.

5. The cobalt-based porous carbon derivative for QuEChERS purification material according to claim 1, characterized in that: The preparation method of ZIF-67 is as follows: cobalt salt and 2-methylimidazole are reacted in a solvent, filtered, washed and dried, the molar ratio of cobalt ions in the cobalt salt and 2-methylimidazole is (0.2-0.25):1, and the reaction time is 6-48 hours.

6. Use of the cobalt-based porous carbon derivative for QuEChERS purification material as claimed in any one of claims 1 to 5 in sample pretreatment for tobacco pesticide residue detection.

7. Use of the cobalt-based porous carbon derivative for QuEChERS purification material as claimed in claim 6 in sample pretreatment for tobacco pesticide residue detection, characterized in that: The following steps are involved: 1) mixing the tobacco sample soaked in water with acetonitrile, adding a salting-out agent, mixing and centrifuging to obtain a first supernatant; 2) Adding the cobalt-based porous carbon derivative and anhydrous magnesium sulfate used for QuEChERS purification material to the first supernatant, mixing and centrifuging to obtain a second supernatant, and filtering to obtain a sample solution for detection.

8. Use of the cobalt-based porous carbon derivative for QuEChERS purification material in sample pretreatment for tobacco pesticide residue detection according to claim 7, characterized in that: In the step 1), the ratio of the mass of the tobacco sample, the volume of water, the volume of acetonitrile and the mass of the salting-out agent is (2-4) g: (10-15) mL: (10-15) mL: (6-7) g.

9. Use of the cobalt-based porous carbon derivative for QuEChERS purification material in sample pretreatment for tobacco pesticide residue detection according to claim 7, characterized in that: The ratio of the volume of the first supernatant, the mass of the cobalt-based porous carbon derivative, and the mass of anhydrous magnesium sulfate is (1-2) mL: (10-15) mg: (150-200) mg.

10. Use of the cobalt-based porous carbon derivative for QuEChERS purification material in sample pretreatment for tobacco pesticide residue detection according to claim 7, characterized in that: The salting-out agent is composed of anhydrous magnesium sulfate, sodium chloride, sodium citrate and disodium hydrogen citrate, and the mass ratio of the anhydrous magnesium sulfate, sodium chloride, sodium citrate and disodium hydrogen citrate is (4-5): (1-2): (1-2): (0.5-1).

11. Use of the cobalt-based porous carbon derivative for QuEChERS purification material in sample pretreatment for tobacco pesticide residue detection according to claim 7, characterized in that: The mixing in steps 1)-2) is performed by oscillating mixing, and the oscillation speed during oscillating mixing is 2000-2500 rpm, and the oscillation time is 2-5 min.

12. Use of the cobalt-based porous carbon derivative for QuEChERS purification material according to any one of claims 1 to 5 in the detection of pesticide residues in tobacco.

13. The use of the cobalt-based porous carbon derivative for QuEChERS purification material in tobacco pesticide residue detection according to claim 12, characterized in that: The tobacco sample is treated by the sample pretreatment method according to claims 6 to 11 to obtain a sample solution for detection, and the pesticide residues in the sample solution are analyzed by LC-Q-TOF MS.

14. The use of the cobalt-based porous carbon derivative for QuEChERS purification material in tobacco pesticide residue detection according to claim 13, characterized in that: The chromatographic conditions of LC-Q-TOF MS analysis were as follows: the chromatographic column was Atlantis@T3 column; the column temperature was 30-40°C; the flow rate was 0.2-0.3 mL / min; the injection volume was 10-15 μL; the elution method was gradient elution; the mobile phase consisted of mobile phase A and mobile phase B, mobile phase A was ammonium acetate solution containing 0.1-0.2% formic acid, and mobile phase B was acetonitrile; the gradient elution method was: 0-1 min, 10%-50% B; 1-5 min, 50% B; 5-16 min, 50%-60% B; 16-25 min, 60%-80% B; 25-30 min, 80%-95% B; 30-40 min, 95% B; 40~40.1 min, 95%~10% B; 40.1~50.1min, 10% B.

15. The use of the cobalt-based porous carbon derivative for QuEChERS purification material in tobacco pesticide residue detection according to claim 13, characterized in that: The mass spectrometry conditions for LC-Q-TOF MS analysis were as follows: ion source: ESI source; scanning mode: positive ion scanning; scanning range: 100-1000 m / z; spray voltage: 5500 V; nebulizer gas pressure: 55 psi; curtain gas pressure: 35 psi; Auxiliary gas pressure: 50 psi; ion source temperature: 450~500℃; cluster fragmentation voltage: 40 V; collision energy: 10 eV (MS), 35 eV (MS / MS); collision energy spread: 15 eV; detection mode: information correlation acquisition mode.

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