Low-zinc-based porous carbon derivative for QuEChERS purification material and application of low-zinc-based porous carbon derivative in sample pretreatment and tobacco pesticide residue detection

Abstract

The invention relates to the technical field of pesticide residue detection, in particular to a low-zinc-based porous carbon derivative for a QuEChERS purification material and application of the low-zinc-based porous carbon derivative in sample pretreatment and tobacco pesticide residue detection. The preparation method of the low-zinc-based porous carbon derivative for the QuEChERS purification material comprises the following steps that ZIF-8 is calcined in an inert atmosphere to obtain the low-zinc-based porous carbon derivative, the calcination temperature is 900-1100 DEG C, the calcination time is 3-7 h, and the proportion of zinc atoms on the surface of the low-zinc-based porous carbon derivative is not higher than 1.1%. Zinc atoms and a porous structure in the porous carbon derivative are regulated and controlled by controlling the calcination temperature and time of ZIF-8, so that the porous carbon derivative has relatively large specific surface area, pore volume and carbon content and relatively rich element chemical states, and enhanced removal of a wider range of matrix interferents can be realized; further, the capability of purifying 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 low-zinc-based porous carbon derivative for QuEChERS purification material and its application in sample pretreatment and tobacco pesticide residue detection. Background Art

[0002] Due to the extensive use and abuse of pesticides, pesticide residues are found in tobacco. However, 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. By heating ZIF-67 to 600-800°C in an inert gas atmosphere and annealing and carbonizing it for 1 to 2 hours, the obtained ZIF-67-derived carbon material is used as a magnetic purifier for QuEChERS pesticide residue analysis, and pesticide residues in 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 is still limited in its ability to purify interferences in the matrix when used as a QuEChERS purification material in tobacco samples with complex matrices and more interferences. Summary of the invention

[0007] The purpose of the present invention is to provide a low zinc-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 low zinc-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 the prior art for matrix interferences in tobacco samples.

[0009] The third object of the present invention is to provide a low zinc-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 low zinc-based porous carbon derivative for QuEChERS purification material of the present invention is:

[0011] A low-zinc-based porous carbon derivative for QuEChERS purification material, the preparation method comprising the following steps: calcining ZIF-8 in an inert atmosphere to obtain a low-zinc-based porous carbon derivative, the calcination temperature is 900-1100°C, the calcination time is 5-7h, and the zinc atom proportion on the surface of the low-zinc-based porous carbon derivative is no more than 1.1%.

[0012] The present invention improves the prior art and provides a low zinc-based porous carbon derivative. By controlling the calcination temperature and time of ZIF-8, the controllable preparation of zinc-based porous carbon derivatives with large specific surface area and high stability is achieved, and the high-temperature volatilization process of zinc atoms in the porous carbon derivative can be controlled, thereby realizing the regulation of the porous structure in the zinc-based porous carbon derivative; the zinc-based porous carbon derivative prepared by the present invention has a large specific surface area, pore volume, carbon content and a richer element chemical state, and can achieve enhanced removal of a wider range of matrix interferences, thereby improving the purification ability of tobacco sample matrix interferences, and is very suitable as a pre-treatment process for QuEChERS purification materials for tobacco sample pesticide residue detection; the zinc-based porous carbon derivative prepared by the present invention has a three-dimensional porous structure of a rhombic dodecahedron, 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 increase the specific surface area and pore volume of the zinc-based porous carbon derivative, and thus improve the purification ability of matrix interferents, preferably, the calcination temperature is 1000-1100°C, and the proportion of zinc atoms on the surface of the low-zinc-based porous carbon derivative is not higher than 0.15%.

[0014] In order to further improve the adsorption capacity of matrix interferents, preferably, the calcination temperature is 1095-1100° C., and the zinc atom ratio on the surface of the low-zinc-based porous carbon derivative is 0.

[0015] The ZIF-8 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-8 is as follows: zinc salt and 2-methylimidazole are reacted in a solvent, filtered, washed and dried, the molar ratio of zinc ions in the zinc salt and 2-methylimidazole is (0.2-0.25):1, and the reaction time is 6-48h.

[0016] The technical solution of the application of the low zinc-based porous carbon derivative for QuEChERS purification material in the sample pretreatment for tobacco pesticide residue detection is as follows:

[0017] An application of the low zinc-based porous carbon derivative for QuEChERS purification material in sample pretreatment during tobacco pesticide residue detection.

[0018] The present invention uses zinc-based porous carbon derivatives as QuEChERS purification materials in the sample pretreatment process, and utilizes the zinc-based porous carbon derivatives with large specific surface area, pore volume, carbon content and rich elemental chemical states, so as to adsorb and purify a wider range of matrix interferences in tobacco samples, thereby improving the purification ability of tobacco samples with complex matrices and more interferences, thereby helping to reduce the detection limit and quantification limit in subsequent pesticide residue detection and improve the accuracy of the detection results.

[0019] In order to further improve the impurity removal and purification capability of sample pretreatment, preferably, the following steps are included:

[0020] 1) mixing the tobacco sample soaked in water with acetonitrile, adding a salting-out agent, mixing and centrifuging to obtain a first supernatant;

[0021] 2) Adding the low-zinc-based porous carbon derivative and anhydrous magnesium sulfate to the first supernatant, mixing and centrifuging to obtain a second supernatant, and filtering to obtain a sample solution for detection.

[0022] 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.

[0023] 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 zinc-based porous carbon derivative, and the mass of anhydrous magnesium sulfate is (1-2) mL: (10-15) mg: (150-200) mg.

[0024] 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).

[0025] 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.

[0026] The technical solution of the application of the low zinc-based porous carbon derivative for QuEChERS purification material in tobacco pesticide residue detection of the present invention is as follows:

[0027] An application of the low zinc-based porous carbon derivative for QuEChERS purification material in tobacco pesticide residue detection.

[0028] The application of the zinc-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 zinc-based porous carbon derivative with large specific surface area, pore volume, carbon content and rich element chemical state as QuEChERS purification material in the pretreatment process of tobacco samples, and can reduce the detection limit and quantitative limit of pesticide residue detection in the pretreated samples, thereby improving the accuracy and sensitivity of the detection results. The detection method of the present invention can detect 30 pesticides, and the 30 pesticides have a good linear relationship within the range of 2 to 200 μg / L, and the linear correlation coefficient (R) is greater than 0.996, and the detection limit and quantitative limit are 0.01 to 0.78 μg / kg and 0.02 to 2.59 μg / kg, respectively.

[0029] 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.

[0030] In order to further improve the accuracy of pesticide detection, 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.

[0031] In order to further improve the accuracy of pesticide detection, 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; atomizing 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

[0032] Figure 1These are SEM morphology images of C900, C1000 and C1100 prepared in the present invention;

[0033] Figure 2 The XRD patterns of ZIF-8, C900, C1000 and C1100 prepared by the present invention;

[0034] Figure 3 N2 adsorption-desorption isotherms of C900, C1000 and C1100 prepared by the present invention;

[0035] Figure 4 This is a graph showing the pore volume test results of C900, C1000 and C1100 prepared by the present invention;

[0036] Figure 5 This is a comparison chart of purification ability test results of C900, C1000 and C1100 prepared by the present invention and other purification materials. DETAILED DESCRIPTION

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

[0038] The prior art is to increase the cobalt ions in the process of synthesizing ZIF-67, thereby increasing the specific surface area and magnetic strength of the derived carbon material obtained by annealing and carbonization, thereby improving the adsorption capacity of interferences in the pesticide analysis process, and the rapid separation of the purifier and the sample matrix brought by the magnetic strength. Compared with the prior art, the present invention is to regulate the calcination parameters of ZIF-8 and then regulate the proportion of zinc atoms and the specific surface area, pore volume and rich chemical element state of porous carbon, so as to adsorb a wider range of matrix interferences, thereby greatly improving the purification capacity of matrix interferences.

[0039] The low-zinc-based porous carbon derivative provided by the present invention is used as a QuEChERS purification material to pre-treat a tobacco sample. The tobacco sample soaked in water is first mixed with acetonitrile, a salting-out agent is added, the mixture is mixed and centrifuged to obtain a first supernatant; the low-zinc-based porous carbon derivative and anhydrous magnesium sulfate are then added to the first supernatant, the mixture is mixed and centrifuged to obtain a second supernatant, and the sample solution for detection is obtained after filtration.

[0040] In a specific embodiment, the centrifugal speed is 5000-8000 rpm, and the centrifugal time is 3-5 min.

[0041] 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.

[0042] 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.

[0043] After pre-treating a tobacco sample using the low-zinc-based porous carbon derivative provided by the present invention as a QuEChERS purification material, a sample solution is obtained, and the pesticide residues in the sample solution are analyzed using LC-Q-TOF MS.

[0044] In a specific embodiment, the pesticide includes thiodicarb, pendimethalin, ethiophos sulfoxide, isopimide, fenthion sulfoxide, phoxim, quinalphos, triadimefon, clomazone, pyraclostrobin, profenofos, fluazifop-butyl, indoxacarb, penconazole, hexythiazox, difenoconazole, butalin, ethiophos, fenamiphos, fenamiphos sulfone, methyl pirimiphos, phosalone, pyrifos, triazophos, azophos, chlorfenapyr, ethophos, thiophanate-methyl, chlorfenapyr, ethophos, thiophanate-methyl, chlorfenapyr, ethophos, thiophanate-methyl, manganese salt of prochloraz, and tebuconazole.

[0045] 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.

[0046] 1. Specific embodiments of low zinc-based porous carbon derivatives for QuEChERS purification materials of the present invention

[0047] Example 1

[0048] The preparation method of the low zinc-based porous carbon derivative used for QuEChERS purification material in this embodiment is as follows:

[0049] 1) Preparation of ZIF-8

[0050] 2.38 g Zn(NO3)2·6H2O (8 mmol) and 2.62 g 2-methylimidazole (32 mmol) were weighed and 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 resulting precipitate was collected by vacuum filtration using a 0.22 μm filter membrane, washed with water and methanol several times, and dried in a vacuum drying oven at 35 °C to obtain ZIF-8.

[0051] 2) Preparation of Zn-based porous carbon derivatives

[0052] The ZIF-8 obtained in step 1) is placed in a tubular furnace in a nitrogen atmosphere and calcined at 900° C. for 5 h to obtain a zinc-based porous carbon derivative. The obtained product is the low zinc-based porous carbon derivative of the present invention, denoted as C900.

[0053] Example 2

[0054] The preparation method of the low zinc-based porous carbon derivative used for QuEChERS purification material in this embodiment is basically the same as that in Example 1, except that: in step 2), the low zinc-based porous carbon derivative is calcined at 1000° C. for 5 hours to obtain a low zinc-based porous carbon derivative, which is recorded as C1000.

[0055] Example 3

[0056] The preparation method of the low zinc-based porous carbon derivative used for QuEChERS purification material in this embodiment is basically the same as that in Example 1, except that: in step 2), the low zinc-based porous carbon derivative is calcined at 1100° C. for 5 hours to obtain a low zinc-based porous carbon derivative, which is recorded as C1100.

[0057] 2. Specific examples of the application of the low zinc-based porous carbon derivative for QuEChERS purification materials of the present invention in sample pretreatment for tobacco pesticide residue detection

[0058] Example 4

[0059] The application of the low zinc-based porous carbon derivative for QuEChERS purification material in this embodiment in sample pretreatment for tobacco pesticide residue detection is as follows:

[0060] 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.

[0061] 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 C900 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.

[0062] Example 5

[0063] The application of the low zinc-based porous carbon derivative for QuEChERS purification material in the sample pretreatment for tobacco pesticide residue detection in this embodiment is basically the same as that in Example 4, except that: 150 mg of anhydrous magnesium sulfate and 10 mg of C1000 in Example 2 are added in step 2).

[0064] Example 6

[0065] The application of the low zinc-based porous carbon derivative for QuEChERS purification material in the sample pretreatment for tobacco pesticide residue detection in this embodiment is basically the same as that in Example 4, except that: 150 mg of anhydrous magnesium sulfate and 10 mg of C1100 in Example 3 are added in step 2).

[0066] 3. Specific examples of the application of the low zinc-based porous carbon derivative for QuEChERS purification materials of the present invention in tobacco pesticide residue detection

[0067] Example 7

[0068] The application of the low zinc-based porous carbon derivative for QuEChERS purification material in tobacco pesticide residue detection in this embodiment is as follows:

[0069] The low zinc-based porous carbon derivative of Example 6 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.

[0070] 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.

[0071] 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).

[0072] 4. Comparative Proportion

[0073] Comparative Example 1

[0074] The application of the low zinc-based porous carbon derivative for QuEChERS purification material in this comparative example in sample pretreatment for tobacco pesticide residue detection is basically the same as that in Example 2, except that CZIFA in step 2) is replaced by PSA.

[0075] Comparative Example 2

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

[0077] Comparative Example 3

[0078] The application of the low zinc-based porous carbon derivative for QuEChERS purification material in this comparative example in sample pretreatment for tobacco pesticide residue detection is basically the same as that in Example 2, except that CZIFA in step 2) is replaced by C18.

[0079] V. Experimental Examples

[0080] Experimental Example 1

[0081] This experimental example tests the physicochemical properties of low zinc-based porous carbon derivatives.

[0082] 1) SEM

[0083] The morphology and microstructure of C900, C1000 and C1100 of Examples 1-3 were characterized by scanning electron microscopy (SEM). Figure 1 As stated, Figure 1 (a)-(c) are SEM images of C900, C1000 and C1100 respectively. Figure 1 It can be seen that C900, C1000 and C1100 all present a rhombic dodecahedron structure. With the increase of calcination temperature, the particle size of the porous carbon derivative CZIF shows a decreasing trend. Especially when the calcination temperature is increased from 900°C to 1000°C, CZIF shrinks significantly and the surface becomes rougher. This is due to the regulatory effect of zinc atoms on the porous structure during high-temperature volatilization.

[0084] 2) XRD

[0085] The crystal structures of C900, C1000 and C1100 of Examples 1-3 were characterized by XRD. Figure 2 The XRD patterns of ZIF-8, C900, C1000 and C1100 are shown in Table 1. Figure 2 It can be seen that in 7.4ο , 10.4 ο , 12.8 ο and 18.0 ο The four diffraction peaks that appear at correspond to the (011), (002), (112) and (222) crystal planes of ZIF-8 crystal, respectively. This result directly proves the successful preparation of ZIF-8. In the XRD patterns of C900, C1000 and C1100 obtained by directly calcining ZIF-8 in a nitrogen atmosphere, the characteristic diffraction peaks of ZIF-8 completely disappear, but the diffraction peaks of nanoparticles do not appear, indicating that the zinc atoms in ZIF-8 are not converted into zinc nanoparticles during the high-temperature calcination process.

[0086] 3) BET and pore volume

[0087] The specific surface area and pore size distribution of C900, C1000 and C1100 of Examples 1-3 were characterized using a specific surface area analyzer. Figure 3 is the N2 adsorption-desorption isotherms of C900, C1000 and C1100. According to the IUPAC classification standard, Figure 3 It can be seen that the adsorption-desorption isotherms of C900, C1000 and C1100 are between type I and type II isotherms. By measuring the nitrogen adsorption at different pressure points, the specific surface areas of C900, C1000 and C1100 were fitted using the BET formula. As the calcination temperature increased from 900℃ to 1000℃, the specific surface area of ​​CZIF increased from 1054.4m 2 g -1 Increased to 1714.8m 2 g -1 By further increasing the calcination temperature to 1100 °C, the specific surface area of ​​CZIF further increased to 1886.7 m 2 g -1 .

[0088] The pore volume test results of C900, C1000 and C1100 of Examples 1-3 are shown in the figure below: Figure 4 Similarly, as the calcination temperature increases from 900 °C to 1000 °C, the pore volume of CZIF increases from 0.506 cm 3 g -1 Increased to 0.935cm 3 g -1 When the calcination temperature was further increased to 1100 °C, the pore volume of CZIF was further increased to 1.002 cm 3 g -1 .

[0089] 4) XPS

[0090] The surface elemental composition of C900, C1000 and C1100 of Examples 1-3 was characterized by XPS. For C900 and C1000, both materials have four elements of C, N, O and Zn, but the percentage of Zn atoms on the surface of C1000 decreases from 1.08% of C900 to 0.13%. As the calcination temperature is further increased to 1100°C, no Zn atoms are detected, indicating that the Zn atoms have completely volatilized at a calcination temperature of 1100°C. The chemical states of C and N in CZIF are analyzed using XPS peak separation software. CZIF has rich C chemical states, namely CC, C-OH and C=N, COC, C=O and CN and COOH. Among them, as the calcination temperature is increased from 900°C to 1000°C, and further increased to 1000°C, the atomic percentage of CC increases from 69.1% to 76.4%, and further increases to 76.8%. CZIF also has rich N chemical states, namely pyridinic N, pyrrolic N, graphitized N and oxidized N. As the calcination temperature increases from 900°C to 1000°C and further to 1000°C, the atomic percentage of graphitized N increases from 32.6% to 41.2% and further to 43.8%.

[0091] Experimental Example 2

[0092] This experimental example tests the purification ability of low-zinc-based porous carbon derivatives.

[0093] The effect of calcination temperature (900, 1000 and 1100°C) 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 with reference to the pretreatment method of Example 4, 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 into 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.

[0094] Figure 5 This is a comparison chart of the purification ability test results of QuEChERS purification materials. Figure 5It can be seen that when the calcination temperature is 900℃, C900 can reduce the amount of co-extracted matrix from 61.4mg / g to 37.2mg / g; as the calcination temperature increases from 900℃ to 1000℃, the amount of co-extracted matrix continues to decrease to 32.2mg / g; and as the calcination temperature further increases from 1000℃ to 1100℃, the amount of co-extracted matrix further slightly decreases to 31.1mg / g, indicating that within the test range, when the calcination temperature is 1100℃, the zinc-free QuEChERS purification material exhibits the best purification performance. Combined with the characterization results, it is found that with the increase of calcination temperature, the gradually enhanced purification performance of QuEChERS purification material is positively correlated with the volatilization degree of zinc atoms and the regulation of structure, including the increase of specific surface area and pore volume, the enhancement of carbonization degree, and the regulation of surface element composition and chemical state, especially the increase of graphitized N ratio.

[0095] The purification performance of QuEChERS purification materials was further compared with that of traditional adsorbents such as GCB, C18 and PSA. Figure 5 As shown, the prepared QuEChERS purification material exhibits better purification performance than traditional purification adsorbents, even classic PSA adsorbents.

[0096] In addition, the cobalt-based porous carbon derivative CZIF-67 obtained by calcining ZIF-67 at 900°C for 5h was used as a comparative example to test the purification ability of CZIF-67. The test found that CZIF-67 can only reduce the amount of co-extracted matrix from 61.4mg / g to 48.8mg / g, which is much lower than C900, C1000 and C1100 of the present invention; and CZIF-67 reduces the amount of co-extracted matrix by only 20.5%, which is much lower than the ratio of C1100 to reduce the amount of co-extracted matrix (49.3%; from 61.4mg / g to 31.1mg / g).

[0097] Experimental Example 3

[0098] 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.

[0099] The process of making the working curve of the pesticide to be tested is as follows:

[0100] 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.

[0101] 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).

[0102] The blank tobacco sample (without pesticide residue) was purified by the pretreatment method of Example 4 to obtain a purified blank extract. 0.5 mL of the blank extract was taken, blown to dryness with nitrogen, and then re-dissolved 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 three addition levels (20, 50 and 200 μg / kg) were also investigated. The test results are shown in Table 1.

[0103] Table 1 Retention time (RT), linear correlation coefficient (R), spike recovery (n=6), RSD, detection limit and quantification limit test results of 30 pesticides (C1100 is the purification material)

[0104]

[0105]

[0106] As can be seen from Table 1, the 30 pesticides had a good linear relationship in the range of 2-200 μg / L, and the linear correlation coefficients (R) were all greater than 0.996. The detection limits and quantification limits were 0.01-0.78 μg / kg and 0.02-2.59 μg / kg, respectively.

[0107] The mixed standard working solutions of different mass concentration levels of low, medium and high 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 7 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) were shown in Table 1. The spiked recovery at the three spiked levels was between 85.5% and 119.6%, and the relative standard deviation (RSD, n=6) was less than 11.8%. 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] 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 low zinc-based porous carbon derivative for QuEChERS purification material, characterized in that: The preparation method comprises the following steps: calcining ZIF-8 in an inert atmosphere to obtain a low zinc-based porous carbon derivative, wherein the calcination temperature is 900-1100°C, the calcination time is 5-7h, and the zinc atom proportion on the surface of the low zinc-based porous carbon derivative is not higher than 1.1%.

2. The low zinc-based porous carbon derivative for QuEChERS purification material according to claim 1, characterized in that: The calcination temperature is 1000-1100° C., and the proportion of zinc atoms on the surface of the low-zinc-based porous carbon derivative is no more than 0.15%.

3. The low zinc-based porous carbon derivative for QuEChERS purification material according to claim 1 or 2, characterized in that: The calcination temperature is 1095-1100° C., and the zinc atom ratio on the surface of the low-zinc-based porous carbon derivative is 0.

4. The low zinc-based porous carbon derivative for QuEChERS purification material according to claim 1, characterized in that: The preparation method of ZIF-8 is as follows: zinc salt and 2-methylimidazole are reacted in a solvent, filtered, washed and dried, the molar ratio of zinc ions in the zinc salt to 2-methylimidazole is (0.2-0.25):1, and the reaction time is 6-48 hours.

5. Use of the low zinc-based porous carbon derivative for QuEChERS purification material as claimed in any one of claims 1 to 4 in sample pretreatment for tobacco pesticide residue detection.

6. Use of the low zinc-based porous carbon derivative for QuEChERS purification material as claimed in claim 5 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 low-zinc-based porous carbon derivative and anhydrous magnesium sulfate to the first supernatant, mixing and centrifuging to obtain a second supernatant, and filtering to obtain a sample solution for detection.

7. Use of the low zinc-based porous carbon derivative for QuEChERS purification material as claimed in claim 6 in sample pretreatment for tobacco pesticide residue detection, 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.

8. Use of the low zinc-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 ratio of the volume of the first supernatant, the mass of the zinc-based porous carbon derivative, and the mass of anhydrous magnesium sulfate is (1-2) mL: (10-15) mg: (150-200) mg.

9. Use of the low zinc-based porous carbon derivative for QuEChERS purification material in sample pretreatment for tobacco pesticide residue detection according to claim 6, 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).

10. Use of the low zinc-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 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.

11. Use of the low zinc-based porous carbon derivative for QuEChERS purification material as claimed in any one of claims 1 to 4 in the detection of tobacco pesticide residues.

12. The use of the low zinc-based porous carbon derivative for QuEChERS purification material in tobacco pesticide residue detection according to claim 11, characterized in that: The tobacco sample is treated by the sample pretreatment method according to claims 5 to 10 to obtain a sample solution for detection, and the pesticide residues in the sample solution are analyzed by LC-Q-TOF MS.

13. The use of the low zinc-based porous carbon derivative for QuEChERS purification material in tobacco pesticide residue detection as claimed in claim 12, 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.

14. The use of the low zinc-based porous carbon derivative for QuEChERS purification material in tobacco pesticide residue detection as claimed in claim 12, 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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