A graft-modified magnetic MOF adsorbent, its preparation method and application in cannabinoid detection

Abstract

The present invention discloses a graft-modified magnetic MOF adsorbent, its preparation method and application in cannabinoid detection. The adsorbent uses the amino group of 1-(3-aminopropyl)imidazole to carry out a ring-opening reaction with epoxy, and a large number of imidazole functional groups are modified on the surface of Fe3O4@poly(GMA / DVB) microspheres. Then, through the self-assembly reaction of the aminoimidazole on the microsphere surface with zinc salt ZnCl2 and 2-methylimidazole on the microsphere surface, a magnetic MOF material Fe3O4@poly(GMA / DVB-ZIF-8) with a large number of ZIF-8 crystals on the surface is obtained. Using it as a magnetic solid-phase extraction adsorbent, it is applied to the extraction and purification of four cannabinoids, namely tetrahydrocannabinol, cannabidiol, cannabinol and tetrahydrocannabinolic acid, in urine or saliva, and has excellent selectivity and adsorption performance. Compared with other pretreatment technologies, the magnetic solid-phase extraction method based on the present invention combined with ultra-high performance liquid chromatography-mass spectrometry does not require complex steps such as nitrogen blowing, greatly shortens the pretreatment time, has a high recovery rate and high extraction efficiency, and has strong practicability.

Description

Technical Field

[0001] The present invention belongs to the field of illegal drug detection, and relates to a novel adsorbent, in particular to a graft-modified magnetic MOF adsorbent, a preparation method thereof, and an application in cannabinoid detection. Background Art

[0002] Drug abuse is a major concern in today's society. To effectively prevent drug abuse, it is necessary to accurately trace and crack down on drug crimes to curb the spread of drugs. The biological specimen detection method can accurately determine whether an individual has the behavior of taking drugs, and can obtain a more comprehensive and accurate drug abuse situation, thus helping relevant departments formulate measures to achieve effective prevention and control of drugs. Analyzing the content of drugs and their metabolites in biological samples such as urine and saliva is the most direct means of diagnosing drug abuse. Therefore, it is very necessary to develop an efficient and accurate analysis method to detect drugs and their metabolites in biological samples.

[0003] The main components of cannabinoids include tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), etc. In forensic toxicology identification, common biological specimens mainly include saliva, urine, hair, and blood, etc. At present, the main methods for enriching and extracting cannabinoids in biological matrices are liquid-liquid extraction and column solid-phase extraction. These two methods have the disadvantages of insufficient selectivity, low extraction efficiency, and complex and time-consuming operations. Especially for specimens such as saliva with a small sample volume and low residual drug content, more efficient means are needed for detection and analysis.

[0004] Metal-organic framework materials (MOFs) are porous crystalline materials self-assembled from metal ions or metal ion clusters and organic ligands. As a classic MOF material, zeolitic imidazolate framework-8 (ZIF-8) has a framework structure similar to that of zeolites. Zn metal ions (M) are bridged by 2-methylimidazole (IM) to form an IM-M-IM network. Due to its high stability, good dispersibility, and excellent adsorption ability for various analytes, it has been widely used in the adsorption and separation of various compounds. In addition, the structure of ZIF-8 has abundant imidazole groups and zinc metal ions, which provide rich π-π stacking interactions and electrostatic interaction sites for it. At the same time, ZIF-8 also has strong hydrophobic properties. Aiming at the problems of low recovery rate, low efficiency, and long time consumption in the pretreatment of cannabinoids in urine, as well as the problems faced by existing solid-phase extraction adsorbents in the adsorption, extraction, and detection of cannabinoids in saliva, the present invention introduces the MOF material ZIF-8 by grafting modification to prepare a novel magnetic MOF adsorbent material Fe3O4@poly(GMA / DVB-ZIF-8). Combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS / MS), an isotope internal standard quantitative method for the detection of four cannabinoids is established, which can achieve efficient and rapid quantitative detection of cannabinoids in urine or saliva. Summary of the Invention

[0005] The purpose of the present invention is to provide a graft-modified magnetic MOF adsorbent for the deficiencies of the prior art, which can be used to rapidly extract cannabinoids from urine or saliva. The present invention also provides a preparation method of the graft-modified magnetic MOF adsorbent and its application in the extraction of cannabinoids in urine or saliva.

[0006] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0007] A graft-modified magnetic MOF adsorbent, wherein the adsorbent uses the amino group of 1-(3-aminopropyl)imidazole to carry out a ring-opening reaction with epoxy, modifies the imidazole functional group on the surface of Fe3O4@poly(GMA / DVB) microspheres, and then self-assembles zinc salt and 2-methylimidazole on the surface of the microspheres through the aminoimidazole on the microsphere surface to obtain a magnetic MOF material Fe3O4@poly(GMA / DVB-ZIF-8) with ZIF-8 crystals grafted on the surface.

[0008] Its preparation method includes the following:

[0009] Disperse the Fe3O4@poly(GMA / DVB) microspheres in a mixed solution of acetonitrile and water. After adding 1-(3-aminopropyl)imidazole and ultrasonicating until homogeneous, transfer the solution to a reaction kettle and react at 80 - 100 °C. After the reaction is completed, repeatedly wash the reaction product with ultrapure water and ethanol by means of external magnet adsorption for multiple times to remove unreacted raw materials and impurities. Then, place the obtained reaction product in a three-necked flask equipped with a mechanical stirrer, add a methanol solution, and simultaneously add ZnCl2 and 2-methylimidazole, and stir to react. After the reaction is completed, alternately wash the reaction product with ethanol and deionized water by means of external magnet adsorption for multiple times until the solution above is clear and there are no suspended substances. Take out the reaction product and dry it to obtain the graft-modified magnetic MOF adsorbent Fe3O4@poly(GMA / DVB-ZIF-8).

[0010] In the above technical solution, further, the Fe3O4@poly(GMA / DVB) microspheres are obtained by uniformly mixing the oleic acid-modified Fe3O4 microsphere material OA-Fe3O4, glycidyl methacrylate (GMA), divinylbenzene (DVB), and the pore-forming agent cyclohexane to obtain solution A, dissolving polyvinyl alcohol 1788 and sodium chloride in water and mixing uniformly to obtain solution B, mixing solution A and solution B, ultrasonically pulverizing under ice bath conditions, adding an initiator, and carrying out a condensation reflux reaction under nitrogen protection. Among them, preferably, the dosage ratio of OA-Fe3O4, GMA, DVB, and cyclohexane in solution A can usually be 0.5 g:(1.5 - 2.5) mL:(0.5 - 1.5) mL:(0.5 - 1.5) mL, the mass ratio of polyvinyl alcohol 1788 and sodium chloride in solution B is usually 1:5, and the volume ratio of solution A to solution B is usually (2.5 - 5.5):150; the temperature of the condensation reflux reaction is 70 °C, the stirring rate is 150 r / min, and the reaction duration is 6 - 12 h. The oleic acid-modified Fe3O4 microsphere material OA-Fe3O4 therein can be obtained by dissolving FeCl3·6H2O in ethylene glycol, adding sodium acetate and polyethylene glycol 4000, heating to dissolve, transferring the obtained mixture to a reaction kettle, and heating to react; after the reaction is completed, putting it into oleic acid and heating and stirring to react.

[0011] Further, the mass ratio of the Fe3O4@poly(GMA / DVB) microspheres to 1-(3-aminopropyl)imidazole is 1:(3 - 5).

[0012] Further, the mixed solution is a solution of acetonitrile and water mixed at a volume ratio of 1:1.

[0013] Further, the mass ratio of ZnCl2 to 2-methylimidazole is 0.85:(1.1 - 1.7).

[0014] Application of the graft-modified magnetic MOF adsorbent in cannabinoid detection. First, the adsorbent is used to separate and extract cannabinoids from urine or saliva, and combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS / MS) analysis and isotope internal standard curve method to achieve quantitative analysis of cannabinoids, where the cannabinoids are tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), and tetrahydrocannabinolic acid (THC-COOH).

[0015] Among them, the method for separating and extracting cannabinoids includes the following: For urine or saliva samples, they are first pretreated, then mixed with the activated adsorbent for extraction. After extraction, the adsorbent is vortex-washed with a washing solution, and then the adsorbent is eluted with an eluent. After the elution is completed, the obtained solution is adjusted in pH and filtered, and then used for UHPLC-MS / MS analysis.

[0016] The adsorbent can be activated successively with methanol and ultrapure water;

[0017] The pretreatment of the urine is as follows: The pH value of the urine sample is adjusted to 13 with a sodium hydroxide solution, and it is placed in a water bath for hydrolysis reaction. After the hydrolysis is completed, the volume of 1 mL of the sample is diluted to 4 mL with ultrapure water, and the pH value of the sample is adjusted to 9 - 11 with a hydrochloric acid solution; The corresponding washing solutions are 5% MeOH / H2O, 10% MeOH / H2O, ACN, or MeOH, and the eluent is 0.5%, 1%, 3%, 5%, or 7% NH3·H2O / MeOH.

[0018] The pretreatment of the saliva is as follows: Take 0.5 mL of the saliva sample, dilute it to 4 mL with ultrapure water, and then adjust its pH to 9 - 11 with a sodium hydroxide solution; The corresponding washing solution is 10% MeOH / H2O, and the eluent is 5% NH3·H2O / MeOH.

[0019] The percentage represents the volume concentration of the former component in the latter component before the slash.

[0020] The beneficial effects of the present invention are as follows:

[0021] The graft-modified magnetic MOF adsorbent Fe3O4@poly(GMA / DVB-ZIF-8) provided by the present invention has a simple preparation method, low cost and convenient use. When applied to the detection of cannabinoids in urine or saliva, it can quickly extract four main cannabinoids from urine or saliva: tetrahydrocannabinol, cannabidiol, cannabinol and tetrahydrocannabinolic acid, showing excellent extraction performance. The recovery rates of the four cannabinoids in urine samples under the optimal extraction conditions all exceed 85%, and the recovery rates of the four cannabinoids in saliva samples are all between 89.5% and 106.3%, with high recovery rates. The adsorption process of Fe3O4@poly(GMA / DVB-ZIF-8) for the four cannabinoids is completed through the synergistic action of hydrophobic interaction, π-π stacking interaction, electrostatic interaction and Zn-O chelation. Compared with other pretreatment technologies, the magnetic solid-phase extraction-ultra-high performance liquid chromatography-mass spectrometry (MSPE-UHPLC-MS / MS) method based on Fe3O4@poly(GMA / DVB-ZIF-8) can directly complete sample pretreatment for injection analysis without complex steps such as nitrogen blowing, greatly shortening the pretreatment time. Especially for the detection of cannabinoids in saliva, it can reduce the chance of sample adulteration through a non-invasive, simple and observable sample collection method, and can directly perform magnetic solid-phase extraction without hydrolysis treatment steps, which is more rapid and efficient. Description of the Drawings

[0022] Figure 1 It is the SEM micrograph of the Fe3O4@poly(GMA / DVB-ZIF-8) sample in Example 1.

[0023] Figure 2 It is the EDS diagram of the Fe3O4@poly(GMA / DVB-ZIF-8) sample in Example 1.

[0024] Figure 3 It is the infrared spectrum diagram of the Fe3O4@poly(GMA / DVB-ZIF-8) sample in Example 1.

[0025] Figure 4 It is the nitrogen adsorption isotherm curve of the Fe3O4@poly(GMA / DVB-ZIF-8) sample in Example 1.

[0026] Figure 5 It is the energy spectrum surface scanning analysis diagram of the Fe3O4@poly(GMA / DVB-ZIF-8) sample in Example 1.

[0027] Figure 6 It is the influence of different elution solvents on the extraction recovery rate in the magnetic solid-phase extraction procedure in Example 2.

[0028] Figure 7It is the influence of different ammonia water concentrations as elution solvents on the extraction recovery rate in the magnetic solid-phase extraction procedure in Example 2.

[0029] Figure 8 It is the influence of different washing solvents on the extraction recovery rate in the magnetic solid-phase extraction procedure in Example 2.

[0030] Figure 9 It is the full XPS spectra of the Fe3O4@poly(GMA / DVB-ZIF-8) sample before and after adsorption in Example 5.

[0031] Figure 10 It is the XPS spectra of the Fe3O4@poly(GMA / DVB-ZIF-8) sample in Example 5 before and after adsorbing four cannabinoids. (a) XPS C1s spectra before adsorption, (b) XPS C1s spectra after adsorption, (c) XPS N1s spectra before adsorption, (d) XPS N1s spectra after adsorption, (e) XPS Zn 2p spectra before adsorption, (f) XPS Zn 2p spectra after adsorption.

[0032] Figure 11 It is the influence of different pH values on the extraction recovery rate in the magnetic solid-phase extraction procedure in Example 5.

[0033] Figure 12 It is the influence of different adsorption and extraction times on the extraction recovery rate in the magnetic solid-phase extraction procedure in Example 5.

[0034] Figure 13 It is the influence of different surfactant concentrations on the extraction recovery rate in the magnetic solid-phase extraction procedure in Example 5.

[0035] Table 1 shows the corresponding parameters of the internal standard quantitative method in Example 3.

[0036] Table 2 shows the spiked recovery rates and precision results of the method using urine matrix in Example 3.

[0037] Table 3 shows the measured concentration of THC-COOH in the actual urine samples in Example 4.

[0038] Table 4 is the spiked recovery rate experiment of the actual urine sample 10 in Example 4

[0039] Table 5 shows the comparison of the detected concentrations of THC-COOH in five actual urine samples between the magnetic solid-phase extraction (MSPE) method of the present invention and the standard liquid-liquid extraction (LLE) method in Example 4.

[0040] Table 6 shows the spiked recovery rates and precision results of the method using saliva matrix in Example 6.

[0041] Table 7 shows the spiked recovery rates of the simulated positive saliva samples in Example 6. Detailed implementation mode

[0042] The technical solutions of the present invention will be further specifically described below through specific examples. It should be understood that the implementation of the present invention is not limited to the following examples, and any formal modification and / or change made to the present invention will fall within the protection scope of the present invention.

[0043] Example 1

[0044] 1) Dissolve FeCl3·6H2O in ethylene glycol, add sodium acetate and polyethylene glycol 4000, heat to dissolve, transfer the obtained mixture to a reaction kettle, and heat for reaction; after the reaction is completed, put the obtained Fe3O4 material into oleic acid, heat and stir for reaction, and then wash it repeatedly with water and ethanol several times to obtain OA-Fe3O4;

[0045] 2) Take 0.5 g of OA-Fe3O4, 2 mL of glycidyl methacrylate (GMA), 1 mL of divinylbenzene (DVB) and 1 mL of porogen cyclohexane to prepare a mixed solution A, and ultrasonically mix it evenly. Then take 0.3 g of polyvinyl alcohol 1788 and 1.5 g of sodium chloride and dissolve them in 150 mL of aqueous solution to prepare solution B, and ultrasonically dissolve it. After the B solution is completely mixed, mix the A solution and the B solution, and place them in an ultrasonic cell disruptor, and ultrasonically disrupt them under ice bath conditions (ultrasonic power 200 W). When there is no obvious oil layer on the surface of the solution and it presents a uniform emulsion state, stop ultrasonic treatment. Transfer the ultrasonically treated mixed solution to a three-necked flask equipped with a mechanical stirrer. Before the reaction temperature is raised, introduce nitrogen for 30 min to remove the air in the reaction environment. After removing the air, add 0.08 g of potassium persulfate (K2S2O8) as an initiator to the reaction solution, and then set the reaction temperature to 70 °C for reflux condensation reaction, and the stirring rate is 150 r / min. Nitrogen is continuously introduced during the reaction. After the 8-hour reaction is completed, the obtained product Fe3O4@poly(GMA / DVB) magnetic microspheres are alternately washed multiple times with ethanol and deionized water by means of external magnet adsorption until the solution above is clear and there is no suspended matter. Finally, disperse the washed Fe3O4@poly(GMA / DVB) in ethanol solvent for storage and standby;

[0046] 3) Take 0.5 g of Fe3O4@poly(GMA / DVB) microspheres, disperse them in a mixed solution of acetonitrile and water (V / V, 1:1). Subsequently, add 2.0 g of 1-(3-aminopropyl)imidazole and sonicate it evenly. Then transfer the solution to a reaction kettle and react in an oven for 14 h at a reaction temperature of 90 °C. After the reaction is completed, the reaction product is repeatedly washed with ultrapure water and ethanol by means of external magnet adsorption to remove unreacted raw materials and impurities. The washed material is stored in a mixed solution of ethanol and water for standby;

[0047] 4) Take the reaction product from the previous step and wash it with methanol multiple times to remove water and other organic solvents on the material. Place the washed material in a three-necked flask equipped with a mechanical stirrer, add 60 mL of methanol solution, and simultaneously add 0.85 g of ZnCl2 and 1.5 g of 2-methylimidazole. Stir and react at 40 °C with a stirring rate of 200 r / min for 48 h. After the reaction is completed, the reaction product is alternately washed with ethanol and deionized water by means of external magnet adsorption multiple times until the solution above is clear and there is no suspended matter. Subsequently, the material is placed in a vacuum drying oven at 60 °C and dried for 14 h and then taken out. Finally, the magnetic MOF material Fe3O4@poly(GMA / DVB-ZIF-8) is obtained. Its SEM micrograph is as Figure 1 shown, the EDS diagram is as Figure 2 shown, the infrared spectrum is as Figure 3 shown, the nitrogen adsorption isotherm curve is as Figure 4 shown, and its energy spectrum scanning analysis diagram is as Figure 5 shown.

[0048] Example 2

[0049] 1) Accurately weigh 5 mg of the magnetic solid-phase extraction adsorbent Fe3O4@poly(GMA / DVB-ZIF-8), and sequentially activate and pretreat the adsorbent with 3 mL of methanol and ultrapure water. After thawing the urine sample at room temperature, add sodium hydroxide solution to the thawed urine sample to adjust the pH value of the solution to 13. Then place the solution in a water bath for hydrolysis reaction at a hydrolysis temperature of 60 °C for 20 min. After hydrolysis is completed, take 1 mL of the urine sample and transfer it to a 10 mL glass test tube, then dilute the urine volume to 4 mL with ultrapure water, and adjust the pH value of the sample to 11 with hydrochloric acid solution. After the sample treatment is completed, add 5 mg of the magnetic solid-phase extraction adsorbent Fe3O4@poly(GMA / DVB-ZIF-8) for dispersion extraction. Oscillate and extract the above dispersion solution for about 5 min, and separate the adsorbent from the urine sample through an external magnetic field.

[0050] 2) The magnetic solid-phase extraction adsorbent was vortex-washed with 500 μL of detergent (5% MeOH / H2O, 10% MeOH / H2O, ACN, or MeOH) for 30 s. After washing, the analyte was eluted. 200 μL of eluent (5% NH3·H2O / MeOH, 5% HCOOH / MeOH, or 5% TFA / MeOH, or NH3·H2O / MeOH with different concentrations) was added to a glass test tube and eluted by vortexing for 30 s. After elution, the adsorbent was separated from the solution to both sides of the glass test tube again by an external magnetic field. The elution solution was taken out from the side of the glass tube using a pipette, and 5 μL of formic acid solution was added to the elution solution to adjust the pH. Then, it was filtered using a 0.22 μm pore size aqueous needle filter membrane, and finally, the filtered solution was transferred to a liquid phase injection vial for UHPLC-MS / MS analysis.

[0051] The effects of different detergents and eluents on the extraction recovery were investigated, as Figure 6 , 7 shown in Figure 8. When 10% MeOH / H2O was used as the washing solvent and 5% NH3·H2O / MeOH was used as the elution solvent, the recovery rates of the 4 analytes were the best.

[0052] Example 3

[0053] 1) The isotope internal standard curve method was used for the qualitative and quantitative analysis of four cannabinoids in urine. The relevant validation parameters of the internal standard method are shown in Table 1. The method detection limits (LODs) and quantification limits (LOQs) were determined according to the corresponding concentrations of signal-to-noise ratio S / N = 3 and S / N = 10 to evaluate the sensitivity of the method. The detection limits and quantification limits of the 4 cannabinoids were 0.017 ng / mL and 0.05 ng / mL, respectively. Based on the relationship between the peak area obtained by UHPLC-MS / MS analysis and the analyte concentration, the internal standard standard curves of the four cannabinoids were prepared. The linear ranges of THC, CBD, and CBN were 0.05 - 5 ng / mL, and the linear range of THC-COOH was 0.05 - 25 ng / mL.

[0054] 2) By conducting a spiked recovery experiment on the urine matrix, the accuracy of the method was investigated. Three concentration levels of low, medium, and high within the linear range were selected for the spiked recovery experiment. As shown in Table 2, the spiked recovery rates of THC, CBD, CBN, and THC-COOH in urine were 85.1 - 95.2%, 92.8 - 104.2%, 87.9 - 93.8%, and 84.7 - 104.7% respectively. The intra-day precision and inter-day precision of the urine matrix were less than 5.8% and 7.6% respectively. The above results indicate that the established analytical method has a low detection limit, good accuracy and reproducibility, meeting the requirements of relevant standards. It can meet the detection of four cannabinoids, namely THC, CBN, CBD, and THC-COOH, in urine samples.

[0055] Table 1

[0056]

[0057] Table 2

[0058]

[0059]

[0060] Example 4

[0061] 1) To further evaluate the applicability of the Fe3O4@poly(GMA / DVB-ZIF-8) adsorbent and the effectiveness of the method, Fe3O4@poly(GMA / DVB-ZIF-8) was used as a magnetic solid-phase extraction pretreatment and combined with the established analytical method for detection and analysis in the urine of cannabis users. A total of 18 actual urine samples were detected, and the detection results are shown in Table 3. THC-COOH was detected in all 18 samples, and its concentration range was between 0.104 - 3.170 ng / L, while THC, CBD, and CBN were not detected in all urine samples.

[0062] In subsequent studies, to further verify the accuracy of the method, a spiked recovery experiment was conducted on one of the positive urine samples (Sample 10), as shown in Table 4. It can be seen that the spiked recovery rate of THC-COOH was between 89.1% - 97.8%, indicating that the method has good accuracy. Subsequently, the detection results of the standard liquid-liquid extraction method (LLE) and the magnetic solid-phase extraction method were compared, and the analysis results of five of the samples were selected for comparison. The results are shown in Table 5. There was no significant difference in the results detected by the two methods, and the relative difference was less than 6.0%. The above results show that the established method has good accuracy and practicability and can be applied to the analysis and detection of 4 cannabinoids in urine samples.

[0063] Table 3

[0064]

[0065] Table 4

[0066]

[0067] Table 5

[0068]

[0069] Example 5

[0070] 1) Accurately weigh 5 mg of the magnetic solid-phase extraction adsorbent Fe3O4@poly(GMA / DVB-ZIF-8), and sequentially activate and pretreat the adsorbent with 3 mL of methanol and ultrapure water. Take 0.5 mL of the saliva sample in a 10 mL glass test tube, and dilute the saliva sample to 4 mL with ultrapure water and then adjust the pH value of the solution with sodium hydroxide. Directly add the saliva sample with the adjusted pH to 5 mg of the magnetic solid-phase extraction adsorbent for adsorption extraction, and subsequently vortex wash the magnetic solid-phase extraction adsorbent with 500 μL of a 10% MeOH / H2O washing solution for 30 s.

[0071] 2) After the washing is completed, elute the analyte. Add 100 μL of 5% NH3·H2O / MeOH to the glass test tube and elute by vortexing for 30 s. After the elution is completed, separate the adsorbent and the solution to both sides of the glass test tube again through an external magnetic field, use a pipette to take out the elution solution from the side of the glass tube, and then add 5 μL of formic acid solution to the elution solution to adjust the pH. Then perform filtration treatment with a 0.22 μm pore size aqueous needle filter membrane, and finally transfer the filtered solution to a liquid phase injection vial for UHPLC-MS / MS analysis.

[0072] In this example, the effects of different solution pH values, adsorption extraction times, and surfactant concentrations (referring to adding surfactants before solution extraction) on the extraction recovery rate were investigated, as Figure 11 、 12 and shown in Figure 13. Considering comprehensively, pH = 11, adsorption time of 5 min, and no addition of surfactant are the optimized sample extraction conditions. In the structure of the surfactant (sodium dodecyl sulfate, SDS), the dodecyl group has extremely strong hydrophobic properties, which will destroy the hydrophobic interaction between cannabinoids and the adsorbent. At the same time, the SDS aqueous solution is alkaline, which will inhibit the ionization of the adsorbed imidazole groups, thus affecting the electrostatic interaction between the adsorbent and cannabinoids. Therefore, when the surfactant concentration is 0, the extraction efficiency for the four cannabinoids is the highest. Under the optimal extraction conditions, the XPS full spectra before and after sample adsorption are as Figure 9As shown, the XPS spectra of the sample before and after adsorbing four cannabinoids are as Figure 10 shown.

[0073] Example 6

[0074] 1) The isotope internal standard curve method was used for the qualitative and quantitative analysis of four cannabinoids in saliva. The relevant verification parameters of the internal standard method are shown in Table 6. The method detection limits (LODs) and quantification limits (LOQs) were determined according to the corresponding concentrations at signal-to-noise ratios S / N = 3 and S / N = 10 to evaluate the sensitivity of the method. The detection limits and quantification limits of the four cannabinoids were 0.017 ng / mL and 0.05 ng / mL, respectively. Based on the relationship between the peak areas obtained by UHPLC-MS / MS analysis and the analyte concentrations, internal standard standard curves for the four cannabinoids were prepared. The linear ranges of THC, CBD, and CBN were 0.05 - 5 ng / mL, and the linear range of THC-COOH was 0.05 - 25 ng / mL.

[0075] 2) A spiked recovery experiment was conducted on the saliva matrix to investigate the accuracy of the method. Three concentration levels of low, medium, and high within the linear range were selected for the spiked recovery experiment. As shown in Table 6, the spiked recoveries of THC, CBD, CBN, and THC-COOH in saliva were 87.7 - 92.9%, 96.0 - 106.5%, 92.9 - 104.4%, and 91.7 - 99.3%, respectively. The within-day precision and between-day precision of the saliva matrix were less than 11.4% and 13.8%, respectively. This indicates that the established analytical method has a low detection limit, good accuracy, and reproducibility, meeting the requirements of relevant standards and being able to meet the detection of the four cannabinoids, THC, CBN, CBD, and THC-COOH, in saliva samples.

[0076] 3) Simulated positive samples were prepared by addition, and the content of the added standard was detected and analyzed. Then, a spiked recovery experiment was conducted on the simulated positive samples to investigate the accuracy and applicability of the method. The results are shown in Table 7, and the spiked recoveries of the four cannabinoids were 89.5% - 106.3%. The above results indicate that the established method has good accuracy and practicality and can be applied to the analysis and detection of the four cannabinoids in saliva samples.

[0077] Table 6

[0078]

[0079] Table 7

[0080]

[0081] The above-described embodiments are only a preferred solution of the present invention and do not impose any form of limitation on the present invention. There are other variations and modifications without exceeding the technical solutions described in the claims.

Claims

1. A graft-modified magnetic MOF adsorbent for the detection of cannabinoids in urine or saliva, characterized in that, The adsorbent is prepared by using the amino group of 1-(3-aminopropyl)imidazole to carry out a ring-opening reaction with epoxy, modifying the imidazole functional group on the surface of Fe3O4@poly(GMA / DVB) microspheres, and then carrying out a self-assembly reaction between the aminoimidazole on the microsphere surface and zinc salt and 2-methylimidazole on the microsphere surface to obtain a magnetic MOF material Fe3O4@poly(GMA / DVB-ZIF-8) grafted with ZIF-8 crystals on the surface; the cannabinoids are tetrahydrocannabinol (THC), cannabidiol (CBD), cannabinol (CBN), and tetrahydrocannabinolic acid (THC-COOH); the detection limits and quantification limits of the four cannabinoids are 0.017 ng / mL and 0.05 ng / mL, respectively. The preparation method of the adsorbent includes the following steps: Disperse Fe3O4@poly(GMA / DVB) microspheres in a mixed solution of acetonitrile and water. After adding 1-(3-aminopropyl)imidazole and ultrasonicating evenly, transfer the solution to a reaction kettle and react at 80-100 °C. After the reaction is completed, use an external magnet to adsorb the reaction product and wash it repeatedly with ultrapure water and ethanol to remove unreacted raw materials and impurities; then place the obtained reaction product in a three-necked flask equipped with a mechanical stirrer, add a methanol solution, and simultaneously add ZnCl2 and 2-methylimidazole, and stir and react. After the reaction is completed, use ethanol and deionized water to alternately wash the reaction product by the method of external magnet adsorption for multiple times until the solution above is clear and there are no suspended substances, take out the reaction product and dry it to obtain a grafted and modified magnetic MOF adsorbent Fe3O4@poly(GMA / DVB-ZIF-8). The Fe3O4@poly(GMA / DVB) microspheres are prepared by uniformly mixing oleic acid-modified Fe3O4 microsphere material OA-Fe3O4, glycidyl methacrylate (GMA), divinylbenzene (DVB), and a pore-forming agent cyclohexane to obtain solution A, dissolving polyvinyl alcohol 1788 and sodium chloride in water and mixing evenly to obtain solution B, mixing solution A and solution B, ultrasonically pulverizing under an ice bath condition, adding an initiator, and carrying out a condensation reflux reaction under nitrogen protection.

2. The preparation method of the graft-modified magnetic MOF adsorbent for cannabinoid detection in urine or saliva according to claim 1, characterized in that, It includes the following steps: Disperse Fe3O4@poly(GMA / DVB) microspheres in a mixed solution of acetonitrile and water. After adding 1-(3-aminopropyl)imidazole and ultrasonicating evenly, transfer the solution to a reaction kettle and react at 80-100 °C. After the reaction is completed, use an external magnet to adsorb the reaction product and wash it repeatedly with ultrapure water and ethanol to remove unreacted raw materials and impurities; then place the obtained reaction product in a three-necked flask equipped with a mechanical stirrer, add a methanol solution, and simultaneously add ZnCl2 and 2-methylimidazole, and stir and react. After the reaction is completed, use ethanol and deionized water to alternately wash the reaction product by the method of external magnet adsorption for multiple times until the solution above is clear and there are no suspended substances, take out the reaction product and dry it to obtain a grafted and modified magnetic MOF adsorbent Fe3O4@poly(GMA / DVB-ZIF-8).

3. The preparation method of the graft-modified magnetic MOF adsorbent for cannabinoid detection in urine or saliva according to claim 2, characterized in that, The Fe3O4@poly(GMA / DVB) microspheres are prepared by uniformly mixing the oleic acid-modified Fe3O4 microsphere material OA-Fe3O4, glycidyl methacrylate (GMA), divinylbenzene (DVB), and the porogen cyclohexane to obtain solution A, dissolving polyvinyl alcohol 1788 and sodium chloride in water and mixing them uniformly to obtain solution B, mixing solution A and solution B, ultrasonically pulverizing under ice bath conditions, adding an initiator, and carrying out a condensation reflux reaction under nitrogen protection.

4. The preparation method of the graft-modified magnetic MOF adsorbent for cannabinoid detection in urine or saliva according to claim 2, characterized in that, The mass ratio of the Fe3O4@poly(GMA / DVB) microspheres to 1-(3-aminopropyl)imidazole is 1:(3 - 5).

5. The preparation method of the graft-modified magnetic MOF adsorbent for cannabinoid detection in urine or saliva according to claim 2, wherein The mixed solution is a solution prepared by mixing acetonitrile and water at a volume ratio of 1:

1.

6. The preparation method of the graft-modified magnetic MOF adsorbent for cannabinoid detection in urine or saliva according to claim 2, characterized in that, The mass ratio of the ZnCl2 and 2-methylimidazole 0.85:（1.1-1.7）。 7. Use of the graft-modified magnetic MOF adsorbent according to claim 1 in cannabinoid detection, characterized in that, First, the adsorbent is used to separate and extract cannabinoids in urine or saliva, and combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS / MS) analysis and isotope internal standard curve method to achieve the quantitative analysis of cannabinoids.

8. The application according to claim 7, characterized in that, The method for separating and extracting cannabinoids includes the following steps: for urine or saliva samples, first perform pretreatment, then mix with the activated adsorbent for extraction, after extraction, use the washing solution to vortex wash the adsorbent, and then use the eluent to elute the adsorbent. After the elution is completed, adjust the pH of the obtained solution and filter it for UHPLC-MS / MS analysis.

9. The application according to claim 8, wherein The pretreatment of the urine is as follows: adjust the pH value of the urine sample to 13 with sodium hydroxide solution, place it in a water bath for hydrolysis reaction. After the hydrolysis is completed, dilute the 1 mL sample volume to 4 mL with ultrapure water and adjust the pH value of the sample to 9 - 11 with hydrochloric acid solution; the corresponding washing solution is 5% MeOH / H2O, 10% MeOH / H2O, ACN, or MeOH, and the eluent is 0.5%, 1%, 3%, 5%, or 7% NH3·H2O / MeOH.

10. The application according to claim 8, characterized in that, The pretreatment of the saliva is as follows: take 0.5 mL of the saliva sample, dilute it to 4 mL with ultrapure water, and then adjust its pH to 9 - 11 with sodium hydroxide solution; the corresponding washing solution is 10% MeOH / H2O, and the eluent is 5% NH3·H2O / MeOH.

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