Method for detecting organophosphorus residues in medicinal and edible products based on paper spray mass spectrometry

Abstract

The invention discloses a method for detecting organophosphorus residues in a medicinal and edible product based on a paper spray mass spectrometry technology, and belongs to the technical field of paper adsorption mass spectrometry detection. The method specifically comprises the following steps: weighing a to-be-detected sample, dispersing the to-be-detected sample in an acetic acid aqueous solution, carrying out ultrasonic treatment, adding dichloromethane, oscillating, centrifuging, and recovering an organic layer to obtain a to-be-detected solution; the method comprises the following steps: preparing a COF-300-paper paper base, adding the COF-300-paper paper base into a solution to be detected, extracting, airing after extraction, dropwise adding a spray solvent ethanol onto the COF-300-paper paper base, detecting by adopting a QTRAP 4500 mass spectrum system, and calculating the content of OPPs in a sample to be detected according to a detection result and a standard curve. The method has good sensitivity, accuracy and repeatability, has the advantages of high efficiency, rapidness and low solvent consumption, meets the environmental protection requirement while improving the food safety monitoring efficiency, and has important popularization value.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for detecting organic phosphorus residues in medicinal and edible products based on paper spray mass spectrometry, belonging to the field of paper adsorption mass spectrometry. BACKGROUND

[0002] The problem of organic phosphorus pesticide residues in medicinal and edible substances and corresponding products has attracted widespread attention in recent years. Organic phosphorus pesticides are known for their strong neurotoxicity, and accumulation in food can lead to a series of health problems, including acute poisoning and long-term chronic diseases, so it is particularly important to ensure food safety.

[0003] Currently, the mainstream methods for detecting organic phosphorus residues mainly include gas chromatography (GC), gas chromatography mass spectrometry (GC-MS / MS), liquid chromatography (LC), and liquid chromatography mass spectrometry (LC-MS / MS). These techniques perform well in terms of sensitivity, accuracy, and quantitative analysis capabilities, and can effectively identify and quantify multiple organic phosphorus pesticide components. However, despite the significant advantages of these chromatography and mass spectrometry methods in detection applications, there are still some limitations in actual operation: first, the operation process of these methods is usually complex, requiring professional personnel to perform delicate sample pretreatment and instrument debugging, which not only increases the operation difficulty, but also puts forward higher requirements for the skill level of laboratory personnel. Secondly, during the sample pretreatment process, a large amount of chemical solvent is often required, which not only increases the detection cost, but also may cause environmental burden. In addition, the detection period is relatively long, often leading to the inability to quickly feedback the detection results, thereby affecting the timely monitoring and risk assessment of food safety.

[0004] In view of the challenges faced by current detection methods, it is particularly important to develop a rapid, simple and low-pollution detection technology. This technology should not only simplify the operation process, but also minimize the impact on the environment, while providing rapid and accurate detection results. In addition, the cost factor is also crucial. An ideal food safety detection technology needs to consider rapidity, simplicity, low pollution, high performance and low cost (including reagents, instruments, consumables and labor cost), making it economically feasible and easy to promote. Such technological progress will significantly improve the efficiency of food safety monitoring, providing consumers with more timely and reliable information protection, and has important practical significance and wide application value. SUMMARY

[0005] In response to the defects and shortcomings of the existing technology, the purpose of the present invention is to provide a method for detecting organophosphorus residues in edible and medicinal products based on paper spray mass spectrometry technology. The core of this method is to utilize the excellent adsorption properties of covalent organic framework (COFs) materials to effectively capture organophosphorus residues in edible and medicinal substances and products. The sample only needs to be sprayed on COFs paper and, after simple pretreatment, it can be placed in a mass spectrometer for analysis. Compared with traditional detection methods, this method not only achieves rapid and efficient detection, eliminates the pretreatment and purification process, significantly reduces the amount of reagents used, but also effectively reduces the generation of chemical waste. This technical solution can better address food safety challenges and provide consumers with more reliable protection.

[0006] In order to achieve the above objectives, the technical solutions provided are as follows:

[0007] The present invention provides a method for detecting organophosphorus residues in medicinal and edible products based on paper spray mass spectrometry technology, the method comprising the following steps:

[0008] (1) Sample pretreatment

[0009] Weigh the sample to be tested and disperse it in an acetic acid aqueous solution. After ultrasonication, add dichloromethane, shake, centrifuge, and recover the organic layer to obtain the test solution.

[0010] (2) Determination of organic phosphorus content in the sample to be tested

[0011] The COF-300@paper paper base is placed in the test solution of step (1) for extraction, dried after extraction, and the solvent ethanol is sprayed onto the COF-300@paper paper base. Then, a mass spectrometry system is used for detection. The content of OPPs in the test sample is calculated based on the test results and the standard curve.

[0012] In one embodiment, the organophosphorus comprises one or more of fenthion, phosalone, dimethoate, phosmet, and acephate.

[0013] In one embodiment, the medicine and food product includes one or more of hawthorn, ginseng and coix seed tea, red ginseng rose vitality tea, red ginseng rose dandelion tea, wolfberry, and ginseng.

[0014] In one embodiment, the volume fraction of the acetic acid aqueous solution in step (1) is 1 to 5%.

[0015] In one embodiment, the mass volume ratio of the sample to be tested, the acetic acid aqueous solution and the dichloromethane in step (1) is 1:20-30:10-20; g:mL:mL.

[0016] In an embodiment, the centrifugal parameter in step (1) is 5000-8000 rpm for 5-10 min.

[0017] In an embodiment, the COF-300@paper paper base in step (2) is specifically prepared by mixing COF-300 powder with ultrapure water, ultrasonicating to obtain a uniformly dispersed suspension, transferring to a Buchner funnel containing filter paper, and performing suction filtration under vacuum conditions, and then placing the COF-300-loaded filter paper matrix in a room temperature environment for natural drying to obtain the COF-300@paper; and then cutting the COF-300@paper into an isosceles triangle to obtain the isosceles triangular COF-300@paper.

[0018] In an embodiment, the amount of COF-300 loaded on the COF-300@paper paper base per 3.5 cm diameter filter paper is 2.5-12.5 mg; preferably, the amount of COF-300 loaded on the COF-300@paper paper base per 3.5 cm diameter filter paper is 5 mg.

[0019] In an embodiment, the COF-300@paper paper base in step (2) is an isosceles triangle with a height of 10-15 cm and a tip angle of 10-60 °C, preferably 30 °C.

[0020] In an embodiment, the COF-300 powder is prepared by using p-xylylene diamine (BDA) and tetra(4-aminophenyl)methane (TAM) as monomers, and allowing the mixture to stand at a temperature of 40-45 °C for 36-48 h.

[0021] In an embodiment, the COF-300 powder is specifically prepared by the following method:

[0022] (1) Mixing BDA, 1,4-dioxane and CF3CH2NH2, vortexing, and then adding CF3COOH to obtain reaction solution A;

[0023] (2) Dissolving TAM in 1,4-dioxane to obtain reaction solution B;

[0024] (3) Adding reaction solution B to reaction solution A, filtering, allowing the mixture to stand at a temperature of 40-45 °C for 36-48 h, and after the reaction is completed, extracting the synthesized crystals by Soxhlet extraction in 1,4-dioxane and tetrahydrofuran, respectively, and drying to obtain yellow crystals, i.e., COF-300.

[0025] In an embodiment, the mass ratio of BDA to TAM is 10-15:20.

[0026] In an embodiment, the parameters of the mass spectrometry system in step (2) are as follows: QTRAP 4500 mass spectrometry system, and the mass spectrometry parameters of the QTRAP 4500 are as follows: curtain gas: 10 psi; ion source gas 1: 0 Psi; ion source gas 2: 0 Psi; spray voltage: 3400 V; IHT (Ion Guide Heater Temperature): 150 DEG C; collision gas: nitrogen; entrance voltage: 10 v; exit voltage: 10 v; MRM (multiple reaction monitoring) positive ion mode scanning, scanning rate: 10 Da / s; and paper base angle: 30 DEG.

[0027] The application also provides application of the method described above in food safety monitoring.

[0028] Advantages:

[0029] The method for detecting organic phosphorus residues in products with medicinal and edible values based on paper spray mass spectrometry has the following advantages:

[0030] (1) high selectivity and adsorption capacity: the excellent adsorption performance of the COFs paper significantly improves the sensitivity and accuracy of detection;

[0031] (2) simple and rapid operation process: the paper spray mass spectrometry method is simple to operate, does not require a complex sample pretreatment and purification process, and can effectively shorten the detection time;

[0032] (3) environmentally friendly and low cost: the method uses a small amount of solvent during detection, thereby minimizing environmental pollution, and can be reused 5 times.

[0033] (4) high efficiency: can be used for simultaneous real-time detection of multiple organic phosphorus pesticides, and is suitable for rapid qualitative and quantitative analysis on site;

[0034] The method can detect organic phosphorus in a variety of medicinal and edible substances and products in a short time, and the results show that the method has good sensitivity, accuracy and repeatability, further verifying its potential for wide application in food safety monitoring, improving the efficiency of food safety monitoring, meeting environmental protection requirements, and having important popularization value;

[0035] In addition, the method has low detection limit and quantitative limit, and has the advantages of high efficiency, speed and small amount of solvent used; specifically, for five kinds of organic phosphorus pesticides (OPPs), the COF-300 material can reach about 90% of the equilibrium adsorption amount in about 5 minutes. The method also has the characteristics of simple operation and low matrix effect, and is suitable for analysis of OPPs residues in complex food matrix samples, thereby providing effective protection for food safety. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Synthetic scheme of COF-300 material prepared for Example 1;

[0037] Figure 2 XRD pattern of COF-300 material prepared for Example 1;

[0038] Figure 3 PT-IR pattern of COF-300 material prepared for Example 1;

[0039] Figure 4 Nitrogen adsorption-desorption isotherm of COF-300 material prepared for Example 1; (a) N2adsorption-desorption isotherm of single crystal COF-300; (b) BET specific surface area of single crystal COF-300; (c) pore size distribution of single crystal COF-300;

[0040] Figure 5 Schematic diagram of molecular diameters of 5 OPPs;

[0041] Figure 6 Stability effect diagram of COF-300 material prepared for Example 1 in different solvents;

[0042] Figure 7 Adsorption kinetics model diagram of COF-300 material prepared for Example 1; (a) pseudo-first-order kinetic model; (b) pseudo-second-order kinetic model; (c) relationship between OPPs adsorption amount and time;

[0043] Figure 8 Flowchart of COF-300@paper paper base prepared for Example 2;

[0044] Figure 9 Scanning electron micrograph of COF-300@paper paper base prepared for Example 2; (a) filter paper; (b) COF-300@paper (100 μm) at different magnifications; (c) COF-300@paper (50 μm) at different magnifications; (d) COF-300@paper after 5 times of PSI;

[0045] Figure 10 XPS spectra of COF-300@paper paper base prepared for Example 2 before and after adsorbing OPPs; (a) XPS high-resolution C1s spectra of COF-300 before and after adsorbing 5 kinds of OPPs; (b) XPS high-resolution P 2p spectra of COF-300 before and after adsorbing 5 kinds of OPPs; (c) XPS high-resolution S2p spectra of COF-300 before and after adsorbing 5 kinds of OPPs;

[0046] Figure 11 Flowchart of detection method for Example 3;

[0047] Figure 12 Standard curve of OPPs in Example 5; (a) the standard curve equation and correlation coefficient of fenthion in the range of 0.5-200 μg·L -1 -1 -1 -1 -1

[0048] Figure 13 Stability and repeatability effect diagram of COF-300@paper paper-based prepared in Example 2; (a) stability effect diagram after storing for different days; (b) repeatability effect diagram;

[0049] Figure 14 Data diagram of different parameter optimization; (a) different COF-300 loadings; (b) different spray voltages; (c) different spray solvents; (d) different tip angles. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application. The following specific embodiments further describe the present application.

[0051] The test method involved in the present application is as follows:

[0052] 1. PXRD: COF-300 samples were uniformly filled into wafer grooves using glass sheets, and X-ray diffraction analysis was performed using a Cu-Kα radiation source. The instrument parameters were set as follows: scanning step 0.05°, dwell time 0.5 seconds per step, and scanning angle range 2-40°. The diffraction data were obtained with the 2θ angle as the abscissa and the diffraction intensity as the ordinate, and finally the data were processed and the spectrum was plotted by Origin software.

[0053] ​​​​​2、FT-IR: Fourier transform infrared spectroscopy was used to determine the infrared characteristic map of benzene-dicarboxaldehyde (BDA), tetra(4-aminophenyl)methane (TAM), synthesized COF-300 and COF-300 after saturated adsorption of OPPs. The test temperature was set to 25℃, the resolution was 0.5cm -1 , and the wave number range was 4000-500cm -1 . The results were plotted with the wave number as the abscissa and the transmittance as the ordinate using origin software.

[0054] 3、SEM: Scanning electron microscopy was used to characterize the morphology of blank filter paper, COF-300@paper and COF-300@paper after 5 times of spray ionization treatment, and the results were observed under different magnifications.

[0055] 4、N2 adsorption-desorption experiment: Gas adsorption instrument was used to determine the specific surface area and pore size distribution of the synthesized COF-300.

[0056] 5、XPS: X-ray photoelectron spectroscopy was used to determine the full spectrum and high-resolution C1s, P 2p, S2p spectrum of COF-300 before and after adsorbing 5 kinds of OPPs. The binding type and element composition of the material were verified.

[0057] Example 1

[0058] The preparation method of single crystal COF-300 material includes the following steps:

[0059] (1) In a 5.0 mL sample bottle, benzene-dicarboxaldehyde BDA (12 mg, 0.089 mmol), 1,4-dioxane (0.50 mL) and CF3CH2NH2 (70 μL, 10 mol / L) were added in sequence, after vortex, 0.10 mL CF3COOH (6.0 mol / L) was added to obtain reaction solution A;

[0060] (2) Tetra(4-aminophenyl)methane TAM (20 mg, 0.052 mmol) was dissolved in 1,4-dioxane (0.50 mL) to obtain reaction solution B;

[0061] (3) Reaction solution B was added to reaction solution A, filtered through a 0.20 μm nylon-6 membrane, and placed at a temperature of 40℃ for 48h. After the reaction was completed, the synthesized crystals were extracted by Soxhlet extraction method in 1,4-dioxane and tetrahydrofuran for 1 day respectively, and dried at 120℃ under vacuum for 12h to obtain yellow crystals, i.e. COF-300 (synthesis schematic diagram as shown in Figure 1 ), with a yield of 65%.

[0062] Characterization of COF-300 material:

[0063] 1. The crystal structure of the prepared COF-300 was analyzed by PXRD.

[0064] The results are as follows Figure 2 As shown, the main peak of COF-300 is in the low-angle region (2θ=8.8°), showing a sharp diffraction peak, which corresponds to the (100) crystal plane and reflects the unit cell parameter aa8. According to the Bragg equation (Equations 1 and 2).

[0065] nλ=2d(hkl)sinθ (1)

[0066]

[0067] Where n is the number of diffraction events, λ is the wavelength of the incident X-ray, d(hkl) is the spacing between the (hkl) planes in the crystal, θ is the angle between the incident X-ray and the reflected plane, a is the lattice constant, and h, k, and l are the crystal plane indices, respectively.

[0068] The second peak (12.5°-12.8°) corresponds to the (110) crystal plane. The Bragg equation can be used to deduce that θ(110)≈12.6° (assuming a is determined by the main peak at 8.8°). The third peak (17.8°-18.0°) corresponds to the (200) crystal plane, and θ(200)≈17.8° is calculated. The specific angle may fluctuate slightly due to differences in unit cell parameters, indicating its highly ordered periodic framework structure. The characteristic diffraction peaks with lower intensity are at 20.8° and 24.3°, which is consistent with the literature reports, proving that COF-300 is a crystalline polymer.

[0069] 2. Characterization of the crystal structure of the prepared COF-300 by FT-IR spectroscopy

[0070] result Figure 3 As shown in the FT-IR spectrum, by comparing the spectra of BDA, TAM and COF-300, it is found that in the COF-300 spectrum, 1685 cm -1 and 3395cm -1 The characteristic peak at 1620 cm-1 was significantly weakened, and the peak at 1620 cm-1 appeared. -1 The new peak at 1685cm indicates that C=O in BDA -1 ) key and TAM(3395cm -1 ) undergoes an amine-aldehyde condensation reaction to form C=N (1620 cm -1 ) new bonds. This, to some extent, confirms the successful synthesis of COF-300. Furthermore, the FT-IR spectra of COF-300 remained almost unchanged after saturated adsorption of various OPPs, demonstrating that OPPs have little effect on the imine bonds of COF-300.

[0071] 3. Characterization by nitrogen adsorption instrument

[0072] The specific surface area and pore size distribution of COF-300 were analyzed by N2 adsorption-desorption experiments at 77K. Figure 4 As shown, from Figure 4 As can be seen from (a) and (c), COF-300 absorbs N2 sharply when the relative pressure is below 0.2, and the pore size distribution is narrow around 1.9 nm, which confirms that COF-300 has a microporous structure. Its specific surface area (BET) is 175.496 m 2 ·g -1 The pore size is 1.98nm. The results show that the synthesized COF-300 material has the characteristics of large surface area and high porosity.

[0073] The molecular diameters of OPPs (fenthion, phosalone, dimethoate, phosmet, and acephate) simulated and measured by ChemDraw 3D software ( Figure 5 ) are 1.1nm, 1.4nm, 1.0nm, 1.3nm and 0.6nm, respectively, which are all smaller than the pore size of COF-300. Therefore, pore size selection can occur, providing conditions for the subsequent use of COF-300 materials for OPPs detection.

[0074] 4. Chemical stability test

[0075] A 25mg COF-300 sample was weighed and placed in a 2mL centrifuge tube. 1mL of each solvent (THF, H2O, EtOH, iPrOH, and n-Hex) was added. After standing in the dark for 24 hours, the sample was centrifuged at 8000 rpm for 5 minutes to separate the solid and liquid phases. The supernatant was discarded, and the precipitate was then placed in a 60°C vacuum oven for 12 hours (the centrifuge tube was sealed with pinhole foil). The dried solid was then analyzed for crystal structure integrity using PXRD, using standard PXRD analysis procedures.

[0076] The results are as follows Figure 6 As shown, crystalline COF-300 can still maintain its original crystal form in THF, H2O, EtOH, iPrOH, and n-Hex solvents, indicating that crystalline COF-300 has certain chemical stability in the above solvents and can be used as COF-300@paper adsorption material.

[0077] 5. Adsorption kinetics evaluation

[0078] The adsorption process of COF-300 on the five OPPs was evaluated by the adsorption kinetics model, including the pseudo-first-order kinetic model and the pseudo-second-order kinetic model, the first-order kinetic model (formula 3) and the pseudo-second-order kinetic model (formula 4); the model formula is as follows:

[0079] ln(q e -q t )=ln q e -k1t (3)

[0080]

[0081] Wherein, qeand qtare the adsorption amounts of the target objects at equilibrium and at a certain time t (μg·g -1 ), respectively, k1and k2are the rate constants of the pseudo-first-order and pseudo-second-order kinetic models, respectively; the parameters are shown in Table 1:

[0082] Table 1 Kinetic parameters of COF-300 adsorbing five OPPs

[0083]

[0084] The results are shown in Figure 7 When the initial concentration is 200 μg·L -1 , the adsorption process of COF-300 on the OPPs is more consistent with the pseudo-second-order kinetic model (R2 2 >R1 2 ). COF-300 shows the characteristics of rapid adsorption in a short time on the five OPPs, and about 90% of the equilibrium adsorption amount of the OPPs is reached within 5 minutes.

[0085] The maximum adsorption capacity of COF-300 on fenthion, phosalone, dimethoate, phosmet and acephate is 132.45 μg·g -1 , 139.66 μg·g -1 , 632.91 μg·g -1 , 127.06 μg·g -1 , 301.20 μg·g -1 , respectively. This may be due to the fact that the five OPPs have different chemical structures and the strength of the interaction between them and COF-300 is different, resulting in different maximum adsorption capacities.

[0086] Example 2

[0087] Preparation of COF-300@paper (the flowchart is shown in Figure 8 , which includes the following:

[0088] COF-300 powder prepared in Example 1 5 mg was mixed with 25 mL ultrapure water, ultrasonic, to obtain a uniformly dispersed suspension, which was transferred to a Buchner funnel with filter paper with a diameter of 3.5 cm, and vacuum filtration was carried out under vacuum conditions, and finally the COF-300 loaded filter paper matrix was placed in a room temperature environment and naturally dried to obtain COF-300@paper, which was ready for use.

[0089] Characterization of COF-300@paper

[0090] 1. Characterization by SEM

[0091] The morphology of blank filter paper, COF-300@paper and COF-300@paper after 5 times of use was characterized, and the results are shown in Figure 9 From SEM Figure 9 (a), it can be seen that the blank filter paper is mainly rich in internal fiber structure, and the gap distance is large. From Figure 9 (b) and (c), it can be seen that the crystal morphology of COF-300 is shuttle-shaped, and the particle size is uniformly loaded on the blank filter paper to form COF-300@paper. From Figure 9 (d), it can be seen that after 5 times of spray ionization (PSI) use, there are still many COF-300 crystals attached to the filter paper fibers, which can reflect that COF-300@paper has a certain repeated use.

[0092] 2. Characterization by XPS

[0093] XPS analysis was performed on COF-300@paper before and after adsorbing OPPs, and the results are shown in Figure 10 Compared with before adsorption, the high-resolution C1s characteristic peak of COF-300 after adsorbing 5 kinds of OPPs moved by-0.09-0.03 eV Figure 10 (a)), the high-resolution P 2p characteristic peak moved by 3.99-14.32 eV Figure 10 (b)), and the high-resolution S2p characteristic peak moved by-1.09-1.11 eV Figure 10 (c)), which proves that there is interaction between OPPs and COF-300.

[0094] Example 3

[0095] A method for detecting OPPs based on COF-300@paper (the detection process is shown in Figure 11 ), which comprises the following steps:

[0096] (1) Sample treatment: bulk hawthorn dry sample was crushed, 1 g sample was dispersed in 20 mL volume fraction of 1% acetic acid aqueous solution, 10 mL dichloromethane was added after ultrasonic for 30 min, shaker oscillation for 5 min, ultrasonic for 2 min, high speed centrifugation for 5 min at 8000 rpm, the organic layer was recovered, and the test solution was obtained;

[0097] (2) Standard curve construction

[0098] The COF-300@paper prepared in Example 2 was cut into an isosceles triangle with a height of 12 mm, and was placed in a series of different concentration (0.5-200 μg·L -1 ) OPPs mixed standard sample matrix solution for extraction, and was naturally dried for 5 min, then was washed with 1 mL of ultrapure water, and was taken out and dried after 10 s. QTRAP 4500 mass spectrometry system was used for detection, the top end of the paper was controlled to be 5 mm away from the inlet of the mass spectrometer horizontally and 4 mm vertically, and 20 μL of spray solvent ethanol was added to elute the OPPs in the COF-300 channels on the surface of the paper matrix;

[0099] During the detection process, the PSI device was installed on a commercial Nanospray Flex source (SCIEX, USA), and the mass spectrometry parameters of QTRAP4500 were optimized as follows: gas curtain gas: 10 psi; ion source gas 1: 0 Psi; ion source gas 2: 0 Psi; spray voltage 3400 V; IHT (Ion Guide Heater Temperature): 150℃; collision gas: nitrogen; inlet voltage: 10 v; outlet voltage: 10 v; multiple reaction monitoring (MRM) positive ion mode scanning, scanning rate 10 Da / s; paper base angle 30°.

[0100] The multiple reaction monitoring (MRM) positive ion mode scanning mode was used, and the ion pairs, declustering voltage (DP) and collision energy (CE) of the five target OPPs are shown in Table 2. The standard curve results of the concentrations (x, μg·L -1 ) and intensities (y) of the five target OPPs are shown in Figure 12 and Table 3: the correction curves (R 2 ≥ 0.99) of the five OPPs obtained, indicating that the OPPs have good linear relationship in the concentration range; the detection limits (LODs) are 0.5-1 μg·L -1 , and the quantification limits (LOQs) are 1-10 μg·L -1 ; the relative standard deviations (RSDs) of the OPPs solution in the intra-day (n=5) are between 3.1% and 9.4%, and the RSDs in the inter-day (n=5) are between 4.6% and 9.9%.

[0101] Table 2 Ion pairs, declustering voltage (DP), and collision energy (CE) of five target OPPs

[0102]

[0103] Table 3. Linear relationship of OPPs within the concentration range

[0104]

[0105] (3) Determination of OPPs content in the sample

[0106] An isosceles triangle COF-300@paper with a height of 12 mm was placed in the test solution of step (1) for extraction, and then naturally dried for 5 minutes. Then, it was washed with 1 mL of ultrapure water, taken out and dried after 10 seconds, and detected using a QTRAP 4500 mass spectrometry system. The top of the paper was controlled to be 5 mm horizontally and 4 mm vertically from the inlet of the mass spectrometer. 20 μL of spray solvent ethanol was added to elute the OPPs adsorbed in the COF-300 pores on the upper surface of the paper matrix; the content of OPPs in the test sample was calculated based on the test results and the standard curve.

[0107] Example 4 Recovery and LOD, LOQ, RSD

[0108] 0.2 μg g -1 , 0.5 μg g -1 and 1.0μg g -1 The recovery rate of the standard mixed solution of OPPs was determined, and the results are shown in Table 3:

[0109] Table 4 Content and recovery of five OPPs in six actual samples

[0110]

[0111]

[0112] The established COF-300@paper--MS method was used to analyze the commercially available medicinal and edible samples at 0.2, 0.5, and 1.0 μg g -1 The recovery experiments of five OPPs at three concentrations were conducted. The experimental data in Table 4 show that the recovery rates of this method ranged from 70.2% to 109.4%, indicating that this method has good accuracy. The RSDs of the five repeated experiments were all less than 11.0%, indicating that this method has high precision and good repeatability, and can be used for OPPs residue analysis of medicinal and edible substances and products. In addition, in the red ginseng rose dandelion tea (quality control) sample, the three concentrations of dimethoate at 0.2, 0.5, and 1.0 μg g-1 The recoveries were 80.0%, 94.0% and 104.5%, respectively, and the RSDs were all less than 8.6%.

[0113] Example 5 Stability and Repeatability

[0114] In order to further investigate the stability of single-crystal COF-300 particles loaded on paper, the COF-300@paper prepared in Example 2 was stored for 1, 5, 10, 15, and 20 days, and the MRM positive ion mode response value of OPPs was detected. The results are as follows: Figure 13 As shown;

[0115] from Figure 13 (a) It can be seen that COF-300@paper is heated to 1000 μg·L -1 Paper spray ionization analysis was performed in a mixed solution of five OPPs, and it was detected that COF-300@paper had good stability after being stored for different days, and the RSDs of the five OPPs measured were all around 2.6%.

[0116] The same COF-300@paper in OPPs solution is 1000 μg·L -1 The results of paper spray ionization analysis of 6 adsorption-desorption cycles were as follows: Figure 13 As shown in (b); after repeated use (≥5 cycles), the RSD was 8.1%, and the performance of the COF-300@pape material decreased, indicating that the synthesized COF-300@paper has good stability and reusability, and can be stored for a long time.

[0117] Example 6 Parameter Optimization

[0118] 1mg·L -1 The OPPs standard mixed solution was used as the detection object, and the detection was carried out according to the method of Example 3; the details are as follows:

[0119] 1. Effect of COF-300 loading on OPPs signal intensity

[0120] Different masses of COF-300 material (0, 2.5, 5, 7.5, 10, and 12.5 mg) were added to a beaker and dissolved in 25 mL of ultrapure water, respectively. The mixture was ultrasonically treated for 30 minutes to uniformly disperse the mixture in the aqueous solution. Subsequently, the solution was poured into a funnel containing 3.5 cm diameter filter paper and filtered to obtain the paper matrix COF-300@paper. The prepared paper matrix (COF-300@paper) was naturally dried and used for online detection by paper spray mass spectrometry. The optimal COF-300 dosage was determined based on the signal intensity of COF-300@paper in the multiple reaction monitoring (MRM) mode for OPPs.

[0121] Results are shown in Table 1 Figure 14 (a) It was observed that with the increase of COF-300 loading, the PSI (Paper Spray Ionization) signal first increased and then decreased. When the COF-300 loading was 5 mg, the recovery rate of the five OPPs was the highest. This was because the crystal COF-300 particles could be attached to the fiber paper base with large voids, and with the increase of COF-300 particles, the 3D through-pore significantly improved the mass transfer efficiency; and the active sites (C=N) on the surface of COF-300 and the force of the target OPPs increased, which improved the recovery rate of OPPs; but with the further increase of COF-300 loading, the excess COF-300 crystal particle material could not be firmly attached to the filter paper, and part of the crystal particle material fell off, resulting in a decrease in elution efficiency and spray efficiency, a decrease in MRM response value of PSI, and a decrease in recovery rate of OPPs.

[0122] 2. Effect of spray voltage on the signal intensity of OPPs

[0123] Six groups of voltages (2500, 2800, 3100, 3400, 3700, 4000 V) in the range of 2500-4000 V were tested on the COF-300@paper paper substrate prepared in Example 2, and the optimal spray voltage condition was finally determined by analyzing the signal response intensity of the COF-300@paper modified material to the organic phosphorus pesticide (OPPs) multi-response monitoring (MRM) mode.

[0124] Results are shown in Table 1 Figure 14 (b) It was observed that with the increase of spray voltage, the PS signal first increased and then decreased. When the spray voltage was set to 3400 V, the signal intensity was the strongest, indicating that at 3400 V, the atomization efficiency of the target OPPs ion was the best. If the applied voltage is too low, the surface tension of the liquid will not be overcome, so that the atomization cannot be effectively formed, resulting in a decrease in ionization efficiency. When the applied voltage is too high, it may cause the occurrence of discharge phenomenon, and then cause local high temperature. This high temperature environment can damage the molecular structure of the target analyte, causing excessive fragmentation, and finally producing unexpected fragmentation products in the ion source.

[0125] 3. Effect of spray solvent on the recovery rate of OPPs

[0126] Five solvents, methanol, ethanol, isopropanol, n-hexane and acetonitrile, were selected and added dropwise to the COF-300@paper paper substrate prepared in Example 2 for testing. By comparing the signal response intensity of the COF-300@paper modified material to the organic phosphorus pesticide (OPPs) multi-response monitoring (MRM) mode, the optimal solvent selection was finally determined.

[0127] The results showed that Figure 14(c) As shown in the comparative test of five spraying solvents of methanol, ethanol, isopropanol, n-hexane and acetonitrile, the paper spray ionization (PS) signal intensity of the non-polar solvent n-hexane is significantly lower than that of other solvents, indicating that the non-polar solvent is not suitable for paper spray mass spectrometry analysis. In the polar solvents (methanol, acetonitrile, isopropanol, ethanol), ethanol as the spraying solvent shows the highest signal intensity and OPPs recovery rate.

[0128] 4. Influence of COF-300@paper paper substrate tip angle on OPPs signal intensity

[0129] The influence of the COF-300@paper triangular paper substrate tip top angle (10°, 20°, 30°, 40°, 50°, 60°) on the detection sensitivity was investigated. By analyzing the signal response intensity of the COF-300@paper modified material to the organic phosphorus pesticide (OPPs) multiple reaction monitoring (MRM) mode, the optimal paper substrate geometric configuration parameters were finally determined.

[0130] The results are as follows: Figure 14 (d) It is observed that as the tip angle increases, the PSI signal presents a "triangular asymmetric distribution" trend. When the tip angle is set to 30°, the MRM signal of OPPs is the strongest and the recovery rate of OPPs is the highest. The reason is that the signal intensity, spraying current and electric field at the nozzle are all dependent on the angle of the paper tip, and the electric field density of the paper tip cut into a small angle is higher, which is conducive to the generation of spray. However, the area of the corresponding paper is also relatively reduced, and the extracted OPPs are less, and the PSI signal is smaller; as the angle increases to 30°, the extracted OPPs increase, and the PS signal intensity is the highest. The larger the angle, the more difficult it is to excite ionization, and the PSI signal decreases; when the angle increases to a certain extent, although the ionization is difficult, the amount of extracted OPPs is relatively large, resulting in an increase in the PSI signal.

[0131] Comparative Example 1

[0132] Compared with the existing OPPs analysis method, the specific comparison is shown in Table 5:

[0133] Table 5 Comparison of the present method with other OPPs residue determination methods

[0134]

[0135] As can be seen from the results, the detection limit and the quantitative limit of the present method are lower, and the present method has the advantages of high efficiency, fast speed, and less solvent consumption. The extraction time of 5 kinds of OPPs is short (COF-300 can reach about 90% of the OPPs equilibrium adsorption capacity in about 5 minutes). Moreover, the present method also has the characteristics of simple operation and low matrix effect, and can be used for the analysis of OPPs residues in complex food matrix samples.

[0136] [1] Farajzadeh M A, Mogaddam M R A, Aghdam S R, et al. Application of elevated temperature-dispersive liquid-liquid microextraction for determination of organophosphorus pesticides residues in aqueous samples followed by gas chromatography-flame ionization detection [J]. Food Chemistry, 2016, 212: 198-204.

[0137] [2] Shakourian M, Yamini Y, Safari M. Facile magnetization of metal-organic framework TMU-6 for magnetic solid-phase extraction of organophosphorus pesticides in water and rice samples [J]. Talanta, 2020, 218: 121139.

[0138] [3] Tan L, Li W, Li H, et al. Development of surface imprinted core-shell nanoparticles and their application in a solid-phase dispersion extraction matrix for methyl parathion [J]. Journal of Chromatography A, 2014, 1336: 59-66.

[0139] [4] Chang H W, Chen C L, Chen Y H, et al. Electrochemical organophosphorus pesticide detection using nanostructured gold-modified electrodes [J]. Sensors, 2022, 22(24): 9938.

[0140] [5]Zhou Q, Wang L, Pan C, et al. Multi-pesticides analysis in honeysuckle and chrysanthemums based on nano-material modified QuEChERs coupled with HPLC-MS / MS [J]. Microchemical Journal, 2025: 112999.

[0141] The above provided examples are not intended to limit the scope of the present application, nor are the described steps intended to limit the order of their execution. Those skilled in the art will make obvious modifications to the present application in light of the existing common knowledge, which also falls within the protection scope defined by the claims of the present application.

Claims

1. A method for detecting organophosphorus residues in medicinal and edible products based on paper spray mass spectrometry, characterized in that: The method comprises the following steps: (1) Sample pretreatment Weigh the sample to be tested and disperse it in an acetic acid aqueous solution. After ultrasonication, add dichloromethane, shake, centrifuge, and recover the organic layer to obtain the test solution. (2) Determination of organic phosphorus content in the sample to be tested The COF-300@paper substrate is placed in the test solution of step (1) for extraction, dried after extraction, and the solvent ethanol is sprayed dropwise onto the COF-300@paper substrate. The mass spectrometry system is used for detection, and the content of OPPs in the test sample is calculated based on the test results and the standard curve; The COF-300@paper substrate is prepared by mixing COF-300 powder with ultrapure water to obtain a uniformly dispersed suspension, which is then transferred to a Buchner funnel filled with filter paper. The suspension is then filtered under vacuum to obtain a filter paper matrix loaded with COF-300, and the COF-300@paper substrate is obtained by drying.

2. The method according to claim 1, characterized in that The organophosphorus includes one or more of fenthion, phosalone, dimethoate, phosmet, and acephate.

3. The method according to claim 1, characterized in that The medicine and food products include one or more of hawthorn, ginseng and coix seed tea, red ginseng and rose vitality tea, red ginseng and rose dandelion tea, wolfberry, and ginseng.

4. The method according to claim 1, wherein The amount of COF-300 loaded on each filter paper with a diameter of 3.5 cm on the COF-300@paper paper base is 2.5 to 12.5 mg.

5. The method according to claim 1, wherein The COF-300@paper paper base in step (2) is an isosceles triangle with a tip apex angle of 10 to 60 degrees.

6. The method according to claim 1, characterized in that The COF-300 powder is prepared by using terephthalaldehyde (BDA) and tetrakis(4-aminophenyl)methane (TAM) as monomers and reacting them at a temperature of 40 to 45° C. for 36 to 48 hours.

7. The method according to claim 1, characterized in that The specific preparation method of the COF-300 powder is as follows: (1) BDA, 1,4-dioxane, and CF3CH2NH2 were mixed, vortexed, and then CF3COOH was added to obtain reaction solution A; (2) dissolving TAM in 1,4-dioxane to obtain reaction solution B; (3) Add reaction solution B to reaction solution A, filter, and allow to react at a temperature of 40-45° C. for 36-48 hours. After the reaction is completed, extract the synthesized crystals by Soxhlet extraction in 1,4-dioxane and tetrahydrofuran, respectively, and dry to obtain yellow crystals, i.e., COF-300 powder.

8. The method according to any one of claims 6 or 7, characterized in that: The mass ratio of BDA to TAM is 10-15:

20.

9. The method according to claim 1, characterized in that The mass spectrometry parameters of the mass spectrometry system in step (2) are as follows: curtain gas: 10 psi; ion source gas 1: 0 psi; ion source gas 2: 0 psi; spray voltage 3400 V; IHT: 150°C; collision gas: nitrogen; inlet voltage: 10 V; outlet voltage: 10 V; multiple reaction monitoring (MRM) positive ion mode scan with a scan rate of 10 Da / s; and a paper base angle of 30°.

10. Use of the method according to any one of claims 1 to 9 in food safety monitoring.

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