Application of impurity adsorption type dispersive solid-phase extraction agent in solanine detection

Abstract

The invention provides an impurity adsorption type dispersive solid-phase extraction agent MOF-808 and application thereof in solanine detection, and the impurity adsorption type dispersive solid-phase extraction agent MOF-808 can be used for purifying a sample pretreatment extracting solution. The MOF-808 provided by the invention shows impurity adsorption capacity due to high specific surface area, adjustable aperture and easy-to-functionalize surface chemical properties, realizes purification of a sample extracting solution, has the advantages of simplicity and convenience in operation, high efficiency, low cost and the like when being applied to pretreatment of a sample during solanine detection, and has a wide application prospect. Therefore, the subsequent accurate detection of the solanine is facilitated.

Description

Application of an impurity adsorption type dispersed solid phase extractant in the detection of solanine Technical Field

[0001] This invention belongs to the field of food safety testing technology, specifically relating to the application of an impurity adsorption type dispersed solid phase extractant in the detection of solanine. Background Technology

[0002] Solanine is a class of steroidal glycoside alkaloids naturally found in Solanaceae plants such as potatoes and eggplants. It mainly includes α-solanine and α-chaconine, accounting for 90% to 95% of total solanine. This class of substances has a rigid steroidal backbone connecting three sugar groups and is an important component of the plant's own defense system. However, its content can significantly increase when solanine fruits are improperly stored (e.g., sprouting, greening, or mechanical damage). Excessive intake of solanine can cause acute poisoning reactions in humans, including gastrointestinal discomfort, neurological disorders, and cerebral edema, which can be life-threatening in severe cases. Health Canada has set the maximum limit for the combined content of α-solanine and α-chaconine in potato tubers at 200 mg / kg in its "List of Food Contaminants and Other Adulterants." Therefore, establishing a rapid, accurate, and sensitive method for detecting solanine is of great significance for ensuring the safety of solanine fruits and their products for consumption.

[0003] Currently, the mainstream detection method for α-solanine and α-carboxane is high-performance liquid chromatography-mass spectrometry (HPLC-MS). However, real-world samples (such as potatoes, potato chips, and tomato sauce) have complex matrices containing large amounts of starch, proteins, organic acids, pigments, and other structurally similar steroidal compounds. These coexisting impurities can cause severe matrix effects during instrumental analysis, interfering with the ionization efficiency of the target analytes and potentially contaminating the chromatographic column and mass spectrometry ion source, leading to decreased detection sensitivity, inaccurate quantification, and reduced instrument stability. Traditional sample pretreatment methods, such as liquid-liquid extraction and solid-phase extraction, while offering some purification effects, are typically cumbersome, time-consuming, and lack the ability to effectively remove multiple polar interfering substances (such as sugars and organic acids) in complex matrices, making it difficult to achieve highly selective purification.

[0004] MOF-808 is a Zr-based MOF, with trimesic acid as the organic ligand, covalently linked to zirconium-based secondary building blocks [Zr6O4(OH)4(HCOO)6] to form a three-dimensional polyhedral structure. Compared to traditional inorganic porous materials such as zeolites, montmorillonite, and molecular sieves, MOF-808 exhibits high stability, a large specific surface area, and excellent adsorption performance. It interacts with target substances through electrostatic adsorption, π-π conjugation, hydrogen bonding, and hydrophobic / hydrophilic interactions, and is widely used in food safety for CO2 capture and catalytic conversion, water environment remediation, and the adsorption and removal of toxic and harmful substances. However, MOF-808 prepared by different methods exhibits differences in structure and performance.

[0005] Therefore, it is necessary to research and develop efficient and reliable sample pretreatment techniques to ensure the accuracy of α-solanine and α-carboxine detection results. Summary of the Invention

[0006] This invention first provides an impurity adsorption type dispersed solid-phase extractant, namely MOF-808. Specifically, this dispersed solid-phase extractant is prepared by the following method: ZrOCl2·8H2O is weighed into a beaker, N,N-dimethylformamide and formic acid are added sequentially, and the mixture is sonicated until completely dissolved. Then, 1,3,5-benzenetricarboxylic acid is added to the beaker and sonicated until dissolved. The mixed solution is transferred to a polytetrafluoroethylene liner and placed in a stainless steel reactor, where it is reacted at 120°C for 24 h. After the reaction is completed and cooled to room temperature, the solution is centrifuged to collect the white precipitate. The precipitate is then ultrasonically washed sequentially with N,N-dimethylformamide and methanol, centrifuged after each wash, and the precipitate is collected. The white precipitate is vacuum dried to obtain MOF-808 purification material. ZrOCl2·8H2O, N,N-dimethylformamide, and formic acid are added sequentially. The ratio of N-dimethylformamide, formic acid and 1,3,5-benzenetricarboxylic acid is 30-50 mg: 0.1-10 mL: 0.1-10 mL: 7-10 mg; the preferred ratio is 30-50 mg: 1 mL: 1 mL: 7-10 mg; and the more preferred ratio is 35-40 mg: 1 mL: 1 mL: 8-9 mg.

[0007] This invention also provides the application of the above-mentioned MOF-808 in the detection of solanine. Specifically, the MOF-808 provided by this invention can be used for sample pretreatment for the detection of solanine in eggplant and solanaceous fruits, wherein the solanine includes α-solanine and α-carboxine. This invention also provides a sample pretreatment method for the detection of solanine in eggplant and solanaceous fruits, which includes the following steps: weigh the sample into a centrifuge tube, add 75% ethanol aqueous solution, then add anhydrous magnesium sulfate and sodium acetate, shake vigorously, sonicate for 15-30 min, vortex for 15-30 min, centrifuge, take the supernatant and blow it dry with nitrogen, reconstitute with methanol-water mixture (2:8, V / V), add the above-prepared MOF-808, sonicate for 2-5 min, vortex for 6-10 min, centrifuge at 12000 r / min for 5 min, and filter the supernatant through 0.22 μL. The sample was filtered through a μm nylon membrane and then subjected to chromatography and mass spectrometry. The weight ratio of the sample to anhydrous magnesium sulfate and sodium acetate was 3-5:1:1; the ratio of the sample to 75% ethanol aqueous solution was 1g:4-6mL.

[0008] This invention also provides a method for detecting solanine in eggplant and solanaceous fruits, the method comprising the following steps: (1) Pretreatment of eggplant and solanaceous fruit samples: weigh the sample into a centrifuge tube, add 75% ethanol aqueous solution, then add anhydrous magnesium sulfate and sodium acetate, shake vigorously and sonicate for 15-30 min, vortex for 15-30 min, centrifuge, take the supernatant and blow it dry with nitrogen, reconstitute with methanol-water mixed solution (2:8, V / V), add the MOF-808 prepared above, sonicate for 2-5 min, vortex for 6-10 min, centrifuge at 12000 r / min for 5 min, pass the supernatant through a 0.22 μm nylon filter membrane and then perform chromatography and mass spectrometry determination; wherein the weight ratio of sample to anhydrous magnesium sulfate and sodium acetate is 3-5:1:1; the ratio of sample to 75% ethanol aqueous solution is 1 g:4-6 mL; (2) Instrument conditions for determination: the chromatographic parameters are as follows: column: Xbridge BEH C 18 (2.5 μm, 3.0 × 100 mm); Mobile phase A: acetonitrile, Mobile phase B: 5 mmol / L ammonium acetate aqueous solution (containing 0.1% formic acid aqueous solution by volume); Column temperature: 40℃; Gradient elution conditions: 0.0–5.0 min, 20% A–55% A; 5.0–5.5 min, 55% A–90% A; 5.5–6.5 min, 90% A; 6.5–6.6 min, 90% A–20% A; 6.6–8.0 min, 20% A; Mass spectrometry parameters are as follows: in positive ion ionization mode of electrospray ionization source (ESI) +The target compound was accurately quantified by scanning using multiple reaction monitoring (MRM) mode. The desolvation gas and the cone gas were both high-purity nitrogen, and the collision gas was high-purity argon. The desolvation temperature was 500°C, the ion source temperature was 150°C, and the cone gas flow rate and the desolvation gas flow rate were 7 and 1000 L / h, respectively. The parent ion, daughter ion, collision energy and other parameters of α-solanine and α-carbohydrate are shown in Table 1.

[0009] Table 1. Mass spectrometric parameters of α-solanic acid and α-carbohydrate

[0010] Note: * indicates quantitative ions. This invention addresses the shortcomings of existing technologies by providing a method for preparing an impurity-adsorbing dispersed solid-phase extractant and its application in the detection of solanine. It is used to purify the sample pretreatment extract when detecting α-solanine and α-carboxine in eggplant fruits. Impurities in the extract are adsorbed, and the target analytes are directly tested by centrifugation. The method is rapid, accurate, and efficient.

[0011] The sample pretreatment using MOF-808 provided by this invention for solanine detection has advantages such as simple operation, high efficiency, and low cost. Furthermore, compared with commonly used adsorbents such as PSA and C18, metal-organic framework materials (MOF-808) exhibit superior adsorption and separation performance for impurities due to their high specific surface area, tunable pore size, and easily functionalizable surface chemistry, thus facilitating the accurate detection of solanine. Attached Figure Description

[0012] Figure 1. Structure and morphology characterization of MOF-808; (A) Fourier transform infrared spectrum of MOF-808; (B) X-ray diffraction pattern of MOF-808; (C) Scanning electron microscope image of MOF-808; (D) N2 adsorption-desorption isotherm and pore size distribution of MOF-808. Figure 2. Comparison of extract before and after purification. Figure 3. Comparison of MRM of extract before and after purification. The specific embodiments of the present invention will be described in detail below with reference to the examples. However, the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0013] Instruments and reagents: Ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC XEVO TQ-S, Waters Corporation, USA); Vacuum drying oven (DZF-6050, Shanghai Banno Biotechnology Co., Ltd.); Hydrothermal synthesis reactor (100 mL, Shanghai Huotong Experimental Instrument Co., Ltd.); Cyclotron (200A, Shanghai Yiheng Technology Co., Ltd.); Ultrasonic cleaner (2500TH, Shanghai Anpu Experimental Technology Co., Ltd.); Ultrapure water system (Millipore Corporation, USA); α-Solanine standard, α-Carbohydrate standard (purity ≥98%, Shanghai Maclean Biochemical Technology Co., Ltd.); Methanol, acetonitrile (chromatographic grade, Merck GmbH, Germany); Formic acid (chromatographic grade, Shanghai Anpu Experimental Technology Co., Ltd.); N,N-Dimethylformamide (99.5%, Shanghai Maclean Biochemical Technology Co., Ltd.); Zirconium oxychloride octahydrate (analytical grade, 99%, Shanghai Yuanye Biotechnology Co., Ltd.); 1,3,5-Benzotricarboxylic acid (analytical grade, 99%, Shanghai Titan Technology Co., Ltd.); Other materials and reagents were commercially available products.

[0014] Example 1: (1) Material Synthesis Weigh 970 mg ZrOCl2·8H2O into a 100 mL beaker, add 25 mL N,N-dimethylformamide and 25 mL formic acid in sequence, sonicate for 30 min to completely dissolve, then add 210 mg 1,3,5-benzenetricarboxylic acid into the beaker, sonicate until dissolved. Transfer the mixed solution to a 100 mL polytetrafluoroethylene liner and place it in a stainless steel reactor, react at 120°C for 24 h. After the reaction is completed and cooled to room temperature, transfer the solution to a 50 mL centrifuge tube, centrifuge at 10000 r / min for 15 min to collect the white precipitate. Wash the precipitate in sequence with N,N-dimethylformamide (10 mL × 3) and methanol (10 mL × 3) sonicated for 10 min, centrifuge at 5000 r / min for 10 min after each wash, and collect the precipitate. Dry the white precipitate in a vacuum drying oven at 60°C for 12 h to obtain MOF-808 purification material.

[0015] (2) Material characterization The functional groups of the synthesized MOF-808 purification material were analyzed by Fourier transform infrared spectroscopy (FT-IR); the crystal structure was identified by X-ray diffraction (XRD); the morphology of the sample was observed by scanning electron microscopy (SEM); and its specific surface area and pore structure were measured by BET nitrogen adsorption method.

[0016] The infrared spectrum of MOF-808 is shown in Figure 1A, at 1615 cm⁻¹. - ¹ and 1382 cm - The absorption peak at ¹ corresponds to the carboxylate group (-COO) in MOF-808. -Asymmetric and symmetric stretching vibrations, 1574 cm - ¹ and 1445 cm - The absorption peak at ¹ originates from the C=C stretching vibration of the benzene ring skeleton of the ligand 1,3,5-benzenetricarboxylic acid, at 758 cm⁻¹. - ¹ and 660 cm - The absorption peak at ¹ is attributed to the Zr-O bond stretching vibration of the zirconium-oxygen cluster in MOF-808. Further XRD analysis of the crystal structure of MOF-808, as shown in Figure 1B, revealed distinct characteristic diffraction peaks at diffraction angles (2θ) of 8.30°, 8.66°, 10.02°, and 10.90°, confirming the good crystal structure of the synthesized MOF-808. SEM results, as shown in Figure 1C, indicate that the synthesized MOF-808 possesses a regular octahedral structure with uniform size. The N₂ adsorption-desorption isotherm, shown in Figure 1D, is a type I isotherm, indicating that the synthesized material has a microporous structure with an average specific surface area of ​​2386.5 m² / g and a pore size of 1.72 nm. In summary, the characterization results demonstrate the successful synthesis of MOF-808 and its excellent overall performance.

[0017] Example 2 Purification and solanine detection using MOF-808 prepared in Example 1 (1) Sample pretreatment (sample purification) ① Take 200 g of tomato, eggplant and potato samples respectively, homogenize for 2 min and weigh 2.0 g of sample into 50 mL centrifuge tube, add 10 mL of 75% volume ratio ethanol aqueous solution, then add 0.5 g of anhydrous magnesium sulfate and 0.5 g of sodium acetate, shake vigorously for 30 s, sonicate for 30 min, vortex for 30 min, centrifuge at 8000 r / min for 5 min, take 1 mL of supernatant and blow dry with nitrogen at 50℃, redissolve with 1 mL methanol-water mixed solution (2:8, V / V) to obtain sample extract; ② Add 10 mg of MOF-808 impurity adsorbent material to sample extract, sonicate for 4 min, vortex adsorb for 8 min, centrifuge at 12000 r / min for 5 min, filter the supernatant through a 0.22 μm nylon filter membrane and then perform instrumental analysis.

[0018] (2) Instrument conditions and chromatographic parameters are as follows: Column: Xbridge BEH C 18(2.5 μm, 3.0 × 100 mm); Mobile phase A: acetonitrile, Mobile phase B: 5 mmol / L ammonium acetate aqueous solution (containing 0.1% formic acid aqueous solution by volume); Column temperature: 40℃. Gradient elution conditions: 0.0–5.0 min, 20% A–55% A; 5.0–5.5 min, 55% A–90% A; 5.5–6.5 min, 90% A; 6.5–6.6 min, 90% A–20% A; 6.6–8.0 min, 20% A.

[0019] The mass spectrometry parameters are as follows: in positive ion ionization mode of electrospray ionization source (ESI) + The target compounds were accurately quantified using multiple reaction monitoring (MRM) mode. High-purity nitrogen was used for both the desolvation gas and the cone gas, while high-purity argon was used for the collision gas. The desolvation temperature was 500°C, the ion source temperature was 150°C, and the cone gas flow rate and desolvation gas flow rate were 7 and 1000 L / h, respectively. The parent ion, daughter ion, and collision energy parameters of α-solanine and α-carbohydrate are shown in Table 1.

[0020] Table 1. Mass spectrometric parameters of α-solanic acid and α-carbohydrate

[0021] Note: * indicates quantitative ion (3) Results 1. Apparent purification effect: As shown in Figure 2: From the appearance, the sample solution containing α-solanine and α-carboxane after purification by MOF-808 (potato, tomato, eggplant, etc.) is significantly clearer and more transparent than the unpurified sample solution. Moreover, the purified sample solution can remove most interfering impurities such as pigments, and can achieve the purpose of purification; 2. Matrix interference before and after sample purification: As shown in Figure 3A, the unpurified sample has poor peak shape, low sensitivity, and many interfering impurities. As shown in Figure 3B, a good chromatographic peak can be obtained in the matrix standard solution of 1 ng / mL. No matrix interference was found, and there was no interfering chromatographic peak; 3. Method recovery verification: The recovery rate of the method was investigated by matrix spiking method. 2 g of potato, tomato, and eggplant samples were weighed and three concentration levels (low, medium, and high) were added (potatoes were 1, 5, and 10 times the background value, tomatoes and eggplants were 5, 10, and 20 μg / mL, respectively). (kg) of α-solanine and α-carboxane standards were tested in 6 parallel experiments for each. Samples were purified according to the above steps before testing. The recoveries were: potato samples: 92.2-105.9%; tomato samples: 86.2-99.9%; eggplant samples: 88.1-100.8%. 4. Method precision validation: On the same day, 6 parallel samples were tested, and the intra-day precision after purification and testing was 1.8-4.9%. For 6 consecutive days, 6 parallel samples were tested each day, and the inter-day precision was 2.7-6.2% after calculation.

[0022] 5. Evaluation of matrix effect: Standard working solutions were prepared using purified extracts from potato, tomato, and eggplant samples. Matrix-matched calibration curves were constructed, and the matrix effect was evaluated by the ratio of the slope of the matrix-matched calibration curve to the slope of the standard solution prepared with pure solvent (the ratio of the slope of the matrix-matched calibration curve to the slope of the pure solvent calibration curve was calculated). A matrix effect of 80-120% was considered low, indicating a small matrix effect; <80% matrix effect indicated inhibition; and >120% matrix effect indicated enhancement. The matrix effects for tomato were 102.1-106.4%; for eggplant, 102.9-108.3%; and for potato, 94.4-112.6%. However, due to the diverse range of samples, matrix-matched standard curves were used uniformly for quantitative analysis to ensure the accuracy of the results and reduce interference.

[0023] 6. Actual Sample Analysis: Fifteen tomato samples, 15 eggplant samples, and 15 potato samples from local supermarkets and farmers' markets in Shanghai were analyzed according to the above pretreatment and analytical methods. The results showed that α-solanine and α-carboxine were not detected in any of the tomato samples; α-solanine and α-carboxine were detected in 9 of the eggplant samples, with contents ranging from 0.02 to 0.97 mg / kg; the detection rate of both alkaloids in the potato samples was 100%, with α-solanine contents ranging from 4.36 to 271.35 mg / kg and α-carboxine contents ranging from 0.93 to 258.21 mg / kg, indicating that the method has good adaptability to high-fat matrices.

[0024] In summary, the impurity adsorption-type dispersive solid-phase extractant of this invention can effectively purify α-solanine and α-carboxane from various solanaceous fruits such as potatoes, tomatoes, and eggplants, exhibiting significant purification effects. The preparation cost of the adsorbent used for a single sample does not exceed 2 yuan. The sensitivity of various sample matrices after purification is below 1 ng / mL, significantly higher than existing analytical methods, with high recovery and good precision. Compared with existing commercial solid-phase extraction columns, this method significantly reduces costs, substantially decreases matrix interference, and significantly improves method sensitivity while maintaining or even exceeding accuracy and reproducibility.

[0025] The scope of protection of this invention is not limited to the descriptions in the embodiments. Modifications that do not deviate from the central idea of ​​this invention are all within the scope of protection of this invention.

Claims

1. An impurity adsorption type dispersed solid-phase extractant, wherein the extractant is MOF-808, characterized in that... MOF-808 was prepared by the following method: ZrOCl2·8H2O was weighed into a beaker, N,N-dimethylformamide and formic acid were added sequentially, and the mixture was sonicated until completely dissolved. Then, 1,3,5-benzenetricarboxylic acid was added to the beaker and sonicated until dissolved. The mixed solution was transferred to a polytetrafluoroethylene-lined container and placed in a stainless steel reactor. The reaction was carried out at 120°C for 24 h. After the reaction was completed and cooled to room temperature, the solution was centrifuged to collect the white precipitate. The precipitate was ultrasonically washed sequentially with N,N-dimethylformamide and methanol. After each washing, the precipitate was centrifuged and collected. The white precipitate was vacuum dried to obtain MOF-808 purification material. The ratio of ZrOCl2·8H2O, N,N-dimethylformamide, formic acid and 1,3,5-benzenetricarboxylic acid was 30-50 mg: 0.1-10 mL: 0.1-10 mL: 7-10 mg.

2. The impurity adsorption type dispersed solid-phase extractant according to claim 1, characterized in that... The ratio of ZrOCl2·8H2O, N,N-dimethylformamide, formic acid, and 1,3,5-benzenetricarboxylic acid is 30-50 mg: 1 mL: 1 mL: 7-10 mg.

3. The impurity adsorption type dispersed solid-phase extractant according to claim 1, characterized in that... The ratio of ZrOCl2·8H2O, N,N-dimethylformamide, formic acid, and 1,3,5-benzenetricarboxylic acid is 35-40 mg: 1 mL: 1 mL: 8-9 mg.

4. The application of MOF-808 as described in claim 1 in the detection of solanine, characterized in that... MOF can be used for sample pretreatment for the detection of solanine in eggplant and solanaceous fruits, wherein the solanine comprises α-solanine and α-carboxine.

5. A sample pretreatment method for detecting solanine in eggplant and solanaceous fruits, comprising the following steps: weighing the sample into a centrifuge tube, adding 75% ethanol aqueous solution, then adding anhydrous magnesium sulfate and sodium acetate, shaking vigorously, sonicating for 15-30 min, vortexing for 15-30 min, centrifuging, taking the supernatant and blowing it dry with nitrogen, reconstituted with methanol-water mixed solution, adding MOF-808 as described in claim 1, sonicating for 2-5 min, vortexing for 6-10 min, centrifuging at 12000 r / min for 5 min, and passing the supernatant through a 0.22 μm nylon filter membrane for chromatography and mass spectrometry determination; wherein the weight ratio of sample to anhydrous magnesium sulfate and sodium acetate is 3-5:1:1; the ratio of sample to 75% ethanol aqueous solution is 1 g:4-6 mL.

6. A method for detecting solanine in eggplant fruit, the method comprising the following steps: (1) Pretreatment of eggplant fruit sample: Weigh the sample into a centrifuge tube, add 75% ethanol aqueous solution, then add anhydrous magnesium sulfate and sodium acetate, shake vigorously and sonicate for 15-30 min, vortex for 15-30 min, centrifuge, take the supernatant and blow it dry with nitrogen, reconstitute with methanol-water mixed solution, 2:8, V / V, add MOF-808 as described in claim 1, sonicate for 2-5 min, vortex for 6-10 min, centrifuge at 12000 r / min for 5 min, pass the supernatant through a 0.22 μm nylon filter membrane and then perform chromatography and mass spectrometry determination; wherein the weight ratio of sample to anhydrous magnesium sulfate and sodium acetate is 3-5:1:1; the ratio of sample to 75% ethanol aqueous solution is 1 g: 4-6 mL; (2) Instrument conditions for determination: The chromatographic parameters are as follows: Column: Xbridge BEH C 18 2.5 μm, 3.0 × 100 mm; Mobile phase A: acetonitrile, Mobile phase B: 5 mmol / L ammonium acetate aqueous solution, aqueous solution containing 0.1% formic acid (v / v); Column temperature: 40℃; Gradient elution conditions: 0.0–5.0 min, 20% A–55% A; 5.0–5.5 min, 55% A–90% A; 5.5–6.5 min, 90% A; 6.5–6.6 min, 90% A–20% A; 6.6–8.0 min, 20% A; Mass spectrometry parameters are as follows: in positive ion ionization mode ESI of electrospray ionization source. + The target compounds were accurately quantified by scanning using multiple reaction monitoring (MRM) mode. The desolvation gas and the cone gas were both high-purity nitrogen, and the collision gas was high-purity argon. The desolvation temperature was 500°C, the ion source temperature was 150°C, and the cone gas flow rate and the desolvation gas flow rate were 7 and 1000 L / h, respectively. The parent ion, daughter ion, collision energy, and other parameters of α-solanine and α-carbohydrate are shown in Table 1.

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