Application of Fe-MOF in the detection of tert-butylhydroquinone in food and fluorescence analysis method

Abstract

The present invention discloses an application of Fe-MOF in detecting tert-butylhydroquinone in food and a fluorescence analysis method, relating to the field of chemical analysis and detection technology. The Fe-MOF is obtained by dissolving FeCl3·6H2O and 2-aminoterephthalic acid in an organic solvent and then heating the mixture. The method uses Fe-MOF as a fluorescent response agent and adopts a standard curve method to perform fluorescence analysis on tert-butylhydroquinone. The present invention provides a new fluorescence analysis method for detecting tert-butylhydroquinone (TBHQ). The method has high sensitivity, simple detection, good stability, and high selectivity. Under optimal detection conditions, the linear range is 0-150 μmol / L and the detection limit is as low as 0.03 μmol / L. The method can detect TBHQ quickly, highly sensitively, and selectively.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical analysis and detection, and in particular to an application of Fe-MOF in detecting tert-butylhydroquinone in food and a fluorescence analysis method. Background Art

[0002] Tert-Butylhydroquinone (TBHQ) is a synthetic phenolic antioxidant commonly used in edible oils. It exhibits strong anti-lipid peroxidation properties, good chemical stability, and low cost. Health studies have shown that high doses of TBHQ in food may cause health problems, including cytotoxicity and carcinogenicity. Therefore, the use of TBHQ in food must be strictly regulated. Many countries (such as the United States and China) have established regulatory agencies. my country's food additive standard, GB / T 2760-2014, stipulates a maximum allowable addition of TBHQ to food of 200 mg / kg.

[0003] Currently, numerous analytical methods exist for the detection of TBHQ, including traditional methods such as high-performance liquid chromatography, gas chromatography, and gas chromatography-mass spectrometry. However, these methods also have limitations, such as the need for expensive instrumentation, time-consuming procedures, and complex sample preparation. Therefore, the development of a simple, selective, and cost-effective method for the detection of TBHQ is urgently needed.

[0004] Compared with traditional detection methods, fluorescence analysis has many advantages such as simple operation, high sensitivity, time saving and low cost. Therefore, fluorescence analysis has received continuous attention from researchers in the past few decades. Metal-organic framework (MOFs) is a new type of multifunctional coordination polymer. After decades of research, a large number of different types of MOFs have been produced, which have been widely used in catalysis, chemical sensing, bioimaging and other fields. However, the development of a MOF material to achieve highly sensitive and selective detection of TBHQ still faces challenges. Summary of the Invention

[0005] The purpose of the present invention is to provide an application of Fe-MOF in the detection of tert-butylhydroquinone in food and a fluorescence analysis method to solve the problems existing in the above-mentioned prior art and achieve highly sensitive and selective detection of TBHQ.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the purposes of the present invention is to provide an application of Fe-MOF in detecting tert-butylhydroquinone in food.

[0008] Furthermore, the preparation method of the Fe-MOF comprises the following steps:

[0009] FeCl3·6H2O and 2-aminoterephthalic acid are dissolved in an organic solvent and then reacted at 100-150°C for 12-60 hours to obtain the Fe-MOF. The preferred reaction temperature is 110°C and the reaction time is 24 hours.

[0010] The second purpose of the present invention is to provide a fluorescence analysis method for detecting tert-butylhydroquinone in food based on Fe-MOF, using Fe-MOF as a fluorescence response agent and a standard curve method to perform fluorescence analysis of tert-butylhydroquinone.

[0011] Furthermore, the fluorescence analysis method comprises the following steps:

[0012] (1) Preparation of Fe-MOF: FeCl3·6H2O and 2-aminoterephthalic acid are dissolved in an organic solvent, and then reacted at 100-150°C for 12-60 hours to obtain the Fe-MOF; preferably, the reaction temperature is 110°C and the reaction time is 24 hours.

[0013] (2) mixing the Fe-MOF with a standard solution of tert-butylhydroquinone, incubating the obtained mixed solution, and drawing a linear curve of tert-butylhydroquinone concentration and Fe-MOF fluorescence intensity;

[0014] (3) The food is subjected to tert-butylhydroquinone extraction to obtain an extract, the obtained extract is mixed with Fe-MOF, the obtained mixture is incubated, and then the Fe-MOF is used for fluorescence analysis to obtain the content of tert-butylhydroquinone in the food.

[0015] Furthermore, in step (1), the molar ratio of FeCl3·6H2O to 2-aminoterephthalic acid is 1-3:1-3, preferably 3:2.

[0016] Furthermore, in steps (2) and (3), the concentration of Fe-MOF in the mixed solution is 0.5 mg / mL.

[0017] Furthermore, in step (3), the incubation temperature is 25-50°C, and the incubation time is 0-50 minutes. Preferably, the incubation temperature is 30°C, and the incubation time is 30 minutes.

[0018] The present invention discloses the following technical effects:

[0019] The present invention aims to provide a novel method for the determination of TBHQ. An off-on fluorescence analysis method based on Fe-MOF has been developed, offering a novel fluorescence analysis method for the detection of TBHQ with high sensitivity, ease of detection, excellent stability, and high selectivity. Under optimal detection conditions, this sensing method exhibits a linear range of 0-150 μmol / L and a limit of detection as low as 0.03 μmol / L. This method enables rapid, highly sensitive, and selective detection of TBHQ. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is an X-ray photoelectron spectrum of Fe-MOF according to an embodiment of the present invention;

[0022] Figure 2 This is the Fourier transform infrared spectrum of Fe-MOF according to an embodiment of the present invention;

[0023] Figure 3 This is the PXRD pattern of Fe-MOF in the embodiment of the present invention;

[0024] Figure 4 This is the excitation spectrum of Fe-MOF in the embodiment of the present invention;

[0025] Figure 5 The emission spectra of Fe-MOF and ligand NH2-BDC in the embodiment of the present invention;

[0026] Figure 6 The effect of different mass concentrations of Fe-MOF on fluorescence intensity in the embodiment of the present invention;

[0027] Figure 7 The fluorescence intensity of Fe-MOF under different TBHQ concentrations in the embodiment of the present invention;

[0028] Figure 8 This is a linear relationship diagram between the fluorescence intensity of Fe-MOF and the concentration of TBHQ in an embodiment of the present invention;

[0029] Figure 9 The effect of incubation temperature on the fluorescence intensity of Fe-MOF in the embodiment of the present invention;

[0030] Figure 10 The effect of incubation time on the fluorescence intensity of Fe-MOF in the embodiment of the present invention;

[0031] Figure 11 The effects of different interfering substances on the fluorescence intensity of Fe-MOF in the presence or absence of TBHQ in the embodiments of the present invention are shown;

[0032] Figure 12 This is the stability analysis of Fe-MOF in the embodiment of the present invention. DETAILED DESCRIPTION

[0033] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0034] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0035] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0036] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0037] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0038] The present invention provides a new method for determining TBHQ, comprising the following steps:

[0039] The first step is the synthesis of Fe-MOF: FeCl3·6H2O (1-3 mmol) and 2-aminoterephthalic acid (NH2-BDC) (1-3 mmol) are dissolved in DMF and the resulting mixture is vigorously stirred at room temperature for 1-5 hours. After stirring and dissolving, it is poured into an autoclave and heated at 100-150°C for 12-60 hours. After the autoclave gradually cools to room temperature, a brown precipitate is collected by centrifugation. The precipitate is washed three times with DMF to remove unreacted metal salts and ligands, and then washed three times with CH2Cl2 to remove residual DMF molecules in the pores. The precipitate is then vacuum dried overnight at 30-100°C to remove CH2Cl2 in the pores, resulting in a brown microcrystalline powder.

[0040] The second step is to prepare a 100 mmol / L TBHQ standard solution.

[0041] The specific preparation process is as follows: Accurately weigh 0.416g of TBHQ (relative molecular mass 166.22) into a small beaker, dissolve it in 5mL of anhydrous ethanol, and transfer it to a 25mL volumetric flask. Rinse the beaker with 1mL of anhydrous ethanol and transfer it to the 25mL volumetric flask. Wash at least three times. Dilute to the mark with anhydrous ethanol to obtain a TBHQ standard solution. Store the TBHQ standard solution in a brown bottle at 4°C until needed.

[0042] In the third step, a certain amount of TBHQ standard solution was mixed with Fe-MOF to achieve a Fe-MOF concentration of 0.5 mg / mL in the resulting suspension. The suspension was then incubated at 30°C for 30 minutes. The fluorescence intensity of the mixed solutions at different TBHQ concentrations was then recorded at a fixed excitation wavelength of 350 nm. (To ensure the accuracy of the measurement results, each sample was measured in triplicate.) The fluorescence intensity of Fe-MOF at different TBHQ concentrations was recorded, and a linear curve was plotted showing the relationship between TBHQ concentration and Fe-MOF fluorescence intensity.

[0043] The fourth step is the pretreatment of the actual sample: the edible oil sample is extracted using an organic solvent (such as methanol, ethanol, acetonitrile, etc.), and the extracted TBHQ sample is subjected to fluorescence analysis and detection using Fe-MOF.

[0044] Example 1

[0045] A fluorescence analysis method for detecting TBHQ based on Fe-MOF, the specific steps are as follows:

[0046] (1) 0.8106 g of FeCl3·6H2O (3 mmol) and 0.3622 g of 2-aminoterephthalic acid (NH2-BDC) (2 mmol) were dissolved in 24 mL of DMF, and the mixture was vigorously stirred at room temperature for 2 h. After stirring and dissolving, the mixture was poured into a 60 mL autoclave and heated at 110 °C for 24 h. After the autoclave gradually cooled to room temperature, a brown precipitate was collected by centrifugation. The precipitate was washed three times with DMF to remove unreacted metal salts and ligands, and then washed three times with CH2Cl2 to remove residual DMF molecules in the pores. The precipitate was then vacuum dried at 60 °C overnight to remove CH2Cl2 in the pores, and finally a brown microcrystalline powder was obtained.

[0047] The experiment used X-ray photoelectron spectroscopy to explore the surface chemical state of Fe-MOF and the structural details of Fe-MOF. Figure 1 As shown in Figure 2, the synthesized MOF structure contains carbon (C 1s), nitrogen (N 1s), oxygen (O 1s) and iron (Fe 2p), which is consistent with the elements contained in MOF, indicating the successful synthesis of Fe-MOF. Fe-MOF was further characterized by Fourier transform infrared spectroscopy. Figure 2 As shown, at 521cm -1 The newly appeared peak is the stretching vibration of Fe-O, which also indicates the successful synthesis of Fe-MOF. Figure 3 As shown, the PXRD patterns correspond to the crystal planes (002), (101), (103), (200), and (201) of Fe-MIL-88B, indicating that the particles have high crystallinity, which also indicates the successful synthesis of Fe-MOF.

[0048] The test was carried out in a 4 mL quartz cuvette. The instrument parameters of the fluorescence spectrometer were as follows: excitation wavelength 350 nm; excitation and emission wavelength slits were both 5 nm; the light source was a xenon lamp; and the emission spectrum acquisition range was 350-650 nm. Figure 4 is the excitation spectrum of Fe-MOF (excited at 350 nm); Figure 5 The emission spectra of Fe-MOF and ligand NH2-BDC at 450 nm.

[0049] (2) Preparation of TBHQ standard solution: Accurately weigh 0.416 g of TBHQ (relative molecular mass 166.22) into a small beaker, dissolve it with 5 mL of anhydrous ethanol, and transfer it to a 25 mL volumetric flask. Wash the beaker with 1 mL of anhydrous ethanol and transfer it to a 25 mL volumetric flask. Wash at least three times, then dilute to the mark with anhydrous ethanol to obtain a 100 mmol / L TBHQ standard solution. The TBHQ standard solution was stored in a brown bottle at 4°C until use.

[0050] (3) In order to obtain the optimal Fe-MOF mass concentration, a certain amount of ground Fe-MOF powder sample was dispersed in 10 mL of pure water and ultrasonically treated for 30 min to fully disperse it in the aqueous solution, obtaining Fe-MOF dispersions of 0.25, 0.5, 1, 2, and 4 mg / mL, respectively.

[0051] A certain amount of TBHQ standard solution was added to the Fe-MOF dispersion to obtain a mixed solution. The TBHQ concentration in the mixed solution was 100 μmol / L and the Fe-MOF concentration was 0.25, 0.5, 1, 2, and 4 mg / mL. The mixture was incubated at 30°C and 30 min, respectively. The fluorescence spectrum intensity of the Fe-MOF dispersion at different concentrations under the same TBHQ concentration was recorded at a fixed excitation wavelength of 350 nm. The effect of different mass concentrations of Fe-MOF on the fluorescence intensity was measured, and the results are shown in the table. Figure 6 ,from Figure 6 It can be seen that under the condition of 0.5 mg / mL, the fluorescence intensity of Fe-MOF changes the most. This is because when the concentration of Fe-MOF is too high, an inner filter effect will occur, which will reduce the fluorescence intensity of Fe-MOF.

[0052] (4) A certain amount of TBHQ standard solution was added to the Fe-MOF dispersion so that the Fe-MOF concentration in the mixed solution was 0.5 mg / mL and the TBHQ concentration was 0-150 μmol / L. The mixture was incubated at 30°C and for 30 min, respectively. The fluorescence intensity of the Fe-MOF at different TBHQ concentrations was recorded at a fixed excitation wavelength of 350 nm. The fluorescence intensity of the Fe-MOF at different TBHQ concentrations was recorded, and a linear curve of the relationship between TBHQ concentration and Fe-MOF fluorescence intensity was plotted.

[0053] The fluorescence intensity of Fe-MOF at different TBHQ concentrations is shown in Figure 2. Figure 7 As shown in Figure 2, it can be seen that the fluorescence intensity increases with the increase of TBHQ concentration; a linear curve of TBHQ concentration and Fe-MOF fluorescence intensity is drawn, as shown in Figure 2. Figure 8 As shown by Figure 8 It can be seen that TBHQ shows a good linear relationship in the range of 0-150 μmol / L, the linear equation is y=3.607x+35.97, and the detection limit is 0.03 μmol / L.

[0054] (5) Sample pretreatment: TBHQ was extracted according to the national standard sample pretreatment method of GB 5009.32-2016. Specifically, 2 mL of edible oil sample (soybean oil) was mixed with 4 mL of methanol in a 50 mL centrifuge tube with a lid. The mixture was ultrasonicated for 30 min and centrifuged at 5000 rpm for 5 min. After centrifugation, the extract was quantitatively transferred to a 25 mL volumetric flask. To ensure complete extraction, the above extraction process was repeated twice, all the extracts were collected and transferred to a 25 mL volumetric flask, then diluted to the mark with methanol and filtered with an organic membrane (0.22 μm). The filtrate was prepared using the standard addition method for fluorescence detection. All samples were refrigerated before use.

[0055] (6) The above filtrate was mixed with 0.5 mg / mL Fe-MOF aqueous dispersion and incubated at 30°C for 30 min.

[0056] The results of the analysis of the actual pre-treated samples by the analysis method of the present invention and the HPLC analysis method are shown in Table 1. (The detection conditions of the HPLC analysis method are as follows: Chromatographic conditions: Flow rate: 1.0 mL min -1 Injection volume: 5 μL; Column temperature: 35°C; UV detector wavelength: 280 nm; Organic phase: methanol; Aqueous phase: 0.5% formic acid solution.

[0057] Table 1 Analysis of TBHQ real samples in edible oils (n=3)

[0058]

[0059] Example 2 Effect of incubation temperature on Fe-MOF fluorescence intensity

[0060] In order to obtain the optimal incubation temperature, a certain amount of TBHQ standard solution was added to the Fe-MOF dispersion to obtain a mixed solution, so that the concentration of TBHQ in the mixed solution was 100 μmol / L and the concentration of Fe-MOF was 0.5 mg / mL. The incubation was carried out at 25, 30, 35, 40, 45, and 50°C for 30 minutes. The fluorescence spectrum intensity of the different suspensions was then recorded at a fixed excitation wavelength of 350 nm. To ensure the accuracy of the measurement results, the fluorescence intensity at different incubation temperatures was recorded, and a linear curve of TBHQ concentration and Fe-MOF fluorescence intensity was drawn, as shown in Figure 2. Figure 9 As shown. Figure 9 It can be seen that the fluorescence intensity changes the most at 30°C, so the optimal incubation temperature is determined to be 30°C.

[0061] Example 3 Effect of incubation time on Fe-MOF fluorescence intensity

[0062] In order to obtain the optimal incubation time, a certain amount of TBHQ standard solution was added to the Fe-MOF suspension so that the concentration of TBHQ in the mixed solution was 100 μmol / L and the concentration of Fe-MOF was 0.5 mg / mL. The incubation was carried out for 0, 20, 30, 40, and 50 minutes at a temperature of 30°C. The fluorescence spectrum intensity of the different suspensions was then recorded at a fixed excitation wavelength of 350 nm. To ensure the accuracy of the measurement results, the fluorescence intensity at different incubation times was recorded, and a linear curve of TBHQ concentration and Fe-MOF fluorescence intensity was drawn, as shown in Figure 2. Figure 10 As shown. Figure 10 It can be seen that the fluorescence intensity remained basically unchanged after 30 minutes, so the optimal incubation time was determined to be 30 minutes.

[0063] Example 4 Selectivity of Fe-MOF for TBHQ

[0064] The selectivity of Fe-MOF for TBHQ was experimentally verified as follows:

[0065] Interference is a key issue that many sensors need to solve. A good fluorescence sensor should have excellent anti-interference performance. The anti-interference performance of the developed TBHQ sensor was investigated under the condition of 200 μmol / L TBHQ concentration. Typical interfering substances, such as propyl gallate (PG), 2,6-di-tert-butyl-p-cresol (BHT), butylated hydroxyanisole (BHA) and some common ions Na + , K + 、Zn 2+ 、Cl - 、NO 3- The effects of the fluorescence intensity of Fe-MOF are as follows Figure 11 As shown. Studies have shown that in the presence of the same concentration (200 μmol / L) of interfering substances, the fluorescence intensity of the Fe-MOF barely changes. Only after the addition of TBHQ does the fluorescence intensity change significantly, demonstrating the good selectivity of the Fe-MOF-based fluorescence sensor. The experimental results show that the present invention can selectively detect TBHQ even in the presence of interfering substances.

[0066] Example 5 Stability of Fe-MOF Fluorescence Analysis

[0067] Figure 12The fluorescence intensity changes of the Fe-MOF before and after the addition of TBHQ over a continuous 72-hour period are shown. Over this period, the fluorescence intensity of the TBHQ sensor (i.e., Fe-MOF) changes minimally. When TBHQ is present in the system, the fluorescence intensity difference between 0 and 72 hours is only 2.4%. This experimental result demonstrates the excellent stability of the Fe-MOF-based TBHQ fluorescence sensor.

[0068] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. Application of Fe-MOF in detecting tert-butylhydroquinone in food, characterized in that: The preparation method of the Fe-MOF comprises the following steps: FeCl3·6H2O and 2-aminoterephthalic acid are dissolved in an organic solvent and then reacted at 100-150°C for 12-60h to obtain the Fe-MOF.

2. A fluorescence analysis method for detecting tert-butylhydroquinone in food based on Fe-MOF, characterized in that: Using Fe-MOF as a fluorescent response agent, a standard curve method is used to perform fluorescence analysis on tert-butylhydroquinone; the fluorescence analysis method comprises the following steps: (1) preparing Fe-MOF: dissolving FeCl3·6H2O and 2-aminoterephthalic acid in an organic solvent, and then reacting at 100-150°C for 12-60 hours to obtain the Fe-MOF; (2) mixing the Fe-MOF with a standard solution of tert-butylhydroquinone, incubating the obtained mixed solution, and drawing a linear curve of tert-butylhydroquinone concentration and Fe-MOF fluorescence intensity; (3) The food is subjected to tert-butylhydroquinone extraction to obtain an extract, the obtained extract is mixed with Fe-MOF, the obtained mixture is incubated, and then the Fe-MOF is used for fluorescence analysis to obtain the content of tert-butylhydroquinone in the food.

3. The fluorescence analysis method according to claim 2, characterized in that In step (1), the molar ratio of FeCl3·6H2O to 2-aminoterephthalic acid is 1-3:1-3.

4. The fluorescence analysis method according to claim 2, wherein In steps (2) and (3), the concentration of Fe-MOF in the mixed solution was 0.5 mg / mL.

5. The fluorescence analysis method according to claim 2, characterized in that In step (3), the incubation temperature is 25-50° C., and the incubation time is 0-50 min.

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