A method for detecting zinc ions

Abstract

The present invention discloses a method for detecting curcumin and zinc ions. The emission fluorescence of NH2-MIL-101(Fe) is quenched in a concentration-dependent manner using curcumin, and curcumin is quantitatively detected according to the linear relationship between the concentration of curcumin and the reduction in the emission fluorescence intensity of NH2-MIL-101(Fe). The zinc ion detection method is based on the "OFF-ON" principle, which relies on curcumin to first adsorb and quench the emission fluorescence of NH2-MIL-101(Fe), and zinc ions of different concentrations can restore the fluorescence quenched by curcumin to varying degrees, thereby fitting the linear relationship between the zinc ion concentration and the fluorescence intensity recovery amount, and calculating the concentration of zinc ions in the sample according to the linear relationship. The detection method of curcumin and zinc ions of the present invention is more convenient and fast, with high accuracy, low detection limit, high selectivity, strong anti-interference ability, and has a strong practical detection application prospect.

Description

Technical Field

[0001] The invention relates to a quantitative detection method based on fluorescent substances, and in particular to a method for quantitatively detecting curcumin and zinc ions. Background Art

[0002] Curcumin (Cur) is a diketone compound extracted from the rhizomes of turmeric, zedoary turmeric, mustard and other plants of the ginger family. It is an orange-yellow crystalline powder with a slightly bitter taste. It is insoluble in water but soluble in organic solvents such as ethanol. Curcumin is widely used in the pharmaceutical and food industries as a spice and food pigment, and has multiple pharmacological effects such as anti-inflammatory, antioxidant, anti-tumor, and anti-atherosclerosis. However, excessive consumption of curcumin can lead to adverse consequences such as contact dermatitis, gastrointestinal pain, and uterine damage. In severe cases, it may also damage liver cells, causing liver poisoning and even life-threatening.

[0003] Zinc (II) is the second most essential trace metal element in the human body and plays an important role in maintaining normal physiological activities and energy conversion. When the zinc content in the human body is low, it will affect growth and development, the immune system, taste, vision, etc. However, excessive intake of zinc can also cause a variety of diseases. In mild cases, symptoms such as nausea, vomiting, and diarrhea may occur, while in severe cases, epilepsy, ischemic stroke, Alzheimer's disease, and Parkinson's disease may occur.

[0004] At present, the commonly used detection methods for curcumin include colorimetry, ultraviolet spectrophotometry, high performance liquid chromatography, capillary electrophoresis, etc. 2+ ) detection methods mainly include colorimetry, atomic absorption spectrometry, high performance liquid chromatography, potentiometric titration, chemiluminescence, etc. The above methods have their own characteristics, but there are disadvantages such as cumbersome operation, high requirements for instruments and technology, time-consuming and labor-intensive, and unsatisfactory detection sensitivity. Therefore, it is necessary to develop a new efficient, rapid and inexpensive method for detecting curcumin and zinc ions.

[0005] NH2-MIL-101(Fe) belongs to metal organic framework materials (MOF), which is an amino derivative of MIL-101(Fe). It has an octahedral structure, large pore size, large surface area and good adsorption performance. The introduction of amino functional groups gives the material new properties and functions, which can not only increase the hydrophilicity of the material, improve its interaction with certain molecules, and provide new opportunities in catalytic and adsorption applications, but also its fluorescent luminescence characteristics also provide it with broad application prospects in fluorescent chemical sensors. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a method for detecting curcumin, and solve the problem of how to quantitatively detect curcumin based on NH2-MIL-101 (Fe). Another purpose of the present invention is to propose a method for detecting zinc ions, and solve the problem of how to quantitatively detect zinc ions based on curcumin and NH2-MIL-101 (Fe).

[0007] Technical solution: The method for detecting curcumin described in the present invention utilizes the concentration-dependent quenching of the emitted fluorescence of NH2-MIL-101(Fe) by curcumin, and quantitatively detects curcumin based on the linear relationship between the concentration of curcumin and the reduction in the emitted fluorescence intensity of NH2-MIL-101(Fe).

[0008] Preferably, the specific detection method comprises the following steps:

[0009] (1) measuring the fluorescence intensity value of the NH2-MIL-101(Fe) suspension as a first fluorescence intensity value;

[0010] (2) respectively measuring the fluorescence intensity values ​​of the NH2-MIL-101(Fe) suspensions containing different final concentrations of curcumin as the second fluorescence intensity value;

[0011] (3) taking the difference between the first fluorescence intensity value and the second fluorescence intensity value as the emission fluorescence intensity reduction amount;

[0012] (4) fitting to obtain a linear equation between different curcumin concentrations and the decrease in emission fluorescence intensity;

[0013] (5) Substituting the measured value of the decrease in the emission fluorescence intensity of the sample to be tested into the linear equation, the corresponding curcumin concentration in the sample to be tested can be obtained.

[0014] The invention utilizes the ability of curcumin to adsorb and quench the emission fluorescence of NH2-MIL-101 (Fe), fits the linear relationship between the concentration of curcumin and the reduction amount of the emission fluorescence intensity, and calculates the concentration of curcumin in the sample according to the linear relationship.

[0015] Preferably, in steps (1) and (2), the final concentration of the NH2-MIL-101(Fe) suspension is 0.25-1.5 mg / mL, and the solvent is water and / or alcohols. The alcohols include at least one of methanol, ethanol, propanol, and butanol.

[0016] Preferably, in steps (1) and (2), the fluorescence intensity value is determined by exciting NH2-MIL-101(Fe) in the solution at 350 nm and recording the fluorescence intensity value at an emission wavelength of 450 nm.

[0017] Preferably, in step (2), the final concentration of curcumin is 0.1-5 μmol / L and / or 10-100 μmol / L; the NH2-MIL-101(Fe) suspension containing curcumin at different final concentrations is obtained by mixing an alcohol solution of curcumin with an aqueous suspension solution of NH2-MIL-101(Fe).

[0018] A second aspect of the present invention provides a method for detecting zinc ions, comprising the steps of:

[0019] (1) measuring the fluorescence intensity value of the NH2-MIL-101(Fe) suspension containing curcumin as the third fluorescence intensity value;

[0020] (2) respectively detecting the fluorescence intensity values ​​of the NH2-MIL-101(Fe) suspension containing curcumin and different concentrations of zinc ions as the fourth fluorescence intensity value;

[0021] (3) taking the difference between the third fluorescence intensity value and the fourth fluorescence intensity value as the fluorescence intensity recovery amount;

[0022] (4) fitting to obtain the linear equation between different zinc ion concentrations and the fluorescence intensity recovery;

[0023] (5) Substituting the measured value of the fluorescence intensity recovery of the sample to be tested into the linear equation, the corresponding zinc ion concentration in the sample to be tested can be obtained.

[0024] The zinc ion detection method is based on the "OFF-ON" principle, which relies on curcumin first adsorbing and quenching the emission fluorescence of NH2-MIL-101(Fe), and different concentrations of zinc ions can restore the fluorescence quenched by curcumin to varying degrees. The linear relationship between zinc ion concentration and fluorescence intensity recovery is thus fitted, and the concentration of zinc ions in the sample is calculated based on this linear relationship.

[0025] Preferably, in steps (1) and (2), the final concentration of NH2-MIL-101(Fe) is 0.25-1.5 mg / mL, the final concentration of curcumin is selected from 10-100 μmol / L, and the solvent of the NH2-MIL-101(Fe) suspension is water and / or alcohol. The alcohol includes at least one of methanol, ethanol, propanol, and butanol.

[0026] Preferably, in step (2), the final concentration of the zinc ions is in the range of 0.01-1 μmol / L and / or 5-100 μmol / L.

[0027] Preferably, the preparation method of NH2-MIL-101(Fe) in the above method is: dissolving hydrated ferric chloride and 2-aminoterephthalic acid in an organic solvent, heating for reaction, collecting the precipitate by centrifugation after the reaction, washing and drying the precipitate with an organic solvent to obtain NH2-MIL-101(Fe).

[0028] Preferably, the heating condition is heating at 140-160° C. for 6-18 hours; the organic solvent includes at least one of DMF, DMSO, THF, and NMP; and the washing method is washing with an organic solvent and methanol alternately.

[0029] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0030] The detection method of curcumin and zinc ions based on NH2-MIL-101 (Fe) fluorescent probe is convenient and fast, with high accuracy and low detection limit, wherein the minimum detection limit of curcumin can reach 10nmol / L, and the minimum detection limit of zinc ions can reach 1.5nmol / L. The present invention has high selectivity, strong anti-interference ability, and strong practical detection application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 These are scanning electron microscopy and transmission electron microscopy images of the fluorescent probe NH2-MIL-101(Fe) in the examples of the present invention.

[0032] Figure 2 This is the fluorescence spectrum of the fluorescent probe NH2-MIL-101(Fe) in the embodiment of the present invention.

[0033] Figure 3 This is the infrared spectrum of the fluorescent probe NH2-MIL-101(Fe) before and after purification in the example of the present invention.

[0034] Figure 4 It is the linear equation for detecting curcumin by the fluorescent probe NH2-MIL-101 (Fe) in the implementation of the present invention; wherein, Figure a is the fluorescence spectrum of the system in the range of 0-100 μmol / L of final concentration of curcumin; Figure b is the linear fitting diagram in the range of 0-5 μmol / L of final concentration of curcumin; Figure c is the linear fitting diagram in the range of 10-100 μmol / L of final concentration of curcumin;

[0035] Figure 5 It is the linear equation for the fluorescent probe NH2-MIL-101 (Fe) to detect zinc ions in the implementation of the present invention; wherein, Figure a is the fluorescence spectrum of the system in the range of 0.01-100 μmol / L of final zinc ion concentration; Figure b is the linear fitting diagram in the range of 0.01-1 μmol / L of final zinc ion concentration; Figure c is the linear fitting diagram in the range of 5-100 μmol / L of final zinc ion concentration;

[0036] Figure 6 The results of the selective experiment of the fluorescent probe NH2-MIL-101 (Fe) for detecting curcumin in the implementation of the present invention are shown in FIG.

[0037] Figure 7 These are the selective experimental results of the fluorescent probe NH2-MIL-101(Fe) in detecting zinc ions in the implementation of the present invention. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0039] Example 1: Preparation and characterization of NH2-MIL-101(Fe)

[0040] Weigh 1.6g of ferric chloride monohydrate (FeCl3·H2O) and 1.4g of 2-aminoterephthalic acid (NH2-H2BDC), dissolve in 15mL N,N-dimethylformamide (DMF), transfer the resulting solution to a 100mL tetrafluoroethylene-lined autoclave, heat at 150℃ for 12 hours, centrifuge at 8000 rpm for 10 minutes, collect the brown product, wash it alternately with DMF and methanol for 3 times, and dry it at 60℃ to obtain a tan solid powder. In addition, part of the obtained powder was suspended in 100mL of methanol, stirred for 2 days to remove residual DMF, centrifuged at 8000 rpm for 10 minutes, and dried at 60℃ for 12h. Scanning electron microscopy, transmission electron microscopy, fluorescence spectroscopy, and infrared spectroscopy were used for characterization.

[0041] Figure 1 The scanning electron microscope and transmission electron microscope images of NH2-MIL-101(Fe) (inserted inset), it can be seen that the prepared NH2-MIL-101(Fe) presents a six-sided spindle with a width of about 2-3μm and a length of about 8-10μm;

[0042] Figure 2 The black and red lines in the middle represent the fluorescence spectra of the reactant NH2-H2BDC and the fluorescent probe NH2-MIL-101(Fe), respectively. When excited at 350nm, NH2-H2BDC emits light blue fluorescence with the strongest emission wavelength at 440nm, while NH2-MIL-101(Fe) emits blue fluorescence with the emission wavelength red-shifted to 450nm.

[0043] Figure 3 The infrared spectra of NH2-MIL-101(Fe) obtained by direct synthesis and NH2-MIL-101(Fe) purified by stirring in methanol for 2 days. 1600-1400cm -1 It is produced by OCO stretching vibration, 3456cm -1and 3373cm -1 Related to the stretching vibration of NH, 540 cm -1 、1337cm -1 They are related to Fe-O and CN in NH2-MIL-101(Fe), respectively. Compared with the directly synthesized product, the infrared spectrum of the purified probe has no obvious difference, which indicates that stirring in methanol for 2 days will not change the structure and stability of the fluorescent probe.

[0044] Example 2: The linear equation for quantitative detection of curcumin was obtained using NH2-MIL-101 (Fe) prepared in Example 1, as follows:

[0045] (1) Accurately weigh a certain amount of NH2-MIL-101(Fe) solid powder, disperse it in deionized water, ultrasonicate for 10 minutes, and dilute to obtain a 1.0 mg / mL NH2-MIL-101(Fe) suspension; accurately weigh a certain amount of curcumin, add anhydrous ethanol, ultrasonicate to dissolve it, and then dilute to obtain a 0.1 mol / L curcumin stock solution.

[0046] (2) exciting a 1.0 mg / mL NH2-MIL-101(Fe) suspension at 350 nm, and recording the fluorescence intensity value at an emission wavelength of 450 nm to obtain a first fluorescence intensity value;

[0047] (3) mixing the NH2-MIL-101(Fe) suspension with curcumin stock solutions of different concentrations to ensure that the final concentration of NH2-MIL-101(Fe) in the mixed solution is 0.8 mg / mL and the final concentration of curcumin is in the range of 0.1-100 μmol / L, shaking and placing for 5 min to obtain NH2-MIL-101(Fe) suspensions containing curcumin of different final concentrations, exciting at 350 nm, saving the fluorescence spectra at each concentration and recording the fluorescence intensity value at an emission wavelength of 450 nm to obtain a second fluorescence intensity value;

[0048] (3) taking the difference between the first fluorescence intensity value and the second fluorescence intensity value as the reduction amount of the excitation fluorescence intensity;

[0049] (4) With the curcumin concentration as the horizontal axis and the decrease in emission fluorescence intensity as the vertical axis, a linear equation between different curcumin concentrations and the decrease in emission fluorescence intensity was obtained by fitting, such as Figure 4 shown.

[0050] Figure 4Figure a shows that in the range of 0-100 μmol / L, as the concentration of curcumin increases, the fluorescence of the NH2-MIL-101(Fe) probe is gradually quenched, and this concentration range shows two linear relationships. In the low concentration range of 0.1-5 μmol / L, the fitted linear equation is y=575.299C 姜黄素 +756.698, R 2 =0.9955 (e.g. Figure 4 (as shown in Figure b); in the relatively high concentration range of 10 to 100 μmol / L, the fitted linear equation y = 20.079C 姜黄素 +3782.896, R 2 =0.9927 (e.g. Figure 4 (as shown in Figure c); the minimum detection limit is 10nmol / L. Where y is F0-F, F0 is the first fluorescence intensity value, and F is the second fluorescence intensity value.

[0051] Example 3: A linear equation for quantitative detection of zinc ions was obtained using NH2-MIL-101 (Fe) and curcumin prepared in Example 1, as follows:

[0052] (1) mixing the NH2-MIL-101(Fe) suspension with the curcumin stock solution to ensure that the final concentration of NH2-MIL-101(Fe) in the mixed solution is 0.8 mg / mL and the final concentration of curcumin is 50 μmol / L, shaking and placing for 5 minutes to obtain a NH2-MIL-101(Fe) suspension containing curcumin; exciting at 350 nm, and measuring the fluorescence intensity value of the NH2-MIL-101(Fe) suspension containing curcumin at an emission wavelength of 450 nm as a third fluorescence intensity value;

[0053] (2) Dissolve a soluble zinc salt in water to prepare zinc ion stock solutions of different concentrations. In this embodiment, zinc chloride (ZnCl2) of AR grade is used. Then mix the zinc ion stock solutions of different concentrations, NH2-MIL-101 (Fe) suspension and curcumin stock solution to ensure that the final concentration of NH2-MIL-101 (Fe) in the mixed solution is 0.8 mg / mL, the final concentration of curcumin is 50 μmol / L, and the final concentration of zinc ions is in the range of 0.01-100 μmol / L. After shaking, place for 30 minutes, excite at 350 nm, save the fluorescence spectra at each zinc ion concentration and record the fluorescence intensity value at an emission wavelength of 450 nm as the fourth fluorescence intensity value;

[0054] (3) taking the difference between the third fluorescence intensity value and the fourth fluorescence intensity value as the fluorescence intensity recovery amount;

[0055] (4) With the final zinc ion concentration as the horizontal axis and the fluorescence intensity recovery amount as the vertical axis, a linear equation between different zinc ion concentrations and the fluorescence intensity recovery amount was fitted; Figure 5 shown.

[0056] Depend on Figure 5 As shown in Figure a, within the range of 0.01-100 μmol / L, as the final concentration of zinc ions increases, the fluorescence of the NH2-MIL-101 (Fe) probe gradually recovers, and this concentration range shows two linear relationships. When the linear range is 0.01-1 μmol / L, the fitted linear equation y = 803.99C 锌离子 +63.197, R 2 =0.9954 (e.g. Figure 5 When the linear range is 5-100 μmol / L, the corresponding linear equation is y=35.244C 锌离子 +853.547, R 2 =0.9976 (e.g. Figure 5 (as shown in Figure c); the minimum detection limit is 1.5 nmol / L. Where y is F0-F, F0 is the third fluorescence intensity value, and F is the fourth fluorescence intensity value.

[0057] Example 4: Anti-interference experiment of curcumin detection

[0058] A certain amount of ascorbic acid (AA), glutamic acid (Glu), glycine (Gly), tyrosine (Tyr), aspartic acid (Asp), arginine (Arg), leucine (Leu), methionine (Met), and valine (Val) were weighed respectively and prepared into solutions with deionized water.

[0059] The NH2-MIL-101(Fe) suspension was divided into two portions in centrifuge tubes, each with 10 tubes. Anhydrous ethanol solution of curcumin was added to one portion to ensure that the final concentration of NH2-MIL-101(Fe) was 0.8 mg / mL and the final concentration of curcumin was 50 μmol / L. Anhydrous ethanol was added to the other portion to ensure that the final concentration of NH2-MIL-101(Fe) was 0.8 mg / mL. The above-mentioned nine proposed interfering substance solutions were added to the two portions of NH2-MIL-101(Fe) suspension respectively to ensure that the final concentration of each interfering substance was 100 μmol / L. After shaking, they were placed for 5 minutes. Excited at 350 nm, recorded the fluorescence intensity value of each group at 450 nm, and used origin software to draw a bar graph. The results are as follows. Figure 6 As shown in the figure, in the presence of the above 9 proposed interfering substances, there was no obvious effect on the detection of curcumin, indicating that this method has good selectivity for the detection of curcumin.

[0060] Example 5: Anti-interference experiment of zinc ion detection

[0061] Weigh a certain amount of metal ions (Ag + , Ca 2+ Mg 2+ , Cu 2+ , Mn 2+ , Pb 2+ 、Cd 2+ , Hg 2+ , Fe 3+ ), and prepare the solution with deionized water.

[0062] The NH2-MIL-101(Fe) suspension and curcumin stock solution were mixed and dispensed into centrifuge tubes, divided into 2 portions, 10 tubes each, one of which was added with ZnCl2 stock solution to ensure that the final concentrations of NH2-MIL-101(Fe) were 0.8 mg / mL, the final concentrations of curcumin were 50 μmol / L, and the final concentrations of ZnCl2 were 1.5 μmol / L. 2+ The final concentration was 50 μmol / L. Deionized water was added to the other portion without adding ZnCl2 stock solution to ensure that the final concentration of NH2-MIL-101(Fe) was 0.8 mg / mL and the final concentration of curcumin was 50 μmol / L.

[0063] The above nine interfering substance solutions were added to two NH2-MIL-101(Fe) suspensions containing curcumin, respectively, to ensure that the final concentration of each interfering substance was 100 μmol / L, and then shaken and left for 5 minutes. Excited at 350 nm, recorded the fluorescence intensity value of each group at 450 nm, and plotted a bar graph using origin software. The results are shown in Figure 2. Figure 7 It shows that the presence of other metal ions has no effect on Zn 2+ The detection produced obvious interference, indicating that this method is not suitable for Zn 2+ The detection has good selectivity.

[0064] Example 6: Practical application of detecting curcumin

[0065] Commercially available instant noodles, ginger powder and red pepper powder are dried and ground into fine powder. 10 mg of solid powder is weighed respectively, 10 mL of anhydrous ethanol is added, ultrasonicated for 20 minutes, centrifuged at 8000 rpm for 10 minutes, and the supernatant is collected and filtered through a 0.45 μm microporous filter membrane. 150 μL of NH2-MIL-101 (Fe) suspension is accurately drawn, and 50 μL of instant flour, ginger powder and red pepper powder ethanol solution are added respectively, and the mixture is placed for 5 min after shaking to ensure that the final concentration of NH2-MIL-101 (Fe) in the mixed solution is 0.8 mg / mL, excited at 350 nm, and the fluorescence intensity value of the emission wavelength of 450 nm is recorded, and the curcumin linear equation fitted in Example 2 is substituted to calculate the curcumin content in the sample. Then, the standard addition method was used to add curcumin standard solution (final concentration 1, 5, 10 μmol / L) to the sample ethanol solution, respectively, and the fluorescence intensity value at the emission wavelength of 450 nm was recorded. The curcumin linear equation was substituted into the fitted one to calculate the total content of curcumin in the sample and the recovery rate of spiked addition. The results are shown in Table 1.

[0066] Table 1 NH2-MIL-101 (Fe) detection of curcumin in actual samples and the results of spike recovery experiments

[0067]

[0068] Example 7: Practical application of detecting zinc ions

[0069] Accurately draw 150 μ L NH2-MIL-101 (Fe) suspension, add 50 μ L curcumin ethanol solution, ensure that NH2-MIL-101 (Fe) final concentration is 0.8mg / mL in mixed solution, curcumin final concentration is 50 μ mol / L, place 5min after shaking, add 50 μ L Jinghu water sample and tap water sample respectively, place 30min after shaking, excite at 350nm, record the fluorescence intensity value of emission wavelength 450nm, substitute into the zinc ion linear equation of fitting in embodiment 3, calculate zinc ion content in sample.Then adopt standard addition method, add zinc ion standard solution (final concentration 0.05, 5.85, 12.25 μ mol / L) respectively in water sample, excite at 350nm, record the fluorescence intensity value of emission wavelength 450nm, substitute into the zinc ion linear equation of fitting, calculate zinc ion total content and spiked recovery in sample, result is as shown in table 2.

[0070] Table 2 Application of NH2-MIL-101(Fe) in detecting zinc ions in actual samples and results of spike recovery experiments

[0071]

Claims

1. A method for detecting zinc ions, characterized in that, The steps include: (1) measuring the fluorescence intensity value of the NH2-MIL-101 (Fe) suspension containing curcumin as the third fluorescence intensity value; (2) respectively detecting the fluorescence intensity values ​​of the NH2-MIL-101 (Fe) suspension containing curcumin and different concentrations of zinc ions as the fourth fluorescence intensity value; (3) taking the difference between the third fluorescence intensity value and the fourth fluorescence intensity value as the fluorescence intensity recovery amount; (4) The linear equation between different zinc ion concentrations and the fluorescence intensity recovery was obtained by fitting; (5) Substituting the measured value of the fluorescence intensity recovery of the sample to be tested into the linear equation, the corresponding zinc ion concentration in the sample to be tested can be obtained.

2. The method for detecting zinc ions according to claim 1, wherein In steps (1) and (2), the final concentration of NH2-MIL-101 (Fe) is 0.25-1.5 mg / mL, the final concentration of curcumin is selected from 10-100 μmol / L, and the solvent of the NH2-MIL-101 (Fe) suspension is water and / or alcohol.

3. The method for detecting zinc ions according to claim 1, wherein In step (2), the final concentration of the zinc ion is in the range of 0.01-1 μmol / L and / or 5-100 μmol / L.

4. The method according to any one of claims 1 to 3, characterized in that: The preparation method of NH2-MIL-101 (Fe) is as follows: dissolving hydrated ferric chloride and 2-aminoterephthalic acid in an organic solvent, heating for reaction, collecting precipitates by centrifugation after the reaction, washing and drying the precipitates with an organic solvent to obtain NH2-MIL-101 (Fe).

5. The method according to claim 4, characterized in that The heating condition is heating at 140-160° C. for 6-18 hours; the organic solvent includes at least one of DMF, DMSO, THF, and NMP; and the washing method is washing with an organic solvent and methanol alternately.

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