Rapid Detection of F Ions in Food Using Cholesteric Chiral Molecular Tweezers

Abstract

The present invention provides a method for detecting F ions in food, which comprises adding compound 7d to a sample to be tested and performing quantitative or qualitative detection using ultraviolet-visible spectroscopy or fluorescence spectroscopy, or performing qualitative detection by distinguishing color changes.

Description

Technical Field

[0001] The present invention relates to the field of detection. Background Art

[0002] As we all know, anions are widely present in our daily lives, especially in biological processes, environmental testing, and clinical medicine. At present, researchers are committed to designing and synthesizing a series of anion receptor compounds and applying them to the selective recognition and detection of specific anions. Among various anions, fluoride ions are increasingly attracting widespread attention due to their special role in living organisms. Fluorine is one of the indispensable trace elements for human growth and development, and plays a pivotal role in preventing dental caries and treating osteoporosis. Therefore, trace amounts of fluoride are widely used as additives in toothpaste and water to achieve the purpose of strengthening bones and protecting teeth. However, at the same time, fluoride is also a cumulative toxic substance. Once the human body ingests excessive fluoride ions, it may induce cell apoptosis, resulting in decreased immune function of the body, and even cause damage to tissues and organs such as bones, heart, and kidneys, which greatly endangers human health. According to the World Health Organization, the limit of fluoride ion content in daily drinking water is 1.5 mg / L. Among them, the current fluoride ion concentration in my country's drinking water hygiene standard shall not exceed 1.0 mg / L to prevent poisoning caused by fluoride ions. Therefore, how to efficiently detect fluoride ions is of great significance to human health and the chemical environment.

[0003] In recent years, there are many traditional detection methods for identifying fluoride ions, including gas chromatography, ion selective electrode method, 19 F-NMR analysis and high performance liquid chromatography are the main methods for fluoride ion detection. However, in addition to relying on large precision instruments and professional operating technicians, these methods are also very cumbersome for sample pretreatment, which seriously hinders their practicality. Therefore, it is very necessary to develop a new, highly sensitive and highly selective fluoride ion detection method. At present, a large number of studies have reported that photochemical response recognition technology can more efficiently and quickly promote the selectivity between the guest and the receptor, thereby realizing the qualitative and quantitative detection of specific ions. Usually in the recognition system of anions, various types of compounds such as amides, thioureas, pyridines, indoles, etc. are considered to be good ligands and show high sensitivity and selectivity. In addition, cholesteric compounds have aroused great interest among researchers due to their simple preparation, mild reaction, flexible and multifunctional recognition sites in their structure, and different types of anion recognition receptors can be designed by modifying the hydroxyl and carboxyl groups in the steroid skeleton. Among them, Liu Xingli et al. used deoxycholic acid as an isolation base and designed and synthesized two new clamp-shaped anion artificial receptors under microwave radiation for the first time. It was found that this type of compound binds to the guest anion F- , Cl - Br - ,I - ,Ac - 、H2PO4 - Both have recognition ability, and the host and the guest form a 1:1 supramolecular complex through multiple hydrogen bonds. Mamra Chahar et al. modified the cholesteric biimidazole derivatives by ring closure and synthesized a new type of deoxycholic acid cyclic receptor. When naphthalene is used as the spacer, the receptor recognizes F with high sensitivity and selectivity. - ion. Summary of the invention

[0004] The invention uses deoxycholic acid as a raw material and combines microwave radiation technology to synthesize a cholesteric target molecular tweezers artificial receptor 7d through a series of chemical reactions, obtains the recognition performance of the receptor to anions through ultraviolet and fluorescence spectral analysis, and infers the possible recognition mechanism by using nuclear magnetic titration and molecular simulation, establishes a method for rapid quantitative detection of fluoride ions by chiral molecular tweezers, and applies it to the detection of F ions in food samples, in order to open up a new method for rapid detection of specific anions for this type of compound in the field of food science.

[0005] Specifically, the present invention provides a method for detecting F ions in food, which comprises adding compound 7d to a sample to be tested and performing quantitative or qualitative detection using ultraviolet-visible spectroscopy or fluorescence spectroscopy, or performing qualitative detection by distinguishing color changes; the structural formula of compound 7d is as follows:

[0006]

[0007] In the fluorescence detection, 270 nm was used as the emission wavelength and the fluorescence intensity was measured at a wavelength of 273 nm.

[0008] Wherein, in the UV-visible spectrum detection, detection is performed at a wavelength of 255nm, 288nm or / and 350nm.

[0009] Among them, the detection limit of F ions is 5.14μmol / L.

[0010] Among them, the pre-test treatment method includes: taking the sample to be tested, nitrifying it in a digestion tube at 400°C for 55 minutes, and taking the supernatant as the sample solution to be tested.

[0011] If quantitative detection is required in the present invention, the F ion content is determined by the standard curve method.

[0012] It is also possible to perform qualitative detection by distinguishing color changes. When 7d compound is added to the sample solution to be tested, when the solution turns yellow, it indicates that the sample to be tested contains F ions. This method is very convenient and quick. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 .(A) Chiral molecular tweezer 7d (20 μmol / L) in different anions (1×10 -3 mol / L); (B) UV-visible absorption spectra of chiral molecular tweezer 7d (20 μmol / L) in the presence of different anions (1×10 -3 mol / L); (C) Fluorescence emission spectra of chiral molecular tweezer 7d (20 μmol / L) in the presence of different anions (1×10 -3 mol / L) in the presence of

[0014] Figure 2 Chiral molecular tweezers 7d (20μmol / L) added dropwise F - With other anions (8.33×10 -4 mol / L) at 288nm absorbance value change bar graph

[0015] Figure 3 .(A) Chiral molecular tweezer 7d(5.0×10 -4 mol / L) and different concentrations of F - (0~192μmol / L) UV-visible spectroscopic titration; (B) Chiral molecular tweezers 7d (5.0×10 -4 mol / L) and different concentrations of F - Benesi-Hildebrand linear fitting; (C) Chiral molecular tweezer 7d (5.0×10 -4 mol / L) was gradually added with F - (D) Chiral molecular tweezers 7d and F - Job diagram of the action system

[0016] Figure 4 .(A) The main compound 7d in the absence of F - FESEM images under F conditions (×180, 3kw). (B) Main compound 7d under F - FESEM images (×10,000, 5 kW) of the main compound 7d in the presence of F - FESEM images (×10,000, 15 kW) of the main compound 7d in the presence of F - Energy spectrum image in the presence of (×10,000, 15 kW).

[0017] Figure 5 . Main molecular clamp 7d and complex 7d-F - The optimal structure and frontier molecular orbital HOMO-LUMO energy difference

[0018] Figure 6 . Main molecular clamp 7d and F - Possible mode of action DETAILED DESCRIPTION

[0019] Example 1

[0020] 1 Experimental part

[0021] 1.1 Instruments and reagents

[0022] Tetrabutylammonium fluoride, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide, tetrabutylammonium hydrogen sulfate, tetrabutylammonium nitrate, tetrabutylammonium dihydrogen phosphate, tetrabutylammonium acetate: Shanghai Dingfen Chemical Technology Co., Ltd.; deoxycholic acid, o-methoxybenzoic acid, triphosgene (≥99%): Shanghai Aladdin Biochemical Technology Co., Ltd.; dichloromethane, ethyl acetate: Tianjin Fuyu Fine Chemical Co., Ltd.; acetone: Guangzhou Jiangshun Chemical Technology Co., Ltd.; anhydrous sodium sulfate: Tianjin Damao Chemical Reagent Factory; pyridine (≥99%): Shanghai Jianxin Chemical Co., Ltd. Reagent Factory; hydrazine hydrate: Guangdong Guanghua Technology Co., Ltd.; deuterated DMSO: Merck Chemical Reagent Co., Ltd.; dimethyl sulfoxide (DMSO), methanol, ethanol, concentrated hydrochloric acid: Tianjin Fuyu Fine Chemical Co., Ltd.

[0023] The UV absorption spectra were measured using a UV-2600 UV-visible spectrophotometer (Shimadzu Instruments Co., Ltd., Japan); the chemical reactions were carried out using an MCR-3 microwave chemical reactor (Zhengzhou Taiyuan Instruments Co., Ltd.); the nuclear magnetic resonance spectra were recorded using an AVANCE NEO nuclear magnetic resonance spectrometer (Bruker, Germany); and the microscopic images were observed using a JSM-7900F field emission scanning electron microscope (JEOL Ltd.);

[0024] 1.2 Synthesis of cholesteric molecular tweezer fluorescent probe

[0025] Deoxycholic acid was used as the raw material, and deoxycholic acid methyl ester was prepared by methyl esterification under the action of concentrated sulfuric acid as a catalyst; L-methionine was used as the raw material, methanol and SOCl2 were added, and L-methionine methyl ester hydrochloride was prepared by heating and reflux reaction. Finally, deoxycholic acid methyl ester was used as the spacer, aryl hydrazine and amino acid were used as arms, and microwave synthesis was used. The column chromatography method was used for separation and purification to prepare the cholesteric chiral molecular tweezer artificial receptor 7d. White crystals, the mass spectrum, hydrogen spectrum, carbon spectrum and other data of the target product are consistent with those reported in the literature. The synthesis route is shown in Scheme 1.

[0026]

[0027] 1.3 Solution preparation and spectral analysis

[0028] Prepare the DMSO solution of the host molecular tweezers 7d at room temperature (2×10 -4 mol·L -1 ), 0.01 mol·L -1 Different types of anions (F - , Cl - Br - ,I - 、HSO4 - 、NO3 - 、H2PO4 - ,Ac - )DMSO solution, at room temperature, add a certain amount of different anions to the prepared molecular tweezers solution, and perform UV-visible absorption and fluorescence spectra measurements (selectivity, interference, UV titration, Job curve).

[0029] The sample pool for fluorescence spectrum measurement is a 1cm×1cm×4cm quartz cuvette, with an excitation slit width of 5.0nm, an emission slit width of 5.0nm, an excitation wavelength λ of 270nm, a sensitivity of 1, and fluorescence is detected in the range of 200 to 600nm. Similarly, a 1cm×1cm×4cm ultraviolet spectrophotometer quartz cuvette is used to detect changes in the ultraviolet absorption spectrum in the range of 200 to 400nm.

[0030] 1.4 Selective recognition of anions by the host molecular tweezer 7d

[0031] Take 0.5mL of 2×10 -4 mol·L -1 The main molecular tweezers were added for 7 days, and 0.5 mL of various anion solutions (F - , Cl - Br - ,I - 、HSO4 - 、NO3 - 、H2PO4 - ,Ac - ), dilute to 5 mL, and observe the changes in solution color, fluorescence emission spectrum, and UV-visible absorption spectrum.

[0032] 1.5 Specific recognition of coexisting ion pairs by F - Research on the interference capability of

[0033] Main molecular tweezers 7d (20 μmol·L -1 ) solution was added with 50 times the amount of F - and other anions, and tested the UV-visible absorption spectrum of the mixed solution at 288 nm.

[0034] 1.6 Main molecular clamp 7d recognizes F - UV titration and Job test

[0035] At a concentration of 5.0×10 -4 mol / L of the main molecular tweezers 7d solution was gradually added with F - (16~192μmol / L), determination of different F - The UV-visible absorption spectra of the complex solutions of each group at different concentrations were used to calculate the absorbance of the complex at 288 nm. - The complex constant of F - The concentration was plotted against the UV-visible absorbance value to obtain the standard curve equation, and then the molecular clamp 7d to F was calculated according to the formula LOD = 3σ / k. - where σ is the standard deviation and k is the slope of the linear fit.

[0036] Always keep subject and object F - The total concentration is 1×10 -5 mol / L, prepare the main molecular tweezers 7d and F - A series of mixed solutions with molar ratios of 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2 and 9:1 were measured for their absorbance values, and the Job dot diagram of the complex was obtained to determine the complex ratio of the complex.

[0037] 1.7 Microstructure observation and energy spectrum imaging study of the complex

[0038] In order to more intuitively observe the main molecular clamp 7d and F - The interaction between the main molecular clamp 7d and its interaction with F - The complexes were observed for microstructure and analyzed by energy spectrum imaging using field emission scanning electron microscopy (FESEM).

[0039] 1.8 Main molecular clamp 7d recognizes F - Study on the mechanism of action

[0040] Molecular tweezers 7d and F were quantitatively added according to the composition ratio of the complex - , observe the main molecular clamp 7d join F - back 1 The changes in the H spectrum can be used to determine the molecular tweezers 7d and F by changing the chemical shift of hydrogen protons on different functional groups. - The binding site and possible driving force of recognition were calculated using Gaussian 09 software, and density functional theory (DFT) optimization calculations were performed at the B3LYP / 6-31G(d) level to study the structure of the main molecular clamp 7d and the main molecular clamp 7d and F- Simulation of the molecular structure.

[0041] 1.9 F in actual food - Detection

[0042] Weigh 4g of Ribes angustifolia, quinoa, oats, flour, and wolfberry into a nitration tube, add 0.2g of copper sulfate, 6g of potassium sulfate, and 10mL of sulfuric acid, digest at 400℃ for 55min, and centrifuge to obtain the supernatant. Take 0.5mL of the main molecular tweezers and add them to 0.5mL of the sample solution, dilute to 5mL, and measure the absorbance of the sample using a UV-spectrophotometer.

[0043] 2 Results and discussion

[0044] 2.1 Selective recognition of anions by the host molecular tweezer 7d

[0045] like Figure 1 As shown in A, when various other anions are added to the main molecular tweezers solution, only F - The UV-visible absorption spectrum of the main molecular tweezer 7d has changed significantly. The absorption peak intensities at 255nm and 288nm have been significantly reduced, and a new absorption peak has been generated at 350nm. However, the addition of other anions has not caused any significant changes. In addition, it is worth noting that the chiral molecular tweezer 7d and F - After the reaction, the solution changed from colorless to obvious yellow, while other anions did not cause color change ( Figure 1 C) This may be because the chiral molecular clamp 7d and F - The complex was formed, which promoted the color change of the solution, indicating that the main molecular tweezer 7d can achieve the specific recognition of F by the naked eye. - To further investigate the selective recognition of anions by chiral molecular tweezers 7d, fluorescence spectroscopy was used to investigate the emission properties of the above anions under the same conditions. Figure 1 As shown in B, with the addition of various anions, only F - The chiral molecular tweezer 7d showed the highest fluorescence intensity at 273nm, while the addition of other ions did not cause obvious changes in the fluorescence spectrum. The reason may be that the complex formed by the chiral molecular tweezer 7d and the fluoride ion is more rigid than before the binding, thus showing fluorescence enhancement. In summary, based on the above two recognition results, it is shown that the main body 7d and F - It produces better selectivity and can achieve highly selective identification.

[0046] 2.2 Study on the influence of coexisting ions on the interference ability of specific recognition

[0047] In order to further evaluate the main molecular clamp 7d in complex environment- The selectivity of the main molecular tweezer 7d was studied in the presence of various other anions in dimethyl sulfoxide solution. Figure 2 As shown, when the main molecular clamp 7d and F - When other competitive anions were added to the coordinated system, the UV absorbance value of the characteristic absorption peak at 288 nm was almost unchanged from that when other anions were added, and the relative error was less than 10% (Table 1), indicating that other coexisting anions interfered with the recognition of F by the main molecular tweezer 7d. - The detection process was slightly affected, further indicating that the main molecular tweezer 7d selectively recognized F - It shows good anti-interference performance and has wide environmental adaptability and practicality.

[0048] Table 1 Interfering ions for the recognition of F by the main molecular tweezers 7d - Impact

[0049]

[0050] 2.3 Effects of the main molecular clamp 7d on different concentrations of F - UV titration test

[0051] In order to further understand and verify the main molecular clamp 7d and F - The relationship between the two - UV spectrophotometric titration test was carried out. Figure 3 A knows that F is not added - When F - The addition of the main molecular clamp 7d and F - The interaction caused the characteristic absorption peak at 288nm to show a regular weakening trend, and a new absorption peak appeared at 350nm. - The concentration of ions gradually increases with the increase of ion concentration, indicating that the host-guest complex is formed during the titration process. -5 ~1.92×10 -4 In the range of mol / L, according to the Hildebrand-Benes equation, 1 / [G0] was plotted against 1 / ΔA, and a good straight line (R 2 =0.997), such as Figure 3 As shown in B, it shows that the main molecular clamp 7d and F - A 1:1 complex was formed between the two groups. According to the intercept 1 / a and the slope 1 / a·Ka of the straight line, the binding constant Ka of the complex was calculated to be 1719 L / mol. - Concentration versus UV-visible absorbance ( Figure 3 C), it can be seen that the absorbance value of chiral molecular tweezer 7d is similar to F - The concentration has a good linear relationship in the range of 16 to 192 μmol / L. The standard curve at 288 nm is y = -0.006x + 1.519 after fitting, and the correlation coefficient is 0.997. According to the calculation formula LOD = 3σ / k, where σ is the standard deviation and k is the slope of the standard curve, the main molecular clamp 7d has a good linear relationship with F - The detection limit of F in drinking water was 5.14 μmol / L, which is much lower than the limit set by the U.S. Environmental Protection Agency (EPA). - Standard (210μM). - Compared with the sensors (Table 2), the main molecular clamp 7d has a strong affinity for F - The recognition sensitivity is higher, and the detection system is intuitive and rapid, without the need for complex processes and expensive instruments. Therefore, it is shown that chiral molecular tweezers 7d can be used for F in this concentration range. - Rapid detection.

[0052] In order to determine the main molecular clamp 7d and F - The molar ratio between 7d and 7d+F is another effective method. - When the molar ratio is 0.5, the obtained 7d+F - The concentration of the complex is the largest, which indicates that the chiral molecular tweezer 7d and F - It is a complex coordination with a 1:1 molar ratio.

[0053] Table 2.

[0054]

[0055]

[0056] 2.4 Microstructure observation and energy spectrum imaging analysis of the complex

[0057] Host molecular clamp 7d and F - Field emission scanning electron microscopy of the formed complex Figure 4 As shown in the figure, without adding F - Ion time ( Figure 4 A), the main compound 7d is mainly accumulated in a dense block form. When combined with anion F - After complexation ( Figure 4 B), the structure of the main molecular clamp 7d changed significantly, forming a regular wrinkled network structure, and the raised part showed cavity striping, which -To further verify that the fluoride ions are encapsulated in the image, a scanning electron microscope image of the sample was taken at an accelerating voltage of 15.0 kV using a JSM 7900F high-resolution transmission scanning electron microscope ( Figure 4 C) and the corresponding energy spectrum imaging diagram ( Figure 4 D) Figure 4 As shown in C, when the main molecular clamp 7d and F - After the action, a large number of fluoride ions enter the cavity of the molecular tweezers 7d, showing a bright strip in the image. After analyzing the energy spectrum imaging, Figure 4 The green part in D is F - As can be seen from the figure, most of the fluoride ions are successfully embedded in the cracks and are encapsulated by the main compound 7d to form a stable complex.

[0058] 2.5 Identification Mechanism

[0059] It is difficult to accurately describe the chiral compounds 7d and F only by UV titration and naked eye identification test. - The recognition mechanism of chiral molecular tweezers 7d can usually be explained more intuitively by using the signal changes of active hydrogen in the nuclear magnetic resonance hydrogen spectrum and the significant fluctuations of chemical shift. Therefore, in order to study the mechanism of action of chiral compound 7d with anionic fluorine in detail, we determined the reaction of chiral molecular tweezers 7d with F in deuterated dimethyl sulfoxide. - Before and After 1 H NMR changes.

[0060] From the NMR data, it can be seen that without adding F - When 1.0 equiv of F was added to the chiral molecular tweezer 7d, two clear signal peaks were shown at 9.70 and 9.09 ppm, which were considered to be the amide NH connected to the 3α-site of the benzene ring and deoxycholic acid methyl ester. In addition, a triplet sharp signal appeared at 7.64 ppm, which belonged to the amide NH on the 12α-site of deoxycholic acid methyl ester and the CH on the benzene ring. - After that, the signal peak of the NH proton of the amide group connected to the benzene ring disappeared, and the NH proton peak of the amide group connected to the 3α part of deoxycholic acid methyl ester moved to the high field to 9.33ppm (△δ=0.24), and the signal peak became significantly broadened and weakened, while the peak shape at 7.64ppm changed significantly, from the original triplet to a doublet at 7.67ppm and a singlet at 7.57ppm. This may be due to the active hydrogen in the main molecular tweezer 7d and the high electronegativity F - Formation of hydrogen bonds (NH…F -) effect, which causes the charge on the benzene ring to increase, indirectly leading to changes in the signal of the aromatic ring hydrogen. It can be seen that the two amide NH on the chiral molecular tweezer 7d binds to the fluoride ion, causing the optical properties to change, thus achieving the purpose of detecting the fluoride ion.

[0061] 2.5 Theoretical calculation

[0062] In order to further explain the binding mechanism between the main molecular tweezer 7d and the anion, the Gaussian09 quantum chemistry software was used to analyze the binding of the main molecular tweezer 7d and F using the DFT / B3LYP / 6-311G method. - Before and after effect In combination with F - After that, NH becomes significantly longer H…F - Distance is N—H…F - The angle is 174.3°, indicating that F - It forms a strong intermolecular hydrogen bond with the main molecular tweezer 7d, which is consistent with the change of active hydrogen in NMR titration. In addition, the HOMO-LUMO orbital energy level difference between the main molecular tweezer 7d and the complex 7d-F decreases from 5.14eV to 4.71eV, indicating that the main molecular tweezer 7d and F - The interaction effectively improves the stability of the complex.

[0063] 2.5 F in actual samples - Quantitative detection of

[0064] Based on the above mechanism exploration, it is shown that the chiral molecular tweezer compound 7d has a good response to fluoride ions. In order to verify the detection ability of chiral molecular tweezer 7d in actual samples, five different food samples were randomly selected and the F - The results are shown in Table 3. The F content of quinoa, Ribes angustifolia, wolfberry, milk powder and wheat flour detected by molecular tweezers at 7d - The contents were 2.44, 4.68, 2.57, 2.23, and 1.77 mg / kg, respectively. In addition, based on the above results, two food samples were randomly selected and tested for their F - The recovery rate test was carried out by adding different concentrations of F -The standard solution (2mg / kg, 5mg / kg) was used to measure its ultraviolet absorbance value. The results are shown in Table 4. The recovery rate was in the range of 97%-106%, and the relative standard deviation was in the range of 0.38%-4.59%. At the same time, it was compared with the fluoride ion selective electrode method in the national standard GB / T5009.18 "Determination of fluoride in food". The relative error value of the test results of this test and the fluoride ion selective electrode method was less than 5% (n=3), proving that this method can accurately and quantitatively (16-192μmol / L) detect F in food samples. - , which has high potential value in real life.

[0065] Table 3. F in food samples - Comparison between the new method and the selective electrode method (n=3)

[0066]

[0067]

[0068] Table 4. F in spiked food samples - Determination of recovery rate (n=3)

[0069]

[0070] 3 Conclusion

[0071] In summary, this paper used deoxycholic acid to synthesize chiral molecular tweezers 7d. UV spectrophotometry showed that molecular tweezers 7d - With selective recognition ability, adding F - It can cause the UV spectrum of the molecular tweezer 7d to show regular changes, and other anions recognize F - Almost no interference occurs, molecular tweezers 7d to F - It has high sensitivity and selectivity, and its binding constant is 1.72×10 4 L / mol, the detection limit is 5.14μmol / L, which is higher than many reported methods. - The addition of fluoride can change the color of the molecular tweezers 7d solution from colorless to yellow, while the color of the solution does not change when other anions are added. Based on this, we can achieve rapid naked eye detection of fluoride ions. In addition, we further determined the molecular tweezers 7d and F using the Job experiment method. - The cooperation between 7d and F - In order to further clarify the molecular clamp 7d and F - The recognition mechanism of molecular tweezers 7d and F - The NMR spectra and microstructural changes before and after coordination revealed that F- It can enter the cleavage of molecular clamp 7d well to form a stable complex. 12α-CONH and -PhCONH in the main molecular clamp 7d are the main binding sites. Fluoride ions form intermolecular hydrogen bonds with hydrogen atoms in amide NH to achieve the purpose of recognition. Further application of molecular clamp 7d to F in actual food samples - Through the detection of F in food samples such as quinoa, Ribes angustifolia, wolfberry, milk powder, and wheat flour, - A method for the determination of F in actual samples was established. - Compared with other reported methods, this method is fast, efficient, requires low-cost instruments and equipment, is easy to operate, and has good detection performance. - The method has high selectivity and is reliable, so it is expected to develop F - Rapid test kits are used for fluoride ion detection in food, environment and other fields.

[0072] In a specific embodiment of the present invention, the fluoride ion concentration is used as the horizontal coordinate and the ultraviolet absorbance value of the complex solution is used as the vertical coordinate to establish a standard curve of the fluoride ion concentration gradient. 0.5 mL of the main molecular tweezer solution is added to 0.5 mL of the pre-treated sample solution, and the volume is fixed to 5 mL. 2.5 mL of the mixed solution is taken into one of the cuvettes, and 2.5 mL of DMSO is added to the other cuvette as a reference solution. The absorbance value of the sample at 288 nm is measured by a UV-spectrophotometer at room temperature (25°C). According to the standard curve y=-0.006x+1.519 in the range of 16 to 192 μmol / L, the F - content.

Claims

1. A method for detecting F ions in food, characterized in that: The method comprises adding compound 7d to a sample to be tested and then using ultraviolet-visible spectroscopy for quantitative or qualitative detection, or performing qualitative detection by distinguishing color changes or fluorescence spectroscopy; the structural formula of compound 7d is as follows: 。 2. The method according to claim 1, characterized in that: In fluorescence detection, the emission wavelength was 270 nm and the fluorescence intensity was measured at 273 nm.

3. The method according to claim 1, characterized in that: In UV-visible spectroscopy, qualitative detection is performed at a wavelength of 255 nm or 350 nm, and quantitative or qualitative detection is performed at a wavelength of 288 nm.

4. The method according to claim 1, characterized in that: The detection limit of F ion was 5.14 μmol / L.

5. The method according to claim 1, characterized in that: The pre-test treatment method includes: taking the sample to be tested, nitrifying it in a digestion tube at 400°C for 55 min, and taking the supernatant as the sample solution to be tested.

6. The method according to claim 1 or 2, characterized in that: The F ion content was determined by the standard curve method.

7. The method according to claim 1, characterized in that: When qualitative detection is performed by distinguishing color changes, 7d compound is added to the sample solution to be tested. When the solution turns yellow, it indicates that the sample to be tested contains F ions.

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