Polarity response type fluorescent probe with anti-solvation effect as well as preparation method and application of polarity response type fluorescent probe

Abstract

The invention belongs to the field of rapid detection of the content of polar components in frying oil, and particularly relates to a polar response type fluorescent probe with an anti-solvation effect as well as a preparation method and application of the polar response type fluorescent probe. The fluorescent probe has a structure as shown in a formula I: # imgabs0 #, wherein n is 1-3. The emission wavelength of the probe reaches up to 720 nm and 830 nm, interference of background fluorescence in edible oil can be effectively avoided, and the probe has high anti-interference capacity. Good correlation exists between the fluorescence intensity and the polar component content of the soybean oil, and the polar component content is determined through a linear equation by utilizing the fluorescence intensity change of the probe in the edible oil under different polar component contents, so that the aim of quickly, sensitively and accurately detecting the polar component of the edible oil is fulfilled.

Description

Technical Field

[0001] The invention relates to the field of rapid detection of polar component content in frying oil, and in particular to a polarity-responsive fluorescent probe of antisolvation effect and a preparation method and application thereof. Background Art

[0002] The total polar fraction (TPM) of edible oil is a series of compounds with greater polarity than TGA itself produced by oxidation, polymerization and hydrolysis of triglycerides (TGA) during continuous frying. During the frying process, TPM will penetrate into the food with the oil. As the food is ingested by consumers, it will have potential harmful effects on human health, such as cardiovascular and cerebrovascular diseases, diabetes and cancer. It can be used as an important indicator for discarding frying oil. According to the national standard (GB 2716-2018), the limit in my country is 27%, and oil exceeding this limit needs to be discarded. The widely accepted analytical method is silica gel column chromatography (GB5009.202-2016), which can effectively and reliably detect TPM values. However, the test experiment of this method requires professional equipment, laboratories and professionals, especially the test time usually takes 1 to 3 days. In recent years, the fast food industry has flourished, and the rapid and accurate detection of TPM values ​​can help companies and regulators effectively manage oil changes, thereby controlling costs and ensuring the quality of fried foods.

[0003] Fluorescent probe technology has important significance and value in scientific research and practical applications due to its high sensitivity, real-time monitoring capability, non-destructiveness and wide application fields. The environmental characteristics of frying oil will change with the increase of TPM content (such as increased polarity, increased viscosity, etc.). Based on this, some fluorescent probes have begun to appear to detect TPM content. At 22.8°C, the viscosity of 29.3% TPM soybean oil is 150cP, which is about 65cP larger than that of 0.1% TPM, and when the temperature rises from 25°C to 35°C, the viscosity decreases by about 20cP. The temperature of edible oil will significantly affect the accuracy of viscosity-responsive probes. In addition, most polarity-responsive probes are "quenching" type, that is, the fluorescence of the probe is quenched with the increase of polarity, showing a typical solvation effect. This type of probe may be competitively quenched by other chemicals or molecules in the complex environment of edible oil, resulting in interference or misinterpretation of the signal. Some fluorescent probes with polarity-responsive "off-on" characteristics that have been reported are usually charged and difficult to dissolve in edible oil. Previous research by our research group, such as application number CN114478316A, disclosed a fluorescent probe and detector for rapid visual detection of polar components in edible oil. Although this fluorescent probe is soluble in edible oil, the fluorescence of the probe is quenched as the polar components in edible oil increase. It is a "quenching" type probe, resulting in low detection sensitivity. Edible oil contains chlorophyll, so the unfried edible oil has a fluorescence emission peak of chlorophyll near 660nm; with the increase of the degree of frying and the content of polar components, the emission peak of chlorophyll decreases, and there is a strong fluorescence emission in the range of 500-550nm, resulting in a higher background fluorescence, thereby interfering with the detection of polar components. Therefore, it is necessary to develop a probe with an emission wavelength of 700nm or even above 800nm ​​to avoid various background fluorescence interferences of edible oil before and after frying. In addition, in fact, the polarity of edible oil is very small and the range of variation is relatively narrow. Therefore, it is of great practical significance to develop a sensitive fluorescence on-type polar response probe for polar components in edible oil. Summary of the invention

[0004] Aiming at the technical problems of low sensitivity, narrow response range and poor anti-interference ability of fluorescent probes in the process of edible oil detection, the present invention proposes a polar response fluorescent probe with antisolvation effect and its preparation method and application. The fluorescent probe has good open-type polar response ability, excellent anti-interference ability and good fat solubility in the detection process.

[0005] To achieve the above object, the technical solution of the present invention is implemented as follows:

[0006] A polar responsive fluorescent probe with an antisolvation effect has a structure as shown in Formula I:

[0007]

[0008] Where n is 1-3.

[0009] Further, specifically, the structure of the polarity-responsive fluorescent probe is any one of the following structures:

[0010]

[0011] The above-mentioned polarity-responsive fluorescent probe is used for quantitative detection of polar components in frying oil. The specific application steps are as follows:

[0012] (1) dissolving the fluorescent probe with the structure above in a solvent to prepare a probe stock solution;

[0013] (2) adding the soybean oil to be tested into n-hexane solvent, and then adding the probe stock solution prepared in step (1) to prepare a mixed solution, and measuring the fluorescence intensity using a fluorescence spectrophotometer;

[0014] (3) Substituting the fluorescence intensity value at the fluorescence peak into the linear fitting curve of fluorescence intensity and polar content of soybean oil with different polar components, the content of polar components in the soybean oil to be tested can be quantified.

[0015] The concentration of the probe stock solution in the above step (1) is 2 mM.

[0016] Furthermore, in the above step (1), in the structural formula I of the fluorescent probe, when n=1, the solvent is 1,4-dioxane; when n=2, the solvent is acetonitrile; when n=3, the solvent is N,N-dimethylformamide.

[0017] The concentration of the fluorescent probe in the mixed solution of the above step (2) is not less than 5 μM.

[0018] Furthermore, the concentration of the fluorescent probe in the mixed solution of step (2) above is 5-10 μΜ.

[0019] The volume ratio of the soybean oil to be tested to the n-hexane solvent in the mixed solution of the above step (2) is 1:(1-4).

[0020] When the fluorescence spectrophotometer is used for the measurement in step (2), the measurement temperature is room temperature; in the structural formula I of the fluorescent probe, when n=1, the excitation wavelength is 590nm; when n=2, the excitation wavelength is 685nm; when n=3, the excitation wavelength is 780nm.

[0021] Specifically, in step (3), the fluorescence intensity value at the fluorescence peak specifically refers to: in the structural formula I of the fluorescent probe, when n=1, the fluorescence intensity value is the fluorescence intensity I at 620nm 620 ; When n = 2, the fluorescence intensity value is the fluorescence intensity I at 720nm 720When n=3, the fluorescence intensity value is the fluorescence intensity I at 830nm. 830 .

[0022] In the above step (3), in the structural formula I of the fluorescent probe, when n=1, the linear fitting curve equation is I 620 =27.6816×TPM+767.6782, R2=0.9808; when n=2, the linear fitting curve equation is I 720 =17.2512×TPM+1245.0925, R 2 =0.9829; when n=3, the linear fitting curve equation is I 830 =28.5355×TPM+1219.0750, R 2 =0.9934; where TPM is the content of different polar components.

[0023] The beneficial effects produced by the present invention are:

[0024] (1) The present invention proposes a novel fluorescent probe, which exhibits an excellent antisolvation effect, that is, in different polar environments, the fluorescence intensity of the probe increases with the increase of the polarity of the solution. The probe belongs to a fluorescent on-type polar response probe, which expands the structural type of on-type polar response probes and has guiding significance for the development of new on-type polar response probes. In addition, the synthesis of the fluorescent probe is simple and can be synthesized by engineering.

[0025] (2) The present application proposes a new method for detecting the content of polar components in edible oil based on the fact that the polarity of the edible oil increases and the fluorescence of the probe turns on. The probe is added to a mixed solvent containing the edible oil to be tested (soybean oil) and n-hexane, and its fluorescence intensity is measured by a fluorescence spectrophotometer. The fluorescence intensity value at the point where the fluorescence intensity increases is substituted into the linear fitting curve of the fluorescence intensity and the polar content of edible oil with different polar components, which is used to quantify the content of polar components in the test oil sample. Among them, when the structure of the fluorescent probe is formula (Ⅰ-1), that is, when n=1 in structural formula Ⅰ, the excitation wavelength is 590nm, and the linear fitting curve equation is I 620 =27.6816×TPM+767.6782, R 2 =0.9808; when the fluorescent probe structure is formula (I-2), that is, when n=2 in structural formula I, the excitation wavelength is 685nm, and the linear fitting curve equation is I 720 =17.2512×TPM+1245.0925, R 2 =0.9829; when the fluorescent probe structure is formula (I-3), that is, when n=3 in formula I, the excitation wavelength is 780nm, and the linear fitting curve equation is I 830 =28.5355×TPM+1219.0750, R2 =0.9934. The emission wavelengths of probes I-2 and I-3 are as high as 720nm and 830nm, which can effectively avoid the interference of chlorophyll and frying component background fluorescence in edible oil, thus having strong anti-interference ability. In this quantitative detection method, the amount of probe required for a single sample is extremely small, the cost is low, the response is rapid, the sensitivity of the probe is high, and the detection results are not easily affected by the complex environment, temperature and other factors of the oil sample itself. It has certain application value in the actual detection of the content of polar components in frying oil. In addition, the oil sample required for the test is small, which is suitable for the detection of trace oil samples in samples such as pre-prepared dishes and fried foods, which is of great significance for the quality monitoring of the entire chain of food production, transportation, sales and consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0027] Figure 1 The H NMR spectrum of intermediate 2.

[0028] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of product Ⅰ-1.

[0029] Figure 3 The H NMR spectrum of intermediate 3.

[0030] Figure 4 This is the hydrogen nuclear magnetic resonance spectrum of product Ⅰ-2.

[0031] Figure 5 The H NMR spectrum of intermediate 4.

[0032] Figure 6 This is the hydrogen nuclear magnetic resonance spectrum of product Ⅰ-3.

[0033] Figure 7 The fluorescence emission spectra of the fluorescent probes prepared in Examples 1-3 of the present invention and the relationship between the fluorescence intensity and the polarity parameter Δf are shown in Figure 1, wherein (a) is the polarity-sensitive fluorescence emission spectrum of probe I-1 in a cyclohexane / ethanol mixed solution system; (b) is the linear relationship (R) between the fluorescence intensity and the polarity parameter Δf of probe I-1 under different polar environments. 2=0.9940); (c) is the polarity-sensitive fluorescence emission spectrum of probe I-2 in a 1,4-dioxane / N,N-dimethylformamide mixed solution system; (d) is the correlation between the fluorescence intensity and the polarity parameter Δf of probe I-2 under different polar environments (R 2 =0.9931); (e) is the polarity-sensitive fluorescence emission spectrum of probe Ⅰ-3 in a 1,4-dioxane / acetonitrile mixed solution system; (f) is the correlation between the fluorescence intensity and the polarity parameter Δf of Ⅰ-3 under different polar environments (R 2 =0.9989).

[0034] Figure 8 The fluorescence emission spectra of the fluorescent probes prepared in Examples 1-3 of the present invention in edible oils with different contents of polar components and the correlation between the fluorescence intensity and the content of polar components in the edible oils, wherein (a) the fluorescence emission spectrum (excitation wavelength is 590 nm) and (b) the correlation between the fluorescence intensity and the content of polar components in the edible oil of probe I-1 in a mixed solution of edible oil with different contents of polar components and n-hexane (volume ratio is 1:4) (the horizontal axis is the content of polar components in the edible oil, the vertical axis is the fluorescence intensity at 620 nm, R 2 =0.9808); (c) Fluorescence emission spectra (excitation wavelength: 685 nm) and (d) correlation between fluorescence intensity and polar component content of edible oil (abscissa: polar component content in edible oil, ordinate: fluorescence intensity at 720 nm, R 2 =0.9829); (e) Fluorescence emission spectra (excitation wavelength is 780 nm) and (f) correlation between fluorescence intensity and polar component content of edible oil (abscissa is polar component content in edible oil, ordinate is fluorescence intensity at 830 nm, R 2 =0.9934). DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The synthetic routes of the fluorescent probes of the structures shown in Formula I-1 to Formula I-3 in the present invention are as follows:

[0037]

[0038] In some embodiments, the preparation steps of the fluorescent probe are as follows:

[0039] The preparation method of the fluorescent probe (probe I-1) having the structure of formula (I-1) comprises the following steps:

[0040] (1) Add 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-alkylidene)malononitrile (Compound 1) and N,N'-dibenzamide to an acetic anhydride solution, stir under reflux, cool and allow to stand overnight. Filter the solid precipitate, wash the solid with a small amount of acetic anhydride and then with a large amount of water to obtain Intermediate 2.

[0041] Among them, the molar ratio of N,N'-dibenzamide to 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-alkylidene)malononitrile is 1:(1-1.1); the mass-volume ratio of 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-alkylidene)malononitrile to acetic anhydride is 1g:10-20mL.

[0042] (2) The intermediate 2,1,2,3,3-tetramethyl-3H-indolium iodide and sodium acetate are added to an anhydrous ethanol solution, refluxed and stirred, cooled to room temperature and filtered. The filtered solid is purified by thin layer silica gel chromatography, the solvent is distilled off under reduced pressure, the residue is washed with a small amount of boiling ethanol, filtered and collected, and dried under reduced pressure to obtain probe I-1.

[0043] Among them, the molar ratio of intermediate 2, 1,2,3,3-tetramethyl-3H-indolium iodide and sodium acetate is 1:1:(1.5-2); the molar-volume ratio of intermediate 2 and anhydrous ethanol is 1 mol:5-10L.

[0044] The preparation method of the fluorescent probe (probe I-2) having the structure of formula (I-2) comprises the following steps:

[0045] (1) Add 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (Compound 1), malonaldehyde dianiline hydrochloride and sodium acetate to an acetic anhydride solution, reflux with stirring, cool and allow to stand overnight. Filter the solid precipitate, wash the solid with a small amount of acetic anhydride and then with a large amount of water to obtain Intermediate 3.

[0046] Among them, the molar ratio of malondialdehyde dianiline hydrochloride to 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-alkylidene)malononitrile and sodium acetate is 1:(1-1.1):(1-1.1); the mass-volume ratio of 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-alkylidene)malononitrile to acetic anhydride is 1g:10-20mL.

[0047] (2) The intermediate 3,1,2,3,3-tetramethyl-3H-indolium iodide and sodium acetate are added to an anhydrous ethanol solution, refluxed and stirred, cooled to room temperature and filtered. The filtered solid is purified by thin layer silica gel chromatography, the solvent is distilled off under reduced pressure, the residue is washed with a small amount of boiling ethanol and filtered, and dried under reduced pressure to obtain probe I-2.

[0048] Among them, the molar ratio of intermediate 3, 1,2,3,3-tetramethyl-3H-indolium iodide and sodium acetate is 1:1:(1.5-2); the molar-volume ratio of intermediate 3 and anhydrous ethanol is 1 mol:5-10L.

[0049] The preparation method of the fluorescent probe (probe I-3) having the structure of formula (I-3) comprises the following steps:

[0050] (1) Add 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (Compound 1), pentadienaldehyde diphenylamine hydrochloride and sodium acetate to an acetic anhydride solution, reflux with stirring, cool and allow to stand overnight. Filter the solid precipitate, wash the solid with a small amount of acetic anhydride and then with a large amount of water to obtain Intermediate 4.

[0051] Among them, the molar ratio of pentadienaldehyde diphenylamine hydrochloride to 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-alkylidene)malononitrile and sodium acetate is 1:(1-1.1):(1-1.1); the mass-volume ratio of 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-alkylidene)malononitrile to acetic anhydride is 1g:10-20mL.

[0052] (2) The intermediate 4,1,2,3,3-tetramethyl-3H-indolium iodide and sodium acetate are added to an anhydrous ethanol solution, refluxed and stirred, cooled to room temperature and filtered. The filtered solid is purified by thin layer silica gel chromatography, the solvent is distilled off under reduced pressure, the residue is washed with a small amount of boiling ethanol and filtered, and dried under reduced pressure to obtain probe I-3.

[0053] Among them, the molar ratio of intermediate 4, 1,2,3,3-tetramethyl-3H-indolium iodide and sodium acetate is 1:1:(1.5-2); the molar-volume ratio of intermediate 4 and anhydrous ethanol is 1 mol:5-10L.

[0054] Example 1

[0055] The preparation method of a polar responsive fluorescent probe with antisolvation effect (compound shown in Formula I-1) of this embodiment comprises the following specific steps:

[0056]

[0057] (1) Compound 1, 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (CAS: 171082-32-9, 1014 mg, 5.1 mmol) and N,N'-dibenzamide (CAS: 622-15-1, 981 mg, 5 mmol) were reacted in acetic anhydride (Ac) 2 O, CAS: 108-24-7, 20mL) and stirred and refluxed for 30 minutes, then the heating was turned off and the stirring was stopped, and the mixture was allowed to stand overnight. After the reaction, the yellow precipitate was filtered, first washed with a small amount of acetic anhydride (2×5mL), then washed with a large amount of water to remove the acetic anhydride, and finally washed with isopropanol and dried in vacuo to obtain a yellow solid intermediate 2 (1g, 57%). 1 H NMR (600MHz, DMSO-d6) δ8.71(d,J=14.3Hz,1H),7.65(dd,J=8.3,6.6Hz,2H),7.62(d,J=7.2 Hz, 1H), 7.48 (d, J = 7.3Hz, 2H), 5.09 (d, J = 14.3Hz, 1H), 2.04 (d, J = 5.4Hz, 3H), 1.66 (s, 6H), such as Figure 1 shown.

[0058] (2) Intermediate 2 (688 mg, 2 mmol), 1,2,3,3-tetramethyl-3H-indolium iodide (CAS: 5418-63-3, 602 mg, 2 mmol) and sodium acetate (CAS: 127-09-3, 328 mg, 4 mmol) were added to anhydrous ethanol (EtOH, CAS: 64-17-5, 10 mL). The mixture was refluxed at 80°C for 8 h. After the mixture was cooled, it was filtered and the obtained solid was purified by column chromatography (CH 2 Cl 2 ) was purified to give purple solid compound Ⅰ-1 (510 mg, 65%). 1 H NMR(600MHz,Chloroform-d)δ8.93(s,1H),7.36(d,J=7.7Hz,1H),7.33(d,J=7.6Hz,1H),7.19(t,J= 7.0Hz,1H),6.99(d,J=8.0Hz,1H),5.79(d,J=13.1Hz,2H),3.45(s,3H),1.73(s,6H),1.60(s,6H), such as Figure 2 shown.

[0059] Example 2

[0060] The preparation method of a polar responsive fluorescent probe with antisolvation effect (compound shown in Formula I-2) of this embodiment comprises the following specific steps:

[0061]

[0062] (1) Compound 1, i.e., 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (CAS: 171082-32-9, 1014 mg, 5.1 mmol), malonaldehyde dianiline hydrochloride (CAS: 50328-50-2, 1293 mg, 5 mmol) and sodium acetate (CAS: 127-09-3, 418 mg, 5.1 mmol) were reacted in acetic anhydride (Ac) to obtain a molten salt. 2 O, CAS: 108-24-7, 20mL) and stirred and refluxed for 30min, then the heating was turned off and the stirring was stopped, and the mixture was allowed to stand overnight. After the reaction, the yellow precipitate was filtered, first washed with a small amount of acetic anhydride (2×5mL), then washed with a large amount of water to remove the acetic anhydride, and finally washed with isopropanol and dried in vacuo to obtain a brick-red solid intermediate 3 (870mg, 47%). 1 H NMR(600MHz,Chloroform-d)δ8.26(d,J=13.7Hz,1H),7.63-7.57(m,3H),7.38(dd,J=15.4,11.2H z,1H),7.23-7.19(m,2H),6.20(s,1H),5.27(dd,J=13.7,11.2Hz,1H),2.00(s,3H),1.68(s,6H), such as Figure 3 shown.

[0063] (2) Intermediate 3 (185 mg, 0.5 mmol), 1,2,3,3-tetramethyl-3H-indolium iodide (CAS: 5418-63-3, 150.5 mg, 0.5 mmol) and sodium acetate (CAS: 127-09-3, 82 mg, 1 mmol) were added to anhydrous ethanol (EtOH, CAS: 64-17-5, 5 mL). The mixture was refluxed at 80°C for 8 h. After the mixture was cooled, it was filtered and the obtained solid was purified by column chromatography (CH 2 Cl 2 ) was purified to give a blue-green solid compound Ⅰ-2 (100 mg, 49%). 1 H NMR (600 MHz, DMSO-d 6)δ8.14(t,J=13.1Hz,1H),7.90(d,J=13.1Hz,1H),7.60(d,J=7.4Hz,1H),7.40(d,J=6.9Hz,2H),7.24(t,J=7.0Hz,1 H), 6.48 (t, J = 12.4Hz, 1H), 6.27 (d, J = 13.8Hz, 1H), 6.04 (d, J = 13.9Hz, 1H), 3.59 (s, 3H), 1.71 (s, 6H), 1.64 (s, 6H), such as Figure 4 shown.

[0064] Example 3

[0065] The preparation method of a polar responsive fluorescent probe with antisolvation effect (compound shown in Formula I-3) of this embodiment comprises the following specific steps:

[0066]

[0067] (1) Compound 1, i.e., 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (CAS: 171082-32-9, 1014 mg, 5.1 mmol), pentadienaldehyde diphenylamine hydrochloride (CAS: 1497-49-0, 1420 mg, 5 mmol) and sodium acetate (CAS: 127-09-3, 418 mg, 5.1 mmol) were reacted in acetic anhydride (Ac) to obtain a 5% acetic acid solution of 1% pyrrolidone. 2 O, CAS: 108-24-7, 20mL) and stirred and refluxed for 30 minutes, then the heating was turned off and the stirring was stopped, and the mixture was allowed to stand overnight. After the reaction, the yellow precipitate was filtered, first washed with a small amount of acetic anhydride (2×5mL), then washed with a large amount of water to remove the acetic anhydride, and finally washed with isopropanol and dried in vacuo to obtain a purple solid intermediate 4 (1g, 56%). 1 H NMR(600MHz,Chloroform-d)δ8.08(t,J=15.0Hz,1H),7.60(t,J=7.9Hz,2H),7.58-7.54(m,1 H),7.34(dd,J=15.3,11.2Hz,1H),7.23(td,J=6.3,5.6,1.7Hz,2H),6.93(dd,J=14.4,11.3Hz ,1H),6.89-6.81(m,1H),6.29(d,J=15.1Hz,1H),6.20(dd,J=14.5,11.2Hz,1H),5.70(d,J=11 .4Hz,1H),5.32(d,J=25.2Hz,1H),5.24(dd,J=13.8,11.4Hz,1H),1.98(s,3H),1.71(s,3H), such as Figure 5 shown.

[0068] (2) Intermediate 4 (198 mg, 0.5 mmol), 1,2,3,3-tetramethyl-3H-indolium iodide (CAS: 5418-63-3, 150.5 mg, 0.5 mmol) and sodium acetate (CAS: 127-09-3, 82 mg, 1 mmol) were added to anhydrous ethanol (EtOH, CAS: 64-17-5, 5 mL). After reflux at 80°C for 8 h, the mixed solution was cooled and filtered. The obtained solid was purified by column chromatography (CH 2 Cl 2 ) was purified to give green solid compound Ⅰ-3 (90 mg, 40%). 1 H NMR (600 MHz, DMSO-d 6 )δ8.02-7.95(m,1H),7.68(s,1H),7.63-7.57(m,2H),7.43(d,J=5.8Hz,2H),7.28(d,J=7.1Hz,1H),6.5 3(t,J=12.6Hz,1H),6.46-6.40(m,2H),5.97(d,J=13.4Hz,1H),3.63(s,3H),1.63(s,6H),1.56(s,6H), such as Figure 6 shown.

[0069] Example 4

[0070] The preparation method of a polar responsive fluorescent probe with antisolvation effect (compound shown in Formula I-1) of this embodiment comprises the following specific steps:

[0071]

[0072] (1) Compound 1, 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (CAS: 171082-32-9, 1094 mg, 5.5 mmol) and N,N'-dibenzamide (CAS: 622-15-1, 981 mg, 5 mmol) were reacted in acetic anhydride (Ac) 2 O, CAS: 108-24-7, 15 mL) and stirred under reflux for 30 min, then the heating was turned off and the stirring was stopped, and the mixture was allowed to stand overnight. After the reaction, the yellow precipitate was filtered, first washed with a small amount of acetic anhydride (2×5 mL), then washed with a large amount of water to remove the acetic anhydride, and finally washed with isopropanol and dried in vacuo to obtain a yellow solid intermediate 2. 1H NMR (600MHz, DMSO-d6) δ8.71(d,J=14.3Hz,1H),7.65(dd,J=8.3,6.6Hz,2H),7.62(d,J=7.2 Hz, 1H), 7.48 (d, J = 7.3Hz, 2H), 5.09 (d, J = 14.3Hz, 1H), 2.04 (d, J = 5.4Hz, 3H), 1.66 (s, 6H).

[0073] (2) Intermediate 2 (688 mg, 2 mmol), 1,2,3,3-tetramethyl-3H-indolium iodide (CAS: 5418-63-3, 602 mg, 2 mmol) and sodium acetate (CAS: 127-09-3, 246 mg, 3 mmol) were added to anhydrous ethanol (EtOH, CAS: 64-17-5, 20 mL). The mixture was refluxed at 80°C for 8 h. After the mixture was cooled, it was filtered and the obtained solid was purified by column chromatography (CH 2 Cl 2 ) was purified to give a purple solid compound Ⅰ-1. 1 H NMR(600MHz,Chloroform-d)δ8.93(s,1H),7.36(d,J=7.7Hz,1H),7.33(d,J=7.6Hz,1H),7.19(t,J =7.0Hz, 1H), 6.99 (d, J = 8.0Hz, 1H), 5.79 (d, J = 13.1Hz, 2H), 3.45 (s, 3H), 1.73 (s, 6H), 1.60 (s, 6H).

[0074] Example 5

[0075] The preparation method of a polar responsive fluorescent probe with antisolvation effect (compound shown in Formula I-1) of this embodiment comprises the following specific steps:

[0076]

[0077] (1) Compound 1, 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (CAS: 171082-32-9, 1044 mg, 5.25 mmol) and N,N'-dibenzamide (CAS: 622-15-1, 981 mg, 5 mmol) were reacted in acetic anhydride (Ac) 2 O, CAS: 108-24-7, 10 mL) and stirred and refluxed for 30 min, then the heating was turned off and the stirring was stopped, and the mixture was allowed to stand overnight. After the reaction, the yellow precipitate was filtered, first washed with a small amount of acetic anhydride (2×5 mL), then washed with a large amount of water to remove the acetic anhydride, and finally washed with isopropanol and dried in vacuo to obtain a yellow solid intermediate 2. 1H NMR (600MHz, DMSO-d6) δ8.71(d,J=14.3Hz,1H),7.65(dd,J=8.3,6.6Hz,2H),7.62(d,J=7.2 Hz, 1H), 7.48 (d, J = 7.3Hz, 2H), 5.09 (d, J = 14.3Hz, 1H), 2.04 (d, J = 5.4Hz, 3H), 1.66 (s, 6H).

[0078] (2) Intermediate 2 (688 mg, 2 mmol), 1,2,3,3-tetramethyl-3H-indolium iodide (CAS: 5418-63-3, 602 mg, 2 mmol) and sodium acetate (CAS: 127-09-3, 328 mg, 4 mmol) were added to anhydrous ethanol (EtOH, CAS: 64-17-5, 14 mL). The mixture was refluxed at 80°C for 8 h. After the mixture was cooled, it was filtered and the obtained solid was purified by column chromatography (CH 2 Cl 2 ) was purified to give a purple solid compound Ⅰ-1. 1 H NMR(600MHz,Chloroform-d)δ8.93(s,1H),7.36(d,J=7.7Hz,1H),7.33(d,J=7.6Hz,1H),7.19(t,J =7.0Hz, 1H), 6.99 (d, J = 8.0Hz, 1H), 5.79 (d, J = 13.1Hz, 2H), 3.45 (s, 3H), 1.73 (s, 6H), 1.60 (s, 6H).

[0079] Example 6

[0080] The preparation method of a polar responsive fluorescent probe with antisolvation effect (compound shown in Formula I-2) of this embodiment comprises the following specific steps:

[0081]

[0082] (1) Compound 1, i.e., 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (CAS: 171082-32-9, 1014 mg, 5.1 mmol), malonaldehyde dianiline hydrochloride (CAS: 50328-50-2, 1319 mg, 5.1 mmol) and sodium acetate (CAS: 127-09-3, 418 mg, 5.1 mmol) were reacted in acetic anhydride (Ac) to obtain a molten salt. 2O, CAS: 108-24-7, 10 mL) and stirred under reflux for 30 min, then the heating was turned off and the stirring was stopped, and the mixture was allowed to stand overnight. After the reaction, the yellow precipitate was filtered, first washed with a small amount of acetic anhydride (2×5 mL), then washed with a large amount of water to remove the acetic anhydride, and finally washed with isopropanol and dried in vacuo to obtain a brick red solid intermediate 3. 1 HNMR(600MHz,Chloroform-d)δ8.26(d,J=13.7Hz,1H),7.63-7.57(m,3H),7.38(dd,J=15.4,11.2 Hz,1H),7.23-7.19(m,2H),6.20(s,1H),5.27(dd,J=13.7,11.2Hz,1H),2.00(s,3H),1.68(s,6H).

[0083] (2) Intermediate 3 (185 mg, 0.5 mmol), 1,2,3,3-tetramethyl-3H-indolium iodide (CAS: 5418-63-3, 150.5 mg, 0.5 mmol) and sodium acetate (CAS: 127-09-3, 62 mg, 0.75 mmol) were added to anhydrous ethanol (EtOH, CAS: 64-17-5, 3.5 mL). The mixture was refluxed at 80°C for 8 h. After the mixture was cooled, it was filtered and the obtained solid was purified by column chromatography (CH 2 Cl 2 ) was purified to obtain a blue-green solid compound Ⅰ-2. 1 H NMR (600 MHz, DMSO-d 6 )δ8.14(t,J=13.1Hz,1H),7.90(d,J=13.1Hz,1H),7.60(d,J=7.4Hz,1H),7.40(d,J=6.9Hz,2H),7.24(t,J=7.0Hz,1 H), 6.48 (t, J = 12.4Hz, 1H), 6.27 (d, J = 13.8Hz, 1H), 6.04 (d, J = 13.9Hz, 1H), 3.59 (s, 3H), 1.71 (s, 6H), 1.64 (s, 6H).

[0084] Example 7

[0085] The preparation method of a polar responsive fluorescent probe with antisolvation effect (compound shown in Formula I-2) of this embodiment comprises the following specific steps:

[0086]

[0087] (1) Compound 1, i.e., 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (CAS: 171082-32-9, 1093 mg, 5.5 mmol), malonaldehyde dianiline hydrochloride (CAS: 50328-50-2, 1293 mg, 5 mmol) and sodium acetate (CAS: 127-09-3, 451 mg, 5.5 mmol) were reacted in acetic anhydride (Ac) to obtain a molten salt. 2 O, CAS: 108-24-7, 15 mL) and stirred and refluxed for 30 min, then the heating was turned off and the stirring was stopped, and the mixture was allowed to stand overnight. After the reaction, the yellow precipitate was filtered, first washed with a small amount of acetic anhydride (2×5 mL), then washed with a large amount of water to remove the acetic anhydride, and finally washed with isopropanol and dried in vacuo to obtain a brick red solid intermediate 3. 1 HNMR(600MHz,Chloroform-d)δ8.26(d,J=13.7Hz,1H),7.63-7.57(m,3H),7.38(dd,J=15.4,11.2 Hz,1H),7.23-7.19(m,2H),6.20(s,1H),5.27(dd,J=13.7,11.2Hz,1H),2.00(s,3H),1.68(s,6H).

[0088] (2) Intermediate 3 (185 mg, 0.5 mmol), 1,2,3,3-tetramethyl-3H-indolium iodide (CAS: 5418-63-3, 150.5 mg, 0.5 mmol) and sodium acetate (CAS: 127-09-3, 82 mg, 1 mmol) were added to anhydrous ethanol (EtOH, CAS: 64-17-5, 2.5 mL). The mixture was refluxed at 80°C for 8 h. After the mixture was cooled, it was filtered and the obtained solid was purified by column chromatography (CH 2 Cl 2 ) was purified to obtain a blue-green solid compound Ⅰ-2. 1 H NMR (600 MHz, DMSO-d 6 )δ8.14(t,J=13.1Hz,1H),7.90(d,J=13.1Hz,1H),7.60(d,J=7.4Hz,1H),7.40(d,J=6.9Hz,2H),7.24(t,J=7.0Hz,1 H), 6.48 (t, J = 12.4Hz, 1H), 6.27 (d, J = 13.8Hz, 1H), 6.04 (d, J = 13.9Hz, 1H), 3.59 (s, 3H), 1.71 (s, 6H), 1.64 (s, 6H).

[0089] Example 8

[0090] The preparation method of a polar responsive fluorescent probe with antisolvation effect (compound shown in Formula I-3) of this embodiment comprises the following specific steps:

[0091]

[0092] (1) Compound 1, i.e., 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (CAS: 171082-32-9, 1014 mg, 5.1 mmol), pentadienaldehyde diphenylamine hydrochloride (CAS: 1497-49-0, 1562 mg, 5.1 mmol) and sodium acetate (CAS: 127-09-3, 418 mg, 5.1 mmol) were reacted in acetic anhydride (Ac) to obtain a 5% acetic acid solution of 1% acetic acid. 2 O, CAS: 108-24-7, 10 mL) and stirred under reflux for 30 min, then the heating was turned off and the stirring was stopped, and the mixture was allowed to stand overnight. After the reaction, the yellow precipitate was filtered, first washed with a small amount of acetic anhydride (2×5 mL), then washed with a large amount of water to remove the acetic anhydride, and finally washed with isopropanol and dried in vacuo to obtain a purple solid intermediate 4. 1 H NMR(600MHz,Chloroform-d)δ8.08(t,J=15.0Hz,1H),7.60(t,J=7.9Hz,2H),7.58-7.54(m,1 H),7.34(dd,J=15.3,11.2Hz,1H),7.23(td,J=6.3,5.6,1.7Hz,2H),6.93(dd,J=14.4,11.3Hz ,1H),6.89-6.81(m,1H),6.29(d,J=15.1Hz,1H),6.20(dd,J=14.5,11.2Hz,1H),5.70(d,J=1 1.4Hz, 1H), 5.32 (d, J = 25.2Hz, 1H), 5.24 (dd, J = 13.8, 11.4Hz, 1H), 1.98 (s, 3H), 1.71 (s, 3H).

[0093] (2) Intermediate 4 (198 mg, 0.5 mmol), 1,2,3,3-tetramethyl-3H-indolium iodide (CAS: 5418-63-3, 150.5 mg, 0.5 mmol) and sodium acetate (CAS: 127-09-3, 72 mg, 0.875 mmol) were added to anhydrous ethanol (EtOH, CAS: 64-17-5, 2.5 mL). After reflux at 80°C for 8 h, the mixed solution was cooled and filtered. The obtained solid was purified by column chromatography (CH 2 Cl 2 ) was purified to give green solid compound Ⅰ-3 (90 mg, 40%). 1H NMR (600 MHz, DMSO-d 6 )δ8.02-7.95(m,1H),7.68(s,1H),7.63-7.57(m,2H),7.43(d,J=5.8Hz,2H),7.28(d,J=7.1Hz,1H),6.5 3(t,J=12.6Hz,1H),6.46-6.40(m,2H),5.97(d,J=13.4Hz,1H),3.63(s,3H),1.63(s,6H),1.56(s,6H).

[0094] Example 9

[0095] The preparation method of a polar responsive fluorescent probe with antisolvation effect (compound shown in Formula I-3) of this embodiment comprises the following specific steps:

[0096]

[0097] (1) Compound 1, i.e., 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (CAS: 171082-32-9, 1093 mg, 5.5 mmol), pentadienaldehyde diphenylamine hydrochloride (CAS: 1497-49-0, 1420 mg, 5 mmol) and sodium acetate (CAS: 127-09-3, 450 mg, 5.5 mmol) were reacted in acetic anhydride (Ac) to obtain a 5% acetic acid solution of 1% pyrrolidone. 2 O, CAS: 108-24-7, 15 mL) and stirred and refluxed for 30 min, then the heating was turned off and the stirring was stopped, and the mixture was allowed to stand overnight. After the reaction, the yellow precipitate was filtered, first washed with a small amount of acetic anhydride (2×5 mL), then washed with a large amount of water to remove the acetic anhydride, and finally washed with isopropanol and dried in vacuo to obtain a purple solid intermediate 4. 1 H NMR(600MHz,Chloroform-d)δ8.08(t,J=15.0Hz,1H),7.60(t,J=7.9Hz,2H),7.58-7.54(m,1 H),7.34(dd,J=15.3,11.2Hz,1H),7.23(td,J=6.3,5.6,1.7Hz,2H),6.93(dd,J=14.4,11.3Hz ,1H),6.89-6.81(m,1H),6.29(d,J=15.1Hz,1H),6.20(dd,J=14.5,11.2Hz,1H),5.70(d,J=1 1.4Hz, 1H), 5.32 (d, J = 25.2Hz, 1H), 5.24 (dd, J = 13.8, 11.4Hz, 1H), 1.98 (s, 3H), 1.71 (s, 3H).

[0098] (2) Intermediate 4 (198 mg, 0.5 mmol), 1,2,3,3-tetramethyl-3H-indolium iodide (CAS: 5418-63-3, 150.5 mg, 0.5 mmol) and sodium acetate (CAS: 127-09-3, 62 mg, 0.75 mmol) were added to anhydrous ethanol (EtOH, CAS: 64-17-5, 3.5 mL). After reflux at 80°C for 8 h, the mixed solution was cooled and filtered. The obtained solid was purified by column chromatography (CH 2 Cl 2 ) was purified to give green solid compound Ⅰ-3. 1 H NMR (600 MHz, DMSO-d 6 )δ8.02-7.95(m,1H),7.68(s,1H),7.63-7.57(m,2H),7.43(d,J=5.8Hz,2H),7.28(d,J=7.1Hz,1H),6.53(t,J=

[0099] 12.6Hz, 1H), 6.46-6.40 (m, 2H), 5.97 (d, J = 13.4Hz, 1H), 3.63 (s, 3H), 1.63 (s, 6H), 1.56 (s, 6H).

[0100] The responses of the fluorescent probes prepared in Examples 1-3 and having structures shown in Formula I-1 to Formula I-3 to solvents of different polarities were investigated respectively. The specific steps and results are as follows.

[0101] (a) Response of fluorescent probe Ⅰ-1 to solvents of different polarities

[0102] Cyclohexane and ethanol were mixed to prepare cyclohexane / ethanol mixed solution systems with different ethanol volume fractions, and then probe I-1 stock solution (probe I-1 stock solution: probe I-1 was dissolved in 1,4-dioxane solvent to a concentration of 2mM) was added until the final concentration of probe I-1 in the mixed solution system was 10μM. Fluorescence spectrum data was tested with 590nm as the excitation wavelength. Figure 7 As shown in a, with the increase of ethanol volume fraction, the fluorescence intensity of the probe gradually increases. 620 A linear fit is made with the polarity parameter Δf value of each polar solvent, such as Figure 7 As shown in b, the fluorescence intensity I 620 There is a good correlation between the polarity parameter Δf and the probe Ⅰ-1, indicating that the probe Ⅰ-1 has an open-type polarity response capability (R 2 =0.9940, response range: Δf=0~0.2706).

[0103] (b) Response of fluorescent probe Ⅰ-2 to solvents of different polarities

[0104] Mix 1,4-dioxane and N,N-dimethylformamide to prepare a 1,4-dioxane / N,N-dimethylformamide mixed solution system with different N,N-dimethylformamide volume fractions, and then add probe I-2 stock solution (probe I-2 stock solution: dissolve probe I-2 in acetonitrile solvent, the concentration is 2mM) until the final concentration of probe I-2 in the mixed solution system is 2μM. Test the fluorescence spectrum data with 690nm as the excitation wavelength. Figure 7 As shown in c, with the increase of N,N-dimethylformamide volume fraction, the fluorescence intensity of the probe gradually increases. 720 A linear fit is made with the polarity parameter Δf value of each polar solvent, such as Figure 7 d, the fluorescence intensity I 720 There is a good correlation between the polarity parameter Δf value and the probe Ⅰ-2, indicating that the probe Ⅰ-2 has an open-type polarity response capability (R 2 =0.9931, response range: Δf=0.0206~0.2942).

[0105] (c) Response of fluorescent probe Ⅰ-3 to solvents of different polarities

[0106] Mix 1,4-dioxane and acetonitrile to prepare a 1,4-dioxane / acetonitrile mixed solution system with different acetonitrile volume fractions, and then add probe Ⅰ-3 stock solution (Ⅰ-3 stock solution: probe Ⅰ-3 is dissolved in N,N-dimethylformamide solvent, the concentration is 2mM) until the final concentration of Ⅰ-3 in the mixed solution system is 2μM. Test the fluorescence spectrum data with 800nm ​​as the excitation wavelength. Figure 7 As shown in e, with the increase of acetonitrile volume fraction, the fluorescence intensity of the probe gradually increases. 830 A linear fit is made with the polarity parameter Δf value of each polar solvent, such as Figure 7 f shows the fluorescence intensity I 830 There is a good correlation between the value of the polarity parameter Δf and the probe I-3, indicating that the probe I-3 has an open-type polarity response capability (R 2 =0.9989, response range: Δf=0.0206~0.3055).

[0107] Application Examples

[0108] The application of fluorescent probes (Ⅰ-1, Ⅰ-2 and Ⅰ-3) in detecting the content of polar components in edible oils is as follows:

[0109] (1) Preparation of oil samples with different polar component contents

[0110] The commercially available Golden Dragon Fish brand soybean fried dough sticks were used to fry, and samples were taken at different time periods to detect the content of polar components according to the national standard method (GB 5009.202-2016). The content of polar components was 1.1%, 6.1%, 13.9%, 21.5%, 26.9%, and 29.3%, respectively.

[0111] (2) Detection of the content of polar components in edible oil using fluorescent probes (Ⅰ-1, Ⅰ-2 and Ⅰ-3)

[0112] A. Detection of polar components in edible oil using fluorescent probe Ⅰ-1 in solution

[0113] Add 400 μL of the oil sample to be tested (1.1%, 6.1%, 13.9%, 21.5%, 26.9%, 29.3%) to 1600 μL of n-hexane, and then add 10 μL of the probe stock solution (the stock solution is prepared in 1,4-dioxane solution, the concentration is 2 mM) and mix well. After adding, the concentration of probe Ⅰ-1 is 10 μM. Place the test solution in a 10.0 mm quartz fluorescence cuvette at room temperature and measure the fluorescence intensity at an excitation wavelength of 590 nm. Figure 8 As shown in a, as the content of polar components in soybean oil increases, the fluorescence intensity of the probe at 620 nm gradually increases. Figure 8 As shown in b, the fluorescence intensity I at 620 nm and the content of different polar components in soybean oil 620 There is a good linear correlation between R 2 =0.9808, the linear equation is: 620 =27.6816×TPM+767.6782, TPM is the content of different polar components.

[0114] B. Detection of polar components in edible oil by fluorescent probe Ⅰ-2 in solution

[0115] Add 1 mL of the oil sample to be tested (1.1%, 6.1%, 13.9%, 21.5%, 26.9%, 29.3%) to 1 mL of cyclohexane, then add 5 μL of the probe stock solution (the stock solution is prepared in acetonitrile solution, the concentration is 2 mM) and mix well. After adding, the concentration of probe I-2 is 5 μM. Place the test solution in a 10.0 mm quartz fluorescence cuvette at room temperature and measure the fluorescence intensity at an excitation wavelength of 685 nm. Figure 8 As shown in Figure c, as the content of polar components in soybean oil increases, the fluorescence intensity of the probe at 720 nm gradually increases. Figure 8 As shown in d, the fluorescence intensity I at 720 nm of soybean oil with different polar component contents 720 There is a good linear correlation between R 2 =0.9829, the linear equation is: I 720=17.2512×TPM+1245.0925, TPM is the content of different polar components.

[0116] C. Detection of polar components in edible oil by fluorescent probe Ⅰ-3 in solution

[0117] Add 500μL of the oil sample to be tested (1.1%, 6.1%, 13.9%, 21.5%, 26.9%, 29.3%) to 1500μL of n-hexane, and then add 5μL of the probe stock solution (the stock solution is prepared in N,N-dimethylformamide solution, the concentration is 2mM) and mix well. After adding, the concentration of probe I-3 is 5μM. Place the test solution in a 10.0mm quartz fluorescence cuvette at room temperature and measure the fluorescence intensity at an excitation wavelength of 780nm. Figure 8 As shown in Figure 5, as the content of polar components in soybean oil increases, the fluorescence intensity of the probe at 830 nm gradually increases. Figure 8 f shows the relationship between the content of soybean oil with different polar components and the fluorescence intensity I at 830 nm. 830 There is a good linear correlation between R 2 =0.9934, the linear equation is: I 830 =28.5355×TPM+1219.0750, TPM is the content of different polar components.

[0118] It can be seen from the above examples that the fluorescent probe provided by the present invention has simple synthesis steps and simple separation and purification steps; it has an open-type polar response property and has good testing capabilities in testing the content of polar components in edible oils.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A polar responsive fluorescent probe of antisolvation effect, characterized in that: The polarity-responsive fluorescent probe has a structure as shown in Formula I: Where n is 1-3.

2. Application of the polarity-responsive fluorescent probe according to claim 1 in quantitative detection of polar components in frying oil.

3. The use according to claim 2, characterized in that: Here are the steps: (1) dissolving the fluorescent probe of the structure described in claim 1 in a solvent to prepare a probe stock solution; (2) adding the soybean oil to be tested into n-hexane solvent, and then adding the probe stock solution prepared in step (1) to prepare a mixed solution, and measuring the fluorescence intensity using a fluorescence spectrophotometer; (3) Substituting the fluorescence intensity value at the fluorescence peak into the linear fitting curve of fluorescence intensity and polar content of soybean oil with different polar components, the content of polar components in the soybean oil to be tested can be quantified.

4. The use according to claim 3, characterized in that: The concentration of the probe stock solution in step (1) is 2 mM.

5. The use according to claim 4, characterized in that: In the step (1), in the structural formula I of the fluorescent probe, when n=1, the solvent is 1,4-dioxane; when n=2, the solvent is acetonitrile; when n=3, the solvent is N,N-dimethylformamide.

6. The use according to claim 5, characterized in that: The concentration of the fluorescent probe in the mixed solution of step (2) is not less than 5 μM.

7. The use according to claim 6, characterized in that: The concentration of the fluorescent probe in the mixed solution of step (2) is 5-10 μM.

8. The use according to claim 7, characterized in that: The volume ratio of the soybean oil to be tested to the n-hexane solvent in the mixed solution of step (2) is 1:(1-4).

9. The use according to claim 8, characterized in that: When the fluorescence spectrophotometer is used for measurement in step (2), the measurement temperature is room temperature; in the structural formula I of the fluorescent probe, when n=1, the excitation wavelength is 590nm; when n=2, the excitation wavelength is 685nm; when n=3, the excitation wavelength is 780nm.

10. The use according to claim 9, characterized in that: In the step (3), in the structural formula I of the fluorescent probe, when n=1, the linear fitting curve equation is 620 =27.6816×TPM+767.6782, R2=0.9808; when n=2, the linear fitting curve equation is I 720 =17.2512×TPM+1245.0925, R2=0.9829; when n=3, the linear fitting curve equation is I 830 =28.5355×TPM+1219.0750, R2=0.9934; where TPM is the content of different polar components.

Images