Application of 1, 3-bis (dicyanomethylene) indan in detection of polar components of edible oil

Abstract

The invention belongs to the field of rapid detection of the content of polar components of edible oil, and discloses application of 1, 3-bis (dicyanomethylene) indan in detection of polar components of edible oil. According to the invention, 1, 3-bis (dicyanomethylene) indan is taken as a probe, and the probe has ultra-sensitive polarity response performance. Under the condition of natural light, obvious color change is displayed in edible oil with different polar components, and rapid colorimetric detection of the polar components of the edible oil is realized by naked eyes. The emission peak of the probe is 646 nm, so that the interference of blue-green fluorescence of edible oil is effectively avoided; high correlation exists between the fluorescence intensity at the long wave and the polar component content of the edible oil, so that the accurate determination of the polar component content of the edible oil is realized. The probe realizes colorimetric and fluorescent dual-channel detection, so that the aim of quickly, sensitively and accurately detecting polar components of edible oil is fulfilled. According to the colorimetric method, the polar components of the edible oil can be rapidly detected without any instrument, the cost is low, the operation is simple, and professional skills are not needed, so that the colorimetric method is very suitable for large-scale and on-site accurate determination of the whole chain of food production, storage, transportation, sales and consumption in food factories, market supervision and the like.

Description

Technical Field

[0001] The invention relates to the field of frying oil polar component detection, in particular to the application of 1,3-bis(dicyanomethylidene)indane in detecting edible oil polar components. Background Art

[0002] Frying is a common method of processing food, which can cook food quickly and enhance the flavor. Through high-temperature frying, a crispy crust forms on the surface of the food while the inside remains tender and smooth, making the food crispy on the outside and tender on the inside. However, as the frying time increases, edible oil will produce harmful substances. Using edible oil for too long may form carcinogens, such as acrylamide, and long-term intake will increase the risk of cancer. Long-term use of edible oil will also produce more polar compounds and polymers, which will burden the liver and cardiovascular system and increase the risk of cardiovascular disease. Carcinogens such as acrylamide may also form in oils and fats, and long-term intake will increase the risk of cancer.

[0003] During the frying process, triglycerides in edible oil will undergo complex chemical reactions with air moisture and other factors to produce products with greater polarity. Therefore, the content of polar components in edible oil has become a comprehensive indicator for evaluating oil quality. For example, Germany stipulates that the total polar components must not exceed 24%, France and Finland stipulate that the total polar components must not exceed 25%, and the limit in my country is 27%. When the polar components of oil exceed this limit, they will be required to be discarded immediately and must not be used any further. Column chromatography is the most traditional and standard method for detecting polar components in frying oil, but its operation is complicated, time-consuming, requires professional inspectors, and has a relatively large demand for sample volume, which limits its applicability for daily monitoring. Therefore, there is an urgent need for a method to quickly detect the polarity of edible oil.

[0004] Fluorescent probes have the advantages of low cost, high sensitivity and good selectivity, and have been widely used in the detection of edible oil in recent years. As the polar components of edible oil increase, the polarity and viscosity of edible oil gradually increase. Therefore, probes that respond to polarity and viscosity have been used to detect polar components of edible oil in recent years, such as Cui S, Wang B, Yan X, et al. Anovel emitter: sensing mechanical stimuli and monitoring total polarmaterials in frying oil[J]. Dyes and Pigments, 2020, 174: 108020. and Shi J, TaoJ, Fu Y, et al. Rapid quantitative evaluation of total polar materials (TPM)in frying oil based on an “off-on” fluorescence viscosity response probe[J].Analytica Chimica Acta, 2024, 1292: 342267. Although compared with detection methods such as chromatography, fluorescence detection does not require large and expensive instruments, it is still subject to the temporal and spatial limitations of instruments and detection flux.

[0005] In contrast, the method of determining the polar components of edible oil by colorimetry does not require any instruments, has fewer operating steps, is low-cost, and does not require professionals. You only need to mix the sample with the reagent and then compare it with the colorimetric card to get the result. It is more suitable for rapid testing, especially for large-scale screening on site, thereby improving the detection throughput and screening efficiency, and can also greatly reduce the detection cost.

[0006] It is very difficult to cause a change in solution color based on a small change in polar components. So far, there is still no method to determine the polar components of edible oil by colorimetry. Summary of the invention

[0007] In order to solve the above technical problems, the present invention proposes the application of 1,3-bis(dicyanomethylene)indane in detecting polar components of edible oil. The present invention uses 1,3-bis(dicyanomethylene)indane as a fluorescent probe, which detects polar components of edible oil through colorimetric and fluorescent dual channels.

[0008] To achieve the above object, the technical solution of the present invention is implemented as follows: The fluorescent probe proposed in the present invention is 1,3-bis(dicyanomethylene)indane, the molecular formula of which is C 15H6N4, the structural formula is as follows: .

[0009] The above-mentioned 1,3-bis(dicyanomethylidene)indane is used for detecting polar components in edible oil.

[0010] Furthermore, the 1,3-bis(dicyanomethylidene)indane is used to detect polar components of edible oil through colorimetric and fluorescent dual channels.

[0011] Specifically, the steps of detecting polar components of edible oil are as follows: (1) Dissolve 1,3-bis(dicyanomethylidene)indane in ethanol to prepare a 2 mM stock solution; (2) Add the probe stock solution to the test oil sample to obtain a mixed solution. By comparing the color of the mixed solution with the colorimetric card, the content of the polar components in the edible oil can be detected by colorimetry. The UV-vis absorption intensity of the mixed solution is measured using a UV-visible spectrophotometer, and the absorbance intensity value at 582 nm is substituted into the fitting curve y of absorbance intensity and polar component content. 582 nm =0.251*e (-x / (-28.147)) -0.111, R²= 0.9822, test the content of polar components in the test oil sample; use a fluorescence spectrophotometer to measure the fluorescence intensity of the mixed solution, and substitute the fluorescence intensity value at 646 nm into the fitting curve I of fluorescence intensity and polar component content 646 nm =-10103.18*e (-x / 30.94) +12801.03, R²= 0.9959, the polar component content in the test oil sample was tested again.

[0012] The preparation method of the test oil sample in the above step (2) is: mixing the edible oil sample to be tested with n-hexane in a volume ratio of 1:5 to obtain the test oil sample.

[0013] Furthermore, the concentration of 1,3-bis(dicyanomethylidene)indane in the mixed solution of step (2) is 50 μM.

[0014] In the above step (2), when the fluorescence spectrophotometer is used for measurement, the test temperature is room temperature and the excitation wavelength is 582 nm.

[0015] A rapid detection box for polar components of edible oil comprises a detection reagent for polar components of edible oil and a cuvette, wherein the detection reagent for polar components of edible oil is a mixed solution of 1,3-bis(dicyanomethyl)indane, n-hexane and ethanol.

[0016] The specific detection method of the edible oil polar component rapid detection box is: add the soybean oil to be tested and the edible oil polar component detection reagent into the colorimetric dish, mix them and compare them with the colorimetric card, so as to realize the rapid detection of the polar component content of the edible oil.

[0017] Furthermore, the volume ratio of the above-mentioned soybean oil to be tested and edible oil polar component detection reagent is 1:5.

[0018] The beneficial effects produced by the present invention are: (1) This application proposes a new method for detecting the content of polar components in edible oils through colorimetric and fluorescence dual-channel detection based on 1,3-bis(dicyanomethylene)indane, a polarity-responsive fluorescent probe. The probe's absorbance intensity at 582 nm and fluorescence intensity at 646 nm gradually increase with the increase of the polar microenvironment, thereby achieving colorimetric and fluorescence dual-mode sensing of polarity. This method can achieve sensitive detection of polar microenvironments through colorimetric detection with the naked eye.

[0019] (2) The color of the probe in a mixed solution containing the oil sample to be tested and n-hexane at a ratio of 1:5 gradually turns blue as the polar components increase. By comparing the color of the solution with the colorimetric card, the polar components of edible oil can be detected quickly and sensitively. This method does not require any instrument to quickly detect the polar components of edible oil, and is low-cost. Therefore, it is very suitable for large-scale, on-site accurate determination of the entire chain of food production, storage, transportation, sales and consumption, such as food factories, fast food restaurants and market supervision.

[0020] (3) Quantitative detection by absorption spectrum: The method proposed in this application can accurately and quantitatively detect the content of polar components in edible oil based on the change in the absorption intensity of the fluorescent probe at 582 nm of the edible oil.

[0021] (4) Quantitative detection by fluorescence spectroscopy: The method proposed in this application can accurately and quantitatively detect the content of polar components in edible oil based on the change in the fluorescence intensity of the fluorescent probe at 646 nm of the edible oil.

[0022] (5) The detection method proposed in this application realizes dual-channel detection of colorimetry and fluorescence. No instrument is required to determine the polarity of edible oil by colorimetry under daylight. There are few operation steps, low cost, and no professional personnel are required. The result can be obtained by mixing the sample with the reagent and then comparing it with the colorimetric card. The fluorescence detection has high sensitivity and good selectivity. The fluorescence-colorimetric dual-mode detection method can improve the diversity, complementarity and synergy of the signal, and improve the flexibility, practicality and accuracy of the detection method, thereby avoiding false positive or negative errors in the results. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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.

[0024] Figure 1 Schematic diagram of the detection of polar components in edible oil.

[0025] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the fluorescent probe with polar response provided in Example 1.

[0026] Figure 3 The UV-vis absorption performance of the probe in acetonitrile / 1,4-dioxane mixtures with different ratios; (a) is the UV-vis absorption spectrum; (b) is the relationship between the acetonitrile content and the UV-vis absorption intensity at 582 nm.

[0027] Figure 4 The UV-vis absorption performance of the probe in soybean oil / n-hexane (1:5, V / V) containing different polar components; (a) is the UV-vis absorption spectrum; (b) is the relationship between the UV-vis absorption intensity at 582nm and its TPM value.

[0028] Figure 5 The fluorescence emission performance of the probe in soybean oil / n-hexane (1:5, V / V) containing different polar components; (a) is the fluorescence emission spectrum; (b) is the relationship between the fluorescence emission intensity at 646 nm and its TPM value.

[0029] Figure 6 It is the color of the probe in oil samples with different polar component contents.

[0030] Figure 7 The figure is a structural diagram of the probe edible oil polar component rapid detection box; wherein, (a) is a schematic diagram of the rapid detection box; and (b) is an instruction manual of the edible oil polar component rapid detection box. DETAILED DESCRIPTION

[0031] 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.

[0032] According to the first aspect of the present application, a fluorescent probe with polar response is provided, and its molecular formula is C 15 H6N4, the structural formula is as follows: .

[0033] According to the second aspect of the present application, the application of the above fluorescent probe in detecting polar components of frying oil: The application of the fluorescent probe in detecting polar components of frying oil comprises the following steps (e.g. Figure 1 shown): S1: dissolving the fluorescent probe in ethanol to obtain a stock solution with a probe concentration of 2 mM; S2: preparing test oil samples according to soybean oil at different frying times; S3: Take 50 μL of the probe stock solution and add it to the cuvette containing 2 mL of the above test oil sample. By comparing it with the colorimetric card, the content of polar components in the edible oil can be colorimetrically detected.

[0034] S4: Use a UV-visible spectrophotometer to measure the UV-vis absorption spectrum, substitute the absorbance intensity value at 582 nm into the fitting curve, and the quantitative detection of the polar component content in the test oil sample can be achieved.

[0035] S5: The fluorescence intensity is measured by using a fluorescence spectrophotometer, and the fluorescence intensity value at 646 nm is substituted into the fitting curve to achieve a quantitative detection of the content of polar components in the test oil sample.

[0036] In S2, first, soybean oil at different frying times is obtained and its polar component content is determined by national standard column chromatography; then, two groups of soybean oil samples with known polar components are taken and mixed in different volume ratios to obtain a group of frying oil samples with different polar component contents; finally, the frying oil samples with different polar components are respectively mixed with n-hexane in a volume ratio of 1:5 to obtain test oil samples with different polar components.

[0037] Among them, in S3, 50 μL of the probe stock solution is added to a cuvette containing 2 mL of the above-mentioned test oil sample. By comparing with the colorimetric card, the content of polar components in the edible oil can be colorimetrically detected.

[0038] Among them, in S4, the quantitative detection principle is: take 50 μL of the probe stock solution and add it to the cuvette containing 2 mL of the above test oil sample, measure its UV-vis absorption spectrum, and substitute its absorption intensity value at 582 nm into the absorbance and polar component fitting curve. The fitting curve is y 582nm =0.251*e (-x / (-28.147)) -0.111, which can realize the quantitative determination of the polar component content of edible oil.

[0039] In S5, the quantitative detection principle is as follows: 50 μL of the probe stock solution is added to a cuvette containing 2 mL of the above test oil sample, and its fluorescence intensity is measured with an excitation wavelength of 582 nm. The fluorescence intensity value at 646 nm is substituted into I 646 nm In the fitting curve of polar components, the fitting curve is I 646 nm =-10103.18*e (-x / 30.94) +12801.03, which can realize the re-quantitative determination of the polar component content of edible oil.

[0040] Based on this implementation case, the colorimetric method is simple to operate and can be distinguished by the naked eye under sunlight, which is convenient for practical application. The fluorescence of the fluorescent probe at 646 nm in the oil effectively avoids the interference of the blue-green fluorescence of the frying oil itself, and there is a high correlation between its fluorescence intensity and the content of polar components in the edible oil. The dual-mode detection of colorimetry and fluorescence makes the results more accurate, thereby realizing rapid and sensitive detection of frying oil with unknown polar components.

[0041] Example 1: Characterization of polarity-responsive probes This embodiment provides a fluorescent probe with polar response, namely 1,3-bis(dicyanomethylene)indane, whose molecular formula is C 15 H6N4, the structural formula is: . Figure 2 is the H NMR spectrum of the fluorescent probe used, where 1 H NMR (600 MHz, Chloroform-d) δ 8.70 -8.66 (m, 2H), 7.95 (dt, J = 6.1, 3.4 Hz, 2H), 4.32 (s, 2H). Example 2: Detection of probe response to solutions of different polarity Mix different volumes of acetonitrile and 1,4-dioxane to prepare acetonitrile / 1,4-dioxane mixed solutions with acetonitrile volume fractions of 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 60%, 80%, and 100%, and dissolve the probe in ethanol to obtain a stock solution with a probe concentration of 2 mM. Take 7 μL of the probe stock solution and add it to a cuvette containing 2 mL of acetonitrile / 1,4-dioxane system. Figure 3Figure a shows the UV-vis absorption spectra of the probe in different ratios of acetonitrile / 1,4-dioxane mixtures. It can be seen from the figure that the probe has two absorption peaks at 346 nm and 582 nm. And as the polarity of the solution changes, the intensity of the two absorption peaks will change. The relationship between the acetonitrile content of the probe in different ratios of acetonitrile / 1,4-dioxane mixtures and the UV-vis absorption intensity at 582 nm is shown in the figure. Figure 3 As shown in Figure b, as the acetonitrile content increases, the absorbance at 582 nm gradually increases, first increasing and then tending to be flat.

[0042] Example 3: Application of probe to detect polar component content of edible oil (1) Preparation of oil samples with different polar component contents: First, soybean oils were obtained at different frying times and their polar component contents were determined by national standard column chromatography; then, two groups of soybean oil samples with known polar components were obtained and mixed in different volume ratios to obtain a group of frying oil samples with different polar component contents, and test oil samples with different polar components were prepared. The polar component contents of soybean oil were 1.1%, 6.1%, 13.9%, 21.5%, 26.9%, and 29.3%, respectively. Soybean oils of different polarity groups were mixed with n-hexane at a volume ratio of 1:5 to prepare test oil samples with different polar components.

[0043] (2) Sample detection: Take 2 mM and 50 μL of ethanol stock solution and add them into the cuvette containing 2 mL of the above test oil sample. After thorough mixing, the following results can be obtained: Figure 6 The color change shown in the figure is obtained by taking a photo with a mobile phone. When actually testing the oil sample, the test oil sample can be replaced with the actual test oil sample, and the color in the cuvette is compared with the colorimetric card. For example, when the newly purchased soybean oil is used as the actual oil sample and tested according to the above method, its color is similar to the color when the TPM on the colorimetric card is 1.1%, and the TPM value of the newly purchased soybean oil is around 1%, indicating that its colorimetric detection accuracy is high.

[0044] (3) Sample detection: Take 50 μL of 2 mM ethanol stock solution and add it to a cuvette containing 2 mL of the above oil sample to measure the UV-vis absorption spectrum. Figure 4 Figure a is the UV-vis absorption spectrum of the probe in soybean oil / n-hexane (1:5, V / V) containing different polar components. It can be seen from the figure that the absorption peak of the probe in soybean oil is at 582 nm, and as the content of polar components in soybean oil increases, the intensity of its absorption peak increases. The relationship between the TPM value of soybean oil with different polar component contents and the absorption intensity at 582 nm is fitted, and the results are shown in Figure 2. Figure 4As shown in Figure b. It can be seen that there is a high correlation between the TPM value of soybean oil with different polar component contents and the absorption intensity at 582 nm: the linear equation is: 582nm =0.251*e (-x / (-28.147)) -0.111 , R²=0.9822.

[0045] (4) Sample detection: Take 50 μL of 2 mM ethanol stock solution and add it to a cuvette containing 2 mL of the above oil sample to be tested, and measure the fluorescence intensity at 582 nm. Figure 5 As shown in Figure a, as the content of polar components in soybean oil increases, the fluorescence intensity of the probe at 646 nm gradually increases, and there is a highly good relationship. Figure 5 As shown in Figure b, there is a high correlation between the TPM value of soybean oil with different polar component contents and the fluorescence emission peak at 646 nm, where R²=0.9959, and the linear equation is: 646nm =-10103.18*e (-x / 30.94) +12801.03.

[0046] Example 4: Basic structure design of edible oil polar component rapid detection box A rapid detection box for polar components of edible oil, the structural composition diagram of which is shown in Figure 7 As shown in Figure a. It includes three cuvettes, a polar component detection reagent for edible oil, a pipette, and an instruction manual. The polar component detection reagent for edible oil is a mixed solution of 1,3-bis(dicyanomethylene)indane, n-hexane, and ethanol (the concentration of 1,3-bis(dicyanomethylene)indane in the mixed solution is 60 μM, and the volume ratio of n-hexane to ethanol is 32:1). The specific detection method is: add 0.5 mL of soybean oil to be tested into the cuvette, and then add 2.5 mL of the polar component detection reagent for edible oil. After thorough mixing, Figure 6 The test results are obtained by comparing with the corresponding colorimetric card paper, and the observation time is based on one minute. Figure 7 Instructions for Figure b.

[0047] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0048] 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. Application of 1,3-bis(dicyanomethylene)indane in the detection of polar components in edible oils.

2. The use according to claim 1, characterized in that: The 1,3-bis(dicyanomethylidene)indane detects polar components of edible oil through colorimetric and fluorescent dual channels.

3. The use according to claim 2, characterized in that: The steps of detecting the polar components of edible oil are: (1) Dissolve 1,3-bis(dicyanomethylidene)indane in ethanol to prepare a stock solution; (2) Add the probe stock solution to the test oil sample to obtain a mixed solution; compare the color of the mixed solution with a colorimetric card or use a spectrophotometer to measure the intensity value of the mixed solution at the peak, and substitute this intensity value into the working curve to achieve quantitative detection of the content of polar components in the test oil sample.

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

5. The use according to claim 4, characterized in that: The preparation method of the test oil sample in step (2) is: mixing the edible oil sample to be tested with n-hexane in a volume ratio of 1:5 to obtain the test oil sample.

6. The use according to claim 4, characterized in that: The concentration of 1,3-bis(dicyanomethyl)indane in the mixed solution of step (2) is 50 μM.

7. The use according to claim 6, characterized in that: When the spectrophotometer is a UV-visible spectrophotometer, the intensity value at the peak is the absorbance intensity value at 582 nm; the working curve is y 582 nm =0.251*e (-x / (-28.147)) -0.111, R² = 0.9822.

8. The use according to claim 6, characterized in that: When the spectrophotometer is a fluorescence spectrophotometer, the test temperature is room temperature, the excitation wavelength is 582 nm, and the intensity value at the peak is the fluorescence intensity value at 646 nm; the working curve is I 646 nm =-10103.18*e (-x / 30.94) +12801.03, R² = 0.9959.

9. A rapid detection box for polar components of edible oil, comprising a detection reagent for polar components of edible oil and a cuvette, characterized in that: The edible oil polar component detection reagent is a mixed solution of 1,3-bis(dicyanomethylidene)indane, n-hexane and ethanol.

10. The edible oil polar component rapid detection box according to claim 9, characterized in that: The specific detection method is: add the soybean oil to be tested and the edible oil polar component detection reagent into the colorimetric dish, mix them and compare them with the colorimetric card, so as to realize the rapid detection of the polar component content of the edible oil.

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