Rapid visualization method for detecting vanillic acid and alkyl resorcinol in eutectic solvent

Abstract

The invention relates to the technical field of cereal functional factor detection, and discloses a method for realizing cereal functional factor detection in a deep eutectic solvent. Specifically, the invention discloses a rapid visualization method for detecting vanillic acid and alkyl resorcinol in a deep eutectic solvent, the deep eutectic solvent synthesized by choline chloride-urea is used as a green solvent to construct a detection system, and a diazonium salt compound is used as a probe. The diazonium salt compound has good solubility and stability in a deep eutectic solvent, can be chemically reacted with vanillic acid and alkyl resorcinol to generate azo compounds with different structures, causes the change of optical characteristics, presents a remarkable visual effect, and has good application prospects. Therefore, the specific detection of the vanillic acid and the alkyl resorcinol in the eutectic solvent is realized. The detection method provided by the invention is green, efficient, stable and sensitive, has the characteristic of visualization, is suitable for actual samples, and is convenient to apply.

Description

Technical Field

[0001] The present invention relates to the technical field of detection of cereal functional factors, and specifically discloses a rapid visualization detection method for vanillic acid and alkylresorcinols by constructing a detection system based on DES and using a diazonium salt compound as a probe. Background Art

[0002] China ranks first in the world in terms of the variety and output of whole grains. With the increasing health awareness of consumers, the acceptance of whole grain foods is also increasing. Research shows that the health effects of whole grains can be attributed to the various phenolic substances rich in whole grains and their products, which have a positive preventive effect on chronic diseases.

[0003] Alkylresorcinols are amphiphilic phenolic lipids in which the 5-position of the benzene ring of 1,3-resorcinol is substituted by a long-chain alkyl group, and have various physiological functions such as antioxidant, antibacterial and bacteriostatic, anti-radiation, tumor inhibition, and neuroprotective effects. The cortex of wheat cereals is the main biological source of alkylresorcinols, among which rye and wheat have the highest content, and the content in refined wheat flour can be ignored. Therefore, alkylresorcinols can be used as dietary biomarkers for whole grain intake and have been frequently used to evaluate the association between whole grains and cancer risk.

[0004] Vanillic acid is a hydroxybenzoic acid phenolic acid, which is widely present in the cortex of gramineous cereals such as wheat, corn, oats, quinoa, and some foods such as fruits, green tea, beer and wine. It has functions such as analgesia, anti-inflammatory, antibacterial and antioxidant, and has a positive effect on cancer, diabetes, obesity, chronic intestinal inflammation, neurodegenerative diseases, cardiovascular diseases and liver diseases. It is usually used in pharmaceuticals, cosmetics and food flavorings.

[0005] Natural deep eutectic solvents synthesized from components existing in nature and acting in living cells, as a non-toxic and biodegradable green solvent, can not only increase the biological activity and stability of extracts, but also improve the stability of substances in them and extend the storage time.

[0006] At present, the market of whole grain products based on whole wheat flour is uneven. Developing an efficient analysis method for alkylresorcinols is an effective way to improve the standard system and achieve rapid authenticity identification. The content of vanillic acid varies greatly in different cereals, and it can be used as a flavoring and preservative for foods. At the same time, it is also an active ingredient of some drugs. It is necessary to develop a suitable analysis method to effectively detect and quantify the content of vanillic acid in complex matrices. Therefore, establishing a product standard system for whole grains and related products for bioactive substances such as alkylresorcinols and vanillic acid is the key link to solve the uneven product quality and the bottleneck of industrial development.

[0007] Therefore, using the deep eutectic solvent synthesized from choline chloride-urea as a green solvent to detect vanillic acid and alkylresorcinols in it is of great significance for maintaining market order and enhancing the health benefits of whole grain diet intake. Summary of the Invention

[0008] In view of this, the technical problem to be solved by the present invention is to provide a rapid visual detection method for vanillic acid and alkylresorcinols in a deep eutectic solvent, without using organic reagents as the extraction and detection environment, overcoming the defects such as pollution, high operation requirements, and low detection efficiency existing in the existing detection methods.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] First, the present invention provides the application of using the deep eutectic solvent synthesized from choline chloride-urea to construct a detection system, and using the naphthyl diazonium salt shown in formula (I) and the pyrenyl diazonium salt shown in formula (II) as probes to detect vanillic acid and alkylresorcinols in DES respectively:

[0011]

[0012] The naphthyl diazonium salt with the structure shown in formula (I) and the pyrenyl diazonium salt with the structure shown in formula (II) above have good solubility in the choline chloride-urea deep eutectic solvent, and can achieve high-sensitivity and specific detection of vanillic acid and alkylresorcinols in grains, showing obvious specificity and anti-interference ability in the detection.

[0013] The naphthyl diazonium salt shown in formula (I) and the pyrenyl diazonium salt shown in formula (II) of the present invention can respectively undergo diazotization reactions with vanillic acid and alkylresorcinols in DES to generate different azo compounds, and then the maximum absorption wavelength of ultraviolet-visible light changes, resulting in changes in optical properties. In the case of being visible to the naked eye, a significant color change occurs in the detection system constructed by DES, and this visualization effect can remain stable in the DES system.

[0014] Therefore, when the above detection system constructed by the deep eutectic solvent synthesized from choline chloride-urea is used for the detection of vanillic acid and alkylresorcinols in grains, it can maintain the effect of stable optical property changes, that is, the generated different azo compounds can remain stable in DES.

[0015] Moreover, the detection limit of the naphthyl diazonium salt for vanillic acid in the choline chloride-urea deep eutectic solvent is as low as 0.703 μmol / L, and the detection limit of the pyrenyl diazonium salt for alkylresorcinols in the choline chloride-urea deep eutectic solvent is as low as 0.281 μmol / L, and the visualization effect is obvious in the detection system constructed by DES.

[0016] The present invention has no special limitation on the sources of the two compounds, choline chloride and urea, and they can be commercially available generally.

[0017] To obtain high-quality and stable DES and use DES (10% H 2 O, v / v) as the detection system, the present invention provides a preferred preparation method for preparing DES as described below. Specifically:

[0018] Second, the present invention provides a preparation method for the above-mentioned DES, including the following steps:

[0019] (1) Calculate the masses of choline chloride solid and urea solid according to a molar ratio of 1:2, weigh and mix them evenly, and synthesize stable colorless and transparent DES by stirring and heating for 1.5 hours. The state of DES does not change after being placed at room temperature of 25 °C for 24 hours;

[0020] (2) Calculate the volumes of DES and pure water according to DES:H 2 O = 9:1 (v / v), add water to DES in portions, dropwise add and mix simultaneously until 10% H 2 O (v / v) is added to DES, and use it after fully mixing evenly;

[0021] The present invention has no special limitation on the sources of choline chloride and urea, and they can be commercially available generally.

[0022] Preferably, the conditions for the contact reaction in (1) include: mixing and stirring for 1.5 hours, the stirring and heating temperature is 80 °C, and the prepared DES is stored at room temperature of 25 °C.

[0023] Preferably, the conditions for the contact reaction in (2) include: slowly adding 10% H 2 O (v / v) to DES in a dropwise manner, adding and mixing simultaneously, and the prepared DES (10% H 2 O, v / v) is stored at room temperature of 25 °C.

[0024] Third, the present invention provides a reagent, test paper or kit for a rapid visualization method for detecting vanillic acid and alkylresorcinols in a deep eutectic solvent, including using the DES synthesized from choline chloride and urea as described above as a solvent to construct a detection system, and using naphthyl diazonium salt and pyrenyl diazonium salt as probes to achieve detection in DES (10% H 2 O, v / v).

[0025] Fourth, the present invention provides a rapid visualization method for detecting vanillic acid and alkylresorcinols in a deep eutectic solvent. Specifically, the present invention provides a rapid visualization method for detecting vanillic acid and alkylresorcinols in a deep eutectic solvent, using the above-mentioned DES and DES (10% H 2O, v / v) or DES and DES (10% H prepared by the above preparation method 2 O, v / v) to construct a detection system, and a diazonium salt compound is used as a probe and dissolved in the detection system to achieve detection.

[0026] Preferably, the concentration of the probe in the present invention is 90-110 μmol / L of naphthyl diazonium salt and 15-25 μmol / L of pyrenyl diazonium salt. The concentration of the probe is further preferably 100 μmol / L of naphthyl diazonium salt and 20 μmol / L of pyrenyl diazonium salt.

[0027] The specific detection method of the present invention is preferably as follows: Choline chloride and urea are mixed in a molar ratio of 1:2, stirred and heated at 80 °C to form a homogeneous and clear deep eutectic solvent (DES), and maintained in a stable state at 25 °C room temperature. In DES with 10% (volume ratio) water added, the above probe concentrations are 100 μmol / L of naphthyl diazonium salt and 20 μmol / L of pyrenyl diazonium salt, and spectroscopic tests of vanillic acid and alkylresorcinols are carried out respectively. When detecting vanillic acid with naphthyl diazonium salt in DES, with the concentration of vanillic acid as the abscissa and the absorbance at the absorption wavelength of 480 nm as the ordinate, a detection standard curve is established. When detecting alkylresorcinols with pyrenyl diazonium salt in DES, with the concentration of alkylresorcinols as the abscissa and the absorbance at the absorption wavelength of 512 nm as the ordinate, a detection standard curve is established. In DES (10% H 2 O, v / v), the above probe concentrations are 100 μmol / L of naphthyl diazonium salt and 20 μmol / L of pyrenyl diazonium salt for the visual detection of vanillic acid and alkylresorcinols, and a visually recognizable color change occurs in the detection system constructed by DES under a fluorescent lamp.

[0028] Compared with the prior art, the present invention provides a rapid visualization method for detecting vanillic acid and alkylresorcinols in a deep eutectic solvent. A detection system is constructed based on DES synthesized from choline chloride and urea in a molar ratio of 1:2, and a diazonium salt compound is used as a probe to achieve stable and efficient detection. The above diazonium salt compound probe and the azo compound after color transformation both have good solubility and stability in DES, and can achieve highly sensitive and specific detection of vanillic acid and alkylresorcinols in the deep eutectic solvent. The detection method provided by the present invention is green, efficient, stable, sensitive, and has the characteristic of visualization, is suitable for actual samples, and is convenient to apply. Description of the Drawings

[0029] Figure 1 For naphthyl diazonium salt probe and pyrenyl diazonium salt in DES (10% H 2 UV-visible absorption spectra before and after the reaction of O, v / v) with vanillic acid and alkylresorcinols respectively

[0030] Figure 2 The change in absorbance at 480 nm of the naphthyl diazonium salt probe after adding different concentrations of vanillic acid in DES (10% H 2 O, v / v);

[0031] Figure 3 The change in absorbance at 512 nm of the pyrene diazonium salt probe after adding different concentrations of alkylresorcinol in DES (10% H 2 O, v / v);

[0032] Figure 4 The ratio of absorbance at 480 nm to that at 462 nm of the naphthyl diazonium salt probe in DES (10% H 2 O, v / v) when interacting with different substances (1 - blank, 2 - vanillic acid, 3 - glucose, 4 - linoleic acid, 5 - vitamin E, 6 - valine, 7 - phenylalanine, 8 - leucine, 9 - Al 3+ , 10 - Fe 3+ , 11 - Cu 2+ , 12 - Zn 2+ , 13 - Mn 2+ , 14 - Ca 2+ , 15 - Mg 2+ , 16 - Na + , 17 - Cl - , 18 - NO 3- , 19 - CH 3 COO - );

[0033] Figure 5 The ratio of absorbance at 512 nm to that at 463 nm of the pyrene diazonium salt probe in DES (10% H 2 O, v / v) when interacting with different substances (1 - blank, 2 - C17:0, 3 - glucose, 4 - linoleic acid, 5 - vitamin E, 6 - valine, 7 - phenylalanine, 8 - leucine, 9 - Al 3+ , 10 - Fe 3+ , 11 - Cu 2+ , 12 - Zn 2+ , 13 - Mn 2+ , 14 - Ca 2+ , 15 - Mg 2+ , 16 - Na + , 17 - Cl - , 18 - NO 3- , 19 - CH 3 COO - );

[0034] Figure 6 The change in absorbance at 480 nm of the naphthyl diazonium salt probe after adding different concentrations of vanillic acid in DES (10% H 2The color change of naphthyl diazonium salt probe in (0, v / v) after reacting with different concentrations of vanillic acid is visible to the naked eye;

[0035] Figure 7 DES (10% H 2 Figure 2. The color change of the pyrene diazonium salt probe in the reaction with different concentrations of alkylresorcinol (V / V) was visible to the naked eye. DETAILED DESCRIPTION

[0036] To further illustrate the present invention, a rapid visualization method for detecting vanillic acid and alkylresorcinol in a deep eutectic solvent provided by the present invention is described in detail below in conjunction with examples.

[0037] It is worth noting that the raw materials used in the present invention are all common commercial products, and their sources are not specifically limited. The present invention is described in detail below in conjunction with specific embodiments.

[0038] Preparation of spare materials:

[0039] Preparation of low eutectic solvent: Weigh appropriate amount of solids of choline chloride and urea in a molar ratio of 1:2, mix thoroughly, and heat with stirring at 80°C for 1.5h to form a homogeneous and clear low eutectic solvent, which remains stable at room temperature of 25°C; add 10% by volume of pure water during the detection process, mix thoroughly to form a homogeneous liquid. The above liquids are all stored at room temperature for future use.

[0040] Preparation of naphthyl diazonium salt mother solution: Weigh the solid represented by formula (I) and prepare a mother solution with a concentration of 1 mmol / L. Leave it at room temperature for 1 hour and then perform spectral testing.

[0041] Preparation of pyrene diazonium salt mother solution: Weigh the solid represented by formula (II) to prepare a mother solution with a concentration of 1 mmol / L, and store it in a refrigerator at 4°C for use. The storage time shall not exceed 5 days.

[0042] Preparation of test substances and interfering substances: Vanillic acid and alkylresorcinol were prepared into stock solutions with concentrations of 6mmol / L, 1mmol / L and 0.2mmol / L with ethanol for later use. Other interfering substances were prepared into stock solutions with 6mmol / L with ethanol or distilled water. These solutions were stored in a refrigerator at 4℃ for later use.

[0043] Preparation of actual samples: Black whole wheat flour and corn flour were purchased from Beijing Wumart Supermarket, and a low eutectic solvent (10% H 2 O, v / v) in a centrifuge tube, add black whole wheat flour or corn flour, with a liquid-to-solid ratio of 15 mL / g, oscillate to mix, ultrasonicate at 35 °C for 10 min and oscillate for 3 min, repeat 4 times, then centrifuge at 4000 g for 15 min, and use the obtained supernatant for the experiment.

[0044] Example 1

[0045] Synthesis and preparation of DES(10% H 2 O, v / v)

[0046] Weigh the choline chloride solid and urea solid according to the molar ratio of 1:2, mix them evenly after weighing, and synthesize a stable colorless and transparent DES by stirring and heating for 1.5 hours. The state of DES does not change after being placed at room temperature of 25°C for 24 hours.

[0047] Calculate the volume of DES and pure water according to the ratio of DES:H 2 O = 9:1 (v / v). Add water to DES in portions, mix while dripping until 10% H 2 O (v / v) is added to DES. After mixing evenly, it can be used.

[0048] The prepared DES and DES(10% H 2 O, v / v) are both stored at room temperature of 25°C.

[0049] Example 2

[0050] UV-Visible Absorption Spectroscopy Test of Naphthyl Diazonium Salt for Detecting Vanillic Acid :

[0051] Take 100 μL of the naphthyl diazonium salt mother liquor and 900 μL of DES(10% H 2 O, v / v), mix them and add them to a 1 mL sample cell. After mixing evenly, measure the fluorescence spectrum of the probe P1 in the detection system constructed by DES, and record the absorbance at a wavelength of 462 nm. Subsequently, gradually add a certain concentration gradient of vanillic acid (VA) to the sample cell. After mixing evenly, measure the corresponding ultraviolet-visible absorption spectrum in the DES system and record the absorbance at 480 nm. The results are shown in Appendix Figure 1 、 2 as follows.

[0052] The results are as shown in Figure 1 、 2 (that is, Figure 1 represents the ultraviolet-visible absorption spectra of the naphthyl diazonium salt probe and pyrene diazonium salt in DES(10% H 2 O, v / v) before and after reacting with vanillic acid and alkyl resorcinol respectively; Figure 2 represents the change in the absorbance of the naphthyl diazonium salt probe at 480 nm after adding different concentrations of vanillic acid in DES(10% H 2 O, v / v)).

[0053] The experimental results show that in the detection system constructed by DES, the naphthyl diazonium salt has a relatively low absorbance at 480 nm. With the addition of vanillic acid, the maximum absorption wavelength of the naphthyl diazonium salt undergoes a red shift, and the absorbance at 480 nm gradually increases. As the concentration of vanillic acid continues to increase, the absorbance of the naphthyl diazonium salt at 480 nm gradually stops changing and reaches saturation. According to the detection limit calculation method recommended by IUPAC, the detection limit of the naphthyl diazonium salt probe for vanillic acid in the detection system constructed by DES is 0.703 μmol / L.

[0054] Figure 6 Figure is a photo taken under sunlight after adding different concentrations of vanillic acid to the detection system constructed by DES. It can be seen that as the concentration of vanillic acid increases, the color of the corresponding solution changes significantly from light brown to orange. The results show that the detection results of this method can achieve clear visual inspection with the naked eye.

[0055] UV-Visible Absorption Spectroscopy Test of Pyrenyl Diazonium Salt for Detecting Alkylresorcinol :

[0056] Take 20 μL of the pyrenyl diazonium salt mother liquor and 980 μL of DES (10% H 2 O, v / v) and mix them into a 1 mL sample cell. After mixing evenly, measure the fluorescence spectrum of probe P2 in the detection system constructed by DES, and record the absorbance at a wavelength of 463 nm. Subsequently, gradually add a certain concentration gradient of alkylresorcinol (C17:0) to the sample cell. After mixing evenly, measure the corresponding ultraviolet-visible absorption spectrum in the DES system and record the absorbance at 512 nm. The results are shown in Figure 1 、 3 .

[0057] The results are shown in Figure 1 、 3 (that is, Figure 1 represents the ultraviolet-visible absorption spectra of the naphthyl diazonium salt probe and the pyrenyl diazonium salt in DES (10% H 2 O, v / v) before and after reacting with vanillic acid and alkylresorcinol respectively; Figure 3 represents the change in the absorbance of the pyrenyl diazonium salt probe at 512 nm after adding different concentrations of alkylresorcinol in DES (10% H 2 O, v / v)).

[0058] The experimental results show that in the detection system constructed with DES, the pyrene-based diazonium salt hardly absorbs light waves at 512 nm. With the addition of alkylresorcinol, the maximum absorption wavelength of the pyrene-based diazonium salt undergoes a red shift, and the absorbance at 512 nm gradually increases. As the concentration of alkylresorcinol continuously increases, the absorbance of the pyrene-based diazonium salt at 512 nm gradually no longer changes and reaches saturation. According to the detection limit calculation method recommended by IUPAC, the detection limit of the pyrene-based diazonium salt probe for alkylresorcinol in the detection system constructed with DES is 0.281 μmol / L.

[0059] Figure 7 Figure shows the photos taken under sunlight after adding different concentrations of alkylresorcinol to the detection system constructed with DES. It can be seen that as the concentration of alkylresorcinol increases, the color of the corresponding solution changes significantly from yellow to red. The results show that the detection results of this method can achieve clear visual inspection by the naked eye.

[0060] Example 3

[0061] Selectivity Study:

[0062] The common interfering substances selected when detecting vanillic acid and alkylresorcinol include common anions, cations, and other interfering substances, such as glucose, linoleic acid, vitamin E, valine, phenylalanine, leucine, Al 3+ 、Fe 3+ 、Cu 2+ 、Zn 2+ 、Mn 2+ 、Ca 2 + 、Mg 2+ 、Na + 、Cl - 、NO 3- 、CH 3 COO - .

[0063] When detecting vanillic acid in the detection system constructed with DES, the concentration of the aforementioned naphthalene-based diazonium salt is 100 μmol / L; when detecting alkylresorcinol in the detection system constructed with DES, the concentration of the aforementioned pyrene-based diazonium salt is 20 μmol / L. The concentration of the interfering substance is 60 μmol / L, and ultraviolet-visible absorption spectroscopy tests are carried out under the same test conditions. For vanillic acid, after adding the interfering substance, the ratio of the absorbance of the probe at 480 nm to the absorbance of the naphthalene-based diazonium salt at its own absorption peak of 462 nm is used as a parameter to measure the influence degree of the probe on the analyte; for alkylresorcinol, after adding the interfering substance, the ratio of the absorbance of the probe at 512 nm to the absorbance at 463 nm is used as a parameter to measure the influence degree of the probe on the analyte. The results are shown in Appendix Figure 4 and 5 . Figure 4 、 5As shown. (That is, Figure 4 represents the absorbance ratio at 480 nm and 462 nm when the naphthyl diazonium salt probe reacts with different substances in DES (10% H 2 O, v / v); Figure 5 represents the absorbance ratio at 512 nm and 463 nm when the pyrene diazonium salt probe reacts with different substances in DES (10% H 2 O, v / v)).

[0064] It can be seen from the appendix Figure 4 that the A 480 / A 462 value of vanillic acid is significantly and stably higher than that of other interferents; it can be seen from 480 / A 462 that the A Figure 5 / A 512 value of alkylresorcinol is significantly and stably higher than that of other interferents. 463 This result indicates that the aforementioned naphthyl diazonium salt probe has excellent selectivity for vanillic acid and the aforementioned pyrene diazonium salt has excellent selectivity for alkylresorcinol in the detection system constructed by DES. 512 / A 463 value.

[0065] Example 4

[0066] Application of Actual Samples :

[0067] Corn flour was selected as the actual sample for the rapid visual detection of vanillic acid. The spiking amounts were as follows: Spiking 1: Add a quantitative (1 μM, 3 μM, 5 μM) standard product to the DES detection system after extracting the actual sample for detection; Spiking 2: Add a quantitative (200 μg / g, 400 μg / g, 600 μg / g) standard product to the actual sample for extraction, and then perform detection in the DES system.

[0068] Black whole wheat flour was selected as the actual sample for the rapid visual detection of alkylresorcinol. The spiking amounts were as follows: Spiking 1: Add a quantitative (5 μM, 10 μM, 20 μM) standard product to the DES detection system after extracting the actual sample for detection; Spiking 2: Add a quantitative (200 μg / g, 500 μg / g, 900 μg / g) to the actual sample, and then perform detection in the DES system.

[0069] Table 1

[0070]

[0071] As shown in Table 1, the present invention uses a deep eutectic solvent to rapidly and visually detect vanillic acid and alkylresorcinols without using organic solvents. The accuracy of the spike recovery rate in the actual sample is relatively high, and the RSDs are all less than 3%, indicating that the detection system constructed by the present invention using DES can achieve rapid, accurate, and visual detection of vanillic acid and alkylresorcinols under actual conditions.

[0072] From the above results, it can be seen that the present invention uses DES to construct a detection system, and combining a diazonium salt compound as a probe can achieve highly sensitive and specific rapid visual detection of vanillic acid and alkylresorcinols.

[0073] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. The technical solution of the present invention is not limited to the technical means disclosed by the above technical means, but also includes the technical solutions composed of any combination of the above technical features. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. An application of a low eutectic solvent (DES) formed by choline chloride and urea as a solvent in the detection of vanillic acid and alkylresorcinol in grains.

2. A rapid visualization method for detecting vanillic acid and alkylresorcinol in a deep eutectic solvent, characterized in that: A deep eutectic solvent (DES) formed by choline chloride and urea is used as a solvent, and a naphthyl diazonium salt represented by formula (I) and a pyrene diazonium salt represented by formula (II) are used as probes; 3. The method according to claim 2, characterized in that The synthesis conditions of the DES are as follows: choline chloride and urea are mixed in a molar ratio of 1:2, and then stirred and heated to synthesize a stable, colorless and transparent DES, which remains stable at room temperature of 25°C.

4. The method according to claim 2, characterized in that: The use condition of the DES is DES: H2O = 9:1 (v / v). When using, 10% volume ratio of water is added to the DES and the mixture is fully mixed before use. The use concentration of the naphthyl diazonium salt represented by formula (I) in DES is 90-110 μmol / L, and the use concentration of the pyrene diazonium salt represented by formula (II) in DES is 15-25 μmol / L.

5. A reagent, test paper or kit for a rapid visualization method for detecting vanillic acid and alkylresorcinol in a deep eutectic solvent, characterized in that: The method includes constructing a detection system using a low eutectic solvent (DES) formed by choline chloride and urea as a solvent.

6. The use according to claim 1, or the method according to any one of claims 2 to 4, or the reagent, test paper or kit according to claim 5, characterized in that: The DES is prepared according to the following method: Choline chloride and urea solids are weighed and mixed evenly in a molar ratio of 1:2, and stirred and heated at 80°C to form a stable, uniform, colorless and transparent DES. If the state of DES does not change when placed at room temperature of 25°C for 24 hours, the synthesis of DES is completed, and DES is stored at room temperature of 25°C.

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