Method for detecting ethephon in fruits and vegetables by using fluorescent COF material and application

Abstract

The invention provides a method for detecting ethephon in fruits and vegetables by using a fluorescent COF material and application, and belongs to the technical field of pesticide detection. According to the fluorescent COF material provided by the invention, 1, 3, 5-tri (4-aminophenyl) benzene (TAPB) and a solution of 2, 5-dimethoxy terephthalaldehyde (DMTP) are subjected to a condensation reaction under the action of adding glacial acetic acid, and the covalent organic framework material is obtained. Research finds that the covalent organic framework material can be used for specific detection of ethephon. The invention also provides a method for rapidly detecting ethephon, which takes the fluorescent COF material as a fluorescent probe, and constructs a COF-based ethephon fluorescent rapid detection method according to the fluorescence intensity measured after incubation of ethephon with different concentrations and the COF material, so as to realize rapid and sensitive detection of ethephon residues. The defects that existing ethephon detection depends on bio-enzyme and is poor in stability, low in sensitivity and the like can be overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of pesticide detection, and particularly relates to a method for detecting ethephon in fruits and vegetables based on fluorescent COF materials. Background Art

[0002] Ethephon is a widely used plant growth regulator that works by releasing ethylene in plants, accelerating the maturation, shedding and aging of crops. In recent years, tropical fruits such as mangoes are inevitably sprayed with a certain amount of ethephon for ripening before they are put on the market. However, improper use of ethephon may lead to toxic enrichment and excessive residues in crops, posing a major threat to food safety and environmental health. The detection of ethephon residues has become an important item in food safety monitoring. Therefore, it is of great significance to achieve on-site and real-time detection of ethephon. Traditional detection methods such as gas chromatography and liquid chromatography have problems such as high professional requirements for operators, long detection time, and high cost of large-scale specialized equipment, which are difficult to meet the needs of on-site and real-time detection.

[0003] The existing new rapid detection technology of ethephon mainly focuses on the detection of ethephon by gold nanoparticle-loaded molecular imprinting switch sensors. Although these methods have made up for the shortcomings of instrumental analysis methods to a certain extent, they also have shortcomings. For example, the gold nanoparticle-loaded molecular imprinting switch sensor requires precise control of reaction conditions during the preparation process, which increases the difficulty and cost. The shedding, deformation and aging of the membrane layer will affect the reliability of the sensor. Due to the large interface resistance between the gold nanoparticles and the molecular imprinting polymer or the poor electron transfer path, the sensor response speed slows down or the signal attenuates, resulting in a decrease in the sensitivity of ethephon detection and inaccurate detection. Therefore, it is urgent to provide a new ethephon detection method with good stability and fast response speed. Summary of the invention

[0004] One object of the present invention is to provide a method for preparing a fluorescent covalent organic framework (COF) material and its application. Another object of the present invention is to provide a method for rapidly detecting ethephon in fruits and vegetables using the fluorescent COF material.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a fluorescent COF material comprises the following steps: subjecting a solution of 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 2,5-dimethoxyterephthalaldehyde (DMTP) to a condensation reaction under the action of glacial acetic acid to obtain a fluorescent covalent organic framework (COF) material (TAPB-DMTP-COF).

[0007] According to the preparation method described above, the solvent of the solution is acetonitrile, the addition ratio of 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 2,5-dimethoxyterephthalaldehyde (DMTP) is 5:4 by mass, the amount of 1,3,5-tris(4-aminophenyl)benzene (TAPB) and acetonitrile is added in a ratio of 1:1 to 2 in units of mg:ml, the amount of 2,5-dimethoxyterephthalaldehyde and acetonitrile is added in a ratio of 3:5 to 6 in units of mg:ml, and the amount of glacial acetic acid is 35 to 50:1 in volume ratio of acetonitrile: glacial acetic acid.

[0008] In the preparation method described above, the condensation reaction after adding glacial acetic acid is stirred at room temperature for 6 to 8 hours. Further, after the reaction, centrifugation is performed, washing is performed three times with ethanol, and drying is performed in a vacuum drying oven at 60 to 80° C. for 8 to 12 hours to collect the yellow powder product TAPB-DMTP-COF.

[0009] Application of the TAPB-DMTP-COF obtained by the above preparation method in preparing a kit for detecting ethephon. A kit for detecting ethephon, comprising the TAPB-DMTP-COF obtained by the above preparation method.

[0010] Application of TAPB-DMTP-COF obtained by the preparation method described above in the detection of ethephon.

[0011] A method for rapidly detecting ethephon in fruits and vegetables comprises the following steps:

[0012] S1, dissolving TAPB-DMTP-COF powder in water to obtain an aqueous solution of TAPB-DMTP-COF;

[0013] S2, diluting the standard substance ethylene with water to prepare a series of standard solutions with concentration gradients;

[0014] S3, after incubating the aqueous solution of TAPB-DMTP-COF with the standard solution, the fluorescence signal is read using a fluorescence spectrophotometer to establish a linear relationship between the ethephon concentration and the fluorescence signal;

[0015] S4, preparing a test solution from the fruit and vegetable sample, mixing the test solution with the aqueous solution of TAPB-DMTP-COF for incubation reaction, and reading the fluorescence signal with a fluorescence spectrophotometer;

[0016] Substituting the obtained fluorescence signal of the sample to be tested into the linear relationship can obtain the concentration of ethephon in the sample to be tested.

[0017] In the method as described above, preferably, in step S1, the concentration of the aqueous solution of TAPB-DMTP-COF is 0.6 mg / L; in step S3, the aqueous solution of TAPB-DMTP-COF and the standard solution are added in a volume ratio of 1:1.

[0018] In the method as described above, preferably, in step S2, the standard solution is a series of standard solutions with a concentration gradient diluted by 2 times or 4 times, such as 0, 10, 20, 50, 100 mg / L, etc.

[0019] In the method as described above, preferably, in step S3, the incubation reaction time is 20 to 40 minutes; the fluorescence signal is read at the fluorescence intensity at an excitation wavelength of 400 nm, an emission wavelength of 520 nm, and a slit width of 5 nm.

[0020] The beneficial effects of the present invention are:

[0021] The invention provides a method for preparing a fluorescent COF material. The method comprises the following steps: respectively adding 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxyterephthalaldehyde into acetonitrile to dissolve the two solutions, mixing the two solutions and dripping a certain amount of glacial acetic acid to prepare a fluorescent material: TAPB-DMTP-COF. The prepared fluorescent COF material has the advantages of high aperture ratio and high specific surface area. The rich imine structures in the material enable TAPB-DMTP-COF to have pH response characteristics and exhibit excellent fluorescence performance. The material can realize fluorescence rapid detection of ethephon residues through specific fluorescence recognition of ethephon, thereby effectively improving the detection efficiency. Therefore, the obtained fluorescent COF material can be used for the detection of pesticide residues.

[0022] The present invention also provides a new use of the fluorescent COF material, which can be used for fluorescent detection of pesticide residues. The fluorescent signal generated by the COF's specific fluorescent recognition of ethephon is enhanced, and based on the sensitivity curve of the concentration of the ethephon residue and the fluorescent signal of TAPB-DMTP-COF, a COF-based ethephon residue fluorescent rapid detection method is constructed, thereby realizing fluorescent rapid detection of ethephon residues and effectively improving the detection efficiency.

[0023] The invention provides a method for rapid detection of ethephon, using a covalent organic framework (COF) material as a fluorescent probe, and constructing a COF-based ethephon fluorescence rapid detection method by fitting a curve of the fluorescence intensity measured after incubation of different concentrations of ethephon with the COF material and the corresponding ethephon concentration, so as to achieve rapid and sensitive detection of ethephon residues and greatly improve the detection efficiency. At the same time, the method is simple and fast, and can overcome the shortcomings of the existing ethephon detection method, such as biological enzymes, poor stability, and low sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the scanning electron microscope image of the TAPB-DMTP-COF involved;

[0025] Figure 2 From top to bottom are infrared spectra of 1,3,5-tris(4-aminophenyl)benzene, 2,5-dimethoxyterephthalaldehyde and TAPB-DMTP-COF provided by the present invention;

[0026] Figure 3 This is the fluorescence response spectrum of the present invention to ethephon, with an excitation wavelength of 400nm;

[0027] Figure 4 The fitting curves for different concentrations of ethephon from 0 to 400 mg / L provided by the present invention have an excitation wavelength of 400 nm and an emission wavelength of 520 nm. DETAILED DESCRIPTION

[0028] The principle of the invention is that ethephon is decomposed into phosphoric acid, hydrochloric acid and ethylene in a solution with a pH value greater than 3.5, and the solution enables the fluorescent probe to produce a protonated fluorescence enhancement effect.

[0029] The present invention provides a method for preparing a fluorescent sensor based on a covalent organic framework, comprising:

[0030] Dissolve 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxyterephthalaldehyde in acetonitrile solution respectively;

[0031] The two solutions were mixed and glacial acetic acid was added dropwise, stirred, and reacted at room temperature to prepare a covalent organic framework TAPB-DMTP-COF.

[0032] In a preferred embodiment, 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxyterephthalaldehyde are added to an acetonitrile solution and dissolved, and the specific steps of preparing the mixed solution include:

[0033] 1,3,5-tris(4-aminophenyl)benzene, 2,5-dimethoxyterephthalaldehyde and acetonitrile solution are mixed and dispersed; magnetic stirring can be used; further, the magnetic stirring step is magnetic stirring at 0-30°C for 0.5-1h.

[0034] In a preferred embodiment, the 1,3,5-tris(4-aminophenyl)benzene, 2,5-dimethoxyterephthalaldehyde, acetonitrile and glacial acetic acid are preferably added in a ratio of 10 mg: 8 mg: 20 ml: 0.5 ml. When other ratios are used, the yield and purity will be affected, so it is preferred that 1,3,5-tris(4-aminophenyl)benzene, 2,5-dimethoxyterephthalaldehyde, acetonitrile and glacial acetic acid are added in a ratio of 10 mg: 8 mg: 20 ml: 0.5 ml.

[0035] In an optional embodiment, after adding the glacial acetic acid solution, the reaction time at room temperature is 7 hours.

[0036] In a preferred embodiment, after the reaction, the solid matter is obtained by centrifugation, washed with anhydrous ethanol for multiple times, and vacuum dried to obtain the fluorescent COF material (TAPB-DMTP-COF). Furthermore, the vacuum drying is carried out in a vacuum drying oven at 80° C. for 7 h.

[0037] The present invention also provides a method for fluorescent detection of pesticide residues. According to the fluorescent COF material prepared above, the fluorescent signal of ethephon is enhanced as the concentration of ethephon increases. Based on this, a COF-based rapid fluorescence detection method for ethephon residues can be constructed according to the sensitivity curve of the concentration of ethephon residues and the fluorescence signal of TAPB-DMTP-COF, thereby realizing rapid fluorescence detection of ethephon residues and effectively improving the detection efficiency.

[0038] The following examples are used to further illustrate the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and substance of the present invention, modifications or substitutions made to the present invention all belong to the scope of the present invention.

[0039] Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, all reagents used in the present method are of analytical grade or above.

[0040] Example 1

[0041] This embodiment provides a fluorescent covalent organic framework (COF) material, which can be prepared by the following method:

[0042] S1: adding 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxyterephthalaldehyde into acetonitrile and dissolving them respectively;

[0043] Specifically, step S1 includes:

[0044] S11: Weigh a certain amount of 1,3,5-tris(4-aminophenyl)benzene and a certain amount of 2,5-dimethoxyterephthalaldehyde and pour them into beakers of appropriate sizes respectively;

[0045] S12: Add a certain amount of acetonitrile solution into two beakers respectively and stir at 25°C for 0.5h.

[0046] It should be noted that the ratio of 1,3,5-tris(4-aminophenyl)benzene to the acetonitrile solution in this step is 10 mg:10 mL, and the ratio of 2,5-dimethoxyterephthalaldehyde to the acetonitrile solution is 8 mg:10 mL. In other embodiments, the amount of each component can be determined according to one's own needs.

[0047] S2: Pour the two solutions into a beaker, stir and mix, and add a certain amount of glacial acetic acid to prepare TAPB-DMTP-COF;

[0048] Specifically, step S2 includes:

[0049] S21: Pour the acetonitrile solution of 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxyterephthalaldehyde into a beaker of appropriate size and stir at room temperature for 0.5 h;

[0050] S22: Add a certain amount of glacial acetic acid to the mixed solution, seal with plastic wrap, and stir at room temperature for 7 hours;

[0051] After centrifugation, the product was washed with ethanol three times and dried in a vacuum oven at 80°C for 12 h to collect the yellow powder product TAPB-DMTP-COF.

[0052] It should be noted that the ratio of 1,3,5-tris(4-aminophenyl)benzene, 2,5-dimethoxyterephthalaldehyde, acetonitrile and glacial acetic acid in this step is 10 mg:8 mg:20 mL:0.5 mL.

[0053] The yellow powder product TAPB-DMTP-COF obtained above was subjected to electron microscope scanning. The results are as follows Figure 1 As shown in the figure, it can be seen that TAPB-DMTP-COF is a regular sphere with an average particle size of about 200nm. The raw materials 1,3,5-tris(4-aminophenyl)benzene (TAPB), 2,5-dimethoxyterephthalaldehyde (DMTP) and the yellow powder product TAPB-DMTP-COF obtained above were examined by infrared spectrometer, and the infrared spectrum was obtained as shown in Figure 2 As shown in the figure, it can be seen that 2,5-dimethoxyterephthalaldehyde has a peak at 1682 cm -1 A characteristic peak appeared at 3353 cm, which is due to the C=O stretching vibration of the benzene ring. In the infrared spectrum of 1,3,5-tri(4-aminophenyl)benzene, a peak at 3353 cm -1 NH stretching vibration, however, the characteristic peaks of these two monomers are lost in COF.-1 The characteristic peak of imine bond caused by CN was formed at 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxyterephthalaldehyde. This indicates that the amino groups of 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxyterephthalaldehyde were condensed through Schiff base reaction, confirming the successful synthesis of TAPB-DMTP-COF. The yellow powder product obtained was dissolved in water and had green fluorescence under ultraviolet light.

[0054] Example 2

[0055] The COF material prepared in Example 1 was dissolved in water to obtain an aqueous solution of 0.06 mg / mL COF fluorescent material. 1 mL of the aqueous solution was incubated with 1 mL of a solution containing different concentrations of ethephon (e.g., the concentration of ethephon was 25 mg / L, 50 mg / L, 100 mg / L, and 500 mg / L) for 30 min, and the emission spectrum was read using a fluorescence spectrophotometer. The results are shown in FIG. Figure 3 From the figure, we can see that the fluorescent COF material has an obvious characteristic peak at the emission wavelength of 520nm, and the fluorescence intensity changes differently according to the different concentrations of ethephon, indicating that the material can perform specific fluorescence recognition of ethephon.

[0056] A fluorescence detection method for ethephon residues was established based on specific fluorescence recognition, and rapid detection was performed based on the fluorescent COF material prepared in Example 1, which specifically includes the following steps:

[0057] S1: co-incubating the aqueous solution of the fluorescent COF material prepared by the method for preparing the fluorescent COF material in Example 1 with a fruit and vegetable extract containing ethephon residue (immersing 1 g of chopped fruit pulp in 3 ml of water as the extract, and centrifuging to obtain the supernatant):

[0058] S2: After oscillation and mixing, the fluorescence intensity of the test solution was measured by a fluorescence spectrophotometer at an excitation wavelength of 400 nm and an emission wavelength of 520 nm, with a slit width of 5 nm;

[0059] S3: Use the absolute value of fluorescence intensity to perform nonlinear fitting on different concentrations of ethephon and construct a new rapid detection method for ethephon.

[0060] It should be noted that in the above implementation method, the concentration of the fluorescent COF material aqueous solution is 0.06 mg / ml, the dosage of the fluorescent COF material aqueous solution and the dosage of the fruit and vegetable extract are 1 ml:1 ml respectively, and the reaction time is 30 min.

[0061] Of course, in other embodiments, the amount of each component can be determined by proportionally increasing or decreasing the above ratio according to one's own needs.

[0062] The invention provides a method for fluorescent detection of pesticide residues. The fluorescent signal generated by the specific fluorescent recognition of ethephon by TAPB-DMTP-COF can be enhanced, and based on the sensitivity curve of the concentration of the ethephon residue and the fluorescent signal of TAPB-DMTP-COF, a method for rapid fluorescent detection of ethephon residue based on TAPB-DMTP-COF is constructed, thereby realizing rapid fluorescent detection of ethephon residue and effectively improving the detection efficiency.

[0063] Example 3

[0064] This embodiment provides a fluorescence detection method for ethephon residues, which specifically comprises the following steps:

[0065] S1: Weigh 10 mg of 1,3,5-tris(4-aminophenyl)benzene and 8 mg of 2,5-dimethoxyterephthalaldehyde and add them into 20 ml beakers respectively. Then add 10 ml of acetonitrile solution into two beakers respectively and stir at room temperature for 30 min to fully dissolve.

[0066] S2: Pour the acetonitrile solution of 1,3,5-tri(4-aminophenyl)benzene and 2,5-dimethoxyterephthalaldehyde into a 50 ml beaker, add 0.5 ml of glacial acetic acid dropwise, seal with plastic wrap, and stir at room temperature for 7 hours.

[0067] S3: After centrifugation at 6000 rpm for 10 min, the mixture was washed with ethanol three times and dried in a vacuum oven at 80°C for 12 h to collect the yellow fluorescent COF material.

[0068] S4: Dissolve the fluorescent COF material in water to prepare a 0.06 mg / ml fluorescent probe aqueous solution, add 1 ml of the COF solution to a fruit and vegetable extract standard containing ethephon residues (i.e., add the standard ethephon to a blank fruit and vegetable extract, wherein the blank fruit and vegetable extract is prepared by soaking 1 g of chopped pulp in 3 ml of water and centrifuging to obtain the supernatant), and incubate for 30 minutes. The concentrations of the standard ethephon are: 0.2, 0.4, 0.8, 1, 2, 4, 8, 10, 20, 40, 80, 100 mg / L.

[0069] At the same time, 1 ml of COF solution was added to the test solution of fruit and vegetable extract containing ethephon residues and incubated for 30 min.

[0070] S5: Measure the fluorescence intensity of the standard and the test solution under the conditions of 400nm excitation, 520nm emission, and 5nm slit width.

[0071] S6: Perform curve fitting based on the absolute value of the fluorescence intensity of the standard and the concentration of ethephon.

[0072] The curve fitting result of the standard product in this embodiment is the fitting curve of different concentrations of ethephon and fluorescence intensity. Figure 4 , the fitting equation is Y = (1346.68 + 162.83X) / (1 + 0.07X + 3.21 × 10 -5 X 2 ), where X represents the concentration of ethephon in the solution, in mg / L, and Y is the fluorescence intensity. The detection limit of the method is determined to be 0.1 mg / L based on a 3-fold signal-to-noise ratio, and the concentration of the solution to be tested can be obtained by substituting the fluorescence value of the solution to be tested into the fitting equation. Thus, the residual concentration of ethephon can be determined based on different fluorescence intensities, and the residual concentration of ethephon can be quickly detected.

[0073] Example 4

[0074] Three kinds of fruit and vegetable samples, strawberry, ginseng fruit and persimmon, were tested. The detection rate of ethephon was tested by adding the standard substance ethephon. The results are shown in Table 1. The results show that the recovery rate of the test is between 94.6% and 106.1%, indicating that the results of this method are accurate and reliable.

[0075] Table 1 Recovery rates of spiked ethephon in three fruit and vegetable samples

[0076]

[0077] Example 5 Interference Test

[0078] Different types of competitive pesticides are used to prepare a concentration of 0.8 μg / mL, and different types of competitive pesticides are mixed with standard solutions of ethephon to prepare multiple different types of standard mixed solutions of ethephon; and the detection is performed according to the detection method of the above-mentioned Example 4, wherein the competitive pesticides include: thiazopyralid, sodium naphthalene-1-acetate, choline chloride and mepiquat chloride. The test results show that there is no difference between the test results of the standard mixed solutions of different types of ethephon and those without adding competitive pesticides, indicating that the competitive pesticides thiazopyralid, sodium naphthalene-1-acetate, choline chloride and mepiquat chloride do not interfere with the detection of ethephon.

[0079] In summary, the preparation method of the fluorescent COF material and the detection method of pesticide residues provided by the embodiments of the present invention use the COF material as a fluorescent probe, which has the advantages of high aperture ratio and high specific surface area. Through the fitting curve of different concentrations of ethephon and fluorescence intensity, a COF-based ethephon fluorescence rapid detection method is constructed to achieve rapid and sensitive detection of ethephon residues, thereby greatly improving the detection efficiency. At the same time, the method is simple and fast, and can overcome the shortcomings of biological enzymes, poor stability, and low sensitivity that the existing detection of ethephon relies on.

[0080] The above description is only an embodiment of the present invention and does not limit the present invention. For professionals in this field, the present invention has various improvements and developments. Any modifications made within the spirit and principles of the present invention should be included in the protection of the present invention.

Claims

1. A method for preparing a fluorescent COF material, characterized in that: The method comprises the following steps: condensing 1,3,5-tri(4-aminophenyl)benzene with a solution of 2,5-dimethoxyterephthalaldehyde under the action of glacial acetic acid to obtain TAPB-DMTP-COF.

2. The preparation method according to claim 1, characterized in that The solvent of the solution is acetonitrile, the addition ratio of 1,3,5-tris(4-aminophenyl)benzene to 2,5-dimethoxyterephthalaldehyde is 5:4 by mass, the amount of 1,3,5-tris(4-aminophenyl)benzene to acetonitrile is 1:1-2 in mg:ml, the amount of 2,5-dimethoxyterephthalaldehyde to acetonitrile is 3:5-6 in mg:ml; the amount of glacial acetic acid is 35-50:1 in volume ratio of acetonitrile to glacial acetic acid.

3. The preparation method according to claim 1, characterized in that: The condensation reaction after adding glacial acetic acid is stirred at room temperature for 6 to 8 hours; after the reaction, centrifugation is performed first, and then washed three times with ethanol, and dried in a vacuum drying oven at 60 to 80° C. for 8 to 12 hours, and then the yellow powder product TAPB-DMTP-COF is collected.

4. Use of the TAPB-DMTP-COF obtained by the preparation method according to any one of claims 1 to 3 in preparing a kit for detecting ethephon.

5. A detection kit for detecting ethephon, comprising TAPB-DMTP-COF obtained by the preparation method according to any one of claims 1 to 3.

6. Use of TAPB-DMTP-COF obtained by the preparation method according to any one of claims 1 to 3 in detecting ethephon.

7. A method for rapid detection of ethephon in fruits and vegetables, characterized in that: It includes the following steps: S1, dissolving TAPB-DMTP-COF powder in water to obtain an aqueous solution of TAPB-DMTP-COF; S2, diluting the ethephon standard solution with water to prepare a series of solutions to be tested with a concentration gradient; S3, after incubating the aqueous solution of TAPB-DMTP-COF with the standard solution, the fluorescence signal is read using a fluorescence spectrophotometer to establish a linear relationship between the ethephon concentration and the fluorescence signal; S4, preparing a test solution from the fruit and vegetable sample, mixing the test solution with the aqueous solution of TAPB-DMTP-COF for incubation reaction, and reading the fluorescence signal with a fluorescence spectrophotometer; Substituting the obtained fluorescence signal of the sample to be tested into the linear relationship can obtain the concentration of ethephon in the sample to be tested.

8. The method for detecting ethephon in fruits and vegetables as claimed in claim 7, characterized in that: In step S1, the concentration of the aqueous solution of TAPB-DMTP-COF is 0.6 mg / L; in step S3, the aqueous solution of TAPB-DMTP-COF and the standard solution are added at a volume ratio of 1:

1.

9. The method for detecting ethephon in fruits and vegetables as claimed in claim 7, characterized in that: In step S2, the standard solution is a solution of ethephon standard diluted at a 2-fold or 4-fold ratio.

10. The method for detecting ethephon in fruits and vegetables as claimed in claim 7, characterized in that: In step S3, the incubation reaction time is 20 to 40 minutes; the fluorescence signal is read at the fluorescence intensity at an excitation wavelength of 400 nm, an emission wavelength of 520 nm, and a slit width of 5 nm.

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