Fluorescent ion probe based on dihydroxynaphthalene, preparation of fluorescent ion probe and application of fluorescent ion probe in diquat detection

Abstract

The invention discloses a dihydroxynaphthalene-based fluorescent ion probe and preparation and application thereof in diquat detection, the fluorescent ion probe can realize rapid, sensitive and specific detection of diquat residues, meanwhile, the fluorescent ion probe is loaded on paper to develop a fluorescent paper base, the requirement of a portable device is met, and the dihydroxynaphthalene-based fluorescent ion probe can be applied to detection of diquat. And a new method is provided for convenient detection of diquat in a complex matrix.

Description

(I) Technical field

[0001] The invention relates to a fluorescent ion probe based on dihydroxynaphthalene and the preparation method and application of the fluorescent ion probe in detecting diquat. (II) Background technology

[0002] Diquat (DQ), also known as 1,1'-ethylene-2,2'-bipyridyl dibromide, is a classic commercial quaternary ammonium herbicide widely used for crop weed control and drying purposes. Some evaluations have shown that diquat is a strong electron transfer and produces oxidative stress, so it promotes the formation of superanion radicals and causes cell apoptosis in the biological microenvironment, and its strong irritation and residues cause serious health hazards to organisms, such as irritation to the eyes, skin, mouth, stomach, throat, etc. Therefore, as food safety issues related to pesticide residues become increasingly important, China has set maximum residue limits for diquat in various foods, such as 2 mg / kg for wheat and 0.05 mg / kg for corn and potatoes, and explored several classic analytical techniques for detection, such as high performance liquid chromatography (HPLC), electrochemical analysis, surface enhanced Raman spectroscopy, etc. However, these traditional detection methods and large instruments often have the problems of cumbersome processing, difficult operation, and low sensitivity. Therefore, it is urgent to propose a simple, rapid and sensitive detection method.

[0003] Fluorescent probe detection technology has become one of the important means besides some traditional technologies due to its good sensitivity, selectivity and real-time monitoring, and the selection of fluorescent materials is an important factor in determining the sensitivity of fluorescent probes. The new material ionic liquids (ILs) have become more attractive in the field of analysis due to their high adjustability and unique optical properties. The charge characteristics of ionic liquids also give them a signal amplification effect. According to the structural characteristics of the analyte, the anions or cations are precisely adjusted in a targeted manner, and the fluorescence, color, weak interaction force, etc. of the probe are optimized, which makes ionic liquids a unique sensor. Therefore, as long as the adjustability of ionic liquids is fully utilized, it is expected to develop a fluorescent ion probe for rapid and sensitive detection of diquat. (III) Summary of the invention

[0004] The purpose of the present invention is to provide a fluorescent ion probe based on dihydroxynaphthalene and its preparation and application in the detection of diquat. The fluorescent ion probe can realize rapid, sensitive and specific detection of diquat residues. At the same time, the fluorescent ion probe is loaded on paper to develop a fluorescent paper base, which meets the needs of portable devices and provides a new method for the convenient detection of diquat in complex matrices.

[0005] The technical solution adopted by the present invention is:

[0006] The present invention provides a fluorescent ion probe based on dihydroxynaphthalene, wherein the structure of the fluorescent ion probe is shown in one of the following:

[0007]

[0008] The invention provides a preparation method of the fluorescent ion probe, which comprises: placing trihexyl (tetradecyl) phosphine hydroxide and dihydroxynaphthalene in a single-necked flask, dissolving them with anhydrous ethanol, fully stirring and reacting at a temperature of 40 to 120° C. for 5 to 18 hours (preferably at 60° C. for 12 hours), evaporating under reduced pressure to remove the solvent after the reaction is completed, and continuing to dry under nitrogen at 60 to 100° C. (preferably 80° C.) to obtain a viscous product, which is the fluorescent ion probe; the dihydroxynaphthalene comprises 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,6-dihydroxynaphthalene and 2,7-dihydroxynaphthalene.

[0009] Furthermore, the molar ratio of trihexyl (tetradecyl) phosphine hydroxide to dihydroxynaphthalene is 2:1.

[0010] Furthermore, the preparation of trihexyl (tetradecyl) phosphine hydroxide is as follows: trihexyl (tetradecyl) phosphine chloride is added to a chromatography column filled with a strong alkaline anion exchange resin, and is slowly rinsed with anhydrous ethanol at a speed of 6 to 8 seconds per drop until the effluent changes from alkaline to neutral, and the collected alkaline effluent is the trihexyl (tetradecyl) phosphine hydroxide solution, and the process is a dechlorination treatment; the strong alkaline anion exchange resin is AMberlite IRA-400 (Cl); and the mass ratio of trihexyl (tetradecyl) phosphine chloride to the strong alkaline anion exchange resin is 1:6.

[0011] The present invention also provides an application of the fluorescent ion probe in detecting diquat in actual samples.

[0012] Further, the application is as follows: the sample to be tested is ground and crushed, ultrasonicated and soaked in methanol at 100-350W for 5-30min, centrifuged, the fluorescent ion probe is added to the supernatant, the fluorescence spectrum at 350-550nm is detected, and the diquat content in the sample to be tested is calculated based on the standard curve of diquat concentration and fluorescence quenching intensity.

[0013] Furthermore, the fluorescent ion probe is added to the supernatant at a concentration of 5 to 500 μM.

[0014] Furthermore, the standard curve of diquat concentration and fluorescence quenching intensity was prepared according to the following steps: a fluorescent ion probe methanol solution was added to a centrifuge tube, and then different volumes of diquat methanol solution were added to make the probe concentration 50 μM, and the final concentration of diquat was 0, 0.5, 1, 2, 2.5, 3, 4, 5, 6, 7, 7.5, 8, 9, 10, 25, 50, 75, 100, 250, 500, 1000 μM, and the mixture was evenly mixed and poured into a quartz dish, and the fluorescence spectrum at 350 to 550 nm was measured to prepare a standard curve with the fluorescence quenching intensity (ΔF=F0-F) of the fluorescent ion probe at 410 nm as the ordinate and the diquat concentration as the abscissa.

[0015] The present invention also provides a diquat test strip made of fluorescent ion probe, wherein the test strip is made by mixing filter paper in a fluorescent ion probe methanol solution (preferably 5.0×10 -4 M) and then dried naturally; the method of using the test strip is: immerse the front end of the test strip into the solution to be tested, take it out after 10s, observe the fluorescence change of the test strip under a 365nm ultraviolet lamp, and compare the test strip fluorescence quenching standard colorimetric card to determine the concentration range of diquat in the solution to be tested;

[0016] The test strip fluorescence quenching standard colorimetric card is prepared according to the following steps: the front end of the test strip is immersed in a methanol solution containing different concentrations of diquat (0, 1, 5, 10, 50, 100, 500, 1000 μM), taken out after 10 seconds, and the change of the fluorescence of the test strip is recorded under a 365nm ultraviolet lamp to prepare a fluorescence quenching standard colorimetric card, and the color gradually changes from strong blue fluorescence to no fluorescence.

[0017] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0018] (1) The fluorescent ion probe of the present invention has high sensitivity.

[0019] The present invention successfully synthesizes a series of fluorescent ion probes based on dihydroxynaphthalene through proton exchange reaction between dihydroxynaphthalene with different substitution sites and trihexyl (tetradecyl) phosphine hydroxide; due to the strong electrostatic attraction and π-π stacking effect between diquat and the fluorescent ion probe, diquat can quickly quench the fluorescence of the fluorescent ion probe and be captured by the detector, especially the fluorescence of 18-DHNP can be quickly quenched (less than 5s). The linear range of 18-DHNP fluorescence detection of diquat is determined to be 0.05-100μM by fluorescence titration method, and its LOD can reach 0.1μM.

[0020] (2) The fluorescent ion probe of the present invention exhibits high selectivity and anti-interference properties.

[0021] The fluorescent ion probe of the present invention can specifically identify diquat from 20 different common pesticides and 5 quaternary ammonium salt pesticides, and has good selectivity and anti-interference.

[0022] (3) Fluorescent ion probe-based preparations can detect diquat quickly, portablely, and sensitively.

[0023] The fluorescent ion probe is loaded onto paper and assembled into a fluorescent paper base, which is portable and can detect diquat quickly and in real time.

[0024] (4) The present invention provides a method for rapid, sensitive and quantitative detection of diquat, which has good applicability in a variety of real food samples; it meets the demand for portable devices and provides a new idea for on-site semi-quantitative detection of diquat. (IV) Description of the drawings

[0025] Figure 1 This is the fluorescence titration emission spectrum of 18-DHNP detecting different concentrations of diquat.

[0026] Figure 2 The graph (a) shows the fluorescence quenching intensity (ΔF) at 410 nm and the diquat concentration (0-1000 μM) when 18-DHNP detects different concentrations of diquat, and the calibration curve (b) shows the linear range of the fluorescence quenching intensity and the diquat concentration (0-100 μM).

[0027] Figure 3 The fluorescence spectra of 18-DHNP detecting diquat at different response times (a) and the line graph with fluorescence intensity as the ordinate and response time as the abscissa (b).

[0028] Figure 4 The selectivity and anti-interference of 18-DHNP in detecting different pesticides; a represents the structural formula and number of 20 pesticides: 1 diquat, 2 benzylsulfuron-methyl, 3 carbendazim, 4 high-efficiency cypermethrin, 5 dimethoate, 6 high-efficiency cypermethrin, 7 pentachloronitrobenzene, 8 triazophos, 9 deltamethrin, 10 methyl parathion, 11 chlorpyrifos, 12 fomesafen, 13 phoxim, 14 pretilachlor, 15 acephate, 16 diazinon, 17 butachlor, 18 acetochlor, 19 profenofos and 20 dichlorvos; b represents the bar graph of fluorescence quenching intensity and pesticide types of 18-DHNP in detecting different pesticides.

[0029] Figure 5 The selectivity and anti-interference of 18-DHNP in detecting different quaternary ammonium pesticides; a represents the structural formula of quaternary ammonium pesticides: diquat DQ, paraquat PQ, diquat FQ, mepiquat MQ, chlormequat-chloride CQ; b represents the bar graph of the fluorescence quenching intensity of 18-DHNP in detecting different quaternary ammonium pesticides and the types of quaternary ammonium pesticides.

[0030] Figure 6 The Job plot's curve of the fluorescence quenching intensity of 18-DHNP detecting different contents of diquat and the molar concentration ratio of diquat to the total amount of substances.

[0031] Figure 7 The fluorescence visualization photographs were taken under 365 nm light when no (blank) and diquat were added to the 18-DHNP solution.

[0032] Figure 8 The preparation and use process of 18-DHNP fluorescent paper (a) and the fluorescent photos taken under 365nm light after detecting different concentrations of diquat (0-1000μM) (b). (V) Specific implementation methods

[0033] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0034] The chemical reagents and solvents used in the examples were all commercially available analytical grade.

[0035] The fluorescence spectrum measurement conditions were set as an excitation wavelength of 345 nm, an emission wavelength of 350-600 nm, and excitation and emission slit widths of 2.5 nm and 2.5 nm, respectively.

[0036] Example 1. Synthesis of fluorescent ion probe

[0037] (1) Dechlorination of trihexyl (tetradecyl) phosphine chloride:

[0038] Trihexyl (tetradecyl) phosphine chloride was added to a chromatography column containing a strongly basic anion exchange resin (model AMberlite IRA-400 (Cl)) in a mass ratio of 1:6, and was slowly rinsed with anhydrous ethanol at a rate of 8 seconds / drop until the effluent was neutral. The collected alkaline effluent was the trihexyl (tetradecyl) phosphine hydroxide solution obtained after dechlorination treatment, and its concentration was determined to be 0.3027 M by acid-base titration.

[0039] (2) Synthesis of fluorescent ion probe 18-DHNP:

[0040] 0.1602 g of 1,8-dihydroxynaphthalene and a solution containing 1.0010 g of trihexyl (tetradecyl) phosphine hydroxide obtained in step (1) (solution volume 6.61 mL), with a molar ratio of trihexyl (tetradecyl) phosphine hydroxide to 1,8-dihydroxynaphthalene of 2:1, were added to a round-bottom flask and dissolved in anhydrous ethanol, and then fully stirred in a 60°C oil bath and reacted for 12 hours. After the reaction was completed, the reaction solution was evaporated under reduced pressure to remove the solvent, and then heated in a nitrogen atmosphere at 80°C for further drying, and finally 1.0265 g of a viscous liquid product was obtained, which was a fluorescent ion probe, recorded as 18-DHNP. It can be sealed and stored at room temperature.

[0041] The 1,8-dihydroxynaphthalene was replaced by 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,6-dihydroxynaphthalene and 2,7-dihydroxynaphthalene, respectively, and the other operations were the same to prepare the fluorescent ion probes 13-DHNP, 14-DHNP, 15-DHNP, 16-DHNP, 17-DHNP, 23-DHNP, 26-DHNP and 27-DHNP, respectively.

[0042] Example 2: Selectivity and anti-interference of fluorescent ion probe for detection of diquat

[0043] Accurately weigh the solid diquat and dissolve it in methanol to prepare 1.0×10 -2 M diquat standard stock solution. Accurately weigh 18-DHNP and dissolve it in methanol to prepare 1.0×10 -3 M 18-DHNP standard stock solution.

[0044] (1) Fluorescence detection of diquat by 18-DHNP:

[0045] When performing fluorescence titration, first add 50 μL of 1.0×10 -3 M 18-DHNP standard stock solution was added to a centrifuge tube, and then different volumes of diquat standard stock solution were added, and then the volume was adjusted to 1.0 mL with methanol, so that the final concentration of the probe was 50 μM, and the final concentration of diquat was 0, 0.5, 1, 2, 2.5, 3, 4, 5, 6, 7, 7.5, 8, 9, 10, 25, 50, 75, 100, 250, 500, 1000 μM. After mixing evenly, the mixture was poured into a quartz dish, and the fluorescence spectra of samples containing different concentrations of diquat (0-1000 μM) were measured at 350-550 nm. The results are as follows: Figure 1 As shown, as the concentration of diquat increased from 0 to 1000 μM, the fluorescence of the probe was gradually quenched, and the fluorescence intensity at 410 nm gradually decreased.

[0046] according to Figure 1The graph with the fluorescence quenching intensity of 18-DHNP at 410 nm (ΔF = F0-F) as the ordinate and the concentration of diquat (0-1000 μM) as the abscissa is shown in FIG. Figure 2 As shown in a, Figure 2 Figure b is a calibration curve of the linear range of fluorescence quenching intensity and diquat concentration (0-100 μM), and there is a good linear relationship between the quenching intensity and the diquat concentration.

[0047] like Figure 2 As shown, in the linear range of 0.05-10 μM, the linear standard calibration curve equation is fitted as ΔF=51.9C+13.0(R 2 =0.9934); In the linear range of 10-100 μM, the linear standard calibration curve equation was fitted as ΔF=2.8C+486.3(R 2 =0.9939). The limit of detection (LOD) of 18-DHNP for diquat was calculated to be 0.1 μM.

[0048] (2) Response time of 18-DHNP to diquat:

[0049] Add 18-DHNP standard stock solution to a centrifuge tube, then add diquat standard stock solution, and then dilute to 1.0 mL with methanol, so that the probe concentration is 50 μM and the final concentration of diquat is 5 μM. Mix well and pour into a quartz dish, and measure the fluorescence spectrum of 350-550 nm at 0 (no diquat), 5, 15, 30, 45, 60, 75, 90, 105, and 120 s, respectively. The results are as follows: Figure 3 As shown in a, the line graph with the fluorescence intensity of 18-DHNP at 410 nm as the ordinate and the response time as the abscissa is shown in Figure 3 As shown in b.

[0050] like Figure 3 As shown, after the addition of 5 μM diquat, the fluorescence intensity of 50 μM 18-DHNP decreased significantly immediately, and the response to diquat was completed within 5 s and remained stable within 120 s, indicating that the probe has the characteristics of rapid response.

[0051] (3) Selectivity of 18-DHNP for detection of diquat:

[0052] 20 pesticides (including diquat and 19 interfering pesticides): 1 diquat (DQ), 2 benzylsulfuron-methyl, 3 carbendazim, 4 high-efficiency cypermethrin, 5 dimethoate, 6 high-efficiency cypermethrin, 7 pentachloronitrobenzene, 8 triazophos, 9 deltamethrin, 10 methyl parathion, 11 chlorpyrifos, 12 fomesafen, 13 phoxim, 14 pretilachlor, 15 acephate, 16 diazinon, 17 butachlor, 18 acetochlor, 19 profenofos and 20 dichlorvos, structural formula see Figure 4 As shown in a.

[0053] In order to explore the selectivity of the probe for diquat detection, the 18-DHNP standard stock solution was added to a centrifuge tube, and then methanol solutions of 20 pesticides were added respectively, and then the volume was fixed to 1.0 mL with methanol, so that the probe concentration was 50 μM and the final concentration of the pesticides was 5 μM. After mixing evenly, the mixture was poured into a quartz dish, and the fluorescence spectrum of 350-550 nm was detected. A bar graph was drawn with the fluorescence quenching intensity (ΔF) as the ordinate and the type of pesticide as the abscissa ( Figure 4 The selectivity of the probe was shown in (b), demonstrating that the probe has excellent selectivity.

[0054] (4) Anti-interference of 18-DHNP on diquat detection

[0055] In order to explore the interference of interfering pesticides on the detection of paraquat by the probe, the 18-DHNP standard stock solution was added to a centrifuge tube, and then the 20 pesticides in step (3) (diquat and equivalent interfering pesticides) were added at the same time, and then the volume was adjusted to 1.0 mL with methanol, so that the probe concentration was 50 μM and the final concentration of the pesticides was 5 μM. The fluorescence spectrum was recorded and the bar graph was drawn in the same way as step (3). Figure 4 As shown in the anti-interference in b, it is proved that the probe also has good anti-interference performance.

[0056] (5) Selectivity and anti-interference of the probe for the detection of the same type of quaternary ammonium pesticides

[0057] Selectivity: Using the same detection method and conditions as step (3), the detection probe is sensitive to the same type of quaternary ammonium pesticides ( Figure 5 The detection selectivity of a) is shown in Figure 5 The selectivity is shown in b.

[0058] Anti-interference: Using the same detection method and conditions as step (4), the detection probe is effective for the same type of quaternary ammonium pesticides ( Figure 5 The anti-interference performance of a) is shown in Figure 5 As shown in b, the anti-interference.

[0059] Figure 5 In Figure b, it can be found that even pesticides with highly similar structures will not interfere with the specific recognition of diquat by 18-DHNP, thanks to the "size match" between the two.

[0060] (6) The mixing ratio of 18-DHNP to diquat:

[0061] The matching ratio of the probe and diquat was determined according to the Job plot's method, and the total molar concentration of the probe and diquat was determined to be 240 μM. The fluorescence spectra at 350-550 nm were measured when the concentration ratio of the probe and diquat was 0:10, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1, and 10:0, respectively.

[0062] Taking 1:9 as an example, 100 μL of 18-DHNP standard stock solution and 100 μL of diquat standard stock solution were added to centrifuge tubes respectively, and then the volume was fixed to 1.0 mL with methanol, so that the probe concentration was 24 μM and the diquat concentration was 216 μM. After mixing evenly, the mixture was poured into a quartz dish for determination. The other concentration ratios were the same as above. The Job plot's curve ( Figure 6 ). When the quenching intensity reaches the maximum, the proportion of diquat is about 0.5, indicating that the mixing ratio of 18-DHNP to diquat is about 1:1.

[0063] Example 3: Sensitivity and accuracy of spike recovery detection of 18-DHNP for diquat in real samples

[0064] Cereals (rice, wheat, sorghum, corn and soybean) and tea (Longjing tea, Maojian and Biluochun) were collected as real samples, and the recovery rate was determined by spike recovery experiment. 1.0g of each cereal crop was crushed or ground, and 10mL of methanol was added as the extractant. After 250W ultrasonication for 10min, insoluble impurities were removed by centrifugation to obtain each extract. 0.1g of tea leaves were taken with 10mL of methanol, ultrasonicated at 250W and soaked for 5min, and then the tea residue was removed to obtain the tea extract.

[0065] Diquat was added to 100 μL of the extract of each sample, and then 18-DHNP standard stock solution (same as in Example 2) was added to make the added concentration 50 μM, wherein the final concentration of diquat added was 5, 10 and 80 μM, and the fluorescence spectra at 350-550 nm were measured respectively. Figure 2 The standard curve obtained in the above method was used to calculate the recovery rate of diquat, and the recovery concentration was verified by HPLC analysis. The results are shown in Table 1. It can be seen that the recovery rate of the probe for diquat spiked in real samples is between 96.1% and 103.4%, and the relative standard deviation (RSD) is less than 3.5%. In addition, P>0.05 also verified that there was no significant difference in the results of the two methods.

[0066] The HPLC analysis conditions were based on HG_T 5246-2017. The instrument model of this experiment was Chromai Leaps, using a C18 chromatographic column. The specific operating conditions were as follows: the mobile phase was 3.64 g of sodium heptane sulfonate, dissolved in 900 mL of distilled water, 16 mL of phosphoric acid was added, the pH value was adjusted to 2 with triethylamine, and 100 mL of acetonitrile was added, mixed evenly and filtered; the flow rate was 1.0 mL / min, the column chamber temperature was low, the detection wavelength was 310 nm, and the injection volume was 10 μL.

[0067] Table 1 Results of spike recovery experiments in food samples

[0068]

[0069] ND a :Notdetected.

[0070] Example 4, 18-DHNP portable paper base

[0071] 1. Study on the quenching of probe by diquat

[0072] A 50 μM 18-DHNP methanol solution emitted bright blue fluorescence under a 365 nm lamp. When 5 μM diquat was added, the fluorescence of the solution was quickly quenched. Figure 7 , which provides a basis for the production of fluorescent paper base.

[0073] 2. Production of portable paper base

[0074] A round filter paper (9 cm in diameter) was soaked in 2 mL of 5.0 × 10 -4 M of 18-DHNP methanol solution, after natural air drying, the 18-DHNP-based paper substrate ( Figure 8 In a), the paper base can be cut into various desired shapes.

[0075] 3. Portable paper-based fluorescence quenching standard colorimetric card

[0076] The front end of the test strip was immersed in methanol solutions containing different concentrations of diquat (0, 1, 5, 10, 50, 100, 500, 1000 μM), and taken out after 10 seconds. The changes in the fluorescence of the test strip were recorded under a 365 nm ultraviolet lamp. Figure 8 As shown in middle b, the color gradually changes from strong blue fluorescence to no fluorescence.

[0077] 4. Application of portable paper base

[0078] The preliminary judgment of diquat concentration can be achieved based on the changes in paper-based fluorescence, which is expected to meet the needs of portable and rapid detection of diquat.

Claims

1. A fluorescent ion probe based on dihydroxynaphthalene, characterized in that: The structure of the fluorescent ion probe is shown in one of the following:

2. A method for preparing the fluorescent ion probe according to claim 1, characterized in that: The method comprises: placing trihexyl (tetradecyl) phosphine hydroxide and dihydroxynaphthalene in a single-necked flask, dissolving them with anhydrous ethanol, fully stirring and reacting them at a temperature of 40 to 120° C. for 5 to 18 hours, evaporating under reduced pressure to remove the solvent after the reaction is completed, and continuing to dry under nitrogen at 60 to 100° C. to obtain a viscous product, which is a fluorescent ion probe.

3. The method according to claim 2, characterized in that The dihydroxynaphthalene includes 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,6-dihydroxynaphthalene and 2,7-dihydroxynaphthalene.

4. The method according to claim 2, characterized in that The molar ratio of trihexyl (tetradecyl) phosphine hydroxide to dihydroxynaphthalene is 2:

1.

5. Use of the fluorescent ion probe according to claim 1 in detecting diquat in actual samples.

6. The use according to claim 5, characterized in that The application is as follows: grinding and crushing the sample to be tested, ultrasonicating and soaking the sample with methanol at 100-350W for 5-30min, centrifuging, adding the fluorescent ion probe to the supernatant, detecting the fluorescence spectrum at 350-550nm, and calculating the diquat content in the sample to be tested based on a standard curve of diquat concentration and fluorescence quenching intensity.

7. The use according to claim 6, characterized in that The fluorescent ion probe is added to the supernatant at a concentration of 5 to 500 μM.

8. The use according to claim 6, characterized in that The standard curve of diquat concentration and fluorescence quenching intensity is prepared according to the following steps: adding a fluorescent ion probe methanol solution into a centrifuge tube, and then adding different volumes of diquat methanol solution to make the probe concentration 50 μM, the final concentration of diquat is 0, 0.5, 1, 2, 2.5, 3, 4, 5, 6, 7, 7.5, 8, 9, 10, 25, 50, 75, 100, 250, 500, 1000 μM, mixing evenly and pouring into a quartz dish, measuring the fluorescence spectrum of 350-550 nm, and preparing a standard curve with the fluorescence quenching intensity of the fluorescent ion probe at 410 nm as the ordinate and the diquat concentration as the abscissa.

9. A diquat test strip made of fluorescent ion probe.

10. The test strip according to claim 9, characterized in that: The test strip is made by soaking filter paper in a fluorescent ion probe methanol solution and then drying it naturally; the method of using the test strip is: immersing the front end of the test strip into the solution to be tested, taking it out after 10 seconds and observing the fluorescence change of the test strip under a 365nm ultraviolet lamp, and comparing the test strip with the fluorescence quenching standard colorimetric card to determine the concentration range of diquat in the solution to be tested; The test strip fluorescence quenching standard colorimetric card is prepared according to the following steps: the front end of the test strip is immersed in a diquat methanol solution with diquat concentrations of 0, 1, 5, 10, 50, 100, 500, and 1000 μM, and the test strip is taken out after 10 seconds, and the change of the fluorescence of the test strip is recorded under a 365nm ultraviolet lamp to prepare a fluorescence quenching standard colorimetric card, in which the color gradually changes from strong blue fluorescence to no fluorescence.

Images