Quick-response cadmium ion long-wavelength fluorescent probe as well as preparation method and application thereof

Abstract

The invention discloses a quick-response cadmium ion long-wavelength fluorescent probe as well as a preparation method and application thereof, and belongs to the technical field of quick analysis and detection of cadmium ions. N, N-bis (2-picolyl) amine is used as a cadmium ion recognition group, an amido bond is used as a linking group to be linked with an acridone luminous parent, and the cadmium ion fluorescent probe DDAC is synthesized. The probe has a large conjugation and strong push-pull electron system, emits long-wavelength fluorescence (630 nm), and effectively eliminates background fluorescence and interference of various ions. The response to cadmium ions is fast (less than 10 s), the detection lower limit is 8.3 nM, and the fluorescence intensity is improved by 30 times after the fluorescent probe is combined with the cadmium ions under the condition that the pH is 4.0-6.0. The probe detection system is applied to rapid detection of the content of cadmium ions in rice food materials, the adding standard recovery rate is 85-105%, the detection error of 10 rice samples is controlled within 20%, various indexes are excellent, and the requirements of the food rapid detection industry are met.

Description

Technical Field

[0001] The invention relates to a fast-response cadmium ion long-wavelength fluorescent probe and a preparation method and application thereof, and belongs to the technical field of fast analysis and detection. Background Art

[0002] Cadmium (Cd 2+ ) is a toxic heavy metal element widely present in the environment, posing a serious threat to ecosystems and human health. Due to the high toxicity, non-degradability and bioaccumulation of cadmium, its presence and migration in the environment have attracted much attention. In the industrial field, cadmium is widely used in industries such as battery manufacturing, electroplating, and pigment production. However, these industrial activities often lead to the emission and leakage of cadmium, which in turn pollutes the soil, water and atmosphere. Cadmium is gradually accumulated in organisms through the food chain, especially in aquatic organisms and crops, and may eventually enter the human body. Once cadmium enters the human body, it can cause damage to the kidneys, liver, bones, and respiratory system, induce a variety of diseases, and may even cause cancer. Therefore, accurate detection of cadmium ions in the environment and organisms is crucial.

[0003] Traditional cadmium ion detection methods, such as atomic absorption spectroscopy (AAS) and inductively coupled plasma mass spectrometry (ICP), have high accuracy and sensitivity, but usually require expensive instruments and equipment, complex sample pretreatment processes, and professional operators. In recent years, fluorescent probe detection methods have been favored by scientific researchers due to their high sensitivity, low toxicity, and simple operation. The cadmium ion fluorescent probes reported in the literature generally have emission wavelengths below 600 nm (Sens. Actuators, B, 2017, 249, 3 86 ~394; Luminescence, 2017, 32, 1405~1410.), long response time (Spectrochim. Acta, Part A, 2020, 226, 117600.), high detection limits (J. Photochem. Photobiol., A, 2018, 353, 77 ~85; RSC Adv., 2017, 7, 23127~23135.), poor biocompatibility, and are most susceptible to interference from other metal ions, especially Zn 2+ This will seriously affect the practical application of probe molecules in the field of in vivo detection and food safety detection. Therefore, it is particularly important to design a small molecule fluorescent probe of cadmium ions with long wavelength, good biocompatibility, fast response and strong selectivity. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, provide a cadmium ion fluorescent probe molecule with strong selectivity, high sensitivity, and rapid and convenient detection, and also provide a preparation method and application of the cadmium ion fluorescent probe. Using DPA as the cadmium ion recognition group and an amide bond as a connecting group to link with an acridone photomatrix, a cadmium ion fluorescent probe DDAC was synthesized, which can effectively eliminate background fluorescence and interference from multiple ions. It has the characteristics of accelerated response to cadmium ions, low detection limit, and high sensitivity under slightly acidic conditions; in the rapid detection of cadmium ion content in rice ingredients, the spiked recovery rate and detection error both meet the requirements of the food rapid inspection industry. In order to solve the above technical problems, the present invention adopts the following technical scheme: 7-amino-1,3-dichloro-9,9-dimethylacridine-2(9hydrogen)-one is selected to react with di(pyridin-2-ylmethyl)glycine to prepare a probe molecule. The compound and Cd are analyzed by ultraviolet absorption spectroscopy and fluorescence emission spectroscopy. 2+ interaction, and found that the compound has excellent Cd 2+ A fluorescent probe for detecting cadmium ions, the molecular formula of which is C 29 H 25 Cl2N5O2, the specific structural formula is as follows:

[0005]

[0006] A method for preparing a fluorescent probe for detecting cadmium ions, the synthetic route of the fluorescent probe is as follows:

[0007] (1) Compound 1 and Compound 2 were dissolved in a mixed solution of tetrahydrofuran and water, and an aqueous NaOH solution was added dropwise under an ice bath. When the solution was cooled to room temperature, saturated ammonium chloride and ethyl acetate solutions were added, and the mixture was stirred vigorously. After extraction and washing, the ethyl acetate solution was washed with an aqueous solution of sodium hydrosulfite, dried, and concentrated to obtain a brown tar-like product 3;

[0008] (2) Dissolve the product 3 in methanol, add hydrochloric acid solution under nitrogen protection with stirring, then react at 5-15°C, warm to room temperature after the reaction, and extract and wash the obtained product 4 in ethyl acetate solution. ;

[0009] (3) adding a sodium periodate aqueous solution dropwise to the ethyl acetate solution of the product 4, and after the reaction is completed, extracting, drying, and distilling to obtain a red-black solid product DDAN;

[0010] (4) DDAN and compound 5 are dissolved in dichloromethane, DMAP and EDC·HCl are added, and the mixture is reacted at room temperature. After the reaction is completed, the mixture is distilled under reduced pressure and purified by column chromatography to obtain a yellow product DDAC. Further, the method specifically comprises the following steps: (1)

[0011] Compound 1 and compound 2 were dissolved in a mixed solution of tetrahydrofuran and water, and a 2.0 M NaOH aqueous solution was slowly added dropwise under an ice bath. When the solution was cooled to room temperature, saturated ammonium chloride and ethyl acetate solutions were poured into the water and stirred vigorously. The organic phase was extracted and washed with a saturated ammonium chloride solution, and the ethyl acetate solution was washed with an aqueous solution of dissolved hydrosulfite. The mixture was dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain a brown tarry product 3. (2)

[0012] The product 3 was dissolved in an appropriate amount of methanol, and a 2.0 M hydrochloric acid solution was slowly added with stirring under nitrogen protection, followed by reaction at 10 °C for 2 h, cooling to room temperature, extraction with ethyl acetate, and washing with saturated brine to obtain an ethyl acetate solution of the product 4. (3)

[0013] Weigh an appropriate amount of sodium periodate, dissolve it in water, slowly stir and add it dropwise to the ethyl acetate solution of the product 4 in the previous step. After the reaction is completed, extract it three times with saturated brine, dry it with anhydrous sodium sulfate, and distill it under reduced pressure. The obtained solid powder is redissolved in ethyl acetate, and ammonia water is added to heat under reflux. After the reaction is completed, the solvent is removed by distillation under reduced pressure to obtain a red-black product DDAN. (4)

[0014] DDAN and compound 5 were weighed and dissolved in dichloromethane, DMAP and EDC·HCl were added, and the mixture was reacted at room temperature. After 48 hours of reaction, the reaction was completed as detected by TCL, and the mixture was distilled under reduced pressure and purified by column chromatography (dichloromethane: anhydrous methanol = 50:1) to obtain a yellow product DDAC.

[0015] In step (1), the molar ratio of compound 1 to compound 2 is 1:1.

[0016] In step (4), the molar ratio of compound DDAN to compound 5 is 1:(1.1-1.2).

[0017] The fluorescent probe is applied to the detection of cadmium ions.

[0018] Furthermore, when the fluorescent probe is used for the detection of cadmium ions, the pH is controlled within the range of 4.0 to 6.0.

[0019] Furthermore, the fluorescent probe is used for the detection of cadmium ions in food. Preferably, it is used for the rapid detection of cadmium ions in rice food raw materials.

[0020] Furthermore, the fluorescent probe is used to qualitatively or quantitatively detect the cadmium ion content in food.

[0021] Beneficial effects of the present invention:

[0022] The emission wavelength of the acridine derivative fluorescent probe DDAC reaches 630 nm, with strong anti-background interference and good stability; no Cd is added 2+ The fluorescence is very weak. When Cd is added to the system 2+ After that, the pyridine N, amine N and amide O in the probe molecule react with Cd 2+ The original PET effect was inhibited and a very strong fluorescence was released. 2+ The fluorescence intensity increased 30 times, indicating the high sensitivity of the probe.

[0023] Due to Cd 2+ With Zn 2+ Similar in structure, the selectivity of cadmium ion probes is often affected by zinc ions. 2+ The interference is mainly caused under neutral and weak alkaline conditions. The possible reason is that under neutral and weak alkaline conditions, OH - Also involved in the probe and Zn 2+ When tested under acidic conditions, Zn 2+ The interference with the cadmium ion probe is not obvious, which is mainly due to the Cd 2+ The ionic radius (0.92 Å) is larger than that of Zn 2+ Ionic radius (0.74 Å), weaker coordination ability than Zn 2+ The probe of the present invention has good reaction ability to cadmium ions in the range of pH = 4.0 to 6.0, ensuring the detection of Cd in food samples. 2+ reliability.

[0024] Probe detection of Cd in 10 types of rice ingredients (from central China, east China, and northeast China) 2+ The spike recovery rate can be controlled between 85% and 107%, and the error of ICP test on the same sample is also controlled within 20%, both meeting the industry's requirements for rapid food safety testing.

[0025] (1) The compound of the present invention has simple synthesis steps, high yield, convenient purification, less time consumption, can be used for large-scale synthesis, and has good application value.

[0026] (2) The emission wavelength of the acridine derivative fluorescent probe of the present invention is relatively long (Em = 630 nm), which can effectively avoid the interference of biomass in the sample solution of the extracted solid. The same food materials from different origins can be calibrated and detected using the same working curve.

[0027] (3) Acridine derivatives Cd of the present invention 2+ Fluorescent probes without Cd 2+ When reacting, it has no fluorescence and good stability. 2+ After binding, it produces strong fluorescence, which will 2+ The fluorescence intensity gradually increases with the increase of concentration, and the fluorescence intensity can be increased up to 30 times.

[0028] (4) The present invention treats Cd 2+ It has a specific selectivity and eliminates Zn with similar structure through the exploration of detection conditions. 2+ Cd 2+ Other metal cations, anions or amino acid small molecules have no effect on the detection.

[0029] (5) The present invention can be tested in acetic acid-sodium acetate buffer, and the applicable pH range is between 4.0 and 6.0, which can achieve the detection of Cd 2+ Real-time monitoring.

[0030] (6) The probe of the present invention can be used to detect Cd in actual food materials 2+ The spike recovery rate can be basically controlled between 85% and 107%, and the error is controlled within 20% or ±10 µg / kg. Food can be tested and it meets the regulations for rapid food safety testing.

[0031] The detection limit of the fluorescent probe DDAC for detecting cadmium ions in water is 8.3 nM (1.0 µg / L, reaching 5.0 µg / kg after extraction and dilution), which is lower than the national limit standards for cadmium ion content in various food ingredients; the probe binds to cadmium ions for a short time, <10 s, which greatly shortens the detection time and truly realizes rapid detection.

[0032] The fluorescent probe DDAC of the present invention has the advantages of strong resistance to biomass background interference, high selectivity, low detection limit, and rapid reaction, which solves the previously reported detection of Cd 2+ The defects of fluorescent probes. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 For the probe DDAC 1 H NMR spectrum.

[0034] Figure 2 For the probe DDAC 13 C NMR spectrum.

[0035] Figure 3 HRMS spectrum of probe DDAC.

[0036] Figure 4 This is the UV-visible absorption spectrum of the probe DDAC before and after the reaction with cadmium ions.

[0037] Figure 5 This is the fluorescence intensity change spectrum of the probe DDAC before and after reacting with cadmium ions at different pH values.

[0038] Figure 6 This is the fluorescence intensity change spectrum over time after the probe DDAC is reacted with the addition of cadmium ions.

[0039] Figure 7 This is the fluorescence emission spectrum of the probe DDAC after reacting with different concentrations of cadmium ions.

[0040] Figure 8 This is a selective interference test between the probe DDAC and common cations and anions. Detection conditions: acetic acid-sodium acetate buffer (pH = 4.5, 10 mM), probe concentration 10 µM, Ex = 465 nm, Em = 630 nm. Samples 1-17 in the figure are Ba(NO3)2, Ca(NO3)2, NaNO3, KNO3, Mn(NO3)2, NiNO3, Fe(NO3)3, Cu(NO3)2, CoNO 3、 Zn(NO3)2, AgNO3, Na2SO4, Na2SO3, NaClO, NaNO3, NaNO2, sample No. 17 is cadmium ion.

[0041] Fig. 9 This is a test of the selective interference between the probe DDAC and various amino acids. Detection conditions: acetic acid-sodium acetate buffer (pH = 4.5, 10 mM), probe concentration 10 µM, Ex = 465 nm, Em = 630 nm, samples 1-12 in the figure are Cys, Trp, Phe, Leu, GSH, Aln, Val, Met, Thr, Asp, ILE, and sample 12 is cadmium ion.

[0042] Fig.10 The working curve of the probe DDAC for detecting cadmium ions in water, detection conditions: acetic acid-sodium acetate buffer (pH= 4.5, 10 mM), probe concentration 10 µM, Ex = 465 nm, Em = 630 nm, cadmium ion concentrations 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, 10.0 μM. The working curve is: Y = 0.002612X – 0.2867, R 2 = 0.9963.

[0043] Fig.11In order to add different amounts of cadmium ions to the extract of red rice sample-1, a standard working curve for the detection of cadmium ion content in red rice by probe DDAC was prepared. Acetic acid-sodium acetate buffer (pH = 4.5, 10 mM), probe concentration 10 µM, Ex = 465 nm, Em = 630 nm, equivalent to cadmium ion content of 5.5, 10, 20, 50, 100, 200, 300, 500 µg / kg. The working curve obtained was: Y = 1.985X – 391.9, R 2 = 0.9942.

[0044] Fig.12 In order to add different amounts of cadmium ions to the extract of rice sample-1, a standard working curve for the detection of cadmium ion content in rice by probe DDAC was prepared. Acetic acid-sodium acetate buffer (pH = 4.5, 10 mM), probe concentration 10 µM, Ex = 465 nm, Em = 630 nm, equivalent to cadmium ion content of 3.5, 10, 20, 50, 100, 200, 300, 500 µg / kg. The working curve obtained is: Y = 1.126X – 219.1, R 2 = 0.9967. DETAILED DESCRIPTION

[0045] Example 1 Synthesis of Probe (1) Synthesis of Compound 3:

[0046]

[0047] Compound 1 (4.56 g, 30 mmol) and compound 2 (6.3 g, 30 mmol) were dissolved in a mixed solution of tetrahydrofuran and water, and a 2M NaOH aqueous solution (30 mL) was slowly added dropwise under an ice bath. When the solution was cooled to room temperature, saturated ammonium chloride and ethyl acetate solutions were poured into the water and stirred vigorously. The organic phase was extracted and washed with a saturated ammonium chloride solution, and the ethyl acetate solution was washed with an aqueous solution (250 mL) containing hydrosulfite (50 g, 287 mmol). The mixture was dried over anhydrous sodium sulfate and concentrated under reduced pressure to obtain 7.1 g of product 3 as a brown tar with a yield of 63%.

[0048] (2) Synthesis of compound 4:

[0049] The product 3 was dissolved in methanol (40 mL), and 2.0 M hydrochloric acid solution (250 mL) was slowly added with stirring under nitrogen protection, followed by reaction at 10 °C for 2 h, cooling to room temperature, extraction with ethyl acetate (250 mL), and washing with saturated brine to obtain an ethyl acetate solution of the product 4.

[0050] (3) Synthesis of compound DDAN:

[0051] Sodium periodate (7.2 g, 33.3 mmol) was weighed and dissolved in water. The solution was slowly added dropwise to the ethyl acetate solution of the product 4 in the previous step with stirring. After the reaction was completed, the solution was extracted three times with saturated brine, dried over anhydrous sodium sulfate, and distilled under reduced pressure. The obtained solid powder was redissolved in ethyl acetate, and ammonia water was added and heated to reflux. After the reaction was completed, the solvent was removed by distillation under reduced pressure to obtain a red-black product DDAN.

[0052] (4) Synthesis of compound DDAC:

[0053] DDAN (50 mg, 0.163 mmol) and compound 5 (47 mg, 0.183 mmol) were dissolved in dichloromethane, and EDC·HCl (50 mg, 0.262 mmol) and DMAP (30 mg, 0.244 mmol) were added and stirred at room temperature for 48 h. The reaction could not be completely carried out, and the solvent was removed by vacuum distillation. The product was separated and purified by silica gel column chromatography, and the eluent was V (dichloromethane): V (anhydrous methanol) = 50:1. Compound DDAC was obtained as a red solid powder of 5 mg, with a yield of 10%. 1 H NMR (500MHz, Chloroform-d) δ 11.38 (s, 1H), 8.66 (d, J = 4.8 Hz, 2H), 8.19 (d, J =2.0 Hz, 1H), 7.76 (s, 1H), 7.70 – 7.61 (m, 4H), 7.28 (s, 2H), 7.27 –7.16 (m,2H), 3.96 (s, 4H), 3.54 (s, 2H), 1.93 (s, 6H). Figure 1 shown.

[0054] Example 2: pH versus probe DDAC for determination of Cd 2+ Impact test

[0055] In order to study the effect of pH on fluorescence intensity, the fluorescence intensity in the pH range of 3.0 to 12.0 was investigated. Figure 5 As shown. (The concentration of the fluorescent probe is 10 μM, Cd 2+ The concentration is 10.0 μM. As shown in the figure, without adding Cd 2+ Since the fluorescence of the probe parent was quenched, the fluorescence intensity of the probe did not change significantly with the increase of pH. 2+After that, it was found that the fluorescence intensity gradually decreased with the increase of pH. The fluorescence intensity remained basically unchanged in the range of pH = 4.0 to 6.0. At pH > 7.0, the fluorescence gradually weakened. Therefore, this study determined that food safety testing was carried out under the condition of pH = 4.5, and 100mmol / L acetic acid-sodium acetate buffer was used to maintain this pH, which ensured the use of probe DDAC to detect Cd in food safety. 2+ reliability.

[0056] Example 3: Fluorescent probes DDAC and Cd 2+ Solution preparation

[0057] The synthesized probe DDAC was dissolved in dimethyl sulfoxide (DMSO) to prepare a 10 mM mother solution, and a certain amount of cadmium nitrate tetrahydrate was dissolved in distilled water to prepare a 1 M mother solution. Acetic acid and sodium acetate were dissolved in 400 mL of distilled water and fixed to volume in a 500 mL volumetric flask to prepare a 100 mM acetic acid-sodium acetate buffer solution with a pH of 4.5.

[0058] Example 4: DDAC fluorescent probe and different concentrations of Cd 2+ Determination of the spectral properties of

[0059] The UV-absorption spectrum was tested in a buffer system of DMF:acetic acid buffer (pH=4.5)=5:95 (v / v). Figure 4 It can be seen that when the probe concentration is 10 μM, Cd 2+ The concentration is 10.0 μM. It can be seen that when no Cd is added 2+ When 10.0 μM Cd 2+ After that, the absorption enhancement was clearly visible at 468nm, and the absorbance reached 0.25, so it can be used as the best absorption peak in this experiment. The fluorescence spectrum was measured in a buffer system of DMF: acetic acid buffer (pH = 4.5) = 5:95, see Figure 7 The obtained fluorescence spectrum is shown in Figure 7 As shown. The probe concentration was 10 μM, Cd 2+ The concentrations of were set to 0μM, 0.1μM, 0.2μM, 0.3μM, 0.4μM, 0.5μM, 0.6μM, 0.7μM, 0.8μM, 0.9μM, 1.0μM, 2.0μM, 3.0μM, 4.0μM, 5.0μM, 10.0μM. 2+ When the fluorescence intensity is almost invisible, but with the increase of Cd 2+ As the concentration increases, the fluorescence intensity gradually increases. 2+ The addition of Cd leads to the restoration of the probe PET effect, which results in the fluorescence turning on.2+ When the concentration increased to 10.0 μM, the fluorescence intensity reached the highest level, and the fluorescence intensity increased by 30 times.

[0060] Example 5: Fluorescent probe DDAC and Cd 2+ Time determination of response

[0061] In order to study the fluorescence probe on Cd 2+ We investigated the response time of the fluorescent probe in 10.0 μM Cd 2+ The fluorescence spectrum of the Figure 6 As shown in the figure, it can be seen that when Cd is added 2+ There is an obvious fluorescence change when the fluorescence intensity increases, and the fluorescence intensity basically does not increase with time. After 10 seconds, the fluorescence intensity remains basically unchanged and tends to be stable and no longer changes, which shows that this fluorescent probe has good stability. Therefore, real-time monitoring can be performed in actual samples.

[0062] Example 6: Fluorescent probe DDAC for Cd 2+ Selective exploration

[0063] Various common metal cations (1.Ba 2+ 2.Ca 2+ 3.Cd 2+ , 4.K + 5.Mn 2+ 6.Na + 7.Ni + 8.Fe 3+ 9.Cu 2+ 10. Zn 2+ 11. Ag + 、17.Cd 2+ )(10.0μM) and various anions (12.SO4 2- 13. SO3 2- 14.ClO - 15. NO3 - 、16. NO2 - ) and other amino acid molecules (1. GSH, 2. Cys, 3. Phe, 4. Ala, 5. Met, 6. Leu, 7. Trp, 8. Thr, 9. Asp, 10. Val, 11. ILE, 12. Cd 2+ ) to explore the changes in fluorescence intensity before and after the reaction. The results are as follows Figure 8 , 9 shows that the fluorescence intensity did not change significantly when metal cations and other anions were added, but when Cd was added to the probe solution 2+After that, the fluorescence intensity was found to be significantly enhanced, and there was an obvious emission peak at 630nm. 2+ Zn, the most interfering 2+ The fluorescence intensity of Cd 2+ It has unique selectivity and can detect actual samples.

[0064] Example 7: Method for extracting cadmium ions from rice ingredients

[0065] Use a grinder to grind rice ingredients into powder, take 0.6 g of rice powder and put it in a 5 mL centrifuge tube, add 2.0 mL of 0.3% nitric acid solution, shake and mix for 10 min, centrifuge for 7 min, and take the supernatant for detection.

[0066] Example 8: Method for detecting cadmium ion content in rice food using ICP

[0067] Ten rice food samples were purchased from different regions (Central China, East China, and Northeast China) and divided into: Rice Sample 1, Rice Sample 2, Rice Sample 3, Rice Sample 4, Rice Sample 5, Red Rice Sample 1, Red Rice Sample 2, Red Rice Sample 3, Red Rice Sample 4, and Red Rice Sample 5. After digestion, the cadmium ion content was detected using an ICP instrument. The results are shown in Table 2.

[0068] Example 9

[0069] Detection of cadmium ions in rice flour extract using fluorescent probe DDAC Method: From the extract prepared in Example 2, take 1275 µL and put it into a 2.0 mL centrifuge tube, add 150 μL acetic acid-sodium acetate buffer (pH = 4.5, 100 mM), then add 75 μL probe DDAC solution (0.2 mM in DMF), mix well and pour into a micro cuvette, and detect the fluorescence intensity at an excitation wavelength of 465 nm.

[0070] Fig.11 In order to add different amounts of cadmium ions to the extract of red rice sample-1, a standard working curve for the detection of cadmium ion content in red rice by probe DDAC was prepared. Acetic acid-sodium acetate buffer (pH = 4.5, 10 mM), probe concentration 10 µM, Ex = 465 nm, Em = 630 nm, equivalent to cadmium ion content of 5.5, 10, 20, 50, 100, 200, 300, 500 µg / kg. The working curve obtained was: Y = 1.985X – 391.9, R 2 = 0.9942.

[0071] Fig.12In order to add different amounts of cadmium ions to the extract of rice sample-1, a standard working curve for the detection of cadmium ion content in rice by probe DDAC was prepared. Acetic acid-sodium acetate buffer (pH = 4.5, 10 mM), probe concentration 10 µM, Ex = 465 nm, Em = 630 nm, equivalent to cadmium ion content of 3.5, 10, 20, 50, 100, 200, 300, 500 µg / kg. The working curve obtained is: Y = 1.126X – 219.1, R 2 = 0.9967.

[0072] The fluorescence intensity of the red rice sample was brought into Fig.11 The working curve of the rice sample is brought into Fig.12 The cadmium ion content was calculated using the working curve.

[0073] Example 10: Test on recovery rate of spiked cadmium ions in rice noodle samples

[0074] Take 0.6 g of rice flour and place it in a 5 mL centrifuge tube, add an appropriate amount of cadmium nitrate standard solution, and place it in a cool place at room temperature to dry. Extract according to the method in Example 2 above, then detect the fluorescence intensity and calculate the cadmium ion content according to Example 4, and finally calculate the spiked recovery rate. The results are shown in Table 1.

[0075] Table 1 Spike recovery test µg / kg

[0076]

[0077] Example 11: Testing and comparison of cadmium ion content in rice samples

[0078] According to the methods of Examples 2 and 4 above, the cadmium ion content in 5 red rice samples and 5 rice samples was tested and compared with the ICP test results, see Table-2.

[0079] Table-2 Detection of cadmium ion content in rice food, comparison of µg / kg

[0080]

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fast-response cadmium ion long-wavelength fluorescent probe, characterized in that: The structural formula of the probe is as follows: 。 2. The method for preparing a fast-response cadmium ion long-wavelength fluorescent probe according to claim 1, characterized in that: It includes the following steps: （1） ； Compound 1 and compound 2 were dissolved in a mixed solution of tetrahydrofuran and water, and an aqueous NaOH solution was added dropwise under an ice bath. When the solution was cooled to room temperature, saturated ammonium chloride and ethyl acetate solutions were added, and the mixture was stirred vigorously. After extraction and washing, the ethyl acetate solution was washed with an aqueous solution of sodium hydrosulfite, dried, and concentrated to obtain a brown tar-like product 3. （2） ； Dissolve the product 3 with methanol, add hydrochloric acid solution under nitrogen protection with stirring, then react at 5-15°C, warm to room temperature after the reaction, extract and wash the obtained product 4 with ethyl acetate solution; （3） ； A sodium periodate aqueous solution is added dropwise to the ethyl acetate solution of the product 4. After the reaction is completed, extraction, drying and distillation are performed to obtain a red-black solid product DDAN; （4） ； DDAN and compound 5 were dissolved in dichloromethane, 4-dimethylaminopyridine and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were added, and the mixture was reacted at room temperature. After the reaction was completed, the mixture was distilled under reduced pressure and purified by column chromatography to obtain a yellow product DDAC.

3. The method for preparing a fast-response cadmium ion long-wavelength fluorescent probe according to claim 2, characterized in that: In the step (1), the molar ratio of compound 1 to compound 2 is 1:

1.

4. The method for preparing a fast-response cadmium ion long-wavelength fluorescent probe according to claim 2, characterized in that: In the step (4), the molar ratio of DDAN to compound 5 is 1:(1.1-1.2).

5. The use of a fast-response cadmium ion long-wavelength fluorescent probe according to claim 1, characterized in that: The fluorescent probe is applied to the detection of cadmium ions.

6. The use of a fast-response cadmium ion long-wavelength fluorescent probe according to claim 5, characterized in that: When the fluorescent probe is used for detecting cadmium ions, the pH is controlled within the range of 4.0 to 6.

0.

7. The use of a fast-response cadmium ion long-wavelength fluorescent probe according to claim 6, characterized in that: The fluorescent probe is applied to the detection of cadmium ions in food.

8. The use of a fast-response cadmium ion long-wavelength fluorescent probe according to claim 7, characterized in that: The fluorescent probe is used for qualitatively or quantitatively detecting the cadmium ion content in food.

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