A fluorescent probe for detecting eutrophication of natural water bodies and its preparation method and application

Abstract

The present invention provides a fluorescent probe that can react to the total nitrogen concentration distribution in natural lakes, and its preparation method and application, which belong to the cross-technical field of chemistry and ecology. The fluorescent probe provided by the present invention (referred to as compound MT-BILA) is a new type of probe synthesized based on phenolic compounds. Since its fluorescence intensity is significantly correlated with the total nitrogen content in the water body, it can react to the total nitrogen concentration distribution in the water body of natural lakes by a fluorescence detection method. The compound MT-BILA provided by the present invention is used to react to the total nitrogen concentration distribution in natural lakes, and the operation method is simple and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the cross-technical field of chemistry and ecology, and relates to a fluorescent probe capable of reflecting the total nitrogen concentration distribution in natural lake water, and in particular to a fluorescent probe for detecting eutrophication of natural water bodies, and a preparation method and application thereof. Background Art

[0002] Water is the source of life and is vital to the survival and development of human society. However, with the acceleration of industrialization and the increasing frequency of human activities, water pollution is becoming increasingly serious, posing a huge threat to the ecological environment and human health. Among the many water pollutants, the content of nitrogen is a key indicator.

[0003] Total nitrogen includes various forms of nitrogen compounds in water, such as nitrate, nitrite, ammonia nitrogen and organic nitrogen. Excessive nitrogen content in water may lead to eutrophication, cause algae to reproduce in large numbers, destroy the water ecological balance, reduce the dissolved oxygen content of water, and even affect the quality of drinking water.

[0004] Therefore, accurate and rapid detection of total nitrogen content in water is extremely important for water quality monitoring, environmental protection and water resource management. Traditional total nitrogen detection methods, such as Kjeldahl nitrogen determination method and potassium persulfate oxidation method, have the disadvantages of cumbersome operation, long time consumption, complex sample pretreatment and the use of a large number of chemical reagents, which are difficult to meet the needs of modern environmental monitoring for rapid, real-time and online detection.

[0005] In recent years, fluorescent probe technology has received extensive attention and application due to its advantages of high sensitivity, high selectivity, rapid response, simple operation, and in-situ real-time detection. Fluorescent probes can interact specifically with target analytes, resulting in changes in fluorescence signals. Quantitative detection of target analytes can be achieved by detecting changes in fluorescence intensity.

[0006] Applying fluorescent probe technology to the detection of total nitrogen content in water is expected to overcome the shortcomings of traditional detection methods and provide a new and efficient means for water quality monitoring. However, the fluorescent probes currently used to detect total nitrogen content in water bodies still face some challenges, such as insufficient selectivity, sensitivity that needs to be improved, insufficient stability, and limited applicability in complex water samples. Therefore, the research on fluorescent probes for detecting total nitrogen content in water bodies has important scientific significance and application value. Summary of the invention

[0007] In view of the problems existing in the prior art, the object of the present invention is to provide a fluorescent probe. The fluorescent probe provided by the present invention can reflect the total nitrogen concentration distribution in natural lake water, and has a simple operation method, reliable detection data, and broad application prospects.

[0008] Another object of the present invention is to provide a method for preparing the fluorescent probe.

[0009] The present invention also provides the use of the fluorescent probe in detecting the total nitrogen concentration distribution in natural lake water bodies.

[0010] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0011] The present invention provides a novel fluorescent probe having a structure shown in Formula IV:

[0012]

[0013] Formula IV.

[0014] The present invention also provides a method for preparing a fluorescent probe using the intermediate compound, comprising the following steps:

[0015] (1) 6-methoxy-1-tetralone and POCl3 were subjected to sulfonylation reaction in dimethylformamide (DMF), extracted with dichloromethane (DCM), and dried to obtain intermediate compound I;

[0016] (2) The intermediate compound I is subjected to substitution reaction with 2-cyanomethylbenzimidazole and pyridine in DMF, extracted with DCM, and dried to obtain the intermediate compound II;

[0017] (3) The intermediate compound II and boron tribromide are subjected to a hydrolysis reaction in DCM, and the intermediate compound III is obtained by DCM extraction and purification by silica gel column chromatography;

[0018] (4) The intermediate compound III was subjected to esterification reaction with levulinic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDCI) and 4-dimethylaminopyridine (DMAP) in DCM, and the fluorescent probe was purified by silica gel column chromatography.

[0019] The intermediate compound I used in the synthesis of the fluorescent probe of the present invention has the structure shown in formula I

[0020]

[0021] Formula Ⅰ.

[0022] The present invention further provides an intermediate compound II having a structure shown in Formula II:

[0023]

[0024] Formula II.

[0025] The present invention further provides an intermediate compound III having a structure shown in Formula III:

[0026]

[0027] Formula III.

[0028] Furthermore, in step (1), the molar ratio of POCl3 and 6-methoxy-1-tetralone is 125:28.4; and the sulfidation reaction is carried out at a temperature of 120°C for 24 hours.

[0029] Furthermore, in step (2), the molar ratio of the intermediate compound I, 2-cyanomethylbenzimidazole and pyridine is 4:5:37; and the substitution reaction is carried out at a temperature of 120° C. for 24 hours.

[0030] Furthermore, in step (3), the molar ratio of the intermediate compound II to boron tribromide is 1:5-5.1; and the hydrolysis reaction is carried out at room temperature for 24 hours.

[0031] Furthermore, the molar ratio of the intermediate compound III, levulinic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 4-dimethylaminopyridine is 0.31:0.46:0.49:0.21; and the esterification reaction is carried out at room temperature for 3 hours.

[0032] The present invention also provides application of the fluorescent probe in detecting the total nitrogen concentration distribution in water.

[0033] The reaction scheme of the synthetic fluorescent probe of the present invention is:

[0034]

[0035] The beneficial effects of the present invention are:

[0036] (1) The present invention provides a novel fluorescent probe that can specifically interact with a target analyte, thereby causing a change in the fluorescence signal. The quantitative detection of the target analyte can be achieved by detecting the change in fluorescence intensity;

[0037] (2) The fluorescent probe prepared by the present invention has strong selectivity, sensitivity and stability, can adapt to different complex water samples, and can effectively detect the distribution of total nitrogen content in water bodies, which has important scientific significance and application value;

[0038] (3) The present invention designs and synthesizes a new type of fluorescent probe, optimizes its performance, improves the accuracy and reliability of detection, and further expands its application in actual water samples. It will provide strong technical support for the monitoring and control of total nitrogen in water bodies, help protect water resources, maintain ecological balance and safeguard human health.

[0039] (4) The preparation method provided by the present invention has simple process and strong controllability. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 MT-BILA in DMSO-d6 1 H NMR spectroscopy;

[0041] Figure 2 MT-BILA in DMSO-d6 13 C NMR spectroscopy;

[0042] Figure 3 A map of water sampling sites;

[0043] Figure 4 is the fluorescence spectrum of the water sample added with MT-BILA;

[0044] Figure 5 It is the correlation fitting curve between MT-BILA and total nitrogen;

[0045] Figure 6 Kriging interpolation analysis for MT-BILA;

[0046] Figure 7 Kriging interpolation analysis for total nitrogen. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further explained and illustrated by means of specific embodiments below.

[0048] Unless otherwise specified, the materials used in the present invention are commercially available.

[0049] The present invention provides a fluorescent probe having a structure shown in Formula IV:

[0050]

[0051] Formula IV

[0052] Total nitrogen includes various forms of nitrogen compounds in water, such as nitrate, nitrite, ammonia nitrogen and organic nitrogen, etc. Fluorescent probes can interact specifically with target analytes, resulting in changes in fluorescence signals. Quantitative detection of target analytes can be achieved by detecting changes in fluorescence intensity.

[0053] The present invention provides a method for preparing the fluorescent probe described in the above technical solution, comprising the following steps:

[0054] Step 1: Add DMF to a 100ml round-bottom flask, slowly add POCl3 using a constant pressure dropping funnel under ice bath conditions, and stir the mixed reaction solution for 30min (DMF: POCl3=20ml:125mmol); then dissolve 6-methoxy-1-tetralone in DMF and add the reaction solution (DMF: POCl3=20ml:125mmol) after the solution is completely dissolved; heat the reaction for 24h. DCM extraction and drying to obtain intermediate compound I, which is directly used in the next step.

[0055] Step 2: Place intermediate compound Ⅰ and 2-cyanomethylbenzimidazole into a round-bottom flask containing 10 mL of DMF, continue to slowly drop pyridine, and heat the reaction for 24 hours (intermediate product Ⅰ: 2-cyanomethylbenzimidazole: DMF: pyridine = 25 mmol: 31.25 mmol: 10 ml: 231.25 mmol); extract with DCM, and dry to obtain intermediate compound Ⅱ.

[0056] Step 3: Add intermediate compound II into a 100 mL round-bottom flask, then add DCM to fully dissolve the solid, slowly add boron tribromide, and stir the reaction at room temperature for 24 hours (intermediate compound II: DCM: boron tribromide = 12.21 mmol: 40 ml: 61.31 mmol); extract the crude product with DCM, and then purify it by silica gel column chromatography (DCM: MeOH = 90:10) to obtain intermediate compound III.

[0057] Step 4: Add the intermediate compound III obtained in the previous step to a 100 mL round-bottom flask, then add levulinic acid, EDCI, DMAP, and then add DCM to fully dissolve the solid. Stir the reaction at room temperature for 3 hours (intermediate compound III: levulinic acid: EDCI: DMAP: DCM = 0.31mmol: 0.46mmol: 0.49mmol: 0.21mmol: 20ml). The crude product was purified by silica gel column chromatography (DCM) to obtain the fluorescent probe product.

[0058] After the first step of the sulfurylation reaction generates the intermediate product I, the present invention uses DCM for extraction and drying to obtain a brown oily substance containing an aldehyde group as an intermediate having a structure shown in formula I.

[0059] After the second step substitution reaction generates the intermediate product II, the present invention uses DCM for extraction and drying to obtain a bright yellow solid as the intermediate product II having the structure shown in formula II.

[0060] After the third step hydrolysis reaction generates the intermediate product III, the present invention uses DCM to extract the crude product, and then purifies it by silica gel column chromatography to obtain a yellow solid as the intermediate product III having the structure shown in formula III. In the present invention, the reagent used for the silica gel column chromatography separation is preferably DCM: MeOH=90:10 by volume ratio.

[0061] After the esterification reaction, the present invention preferably purifies the obtained crude product by silica gel column chromatography, and finally obtains a yellow solid product as a fluorescent probe having a structure shown in Formula IV. In the present invention, the reagent used for silica gel column chromatography separation is DCM.

[0062] The present invention provides the application of the fluorescent probe described in the above technical solution in detecting the total nitrogen content in water.

[0063] Example 1

[0064] Add 20 mL of DMF to a 100 ml round-bottom flask, slowly add POCl3 (11.6 mL, 125 mmol) using a constant pressure dropping funnel under ice bath conditions, stir the mixed reaction solution for 30 min, then dissolve 6-methoxy-1-tetralinone (5 g, 28.4 mmol) in 10 mL of DMF, add the reaction solution after the solution is complete, and heat the reaction for 24 h. Extract with DCM and dry to obtain a brown oil containing an aldehyde group, which is the compound shown in formula I, intermediate compound I.

[0065] Example 2

[0066] The oily intermediate compound Ⅰ (25 mmol) and 2-cyanomethylbenzimidazole (4911.88 mg, 31.25 mmol) were placed in a round-bottom flask containing 10 mL of DMF, and pyridine (18.75 mL, 231.25 mmol) was slowly added dropwise. The reaction was heated for 24 h, extracted with DCM, and dried to obtain a bright yellow solid as the compound shown in Ⅱ, intermediate compound Ⅱ (3.8 g), with a yield of 70%.

[0067] Example 3

[0068] The intermediate compound II (3.8 g, 12.21 mmol) was added to a 100 mL round-bottom flask, and 40 mL of DCM was added to fully dissolve the solid. Boron tribromide (5.9 mL, 61.31 mmol) was slowly added, and the reaction was stirred at room temperature for 24 h. The crude product was extracted with DCM and purified by silica gel column chromatography (DCM: MeOH=90:10) to obtain a yellow solid as the compound shown in III, intermediate compound III (569.6 mg), with a yield of 15.2%.

[0069] Example 4

[0070] Add the yellow solid hydroxyl-containing product compound III (95 mg, 0.31 mmol) to a 100 mL round-bottom flask, then add levulinic acid (63.76 mg, 0.46 mmol), EDCI (94 mg, 0.49 mmol), DMAP (26 mg, 0.21 mmol), and then add 20 mL DCM to fully dissolve the solid. Stir the reaction at room temperature for 3 hours. The crude product was purified by silica gel column chromatography (DCM) to obtain a yellow solid product, which is the fluorescent probe MT-BILA shown in IV, about 60 mg.

[0071] Figure 1 MT-BILA in DMSO-d6 1 H NMR spectroscopy, Figure 2 MT-BILA in DMSO-d6 13 C NMR spectroscopy.

[0072] Test Case

[0073] Dissolve the fluorescent probe MT-BILA (0.0409 mg) in 10 ml dimethyl sulfoxide (DMSO) to prepare a 1 mmol / L solution. Take 200 ul of each water sample to be tested in a 2 ml centrifuge tube, add 20 ul of MT-BILA solution, and prepare all water samples; scan the fluorescence spectrum with a fluorescence spectrophotometer to obtain data on the change of fluorescence intensity with wavelength.

[0074] The data were imported into Origin, and a scatter plot of fluorescence intensity and total nitrogen content was drawn. The scatter plot was linearly fitted to obtain the correlation coefficient, and then the correlation between the two was analyzed.

[0075] Import the sorted data into ArcGIS software. Use the spatial analysis tool in ArcGIS, select the Kriging interpolation method, perform interpolation calculations on the fluorescence intensity and total nitrogen content, and then generate interpolation maps of fluorescence intensity and total nitrogen content.

[0076] Figure 3 For the water sampling point map, Figure 4 is the fluorescence spectrum of MT-BILA, Figure 5 is the correlation fitting curve between MT-BILA and total nitrogen, Figure 6 Kriging interpolation analysis for MT-BILA, Figure 7 Kriging interpolation analysis for total nitrogen.

[0077] It can be seen from the above test examples that the fluorescent probe provided by the present invention can reflect the total nitrogen concentration distribution in natural lake water bodies; the operation method is simple and has broad application prospects.

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fluorescent probe, characterized in that It has the structure shown in Formula IV: Formula IV.

2. A method for preparing a fluorescent probe as claimed in claim 1, characterized in that: The following steps are involved: (1) 6-methoxy-1-tetralone and phosphorus oxychloride are subjected to sulfonylation reaction in dimethylformamide, extracted with dichloromethane, and dried to obtain intermediate compound I; The intermediate compound I has the structure shown in Formula I: Formula I; (2) The intermediate compound I is subjected to substitution reaction with 2-cyanomethylbenzimidazole and pyridine in dimethylformamide, extracted with dichloromethane, and dried to obtain the intermediate compound II; The intermediate compound II has the structure shown in Formula II: Formula II; (3) The intermediate compound II and boron tribromide are subjected to a hydrolysis reaction in dichloromethane, and the intermediate compound III is obtained by dichloromethane extraction and purification by silica gel column chromatography; The intermediate compound III has a structure shown in formula III: Formula III; (4) The intermediate compound III is subjected to esterification reaction with levulinic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 4-dimethylaminopyridine in dichloromethane, and the fluorescent probe is purified by silica gel column chromatography.

3. The preparation method according to claim 2, characterized in that: In step (1), the molar ratio of phosphorus oxychloride to 6-methoxy-1-naphthalene ketone is 125:28.4; and the sulfidation reaction is carried out at a temperature of 120° C. for 24 hours.

4. The preparation method according to claim 2, characterized in that: In step (2), the molar ratio of the intermediate compound I, 2-cyanomethylbenzimidazole and pyridine is 4:5:37; and the substitution reaction is carried out at a temperature of 120° C. for 24 hours.

5. The preparation method according to claim 2, characterized in that: In step (3), the molar ratio of the intermediate compound II to boron tribromide is 1:5-5.1; and the hydrolysis reaction is carried out at room temperature for 24 hours.

6. The preparation method according to any one of claims 2 to 5, characterized in that: The molar ratio of the intermediate compound III, levulinic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 4-dimethylaminopyridine is 0.31:0.46:0.49:0.21; the esterification reaction is carried out at room temperature for 3 hours.

7. Use of the fluorescent probe as claimed in claim 1 in detecting the total nitrogen concentration distribution in water.

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