A Fluorescent Probe and Its Application in Detecting Anionic Surfactant SDS

Abstract

The present invention discloses a fluorescent probe and its application in detecting anionic surfactant SDS. The structural formula of the fluorescent probe is #imgabs0#. The fluorescent probe has a reactive group that can electrostatically interact with SDS to cause aggregation-induced fluorescence. At the same time, the molecular structure also has a certain hydrophobic structure, forming a certain hydrophobic environment within the molecule, eliminating the interference of many other inorganic anions in the surfactant detection process. Compared with the national standard method and other reported methods, the present method has the characteristics of high sensitivity, good selectivity, and rapid response. In addition, the probe has good water solubility, and the detection process does not require repeated extraction with organic solvents, which is environmentally friendly. It can be directly used for the detection of SDS in water samples, and can also be used for the rapid detection of SDS residues on tableware surfaces.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescent probes and anionic surfactant detection, and in particular to a fluorescent probe and application thereof in detecting anionic surfactant SDS. Technical Background

[0002] Surfactants, with their hydrophilic and hydrophobic ends, possess excellent properties in many areas, including wetting, emulsification, foaming, dispersion, and solubilization. Consequently, they are widely used in textiles, food, pesticides, and cosmetics. Anionic surfactants, which account for over 40% of total usage, play a crucial role in many cleaning and washing products, such as laundry detergents, liquid laundry detergents, and dishwashing liquids. However, anionic surfactants can be irritating to the eyes and skin, and within organisms, they can affect the exchange of substances between cell membranes and the outside world and inhibit enzyme activity. They can produce foam even at very low concentrations in the environment, causing water contamination to a certain extent. Current water purification methods are ineffective in removing these substances, ultimately impacting human health through the food chain.

[0003] Numerous methods are currently available for detecting anionic surfactants, including flow injection analysis, biosensor analysis, gas chromatography-mass spectrometry, and high-performance liquid chromatography. However, these methods require expensive instrumentation and complex procedures, making them unsuitable for the current demand for rapid, environmentally friendly, and timely detection. Furthermore, the method for detecting anionic synthetic detergents, as outlined in "GBT 5750.4-2006 Standard Test Methods for Drinking Water - Sensory Properties and Physical Indicators," involves an electrostatic reaction between methylene blue and anionic surfactants, and requires repeated extraction of the resulting conjugate with chloroform. This cumbersome and lengthy process also presents interference from substances that react with methylene blue, such as phenols, organic sulfates, sulfonates, phosphates, carbonates, and metal ions, making it difficult to guarantee the accuracy and reproducibility of test results. Developing efficient, rapid, and highly selective methods for detecting anionic surfactants is a critical issue that urgently needs to be addressed in this field.

[0004] Therefore, it is particularly important to develop a rapid detection method for anionic synthetic detergents that is simple to operate, harmless to health, and time-saving. Summary of the Invention

[0005] The present invention proposes a fluorescent probe and its application in detecting anionic surfactant SDS. The fluorescent probe is a novel tetraphenylethylene derivative probe. The tetravalent positive ion TPE-4 of the fluorescent probe is +Through the fluorescent luminescence effect caused by electrostatic interaction with the anionic surfactant SDS, specific identification and detection of SDS (sodium dodecyl sulfate) is achieved. Compared with the national standard method and other reported methods, this method has the characteristics of high sensitivity, good selectivity, and rapid response. It can be used for direct detection of SDS in water samples and for rapid detection of residual SDS on the surface of tableware.

[0006] The technical solution for realizing the present invention is:

[0007] A fluorescent probe with the structural formula

[0008] The preparation method of the fluorescent probe comprises the following steps:

[0009] S1: Tetrakis-(4-bromophenyl)ethylene, potassium ferricyanide trihydrate, sodium carbonate, and palladium acetate were dissolved in DMAc, heated to 100°C under nitrogen and refluxed for 10 h. After cooling to room temperature, the crude product was obtained by filtration, extraction, and drying. The crude product was then purified by silica gel column chromatography to obtain a yellow powdery solid.

[0010] S2: The yellow solid obtained in step S1 was dissolved in ultra-dry THF at -40°C under nitrogen protection, and the LiHMDS solution was slowly added. The mixture was returned to room temperature and stirred overnight. Then, the mixture was cooled to 0°C and an ethanol solution of hydrochloric acid was slowly added to obtain a white solid. The solid was separated by centrifugation and then added to ethanol. Ultrasonication was performed for 1 hour. The solid was then centrifuged, washed with ethanol, and vacuum dried to obtain the final product.

[0011] The fluorescent probe is used in detecting anionic surfactant SDS.

[0012] The above application specifically includes the following steps:

[0013] (1) Dissolve the fluorescent probe in DMSO to prepare a 2 mM probe stock solution;

[0014] (2) Add the probe stock solution to HEPES buffer (10 mM, pH = 7.0), and then add different equivalents of SDS to make the final concentration of the fluorescent probe 10 μM. After mixing, let it stand for 1 min. Use 350 nm as the excitation wavelength to measure the fluorescence emission spectra of each solution before and after adding SDS;

[0015] (3) Observe the change in fluorescence intensity of the solution at 460 nm before and after the interaction of the fluorescent probe with SDS;

[0016] (4) Add the probe stock solution and the sample solution to be tested to a HEPES buffer solution at pH 7.0, so that the final concentration of the fluorescent probe is 10 μM and the final concentration of HEPES is 10 mM. After mixing, let it stand for 1 min. Use 350 nm as the excitation wavelength and measure the fluorescence intensity of the test solution at 460 nm. The SDS content in the sample solution to be tested is obtained based on the fluorescence intensity.

[0017] Changes in fluorescence intensity with SDS concentration: As the SDS concentration increases, the fluorescence intensity of the fluorescent probe at 460 nm in the solution continues to increase, and when the SDS concentration is in the range of 5-60 μM, there is a good linear relationship between the fluorescence intensity and the SDS concentration. The linear equation is y = -244.1967 + 49.4701x, where y represents the fluorescence intensity and x represents the SDS concentration (μM).

[0018] The fluorescent probe is used to detect the SDS content in water.

[0019] The fluorescent probe is used to detect the SDS residue on tableware.

[0020] The fluorescent probe can be used to detect the SDS concentration in washing products.

[0021] The beneficial effects of the present invention are:

[0022] (1) The probe designed in the present invention is a novel fluorescent probe based on an amidine functional group as a recognition group and tetraphenylethylene as a fluorophore. It has good photostability and pH stability. The probe itself does not fluoresce in aqueous solution, but exhibits strong blue fluorescence after reacting with the anionic surfactant sodium dodecyl sulfate (SDS).

[0023] (2) The probe designed in the present invention only responds to the anionic surfactant SDS, showing strong blue fluorescence, and has a weak response to high concentrations of sodium dodecylbenzene sulfonate. It has no response to other types of anionic surfactants, cationic surfactants, neutral surfactants, amphoteric surfactants, metal ions, amino acids, etc., and can specifically recognize the anionic surfactant sodium dodecyl sulfate;

[0024] (3) The probe designed in the present invention is simple to operate, has a fast reaction speed, and has obvious fluorescence color changes when detecting anionic surfactants. It can be promoted and applied in the field of rapid detection of anionic synthetic detergents in tableware (drinking utensils) and drinking water. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 The fluorescent probe prepared in Example 1 1 H NMR spectrum;

[0027] Figure 2 The graph shows the change of fluorescence intensity before and after the reaction of 10 μM fluorescent probe with 50 μM SDS under different pH conditions;

[0028] Figure 3 The graph shows the change of fluorescence emission intensity over time in 10 mM HEPES solution with a fluorescent probe concentration of 10 μM and an excitation wavelength of 350 nm before and after the addition of 50 μM SDS.

[0029] Figure 4 The fluorescence emission spectra of the fluorescent probe were obtained in 10 mM HEPES solution with a concentration of 10 μM and an excitation wavelength of 350 nm after adding different concentrations of SDS for 1 minute. Figure 4 A), and the linear fitting diagram between SDS concentration and fluorescence intensity ( Figure 4 B);

[0030] Figure 5 The fluorescence spectra of the probe after interaction with SDS and other interfering substances were shown in 10 mM HEPES solution with a concentration of 10 μM and an excitation wavelength of 350 nm. The final concentration of SDS was 20 μM and the final concentration of other interfering substances was 100 μM.

[0031] Figure 6 The particle size distribution diagram before and after the action of 10 μM fluorescent probe and 50 μM SDS; DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1 Preparation of fluorescent probe

[0034] S1: Dissolve tetra(4-bromophenyl)ethylene (1 g), potassium ferricyanide trihydrate (760.2 mg), sodium carbonate (653 mg), and palladium acetate (1.4 mg) in 10 mL of DMAc. Heat to 100°C and reflux for 10 h under nitrogen. After cooling to room temperature, filter and rinse with dichloromethane. Collect the filtrate, dilute with dichloromethane, and extract with saturated brine. Dry with anhydrous sodium sulfate, and evaporate under low pressure to obtain a crude product. Purify by silica gel column chromatography using dichloromethane as the eluent to obtain a yellow powdery solid.

[0035] S2: The yellow solid obtained in step S1 was dissolved in ultra-dry THF at -40°C under nitrogen protection, and 37 mL of a 1.0 M LiHMDS solution (solvent: THF) was slowly added. The mixture was returned to room temperature and stirred overnight. The mixture was then cooled to 0°C and an ethanol solution of hydrochloric acid was slowly added (10 mL of HCl was added to 100 mL of ethanol) to obtain a white solid. The solid was separated by centrifugation and then added to 10 mL of ethanol. Ultrasonication was performed for 1 hour, and the solid was centrifuged, washed with ethanol, and vacuum dried to obtain the final fluorescent probe product.

[0036] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the fluorescent probe prepared in Example 1, and the spectrum shows the following data: 1 HNMR (600MHz, DMSO-d6) δ9.30 (d, J = 150.9Hz, 8H), 7.76 (s, 4H), 7.24 (s, 4H).

[0037] Example 2 Changes in fluorescence intensity before and after the interaction of the fluorescent probe with SDS under different pH conditions

[0038] Solution preparation: HEPES buffer solutions with a pH of 1-12 were prepared, all at a concentration of 10 mM; the fluorescent probe prepared in Example 1 was dissolved in DMSO to prepare a probe stock solution with a concentration of 2 mM; and an SDS solution with a concentration of 2 mM was prepared using ultrapure water as the solvent.

[0039] Take 2 mL of each of the above-mentioned HEPES buffers with different pH values, add 10 μL of the probe stock solution to each set of buffers, and use 350 nm as the excitation wavelength to test the fluorescence intensity of the probe at 460 nm under different pH conditions. Then, add 50 μL of SDS solution to each solution, let it stand for 1 minute, and then use 350 nm as the excitation wavelength to test the fluorescence intensity of each solution at 460 nm after adding SDS solution.

[0040] The results are as follows Figure 2As shown, before the addition of SDS, the fluorescent probe did not emit obvious fluorescence in HEPES buffer with a pH of 1-12; after the addition of SDS solution, the fluorescent probe underwent obvious fluorescence enhancement in HEPES buffer with a pH of 1-11, and at pH 4 and 7, the fluorescence intensity of the fluorescent probe at 460 nm was the largest. Considering that HEPES buffer has a certain buffering capacity at pH 7, the subsequent examples were all tested in HEPES buffer with a pH of 7, and in actual applications, the test can be performed by mixing the buffer and the test solution.

[0041] Example 3 Changes in fluorescence intensity over time before and after the interaction of fluorescent probe with SDS

[0042] To 2 mL of HEPES buffer solution with a pH of 7.0, add 10 μL of the probe stock solution prepared in Example 2, use 350 nm as the excitation wavelength and 460 nm as the emission wavelength, and test using a fluorescence spectrometer for time scanning. Then, add 50 μL of SDS solution to make the final concentration of SDS 50 μM. Stir well and continue testing, and save the experimental test data of the change of fluorescence intensity over time in the above process.

[0043] The results are as follows Figure 3 As shown in the figure, after adding SDS to the HEPES buffer after adding the probe stock solution, the fluorescence intensity increases rapidly in the first 1 minute, and then the rate of increase gradually decreases until it stops increasing at about 18 minutes. Combined with the trend of fluorescence intensity changes, the fluorescence intensity of the probe reacting with SDS for 1 minute can be directly tested when applied.

[0044] Example 4 Fluorescence intensity changes after the fluorescent probe reacts with different concentrations of SDS

[0045] In 2 mL of HEPES buffer solution with a pH of 7.0, first add 10 μL of the probe stock solution prepared in Example 2, and then add 0, 2, 3, 4, 5, 7, 10, 15, 20, 30, 40, 50, 60, 65, 70, and 75 μL of the SDS solution prepared in Example 2, respectively. After stirring, let it stand for 1 minute, and the fluorescence emission spectrum of each solution was tested using a fluorescence spectrometer.

[0046] The results are as follows Figure 4 As shown in Figure 2, as the SDS concentration in the solution increases, the fluorescence intensity of the fluorescent probe at 460 nm in the solution continues to increase ( Figure 4 A), and when the SDS concentration is in the range of 5-60 μM, there is a good linear relationship between the fluorescence intensity of the fluorescent probe and the SDS concentration in the solution ( Figure 4 B), the linear equation is y = -244.1967 + 49.4701x, where R2 =0.99, y represents the fluorescence intensity, and x represents the concentration of SDS (μM). These data show that the fluorescent probe prepared by the present invention can produce a good linear response to SDS within a certain range and has high sensitivity.

[0047] Example 5 Selectivity of fluorescent probe for SDS

[0048] Preparation of interfering substance solution: Use ultrapure water as solvent to prepare different interfering substance solutions. The concentration of the interfering substance solution is 10mM. After preparation, all interfering substance solutions are stored at 4℃ for future use. The interfering substances include: SDBS, SDSO, CTAC, CTAB, DTAB, TW-20, MES, Betaine, TX-100, F - Br - , I - 、S2O3 2- 、NO3 - 、SO4 2- 、SO3 2- 、HPO4 2- , ClO - 、CO3 2- 、Cl - 、NO2 - 、CH3COO - , K + , Ca 2+ 、Zn 2+ 、Hg 2+ Cr 3+ Mg 2+ 、Fe 3+ 、Cu 2+ , Pb 2+ 、Mn 2 + 、Al 3+ 、Ag + .

[0049] To 2 mL of HEPES buffer solution with a pH of 7.0, 10 μL of the probe stock solution prepared in Example 2 was first added. One group of the mixed solution was added to the SDS solution. Different interfering substance solutions were added to the remaining groups of the mixed solution to achieve a final concentration of SDS of 20 μM and a final concentration of each of the other interfering substances of 100 μM. The solutions after adding SDS or the interfering substance were stirred evenly and allowed to stand for 1 minute. The fluorescence intensity of each solution at 460 nm was measured using a fluorescence spectrometer with an excitation wavelength of 350 nm.

[0050] The results are as follows Figure 5As shown in the figure, only after adding SDS, the fluorescence of the fluorescent probe in the solution is significantly enhanced. Except for a weak fluorescence response to high concentration of SDBS, the probe has no fluorescence response to other interferents. This shows that the fluorescent probe prepared by the present invention has a high selectivity for SDS and can specifically recognize SDS.

[0051] Example 6 Particle size changes before and after the reaction of fluorescent probe with SDS

[0052] The particle size distributions of 2 mL of an aqueous solution containing 10 μM fluorescent probe, 2 mL of an aqueous solution containing 50 μM SDS, and 2 mL of an aqueous solution containing both 10 μM fluorescent probe and 50 μM SDS were measured using a dynamic light scattering (DLS) instrument.

[0053] Depend on Figure 6 It can be seen that in the aqueous solution containing only the probe, the main particle size distribution is below 100 nm ( Figure 6 A), in the aqueous solution containing only SDS, the main particle size distribution is between 200nm-300nm ( Figure 6 B), while in the aqueous solution with both probe and SDS added, the final particle size distribution was around 1000 nm ( Figure 6 C). This indicates that the probe and SDS self-assembled into larger particle aggregates through electrostatic interaction.

[0054] Example 7 Application of fluorescent probe in testing anionic surfactant SDS in water samples

[0055] Tap water samples and Meihu water samples from Zhengzhou University were taken, filtered through a 0.22 μm filter membrane, and stored for later use. 1 mL of 20 mM HEPES buffer with a pH of 7.0 was mixed with 0.5 mL of the test filtrate and 0.5 mL of ultrapure water to prepare a test solution. 10 μL of the probe stock solution prepared in Example 2 was added to the test solution, mixed, and allowed to stand for 1 min. The fluorescence intensity of the solution at 460 nm was measured using a fluorescence spectrometer with an excitation wavelength of 350 nm. The SDS content in the water sample was calculated according to the standard curve equation in Example 4.

[0056] Different amounts of SDS (incremental concentrations of 20, 40, and 60 μM) were added to the test solutions, and then 10 μL of the probe stock solution prepared in Example 2 was added to each of the above solutions to perform spike recovery experiments with an excitation wavelength of 350 nm.

[0057] The results are shown in Table 1. The SDS content in tap water and Meihu water was not detected. The fluorescent probe prepared by the present invention has a good spiked recovery rate for SDS in actual water samples, indicating that the fluorescent probe designed by the present invention can be used for accurate and rapid detection of SDS in actual sample environments and can be promoted in future practical applications.

[0058] Table 1 SDS detection results in water samples and spike recovery test results

[0059]

[0060] Example 8 Application of Fluorescent Probe in Testing SDS Residue on the Surface of Washed Dishware

[0061] Take 2ml of commercial dishwashing liquid sample, dilute it with 2L of water, soak dishes in it for five minutes and wash them, then rinse them three times with water and dry them in an oven. After the sample has dried, add 10ml of 10.0mM HEPES buffer solution, pH 7.0, to a bowl and sonicate for five minutes to fully dissolve the remaining detergent in the buffer solution. Use this sample as the test solution, and using the linear equation in Example 4, test the SDS residue in the test solution and verify the effectiveness using the spike-in recovery method.

[0062] The specific method is as follows: take 2 mL of the above-mentioned test solution, add 0, 10, and 20 μL of the SDS solution prepared in Example 2 respectively, stir evenly, then add 10 μL of the probe stock solution, mix evenly, wait for 1 minute, and then use a fluorescence spectrometer to test the fluorescence intensity of each solution at 460 nm with an excitation wavelength of 350 nm.

[0063] As shown in Table 2, after using the dishwashing liquid to wash the tableware, no SDS residue is left on the surface of the tableware. At the same time, the average recovery rate of the spiked recovery of SDS clearly shows that the fluorescent probe can be used for the actual detection of detergent SDS in tableware, and has a good practical application prospect.

[0064] Table 2 Results of SDS residue detection on tableware surface and spike recovery test results

[0065] Concentration increment (μM) Detection amount (μM) Average recovery rate (%) 0 Not detected - 10 10.11 101.11 20 21.90 109.48

[0066] Example 9 Application of Fluorescent Probe in Testing the Anionic Surfactant SDS Concentration in Washing Products

[0067] Since there may be interference from other matrices with relatively high concentrations when testing actual detergents, the standard addition method is used to avoid unnecessary matrix interference when testing the concentration of anionic surfactants in washing products. The detergent is diluted to a low concentration with a HEPES buffer solution with a concentration of 10.00mM and a pH of 7.0 as the test solution for testing. In this experiment, the dishwashing liquid was diluted 6400 times with a HEPES buffer solution as the test solution. 2ml of the test solution was taken, and 0, 10, 20, 30, and 40μL of the SDS solution prepared in Example 2 were added respectively. Then, 10μL of the probe stock solution was added, mixed, and after waiting for 1 minute, the fluorescence intensity of each solution at 460nm was tested using a fluorescence spectrometer with an excitation wavelength of 350nm.

[0068] Table 3 shows that the linear relationship for this standard addition method is: y = 254.22 + 64.561x. This means that after the dishwashing liquid is diluted 6400-fold with HEPES buffer, the SDS concentration in the solution is 3.94 μM. This actual addition method demonstrates that the fluorescent probe can also be used to detect SDS concentration in detergents.

[0069] Table 3 Fluorescence intensity test results after adding different amounts of SDS to the test solution

[0070] Concentration increment (μM) 0 10 20 30 40 Fluorescence intensity (au) 262.7 913.5 1488 2231 2832

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Application of a fluorescent probe in detecting anionic surfactant SDS, characterized in that: The fluorescent probe structural formula is ; comprising the following steps: (1) Dissolving the fluorescent probe in DMSO to prepare a probe stock solution; (2) Add the probe stock solution to the HEPES buffer, then add different equivalents of SDS, mix well and let it stand. Use 350 nm as the excitation wavelength to measure the fluorescence emission spectra of each solution before and after adding SDS. (3) Observe the change in fluorescence intensity of the solution at 460 nm before and after the interaction of the fluorescent probe with SDS; (4) Add the probe stock solution and the sample solution to be tested to the HEPES buffer, mix well and let it stand. Use 350 nm as the excitation wavelength and measure the fluorescence intensity of the test solution at 460 nm. The SDS content in the sample solution to be tested is obtained based on the fluorescence intensity.

2. The use according to claim 1, characterized in that The concentration of the probe stock solution in step (1) is 2 mM.

3. The use according to claim 1, characterized in that In the steps (2) and (4), the pH of the HEPES buffer solution is 7.0, and the final concentration of HEPES is 10 mM.

4. The use according to claim 1, characterized in that The final concentration of the fluorescent probe in step (2) and step (4) is 10 μM.

5. The use according to any one of claims 1 to 4, characterized in that Used to detect SDS content in water.

6. The use according to any one of claims 1 to 4, characterized in that Used to detect SDS residues on tableware.

7. The use according to any one of claims 1 to 4, characterized in that The fluorescent probe can be used to detect the SDS concentration in washing products.

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