A method for detecting bismuth ions

Abstract

The application discloses a kind of ratio fluorescent probe based on Eu (III) coordination polymer, for detecting Bi (III) in water.GMP-Eu-DPA polymer containing Eu (III) and GMP and DPA coordination is synthesized with guanosine monophosphate (GMP), Eu (III) and 2,6-pyridine dicarboxylic acid (DPA) as raw material, the polymer emits red light at 614 nm under 282 nm wavelength excitation, which is the characteristic peak of Eu (III).When Bi (III) is added, Bi (III) takes GMP and DPA in GMP-Eu-DPA polymer, causes GMP-Eu-DPA polymer to dissociate, thereby reduces the luminescence intensity of GMP-Eu-DPA coordination polymer at 614 nm, and forms luminescent GMP-Bi complex at 373 nm, therefore, the luminescence intensity ratio I 373 / I 614 Can be used as the response signal of detecting Bi (III), constructs a kind of ratio fluorescent sensor for the analysis determination of Bi (III).The linear range of the system for detecting Bi (III) concentration is 1.0-230 μM, and the detection limit is 0.6 μM.The method is successfully used for detecting Bi (III) in real water sample, and the result of standard addition recovery experiment is satisfactory.

Description

TECHNICAL FIELD

[0001] The present application relates to a fluorescence method for detecting bismuth ions, and in particular to the construction of a GMP-Eu-DPA probe system and quantitative detection of bismuth ion concentration. BACKGROUND

[0002] Bismuth is a rare metal that has been used in various fields, including nuclear fuel carriers, computed tomography and organic synthesis, as well as alloys, cosmetics, dyes, medical applications and semiconductors. Bismuth compounds are widely used in the treatment of skin diseases, gastric inflammation caused by Helicobacter pylori and syphilis. Studies have found that bismuth ions (Bi(III)) do not pose a threat to human health, but excessive bismuth can accumulate in the brain and kidneys, which can cause neurotoxic effects. Bismuth can also cause a variety of diseases, such as kidney disease, neuropathological disease, osteoarthropathy and hepatitis. Therefore, developing an efficient and selective method for detecting bismuth ions is an important means to prevent bismuth from producing toxic side effects on the human body. So far, traditional analysis techniques such as atomic emission spectrometry, electrochemical methods, inductively coupled plasma atomic emission spectrometry, inductively coupled plasma mass spectrometry, and resonance light scattering have been used to detect Bi(III) ions. However, most of these methods are complex to operate, expensive in equipment and time-consuming in detection, and cannot meet the requirements of rapid detection.

[0003] In recent years, fluorescent probes for detecting various substances have attracted much attention due to their high sensitivity, low cost, time saving, and no need for sophisticated instruments. Lanthanide metal-organic frameworks (LMOFs) connected with bridging organic ligands have been successfully applied to a variety of sensing applications due to their large Stokes shift, long lifetime, high quantum yield, bright visible emission, and non-interfering emission energy. Trivalent lanthanide ions are usually weakly luminescent under direct excitation because f-f electronic transitions are forbidden. The antenna effect can make lanthanide ions in the organic framework emit strong light because the organic ligand absorbs photons, generates a triplet state from the singlet state, and energy transfer from the excited ligand to the lanthanide ion makes the characteristic emission of the lanthanide ion much stronger. In addition, most of the fluorescent probes based on lanthanide coordination polymers are based on the change of fluorescence intensity at a single wavelength as the output signal, while the single-wavelength emission signal will be affected by the fluctuation of excitation light intensity, the change of the amount of probe used, and the interference of the microenvironment. These unstable factors may cause systematic errors, inaccurate results, and non-reproducible results. Ratio fluorescent probes can record two emission signals at one excitation wavelength, and then calculate the intensity ratio of the two, which minimizes the ambiguity of the fluorescent signal through self-calibration, thereby improving the accuracy, anti-interference, and reproducibility of target detection. The use of the ratio of the intensity of the two wavelengths means that the results will be specific to the target analyte, and the influence of the biological molecular environment can be avoided. Therefore, it is still challenging to develop a fluorescent probe for the determination of Bi(III) with simplicity, high sensitivity, and high selectivity. SUMMARY

[0004] One of the purposes of the present application is to provide a method for detecting Bi(III). A GMP-Eu-DPA polymer containing Eu(III) coordinated with GMP and DPA was synthesized using guanosine monophosphate (GMP), Eu(III), and 2,6-pyridinedicarboxylic acid (DPA) as raw materials. When Bi(III) is added to the GMP-Eu-DPA probe system, it will combine with GMP in the system to form a GMP-Bi complex, which produces very strong fluorescence at 373 nm. At the same time, Bi(III) also reacts with DPA in the system to form a DPA-Bi complex, which causes the dissociation of the GMP-Eu-DPA polymer, thereby reducing the fluorescence peak at 614 nm. Therefore, the luminescence intensity ratio I 373 / I 614 The luminescence intensity ratio can be used as a response signal for detecting Bi(III), and a ratio fluorescent sensor is constructed for the analysis and determination of Bi(III). The linear range of the system for detecting the concentration of Bi(III) is 1.0-230 μM, and the detection limit is 0.6 μM.

[0005] The second object of the present application is to provide the application of the GMP-Eu-DPA probe in the detection of Bi(III).

[0006] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0007] The preparation method of the GMP-Eu-DPA coordination polymer fluorescent probe comprises the following steps:

[0008] The GMP disodium salt aqueous solution (10 mM) is added to the HEPES buffer solution (0.1 M, pH 7.8), and the Eu(NO3)3 solution (10 mM) is slowly added while stirring.

[0009] Then, the DPA (10 mM) aqueous solution is added to the above white precipitate, and stirring is performed at room temperature.

[0010] The above solution is centrifuged, the white precipitate is collected, and after washing and drying, it is dispersed in 10 mL of deionized water to obtain a GMP-Eu-DPA suspension.

[0011] In step (1), the volume of the Eu(NO3)3 aqueous solution and the GMP disodium salt solution is 4.0 mL, and the volume of the HEPES buffer solution is 1.0 mL.

[0012] In step (1), the stirring time is 0.5-1 h, preferably 1 h.

[0013] In step (2), the volume of DPA is 4.0 mL.

[0014] In step (2), the stirring time is 3 h.

[0015] In step (3), the centrifugation speed is 8000 rpm, and the centrifugation time is 7 min.

[0016] In step (3), the washing solution is deionized water.

[0017] The GMP-Eu-DPA coordination polymer prepared according to the above method is a spatial network structure composed of nanofiber aggregation and connection, and can emit red fluorescence. The fluorescence here can be quenched by Bi(III).

[0018] The present application also provides the application of the GMP-Eu-DPA in the detection of Bi(III), which can realize quantitative detection of Bi(III).

[0019] This invention also provides a method for detecting Bi(III), the method comprising the following steps: adding 50 μM GMP-Eu-DPA solution to HEPES buffer solution; adding different concentrations of Bi(III) ranging from 0-230.0 μM to different containers, and adding ultrapure water to make the final volume of each container 1.0 mL; reacting at room temperature for a period of time; and testing the fluorescence emission spectrum of the mixture with an excitation wavelength of 282 nm between 312-640 nm. The ratio of the emission intensities of the GMP-Eu-DPA system at 373 and 614 nm is used to determine the fluorescence emission spectrum. I 373 / I 614 A standard curve is plotted with the concentration of Bi(III) solution on the ordinate and the concentration of Bi(III) solution on the abscissa, thereby detecting the concentration of Bi(III) in the test solution.

[0020] The final concentration of the HEPES buffer solution was 200 μM, and the pH was 7.8.

[0021] The final concentrations of Bi(III) were 1, 5, 10, 20, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, and 230 μM, respectively.

[0022] The reaction was carried out under the condition of standing at room temperature for 5 minutes.

[0023] The linear equation of the standard curve is: I 373 / I 614 = 0.0089C - 0.01763, correlation coefficient R 2 It is 0.999. C The concentration of Bi(III) is expressed in μM.

[0024] The technical solution provided by this invention synthesizes a GMP-Eu-DPA lanthanide coordination polymer, which exhibits Eu at 614 nm under 282 nm wavelength excitation. 3+ The characteristic emission peak of Bi(III) is observed. When Bi(III) is added to the GMP-Eu-DPA probe system, it captures GMP and DPA, leading to the dissociation of the GMP-Eu-DPA polymer. This reduces the luminescence intensity of the GMP-Eu-DPA coordination polymer at 614 nm and forms a luminescent GMP-Bi complex at 373 nm. Based on this principle, this invention designs a novel ratiometric fluorescent probe to achieve the quantitative detection of Bi(III).

[0025] The ratio type fluorescent probe designed for detecting Bi (III) has good selectivity in the detection process and is not interfered by other related substances compared with single emission fluorescent probes. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Transmission electron microscopy of GMP-Eu-DPA prepared in Example 1;

[0027] Figure 2 Infrared spectra of GMP, DPA, GMP-Eu-DPA prepared in Example 1;

[0028] Figure 3 Mechanism diagram of GMP-Eu-DPA probe detecting Bi (III) in Example 2;

[0029] Figure 4 Fluorescence emission spectra of GMP, DPA, GMP-Eu, DPA+Bi (III) in Example 2.

[0030] Figure 5 Fluorescence emission spectra of Eu-DPA, Eu-DPA+Bi (III) in Example 2;

[0031] Figure 6 UV-visible absorption spectra of GMP, GMP+Bi (III), DPA, DPA+Bi (III) and Bi (III) in Example 2;

[0032] Figure 7 Fluorescence emission spectra of GMP-Eu-DPA, GMP-Eu-DPA+Bi (III) in Example 2;

[0033] Figure 8 Transmission electron microscopy of GMP-Eu-DPA after adding Bi (III) in Example 2;

[0034] Figure 9 Effect of pH on the luminescence intensity of GMP-Eu-DPA probe detecting Bi (III) system in Example 3, wherein the final concentration of Bi (III) is 100 μM;

[0035] Figure 10 Effect of reaction time on the luminescence intensity of GMP-Eu-DPA probe detecting Bi (III) system in Example 4, wherein the final concentration of Bi (III) is 100 μM;

[0036] Figure 11 Fluorescence intensity ratio in Example 5I 373 / I 614 fluorescence emission spectra with Bi(III) concentrations between 0 and 300 μM, wherein the final concentrations of Bi(III) were 0, 1, 5, 10, 20, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, 230, 250, 270, 300 μM, respectively;

[0037] Figure 12 standard curve for detecting Bi(III) by the GMP-Eu-DPA probe in Example 5, wherein the final concentrations of Bi(III) were 1, 5, 10, 20, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, 230 μM, respectively;

[0038] Figure 13 selectivity experiment graph for detecting Bi(III) by the GMP-Eu-DPA probe in Example 6, wherein the final concentration of Bi(III) was 100 μM, and the concentrations of other ions were 5-10 times of the final concentration of Bi(III). DETAILED DESCRIPTION

[0039] The application will be described in detail below with reference to the examples.

[0040] All the solutions in the application are aqueous solutions of the respective substances, unless otherwise specified. Example 1

[0041] The method for preparing the GMP-Eu-DPA coordination polymer comprises the following steps:

[0042] 4.0 mL of an aqueous Eu(NO3)3 solution (10 mM) was added to 4.0 mL of a HEPES buffer (100 mM; pH 7.8) in which GMP (10 mM) was dissolved. A white precipitate was immediately formed after adding the Eu(NO3)3 solution, and stirring was performed for 1 h. Then, 4.0 mL of an aqueous DPA solution (10 mM) was added. The mixed solution was placed at room temperature and stirred for 3 h. The solution was centrifuged at 8000 rpm for 7 min, and the white precipitate was collected and washed with ultrapure water three times to remove the unreacted reagents. The collected precipitate was dried and dispersed in 10 mL of ultrapure water to obtain a GMP-Eu-DPA suspension, which was stored at 4 ℃ for subsequent experiments.

[0043] The transmission electron microscopy (TEM) image thereof is shown in Figure 1 As can be seen from the TEM image, the prepared GMP-Eu-DPA is a nanoscale fiber network structure.

[0044] Fourier transform infrared spectroscopy confirmed the formation of the GMP-Eu-DPA polymer. The infrared spectra of GMP, DPA, and the GMP-Eu-DPA polymer are shown below. Figure 2 As shown. GMP spectra at 1697, 1482, and 1086 cm⁻¹ -1 The locations represent the n(P-OH) stretching vibration, n(N7-C8) stretching vibration, and symmetric n... s Absorption bands of (PO3) stretching vibrations. In the GMP-Eu-DPA spectrum, these peaks shift to 1706, 1458, and 1091 cm⁻¹, respectively. -1 This indicates a synergistic effect between GMP and Eu(III). The DPA spectrum shows 1573 and 1413 cm⁻¹... -1 The peaks representing the bond lengths correspond to the C=N and C=C double bonds on the pyridine ring in DPA. These peaks shift to 1600 and 1428 cm⁻¹, respectively, in the GMP-Eu-DPA spectrum. -1 This indicates that DPA and Eu(III) have a synergistic effect. These results provide direct evidence for the synergistic effect of Eu(III) with GMP and DPA.

[0045] These results indicate that both GMP and DPA are involved in the formation of the GMP-Eu-DPA coordination polymer network structure. Example 2

[0046] Mechanism of Bi(III) detection by the GMP-Eu-DPA probe prepared in Example 1

[0047] like Figure 3 As shown, the GMP-Eu-DPA polymer emits red light at 614 nm under 282 nm excitation, which is the characteristic peak of Eu(III). Upon the addition of Bi(III), Bi(III) abstracts GMP or DPA from the GMP-Eu-DPA polymer, leading to polymer dissociation, reducing the luminescence intensity of the GMP-Eu-DPA coordination polymer at 614 nm, and forming a luminescent GMP-Bi complex at 373 nm. The emission spectra of GMP and DPA in the presence and absence of Bi(III) were measured to study the interactions between Bi(III) and GMP, and between Bi(III) and DPA. Figure 4As shown, mixtures of GMP, DPA, DPA, and Bi(III), as well as mixtures of GMP and Eu(III), did not emit light. In the presence of Bi(III), GMP exhibited strong fluorescence emission at 373 nm. The increase in GMP luminescence intensity was entirely attributed to the formation of the GMP-Bi complex. Bi(III) coordinated with the oxygen atom in GMP to form a complex, blocking the electron-withdrawing ability of the oxygen atom in the GMP molecule, thus enabling GMP to emit light at 373 nm. Figure 5 As shown, the luminescence of the Eu-DPA complex is quenched by Bi(III). This is because DPA is captured by Bi(III) in the system, leading to the disruption of the Eu-DPA structure and thus quenching the fluorescence emission at 614 nm. The UV-Vis absorption spectrum is shown below. Figure 6 As shown, the addition of Bi(III) altered the UV-vis absorption of GMP and DPA, indicating that Bi(III) interacts with both DPA and GMP. Figure 7 As can be seen, the GMP-Eu-DPA polymer exhibits strong luminescence at 614 nm in the absence of Bi(III). This is attributed to the energy absorbed by DPA and transferred to Eu(III) (i.e., the antenna effect). However, the addition of Bi(III) quenches the luminescence of the GMP-Eu-DPA polymer, resulting in a new emission band centered at 373 nm at the same excitation wavelength (282 nm). The addition of Bi(III) disrupts the structure of the GMP-Eu-DPA polymer. By mixing an appropriate amount of Bi(III) with the GMP-Eu-DPA polymer, the structure of the GMP-Eu-DPA polymer was studied using transmission electron microscopy, as shown below. Figure 8 As shown, the GMP-Eu-DPA polymer network structure is disrupted by the addition of Bi(III). Example 3

[0048] Effect of pH of HEPES buffer solution on the detection system

[0049] HEPES buffer solutions with different pH values ​​were added to the GMP-Eu-DPA probe, and then Bi(III) of the same concentration was added to each solution. The mixtures were thoroughly mixed and brought to a final volume of 1.0 mL, and allowed to react at room temperature for 5 min. The fluorescence emission spectra of each system were measured at an excitation wavelength of 282 nm. The difference in fluorescence intensity ratio, Δ, was calculated by plotting the pH of the HEPES buffer solution on the x-axis. I 373 / I 614 Plot a graph on the ordinate, such as Figure 9 , ∆ I 373 / I614 = (Δ I 373 / I 614 ) - (Δ I 373 / I 614 )0, wherein (Δ I 373 / I 614 ) and (Δ I 373 / I 614 )0are the fluorescence intensity ratios of GMP-Eu-DPA system with and without Bi(III) respectively at the same pH. The final concentration of HEPES buffer solution is 200 μM, and the final concentration of Bi(III) is 100 μM. The pH of the system is 6.8, 7.0, 7.2, 7.4, 7.6, 7.8, 8.0, 8.2 respectively.

[0050] It can be seen from Figure 9 that the pH of the HEPES buffer solution used in the detection system will affect the sensitivity of the ratiometric fluorescent probe. When the pH of the buffer solution is 7.8, the difference Δ I 373 / I 614 is the largest. Therefore, when detecting Bi(III), the HEPES buffer solution with pH 7.8 is selected as the optimal reaction pH value. Example 4

[0051] Effect of reaction time on the detection system

[0052] The HEPES buffer solution and GMP-Eu-DPA suspension were mixed, and then the same concentration of Bi(III) was added to the system and mixed thoroughly to 1.0 mL. The emission spectrum was detected every few minutes under the excitation wavelength of 282 nm, and the reaction time was taken as the abscissa, I 373 / I 614 and the ordinate was taken as the fluorescence intensity ratio, as shown in Figure 10 .The final concentration of HEPES buffer solution in the detection system is 200 μM, and the final concentration of Bi(III) is 100 μM.

[0053] It can be seen from Figure 10 that the fluorescence intensity ratio I 373 / I 614The fluorescence intensity gradually increased with the increase of the reaction time, and gradually tended to be stable when the reaction time reached 3 min. In order to make the reaction more complete, the optimal reaction time was selected as 5 min. Example 5

[0054] Quantitative detection of Bi(III)

[0055] The method for quantitative detection of Bi(III) includes the following steps: 50 μM GMP-Eu-DPA solution is added to 20 μL HEPES buffer solution (0.01 M, pH 7.8), then different volumes of Bi(III) are added to the mixture, so that the final concentration of Bi(III) is in the range of 0-300 μM, deionized water is added to 1.0 mL, and it is placed at room temperature for 5 min. The emission spectrum in the wavelength range of 312-640 nm is measured under the excitation wavelength of 282 nm. The ratio of the fluorescence intensity I 373 / I 614 The concentration of Bi(III) solution is taken as the ordinate, and the concentration of Bi(III) is taken as the abscissa. The final concentration of Bi(III) is 0, 1, 5, 10, 20, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, 230, 250, 270, 300 μM, respectively.

[0056] As can be seen from Figure 11 , with the increase of the concentration of Bi(III), the fluorescence of GMP-Eu-DPA probe system at 373 nm gradually increases, and the fluorescence at 614 nm gradually decreases.

[0057] As can be seen from Figure 12 , the ratio of the fluorescence intensity I 373 / I 614 of Bi(III) shows a good linear relationship, and the linear equation is I 373 / I 614 = 0.0089C - 0.01763, the correlation coefficient R 2 is 0.999, wherein C is the concentration of Bi(III) in μM. The linear concentration range of Bi(III) in this method is 1-230 μM. The detection limit of Bi(III) is 0.6 μM calculated by the formula 3σ / k (wherein σ is the standard deviation of 9 blank measurements, and k is the slope of the standard curve). Example 6

[0058] Selective experiment

[0059] A high-performance fluorescent probe must possess good selectivity and interference resistance. To evaluate the performance of the fluorescent probe in complex detection environments, various potential interfering substances were selected for testing, including Ag. + Al 3+ Ca 2 + Cd 2+ Co 2+ Cu 2+ Fe 3+ Mg 2+ Na + Ni 2+ Pb 2+ and Zn 2+ The final concentration of the Bi(III) line was 100 μM, and the final concentration of the interfering substances was 5-10 times that of the final concentration of the Bi(III) line. Under the same experimental conditions, the Bi(III) line and other ions reacted with the GMP-Eu-DPA probe system at room temperature for 5 min, and the fluorescence intensity was measured at an excitation wavelength of 282 nm. I 373 / I 614 .

[0060] like Figure 13 Experimental results show that, except for the Bi(III) line which can increase the fluorescence intensity compared to I 373 / I 614 Aside from a significant increase in ion concentration, the influence of other ions on this probe is almost negligible. Therefore, the ratiometric fluorescent probe designed in this invention is considered to have good selectivity and anti-interference capabilities. Example 7

[0061] Determination of Bi(III) lines in actual samples

[0062] To verify the practicality of the detection method provided by this invention, the concentration of Bi(III) in tap water was detected by the standard addition method, and the results are listed in Table 1.

[0063] No Bi(III) lines were detected in tap water. In this invention, two different concentrations of Bi(III) were added for recovery experiments, and the recovery rate of this method was found to be between 99.5% and 100.13%, with the average relative standard deviation (RSD) controlled within 1.59%. These data indicate that the method is practical and reliable.

[0064] Table 1. Analytical results of Bi(III) in actual water samples

[0065] Sample No. Amount added (μM) Detection (μM) (n = 4) Recovery (%) (n = 4) RSD (%) (n = 4) 1 0 Not detected — — 2 70 70.09 100.13 1.59 3 150 149.21 99.5 0.989

[0066] The above-mentioned detection method of Bi(III) and application are described in detail in the reference examples, which are illustrative rather than limiting. Several examples can be listed within the defined range, and thus the changes and modifications without departing from the overall concept of the present application shall fall within the scope of the present application.

Claims

1. A method for preparing a GMP-Eu-DPA fluorescent probe, characterized in that, The method comprises the following steps: (1) 4.0 mL of 10 mM GMP disodium salt aqueous solution is added to 1.0 mL of 0.1 M HEPES buffer solution with pH of 7.8, and 4.0 mL of 10 mM Eu(NO3)3 solution is slowly added while stirring, and a white precipitate is immediately formed, and the mixed solution is stirred at room temperature, (2) Then 4.0 mL of 10 mM DPA aqueous solution is added to the white precipitate, and stirring is performed at room temperature, (3) The above solution is centrifuged, the white precipitate is collected, and after washing and drying, the GMP-Eu-DPA suspension is obtained by dispersing in 10 mL of deionized water.

2. Application of the GMP-Eu-DPA fluorescent probe prepared by the preparation method of claim 1 in detection of Bi(III).

3. A method for the detection of Bi(III), characterized in that The detection method comprises the following steps: mixing 50 μL of the GMP-Eu-DPA fluorescent probe of claim 1 with a HEPES buffer solution, adding Bi(III) of different concentrations into the mixture, adding deionized water to make up to 1.0 mL, reacting for a period of time, and testing the fluorescence emission spectrum in the wavelength range of 312-640 nm under an excitation wavelength of 282 nm, so as to obtain the ratio I 373 / I 614 The ratio I 373 nm / 614 nm is taken as the ordinate, and the concentration of Bi(III) is taken as the abscissa to draw a standard curve, and then the concentration of Bi(III) in the sample to be detected is detected.

4. The detection method according to claim 3, characterized in that, In the detection system, the final concentration of the HEPES buffer solution is 200 μM, the pH is 7.8, the reaction time is 5 min at room temperature, and the final concentration of Bi(III) is 1, 5, 10, 20, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, and 230 μM, respectively.

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