Method for detecting bismuth ions

Abstract

The invention discloses a ratiometric fluorescent probe based on an Eu (III) coordination polymer. The ratiometric fluorescent probe is used for detecting Bi (III) in water. GMP (guanosine monophosphate), Eu (III) and 2, 6-dipicolinic acid (DPA) are used as raw materials, a GMP-Eu-DPA polymer containing coordination of Eu (III), GMP and DPA is synthesized, the polymer emits red light at 614 nm under excitation of the wavelength of 282 nm, and the red light is a characteristic peak of Eu (III). When Bi (III) is added, the Bi (III) captures GMP and DPA in the GMP-Eu-DPA polymer to cause dissociation of the GMP-Eu-DPA polymer, so that the luminous intensity of the GMP-Eu-DPA coordination polymer at 614 nm is reduced, and a luminous GMP-Bi compound is formed at 373 nm, therefore, the luminous intensity ratio I373 / I614 can be used as a response signal for detecting Bi (III), and a ratio fluorescence sensor is constructed for analysis and determination of Bi (III). The linear range of Bi (III) concentration detected by the system is 1.0-230 [mu] M, and the detection limit is 0.6 [mu] M. The method is successfully used for detecting Bi (III) in a real water sample, and standard recovery experiment results are satisfactory.

Description

Technical Field

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

[0002] Bismuth is a rare metal that has been used in a variety of 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 to treat skin diseases, gastritis 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 accumulates in the brain and kidneys, causing neurotoxic effects. Bismuth may also cause a variety of diseases, such as nephropathy, neuropathological diseases, osteoarthritis and hepatitis. Therefore, developing an efficient and selective method for detecting bismuth ions is an important means to prevent bismuth from causing toxic side effects on the human body. To date, traditional analytical techniques such as atomic emission spectroscopy, electrochemical methods, inductively coupled plasma atomic emission spectroscopy, inductively coupled plasma mass spectrometry, and resonance light scattering are generally used to detect Bi(III) ions. However, most of these methods are complicated to operate, expensive in instruments and take a long time to detect, which cannot meet the requirements of rapid detection.

[0003] In recent years, fluorescent probes for detecting various substances have attracted much attention due to their advantages such as high sensitivity, low price, time saving, and no need for precision instruments. Lanthanide metals and organic frameworks connected with lanthanide ions and bridging organic ligands have been successfully used in various sensing applications due to their large Stokes shift, long lifetime, high quantum yield, brighter visible emission, and undisturbed emission energy. Trivalent lanthanide ions are usually weakly luminescent under direct excitation due to the prohibition of ff electronic transitions. The antenna effect can make lanthanide ions in organic frameworks emit strong light, because organic ligands absorb photons, generate triplet excitation from singlet states, and energy transfer from excited ligands to lanthanide ions makes the characteristic emission of lanthanide ions more intense. In addition, fluorescent probes based on lanthanide coordination polymers mostly use the change of fluorescence intensity at a single wavelength as the output signal, and the single-wavelength emission signal is affected by the fluctuation of the 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 irreproducible results. Ratiometric fluorescent probes can record two emission signals at one excitation wavelength and then calculate the intensity ratio of the two, minimizing the ambiguity of the fluorescent signal through self-calibration, thereby improving the accuracy, anti-interference and repeatability of target detection. Using the ratio of the signal intensity of the two wavelengths means that the results will be specific to the target analyte and can avoid the influence of the biological molecular environment. Therefore, it remains challenging to develop a fluorescent probe with simplicity, high sensitivity and high selectivity for the determination of Bi(III). Summary of the invention

[0004] One of the purposes of the present invention is to provide a method for detecting Bi(III). Using guanosine monophosphate (GMP), Eu(III) and 2,6-pyridinedicarboxylic acid (DPA) as raw materials, a GMP-Eu-DPA polymer containing Eu(III) coordinated with GMP and DPA was synthesized. When Bi(III) is added to the GMP-Eu-DPA probe system, it will combine with the GMP in the system to form a GMP-Bi complex, which produces strong fluorescence at 373 nm. At the same time, Bi(III) also reacts with the DPA in the system to form a DPA-Bi complex, causing the GMP-Eu-DPA polymer to dissociate, thereby reducing the fluorescence peak at 614 nm. Therefore, the luminescence intensity is higher than that of the probe. I 373 / I 614 It can be used as a response signal to detect Bi(III), and a ratiometric fluorescence sensor was constructed for the analysis and 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.

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

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: The preparation method of the GMP-Eu-DPA coordination polymer fluorescent probe comprises the following steps: GMP disodium salt aqueous solution (10 mM) was added to HEPES buffer solution (0.1 M, pH 7.8), and Eu(NO3)3 solution (10 mM) was slowly added while stirring, and a white precipitate was immediately formed in the solution.

[0007] Then, DPA (10 mM) aqueous solution was added to the white precipitate and stirred at room temperature.

[0008] The above solution was centrifuged, and the white precipitate was collected, washed, dried, and dispersed in 10 mL of deionized water to obtain a GMP-Eu-DPA suspension.

[0009] In step (1), the volumes of the Eu(NO3)3 aqueous solution and the GMP disodium salt solution were both 4.0 mL, and the volume of the HEPES buffer solution was both 1.0 mL.

[0010] In step (1), the stirring time is 0.5 to 1 h, preferably 1 h.

[0011] In step (2), the volume of DPA was 4.0 mL.

[0012] In step (2), the stirring time is 3 h.

[0013] In step (3), the centrifugal speed is 8000 rpm and the centrifugal time is 7 min.

[0014] In step (3), the washing solution is deionized water.

[0015] The GMP-Eu-DPA coordination polymer prepared according to the above method has a spatial network structure composed of nanofiber aggregation and connection, and can emit red fluorescence, and the fluorescence here can be quenched by Bi(III).

[0016] The present invention also provides the use of the GMP-Eu-DPA in detecting Bi(III), which can realize the quantitative detection of Bi(III).

[0017] The present invention also provides a method for detecting Bi(III), which comprises the following steps: adding 50 μL of GMP-Eu-DPA solution to a HEPES buffer solution. Adding different concentrations of Bi(III) of 0-230.0 μM to different containers, and adding ultrapure water to make the final volume of each container 1.0 mL, reacting for a while at room temperature, and testing the fluorescence emission spectrum of the mixture between 312-640 nm with an excitation wavelength of 282 nm. The ratio of the emission intensity of the GMP-Eu-DPA system at 373 and 614 nm ( I 373 / I 614 ) as the ordinate and the concentration of Bi(III) solution as the abscissa to draw a standard curve, and then detect the Bi(III) concentration in the test solution.

[0018] The final concentration of the HEPES buffer solution was 200 μM, and the pH was 7.8.

[0019] 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.

[0020] The reaction was carried out at room temperature for 5 min.

[0021] The linear equation of the standard curve is: I 373 / I 614 = 0.0089C - 0.01763, correlation coefficient R 2 is 0.999, C is the concentration of Bi(III) in μM.

[0022] In the technical solution provided by the present invention, a GMP-Eu-DPA lanthanide coordination polymer is synthesized, and the coordination polymer exhibits Eu at 614 nm under 282 nm wavelength excitation. 3+ When Bi(III) is added to the GMP-Eu-DPA probe system, it captures GMP and DPA, causing the GMP-Eu-DPA polymer to dissociate, reducing the luminescence intensity of the GMP-Eu-DPA coordination polymer at 614 nm, and forming a luminescent GMP-Bi complex at 373 nm. Based on the above principle, the present invention designs a new ratiometric fluorescent probe to achieve quantitative detection of Bi(III).

[0023] Compared with the single-emission fluorescent probe, the ratiometric fluorescent probe designed for detecting Bi(III) in the present invention has good selectivity during the detection process and is not interfered by other related substances. The method can be used to detect the content of Bi(III) in tap water, with good detection sensitivity and selectivity, and the detection limit can be as low as 0.6 μM. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a transmission electron microscopy image of GMP-Eu-DPA prepared in Example 1; Figure 2 The infrared spectra of GMP, DPA and GMP-Eu-DPA prepared in Example 1; Figure 3 This is a diagram showing the mechanism of the GMP-Eu-DPA probe detecting Bi(III) in Example 2; Figure 4 These are the fluorescence emission spectra of GMP, DPA, GMP-Eu, and DPA+Bi(III) in Example 2.

[0025] Figure 5 The fluorescence emission spectra of Eu-DPA and Eu-DPA+Bi(III) in Example 2; Figure 6 The UV-visible absorption spectra of GMP, GMP+Bi(III), DPA, DPA+Bi(III) and Bi(III) in Example 2; Figure 7 The fluorescence emission spectra of GMP-Eu-DPA and GMP-Eu-DPA+Bi(III) in Example 2; Figure 8 This is a transmission electron microscopy image of GMP-Eu-DPA after adding Bi(III) in Example 2; Fig. 9 The effect of pH on the luminescence intensity of the Bi(III) system detected by the GMP-Eu-DPA probe in Example 3, wherein the final concentration of Bi(III) is 100 μM; Fig.10 The effect of reaction time on the luminescence intensity of the Bi(III) system detected by the GMP-Eu-DPA probe in Example 4, wherein the final concentration of Bi(III) is 100 μM; Fig.11 The fluorescence intensity ratio in Example 5 I 373 / I 614Fluorescence emission spectra with Bi(III) concentrations between 0 and 300 μM, where 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, and 300 μM; Fig.12 is the standard curve for detecting Bi(III) by the GMP-Eu-DPA probe in Example 5, wherein the final concentrations of Bi(III) are 1, 5, 10, 20, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, and 230 μM, respectively; Fig.13 This is a selectivity experimental diagram of the GMP-Eu-DPA probe for detecting Bi(III) in Example 6, wherein the final concentration of Bi(III) is 100 μM and the concentrations of other ions are 5-10 times the final concentration of Bi(III). DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the embodiments.

[0027] All solutions in the present invention are aqueous solutions of various substances unless otherwise specified. Example

[0028] The preparation method of the GMP-Eu-DPA coordination polymer comprises the following steps: 4.0 mL of Eu(NO3)3 aqueous solution (10 mM) was added to 4.0 mL of HEPES buffer (100 mM; pH 7.8) containing GMP (10 mM). A white precipitate was formed immediately after the addition of Eu(NO3)3 solution, and the mixture was stirred for 1 h. Then 4.0 mL of DPA (10 mM) aqueous solution was added. The mixed solution was stirred at room temperature for 3 h, and the solution was centrifuged at 8000 rpm for 7 min. The white precipitate was collected and washed three times with ultrapure water to remove the unreacted reagent. 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 °C for subsequent experiments.

[0029] Its transmission electron microscopy image is as follows Figure 1 As shown, the transmission electron microscopy (TEM) images show that the prepared GMP-Eu-DPA is a nanoscale fiber network structure.

[0030] Fourier transform infrared spectroscopy confirmed the formation of GMP-Eu-DPA polymer. The infrared spectra of GMP, DPA and GMP-Eu-DPA polymer are shown in Figure 2. Figure 2The GMP spectrum is shown at 1697, 1482 and 1086 cm -1 The positions are n (P-OH) stretching vibration, n (N7-C8) stretching vibration and symmetric n s In the GMP-Eu-DPA spectrum, these peaks shift to 1706, 1458, and 1091 cm -1 , indicating that GMP and Eu(III) have a coordinated effect. The 1573 and 1413 cm -1 The peaks of the bond lengths are 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 , indicating that DPA and Eu(III) had a coordinated effect. These results provide direct evidence for the synergistic effect of Eu(III) with GMP and DPA.

[0031] Based on these results, it is shown that both GMP and DPA are involved in the formation of the GMP-Eu-DPA coordination polymer network structure. Example

[0032] Mechanism of detecting Bi(III) by the GMP-Eu-DPA probe prepared in Example 1 like Figure 3 As shown, the GMP-Eu-DPA polymer emits red light at 614 nm under excitation at a wavelength of 282 nm, which is the characteristic peak of Eu(III). After Bi(III) is added, Bi(III) captures GMP or DPA in the GMP-Eu-DPA polymer, causing the GMP-Eu-DPA polymer to dissociate, 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 luminescence 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 4 As shown, GMP, DPA, a mixture of DPA and Bi(III), and a mixture of GMP and Eu(III) did not emit light. In the presence of Bi(III), GMP has a strong fluorescence emission at 373 nm. The increase in the luminescence intensity of GMP is entirely attributed to the formation of the GMP-Bi complex. Bi(III) coordinates with the oxygen atoms in GMP to form a complex, blocking the electron-withdrawing ability of the oxygen atoms in the GMP molecule, thereby causing GMP to emit light at 373 nm. Figure 5As 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, resulting in the destruction of the structure of Eu-DPA, and the fluorescence emission at 614 nm is quenched. The ultraviolet-visible absorption spectrum, as Figure 6 shown, the addition of Bi(III) changes the UV-vis absorption of GMP and DPA, indicating that Bi(III) interacts with DPA and GMP. As can be seen from Figure 7 , in the absence of Bi(III), the GMP-Eu-DPA polymer has strong luminescence at 614 nm. This is attributed to the absorption of ultraviolet light energy by DPA and transferred to Eu(III) (i.e., the antenna effect). After adding Bi(III), the luminescence of the GMP-Eu-DPA polymer is quenched, and a new emission band centered at 373 nm appears at the same excitation wavelength (282 nm). The addition of Bi(III) will destroy 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 by transmission electron microscopy, as Figure 8 shown, the network structure of the GMP-Eu-DPA polymer is destroyed by the added Bi(III). Example

[0033] Effect of pH of HEPES buffer solution on the detection system Add HEPES buffer solutions with different pH values to the GMP-Eu-DPA probe, then add the same concentration of Bi(III) to a series of solutions, mix well and make up the volume to 1.0 mL, and react at room temperature for 5 min. Measure the fluorescence emission spectra of each system at an excitation wavelength of 282 nm, with the pH of the HEPES buffer solution as the abscissa and the difference in fluorescence intensity ratio ∆ I 373 / I 614 as the ordinate to plot a graph, as Fig. 9 , ∆ I 373 / I 614 = (∆ I 373 / I 614 ) - (∆ I 373 / I 614 ), where (∆ I 373 / I 614 ) and (∆ I373 / I 614 )0 are the fluorescence intensity ratios of the GMP-Eu-DPA system with and without Bi(III) at the same pH. The final concentration of HEPES buffer solution was 200 μM, and the final concentration of Bi(III) was 100 μM. The pH values ​​in the system were 6.8, 7.0, 7.2, 7.4, 7.6, 7.8, 8.0, and 8.2, respectively.

[0034] from Fig. 9 As can be seen from the figure, the pH of the HEPES buffer solution used in the detection system affects the sensitivity of the ratio fluorescence probe. When the pH of the buffer solution is 7.8, the difference in the fluorescence intensity ratio ∆ I 373 / I 614 Therefore, when detecting Bi(III), HEPES buffer solution with a pH of 7.8 was selected as the optimal reaction pH value. Example

[0035] Effect of reaction time on detection system Mix the HEPES buffer solution and the GMP-Eu-DPA suspension, add Bi(III) of the same concentration to the system, mix thoroughly and adjust the volume to 1.0 mL. Detect the emission spectrum every few minutes at an excitation wavelength of 282 nm, with the reaction time as the horizontal axis. I 373 / I 614 Plot the ordinate, such as Fig.10 The final concentration of HEPES buffer solution in the detection system was 200 μM, and the final concentration of Bi(III) was 100 μM.

[0036] Depend on Fig.10 It can be seen that the fluorescence intensity ratio I 373 / I 614 It increases with the increase of reaction time and gradually stabilizes when the reaction time reaches 3 min. In order to make the reaction more thorough, the optimal reaction time is 5 min. Example

[0037] Quantitative detection of Bi(III) The quantitative detection method of Bi(III) comprises the following steps: adding 50 μM GMP-Eu-DPA solution to 20 μL HEPES buffer solution (0.01 M, pH 7.8), then adding different volumes of Bi(III) to the mixture to make the final concentration of Bi(III) in the range of 0-300 μM, adding deionized water to 1.0 mL, and leaving it at room temperature for 5 minutes. The emission spectrum in the wavelength range of 312-640 nm is measured at an excitation wavelength of 282 nm. The ratio of fluorescence intensity is used as the ratio of the fluorescence intensity. I 373 / I 614 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, and 300 μM.

[0038] from Fig.11 It can be seen that with the increase of Bi(III) concentration, the fluorescence of the GMP-Eu-DPA probe system at 373 nm gradually increased, while the fluorescence at 614 nm gradually decreased.

[0039] from Fig.12 It can be seen that the ratio of fluorescence intensity I 373 / I 614 It shows a good linear relationship with the concentration of Bi(III), and the linear equation is: I 373 / I 614 = 0.0089C - 0.01763, correlation coefficient R 2 is 0.999, where 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 using the formula 3σ / k (where σ is the standard deviation of 9 blank measurements and k is the slope of the standard curve). Example

[0040] Selective experiment A fluorescent probe with good performance must have good selectivity and anti-interference ability. In order to evaluate the performance of fluorescent probes in complex detection environments, a variety of potential interferents were selected for testing, including Ag + 、Al 3+ , Ca 2 + 、Cd2+ 、Co 2+ , Cu 2+ , Fe 3+ Mg 2+ 、Na + 、Ni 2+ , Pb 2+ and Zn 2+ The final concentration of Bi(III) line was 100 μM, and the final concentration of the interfering substance was 5-10 times of the final concentration of Bi(III) line. Under the same experimental conditions, 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 to calculate I 373 / I 614 .

[0041] like Fig.13 The experimental results show that, in addition to the Bi(III) line, the fluorescence intensity can be increased by I 373 / I 614 Except for the obvious increase, the influence of other ions on this probe is almost negligible. Therefore, it is believed that the ratiometric fluorescent probe designed in the present invention has good selectivity and anti-interference ability. Example

[0042] Determination of Bi(III) lines in real samples In order to verify the practicability of the detection method provided by the present invention, the present invention detected the concentration of Bi(III) line in tap water by standard addition method, and the results are listed in Table 1.

[0043] In tap water, no Bi(III) line was detected. The present invention added two different concentrations of Bi(III) for recovery experiments, and found that the recovery rate of this method was between 99.5-100.13%, and the average relative standard deviation (RSD) was controlled within 1.59%. These data show that this method is practical and reliable.

[0044] Table 1 Analysis results of Bi(III) in actual water samples Sample No. Addition amount (μM) Detection (μM) (n = 4) Recovery rate (%) (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 The above reference embodiments provide a detailed description of the detection method and application of Bi(III), which is illustrative rather than restrictive. Several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a GMP-Eu-DPA fluorescent probe, characterized in that: The following steps are involved: (1) Add 4.0 mL of GMP disodium salt aqueous solution (10 mM) to 1.0 mL of HEPES buffer solution (0.1 M, pH 7.8), and slowly add 4.0 mL of Eu(NO3)3 solution (10 mM) while stirring. A white precipitate will form immediately, and the mixed solution will be stirred at room temperature. (2) Then, DPA (10 mM) aqueous solution was added to the above white precipitate and stirred at room temperature. (3) The above solution was centrifuged, the white precipitate was collected, washed, dried and dispersed in 10 mL of deionized water to obtain a GMP-Eu-DPA suspension.

2. Use of the GMP-Eu-DPA fluorescent probe according to claim 1 in detecting Bi(III).

3. A method for detecting Bi(III), characterized in that: The detection method comprises the following steps: 50 μL of GMP-Eu-DPA solution and HEPES buffer solution are mixed, and then different concentrations of Bi(III) are added thereto, and finally deionized water is added to make the volume 1.0 mL. After a period of reaction, the fluorescence emission spectrum in the wavelength range of 312-640 nm under the excitation wavelength of 282 nm is tested, and the ratio of the fluorescence intensity at the wavelengths of 373 nm and 614 nm is used as the value I 373 / I 614 A standard curve is drawn with the concentration of Bi(III) as the ordinate and the concentration of Bi(III) as the abscissa, thereby detecting the concentration of Bi(III) in the sample to be tested.

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

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