Direct mass spectrometry device and method for trace uranium in water body

Abstract

The invention discloses a direct mass spectrometry device and method for trace uranium in a water body, and relates to the technical field of analys.The method comprises the steps that a gel film is soaked in uranium-containing wastewater and taken out, a tip is cut out, and the uranium-adsorbed gel film is obtained; dropwise adding an extracting agent on the gel film, and then applying high voltage on the gel film, so that uranium adsorbed on the gel film is extracted and moves towards the tip along with the solvent to form spray; uranium is ionized in the form of uranyl acetate and detected by a mass spectrum detection system; according to the invention, accurate analysis of trace uranium can be realized, and mass loss of uranium in a water sample due to links such as sample treatment and preservation is avoided. The device can be applied to various complex water environments, and direct mass spectrometry can be realized only by shearing gel into a triangular shape with a tip and applying voltage and an extracting agent during analysis. And the method has the advantages of high analysis speed, good linear relationship, low detection limit and the like.

Description

Technical Field

[0001] This invention relates to the field of analytical technology, specifically to a direct mass spectrometry analysis device and method for trace uranium in water. Background Technology

[0002] In recent years, nuclear energy development has occupied an increasingly important position in my country's energy structure, becoming one of the main energy sources and playing a key supporting role in economic development and social construction. However, the development and utilization of nuclear energy often results in the leakage of some radioactive elements into the environment, causing environmental pollution and even human health problems. China's latest "Standards for Drinking Water Quality" stipulates a limit of 0.03 mg / L for uranium. Long-term exposure to an environment with excessive uranium levels poses a significant risk to human health. Therefore, it is urgent to conduct analysis and detection of radioactive substances in environmental water samples, especially trace amounts of the radioactive element uranium in water bodies. This is of great significance for effectively controlling environmental pollution and reducing ecological risks. Although classical spectrophotometry can quantitatively detect the uranium content in water by measuring the absorbance of the analyte within a specific wavelength or wavelength range, this method has significant drawbacks. It cannot analyze trace amounts of uranium in water, is highly susceptible to interference from other elements, and requires complex enrichment and chemical separation operations before measurement. These procedures are not only cumbersome and time-consuming but also fail to meet the practical needs of rapid detection. Furthermore, analyzing uranium in water using traditional methods (such as ICP-MS) often requires on-site collection, filtration, and preservation of water samples. This places stringent requirements on the preservation conditions (such as light exposure, container material, preservation medium, and preservation time). Each step can potentially lead to the loss of trace amounts of uranium, resulting in inaccurate results.

[0003] In the existing technology, the main methods for uranium analysis in water bodies are: (1) Spectroscopic methods, such as spectrophotometry and inductively coupled plasma atomic emission spectrometry (ICP-OES / AES). These methods are either susceptible to matrix interference or have strong signal interference, and their sensitivity is not suitable for the direct analysis of trace amounts of uranium in water bodies. (2) Radioactive analysis methods. This method has complex steps and requires pretreatment of complex samples. (3) Inductively coupled plasma mass spectrometry (ICP-MS), although it has high sensitivity and accuracy, has high requirements for sample pretreatment, and the instruments are expensive, with high operating costs and stringent requirements for sample preservation conditions. Summary of the Invention

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a direct mass spectrometry analysis device and method for trace uranium in water.

[0005] The technical solution of the present invention is as follows: A direct mass spectrometry method for analyzing trace amounts of uranium in water includes the following steps: S1: Immerse the gel film in uranium-containing wastewater, remove it and cut off the tip to obtain a gel film that adsorbs uranium; S2: Add the extractant to the gel film, and then apply a voltage of 3-5kV to the gel film, so that the uranium adsorbed on the gel film is extracted and moves towards the tip with the solvent to form a spray; the uranium is ionized in the form of uranyl acetate and detected by the mass spectrometry detection system.

[0006] Preferably, in step S1, the concentration of uranium-containing wastewater is 0.1-5 µg / L.

[0007] Preferably, in step S1, the gel film is cross-linked from an acrylamide gel and a polyhydroxy COF material.

[0008] Preferably, in step S2, the extractant is a methanol-acetic acid mixture.

[0009] The present invention also discloses a direct mass spectrometry analysis device for trace uranium in water, applicable to any of the analytical methods described above. The analytical device includes an in-situ sampling system, a solvent extraction system, a gel spray ionization system, and a mass spectrometry detection system. The in-situ sampling system includes a gel film for adsorbing uranium-containing wastewater; The solvent extraction system includes a solvent dropping device and a fixed platform for supporting a gel film adsorbed with uranium, the gel film adsorbed with uranium having a pointed tip; The gel spray ionization system includes a high-voltage power supply capable of applying voltage to the film; The mass spectrometry detection system includes a mass spectrometer, and the tip is 3-5 mm from the conical opening of the mass spectrometer.

[0010] Preferably, the uranium-adsorbed gel film is triangular.

[0011] Preferably, the in-situ sampling system includes a housing, a gel film is disposed inside the housing, and a plurality of through holes are disposed on the housing.

[0012] The beneficial effects of this invention are as follows: This invention achieves in-situ fixation of trace uranium in water by synthesizing a gel adsorption material (crosslinked with polyhydroxy COF and acrylamide gel), and then combining it with direct mass spectrometry (DMS) technology to achieve accurate analysis of trace uranium, while avoiding mass loss of uranium in water samples due to sample processing and preservation. This device can be applied to various complex aquatic environments. During analysis, the gel only needs to be cut into a pointed triangular shape, and voltage and extractant applied to achieve direct mass spectrometry analysis. It is simple to operate and has advantages such as fast analysis speed, good linearity, and low detection limit. Attached Figure Description

[0013] Figure 1 A direct mass spectrometry analysis device and flow chart for uranium in water; 100-in-situ sample collection device, 101-shell, 102-through hole, 103-gel film, 104-tip, 200-solvent dropping device, 300-high voltage power supply, 400-mass spectrometer. Figure 2 The images show mass spectrometry signals of uranium in water; a) shows the determination by the gel membrane adsorption method in Example 1, and b) shows the determination of uranium-containing aqueous solution by direct mass spectrometry. Figure 3 This is a collision-induced dissociation analysis diagram of uranyl acetate; Figure 4 The curves show the linearity of uranium concentrations in the range of 0.1–5 µg / L. Detailed Implementation

[0014] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0015] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0016] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0017] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0018] Reference Figure 1 Preferred embodiments of the present invention: A direct mass spectrometry analysis device for trace uranium in water, the analysis device comprising an in-situ sampling system 100, a solvent extraction system 200, a gel spray ionization system 3, and a mass spectrometry detection system; The in-situ sampling system includes a gel film 103 for adsorbing uranium-containing wastewater; The solvent extraction system includes a solvent dropping device 200 and a fixed platform supporting a uranium-adsorbed gel film, the uranium-adsorbed gel film having a tip 104. The gel spray ionization system includes a high-voltage power supply 300 capable of applying voltage to the film; The mass spectrometry detection system includes a mass spectrometer 400, with the tip being 3-5 mm from the conical opening of the mass spectrometer.

[0019] It may also have the following additional technical features: The uranium-adsorbed gel film is triangular, but not limited to this; it can also be other shapes with pointed ends.

[0020] In some embodiments, the in-situ sampling system 100 includes a housing 101, which is detachable and specifically comprises an upper shell and a lower shell. A gel film is disposed inside the housing, and several through holes 102 are provided on the upper and lower shells. Specifically, the housing is made of polypropylene, and the upper and lower shells can be fitted together to filter out insoluble impurities in the water. During sampling, the housing is immersed in the target water to ensure that the uranium in the water comes into full contact with the gel film. More specifically, the gel film is cross-linked from an acrylamide gel and a polyhydroxy COF material, and its dimensions are 2.5 cm in diameter and approximately 1.0 mm thick.

[0021] The polyhydroxy material used was prepared as follows: 2,4-Dicarboxymethyl phloroglucinol (55 mg) and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (159 mg) were placed in a 25 mL Pyrex tube. n-Butanol (1 mL) and o-dichlorobenzene (1 mL) were added, and the mixture was sonicated for 20 min. Then, acetic acid (6 M, 0.5 mL) was added, and the Pyrex tube was subjected to a freeze-degassing-thawing cycle in liquid nitrogen three times. After returning to room temperature, the tube was heated in a muffle furnace at 120 °C for 3 days. The resulting solid product was washed sequentially with acetone, N,N-dimethylacetamide, and deionized water. Finally, it was vacuum dried to obtain a brick-red powder.

[0022] The gel film was prepared by adding 0.003 g of laboratory-prepared polyhydroxy COF material powder (brick-red powder) to 10 mL of acrylamide solution, and then reacting it with ammonium persulfate initiator (70 mL) and tetramethylethylenediamine catalyst at 10% (w / v). After the solution had reacted completely and been thoroughly mixed, it was immediately cast between two glass plates separated by a 1.0 mm thick gasket and allowed to solidify at approximately 40°C for about 45 minutes. Once solidified, the gel could be cut and assembled into a sampling device.

[0023] During analysis, the gel film 103 is removed and cut into a triangular shape with a pointed tip. The cut gel film is fixed to the tip of the mass spectrometer 400 cone, with the tip approximately 3-5 mm from the cone. An extraction solvent, a methanol-acetic acid mixture, is added dropwise to the gel film 103 using a pipette, and a high voltage of 3-5 kV is applied to the gel film. Under the influence of the electric field and the extractant, the uranium adsorbed by the gel is effectively extracted and moves towards the tip with the solvent, forming a spray. Ultimately, the uranium is ionized as uranyl acetate and recorded by the mass spectrometry detection system. Quantitative analysis is performed based on the intensity of the mass spectrometry response signal of uranyl acetate.

[0024] It is understood that the present invention avoids the loss of uranium by fixing trace amounts of uranium in water in situ into a gel adsorbent material and then analyzing the gel material, rather than by preserving and analyzing the water sample.

[0025] Secondly, this invention organically combines electrospray ionization technology with direct mass spectrometry. By using gel materials as samples, direct mass spectrometry analysis can be achieved without the need for desorption or dissolution, avoiding cumbersome sample preparation and greatly shortening the analysis time.

[0026] In addition, the gel film in this invention combines the porous properties of gel materials with the excellent adsorption performance of uranium by multi-hydroxyl COF materials, thereby achieving in-situ enrichment and fixation of trace uranium in water and reducing the detection limit of the method.

[0027] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0028] Example 1

[0029] This method first enriches uranium (concentration below 5 µg / L) from the aquatic environment onto a gel adsorbent material, and then performs direct mass spectrometry analysis on the gel adsorbent material. The porous properties of the gel material and the pointed triangular shape after cutting allow for electrospray ionization under high voltage and extractant, eliminating the need for complex desorption and dissolution treatments of the gel membrane. One of the keys to this analytical method is the selection of a suitable extractant.

[0030] This embodiment uses a methanol-acetic acid mixed solution (volume ratio 1:1) as the extractant and a 3 µg / L uranium standard aqueous solution. This achieves good spray ionization and provides good extraction of uranium. Under the action of acetic acid, uranium reacts with acetic acid to generate uranyl acetate ions. In the negative ion scanning mode of mass spectrometry, with a voltage of 4 kV, a capillary temperature of 200 °C, and capillary and lens voltages set to -30 V and -50 V respectively, a detectable uranium signal with m / z 447 and the structure [UO2(CH3COO)3] can be obtained. - ( Figure 2 (a) To better analyze these ion peaks, collision-induced dissociation can be used as an auxiliary method; simultaneously, the results were compared with those obtained by direct electrospray mass spectrometry determination of aqueous solutions of the same concentration. Figure 2 In step b, the relative abundance of uranium signal (m / z 447) obtained by direct mass spectrometry analysis in uranium-containing aqueous solutions was significantly lower. Additionally, as... Figure 3 Applying a certain collision energy (30 eV) to the uranyl acetate complex m / z 447 yields a signal m / z 388 [UO2(CH3COO)2]. - This is due to the loss of an acetate ion at m / z 447. Further applying collision energy to m / z 388 will result in a ketene decarboxylation reaction to produce [UO2(CH3COO)(O)]. - Its mass-to-charge ratio (m / z) is 346. This confirms that the proposed technique can successfully perform in-situ fixation and direct mass spectrometry analysis of uranium in water.

[0031] Example 2

[0032] This embodiment evaluates the analytical performance of the method by establishing the relationship between signal intensity and concentration. For example, using fragment ions with a mass-to-charge ratio of 346 as the quantitative ion, a series of low-concentration uranium standard aqueous solutions (0.1-5 µg / L) were prepared, and enrichment and online analysis were performed using this device. Standard curves were then plotted. Figure 4 Experimental results show that this method can accurately determine trace amounts of uranium in water. The method exhibits good linear correlation within an extremely low concentration range (0.1-5 µg / L). Its linear regression equation is y = 61.271x + 33.673, with a correlation coefficient R0. 2 The result of 0.9993 demonstrates that the method has reliable quantitative analysis capability within this concentration range.

[0033] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0034] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of the present invention.

Claims

1. A direct mass spectrometry method for the analysis of trace uranium in water, characterized in that, Includes the following steps: S1: Immerse the gel film in uranium-containing wastewater, remove it and cut off the tip to obtain a gel film that adsorbs uranium; S2: Add the extractant to the gel film, and then apply a voltage of 3-5kV to the gel film, so that the uranium adsorbed on the gel film is extracted and moves towards the tip with the solvent to form a spray; the uranium is ionized in the form of uranyl acetate and detected by the mass spectrometry detection system.

2. The direct mass spectrometry analysis method for trace uranium in water as described in claim 1, characterized in that, In step S1, the concentration of uranium-containing wastewater is 0.1-5 µg / L.

3. The direct mass spectrometry analysis method for trace uranium in water according to claim 1, characterized in that, In step S1, the gel film is cross-linked from an acrylamide gel and a polyhydroxy COF material.

4. The direct mass spectrometry analysis method for trace uranium in water as described in claim 1, characterized in that, In step S2, the extractant is a methanol-acetic acid mixture with a volume ratio of 1:

1.

5. A direct mass spectrometry analysis apparatus for trace uranium in water, applied to the analytical method as described in any one of claims 1-4, characterized in that, The analytical apparatus includes an in-situ sampling system, a solvent extraction system, a gel spray ionization system, and a mass spectrometry detection system. The in-situ sampling system includes a gel film for adsorbing uranium-containing wastewater; The solvent extraction system includes a solvent dropping device and a fixed platform for supporting a gel film adsorbed with uranium, the gel film adsorbed with uranium having a pointed tip; The gel spray ionization system includes a high-voltage power supply capable of applying voltage to the film; The mass spectrometry detection system includes a mass spectrometer, and the tip is 3-5 mm from the conical opening of the mass spectrometer.

6. The analytical apparatus according to claim 5, characterized in that, The uranium-adsorbed gel film is triangular.

7. The analytical apparatus according to claim 5, characterized in that, The in-situ sampling system includes a housing, inside which a gel film is disposed, and the housing has several through holes.

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