Laser fluorescence uranium measurement method based on fluorescence enhancer

Abstract

The invention discloses a laser fluorescence uranium measurement method based on a fluorescence enhancer. The laser fluorescence uranium measurement method comprises the following steps: pre-treating a sample; precisely weighing 0.1000 g of a sample, and placing the sample in a porcelain crucible; heating the sample in a muffle furnace at 600 DEG C for 1 hour to remove sulfur and organic matters in the sample, taking out the crucible through a mechanical arm, and brushing the powder into a polytetrafluoroethylene crucible after the crucible is taken out; treating a sample; adding a mixed solution of 5mL of nitric acid, 3mL of perchloric acid and 2mL of hydrofluoric acid into the sample powder in the step 1.1; placing the crucible on a temperature-controlled electric heating plate, heating for 1 hour at the temperature of less than or equal to 300 DEG C, and after the sample is completely decomposed, opening a cover and evaporating until the white smoke is completely dispersed; cooling, adding 1mL of nitric acid to wash the inner wall of the crucible, and heating again until the sample solution is concentrated to be in a wet salt state; when the laser fluorescence uranium measurement method based on the fluorescence enhancer is used, suspended solids of high-sulfur and high-organic-matter samples can be effectively eliminated, the treatment time can be shortened, and the whole detection method is more efficient and accurate and suitable for application and popularization.

Description

Technical Field

[0001] This invention relates to the field of uranium ore detection and analysis technology, and in particular to a laser fluorescence method for uranium determination based on a fluorescence enhancer. Background Technology

[0002] In uranium exploration and development, accurate detection of trace uranium is crucial for assessing uranium reserves and guiding mining processes. Currently, the main methods for detecting trace uranium in uranium ore include inductively coupled plasma mass spectrometry (ICP-MS) and laser fluorescence spectrometry. While ICP-MS offers high accuracy, it is expensive, complex to operate, and requires stringent environmental conditions. Laser fluorescence spectrometry, on the other hand, is widely used in uranium analysis due to its low detection limit (down to the μg / g level), lower cost, and elimination of complex sample enrichment and separation steps.

[0003] In existing conventional laser fluorescence detection methods, the typical operational steps include sample pretreatment, solution preparation, fluorescence intensity measurement, and result calculation. In the sample pretreatment stage, current technologies often employ methods such as open-air acid dissolution, alkali fusion, and dry ashing. Dry ashing requires calcining the sample at 600℃ for 2-3 hours, followed by cooling and then acid dissolution, making the entire pretreatment process time-consuming. Open-air acid dissolution often uses single or mixed acid systems such as nitric acid and hydrochloric acid; however, for high-sulfur and high-organic-matter uranium ore samples, incomplete acid dissolution is prone to occur, producing a large amount of suspended matter. This suspended matter can adhere to the inner wall of the detection container or scatter the laser, severely affecting the accuracy of fluorescence intensity measurement. While alkali fusion can solve the problem of incomplete sample decomposition to some extent, the operation process is cumbersome, and excessive matrix impurities are easily introduced during alkali fusion, leading to deviations in the detection results. Although microwave digestion has high decomposition efficiency, the amount of sample that can be processed at one time is limited (usually only 1-2 samples), and it requires sophisticated equipment, making it unsuitable for the detection needs of large batches of samples.

[0004] In summary, there is an urgent need for an efficient and accurate laser fluorescence method for uranium determination to overcome the aforementioned technical deficiencies. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems by providing a laser fluorescence uranium determination method based on a fluorescence enhancer that can effectively eliminate suspended matter in high-sulfur and high-organic-matter samples, shorten processing time, and make the overall detection method more efficient and accurate.

[0006] To achieve the above objectives, the technical solution of the present invention is: a laser fluorescence method for uranium determination based on a fluorescence enhancer, comprising the following steps: Step 1: Sample pretreatment; Step 1.1: Accurately weigh 0.1000g of the sample and place it in a porcelain crucible; heat it in a muffle furnace at 600℃ for 1 hour to remove sulfur and organic matter from the sample, and remove the crucible by a robotic arm. After removal, brush the powder into the polytetrafluoroethylene crucible. Step 2, Sample processing; Step 2.1: Add a mixture of 5 mL nitric acid, 3 mL perchloric acid and 2 mL hydrofluoric acid to the sample powder from Step 1.1; Step 2.2: Place the crucible on a temperature-controlled heating plate and heat at ≤300℃ for 1 hour. After the sample has completely decomposed, open the lid and evaporate until the white smoke dissipates. 2.3 After cooling, add 1 mL of nitric acid to wash the inner wall of the crucible, and heat again until the sample solution is concentrated to a wet salt state; 2.4. Add 5 mL of (1+2) nitric acid mixture and an appropriate amount of ultrapure water while hot, heat until the solution is clear, cool and transfer to a 50 mL volumetric flask, dilute to volume and shake well for later use. 2-3 reagent blanks need to be set up for each batch. Step 3: Detection and Interference Control; Step 3.1: Transfer 0.5 mL of the pretreated solution to a quartz cuvette, add 4.5 mL of deionized water, and measure the initial fluorescence intensity (F); after rinsing the cuvette, add 0.5 mL of sample solution, 0.5 mL of sodium hydroxide solution, and 4.0 mL of mixed reagent, and stir well; if the manganese ion content in the sample is high, add 0.02 mol / L EDTA solution to the hydrochloric acid extract for masking; if the iron ion content is high, reduce its concentration by dilution; Step 3.2: Measure the fluorescence intensity (F1), then add 0.020-0.050 mL of uranium standard solution (concentration 0.24 g / mL or 1.04 g / mL), mix well, and then measure the fluorescence intensity (F2); test the blank solution simultaneously. Step 4: Calculate the result. Use the following formula to calculate the mass fraction of uranium. ; In the formula: ω is the mass fraction of uranium in the sample; F is the fluorescence intensity of the sample solution before the addition of the mixed reagent; F1 is the fluorescence intensity reading obtained after adding the mixed solution; F2 is the fluorescence signal obtained after adding the standard uranium solution; Vs is the volume of the uranium standard solution added to the sample, in mL; m is the sample weight, in g; V1 / V2 refers to the ratio of the total fixed volume of the sample solution to the volume taken for detection; C is the concentration of the uranium standard solution, in μg / mL; K is the volume correction factor, calculated by the formula (Vt+Vs) / Vt.

[0007] Preferably, the mixed reagent in step 3.1 is a mixture of fluorescence enhancer, EDTA (disodium ethylenediaminetetraacetate), and buffer solution; wherein the concentration of EDTA solution is 0.01~0.1 mol / L, the mass of potassium dihydrogen phosphate required to prepare 1L of buffer solution is 3~8g, and the mass of potassium hydrogen phosphate is 7~12g.

[0008] Preferably, the buffer solution is a phosphate buffer solution, and the volume ratio of the fluorescence enhancer, EDTA and buffer solution is 1:2:7.

[0009] Preferably, in step 3.1, when the manganese ion concentration in the sample is ≥0.1 mg / L, 0.02 mol / L EDTA solution is added to the mixed solution.

[0010] Preferably, in step 3.1, when the iron ion concentration in the sample is ≥0.5mg / L, ultrapure water is used for dilution, and the dilution factor is 5-10 times.

[0011] Preferably, the muffle furnace has a heating chamber for storing crucibles inside, and the heating chamber is sealed and covered by a door. The crucibles are put into or taken out by a clamping mechanism. The clamping mechanism includes cylinder jaws, and symmetrically arranged swing arms are provided on the outer side of the cylinder jaws. The ends of the swing arms are provided with semi-circular rings, and the semi-circular rings are driven by the cylinder jaws to contact or move away from the crucibles.

[0012] Preferably, the outer side of the cylinder gripper is fixedly connected to the horizontally arranged optical axis, which can move horizontally. When the optical axis extends, the semi-circular ring sends the crucible into the heating chamber through the cylinder gripper; when the optical axis retracts, the semi-circular ring removes the crucible through the cylinder gripper.

[0013] Preferably, an outer support is also provided on the outside of the muffle furnace, and a movable push plate is provided on the surface of the outer support. A stepper motor is provided on the side of the movable push plate away from the muffle furnace. The output shaft of the stepper motor is coaxially and fixedly connected to the optical axis. After the stepper motor is running, it drives the crucible to rotate.

[0014] Preferably, the surface of the outer support is provided with a guide rail, the bottom of the movable push plate is provided with a slider that cooperates with the guide rail, the end of the outer support is provided with a second stepper motor, the output end of the second stepper motor is fixed with a lead screw, the lead screw passes through the movable push plate and extends towards the muffle furnace, and the second stepper motor drives the crucible to enter and exit the heating chamber after running.

[0015] Preferably, a multi-axis robotic arm is also provided on one side of the outer support, and the output end of the robotic arm is provided with a steel brush for brushing away powder in the crucible.

[0016] This invention discloses a laser fluorescence method for uranium determination based on a fluorescence enhancer, comprising the following steps: sample pretreatment; accurately weighing 0.1000g of sample and placing it in a porcelain crucible; heating in a muffle furnace at 600℃ for 1 hour to remove sulfur and organic matter from the sample, and then removing the crucible using a robotic arm, and brushing the powder into a polytetrafluoroethylene crucible; sample processing; adding a mixture of 5mL nitric acid, 3mL perchloric acid and 2mL hydrofluoric acid to the sample powder from step 1.1; placing the crucible on a temperature-controlled heating plate and heating at ≤300℃ for 1 hour until the sample is completely decomposed, then opening the lid and evaporating until the white smoke dissipates; cooling and adding 1mL nitric acid to wash the inner wall of the crucible, and then heating again until the sample solution is concentrated to a wet salt state; compared with the prior art, this laser fluorescence method for uranium determination based on a fluorescence enhancer has the advantages of effectively eliminating suspended matter in high-sulfur and high-organic-matter samples, shortening the processing time, and making the overall detection method more efficient and accurate. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the muffle furnace in this invention.

[0018] Figure 2 This is a schematic diagram of the structure of the external support in this invention.

[0019] Figure 3 This is a schematic diagram showing the fit between the muffle furnace and the outer support in this invention.

[0020] In the diagram: 1. Muffle furnace; 2. Door; 3. Heating chamber; 4. Outer support; 5. Robotic arm; 51. Steel brush; 6. Cylinder gripper; 61. Swing arm; 62. Semicircular ring; 7. Optical axis; 8. Moving push plate; 81. Guide rail; 82. Stepper motor one; 9. Stepper motor two; 91. Lead screw; 10. Crucible. Detailed Implementation

[0021] A laser fluorescence method for uranium determination based on a fluorescence enhancer includes the following steps: Step 1: Sample pretreatment; Step 1.1: Accurately weigh 0.1000g of the sample and place it in a porcelain crucible; heat it in a muffle furnace at 600℃ for 1 hour to remove sulfur and organic matter from the sample, and remove the crucible by a robotic arm. After removal, brush the powder into the polytetrafluoroethylene crucible. Step 2, Sample processing; Step 2.1: Add a mixture of 5 mL nitric acid, 3 mL perchloric acid and 2 mL hydrofluoric acid to the sample powder from Step 1.1; Step 2.2: Place the crucible on a temperature-controlled heating plate and heat at ≤300℃ for 1 hour. After the sample has completely decomposed, open the lid and evaporate until the white smoke dissipates. 2.3 After cooling, add 1 mL of nitric acid to wash the inner wall of the crucible, and heat again until the sample solution is concentrated to a wet salt state; 2.4. Add 5 mL of (1+2) nitric acid mixture and an appropriate amount of ultrapure water while hot, heat until the solution is clear, cool and transfer to a 50 mL volumetric flask, dilute to volume and shake well for later use. 2-3 reagent blanks need to be set up for each batch. Step 3: Detection and Interference Control; Step 3.1: Transfer 0.5 mL of the pretreated solution to a quartz cuvette, add 4.5 mL of deionized water, and measure the initial fluorescence intensity (F); after rinsing the cuvette, add 0.5 mL of sample solution, 4.5 mL of sodium hydroxide solution, and 4.0 mL of mixed reagent, and stir well; if the manganese ion content in the sample is high, add 0.02 mol / L EDTA solution to the hydrochloric acid extract for masking; if the iron ion content is high, reduce its concentration by dilution; The mixed reagent is a mixture of fluorescence enhancer, EDTA (disodium ethylenediaminetetraacetate) and buffer solution; the concentration of EDTA solution is 0.01~0.1 mol / L, and the required mass of potassium dihydrogen phosphate and potassium hydrogen phosphate is 3~8g and 7~12g respectively to prepare 1L of buffer solution. The buffer solution is a phosphate buffer, and the volume ratio of the fluorescence enhancer, EDTA and buffer solution is 1:2:7. When the concentration of manganese ions in the sample is ≥0.1 mg / L, add 0.02 mol / L EDTA solution to the mixed solution; Step 3.2: Measure the fluorescence intensity (F1), then add 0.020-0.050 mL of uranium standard solution (concentration 0.24 g / mL or 1.04 g / mL), mix well, and then measure the fluorescence intensity (F2); test the blank solution simultaneously. Step 4: Calculate the result. Use the following formula to calculate the mass fraction of uranium. ; In the formula: ω is the mass fraction of uranium in the sample; F is the fluorescence intensity of the sample solution before the addition of the mixed reagent; F1 is the fluorescence intensity reading obtained after adding the mixed solution; F2 is the fluorescence signal obtained after adding the standard uranium solution; Vs is the volume of the uranium standard solution added to the sample, in mL; m is the sample weight, in g; V1 / V2 refers to the ratio of the total fixed volume of the sample solution to the volume taken for detection; C is the concentration of the uranium standard solution, in μg / mL; K is the volume correction factor, calculated by the formula (Vt+Vs) / Vt.

[0022] Furthermore, in step 3.1, when the iron ion concentration in the sample is ≥0.5mg / L, ultrapure water is used for dilution, with a dilution factor of 5-10 times.

[0023] Based on the above embodiments, sample pretreatment can also be carried out by ashing treatment, specifically: accurately weigh 0.1000g of sample into a porcelain crucible, heat it for 1 hour at ≤300℃ on a temperature-controlled electric heating plate to remove sulfur and organic matter from the sample.

[0024] In the pretreatment stage, multiple groups of 0.1000g unknown samples and samples with different contents of certified reference materials were weighed in parallel and treated in various ways. The digestion effects are listed in Tables 1 and 2. Table 1 shows that the untreated unknown sample still had a large amount of black suspended matter on the liquid surface after being brought to volume, shaken, and allowed to stand for 12 hours. However, the samples pretreated with ashing, aqua regia, sulfuric acid, and perchloric acid + nitric acid showed clear solutions after being brought to volume, shaken, and allowed to stand for 12 hours. Table 2 shows that failure to pretreat the samples before mixed acid digestion leads to large fluctuations in sample test results. Treating the samples with ashing and perchloric acid resulted in better accuracy and consistency of the test results. In samples pretreated with hydrogen peroxide, the test results were lower due to splashing during the treatment process. Because the sulfuric-phosphoric acid mixture is a non-volatile acid, it could not be evaporated to dryness even after prolonged pretreatment, resulting in no test results. Sulfuric acid pretreatment was time-consuming and resulted in higher test results. Two ashing methods were used: ashing method 1 and ashing method 2. For ashing method 1, 0.1000g of sample was directly weighed into a ceramic crucible, calcined at 600℃ for 2-3 hours, and then cooled to room temperature before being carefully transferred to a polytetrafluoroethylene crucible for pretreatment. For ashing method 2, approximately 1g of sample was weighed into a ceramic crucible, the weight of the crucible and the sample were recorded, and the sample was calcined at 600℃ for 2-3 hours. After cooling to room temperature, the total weight of the crucible and the sample after calcination was recorded, and the change in sample weight before and after calcination was calculated. 0.1000g of sample was weighed for pretreatment, and the sample weight change coefficient was considered when calculating the results.

[0025] Table 1 above shows the effects of different pretreatment schemes.

[0026] Table 2 above shows the test results for different pretreatment schemes.

[0027] In summary, pretreatment of uranium-bearing ores with high sulfur and high organic matter content using perchloric acid, nitric acid, and ashing can meet the detection requirements. After adding 1 mL of perchloric acid and 1 mL of nitric acid to the sample, it is evaporated to near dryness on a hot plate at approximately 220°C. Then, another 1 mL of perchloric acid and 1 mL of nitric acid are added, and the mixture is evaporated to near dryness. Subsequently, the sample is processed according to the sample pretreatment steps. The resulting HClO4+HNO3-treated sample has high detection accuracy and is more time-efficient compared to the ashing method.

[0028] By comparing different pretreatment methods, a method for batch analysis of high-sulfur and high-organic-matter samples was determined, and the influencing factors in the analysis process were investigated. (1) This method utilizes perchloric acid + nitric acid pretreatment, which can effectively solve the problem of a large amount of suspended matter in high sulfur and high organic matter samples in general processing procedures. Compared with methods such as high temperature ashing, this method is more time-efficient.

[0029] (2) Elements such as iron, manganese, and chlorine have strong ultraviolet light absorption properties, which can easily suppress the fluorescence emission signal of uranium, resulting in a "quenching effect" that reduces fluorescence intensity. The introduction of fluorescence enhancers can improve the luminescence intensity of uranyl ions to a certain extent, and also mask some interfering ions. The effect on iron ions is limited, while the shielding ability for manganese ions is poor. Adding EDTA solution can effectively reduce the interference of manganese ions.

[0030] In this invention, the muffle furnace 1 has a heating chamber 3 inside for storing the crucible 10. The heating chamber 3 is sealed and covered by a door 2. The crucible 10 is placed in or removed by a clamping mechanism. The clamping mechanism includes a cylinder gripper 6. The outer side of the cylinder gripper 6 is provided with symmetrically arranged swing arms 61. The end of the swing arm 61 is provided with a semi-circular retaining ring 62. The semi-circular retaining ring 62 is driven by the cylinder gripper 6 to contact or move away from the crucible 10. When it is necessary to clamp the crucible for placement or removal, the cylinder gripper 6 drives the swing arms 61 on both sides to swing, thereby clamping the crucible 10 through the semi-circular retaining ring 62. When the crucible 10 is placed in place, the semi-circular retaining ring 62 swings outward to release the crucible 10, thereby avoiding manual handling and improving the safety of the testing process.

[0031] The outer side of the cylinder gripper 6 is fixedly connected to the horizontally arranged optical axis 7. The optical axis 7 can move horizontally. When the optical axis 7 extends, the semi-circular ring 62 sends the crucible 10 into the heating chamber 10 through the cylinder gripper 6. When the optical axis 7 retracts, the semi-circular ring 62 takes out the crucible 10 through the cylinder gripper 6. That is to say, the purpose of extending and retracting the optical axis 7 is to place or take out the crucible 10 into the heating chamber 3, and the whole process reduces manual intervention.

[0032] In this embodiment, an outer support 4 is also provided on the outside of the muffle furnace 1. A movable push plate 8 is provided on the surface of the outer support 4. A stepper motor 82 is provided on the side of the movable push plate 8 away from the muffle furnace 1. The stepper motor 82 is fixed on the movable push plate 8. The output shaft of the stepper motor 82 is coaxially and fixedly connected to the optical axis 7. After the stepper motor 82 runs, it drives the crucible 10 to rotate. After the sample is heated in the crucible, the optical axis 7 moves towards the muffle furnace 1. After moving, the cylinder gripper 6 opens and then clamps the crucible 10. Then the optical axis 7 retracts. After retraction, the stepper motor 82 starts. After starting, the optical axis 7 and the cylinder gripper 6 rotate and move by an angle. During this process, the two semi-circular clamping rings 62 always clamp the crucible 10, so as to facilitate the internal powder to leave the crucible.

[0033] In order to realize the telescopic movement of the optical axis 7, the surface of the outer support 4 is provided with a guide rail 81, the bottom of the movable push plate 8 is provided with a slider that cooperates with the guide rail 81, the end of the outer support 4 is provided with a stepper motor 9, the output end of the stepper motor 9 is fixed with a lead screw 91, the lead screw 91 extends through the movable push plate 8 toward the muffle furnace 1, and the stepper motor 9 drives the crucible 10 to enter and exit the heating chamber 3 after running.

[0034] In other words, the lead screw 91 is engaged with the movable push plate 8 through the thread. When the lead screw 91 rotates, the movable push rod 8 is driven to move in a straight line along the trajectory of the guide rail 81 due to the thread action. Since the stepper motor 82 and the optical shaft are connected to the movable push plate 8, the movement of the movable push plate 8 drives the stepper motor 82 and the optical shaft to move, thereby realizing the semi-circular ring 6 extending into or retracting into the heating chamber to meet the needs of taking out and placing the crucible.

[0035] To facilitate the removal of powder from the crucible, a multi-axis robotic arm 5 is also provided on one side of the outer support 4. The output end of the robotic arm 5 is equipped with a steel brush 51 for brushing away powder from the crucible. The steel brush 51 is cylindrical and rotates by a motor. When the stepper motor 82 tilts the crucible 10 at a certain angle, the robotic arm 5 moves and drives the steel brush 51 to extend into the crucible. The rotation of the steel brush brushes out the powder adhering to the inner wall for subsequent testing.

[0036] The outer support 4 structure enables automatic loading and unloading of the crucible, and the powder inside the sample can be easily removed after heating, reducing or eliminating manual intervention and achieving a high degree of automation.

[0037] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A laser fluorescence method for uranium determination based on a fluorescence enhancer, characterized in that, Includes the following steps: Step 1: Sample pretreatment; Step 1.1: Accurately weigh 0.1000g of the sample and place it in a porcelain crucible; heat it in a muffle furnace at 600℃ for 1 hour to remove sulfur and organic matter from the sample, and remove the crucible by a robotic arm. After removal, brush the powder into the polytetrafluoroethylene crucible. Step 2, Sample processing; Step 2.1: Add a mixture of 5 mL nitric acid, 3 mL perchloric acid and 2 mL hydrofluoric acid to the sample powder from Step 1.1; Step 2.2: Place the crucible on a temperature-controlled heating plate and heat at ≤300℃ for 1 hour. After the sample has completely decomposed, open the lid and evaporate until the white smoke dissipates. 2.3 After cooling, add 1 mL of nitric acid to wash the inner wall of the crucible, and heat again until the sample solution is concentrated to a wet salt state; 2.

4. Add 5 mL of (1+2) nitric acid mixture and an appropriate amount of ultrapure water while hot, heat until the solution is clear, cool and transfer to a 50 mL volumetric flask, dilute to volume and shake well for later use. 2-3 reagent blanks need to be set up for each batch. Step 3: Detection and Interference Control; Step 3.1: Transfer 0.5 mL of the pretreated solution to a quartz cuvette, add 4.5 mL of deionized water, and measure the initial fluorescence intensity (F). After rinsing the cuvette, add 0.5 mL of sample solution, 0.5 mL of sodium hydroxide solution, and 4.0 mL of mixed reagent, and stir well. If the manganese ion content in the sample is high, add 0.02 mol / L EDTA solution to the mixed reagent for masking; otherwise, add water to make up the corresponding proportion. If the iron ion content is high, reduce its concentration by dilution. Step 3.2: Measure the fluorescence intensity (F1), then add 0.020-0.050 mL of uranium standard solution (concentration 0.24 g / mL or 1.04 g / mL), mix well, and then measure the fluorescence intensity (F2); test the blank solution simultaneously. Step 4: Calculate the result. Use the following formula to calculate the mass fraction of uranium. ； In the formula: ω is the mass fraction of uranium in the sample; F is the fluorescence intensity of the sample solution before the addition of the mixing reagent; F1 is the fluorescence intensity reading obtained after the addition of the mixing solution; F2 is the fluorescence signal obtained after adding the standard uranium solution; Vs is the volume of the uranium standard solution added to the sample, in mL; m is the weight of the sample, in g; V1 / V2 refers to the ratio of the total fixed volume of the sample solution to the volume taken for detection; C is the concentration of the uranium standard solution, in μg / mL; K is the volume correction factor, calculated by the formula (Vt+Vs) / Vt.

2. The laser fluorescence method for uranium determination based on a fluorescence enhancer according to claim 1, characterized in that, The mixed reagent in step 3.1 is a mixture of fluorescence enhancer, EDTA (disodium ethylenediaminetetraacetate), and buffer solution; wherein the concentration of EDTA solution is 0.01~0.1 mol / L, and the required mass of potassium dihydrogen phosphate and potassium hydrogen phosphate is 3~8g and 7~12g respectively to prepare 1L of buffer solution.

3. The laser fluorescence method for uranium determination based on a fluorescence enhancer according to claim 2, characterized in that, The buffer solution is a phosphate buffer, and the volume ratio of the fluorescence enhancer, EDTA and buffer solution is 1:2:

7.

4. The laser fluorescence method for uranium determination using a fluorescence enhancer according to claim 1, characterized in that, In step 3.1, when the concentration of manganese ions in the sample is ≥0.1 mg / L, 0.02 mol / L EDTA solution is added to the mixed solution.

5. The laser fluorescence method for uranium determination using a fluorescence enhancer according to claim 1, characterized in that, In step 3.1, when the iron ion concentration in the sample is ≥0.5mg / L, ultrapure water is used for dilution, with a dilution factor of 5-10 times.

6. The laser fluorescence method for uranium determination using a fluorescence enhancer according to any one of claims 1-5, characterized in that, The muffle furnace has a heating chamber for storing crucibles. The heating chamber is sealed with a door. The crucibles are placed in or removed by a clamping mechanism. The clamping mechanism includes cylinder jaws. The outer side of the cylinder jaws is provided with symmetrically arranged swing arms. The end of the swing arms is provided with a semi-circular retaining ring. The semi-circular retaining ring is driven by the cylinder jaws to contact or move away from the crucible.

7. The laser fluorescence method for uranium determination using a fluorescence enhancer according to claim 6, characterized in that, The outer side of the cylinder gripper is fixedly connected to the horizontally set optical axis. The optical axis can move horizontally. When the optical axis extends, the semi-circular ring sends the crucible into the heating chamber through the cylinder gripper. When the optical axis retracts, the semi-circular ring takes out the crucible through the cylinder gripper.

8. The laser fluorescence method for uranium determination using a fluorescence enhancer according to claim 7, characterized in that, An outer support is also provided on the outside of the muffle furnace. A movable push plate is provided on the surface of the outer support. A stepper motor is provided on the side of the movable push plate away from the muffle furnace. The output shaft of the stepper motor is coaxially and fixedly connected to the optical axis. After the stepper motor runs, it drives the crucible to rotate.

9. The laser fluorescence method for uranium determination using a fluorescence enhancer according to claim 8, characterized in that, The outer support is provided with a guide rail on its surface, and the bottom of the movable push plate is provided with a slider that cooperates with the guide rail. The end of the outer support is provided with a second stepper motor, and the output end of the second stepper motor is fixed with a lead screw. The lead screw passes through the movable push plate and extends towards the muffle furnace. After the second stepper motor runs, it drives the crucible to enter and exit the heating chamber.

10. The laser fluorescence method for uranium determination using a fluorescence enhancer according to claim 9, characterized in that, A multi-axis robotic arm is also provided on one side of the outer support, and the output end of the robotic arm is provided with a steel brush to remove powder from the crucible.

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