Method for determining content of ultra-trace rare earth elements in high-purity tungsten trioxide

Abstract

The application provides a method for determining the content of ultra-trace rare earth elements in high-purity tungsten trioxide, and particularly relates to a preparation of a quality control sample for tungsten trioxide rare earth component analysis and a method for determining the content of 14 kinds of ultra-trace rare earth elements in high-purity tungsten trioxide. The method is simple and easy to operate, solves the problem of accurate quantitative analysis of 14 kinds of ultra-trace rare earth impurities in high-purity tungsten trioxide, and solves the problem of no same-substrate quality control sample through a rapid preparation method of the quality control sample for tungsten trioxide rare earth component analysis.

Description

Technical Field

[0001] This invention belongs to the field of high-purity tungsten material analysis technology, and relates to a method for determining the content of ultra-trace rare earth elements in high-purity tungsten trioxide. Specifically, it relates to the preparation of quality control samples for rare earth component analysis of tungsten trioxide and the method for determining the content of 14 ultra-trace rare earth elements in high-purity tungsten trioxide. Background Technology

[0002] High-purity tungsten trioxide (purity ≥99.99%, i.e., 4N and above) has core applications in tungsten metal preparation, electronics and semiconductors, energy storage and new energy, ceramics and optics due to its high purity, low impurities, and stable physicochemical properties. It is a key material for many high-end technologies. Tungsten trioxide is an important intermediate product in the production of high-purity tungsten powder and high-purity sputtering tungsten targets, and its purity directly affects the performance of high-purity tungsten products. According to the non-ferrous metals industry standard YS / T 1726-2025 "High-purity Tungsten Trioxide", high-purity tungsten trioxide includes three grades: 4N, 5N, and 6N, with the individual requirement for 14 rare earth impurities not exceeding 0.1 × 10⁻⁶. -4 %~0.005×10 -4 %, while according to GB / T 14666 "Analytical Chemistry Terminology", the mass fraction of the analyte is less than 1×10⁻⁶. -4 The percentage (%) falls under the category of ultra-trace analysis. Ultra-trace analysis typically faces challenges such as excessively high reagent blanks introduced by sample pretreatment, high limits of quantitation (LOQs), and difficulties in confirming the accuracy of results due to a lack of standard materials. Therefore, optimizing sample pretreatment methods to control reagent blanks, separating and concentrating matrix impurities to significantly reduce the LQ, and preparing targeted quality control samples for tungsten trioxide rare earth analysis are crucial for the accurate analysis of 14 ultra-trace rare earth impurities in high-purity tungsten trioxide. Summary of the Invention

[0003] This invention aims to solve the above-mentioned problems and provides a method for determining the content of 14 ultra-trace rare earth elements (lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium) in high-purity tungsten trioxide. The accuracy of the method is verified by inventing a rapid method for preparing a quality control sample for rare earth element analysis in tungsten trioxide. This method involves preparing a high-purity tungsten trioxide rare earth element analysis quality control sample, which achieves ultra-trace rare earth element determination by precipitating a tungsten matrix and concentrating impurities.

[0004] The technical solution of the present invention is as follows:

[0005] A method for determining the content of ultra-trace rare earth elements in high-purity tungsten trioxide, characterized by comprising the following steps:

[0006] S1. Using high-purity tungsten powder as raw material, rapidly prepare quality control samples for rare earth component analysis of tungsten trioxide;

[0007] S2. Accurately weigh the high-purity tungsten trioxide sample, place it in a beaker, and perform a blank experiment accordingly.

[0008] S3. Add appropriate proportions of ammonia and hydrogen peroxide to the beaker in step S2, heat to dissolve the sample, and then concentrate it to a small volume.

[0009] S4. Precipitate the tungsten matrix in the concentrated solution obtained in step S3, and heat it on a hot plate until the precipitate changes color. Transfer it to a 10 mL centrifuge tube and let it stand overnight or centrifuge to obtain the analytical solution.

[0010] S5. Digest the tungsten trioxide rare earth component analysis quality control sample prepared in step S1 according to the processing methods of steps S2, S3 and S4, and dilute the supernatant 10 times for analysis.

[0011] S6. Prepare mixed standard solutions of 14 rare earth elements with mass concentrations of 0, 2 ng / mL, 4 ng / mL, 6 ng / mL, and 8 ng / mL, wherein the 14 rare earth elements include lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; and prepare a Cs solution with a mass concentration of 100 ng / mL as an internal standard solution, with 2% nitric acid as the medium;

[0012] S7. On an inductively coupled plasma mass spectrometer, an internal standard solution is introduced through a three-way valve, and the series of standard solutions prepared in S6 and the analytical solution obtained in S4 are measured sequentially. Working curves for each element are plotted with the ratio of the signal intensity of the analyte to the internal standard element in the analytical solution as the ordinate and the mass concentration of the analyte as the abscissa (linear correlation coefficients are all not less than 0.999). The mass concentrations of the 14 rare earth elements are calculated based on the corresponding working curves.

[0013] S8. Calculate the mass fraction of rare earth elements in high-purity tungsten trioxide based on the mass concentration of the element to be analyzed in the test solution, the volume of the test solution, and the sample weight, and calculate the recovery rate based on the theoretical and actual measured values ​​of rare earth elements in the quality control sample.

[0014] in,

[0015] The preparation steps for the quality control sample used in step S1 for the rare earth element composition analysis of tungsten trioxide are as follows:

[0016] (1) Accurately weigh 0.7930g of high-purity tungsten powder and place it in a platinum crucible. Add 10mL to 15mL of hydrogen peroxide in 3 to 4 portions. After the violent reaction stops, heat it on a hot plate until it is completely dissolved.

[0017] (2) After the high-purity tungsten powder in step (1) has completely dissolved, add 0.20 mL of a mixed standard solution of rare earth elements with a mass concentration of 10 μg / mL for each impurity element to the platinum crucible, heat it on a 180°C hot plate to evaporate the liquid, and then raise it to 250°C and continue heating for 20 min to fully evaporate the salts.

[0018] (3) After the salts are fully evaporated, place the platinum crucible from step (2) in a muffle furnace at room temperature. The temperature control program slowly raises the temperature from room temperature to 600°C within 1 hour, and then keeps it at that temperature for 1 hour until it is completely turned yellow.

[0019] (4) After the crucible in step (3) is cooled down, it is taken out and then ground in an agate mortar for 20 min to 30 min to ensure the uniformity of the quality control sample; thus, the quality control sample is obtained.

[0020] In step S3, high-purity tungsten trioxide is moistened with 3 mL of deionized water, and then ammonia is added in two portions. The first time, 3 mL of ammonia is added, and the mixture is heated at 220°C for about 20 minutes until most of the sample dissolves and turns from yellow to white. The second time, 2 mL of ammonia is added, and the mixture is heated until the sample is completely dissolved. The watch glass is removed, and the mixture is heated again. The sample solution is then evaporated to a small volume (about 2 mL), thus completing the digestion of the high-purity tungsten trioxide sample.

[0021] The precipitation of the tungsten matrix in step S4 is as follows: After the sample solution digested in step S3 is removed and cooled, 1 mL of nitric acid is added. A white precipitate appears when the beaker is shaken. Then, it is heated on a hot plate at 220°C for about 5 minutes, and the precipitate changes from white to yellow. The mixture in the beaker is then transferred to a 10 mL centrifuge tube with deionized water and left to stand overnight or centrifuged at 4000 r / min for 5 minutes to obtain the supernatant as the analytical solution.

[0022] In step S7, when performing the determination on an inductively coupled plasma mass spectrometer, it is necessary to optimize the instrument parameters and select the optimal isotope mass number for the analyte to eliminate mass spectrometry interference and reduce the method limit of quantitation.

[0023] To obtain optimal sensitivity, instrument parameters such as RF generator power, sampling depth, and lens parameters need to be optimized (RF generator power 1550W, sampling depth 8.0mm, Omega deflection voltage -80V, quadrupole mass gain 125, kinetic energy discrimination 3mV~5mV, quadrupole deflection voltage -5V~5V). To eliminate matrix effects, the gas flow rates of nebulizer and dilution gas need to be optimized (nebulizer gas 0.6L / min, dilution gas 0.5L / min). In addition, to eliminate mass spectrometry interference, it is necessary to select isotope mass numbers with high abundance and no isotope interference to establish the analytical method. The limit of quantitation needs to be calculated according to 10 times the blank standard deviation (number of measurements n=11), that is, the signal intensity of each rare earth element in the blank solution is measured 11 times consecutively, the standard deviation is calculated, and the limit of quantitation is calculated according to the concentration corresponding to 10 times the standard deviation. This determines which grades of high-purity tungsten trioxide the method can meet for the determination of rare earth element content.

[0024] In step S8, the mass concentration of the element to be tested is obtained based on the working curve in step S7. The mass fraction of rare earth elements in high-purity tungsten trioxide and the recovery rate of the quality control sample are calculated by combining the test liquid volume, sample weight and spiking amount. A recovery rate of 90% to 110% is considered a satisfactory result.

[0025] The beneficial effects of this invention are:

[0026] (1) In the test method of the present invention, the quality control sample for rare earth component analysis of tungsten trioxide prepared is similar in physicochemical properties to the high-purity tungsten trioxide sample to be analyzed, which can effectively verify the accuracy of the test method;

[0027] (2) In the test method of the present invention, the tungsten matrix is ​​precipitated simultaneously during the acidification process of the tungsten trioxide solution, which ensures that the impurities are fully dissolved and eliminates the matrix effect;

[0028] (3) In the test method of the present invention, the impurities are concentrated by evaporating the test solution to a small volume and then centrifuging / sedimenting, so that the quantitation limit of the 14 rare earth elements is lower than 0.005 mg / kg;

[0029] (4) In the test method of the present invention, mass spectrometry interference during the measurement process is eliminated by separating the tungsten matrix and selecting appropriate isotope mass numbers;

[0030] Furthermore, the method for determining trace rare earth elements in high-purity tungsten trioxide according to the present invention solves the problem of accurate quantitative analysis of 14 trace rare earth impurities in high-purity tungsten trioxide. Simultaneously, the rapid preparation of quality control samples for rare earth component analysis in tungsten trioxide according to the present invention also solves the problem of the lack of quality control samples with the same matrix. Moreover, this determination method is simple and easy to perform. Through precipitation separation and impurity concentration, it can effectively eliminate matrix effects and provide a method limit of quantitation that meets product testing requirements. With the assistance of quality control sample monitoring, it ultimately ensures accurate and efficient determination of the content of 14 trace rare earth elements in high-purity tungsten trioxide. Attached Figure Description

[0031] Figure 1 The working curve of praseodymium (Pr) in the embodiment

[0032] Figure 2 The working curve of terbium (Tb) in the embodiment. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] S1. Preparation of quality control samples for rare earth element composition analysis of tungsten trioxide: Accurately weigh 0.7930 g of high-purity tungsten powder and place it in a platinum crucible. Add 10 mL to 15 mL of hydrogen peroxide in 3 to 4 portions. After the vigorous reaction stops, heat on a hot plate until completely dissolved. Add 0.20 mL of a mixed standard solution of rare earth elements, each with a mass concentration of 10 μg / mL. Heat on a hot plate at 180°C to evaporate the liquid to dryness, then raise the temperature to 250°C and continue heating for 20 min. Remove from the heat. Place the platinum crucible in a muffle furnace. Using the temperature control program of the muffle furnace, slowly raise the temperature from room temperature to 600°C over 1 hour, and hold at this temperature for 1 hour until completely transformed into a yellow color. After cooling, remove the crucible and grind it in an agate mortar for 20 to 30 min.

[0035] S2. Accurately weigh 0.10g of high-purity tungsten trioxide sample and place it in a 50mL beaker. Perform a blank test along with the sample.

[0036] S3. Digest the high-purity tungsten trioxide sample. Add 3 mL of deionized water to the beaker from the previous step to moisten it, then add 1 mL of hydrogen peroxide and 3 mL of ammonia. Cover with a watch glass and heat on a hot plate at 220°C for approximately 20 minutes. When most of the sample has dissolved and the color has changed from yellow to white, add 2 mL of ammonia and continue heating until the sample is completely dissolved. Remove the watch glass and continue heating, evaporating the sample solution to approximately 2 mL.

[0037] S4. Precipitate the tungsten matrix. Remove the concentrated sample solution from step 1.3, cool it, and add 1 mL of nitric acid. Shaking the beaker will produce a white precipitate. Place the beaker on a hot plate at 220°C for approximately 5 minutes; the precipitate will change from white to yellow. Transfer the mixture from the beaker to a 10 mL centrifuge tube using deionized water and let it stand overnight or centrifuge at 4000 r / min for 5 minutes. Transfer the supernatant for analysis.

[0038] S5. The tungsten trioxide rare earth component analysis obtained in step S1 is processed using the quality control sample according to the processing methods of S2, S3 and S4. The supernatant is diluted 10 times before analysis.

[0039] S6. By progressively diluting the 100 μg / mL elemental standard storage solution, mixed standard solutions of 14 rare earth elements with mass concentrations of 0, 2 ng / mL, 4 ng / mL, 6 ng / mL, and 8 ng / mL, and a Cs internal standard solution with a mass concentration of 100 ng / mL were prepared, with 1% nitric acid as the medium.

[0040] S7. On the inductively coupled plasma mass spectrometer (ICP-MS), the internal standard solution was introduced through a three-way valve. The ICP-MS measurement conditions were as follows: RF generator power 1550W, sampling depth 8.0mm, nebulizer gas 0.6L / min, dilution gas 0.5L / min, Omega deflection voltage -80V, quadrupole mass gain 125, kinetic discrimination 4.1mV, quadrupole deflection voltage -3.0V, and peristaltic pump speed 0.1rps. The selection of isotope mass numbers is shown in Table 1.

[0041] Table 1 Selection of Isotope Mass Number

[0042]

[0043] On the mass spectrometer, the standard solution prepared by S6 and the Cs internal standard solution were introduced into the injection system through a three-way connector. The signal intensity was monitored, and the working curve for the rare earth elements in step 14 was plotted using the standard curve method. Additionally, the signal intensity of each rare earth element in the blank solution was measured 11 times consecutively, and its standard deviation was calculated. The limit of quantitation (LOQ) was calculated based on the concentration corresponding to 10 times the standard deviation. The linear equation, linear correlation coefficient, and LOQ of the working curve obtained at this time are shown in Table 2. From the LOQ data obtained in Table 2, it can be seen that, compared with product requirements, the LOQ of this method can meet the testing requirements for the content of 14 rare earth elements in 4N~6N high-purity tungsten trioxide products. Furthermore, working curves are given for praseodymium (Pr) and terbium (Tb) as examples; see [link to table]. Figure 1 and Figure 2 Other elements are not listed individually. From Figure 1 and 2As can be seen from Table 2, the linear correlation coefficients of the working curves for the standard solutions of praseodymium (Pr) and terbium (Tb) are all not less than 0.999. Table 2 also shows that the linear correlation coefficients of the obtained working curves are all not less than 0.999.

[0044] Table 2 Linearity and Limits of Quantitation of the Working Curve

[0045]

[0046] S8. On the mass spectrometer, under the same determination conditions as the standard solution prepared in S6, the supernatant of the tungsten trioxide sample from step S4 (or a 10-fold dilution of the supernatant of the quality control sample for rare earth component analysis of tungsten trioxide in step S5) and the Cs internal standard solution are introduced into the injection system through a three-way connector. The signal intensity is monitored, and the mass concentration of each impurity element in tungsten trioxide is calculated according to the working curve method. Then, the mass fraction of each rare earth element is calculated based on the relationship between the obtained mass concentration of the impurity element, the volume of the solution, and the weight of the sample. The recovery rate is calculated by comparing the measured value of the quality control sample with the theoretical value. The results are shown in Table 3.

[0047] Table 3. Results of high-purity tungsten trioxide determination and quality control status.

[0048]

[0049] As shown in Table 2, the linear correlation coefficients of the working curves obtained by this invention are all not less than 0.999, and the limit of quantitation is 0.0029*10. -4 For products with a percentage below 0.005%, the requirement is also 0.005*10. -4 / %, which demonstrates that the test method according to the present invention, namely, by separating and concentrating impurities through precipitation, can effectively eliminate matrix effects and meet product testing requirements.

[0050] As shown in Table 3, the recovery rate of the elements in the quality control samples calculated by this invention is 93%~104%, which is a satisfactory result in the field. Furthermore, a comparison of the measured mass concentrations of the quality control samples used for rare earth element analysis in Table 3 with the theoretical values ​​shows that, within a certain error range, they can be used for sample calibration. In other words, the testing method of this invention can assist in the monitoring of quality control samples, solving the problem of the lack of quality control samples with the same matrix, and also ensuring the accurate and efficient determination of the content of 14 ultra-trace rare earth elements in high-purity tungsten trioxide.

[0051] In summary, the above embodiments demonstrate that the present invention achieves the beneficial effect of simultaneously determining 14 ultra-trace rare earth impurities by using precipitated high-purity tungsten trioxide as the tungsten matrix, concentrating rare earth impurities, and optimizing inductively coupled plasma mass spectrometry (ICP-MS) measurement conditions. The accuracy of the measurement method is further verified by a rapid preparation of quality control samples for tungsten trioxide rare earth component analysis.

Claims

1. A method for determining the content of ultra-trace rare earth elements in high-purity tungsten trioxide, characterized in that, Includes the following steps: S1. Using high-purity tungsten powder as raw material, rapidly prepare quality control samples for rare earth component analysis of tungsten trioxide; S2. Accurately weigh the high-purity tungsten trioxide sample, place it in a beaker, and perform a blank experiment accordingly. S3. Add appropriate proportions of ammonia and hydrogen peroxide to the beaker in step S2, heat to dissolve the sample, and then concentrate it to a small volume. S4. Precipitate the tungsten matrix in the concentrated solution obtained in step S3, and heat it on a hot plate until the precipitate changes color. Transfer it to a 10 mL centrifuge tube and let it stand overnight or centrifuge to obtain the analytical solution. S5. Following the processing methods of steps S2, S3 and S4, digest the quality control sample for rare earth component analysis of tungsten trioxide prepared in step S1, and dilute the supernatant 10 times for testing. S6. Prepare mixed standard solutions of 14 rare earth elements with mass concentrations of 0 ng / mL, 2 ng / mL, 4 ng / mL, 6 ng / mL and 8 ng / mL, and prepare a Cs solution with a mass concentration of 100 ng / mL as an internal standard solution. The medium is 2% nitric acid. S7. On an inductively coupled plasma mass spectrometer, an internal standard solution is introduced through a three-way valve, and the series of standard solutions prepared in S6 and the analytical solution obtained in S4 are measured sequentially. The ratio of the signal intensity of the analyte to the internal standard element in the analytical solution is plotted on the ordinate, and the mass concentration of the analyte is plotted on the abscissa. The linear correlation coefficient of the working curve is not less than 0.999, and the mass concentration of the 14 rare earth elements is calculated according to the corresponding working curve. S8. Calculate the mass fraction of rare earth elements in high-purity tungsten trioxide based on the mass concentration of the element to be analyzed in the test solution, the volume of the test solution, and the sample weight, and calculate the recovery rate based on the theoretical and actual measured values ​​of rare earth elements in the quality control sample.

2. The determination method according to claim 1, characterized in that, The preparation steps for the quality control sample used in step S1 for the rare earth element analysis of tungsten trioxide are as follows: (1) Accurately weigh high-purity tungsten powder and place it in a platinum crucible. Add 10 mL to 15 mL of hydrogen peroxide in 3 to 4 portions. After the violent reaction stops, heat it on a hot plate until it is completely dissolved. (2) After the high-purity tungsten powder in step (1) has completely dissolved, add 0.20 mL of a mixed standard solution of rare earth elements with a mass concentration of 10 μg / mL for each impurity element to the platinum crucible, heat it on a 180°C hot plate to evaporate the liquid, and then raise it to 250°C and continue heating for 20 min to fully evaporate the salts. (3) After the salts are fully evaporated, place the platinum crucible from step (2) in a muffle furnace at room temperature. The temperature control program slowly raises the temperature from room temperature to 600°C within 1 hour, and then keeps it at that temperature for 1 hour until it is completely turned yellow. (4) After the crucible in step (3) is cooled down, it is taken out and then ground in an agate mortar for 20 min to 30 min to ensure the uniformity of the quality control sample; thus, the quality control sample is obtained.

3. The determination method according to claim 1, characterized in that, In step S3, high-purity tungsten trioxide is moistened with 3 mL of deionized water, and then ammonia is added in two portions. The first time, 3 mL of ammonia is added, and the mixture is heated at 220°C for about 20 minutes until most of the sample dissolves and turns from yellow to white. The second time, 2 mL of ammonia is added, and the mixture is heated until the sample is completely dissolved. The watch glass is removed, and the mixture is heated again. The sample solution is then evaporated to a small volume, thus completing the digestion of the high-purity tungsten trioxide sample.

4. The determination method according to claim 1, characterized in that, The tungsten matrix precipitation step S4 is as follows: The digested sample solution from step S3 is removed and cooled, 1 mL of nitric acid is added, and a white precipitate appears when the beaker is shaken. Then, it is heated on a hot plate at 220°C for about 5 minutes, and the precipitate changes from white to yellow. The mixture in the beaker is then transferred to a 10 mL centrifuge tube with deionized water and left to stand overnight or centrifuged at 4000 r / min for 5 minutes to obtain the supernatant as the analytical solution.

5. The determination method according to claim 1, characterized in that, In step S6, the 14 rare earth elements include lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

6. The determination method according to claim 1, characterized in that, In step S7, when establishing the determination method on the inductively coupled plasma mass spectrometer, it is necessary to optimize the instrument parameters and select the optimal isotopic mass number for the analyte to eliminate mass spectrometry interference and reduce the method's limit of quantitation.

7. The determination method according to claim 6, characterized in that, The optimized instrument parameters are the RF generator power, sampling depth, and lens parameters optimized to obtain the best sensitivity.

8. The determination method according to claim 6, characterized in that, Using the series of standard solutions prepared in step S6, a working curve is plotted under selected conditions. After the linearity of the working curve meets the requirements, 11 consecutive measurements of the blank solution are required. Then, the limit of quantitation of the method is calculated, thereby determining which grades of high-purity tungsten trioxide can be tested for rare earth element content.

9. The determination method according to claim 1, characterized in that, In step S8, the mass concentration of the element to be tested is obtained based on the working curve in step S7. The mass fraction of rare earth elements in high-purity tungsten trioxide and the recovery rate of the quality control sample are calculated by combining the test liquid volume, sample weight and spiking amount. A recovery rate of 90% to 110% is considered a satisfactory result.

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