Method for determining content of trace holmium, thulium and tungsten in rare earth erbium and compound thereof

Abstract

The invention discloses a method for determining the content of trace holmium, thulium and tungsten in rare earth erbium and a compound thereof, which comprises the following steps: placing a rare earth erbium and compound sample thereof in a beaker, and performing a blank test along with a sample; adding nitric acid, heating at low temperature until the sample is completely dissolved, and cooling; transferring into a volumetric flask, adding a cesium internal standard solution, diluting with water, and uniformly mixing; the holmium, the thulium and the tungsten are measured by using an oxygen mode of an inductively coupled plasma tandem mass spectrometer, and the contents of the holmium, the thulium and the tungsten are calculated according to a working curve method. According to the method, the inductively coupled plasma tandem mass spectrometry technology is used, and mass spectrum interference of an erbium matrix on holmium, thulium and tungsten is effectively eliminated by selecting a proper reaction mode and optimizing the flow of reaction gas.

Description

Technical Field

[0001] This invention relates to the field of materials testing technology, and more specifically, to a method for determining the content of trace holmium, thulium, and tungsten in rare earth erbium and its compounds. Background Technology

[0002] Rare earth elements (REEs) are widely used in various high-tech fields. Praseodymium, neodymium, samarium, and dysprosium are commonly used in high-power permanent magnets; ytterbium, erbium, and holmium are commonly used in lasers; and lanthanum, gadolinium, terbium, and europium are components of luminescent and fluorescent materials, commonly used in fluorescent lamps, radar screens, and plasma displays. Rare earth elements are also used in automotive exhaust absorption catalysts and high-tech glass.

[0003] Due to the similarity of rare earth elements' properties, the detection of other rare earth impurities in high-purity rare earths is extremely difficult. Currently, the analysis of other rare earth impurities in rare earth oxides mainly employs inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). In ICP-OES analysis, the dense spectral lines of rare earth elements cause severe interference with the spectral lines of impurity elements, generally limiting its application to products with a purity below 99.9%, which is insufficient for products requiring higher purity. Compared to ICP-OES, ICP-MS has been widely used in the analysis of high-purity rare earth products in recent years due to its lower detection limit, but it still suffers from matrix mass spectrum overlap interference, making it unable to directly determine rare earth products with a purity above 99.999%. In high-purity rare earth analysis, for elements with severe interference, the current common practice is to separate the matrix. The separation of trace rare earth analytes from the rare earth matrix can be achieved using chelating resins for online or offline matrix removal, or by applying matrix interference coefficient correction. However, this technique is very time-consuming and requires customized sample pretreatment and analytical methods based on the matrix elements being separated. The steps are cumbersome, and many factors influence the results. This patent uses triple tandem inductively coupled plasma mass spectrometry (ICP-MS / MS) to directly determine the content of trace holmium, thulium, and tungsten in erbium and its compounds. Compared to conventional quadrupole ICP-MS (or ICP-QMS), ICP-MS / MS adds a main quadrupole mass filter (Q1) before the octupole reaction cell system (ORS3) and the quadrupole mass filter (Q2). Q1, as a mass filter, only allows ions with the target analyte mass number to enter the reaction cell, thus excluding all other ions with different mass numbers. Because Q1 eliminates matrix ions and other ions in the plasma, the reaction process in ORS3 can be precisely controlled, allowing for direct and accurate determination of samples with complex matrix interferences without separation. This paper utilizes the dual quadrupole mass filter feature of ICP-MS / MS and its target ion scanning function to study the interference of holmium, thulium, and tungsten in the erbium matrix. Furthermore, using an octupole reaction cell system, different reaction modes (such as NH3, O2, H2, and He) and varying reaction gas flow rates were optimized to directly determine the content of trace holmium, thulium, and tungsten in rare earth erbium and its compounds. Summary of the Invention

[0004] 1. Technical problems to be solved The purpose of this invention is to provide a method for determining the content of trace holmium, thulium, and tungsten in rare earth erbium and its compounds, so as to solve the problems mentioned in the background art.

[0005] 2. Technical Solution A method for determining trace amounts of holmium, thulium, and tungsten in rare earth erbium and its compounds, comprising the following steps: Place rare earth erbium and its compound samples in a beaker and perform a blank test along with the sample; Add nitric acid, heat at low temperature until the sample is completely dissolved, and then cool. Transfer to a volumetric flask, add cesium internal standard solution, dilute with water and mix well; Holmium, thulium, and tungsten were determined using oxygen mode of an inductively coupled plasma tandem mass spectrometer, and their contents were calculated using the working curve method. Preferred parameters for the inductively coupled plasma tandem mass spectrometer are as follows: sampling depth: 9.0 mm, nebulizer gas flow rate: 0.9 L / min, dilution gas flow rate: 0.35 L / min, nebulizer temperature: 2.0 °C, measurement method: peak skipping method, and oxygen flow rate: 30%.

[0006] Isotope selection was based on the principle of high abundance and no interference from impurity element isotopes. Recommended mass numbers, determination modes, and internal standard elements for isotopes are shown in the table below:

[0007] Q1 is the mass number of the instrument's first-stage mass spectrometer, and Q2 is the mass number of the instrument's second-stage mass spectrometer.

[0008] 3. Beneficial effects Compared with the prior art, the advantages of this invention are: This invention uses inductively coupled plasma tandem mass spectrometry (ICP-MS) to effectively eliminate the mass spectrometric interference of erbium matrix elements on holmium, thulium, and tungsten by selecting a suitable reaction mode and optimizing the reaction gas flow rate. Attached Figure Description

[0009] Figure 1 In oxygen mode 165 Product ion scan of Ho; Figure 2 A schematic diagram illustrating the principle of determining Ho in rare earth erbium and its compounds using oxygen mode-mass shift. Figure 3 In oxygen mode 169 Product ion scan of Tm; Figure 4 A schematic diagram illustrating the principle of determining Ho in rare earth erbium and its compounds using oxygen mode-mass shift. Figure 5 In oxygen mode 182 Product ion scan of W; Figure 6 A schematic diagram illustrating the principle of determining W in rare earth erbium and its compounds using oxygen mode-mass shift. Figure 7 The effect of O2 flow rate on the signal (165→181); Figure 8 The effect of O2 flow rate on the signal (169→185); Figure 9 The effect of O2 flow rate on the signal (182→214). Detailed Implementation

[0010] Example: A method for determining trace amounts of holmium, thulium, and tungsten in rare earth erbium and its compounds involves digesting the sample with nitric acid, using argon plasma as the ionization source, and determining holmium, thulium, and tungsten in oxygen mode using an inductively coupled plasma mass spectrometer (ICP-MS). The contents of holmium, thulium, and tungsten are then calculated using the working curve method.

[0011] Includes the following steps: 1. Reagents (Unless otherwise specified, only reagents confirmed to be of analytical grade and distilled or deionized water or water of equivalent purity shall be used in the analysis) 1.1 Nitric acid: Up grade.

[0012] 1.2 Standard storage solutions: Holmium, thulium, tungsten, and cesium were stored in single-element standard solutions with valid certificates and a mass concentration of 1000 μg / mL.

[0013] 1.3 Mixed Standard Solutions: Transfer 10.00 mL of each of the holmium, thulium, and tungsten standard stock solutions (1.2) into a 1000 mL volumetric flask, add 50 mL of nitric acid (1.1), dilute to the mark with water, and mix well. Each mL of this solution contains 1 µg of each of holmium, thulium, and tungsten.

[0014] 1.4 Cesium internal standard solution: Transfer 1.00 mL of cesium standard stock solution (1.2) to a 1000 mL volumetric flask, add 50 mL of nitric acid (1.1), dilute to the mark with water, and mix well. This solution contains 1 µg of cesium per mL.

[0015] 2. Instruments 2.1 Inductively coupled plasma tandem mass spectrometer with a mass resolution of not less than (0.8 ± 0.1) amu.

[0016] 2.2 Electronic balance, accurate to 0.0001g.

[0017] 3. Samples Weigh 0.10 g of the sample, accurate to 0.0001 g.

[0018] 4. Preparation of analytical solution

[0019] Place the sample (3) in a 100 mL beaker and perform a blank test along with the sample. Add a small amount of water, add 3.0 mL of nitric acid (1.1), heat at low temperature until the sample is completely dissolved, cool, transfer to a 100 mL volumetric flask, add 1.00 mL of cesium internal standard solution (1.4), dilute with water to the mark, and mix well.

[0020] Preparation of 5 series of standard solutions Transfer 0 mL, 0.10 mL, 0.50 mL, 1.00 mL, 2.00 mL, 5.00 mL, and 10.00 mL of the mixed standard solution (1.3) into a set of 100 mL volumetric flasks, add 1.00 mL of cesium internal standard solution (1.4) to each flask, dilute with water to the mark, and mix well.

[0021] 6. Measurement 6.1 On the inductively coupled plasma tandem mass spectrometer, after the instrument is running stably, under the selected instrument working conditions, use the prepared standard series solution (5) to calibrate the working curve. The correlation coefficient of the working curve of each element should be above 0.999. Otherwise, it is necessary to re-standardize or re-prepare the standard series solution for standardization.

[0022] 6.2 Sequentially measure the blank solution and analytical solution (4). The software automatically processes the data, calculates and outputs the mass concentration of each impurity element in the blank solution and analytical solution.

[0023] 6.7 Calculation of Analysis Results The content of each element is expressed as a mass fraction Wx and calculated according to formula (1):

[0024] In the formula: ρ x —The mass concentration of the element being measured in the sample solution, expressed in nanograms per milliliter (ng / mL). ρ0—mass concentration of the element being measured in the blank solution, in nanograms per milliliter (ng / mL). V — Total volume of the solution, in milliliters (mL); m — the numerical value of the sample mass, in grams (g).

[0025] The verification process for the above scheme includes the following steps: 1. Sample dissolution: Add 3 mL of nitric acid and heat at low temperature to completely dissolve 0.10 g of rare earth erbium and its compounds. After cooling, transfer to a 100 mL volumetric flask, add internal standard, dilute to volume, and shake well. The solution is ready for analysis. The instrument parameters were optimized, and the optimized operating parameters are shown in Table 1.

[0026] Table 1 ICP-MS / MS Operating Parameters

[0027] 2. Mass Spectrometry Interference Analysis Isotopes with high abundance and low mass spectrometry interference are preferentially selected as the isotopes of the analytes. In erbium-based systems, the mass spectrometry interference of Ho, Tm, and W mainly originates from matrix interference, which cannot be effectively eliminated in standard mode or hydrogen mode. A primary mass filter (Q1) is required to screen only target ions and interfering ions into the oxygen or ammonia collision reaction cell. Due to differences in properties, target ions or interfering ions react with the gases in the reaction cell, resulting in differences in mass-to-charge ratios. A secondary mass filter (Q2) is used for further separation. Finally, the target ion product enters the detector for quantitative detection. Different determination modes are selected for different elements based on the mass spectrometry interference, including standard mode tandem, H2 tandem, He tandem, O2 tandem, and NH3 tandem. Product ion scanning is performed in different tandem modes, and the collision / reaction gas flow rate is optimized to obtain the best mass spectrometry interference elimination effect.

[0028] 3. Measurement of Ho, Tm, and W in oxygen mode Inductively coupled plasma tandem mass spectrometry (ICP-MS / MS) features a primary mass filter (Q1), a collision reaction cell (CRC), and a secondary mass filter (Q2). Q1 screening allows only target ions and interfering ions to enter the oxygen or ammonia collision reaction cell. Due to differences in properties, the target ions or interfering ions react with the cell gases, resulting in differences in mass-to-charge ratios. The secondary screening in Q2 achieves separation, and finally, the target ion product enters the detector for quantitative detection.

[0029] 1) Measurement of Ho in oxygen mode Mass spectrometric interferences in rare earth erbium and its compounds, particularly Ho, primarily originate from the hydrides of the erbium matrix. The Ho isotope 165 is affected by the matrix... 164 Er 1 H + Mass spectrometry interference.

[0030] Prepare a 10 ng / mL Ho standard solution, set Q1=165, and perform a full-spectrum scan of the product ions when the gas in the reaction cell is oxygen. See [link to relevant documentation]. Figure 1 .Depend on Figure 1 It can be seen that a strong ion peak appears at m / z=181 when the pool gas is oxygen. Based on the difference in mass number, the product is inferred to be HoO. + The following reactions are occurring in the oxygen reaction tank at this time: Ho + +O2→HoO+ + O This reaction is exothermic, Ho + The ion readily reacts with O2 to form a new product ion HoO. + This avoids interference at the original mass number.

[0031] To verify the effectiveness of ICP-MS / MS in eliminating the interference of Er matrix hydride ions on Ho, product ion scans were performed on blank matrix solutions (1000 μg / mL Er) and sample solutions (1000 μg / mL Er ~ 10 ng / mL Ho) under various reaction modes (O2, NH3). The signal intensity of Ho in the blank matrix solution and sample solution was collected under different modes. To determine the interference under different modes, the background equivalent concentration (BEC) was used as the evaluation criterion. BEC is the ratio of the signal intensity generated by the interfering element at the analyte to the sensitivity of the method; that is, the signal intensity generated by 1000 μg / mL Er solution at the corresponding mass number is equivalent to a certain amount of Ho. The lower the BEC, the less interference the Er matrix causes to the determination of Ho. The results are shown in Table 2.

[0032]

[0033] In the formula: P S I represents the mass concentration of Ho in the sample solution; b Is represents the signal intensity in the blank solution; Is represents the signal intensity in the sample solution.

[0034] Table 2. BEC values ​​measured under different acquisition modes

[0035] In standard mode, 165 The highest BEC was observed in Ho, indicating severe mass spectrometry interference. In H2 and He modes, the BEC decreased but remained relatively high, indicating that these modes failed to completely eliminate interfering ions. In NH3 reaction mode, the BEC decreased to 1.26 ng / mL, indicating that some mass spectrometry interference was eliminated in the NH3 mass transfer mode. In O2 mass transfer mode, the BEC decreased to 0.076 ng / mL, indicating minimal mass spectrometry interference and effective elimination of interfering ions.

[0036] The principle for testing Ho in rare earth erbium and its compounds under oxygen mode is described in [link to relevant documentation]. Figure 2 .

[0037] 2) Measurement of Tm in oxygen mode Mass spectrometric interferences of Tm in rare earth erbium and its compounds also primarily originate from the hydrides of the erbium matrix. The Tm isotope 169 is affected by the matrix... 168 Er1 Mass spectrometry interference of H.

[0038] Prepare a 10 ng / mL Tm standard solution, set Q1=169, and perform a full spectrum scan of the product ions when the gas in the reaction cell is oxygen. See [link to relevant documentation]. Figure 3 .Depend on Figure 3 It can be seen that a strong ion peak appears at m / z=185 when the gas in the reaction tank is oxygen. Based on the difference in mass number, the product is inferred to be TmO. + The following reactions are occurring in the oxygen reaction tank at this time: Tm + +O2→TmO + + O This reaction is exothermic, Tm + The ion readily reacts with O2 to form a new product ion, TmO. + This avoids interference at the original mass number.

[0039] To verify the effectiveness of ICP-MS / MS in eliminating the interference of Er hydride ions on Tm, the signal intensity of Tm in blank matrix solution (1000 μg / mL Er) and sample solution (1000 μg / mL Er ~ 10 ng / mL Tm) was collected under different modes. To determine the interference under different measurement modes, the background equivalent concentration (BEC) was used as the evaluation criterion. BEC is the ratio of the signal intensity generated by the interfering element at the analyte to the sensitivity of the method; that is, the signal intensity generated by 1000 μg / mL Er solution at the corresponding mass number is equivalent to a certain amount of Tm. The lower the BEC, the less interference the Er matrix causes to the determination of Tm. The results are shown in Table 3.

[0040] Table 3. BEC values ​​measured under different acquisition modes

[0041] In standard mode, 169 The highest BEC at Tm indicates severe mass spectrometry interference. While BEC decreased in both H2 and He modes, it remained relatively high, indicating that the He collision mode and H2 reaction mode failed to completely eliminate interfering ions, and significant mass spectrometry interference persisted. In the NH3 reaction mode, BEC decreased to 1.35 ng / mL, indicating that some mass spectrometry interference was eliminated under this mode. When O2 was introduced as the reaction gas, BEC decreased to 0.023 ng / mL, indicating minimal mass spectrometry interference and effective elimination of interfering ions.

[0042] The principle for testing Tm in rare earth erbium and its compounds under oxygen mode is described in [link to relevant documentation]. Figure 4 .

[0043] 3) Measurement of W in oxygen mode Mass spectral interferences in rare earth erbium and its compounds mainly originate from oxides of the Er matrix. Mass numbers 180, 182, 183, 184, and 186 are all affected by Er oxides.

[0044] Prepare a 10 ng / mL W standard solution, set Q1=182, and perform a full-spectrum scan of the product ions when the gas in the reaction cell is oxygen. See [link to relevant documentation]. Figure 5 .Depend on Figure 5 It can be seen that a strong ion peak appears at m / z=214 when the pool gas is oxygen. Based on the difference in mass number, the product is inferred to be WO2. + The following reactions are occurring in the oxygen reaction tank at this time: W + +O2→WO2 + This reaction is exothermic. + The ion readily reacts with O2 to form a new product ion, WO2. + This avoids interference at the original mass number.

[0045] To verify the effectiveness of ICP-MS / MS in eliminating the interference of Er oxide ions in the matrix on W, signal intensities of W in blank matrix solutions (1000 μg / mL Er) and sample solutions (1000 μg / mL Er ~ 10 ng / mL W) were collected under different modes. To determine the interference under different measurement modes, the background equivalent concentration (BEC) was used as the evaluation criterion. BEC is the ratio of the signal intensity generated by the interfering element at the analyte to the sensitivity of the method; that is, the signal intensity generated by 1000 μg / mL Er solution at the corresponding mass number is equivalent to a certain concentration of W. The lower the BEC, the less interference the Er matrix causes to the determination of W. The results are shown in Table 4.

[0046] Table 4. BEC values ​​measured under different acquisition modes

[0047] In standard mode, 182 The highest BEC value for W indicates severe mass spectrometry interference. In H2 and He modes, the BEC values ​​decreased but remained relatively high, indicating that the He collision mode and H2 reaction mode failed to completely eliminate interfering ions. In NH3 mode, the BEC value decreased to 1.77 ng / mL, effectively eliminating most of the mass spectrometry interference. When O2 was introduced as the reaction gas, the BEC value decreased to 0.051 ng / mL, indicating minimal mass spectrometry interference and effective elimination of interfering ions.

[0048] The principle for testing W in rare earth erbium and its compounds under oxygen mode is described in [link to relevant documentation]. Figure 6 .

[0049] 4) Optimization of O2 flow rate The reaction gas flow rate (maximum O2 flow rate of 1.5 mL / min) significantly impacts the effectiveness of interference elimination. Signal intensities were collected for mass pairs 165-181 in the blank matrix solution (1000 μg / mL Er), 169-185 in the sample solution (1000 μg / mL Er ~ 10 ng / mL Ho), and 182-214 in the sample solution (1000 μg / mL Er ~ 10 ng / mL Tm). The results of signal intensity variation with O2 flow rate are shown in [Figure number missing]. Figure 3-8 It can be seen that with the change of O2 flow rate, the signal intensity in the blank solution did not change significantly, while the signal intensity in the sample solution showed a trend of first increasing and then decreasing. When the O2 flow rate was between 20% and 30%, M+ underwent an oxidation reaction to generate a new ion M. 16 O + The reaction tends towards saturation. However, as the O2 flow rate continues to increase to 40%, the excessive flow rate causes collisions between excess O2 and M+ ions in the reaction tank, leading to a decrease in signal intensity. This study selected an O2 flow rate of 30%.

[0050] 4. Isotope selection Prioritize selecting mass numbers of analytes that are free from isotopic interference and have high abundance. When matrix-induced mass spectrometry interference cannot be eliminated, select the oxygen reaction cell mode to eliminate the interference before measurement. A summary of the mass numbers of analytes Q1 and Q2 and the measurement modes is shown in Table 5.

[0051]

[0052] 5. Investigation of matrix effects and internal standard correction When the matrix concentrations were 0.5 mg / mL, 1.0 mg / mL, 2.0 mg / mL, and 3.0 mg / mL, respectively, each analyte was added at a mass concentration of 10 ng / mL, and the signal intensity (in CPS) of the analytes at different matrix concentrations was measured. The results are shown in Table 6. As can be seen from Table 6, the signal intensity of each analyte decreased to varying degrees with increasing matrix concentration, indicating that rare earth erbium and its compound matrix have a significant inhibitory effect on the signal of each analyte (matrix effect).

[0053] When matrix effects are significant, matrix matching and internal standard correction methods can usually be used to improve the accuracy of the determination results. This method uses internal standard correction to correct the determination results. Each analyte with a mass concentration of 10 ng / mL was added to a matrix solution with a mass concentration of 1 mg / mL, followed by the addition of a cesium internal standard solution. The correction effect of the internal standard element on the matrix effect was investigated, and the results are shown in Table 6.

[0054] Table 6. Matrix Effects and Internal Standard Correction Results

[0055] The results in the table above show that the matrix effect is quite significant when ICP-MS / MS is used to determine trace impurity elements in rare earth erbium and its compounds. With the internal standard element correction, the recoveries of each analyte at 10 ng / mL are 99.1% to 106.6%, indicating that the internal standard element Cs can effectively correct the matrix effect and improve the accuracy of the method.

[0056] 6. Plotting the working curve and investigating the detection limit Working curve 1: Transfer 0 mL, 0.10 mL, 0.50 mL, 1.00 mL, 2.00 mL, 5.00 mL, and 10.00 mL of the mixed standard solution into a set of 100 mL volumetric flasks, add 1.00 mL of cesium internal standard solution to each flask, dilute with water to the mark, and mix well.

[0057] Prepare a series of standard solutions according to the above method, and measure the signal intensity of the isotopes of each element to be tested under the selected instrument conditions. Plot the working curve with the mass concentration of each element to be tested as the abscissa and the ratio of the signal intensity of the element to be tested to the internal standard element as the ordinate.

[0058] Using 6N rare earth erbium and its compounds as the research objects, erbium matrix solutions of 1 mg / mL were prepared. Eleven consecutive measurements were performed according to the selected experimental method. The standard deviation of the measurement results was calculated, and the limit of detection (LOD) was defined as three times the standard deviation of the measured signal intensity, and the limit of quantitation (LOQ) was defined as ten times the standard deviation. The linear equations, correlation coefficients, LODs, and LOQs of quantitation for each impurity element are shown in Table 7.

[0059] Table 7. Working curves, limits of detection, and limits of quantification for each analyte.

[0060]

[0061] As shown in the table above, the linear correlation coefficients of the working curves of each element to be measured are all greater than 0.999, indicating that the working curves have good linearity.

[0062] 7. Precision test results Because the collected rare earth erbium and its compound samples contained low levels of impurity elements, precision tests were conducted by spiked synthesis. Specifically, holmium, thulium, and tungsten were added to the rare earth erbium and its compounds at concentrations of 1 μg / g, 10 μg / g, and 40 μg / g, respectively. After weighing the samples, appropriate amounts of the mixed standard solution were added directly to the corresponding beakers for dissolution, resulting in samples 1#, 2#, and 3#. Following the selected experimental method, each analyte element in the three synthesized samples was independently measured seven times. The results are shown in Tables 8-10. The average value and standard deviation of the measurement results were calculated.

[0063] Table 8 Precision test results of synthetic sample #1

[0064] Table 9 Precision test results of synthetic sample #2

[0065] Table 10 Precision test results of synthetic sample #3

[0066] As shown in the table above, the RSD of the precision test results for each element is less than 5%, indicating good precision that meets the application requirements.

[0067] 8. Accuracy test results According to the established experimental method, spiked recovery tests were carried out on Ho, Tm and W in rare earth erbium and its compounds to verify the correctness of the method. The results are shown in Tables 11 to 13.

[0068] Table 11 Recovery rates at low concentrations

[0069] Table 12 Recovery rates of medium concentration spikes

[0070] Table 13 High Concentration Spike Recovery Rate

[0071] The results in Tables 11-13 show that the recoveries of the three elements were 96.00%–112.00%, indicating good accuracy and meeting the detection requirements. In summary, an ICP-MS / MS method was established for the determination of trace holmium, thulium, and tungsten in rare earth elements and their compounds. The mechanism of each mode in QQQ for eliminating mass spectrometry interference was studied. The QQQ-O2 mode can eliminate the mass spectrometry interference of Er oxide ions and hydride ions on Ho, Tm, and W. The relative standard deviation of this method is <5.0%, indicating good precision. The sample spike recoveries are between 96.0% and 112.0%, demonstrating accurate results.

[0072] Although examples of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for determining trace amounts of holmium, thulium, and tungsten in rare earth erbium and its compounds, characterized in that: Includes the following steps: Place rare earth erbium and its compound samples in a beaker and perform a blank test along with the sample; Add nitric acid, heat at low temperature until the sample is completely dissolved, and then cool. Transfer to a volumetric flask, add cesium internal standard solution, dilute with water and mix well; Holmium, thulium, and tungsten were determined using oxygen mode of an inductively coupled plasma mass spectrometer, and their contents were calculated using the working curve method.

2. The method for directly determining the trace amounts of holmium, thulium, and tungsten in rare earth erbium and its compounds according to claim 1, characterized in that: Parameter selection for inductively coupled plasma tandem mass spectrometry: sampling depth: 8.0~9.0 mm, nebulizer gas flow rate: 0.9~1.0 L / min, dilution gas flow rate: 0.35~0.40 L / min, nebulizer temperature: 2.0℃, oxygen flow rate: 25~40%.

3. The method for determining trace amounts of holmium, thulium, and tungsten in rare earth erbium and its compounds according to claim 2, characterized in that: Isotope selection was based on the principle of high abundance and no interference from impurity element isotopes. Recommended mass numbers, determination modes, and internal standard elements for isotopes are shown in the table below: Q1 is the mass number of the instrument's first-stage mass spectrometer, and Q2 is the mass number of the instrument's second-stage mass spectrometer.

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