Method for accurately determining impurity elements in rhodium powder by removing interference of rhodium matrix

Abstract

The application provides a method for accurately determining impurity elements in rhodium powder by removing rhodium matrix interference, and belongs to the field of analysis and detection. The application takes several equal amounts of rhodium powder samples, respectively prepares sample solutions, and respectively establishes calibration curves containing rhodium matrix and calibration curves without rhodium matrix based on an inductively coupled plasma atomic emission spectrometer by using an improved standard addition method, so as to respectively determine the content of impurity elements in a to-be-tested sample solution and a to-be-tested blank solution, and then the content of impurity elements in the rhodium powder can be obtained by calculation. The method not only eliminates the interference of rhodium in the matrix on the determination of the content of impurity elements, but also eliminates the systematic error caused by the deviation of the determination result of impurity elements in the blank solution, effectively ensures the accuracy of the test result, and has the advantages of simple operation process, saved test time, and avoided problems such as poor reproducibility and poor stability of the test result.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of analytical detection, and particularly relates to a method for accurately determining impurity elements in rhodium powder by removing rhodium matrix interference. BACKGROUND

[0002] Rhodium belongs to platinum group metals and is mainly used for catalysts and corrosion-resistant materials for scientific instruments, and is commonly used as an electroplating layer in the electronic industry and jewelry processing industry. At present, rhodium is mainly used as a car exhaust catalyst in the automobile industry, and the automobile manufacturing industry is the largest user of rhodium. With the continuous development of fuel cells and the gradual maturity of fuel cell automobile technology, the use of rhodium in the automobile industry will further increase, and the purity thereof will directly affect the performance of the product. Therefore, it is crucial to accurately determine the impurity content in rhodium powder and then calculate the purity data of the rhodium powder.

[0003] At present, the commonly used methods for detecting impurities in rhodium powder include inductively coupled plasma atomic emission spectrometry (ICP-AES) and glow discharge mass spectrometry (GD-MS). Jiang Danping et al. published an article entitled "Comparison of Two Different Methods for Determining Impurity Element Content in Rhodium Powder" in Measurement Technology, Vol. 40, No. 6, 2020, which detailed the above two methods for detecting impurities in rhodium powder and compared them, reflecting the superiority of the ICP-AES detection method. When determining impurity elements in rhodium powder based on ICP-AES, a working curve is formed according to a rhodium-free matrix standard solution, and then the working curve is used to determine the impurity concentration in the rhodium sample solution. However, since the rhodium matrix will seriously interfere with the determination of impurity elements, the test results will be inaccurate. Therefore, it is necessary to eliminate the interference of the rhodium matrix to improve the accuracy of the test results.

[0004] Generally, the matrix interference can be eliminated by matching the pure matrix. For example, the patent with publication number CN110231333A provides a method for determining impurity elements in aluminum oxide, which uses high-purity aluminum to prepare an aluminum matrix standard solution, and then uses the aluminum matrix standard solution and other impurity element standard solutions as a series of standard solutions, and draws a working curve of the series of standard solutions to eliminate the interference of the aluminum matrix. However, if this method is applied to the determination of impurities in rhodium powder, high-purity rhodium needs to be consumed for matching, and high-purity rhodium is rare and expensive, which greatly increases the experimental cost and limits the application of the rhodium powder detection method.

[0005] In addition, the standard addition method can also be used to eliminate the matrix interference. However, the conventional standard addition method is to dissolve a large sample, dilute and then take an equal amount of solution for testing. In this way, the impurities in the blank solution are difficult to detect after dilution, so the blank solution is generally not determined. However, since rhodium is chemically inert, it is extremely difficult to dissolve a large sample, and it is difficult to obtain high-purity rhodium powder for dilution in actual application, so this conventional standard addition method is not suitable for the detection of rhodium powder. Moreover, if there is a certain concentration of impurities in the blank solution, not determining it will lead to inaccurate test results and systematic errors. Therefore, how to eliminate the rhodium matrix interference while eliminating the systematic error of impurity elements is a big problem in the determination of impurity elements in rhodium powder by ICP-AES.

[0006] Therefore, it is necessary to design an improved method for accurately determining impurity elements in rhodium powder by removing rhodium matrix interference to solve the above problems. SUMMARY

[0007] The purpose of the present application is to provide a method for accurately determining impurity elements in rhodium powder by removing rhodium matrix interference, which can eliminate the interference of rhodium matrix on the determination of impurity elements and eliminate the systematic error of impurity elements in the blank solution, effectively guarantee the accuracy of test results, and make up for the shortcomings of the existing detection method.

[0008] To achieve the above-mentioned purpose of the application, the present application provides a method for accurately determining impurity elements in rhodium powder by removing rhodium matrix interference, comprising the following steps:

[0009] S1. A plurality of equal amounts of rhodium powder samples are weighed, and each of the rhodium powder samples is sequentially subjected to microwave digestion treatment and heating concentration treatment to obtain a plurality of sample solutions;

[0010] S2. The blank sample is sequentially subjected to the microwave digestion treatment and the heating concentration treatment in the same way as in step S1 to obtain a blank solution;

[0011] S3. At least one of the sample solutions is made constant volume as a to-be-tested sample solution; different amounts of mixed standard solution containing to-be-tested impurity elements are added to at least three of the sample solutions, and the constant volume is used as a standard solution containing rhodium matrix;

[0012] S4. The to-be-tested sample solution and the standard solution containing rhodium matrix are detected by an inductively coupled plasma atomic emission spectrometer, a calibration curve containing rhodium matrix is established according to the detection results, and the concentration of impurity elements in the to-be-tested sample solution is calculated according to the calibration curve containing rhodium matrix;

[0013] S5. Add different amounts of the mixed standard solution to the volumetric flask, then add hydrochloric acid solution, and dilute to volume to obtain the rhodium-free matrix standard solution; dilute the blank solution to volume to obtain the blank solution to be tested.

[0014] S6. The standard solution of the rhodium-free matrix and the blank solution to be tested are detected by inductively coupled plasma atomic emission spectrometry. A calibration curve of the rhodium-free matrix is ​​established based on the detection results, and the concentration of impurity elements in the blank solution to be tested is calculated based on the calibration curve of the rhodium-free matrix.

[0015] S7. Calculate the content of impurity elements in the rhodium powder sample based on the concentration of impurity elements in the sample solution to be tested and the concentration of impurity elements in the blank solution to be tested.

[0016] As a further improvement of the present invention, the microwave digestion process includes the following steps:

[0017] The rhodium powder sample was placed in a microwave digestion vessel, and hydrochloric acid solution and hydrogen peroxide solution were added to the microwave digestion vessel. The vessel was then heated in a digestion apparatus.

[0018] As a further improvement of the present invention, in step S1, the mass of each rhodium powder sample is 0.0995 to 0.1005 g; the density of the hydrochloric acid solution added to the microwave digestion vessel is 1.19 g / mL, and the amount added is 9 to 15 mL; the volume fraction of the hydrogen peroxide solution is 30%, and the amount added is 3 to 5 mL.

[0019] As a further improvement of the present invention, during the microwave digestion process, the temperature of the food placed in the digester for heating is 240-260°C, and the heating time is 1-2 hours.

[0020] As a further improvement of the present invention, the temperature of the heating concentration treatment is 180-220°C, and both the sample solution and the blank solution are concentrated to 0.8-1.2 mL.

[0021] As a further improvement of the present invention, in step S3, the mixed standard solution contains one or more of the following metallic impurities:

[0022] Platinum, iridium, ruthenium, aluminum, iron, silicon, magnesium, silver, palladium, gold, lead, copper, zinc, nickel, cadmium, cobalt, antimony, zirconium, tellurium;

[0023] The concentration of each metal impurity in the mixed standard solution is 5–15 μg / mL.

[0024] As a further improvement of the present invention, in step S3, the method for preparing the standard solution containing the rhodium matrix includes: adding 0.5 mL, 1 mL, and 2 mL of the mixed standard solution to three portions of the sample solution respectively, and making up the volume to obtain the standard solution containing the rhodium matrix.

[0025] As a further improvement of the present invention, in step S5, the method for preparing the standard solution of the rhodium-free matrix includes: adding 0 mL, 0.5 mL, 1 mL and 2 mL of the mixed standard solution to four volumetric flasks respectively, then adding hydrochloric acid solution, and making up to volume to obtain the standard solution of the rhodium-free matrix.

[0026] As a further improvement of the present invention, in step S5, the density of the hydrochloric acid solution is 1.19 g / mL, and the amount added is 0.8 to 1.2 mL.

[0027] As a further improvement of the present invention, in step S7, the formula for calculating the content of impurity elements in the rhodium powder sample is as follows:

[0028]

[0029] Where, ω i The mass fraction of impurity element i in the rhodium powder sample is expressed as a percentage; i represents one of platinum, iridium, ruthenium, aluminum, iron, silicon, magnesium, silver, palladium, gold, lead, copper, zinc, nickel, cadmium, cobalt, antimony, zirconium, and tellurium.

[0030] C i The concentration of impurity element i in the sample solution to be tested is expressed in micrograms per milliliter.

[0031] C bi The concentration of impurity element i in the blank solution to be tested is expressed in micrograms per milliliter.

[0032] V represents the volume of the sample solution to be tested, in milliliters;

[0033] m represents the mass of the rhodium powder sample, in grams.

[0034] The beneficial effects of this invention are:

[0035] 1. The present invention provides a method for accurately determining impurity elements in rhodium powder by removing interference from the rhodium matrix. Several equal amounts of rhodium powder samples are weighed and prepared into sample solutions. Then, using inductively coupled plasma atomic emission spectrometry (ICP-AES), calibration curves are established for both the rhodium-containing and rhodium-free matrices using the standard addition method. These curves are used to determine the content of impurity elements in the sample solutions and blank solutions, respectively. The accurate content of impurity elements in the rhodium powder is then calculated. This method not only eliminates the interference of rhodium in the matrix on the determination of impurity element content but also eliminates the systematic error caused by deviations in the determination results of impurity elements in the blank solution, effectively ensuring the accuracy of the test results. Furthermore, this method is simple to operate and saves testing time.

[0036] 2. This invention establishes a calibration curve for a rhodium-containing matrix by adding different amounts of mixed standard solution to the sample solution. The impurity content in the test solution is calculated using this calibration curve, eliminating the interference of rhodium in the matrix on the determination results of other impurity elements. This method not only reduces testing costs but also ensures testing accuracy. Furthermore, using a rhodium-containing matrix calibration curve allows for the continuous determination of multiple rhodium powder samples, saving testing time.

[0037] 3. This invention improves upon the conventional standard addition method, making it applicable to the determination of impurity elements in rhodium powder. Specifically, this invention directly weighs multiple identical and small samples (approximately 0.1000 g each) and then performs microwave digestion on each sample separately. This ensures complete dissolution of each sample, avoiding the difficulty in dissolving rhodium powder when dissolving a larger sample (approximately 1 g) in the conventional standard addition method, and saving testing costs. Furthermore, this invention establishes a calibration curve for a rhodium-free matrix for the first time using the standard addition method. This calibration curve is then used to determine the impurity content in the blank solution, accurately measuring the impurity element content in the blank sample, eliminating systematic errors, and completely eliminating matrix interference, resulting in more accurate test results. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to specific embodiments.

[0039] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0040] This invention provides a method for accurately determining impurity elements in rhodium powder after removing interference from the rhodium matrix, comprising the following steps:

[0041] S1. Weigh out several equal portions of rhodium powder samples, and sequentially perform microwave digestion and heating concentration on each portion of the rhodium powder sample to obtain several sample solutions.

[0042] S2. Following the same procedure as in step S1, the blank sample is subjected to the microwave digestion treatment and the heating concentration treatment sequentially to obtain a blank solution;

[0043] S3. After diluting at least one of the sample solutions to a final volume, use it as the sample solution to be tested; add different amounts of mixed standard solution to at least three of the sample solutions, and dilute to a final volume to use them as standard solutions containing a rhodium matrix; the mixed standard solution contains the impurity element to be tested;

[0044] S4. The test sample solution and the standard solution containing the rhodium matrix are detected by inductively coupled plasma atomic emission spectrometry. A calibration curve for the rhodium matrix is ​​established based on the detection results, and the concentration of impurity elements in the test sample solution is calculated based on the calibration curve of the rhodium matrix.

[0045] S5. Add different amounts of the mixed standard solution to the volumetric flask, then add hydrochloric acid solution, and dilute to volume to obtain the rhodium-free matrix standard solution; dilute the blank solution to volume to obtain the blank solution to be tested.

[0046] S6. The standard solution of the rhodium-free matrix and the blank solution to be tested are detected by inductively coupled plasma atomic emission spectrometry. A calibration curve of the rhodium-free matrix is ​​established based on the detection results, and the concentration of impurity elements in the blank solution to be tested is calculated based on the calibration curve of the rhodium-free matrix.

[0047] S7. Calculate the content of impurity elements in the rhodium powder sample based on the concentration of impurity elements in the sample solution to be tested and the concentration of impurity elements in the blank solution to be tested.

[0048] Through the above method, the present invention can simultaneously eliminate the interference of the rhodium matrix on the impurity content in the test sample solution and the blank solution, and accurately measure the impurity element content in rhodium powder in a simpler way.

[0049] Preferably, in step S1, the microwave digestion process includes the following steps: placing the rhodium powder sample in a microwave digestion vessel, adding 9-15 mL of hydrochloric acid solution with a density of 1.19 g / mL and 3-5 mL of hydrogen peroxide solution with a volume fraction of 30% to the microwave digestion vessel containing the rhodium powder sample, placing it in a digestion apparatus, heating to 240-260°C, and heating for 1-2 hours. Preferably, the number of rhodium powder samples is five portions, each with an equal mass, all within the range of 0.0995-0.1005 g.

[0050] The above method enables rhodium powder to dissolve quickly and completely, greatly shortening the heating time and reducing the amount of rhodium powder used, thus saving testing costs.

[0051] In step S1, the preferred temperature for the heating and concentration process is 180–220°C, and the sample solution is concentrated to 0.8–1.2 mL.

[0052] The microwave digestion and heating concentration processes in step S2 are exactly the same as those in step S1. The only difference is that no rhodium powder sample is added in step S2 for use as a blank control.

[0053] In step S3, it is preferable to dilute the two sample solutions to the required volume and use them as the test sample solutions in order to improve the accuracy of the detection results by averaging them. At the same time, it is preferable to add 0.5 mL, 1 mL and 2 mL of mixed standard solution to the three sample solutions respectively in order to obtain the calibration curve of the rhodium-containing matrix more accurately.

[0054] The mixed standard solution contains one or more of the following metallic impurities:

[0055] Platinum, iridium, ruthenium, aluminum, iron, silicon, magnesium, silver, palladium, gold, lead, copper, zinc, nickel, cadmium, cobalt, antimony, zirconium, tellurium;

[0056] The concentration of each metal impurity in the mixed standard solution is preferably 5–15 μg / mL.

[0057] In step S5, preferably, 0 mL, 0.5 mL, 1 mL, and 2 mL of the mixed standard solution are added to four volumetric flasks respectively, followed by the addition of hydrochloric acid solution and dilution to volume. The hydrochloric acid solution has a density of 1.19 g / mL, and the preferred amount added is 0.8–1.2 mL.

[0058] In step S7, the formula for calculating the content of impurity elements in the rhodium powder sample is:

[0059]

[0060] Where, ω iThe mass fraction of impurity element i in the rhodium powder sample is expressed as a percentage; i represents one of platinum, iridium, ruthenium, aluminum, iron, silicon, magnesium, silver, palladium, gold, lead, copper, zinc, nickel, cadmium, cobalt, antimony, zirconium, and tellurium.

[0061] C i The concentration of impurity element i in the sample solution to be tested is expressed in micrograms per milliliter.

[0062] C bi The concentration of impurity element i in the blank solution to be tested is expressed in micrograms per milliliter.

[0063] V represents the volume of the sample solution to be tested, in milliliters;

[0064] m represents the mass of the rhodium powder sample, in grams.

[0065] In all the above steps, the volume of the solution after volume adjustment is the same, and it is preferable to use a 10 mL volumetric flask for volume adjustment.

[0066] The present invention will now be described in detail with reference to specific embodiments.

[0067] Example 1

[0068] This embodiment provides a method for accurately determining impurity elements in rhodium powder after removing interference from the rhodium matrix, including the following steps:

[0069] S1. Weigh five rhodium powder samples, each with a mass of 0.1000g, and place them in five microwave digestion vessels. Add 15mL of hydrochloric acid solution (density 1.19g / mL, purity grade superior) and 5mL of hydrogen peroxide solution with a volume concentration of 30% to each microwave digestion vessel containing the rhodium powder sample. Place the vessels in a high-temperature and high-pressure digester, heat to 260℃, and heat for 1h. Then, transfer the digested solution to five polytetrafluoroethylene beakers with water and heat at 180℃ to concentrate to a volume of 1mL to obtain five sample solutions.

[0070] S2. Following the same procedure as in step S1, the two blank samples were subjected to the microwave digestion and heating concentration processes sequentially to obtain two blank solutions, each with a volume of 1 mL.

[0071] S3. Transfer the five sample solutions prepared in step S1 to 10 mL plastic volumetric flasks. Dilute two of the sample solutions to the mark with water and use them as the test sample solutions, denoted as A1 and A2 respectively, with a volume of V. Add 0.5 mL, 1 mL, and 2 mL of mixed standard solution to the other three sample solutions respectively, and dilute to the mark to use them as rhodium-containing matrix standard solutions, denoted as A3, A4, and A5 respectively.

[0072] The mixed standard solution contains metallic impurities: platinum, iridium, ruthenium, aluminum, iron, silicon, magnesium, silver, palladium, gold, lead, copper, zinc, nickel, cadmium, cobalt, antimony, zirconium, and tellurium; and the concentration of each metallic impurity in the mixed standard solution is 10 μg / mL.

[0073] S4. Inductively coupled plasma atomic emission spectrometry (ICP-AES) is used to detect A1, A2, A3, A4, and A5 obtained in step S3, respectively. A calibration curve for the rhodium-containing matrix is ​​established based on the detection results. The concentrations of impurity elements in A1 and A2 are calculated based on the calibration curves of the rhodium-containing matrix, and the average of the two concentrations is denoted as C. i .

[0074] S5. Add 0 mL, 0.5 mL, 1 mL, and 2 mL of mixed standard solution to four 10 mL plastic volumetric flasks, respectively. This mixed standard solution is the same as that used in step S3. Then add 1 mL of hydrochloric acid solution with a density of 1.19 g / mL to each volumetric flask. This hydrochloric acid solution is the same as that used in step S1. Then, dilute to the mark to obtain the rhodium-free standard solution. Dilute the two blank solutions obtained in step S2 to 10 mL and use them as the blank solutions to be tested, labeled B1 and B2, respectively.

[0075] S6. Using inductively coupled plasma atomic emission spectrometry (ICP-AES), the standard solution and blank solutions B1 and B2 of the rhodium-free matrix from step S5 were analyzed. A calibration curve for the rhodium-free matrix was established based on the results. The concentrations of impurity elements in B1 and B2 were calculated based on the calibration curve, and the average concentration was recorded as C. bi .

[0076] S7. Based on the average concentration C of impurity elements in the test sample solutions A1 and A2 obtained in steps S4 and S6. i The average concentration C of impurity elements in blank solutions B1 and B2. bi The content of metallic impurities in the sample to be tested is calculated according to the following formula:

[0077]

[0078] Where, ω i The mass fraction of impurity element i in the rhodium powder sample is expressed as a percentage; i represents one of platinum, iridium, ruthenium, aluminum, iron, silicon, magnesium, silver, palladium, gold, lead, copper, zinc, nickel, cadmium, cobalt, antimony, zirconium, and tellurium.

[0079] C i The concentration of impurity element i in the sample solution to be tested is expressed in micrograms per milliliter.

[0080] C biThe concentration of impurity element i in the blank solution to be tested is expressed in micrograms per milliliter.

[0081] V represents the volume of the sample solution to be tested, in milliliters;

[0082] m represents the mass of the rhodium powder sample, in grams.

[0083] The content of impurity elements in the rhodium powder measured in this embodiment is shown in Table 1.

[0084] Table 1. Content of various impurity elements in rhodium powder measured in Example 1

[0085]

[0086] To verify the accuracy of the above results, a spiked recovery experiment was conducted on the rhodium powder sample of Example 1. Specifically, 0.1000g of the rhodium powder sample from Example 1 was weighed and 0.5mL of the mixed standard solution used in Example 1 was added, so that the amount of each metal impurity added was 5μg. The spiked sample was obtained, and the impurity content in the spiked sample was determined according to the steps in Example 1. The recovery rate was calculated, and the results are shown in Table 2.

[0087] Table 2 Results of the spiked recovery experiment in Example 1

[0088]

[0089] The spiked recovery results in the table above show that the spiked recovery rate is between 96.0% and 104.0%, indicating that the method is accurate and reliable.

[0090] Example 2

[0091] This embodiment provides an accurate method for determining impurity elements in rhodium powder after removing interference from the rhodium matrix. Compared with Example 1, the difference lies in changing the volume, heating temperature, and time of the hydrochloric acid solution and hydrogen peroxide solution added in the microwave digestion process in steps S1 and S2.

[0092] In this embodiment, the amount of hydrochloric acid solution added in step S1 is 9 mL, the amount of hydrogen peroxide solution added is 3 mL, the heating temperature is 240℃, and the heating time is 2 h. Other raw materials and steps are roughly the same as in Example 1, and will not be repeated here. The content of impurity elements in the rhodium powder measured in this embodiment is shown in Table 3.

[0093] Table 3. Content of various impurity elements in rhodium powder measured in Example 2.

[0094]

[0095] To verify the accuracy of the above results, a spiked recovery experiment was conducted on the rhodium powder sample used in this embodiment. The experimental method was the same as that in Example 1, and will not be repeated here. The spiked recovery experiment results of this embodiment are shown in Table 4.

[0096] Table 4. Results of the spiked recovery experiment in Example 2

[0097]

[0098] The spiked recovery results in the table above show that the spiked recovery rate is between 96.0% and 104.0%, indicating that the method is accurate and reliable.

[0099] Comparative Example 1

[0100] This comparative example provides an accurate method for determining impurity elements in rhodium powder after removing interference from the rhodium matrix. Compared to Example 1, the difference lies in that, in step S1, two rhodium powder samples are digested, and steps S3 and S4 are not performed. That is, this comparative example only establishes a calibration curve without a rhodium matrix, and calculates the impurity concentrations in the test sample solution and the test blank solution based on this standard curve without a rhodium matrix. The other steps in this comparative example are largely the same as in Example 1 and will not be repeated here. The rhodium powder sample tested in this comparative example is the same as that used in Example 1, and the test results are shown in Table 5.

[0101] Table 5 Content of various impurity elements in rhodium powder

[0102] Element Platinum Iridium Ruthenium Aluminium Iron Silicon Silver Content (%) 0.0014 0.0854 0.0924 0.0082 0.0114 0.0085 0.0212 Element Gold Copper Nickel Cadmium Antimony Tellurium Palladium Content (%) 0.0056 Not detected 0.0222 Not detected 0.0072 0.0621 Not detected Element Lead Zinc Magnesium Cobalt Zirconium Content (%) 0.0078 0.0441 0.0112 Not detected Not detected

[0103] As can be seen from the data in Comparative Example 1, in this comparative example, only a calibration curve for a rhodium-free matrix was established based on a standard solution of a rhodium-free matrix. When using this curve to calculate the impurity content in the test sample solution containing rhodium, the presence of rhodium caused positive interference in the determination of most impurity elements, resulting in an overestimation of the impurity element content and seriously affecting the accuracy of the determination results.

[0104] Comparative Example 2

[0105] This comparative example provides an accurate method for determining impurity elements in rhodium powder after removing interference from the rhodium matrix. Compared with Example 1, the difference is that steps S5, S6, and S7 are omitted, i.e., the content of impurity elements in the blank solution is not measured. The other steps are roughly the same as in Example 1 and will not be described again here. The rhodium powder sample tested in this comparative example is the same as that used in Example 1, and the test results are shown in Table 6.

[0106] Table 6 Content of various impurity elements in rhodium powder

[0107]

[0108] As can be seen from the data in Example 1, if the content of impurity elements in the blank solution is not measured, the hydrochloric acid, hydrogen peroxide and elements such as iron, silicon, aluminum and magnesium added during the digestion of the blank solution will be ignored, which will lead to the measured content of impurity elements in the sample being too high and produce systematic errors. Therefore, it is essential to measure the blank solution.

[0109] Comparative Example 3

[0110] This comparative example provides an accurate method for determining impurity elements in rhodium powder after removing interference from the rhodium matrix. Compared to Example 1, the difference lies in that steps S5 and S6 are omitted; instead, the rhodium-containing matrix established in step S4 is used directly as the calibration curve to determine the impurity content in the blank solution. Other steps are largely the same as in Example 1 and will not be repeated here. The rhodium powder sample tested in this comparative example is the same as that used in Example 1, and the test results are shown in Table 7.

[0111] Table 7 Content of various impurity elements in rhodium powder

[0112] Element Platinum Iridium Ruthenium Aluminium Iron Silicon Silver Content (%) Not detected 0.0453 0.0784 0.0082 0.0114 0.0066 Not detected Element Gold Copper Nickel Cadmium Antimony Tellurium Palladium Content (%) Not detected Not detected 0.0154 Not detected 0.0321 0.0211 Not detected Element Lead Zinc Magnesium Cobalt Zirconium Content (%) Not detected 0.0343 0.0112 Not detected Not detected

[0113] As can be seen from the data in Example 1, if a standard solution containing a rhodium matrix is ​​used to directly measure the blank solution, the measurement of most impurity elements will be interfered with due to the difference in the matrices. This will affect the measurement of the concentration of impurity elements in the blank solution, resulting in a large deviation between the final measured content of impurity elements in the rhodium powder and the actual content, thus affecting the accuracy of the measurement results.

[0114] In summary, this invention provides an accurate method for determining impurity elements in rhodium powder by removing interference from the rhodium matrix. A modified standard addition method is used to establish calibration curves for both rhodium-containing and rhodium-free matrices, which are then used to determine the content of impurity elements in the test solution and blank solution, respectively. The content of impurity elements in the rhodium powder is then calculated. This method not only eliminates the interference of rhodium in the matrix on the determination of impurity element content but also eliminates the systematic error caused by deviations in the determination results of impurity elements in the blank solution, effectively ensuring the accuracy of the test results. Furthermore, the method is simple, rapid, highly sensitive, and provides reliable results.

[0115] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for accurately determining impurity elements in rhodium powder after removing interference from the rhodium matrix, characterized in that, Includes the following steps: S1. Weigh out several equal portions of rhodium powder samples, and sequentially perform microwave digestion and heating concentration on each portion of the rhodium powder sample to obtain several sample solutions. S2. Following the same procedure as in step S1, the blank sample is subjected to the microwave digestion treatment and the heating concentration treatment sequentially to obtain a blank solution; S3. After diluting at least one of the sample solutions to a final volume, use it as the sample solution to be tested; add different amounts of mixed standard solution to at least three of the sample solutions, and dilute to a final volume to use them as standard solutions containing a rhodium matrix; the mixed standard solution contains the impurity element to be tested; S4. The test sample solution and the standard solution containing the rhodium matrix are detected by inductively coupled plasma atomic emission spectrometry. A calibration curve for the rhodium matrix is ​​established based on the detection results, and the concentration of impurity elements in the test sample solution is calculated based on the calibration curve of the rhodium matrix. S5. Add different amounts of the mixed standard solution to the volumetric flask, then add hydrochloric acid solution, and dilute to volume to obtain the rhodium-free matrix standard solution; dilute the blank solution to volume to obtain the blank solution to be tested. S6. The standard solution of the rhodium-free matrix and the blank solution to be tested are detected by inductively coupled plasma atomic emission spectrometry. A calibration curve of the rhodium-free matrix is ​​established based on the detection results, and the concentration of impurity elements in the blank solution to be tested is calculated based on the calibration curve of the rhodium-free matrix. S7. Calculate the content of impurity elements in the rhodium powder sample based on the concentration of impurity elements in the sample solution to be tested and the concentration of impurity elements in the blank solution to be tested.

2. The method for accurately determining impurity elements in rhodium powder after removing interference from the rhodium matrix according to claim 1, characterized in that, The microwave digestion process includes the following steps: The rhodium powder sample was placed in a microwave digestion vessel, and hydrochloric acid solution and hydrogen peroxide solution were added to the microwave digestion vessel. The vessel was then heated in a digestion apparatus.

3. The method for accurately determining impurity elements in rhodium powder after removing interference from the rhodium matrix according to claim 2, characterized in that, In step S1, the mass of each rhodium powder sample is 0.0995 to 0.1005 g; the density of the hydrochloric acid solution added to the microwave digestion vessel is 1.19 g / mL, and the amount added is 9 to 15 mL; the volume fraction of the hydrogen peroxide solution is 30%, and the amount added is 3 to 5 mL.

4. The method for accurately determining impurity elements in rhodium powder after removing interference from the rhodium matrix according to claim 2, characterized in that, During the microwave digestion process, the temperature for heating in the digester is 240–260°C, and the heating time is 1–2 hours.

5. The method for accurately determining impurity elements in rhodium powder after removing interference from the rhodium matrix according to claim 1, characterized in that, The heating and concentration process is carried out at a temperature of 180–220°C, and both the sample solution and the blank solution are concentrated to 0.8–1.2 mL.

6. The method for accurately determining impurity elements in rhodium powder after removing interference from the rhodium matrix according to claim 1, characterized in that, The mixed standard solution contains one or more of the following metallic impurities: Platinum, iridium, ruthenium, aluminum, iron, silicon, magnesium, silver, palladium, gold, lead, copper, zinc, nickel, cadmium, cobalt, antimony, zirconium, tellurium; The concentration of each metal impurity in the mixed standard solution is 5–15 μg / mL.

7. The method for accurately determining impurity elements in rhodium powder after removing interference from the rhodium matrix according to claim 1, characterized in that, In step S3, the method for preparing the standard solution containing the rhodium matrix includes: adding 0.5 mL, 1 mL, and 2 mL of the mixed standard solution to three portions of the sample solution, respectively, and making up to a final volume to obtain the standard solution containing the rhodium matrix.

8. The method for accurately determining impurity elements in rhodium powder after removing interference from the rhodium matrix according to claim 1, characterized in that, In step S5, the method for preparing the rhodium-free matrix standard solution includes: adding 0 mL, 0.5 mL, 1 mL, and 2 mL of the mixed standard solution to four volumetric flasks respectively, then adding hydrochloric acid solution, and making up to volume to obtain the rhodium-free matrix standard solution.

9. The method for accurately determining impurity elements in rhodium powder after removing interference from the rhodium matrix according to claim 1, characterized in that, In step S5, the density of the hydrochloric acid solution is 1.19 g / mL, and the amount added is 0.8 to 1.2 mL.

10. The method for accurately determining impurity elements in rhodium powder after removing interference from the rhodium matrix according to claim 1, characterized in that, In step S7, the formula for calculating the content of impurity elements in the rhodium powder sample is as follows: Where, ω i The mass fraction of impurity element i in the rhodium powder sample is expressed as a percentage; i represents one of platinum, iridium, ruthenium, aluminum, iron, silicon, magnesium, silver, palladium, gold, lead, copper, zinc, nickel, cadmium, cobalt, antimony, zirconium, and tellurium. C i The concentration of impurity element i in the sample solution to be tested is expressed in micrograms per milliliter. C bi The concentration of impurity element i in the blank solution to be tested is expressed in micrograms per milliliter. V represents the volume of the sample solution to be tested, in milliliters; m represents the mass of the rhodium powder sample, in grams.

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