Method for preparing test solution of impurity content in titanium tetrachloride prepared by mixed acid method and detection method

Abstract

The application discloses a method for preparing a test solution for testing impurity content in titanium tetrachloride prepared by a mixed acid method and a detection method, and belongs to the technical field of component detection and analysis. The preparation method and the detection method are as follows: water is added to a titanium tetrachloride sample to react until the precipitate is dissolved and no dense white smoke is generated any more; the obtained product is heated and evaporated dry under the condition that the temperature is not higher than 100 DEG C; then, hydrofluoric acid solution, nitric acid solution and appropriate water are added, and heating is carried out under the condition that the temperature is not higher than 150 DEG C until the titanium matrix is completely dissolved, so that a clear and transparent solution is obtained; water is added for dilution and constant volume, so that the test solution for testing the impurity content in the titanium tetrachloride is obtained, and the concentration of the hydrofluoric acid and the concentration of the nitric acid are both less than 2%; and the impurity content in the solution is determined by using ICP-MS or ICP-OES. The method is simple in operation, effectively avoids the pollution risk of external elements, reduces the operation error, and thus greatly improves the accuracy and reliability of the analysis result.

Description

Technical Field

[0001] This invention belongs to the field of component detection and analysis technology, and relates to a method for preparing a test solution for the content of impurities in titanium tetrachloride by mixed acid method and a detection method. Specifically, it relates to a method for preparing a sample test solution and an analysis method for detecting the content of trace, ultra-trace and ultra-trace levels of metallic impurities and other elements in titanium tetrachloride. Background Technology

[0002] TiCl4 is a key intermediate product in the chloride process for producing sponge titanium and titanium dioxide. The quality of TiCl4, including its impurity element content, severely restricts the quality and application areas of finished metallic titanium and titanium oxide products. With the rapid development of integrated circuit technology, TiCl4 is widely used as a precursor for high-temperature TiN deposition in DRAM, 3D NAND flash memory chips, and logic chips. For example, it is used to deposit TiN as a metal electrode layer in memory chips and to react with TEA to deposit TiAl or TiN as a work function layer in logic chips. However, TiCl4 used in the semiconductor field requires a purity of not less than 99.99999%, and there are strict limits on the content of more than 20 metallic impurities, including vanadium, arsenic, tin, silver, bismuth, gallium, and iron, with each impurity content not exceeding 1 ppb. Therefore, analytical methods for detecting trace, ultra-trace, and ultra-trace impurity element content in TiCl4 are indispensable supporting technologies for its production control and product application.

[0003] The literature "Determination of Impurity Elements in Titanium Tetrachloride Liquid by Inductively Coupled Plasma Atomic Emission Spectrometry" dilutes TiCl4 sample solutions with high-concentration dilute hydrochloric acid or dilute nitric acid and uses inductively coupled plasma atomic emission spectrometry (ICP-OES) to determine inorganic impurity elements such as Si, Fe, V, and Al. However, the ICP-OES detection method used in this approach is limited by its detection limit and other performance indicators, making it unsuitable for the determination of trace and micro-elements. Furthermore, the sample pretreatment method of diluting TiCl4 with a large amount of high-concentration dilute hydrochloric acid solution results in hydrogen and chloride ion concentrations in the sample solution far exceeding the upper limit that ICP-OES can tolerate. This leads to matrix effects and mass spectrometry interference, significantly impacting the accuracy of the results, and also severely corrodes valuable components such as the interface cone of the ICP-MS instrument.

[0004] The literature "Determination of 13 Elemental Impurities in Refined Titanium Tetrachloride by Acid Hydrolysis-ICP-MS" describes a hydrolysis reaction in which titanium tetrachloride sample is slowly added to hydrochloric acid solution to generate a white emulsion of hydrolysate. Nitric acid is then added and the mixture is heated at low temperature for digestion. Finally, the solution is diluted with hydrochloric acid to obtain the test hydrolysate. The content of 13 elemental impurities in refined titanium tetrachloride is then analyzed using an external standard quantitative method. This method cannot address the high concentration of Cl coexisting in TiCl4. - The impact of mass spectrometry interference from polyatomic ions on elemental analysis, and the effects of high concentrations of H2O.+ There are issues with the corrosion of the instrument. Furthermore, this method uses large amounts of hydrochloric acid and nitric acid solutions in the preparation of the test solution, and the amount of reagents used is far greater than the amount of TiCl4 sample. This adds to the serious influence of impurities present in the background of the reagent blank on the determination, requiring extremely high reagent purity, and necessitating consideration of eliminating polyatomic ion spectral interference caused by nitrogen oxides.

[0005] The literature "Determination of Arsenic in Titanium Tetrachloride by Inductively Coupled Plasma Mass Spectrometry" establishes an analytical method for determining the arsenic content in titanium tetrachloride using inductively coupled plasma mass spectrometry (ICP-MS). Nitric acid was used to decompose the sample solution, and the mass spectrometry interferences present during measurement were investigated. A dynamic reaction cell (DRC) was used to eliminate interferences, with NH3 as the reaction gas. The optimal conditions for eliminating interferences were achieved at an Rpq value of 0.45 and a DRC gas flow rate of 0.5 mL / min. 75 ArCl 75 Interference from As. This method uses only nitric acid for hydrolysis, which can easily lead to incomplete dissolution. It requires centrifugation or filtration to remove fine particles such as titanium oxide suspended in the test solution that may clog instrument components. The supernatant must be separated and re-diluted to a fixed volume before the element content can be determined. This not only increases the number of steps and the risk of contamination of trace elements, but the secondary separation and dilution also increases the error in the detection results.

[0006] It is evident that existing technologies suffer from drawbacks such as complex operation, long process cycles, high testing costs, numerous interfering factors, and large errors in detection results. Therefore, developing an analytical method capable of accurately detecting trace, ultra-trace, and ultra-trace impurity elements in TiCl4 is of paramount importance for its production control and practical applications. Summary of the Invention

[0007] The technical problem to be solved by this invention is the detection of high concentrations of Cl during TiCl4 detection. - H + This includes issues such as matrix effects, acidity effects, and mass spectrometry interference that affect the reliability of detection results, as well as corrosion of the detection instrument caused by strongly acidic media solutions.

[0008] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0009] Firstly, in order to completely eliminate the high concentration of Cl in the TiCl4 sample solution - H + To address the impact of coexisting components on detection results and instrument operation, this invention provides a method for preparing a test solution for impurity content in titanium tetrachloride using a mixed acid method, comprising the following steps:

[0010] S1. Add an appropriate amount of water to the titanium tetrachloride sample to be tested, and react fully at room temperature to generate a yellow flocculent precipitate. Then continue to add water to react until the precipitate dissolves and no more thick white smoke is produced.

[0011] S2. The product obtained in step S1 is heated and evaporated at a temperature not exceeding 100°C to obtain a titanium-based solid mainly composed of anatase titanium dioxide.

[0012] S3. Add hydrofluoric acid solution, nitric acid solution and appropriate amount of water to the titanium-based solid obtained in step S2, and heat at a temperature not higher than 150°C until the titanium matrix is ​​completely dissolved to obtain a clear and transparent solution.

[0013] S4. After the solution obtained in step S3 has cooled, add water to dilute and bring the volume to a final volume to obtain a test solution for the impurity content in titanium tetrachloride with both hydrofluoric acid and nitric acid concentrations less than 2%.

[0014] In step S1 above, the volume ratio of the titanium tetrachloride sample to be tested to the water added for the first time is 1:0.5 to 3, and the volume ratio of the titanium tetrachloride sample to be tested to the water added for the second time is 1:0.5 to 3.

[0015] In step S1 above, adding water to the titanium tetrachloride sample will trigger a violent hydrolysis reaction, causing a large amount of HCl gas to escape rapidly. To avoid an overly violent reaction, water should be added slowly dropwise to the titanium tetrachloride to control the reaction rate and prevent safety issues caused by the large-scale escape of HCl gas; at the same time, it should be avoided that volatile impurities are released and lost with the HCl gas during the violent hydrolysis process.

[0016] In step S2 above, the temperature for heating and drying is 90-100°C.

[0017] In step S3 above, the volume ratio of the titanium tetrachloride sample to be tested to the hydrofluoric acid solution is 1:0.5 to 1, and the volume ratio of the titanium tetrachloride sample to be tested to the nitric acid solution is 1:0.5 to 1.

[0018] In step S3 above, the concentration of the hydrofluoric acid solution is ≥40%, and the concentration of the nitric acid solution is 65% to 68%.

[0019] In step S3 above, the amount of water added should be sufficient to ensure that the titanium-based solids are just completely dissolved.

[0020] In step S3 above, the heating and melting temperature is 100-150°C.

[0021] In step S4 above, the volume ratio of the titanium tetrachloride sample to be tested to the impurity content test solution in titanium tetrachloride is 1:20 to 250.

[0022] This invention fully utilizes the property that TiCl4 readily hydrolyzes in water to form titanium precipitate and a large amount of HCl fumes, providing a simple, rapid, and efficient method for removing Cl from TiCl4. - H + A method for preparing sample test solutions containing coexisting components. Water is added only to the TiCl4 sample solution, and through controlled hydrolysis or evaporation, a second precipitation and second dissolution of the precipitate are repeated to promote the presence of a large amount of Cl- in the sample. - and H + The precipitate is expelled in the form of volatile HCl, etc.; at the same time, the generated titanium dioxide precipitate exists in the form of anatase crystal structure that is easily soluble in acid, so that it can be quickly and completely redissolved by a very small amount of hydrofluoric acid and nitric acid.

[0023] This invention reduces ethanol evaporation loss by limiting the heating temperature conditions of the dissolution reaction, and the Ti in the test solution 4+ With F - The generated complex ions remain stable in the low-acidity medium, ensuring that the high-concentration titanium matrix does not re-hydrolyze and precipitate in the extremely low-acidity test solution. Besides the titanium matrix, the test solution contains only hydrofluoric acid (no more than 2.0%) and nitric acid (no more than 2.0%), which do not interfere with the determination. The test solution prepared by this method significantly reduces acidity and purifies the coexisting medium system compared to the original TiCl4 sample mother liquor, effectively eliminating interference from chloride ions and the corrosive effect of strong media on the instrument. The method uses very small amounts of hydrofluoric acid and nitric acid, greatly reducing analytical costs and the impact of reagent blank background contamination on the results. The precipitate generated by the titanium-based hydrolysis reaction is completely redissolved, and the solution is clear and transparent without suspended or settled insoluble particles. There are no issues such as insoluble particles adsorbing, encapsulating, or encapsulating the analyte, thus avoiding problems that affect the reliability of the detection results. This method is simple to operate and has a short process, greatly shortening the testing cycle and reducing the risk of contamination during the preparation of the test solution for trace and ultra-trace element determination, thereby improving the accuracy and reliability of the results.

[0024] Secondly, this invention provides a method for detecting the impurity content in titanium tetrachloride, which is characterized by simple operation and short testing process, and can rapidly determine the content of trace, ultra-trace, and ultra-ultra-trace metallic impurities in TiCl4. The specific method is as follows: A test solution for the impurity content in titanium tetrachloride is prepared according to the above-mentioned mixed acid method. The content of impurity elements in the solution is determined by ICP-MS or ICP-OES. The impurity elements include Li, Be, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Sb, Cu, Zn, Ga, As, Ni, Mo, Cd, Sn, Sr, Pb, Ba, Bi, Th, and U.

[0025] Furthermore, when the volume ratio of the titanium tetrachloride sample to the test solution for impurities in titanium tetrachloride is 1:100–250, or when the impurity content in the titanium tetrachloride sample is less than or equal to 0.5 mg / L, ICP-MS is used for detection; the detection parameters are: tandem mass spectrometry; RF power 1200–1350 W; He\O2\NH3 collision reaction mode; 103 Rh internal standard correction mode; standard addition method / calibration curve method.

[0026] Furthermore, when the volume ratio of the titanium tetrachloride sample to the test solution for impurities in titanium tetrachloride is 1:20 to <100, or when the impurity content in the titanium tetrachloride sample is greater than 0.5 mg / L, ICP-OES detection is used; the detection parameters are: RF power 1200-1350 W; standard addition method / calibration curve method.

[0027] Furthermore, both the ICP-MS and ICP-OES can use instrument components made of glass, such as quartz glass concentric atomizers or quartz glass vortex fog chambers, which have higher atomization and transmission efficiency.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] This method involves directly hydrolyzing titanium tetrachloride with pure water, followed by heating to dryness to completely remove coexisting chloride and hydrogen ions. Subsequently, only trace amounts of hydrofluoric acid and nitric acid are needed to completely dissolve the resulting titanium-based precipitate. The solution is then diluted to volume using only pure water, and the content of impurity elements in the test solution is determined using ICP-MS or ICP-OES. The key lies in the effective removal of highly interfering chloride and corrosive hydrogen ions through hydrolysis, solving the problems of matrix component interference and corrosion of the instrument by strong acid solutions. Simultaneously, the complex formed between fluoride and titanium ions allows titanium to remain dissolved in a low-acidity medium, ensuring rapid and complete dissolution of the precipitate. The resulting solution is clear and transparent, free of any insoluble solid particles. Hydrolysis does not occur with dilution with only water, and the prepared test solution requires no additional steps such as centrifugation or filtration; it can be directly analyzed after a single dilution and volume adjustment.

[0030] This method effectively eliminates polyatomic ion interference generated by chloride ions in mass spectrometry analysis and further solves the corrosion problem of high-concentration hydrogen ions on the instrument's sample introduction system and nebulizer. Furthermore, due to the extremely low acid dosage, its concentration in the test solution used for ICP-MS / ICP-OES analysis is controlled below 2%, which significantly reduces the interference of impurity elements introduced by the reagent background blank and nitrogen oxides generated by nitric acid on mass spectrometry determination, thus improving the accuracy of trace element detection.

[0031] This invention features a simple and streamlined operation process with few steps, effectively avoiding the risk of foreign element contamination that may arise from intermediate steps such as solution transfer, centrifugation / filtration, secondary separation, and dilution. This reduces operational errors and significantly improves the accuracy and reliability of analytical results. Furthermore, ethanol, as an organic solvent, is used in small quantities, and the background levels of inorganic impurities it contains are far lower than those of strong inorganic acids such as nitric acid. Additionally, hydrofluoric acid and nitric acid have low boiling points and are highly volatile, allowing for purification through routine sub-boiling distillation in the laboratory, further reducing the impact of reagent impurities on ultra-trace analysis. Detailed Implementation

[0032] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with the embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Unless otherwise defined, all technical terms used herein have the same meaning as understood by those skilled in the art.

[0033] A method for preparing a test solution for impurities in titanium tetrachloride using a mixed acid method and a detection method thereof: An appropriate amount of water is added to the titanium tetrachloride sample to be tested, and the mixture is allowed to react fully at room temperature to generate a yellow flocculent precipitate. Water is then added continuously until the precipitate dissolves and no more dense white fumes are produced. The resulting product is heated to dryness at a temperature not exceeding 100°C to obtain a titanium-based solid mainly composed of anatase titanium dioxide. Hydrofluoric acid solution, nitric acid solution, and an appropriate amount of water are added to the titanium-based solid, and the mixture is heated at a temperature not exceeding 150°C until the titanium matrix is ​​completely dissolved, resulting in a clear and transparent solution. After the solution cools, it is diluted with water to a fixed volume to obtain a test solution for impurities in titanium tetrachloride with both hydrofluoric acid and nitric acid concentrations less than 2%. The content of impurity elements in the solution was determined by ICP-MS or ICP-OES; the impurity elements included Li, Be, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Sb, Cu, Zn, Ga, As, Ni, Mo, Cd, Sn, Sr, Pb, Ba, Bi, Th, and U.

[0034] In one embodiment of the present invention, the volume ratio of the titanium tetrachloride sample to be tested to the water added for the first time is 0.5 to 1:3, and the volume ratio of the titanium tetrachloride sample to be tested to the water added for the second time is 1:0.5 to 3. As a non-limiting example, the volume ratio of the titanium tetrachloride sample to be tested to the water added for the first time can be 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, or any ratio therein, and the volume ratio of the titanium tetrachloride sample to the water added for the second time can be 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, or any ratio therein.

[0035] In one embodiment of the present invention, the heating and drying temperature is 90 to 100°C. As a non-limiting example, the heating and drying temperature is 90°C, 100°C, or within any two of the above values.

[0036] In one embodiment of the present invention, the volume ratio of the titanium tetrachloride sample to the hydrofluoric acid solution is 1:0.5 to 1, and the volume ratio of the titanium tetrachloride sample to the nitric acid solution is 1:0.5 to 1. As a non-limiting example, the volume ratio of the titanium tetrachloride sample to the hydrofluoric acid solution can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, or any ratio therein, and the volume ratio of the titanium tetrachloride sample to the nitric acid solution can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, or any ratio therein.

[0037] In one embodiment of the present invention, the heating and dissolving temperature is 100 to 150°C. As a non-limiting example, the heating and dissolving temperature is 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, or within any two of the above values.

[0038] In one embodiment of the present invention, the volume ratio of the titanium tetrachloride sample to be tested to the test solution for impurities in titanium tetrachloride is 1:20 to 250. As a non-limiting example, the volume ratio of the titanium tetrachloride sample to be tested to the test solution for impurities in titanium tetrachloride can be 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, 1:110, 1:120, 1:130, 1:140, 1:150, 1:160, 1:170, 1:180, 1:190, 1:200, 1:210, 1:220, 1:230, 1:240, 1:250, or any ratio therebetween.

[0039] Example 1

[0040] (1) Take 0.5 mL of TiCl4 sample solution (sample 1#) into a 50 mL PFA quantitative tube, slowly add about 1.0 mL of water dropwise, and react completely with TiCl4 liquid to form a yellow flocculent precipitate and a large amount of concentrated white HCl fumes. Then continue to add water until the precipitate dissolves. When no more concentrated white fumes are produced in the container, place the container in a 90℃ water bath and heat until the solution evaporates to dryness. Add 0.5 mL of HF solution (40%), 0.5 mL of HNO3 solution (65%) and 10 mL of water, place on a 100℃ hot plate and heat until the precipitate is completely dissolved and the solution is clear and transparent. Dilute with water to 50 mL and make up to volume. Use ICP-MS to determine the element content in the test solution. The detection parameters are: RF power 1300 W; He\O2\NH3 collision reaction mode. 103 Rh internal standard correction mode; calibration curve method;

[0041] (2) Take 1.0 mL of TiCl4 sample solution (sample 2#) into a 100 mL PFA quantitative tube, slowly add about 2 mL of water dropwise, and react completely with the TiCl4 liquid to form a yellow flocculent precipitate and a large amount of concentrated white HCl fumes. Then continue to add water until the precipitate dissolves. When no more concentrated white fumes are produced in the container, place the quantitative tube in a 100℃ water bath and heat until the solution evaporates to dryness. Add 1.0 mL of HF solution (40%), 1.0 mL of HNO3 solution (65%) and 15 mL of water, and place it on a 120℃ low-temperature hot plate and heat until the precipitate is completely dissolved and the solution is clear and transparent. Dilute with water to 100 mL and make up to volume. Use ICP-MS to determine the element content in the test solution. The detection parameters are: RF power 1300W; He\O2\NH3 collision reaction mode. 103 Rh internal standard correction mode; calibration curve method;

[0042] (3) Take 5.0 mL of TiCl4 sample solution (sample 3#) into a polytetrafluoroethylene beaker, slowly add about 10 mL of water dropwise, and react completely with the TiCl4 liquid to form a yellow flocculent precipitate and a large amount of concentrated white HCl fumes. Then continue to add water until the precipitate dissolves. When no more concentrated white fumes are produced in the container, place the beaker in a 100℃ water bath and heat until the solution evaporates to dryness. Place 2.5 mL of HF solution (40%), 5.0 mL of HNO3 solution (65%) and 20 mL of water on a 150℃ low-temperature hot plate and heat until the precipitate is completely dissolved and the solution is clear and transparent. Dilute with water to 100 mL and make up to volume. Use ICP-OES to determine the element content in the test solution. The detection parameters are: RF power 1200~1350W; calibration curve method.

[0043] (4) Take 2.5 mL of TiCl4 sample solution (sample 4#) into a polytetrafluoroethylene beaker, slowly add about 6 mL of water dropwise, and react completely with the TiCl4 liquid to form a yellow flocculent precipitate. A concentrated white fumes of HCl will be emitted. Then continue to add water dropwise until the precipitate dissolves. When no more concentrated white fumes are emitted from the container, place the beaker in a 95℃ water bath and heat until the solution evaporates to dryness. Add 2.0 mL of HF solution (40%), 2.0 mL of HNO3 solution (65%) and 15 mL of water, and place it on a 150℃ low-temperature hot plate and heat until the precipitate is completely dissolved and the solution is clear and transparent. Dilute with water to 100 mL and make up the volume. Use ICP-OES to determine the element content in the test solution. The detection parameters are: RF power 1200~1350W; calibration curve method.

[0044] The test solution preparation and element content determination were repeated 8 times according to (1) to (4) above, and the average value and relative standard deviation (RSD) of the 8 measurement results were calculated to evaluate the detection precision level of the method of the present invention. The results are shown in Table 1.

[0045] Table 1 Precision Test (n=8)

[0046]

[0047]

[0048] As shown in Table 1, the relative standard deviation (RSD) for determining elements ≥0.01 mg / kg using the method of this invention is ≤25%, indicating that the results of repeated determinations are consistent, the method has good repeatability and reproducibility, and the method has a high level of precision.

[0049] Example 2

[0050] The effectiveness of the method of the present invention in solving the problems of chloride ions and hydrogen ions affecting the detection results and causing corrosion to the detection instrument during the detection of titanium tetrachloride is evaluated.

[0051] 1. Targeting chloride ions

[0052] The chloride ion content in the test solutions prepared according to (1) to (4) above was determined by reacting with unremoved Cl-. - Test solution Cl - The theoretical concentration was used to evaluate the chloride ion removal rate of the method of the present invention, and the results are shown in Table 2.

[0053] Table 2. Verification Test of Chloride Ion Removal Effect

[0054]

[0055] As shown in Table 2, the method of the present invention removes chloride ions at a rate greater than 80%, effectively reducing corrosion to instruments and equipment and interference with the determination of the components to be determined.

[0056] 2. Targeting hydrogen ions

[0057] The original mother liquor of titanium tetrachloride contains almost no hydrogen ions. In conventional methods, to prevent the hydrolysis of titanium tetrachloride in low-acidity media to form titanium oxide precipitate, a large amount of acid is added when diluting the titanium tetrachloride solution, thus introducing a large number of hydrogen ions. These hydrogen ions not only affect the accuracy of the detection results but also corrode the detection instrument. The method of this invention requires only a very small amount of acid to be added during the dilution process, thus significantly reducing the concentration of introduced hydrogen ions. Compared with the conventional method that uses a high concentration of acid for dilution, the method of this invention reduces the hydrogen ion concentration by orders of magnitude.

[0058] Calculations show that the hydrogen ion concentration in the test solutions prepared by (1) to (4) is significantly lower than that of traditional methods. This indicates that the method of the present invention can effectively control and significantly reduce the hydrogen ion concentration in the test solution, thereby reducing its interference with the detection results and the risk of corrosion to the instrument.

Claims

1. A method for preparing a solution for testing the impurity content in titanium tetrachloride using a mixed acid method, characterized in that, Includes the following steps: S1. Add an appropriate amount of water to the titanium tetrachloride sample to be tested, and react fully at room temperature to generate a yellow flocculent precipitate. Then continue to add water to react until the precipitate dissolves and no more thick white smoke is produced. S2. The product obtained in step S1 is heated and evaporated at a temperature not exceeding 100°C to obtain a titanium-based solid mainly composed of anatase titanium dioxide. S3. Add hydrofluoric acid solution, nitric acid solution and appropriate amount of water to the titanium-based solid obtained in step S2, and heat at a temperature not higher than 150°C until the titanium matrix is ​​completely dissolved to obtain a clear and transparent solution. S4. After the solution obtained in step S3 is cooled, add water to dilute and make up the volume to obtain a test solution for the impurity content in titanium tetrachloride with both hydrofluoric acid concentration and nitric acid concentration less than 2%. In step S1, the volume ratio of the titanium tetrachloride sample to be tested to the water added for the first time is 1:0.5~3, and the volume ratio of the titanium tetrachloride sample to be tested to the water added for the second time is 1:0.5~3. In step S2, the temperature for heating and drying is 90~100℃; In step S3, the heating and melting temperature is 100~150℃.

2. The method for preparing a test solution for impurity content in titanium tetrachloride using the mixed acid method according to claim 1, characterized in that: In step S3, the volume ratio of the titanium tetrachloride sample to be tested to the hydrofluoric acid solution is 1:0.5~1, and the volume ratio of the titanium tetrachloride sample to be tested to the nitric acid solution is 1:0.5~1.

3. The method for preparing a test solution for impurity content in titanium tetrachloride using the mixed acid method according to claim 1, characterized in that: In step S3, the concentration of the hydrofluoric acid solution is ≥40%, and the concentration of the nitric acid solution is 65%~68%.

4. The method for preparing a test solution for impurity content in titanium tetrachloride using the mixed acid method according to claim 1, characterized in that: In step S4, the volume ratio of the titanium tetrachloride sample to be tested to the impurity content test solution in titanium tetrachloride is 1:20~250.

5. A method for detecting impurity content in titanium tetrachloride, characterized in that: A test solution for impurity content in titanium tetrachloride is prepared by the method according to any one of claims 1 to 4, and the content of impurity elements in the solution is determined by ICP-MS or ICP-OES. The impurity elements include Li, Be, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Sb, Cu, Zn, Ga, As, Ni, Mo, Cd, Sn, Sr, Pb, Ba, Bi, Th, and U.

6. The method for detecting impurity content in titanium tetrachloride according to claim 5, characterized in that: When the volume ratio of the titanium tetrachloride sample to the test solution for impurities in titanium tetrachloride is 1:100~250, or when the impurity content in the titanium tetrachloride sample is less than or equal to 0.5 mg / L, ICP-MS is used for detection. The detection parameters were: tandem mass spectrometry; RF power 1200~1350W; He\O2\NH3 collision reaction mode; 103 Rh internal standard correction mode; standard addition method / calibration curve method.

7. The method for detecting impurity content in titanium tetrachloride according to claim 5, characterized in that: When the volume ratio of the titanium tetrachloride sample to the test solution for impurities in titanium tetrachloride is 1:20 to <100, or when the impurity content in the titanium tetrachloride sample is greater than 0.5 mg / L, ICP-OES detection shall be used. The detection parameters are: RF power 1200~1350 W; standard addition method / calibration curve method.

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