A method for detecting trace elements in electrolytes using ICP-OES and its application

Abstract

This invention relates to the field of detection and analysis technology, and particularly to a method and application for detecting trace elements in electrolytes using ICP-OES. The method includes: S1. Sample pretreatment: Weighing the electrolyte sample to be tested, performing wet digestion for pretreatment, and adding Sc internal standard solution to the pretreated digestion solution to obtain the sample solution; S2. Preparation of internal standard calibration solution: Preparing a gradient concentration standard working solution containing the trace element to be tested, and adding Sc internal standard solution to each gradient concentration standard working solution to obtain the internal standard calibration solution; S3. ICP-OES detection: Transferring the sample solution and internal standard calibration solution to the ICP-OES instrument for detection to determine the content of the trace element to be tested in the sample solution. This method, through specific sample pretreatment and internal standard calibration, achieves accurate detection of trace elements in electrolytes. The method has high sensitivity, meets the analytical requirements of electrolytes, and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of detection and analysis technology, and in particular to a method and application for detecting trace elements in electrolytes using ICP-OES. Background Technology

[0002] Electrolyte is a core material in lithium batteries, and its purity directly determines the battery's cycle life, charge-discharge efficiency, and safety performance. The content of trace elements such as Al, As, Cd, Cr, and Cu in the electrolyte is a key indicator for evaluating its purity. Therefore, establishing accurate, efficient, and universal quantitative analysis methods for trace elements in electrolytes is of significant industry value for quality control and product performance improvement in lithium battery production processes, and is also one of the key research areas in the field of new energy materials testing. Currently, due to its advantages such as detection efficiency and simultaneous determination of multiple elements, quantitative analysis technology for trace elements has become the mainstream method for component detection in the chemical and new energy materials fields, and is widely used in the trace element detection stage of electrolytes.

[0003] Existing methods for quantitative analysis of trace elements in electrolytes require specialized sample introduction systems, placing stringent demands on equipment and creating a high barrier to entry, hindering widespread application in routine laboratories. Furthermore, electrolytes contain high levels of elements such as sulfur (S) and phosphorus (P), resulting in significant matrix effects and often leading to low recovery rates with traditional quantitative analysis methods, failing to meet accuracy requirements. Moreover, existing methods struggle to achieve the low detection limits needed for specific trace elements like Fe, Ca, and K in electrolytes, particularly in practical production settings. The industry also lacks a standardized, methodologically validated quantitative analysis system for over ten trace elements in electrolytes, severely limiting the accuracy, stability, and standardization of electrolyte purity testing.

[0004] Chinese invention patent application CN117805217A discloses a method for detecting essential trace elements in human blood based on scientific research applications. Utilizing inductively coupled plasma mass spectrometry (ICP-MS) technology, it solves the problem of detecting heavy metal exposure in children's blood, achieving rapid and accurate detection of multiple essential trace elements. Chinese invention patent application CN101221139A discloses a method for detecting and analyzing trace elements in breast tumor tissue. Using synchrotron radiation X-ray fluorescence analysis, it detects trace elements in breast tumor samples, overcoming the problem of insufficient detection sensitivity in existing technologies and achieving high accuracy in detecting trace elements in breast tumors.

[0005] However, none of the existing technologies mentioned above have solved the aforementioned technical problems. There is an urgent need to develop an analytical method that can accurately, efficiently, and reliably detect trace elements in electrolytes. Summary of the Invention

[0006] To address the technical problems of insufficient accuracy and sensitivity, and complex detection methods in current quantitative analysis of trace elements in electrolytes, this invention proposes a quantitative analysis method for trace elements in electrolytes based on ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry). Through specific sample pretreatment methods and internal standard correction, the method achieves accurate detection of trace elements in electrolytes. The method has high sensitivity, can meet the analytical requirements of electrolytes, and has broad application prospects.

[0007] The first aspect of this invention provides a method for detecting trace elements in an electrolyte using ICP-OES, the method comprising: S1. Sample pretreatment: Weigh the electrolyte sample to be tested, perform pretreatment by wet digestion, add Sc (scandium) internal standard solution to the pretreated digestion solution to obtain the sample solution to be tested; S2. Preparation of internal standard calibration standard solution: Prepare a gradient concentration standard working solution containing the trace element to be measured, and add Sc internal standard solution to each gradient concentration standard working solution to obtain the internal standard calibration standard solution; S3. On-machine testing: Transfer the sample solution to be tested and the internal standard calibration solution to the ICP-OES for on-machine testing to determine the content of the trace elements to be tested in the sample solution.

[0008] To address the issues that existing technologies for detecting trace elements in samples largely rely on ICP-MS instruments, which suffer from problems such as complex instrument operation, high equipment costs, and cumbersome detection procedures, this invention innovatively adopts ICP-OES as the detection instrument. Through optimization of sample pretreatment and quantitative methods, the ICP-OES instrument, which is simpler to operate and lower in cost, can effectively achieve quantitative analysis of multiple trace elements in electrolytes without the need for complex ICP-MS instruments, greatly simplifying the detection process and lowering the detection threshold and cost.

[0009] Optionally, the wet digestion process includes: taking the electrolyte sample to be tested and mixing it with HNO3, heating it at 105-130℃ for 0.5-2 hours to obtain the digestion solution.

[0010] Alternatively, the electrolyte sample to be tested can be mixed with HNO3 and heated at 120°C for 1 hour.

[0011] Optionally, the ratio of the electrolyte sample to HNO3 is (0.1-0.5) g: (1-10) mL; more preferably, it is 0.2 g: 4 mL.

[0012] To address the shortcomings of existing technologies that require a dedicated organic sample introduction system for direct sample introduction when using ICP-OES to detect electrolytes, which involves complex configurations and high usage requirements, this invention designs a wet digestion sample pretreatment method. Through specific operations such as nitric acid digestion and volume adjustment, the organic matrix and high-salt components in the electrolyte are treated into an aqueous solution system suitable for conventional ICP-OES sample introduction. This eliminates the need for a complex organic sample introduction system, allowing detection to be completed using only a conventional ICP-OES sample introduction device, significantly improving the applicability and ease of operation of the method.

[0013] Optionally, the lithium hexafluorophosphate content in the electrolyte sample to be tested is 10 wt% or more, and more preferably 15 wt% or more, such as 16 wt%, 18 wt%, 20 wt%, 24%, etc.

[0014] Optionally, the trace elements to be tested include Al (aluminum), As (arsenic), Cd (cadmium), Cr (chromium), Cu (copper), Hg (mercury), Mg (magnesium), Ni (nickel), Pb (lead), Zn (zinc) and Na (sodium).

[0015] Optionally, when preparing the gradient concentration standard working solution containing the trace element to be measured, gradient concentration standard working solutions of Na and Hg are prepared separately.

[0016] During the research and development process, the applicant discovered that Na and Hg elements are prone to concentration drift and insufficient stability during analysis and detection. This invention uses a separate preparation method for Na and Hg elements when preparing gradient concentration standard working solutions, avoiding adsorption loss or morphological changes caused by mixing with other elements. This effectively ensures the stability and concentration accuracy of the standard solution and further improves the reliability of quantitative detection results of trace elements in the electrolyte.

[0017] Optionally, the concentration range of trace elements in the gradient concentration standard working solution is 0.10-10.0 mg / L.

[0018] Optionally, the concentration of Sc in the internal standard calibration solution and the sample solution to be tested is 1.00-10.00 mg / L; examples include 1.00 mg / L, 2.00 mg / L, 3.00 mg / L, 4.00 mg / L, 5.00 mg / L, 6.00 mg / L, 7.00 mg / L, 8.00 mg / L, 9.00 mg / L, and 10.00 mg / L; further options include 3.00-7.00 mg / L, and most preferably 5.00 mg / L.

[0019] To address the problem of poor accuracy and low recovery rates in existing analytical methods for detecting trace elements in electrolytes due to significant matrix effects caused by high levels of sulfur (S) and phosphorus (P) in the sample, this invention employs Sc (Sc) as an internal standard element. An equal concentration of Sc internal standard solution is added to both the standard solution and the sample solution. This internal standard correction method counteracts matrix interference and instrument signal fluctuations, achieving accurate quantification of trace elements. Furthermore, by optimizing and determining specific operating conditions for the ICP-OES instrument, combined with the internal standard correction method, the method achieves detection limits for most trace elements in electrolytes as low as below 2 mg / kg, exhibiting both high detection sensitivity and good repeatability. The spiked recovery rate remains stable within the range of 90%-116%, and the precision (RSD) is as low as below 3%, comprehensively improving the accuracy and reliability of the detection results.

[0020] Optionally, the ICP-OES test conditions in step S3 include: High-frequency generator power 1-2kW; Plasma flow rate: 10.0-15.0 L / min; Auxiliary gas flow rate: 0.8-1.2 L / min; Atomizer flow rate: 0.5-1.0 L / min.

[0021] In some implementations, the ICP-OES test conditions are as follows: The high-frequency generator has a power of 1.2kW; in the gas path system, the plasma flow rate is 12.0L / min, the auxiliary gas flow rate is 1.0L / min, and the atomizer flow rate is 0.7L / min; the optical path system adopts axial and radial observation methods, with an observation height of 8mm.

[0022] The quantitative logic of trace elements in the detection method of this invention is as follows: In step S3, the internal standard calibration solution and the sample solution to be tested are introduced into ICP-OES for determination. The emission intensity of each trace element to be tested and the scandium internal standard are measured respectively. A standard curve is established using the formula "concentration of trace element to be tested - emission intensity of trace element to be tested / emission intensity of scandium internal standard". The emission intensity ratio of each trace element in the sample solution to the scandium internal standard is substituted into the standard curve to calculate the concentration of each trace element in the sample to be tested, which is then converted into the actual content of trace elements in the electrolyte.

[0023] Optionally, the LOD (limit of detection) of each trace element in the method is below 0.05 μg / mL.

[0024] In some embodiments, the LOD of Al is 0.005 μg / mL, the LOD of As is 0.002 μg / mL, the LOD of Cd is 0.001 μg / mL, the LOD of Cr is 0.002 μg / mL, the LOD of Cu is 0.002 μg / mL, the LOD of Hg is 0.008 μg / mL, the LOD of Mg is 0.006 μg / mL, the LOD of Na is 0.029 μg / mL, the LOD of Ni is 0.003 μg / mL, the LOD of Pb is 0.009 μg / mL, and the LOD of Zn is 0.003 μg / mL.

[0025] Optionally, the MDL (method detection limit) of each trace element in the method is below 2 mg / kg.

[0026] In some embodiments, the MDL of Al is 0.262 mg / kg, the MDL of As is 0.075 mg / kg, the MDL of Cd is 0.057 mg / kg, the MDL of Cr is 0.116 mg / kg, the MDL of Cu is 0.114 mg / kg, the MDL of Hg is 0.394 mg / kg, the MDL of Mg is 0.306 mg / kg, the MDL of Na is 1.461 mg / kg, the MDL of Ni is 0.161 mg / kg, the MDL of Pb is 0.436 mg / kg, and the MDL of Zn is 0.147 mg / kg.

[0027] This invention employs wet digestion for electrolyte sample pretreatment, combined with specific ICP-OES measurement conditions, ultimately achieving LOD values ​​of all target elements below 0.05 μg / mL and MDL values ​​below 2 mg / kg. This enables highly sensitive quantitative detection of multiple trace elements such as Al, As, Cd, Cr, Cu, Hg, Mg, Ni, Pb, Zn, and Na in electrolytes, meeting the detection needs of electrolytes with high fluoride content.

[0028] The second aspect of this invention provides an application of the method for detecting trace elements in electrolytes using ICP-OES, which is applied in the field of new energy batteries.

[0029] Beneficial effects: This invention provides a method for detecting trace elements in electrolytes using ICP-OES, which has the following advantages: (1) This invention uses ICP-OES to replace the complex ICP-MS, eliminating the need for high-cost mass spectrometry equipment and complex operating procedures, which significantly reduces the instrument threshold and detection cost for the detection of trace elements in electrolytes; (2) The present invention treats the electrolyte sample by specific nitric acid wet digestion, which transforms the organic and high-salt matrix into a conventional aqueous solution system. There is no need to configure a complicated organic sample introduction system. The detection can be completed using only a conventional ICP-OES sample introduction device, which is simpler to operate and more applicable. (3) The present invention adopts the Sc internal standard correction method, adding Sc internal standard of equal concentration to the standard solution and the sample, which effectively offsets the matrix effect and instrument signal fluctuation caused by high S and P elements in the electrolyte. The spiked recovery rate is stable in the range of 90%-116%, and the quantitative results are accurate and reliable. (4) The present invention optimizes the ICP-OES sampling conditions, and the LOD of the target elements is below 0.05 μg / mL and the MDL is below 2 mg / kg. It has high detection sensitivity for trace elements such as Al, As, Cd, Cr, Cu, Hg, Mg, Ni, Pb, Zn and Na. (5) The precision of the test results of each target element in this method is less than 3%, and the overall RSD is less than 10%. The method has excellent repeatability and stability and can meet the accuracy requirements of trace element detection in electrolyte. Attached Figure Description

[0030] Figure 1 The Al standard curve obtained from Comparative Example 1; Figure 2 The standard curve of As obtained from Comparative Example 1; Figure 3 The Ca standard curve obtained from Comparative Example 1; Figure 4 The Cd standard curve obtained from Comparative Example 1; Figure 5 The Cr standard curve obtained from Comparative Example 1; Figure 6 The Cu standard curve obtained from Comparative Example 1; Figure 7 The K standard curve obtained from Comparative Example 1; Figure 8 The Mg standard curve obtained from Comparative Example 1; Figure 9 The Na standard curve obtained from Comparative Example 1; Figure 10 The Pb standard curve obtained from Comparative Example 1; Figure 11 The Ni standard curve obtained from Comparative Example 1; Figure 12 The Zn standard curve obtained from Comparative Example 1; Figure 13 The Fe standard curve obtained from Comparative Example 1; Figure 14The Hg standard curve obtained from Comparative Example 1. Detailed Implementation

[0031] In existing technologies, the determination of trace elements in electrolytes using ICP-OES typically involves direct sample loading after dilution with ethanol and carbonate aqueous solutions. This method requires the ICP-OES instrument to be equipped with a dedicated organic sample introduction system, resulting in a high barrier to entry and limited applicability, making it difficult to promote in routine laboratories. Furthermore, electrolytes contain high levels of sulfur (S) and phosphorus (P), leading to significant matrix effects. When using conventional standard curve methods for quantitative analysis, the spiked recovery rate is generally below 90%, failing to meet the accuracy requirements for quantitative analysis. This invention provides a standardized, fully methodologically validated quantitative analysis method for more than ten trace elements in electrolytes, meeting the accuracy and standardization requirements for trace element detection in electrolytes.

[0032] The present invention will be explained below with reference to implementation examples. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Information on the standard products used in the following implementation examples is shown in Table 1.

[0033] Table 1 Standard Product Information Table

[0034] Information on the electrolyte samples used in the following implementation cases is shown in Tables 2 and 3; information on the equipment and consumables is shown in Table 4.

[0035] Table 2 Electrolyte Sample 1 Formulation Information

[0036] Table 3 Electrolyte Sample 2 Formulation Information

[0037] Table 4 Equipment and Consumables Information

[0038] Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. Unless otherwise specified, the solvent for solutions involved in this invention is water; and the concentrations involved are mass concentrations.

[0039] Example 1 This embodiment provides a method for detecting trace elements in electrolytes using ICP-OES, the method comprising: S1. Sample Pretreatment Accurately weigh 0.2 g of the electrolyte sample to be tested (electrolyte sample 1, accurate to 0.0001 g) into a 50 mL centrifuge tube, add 4 mL of HNO3 for wet digestion, heat at 120 °C for 1 h, dilute to 10 mL with primary water, add 50 μL of 1000 mg / L Sc internal standard solution, mix well to obtain the sample solution to be tested; S2. Preparation of internal standard calibration solution S2.1 Preparation of standard stock solutions Standard Stock Solution 1: Accurately transfer 5 mL of Mixed Standard 1 into a 50 mL volumetric flask, and dilute to the mark with 5 wt% nitric acid aqueous solution to prepare 100 mg / L Standard Stock Solution 1; store it at 2-8℃ protected from light, with a shelf life of 3 months; Standard Stock Solution 2: Accurately transfer 5 mL of Mixed Standard 2 into a 50 mL volumetric flask, and dilute to the mark with 5 wt% nitric acid aqueous solution to prepare 100 mg / L Standard Stock Solution 2; store it at 2-8℃ protected from light, with a shelf life of 3 months; Standard stock solution 3: Accurately transfer 5 mL of Na standard solution into a 50 mL volumetric flask, and dilute to the mark with primary water to prepare 100 mg / L standard stock solution 3; store it at 2-8℃ protected from light, with a shelf life of 1 month; Standard stock solution 4: Accurately transfer 5 mL of Hg standard solution into a 50 mL volumetric flask, and dilute to the mark with primary water to prepare 100 mg / L standard stock solution 4; store it at 2-8℃ protected from light, with a shelf life of 1 month; S2.2 Preparation of mixed standard working solution Transfer equal volumes of standard stock solution 1 and standard stock solution 2 into volumetric flasks, add equal volumes of Sc internal standard solution (add 250µL of 1000mg / L Sc internal standard solution to 50mL of the solution), and serially dilute with 5wt% nitric acid aqueous solution to prepare mixed standard working solutions containing 5.00mg / L Sc element at concentrations of 0.10mg / L, 0.50mg / L, 1.0mg / L, 5.0mg / L, and 10.0mg / L.

[0040] Accurately transfer standard stock solution 3 and add the same volume of Sc internal standard solution (adding 250µL of 1000mg / L Sc internal standard solution to 50mL of the solution). Dilute with 5wt% nitric acid aqueous solution in a gradient and bring to volume to prepare single-standard Na gradient standard solutions containing 5.00mg / L Sc element at concentrations of 0.10mg / L, 0.50mg / L, 1.0mg / L, 5.0mg / L, and 10.0mg / L.

[0041] Accurately transfer standard stock solution 4 and add the same volume of Sc internal standard solution (add 250µL of 1000mg / L Sc internal standard solution to 50mL of the solution). Dilute with 5wt% nitric acid aqueous solution in a gradient and bring to volume to prepare single-standard Hg solutions containing 5.00mg / L Sc element at concentrations of 0.10mg / L, 0.50mg / L, 1.0mg / L, 2.0mg / L, and 5.0mg / L.

[0042] S3. On-machine testing The sample solution to be tested and the internal standard calibration solution were transferred to the ICP-OES instrument for detection to determine the content of the trace elements to be tested in the sample solution; the ICP test conditions of the ICP-OES are shown in Table 5, and the observation parameters of each trace element to be tested are shown in Table 6.

[0043] The trace elements to be tested include Al, As, Cd, Cr, Cu, Hg, K, Mg, Ni, Pb, Zn, Ca, Fe, and Na.

[0044] Table 5 ICP Test Conditions

[0045] Table 6 Observation parameters of each trace element to be measured

[0046] In step S3, the internal standard calibration solution and the sample solution to be tested are introduced into ICP-OES for measurement. The emission intensity of each trace element to be tested and the internal standard Scandium are measured separately. A standard curve is established using the formula "concentration of trace element to be tested - emission intensity of trace element to be tested / emission intensity of scandium internal standard". The emission intensity ratio of each trace element in the sample solution to that of the scandium internal standard is substituted into the standard curve to calculate the concentration of each trace element in the sample.

[0047] Furthermore, the content of each trace element in the electrolyte sample to be tested is calculated based on Equation (1).

[0048] Equation (1) In the formula: X i The content of the trace element to be tested in the sample is expressed in mg / kg. C The concentration of the trace element to be measured in the sample is obtained from the standard curve, and the unit is mg / L; C 0 represents the concentration of the analyte in the blank solution (the digestion solution of HNO3 without adding the sample) obtained according to the standard curve, in mg / L. V The volume of the sample solution to be tested is determined in mL. This refers to the dilution factor of the sample solution to be tested. The mass of the electrolyte sample to be tested is expressed in grams.

[0049] Example 2 This example provides a method for detecting trace elements in electrolytes using ICP-OES, with the specific implementation method being the same as in Example 1; the difference is that the electrolyte sample to be tested is electrolyte sample 2.

[0050] Example 3 This example provides a method for detecting trace elements in electrolytes using ICP-OES, with the specific implementation method being the same as in Example 1; the difference lies in the following adjustments made to the instrument testing conditions.

[0051] Table 7 ICP Test Conditions

[0052] Blank comparison example This example provides a method for detecting trace elements in electrolytes using ICP-OES. The specific implementation method is the same as in Example 1; the difference is that the sample solution to be tested is a blank solution (using HNO3 without adding the digestion solution after sample digestion).

[0053] Comparative Example 1 This example provides a method for detecting trace elements in electrolyte using ICP-OES, with the specific implementation method being the same as in Example 1; the difference lies in the quantitative method for the content of trace elements in electrolyte sample 1.

[0054] Specifically: Based on a series of prepared standard solutions, the characteristic emission intensities of each standard solution were determined using ICP-OES. A standard curve was plotted with emission intensity as the ordinate and concentration as the abscissa, and a univariate linear regression equation was established. The standard curves for each trace element are shown below. Figure 1-14 The results showed that the correlation coefficients R of the standard curves of the 14 trace elements were all greater than 0.999, indicating that the peak area of ​​the 13 elements was proportional to their concentration within the linear range, and the linear relationship was good. The correlation coefficient R>0.999 showed that the standard curve fit was good.

[0055] Furthermore, the blank solution and the sample solution to be tested were introduced into ICP-OES for measurement, and the emission intensity of each trace element to be tested was measured and substituted into... Figure 1-14 The concentrations of each trace element in the sample to be tested are calculated from the standard curve.

[0056] Performance testing 1. Limit of detection The limits of detection were calculated based on the test results of the blank control examples (11 parallel samples). The instrument limit of detection (LOD=3σ) and the method limit of detection (MDL=50×LOD) were calculated using three times the standard deviation of the test results of the blank control examples. The results are shown in Table 8.

[0057] Table 8. Detection limits for each trace element

[0058] Table 8 shows that the detection limits of the method of the present invention are extremely low. The MDL of the trace elements Al, As, Cd, Cr, Cu, Hg, Mg, Ni, Pb, Zn and Na are all below 2 mg / kg, which can meet the requirements for detection and analysis of electrolytes. However, the detection limits of Fe, Ca and K are relatively high, at 4.377 mg / kg, 5.888 mg / kg and 21.095 mg / kg respectively, which cannot meet the detection requirements.

[0059] 2. Accuracy and precision The test results for Examples 1, 2, and 3 are shown in Tables 9, 10, and 11, respectively; the test results for Comparative Example 1 are shown in Table 12. Seven parallel samples were set up for each sample, and the data in the tables are the average values ​​of each parallel sample.

[0060] Among them, the sample background value is the result obtained by directly testing the sample without digestion treatment, and ND is the result that is below the detection limit and not detected.

[0061] The accuracy of the method is measured by the recovery rate after spiked loading, which is required to be in the range of 80-120%. The precision of the method is measured by the relative standard deviation (RSD) of 7 parallel samples. The lower the RSD, the higher the precision and repeatability of the method.

[0062] Table 9 Test results of electrolyte sample 1

[0063] Table 10 Test results of electrolyte sample 2

[0064] Table 11 Test results of electrolyte sample 1

[0065] Table 9 shows that the spiked recovery rate of electrolyte sample 1 containing 16 wt% lithium hexafluorophosphate ranges from 98% to 112%, and the RSD of each element is less than 8%, with the RSD of all elements except potassium (K) being less than 3%. Table 10 shows that the spiked recovery rate of electrolyte sample 2 containing 20 wt% lithium hexafluorophosphate ranges from 99% to 110%, and the RSD of each element is less than 6%, with the RSD of all elements except potassium (K) being less than 3%. Table 11 shows that the spiked recovery rate of electrolyte sample 1 containing 16 wt% lithium hexafluorophosphate ranges from 90% to 116%, and the RSD of each element is less than 8%, with the RSD of all elements except potassium (K) being less than 3%. These results demonstrate that the accuracy and precision of the detection method provided by this invention meet the requirements of relevant evaluation standards. The test conditions used in Example 1 are superior to those in Example 3.

[0066] Table 12 Test Results of Comparative Example 1 (Standard Curve Method)

[0067] The results in Table 12 show that, due to the high content of S and P elements in the electrolyte, the sample matrix effect is significant. When the conventional standard curve method (pure external standard method) is used for spiked recovery testing, the recovery rate of each element is generally less than 90%, which cannot meet the requirements for accurate quantitative analysis of trace elements in electrolyte samples.

[0068] In summary, the methodological verification results of the present invention are shown in Table 13.

[0069] Table 13 Methodology Validation and Evaluation Criteria

[0070] As shown in Table 13, the ICP-OES method established in this invention can achieve quantitative analysis of 14 trace elements in electrolyte, namely Al, As, Cd, Cr, Cu, Hg, K, Mg, Ni, Pb, Zn, Ca, Fe, and Na. Among them, except for Fe, Ca, and K, the method detection limits for the other 11 elements are ≤2 mg / kg, demonstrating excellent detection sensitivity.

Claims

1. A method for detecting trace elements in an electrolyte using ICP-OES, characterized in that, The method includes: S1. Sample pretreatment: Weigh the electrolyte sample to be tested, perform pretreatment by wet digestion, add Sc internal standard solution to the pretreated digestion solution to obtain the sample solution to be tested; S2. Preparation of internal standard calibration standard solution: Prepare a gradient concentration standard working solution containing the trace element to be measured, and add Sc internal standard solution to each gradient concentration standard working solution to obtain the internal standard calibration standard solution; S3. On-machine testing: Transfer the sample solution to be tested and the internal standard calibration solution to the ICP-OES for on-machine testing to determine the content of the trace element to be tested in the sample solution; The wet digestion process includes: taking the electrolyte sample to be tested and mixing it with HNO3, heating it at 105-130℃ for 0.5-2 hours to obtain the digestion solution; The trace elements to be tested include Al, As, Cd, Cr, Cu, Hg, Mg, Ni, Pb, Zn, and Na.

2. The method according to claim 1, characterized in that, The wet digestion process includes: taking the electrolyte sample to be tested and mixing it with HNO3, heating it at 120°C for 1 hour to obtain the digestion solution.

3. The method according to claim 1, characterized in that, The ratio of the electrolyte sample to HNO3 used is (0.1-0.5) g : (1-10) mL.

4. The method according to claim 3, characterized in that, The ratio of the electrolyte sample to HNO3 used was 0.2g:4mL.

5. The method according to claim 1, characterized in that, When preparing a gradient concentration standard working solution containing the trace element to be measured, gradient concentration standard working solutions for Na and Hg are prepared separately.

6. The method according to claim 1, characterized in that, The concentration of Sc in the internal standard calibration solution and the test sample solution is 1.00-10.00 mg / L.

7. The method according to claim 1, characterized in that, The electrolyte sample to be tested contains more than 10 wt% lithium hexafluorophosphate.

8. The method according to claim 1, characterized in that, The ICP-OES test conditions in step S3 include: High-frequency generator power 1-2kW; Plasma flow rate: 10.0-15.0 L / min; Auxiliary gas flow rate: 0.8-1.2 L / min; Atomizer flow rate: 0.5-1.0 L / min.

9. The method according to claim 1, characterized in that, In the method described, the LOD of each trace element is below 0.05 μg / mL, and the MDL is below 2 mg / kg.

10. An application of the ICP-OES method for detecting trace elements in electrolytes according to any one of claims 1-9, characterized in that, The method is applied in the field of new energy batteries.

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