Method for detecting fluorine-containing anions in lithium battery based on liquid chromatography mass spectrometry analysis

Abstract

The application discloses a fluorine-containing anion detection method in lithium batteries based on liquid chromatography mass spectrometry analysis, relates to the technical field of analytical chemistry, and mainly aims to solve the problems that the existing ion chromatography method has low sensitivity and poor selectivity, cannot meet the analysis requirements of complex matrix samples, is difficult to overcome matrix interference, influences the accuracy and reliability of identification results, and cannot comprehensively cover various inorganic and organic fluorine-containing anions in lithium batteries. The method comprises the following steps: performing pretreatment operation on a to-be-detected sample based on different sample types; performing solid-phase extraction operation on the to-be-detected sample after the pretreatment operation, and detecting fluorine-containing anions of the target detection object by means of a liquid chromatography mass spectrometry device to obtain a fluorine-containing anion chromatogram; and accurately quantifying the fluorine-containing anions in the sample by means of an analyte standard curve.

Description

Technical Field

[0001] This application relates to the field of analytical chemistry technology, and in particular to a method for detecting fluoride anions in lithium batteries based on liquid chromatography-mass spectrometry. Background Technology

[0002] Lithium-ion batteries are widely used in various fields. The incorporation of fluorine can improve the thermal stability of lithium-ion batteries. Therefore, fluoride anions are widely used in various battery components. During the production and disposal of lithium-ion batteries, if fluoride anions are released into the environment, they can pollute water and soil, and threaten the ecological environment and human health. Therefore, the identification of fluoride anions in lithium-ion batteries is of great significance.

[0003] Currently, existing methods for identifying fluoride anions in lithium batteries primarily focus on water and soil samples, typically employing ion chromatography. However, direct ion chromatography suffers from low sensitivity and poor selectivity, failing to meet the analytical needs of complex matrix samples. It also struggles to overcome matrix interference, impacting the accuracy and reliability of the identification results and failing to comprehensively cover all types of inorganic and organic fluoride anions in lithium batteries. Therefore, a method for detecting fluoride anions in lithium batteries based on liquid chromatography-mass spectrometry is urgently needed to address these issues. Summary of the Invention

[0004] In view of this, this application provides a method for detecting fluorine-containing anions in lithium batteries based on liquid chromatography-mass spectrometry analysis. The main purpose is to solve the problems of low sensitivity and poor selectivity of existing direct ion chromatography methods, which cannot meet the analysis needs of complex matrix samples, are difficult to overcome matrix interference, affect the accuracy and reliability of identification results, and cannot fully cover various inorganic and organic fluorine-containing anions in lithium batteries.

[0005] According to one aspect of this application, a method for detecting fluoride anions in lithium batteries based on liquid chromatography-mass spectrometry is provided, comprising: Preprocessing operations are performed on the samples to be tested based on different sample types; Solid-phase extraction was performed on the sample to be tested after pretreatment, and the fluorine-containing anion was detected by liquid chromatography-mass spectrometry to obtain a chromatogram of fluorine-containing anions. The fluoride anions contained in the sample were accurately quantified by using the analyte standard curve.

[0006] Furthermore, before accurately quantifying the fluoride anions in the sample using the analyte standard curve, the method further includes: The standard fluorine-containing anions were detected by liquid chromatography-mass spectrometry to obtain a standard chromatogram, and the standard chromatogram was then subjected to chromatographic separation. Standard curves for analytes are generated based on the standard chromatograms after chromatographic classification.

[0007] Furthermore, the solid-phase extraction operation on the sample to be tested after pretreatment includes: The sample to be tested was subjected to solid-phase extraction using a pre-set solid-phase extraction column, wherein the pre-set solid-phase extraction column was sequentially filled with 5 mL of methanol and 5 mL of 0.2% acetic acid aqueous solution. After the sample to be tested is loaded into the column, it is washed with 5 mL of ultrapure water, followed by elution. The elution process uses 5 mL of methanol containing 5% ammonia solution.

[0008] Further, the chromatographic separation of the standard chromatogram includes: Chromatographic separation was performed using a reversed-phase ion-exchange column or a hydrophilic column. The mobile phase used for chromatographic separation is an aqueous solution containing pure acetonitrile and 40 mmol / L ammonium acetate, or any one of ammonium formate or ammonium bicarbonate.

[0009] Furthermore, the preprocessing operations for the test samples based on different sample types include: The sample to be tested is subjected to solvent extraction, the extracted sample is then acidified, and the acidified sample is then purified.

[0010] Furthermore, the sample to be tested includes inorganic analytes containing fluoride anions and organic analytes containing fluoride anions.

[0011] Furthermore, the preset solid-phase extraction column is a weak anion exchange SPE column or a strong anion exchange SPE column.

[0012] By employing the above technical solutions, the technical solutions provided in the embodiments of this application have at least the following advantages: This application provides a method for detecting fluoride anions in lithium batteries based on liquid chromatography-mass spectrometry (LC-MS). Compared with existing technologies, this application's embodiments involve pretreatment of the test samples based on different sample types; solid-phase extraction of the pretreated samples; and detection of the target analyte using LC-MS. The method accurately quantifies the target fluoride anion in the sample by combining the target analyte standard curve. The mixed-mode WAX ​​column solid-phase extraction achieves efficient separation of various lithium battery-related fluoride anions, simultaneously separating highly polar inorganic and organic fluoride anions, thereby improving the selectivity and separation effect of the analysis and significantly enhancing the accuracy of fluoride anion detection in lithium batteries.

[0013] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0014] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A flowchart of a method for detecting fluoride anions in lithium batteries based on liquid chromatography-mass spectrometry analysis, provided in an embodiment of this application, is shown. Figure 2 This paper presents a schematic diagram of the complete process of a method for analyzing fluorine-containing anions in lithium batteries according to an embodiment of this application. Figure 3 This paper illustrates a lithium battery-related fluorine-containing anion structure provided in an embodiment of this application. Figure 4 A chromatogram of a fluorine-containing anion provided in an embodiment of this application is shown. Detailed Implementation

[0015] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0016] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0017] This application provides a method for detecting fluorine-containing anions in lithium batteries based on liquid chromatography-mass spectrometry analysis, such as... Figure 1 As shown, the method includes: 101. Perform preprocessing operations on the samples to be tested based on different sample types.

[0018] In this embodiment, the sample to be tested is an environmental sample that may contain fluoride anions. The sample to be tested includes inorganic analytes containing fluoride anions and organic analytes containing fluoride anions. In some embodiments, the inorganic analytes include tetrafluoroborate (BF4). - ), hexafluorophosphate (PF6) - ), difluorophosphate (PO2F2) - ), hexafluoroarsenate (AsF6) - The organic compounds include difluorosulfonamide (FSI) and ultra-short chain PFAS (trifluoroacetic acid, trifluoromethanesulfonic acid, pentafluoropropionic acid, pentafluoropropanesulfonic acid and heptafluoropropanesulfonic acid). The embodiments in this application are not specifically limited.

[0019] To ensure the effectiveness of sample analysis and testing, the samples need to be cleaned. Different cleaning methods are used for different sample types. The steps for cleaning the samples based on different sample types include: The sample to be tested is subjected to solvent extraction, the extracted sample is then acidified, and the acidified sample is then purified.

[0020] Specifically, such as Figure 2 The sample pretreatment process shown can include environmental and biological samples. Environmental samples include surface water, soil, sediment, and plant samples, while biological samples include fish samples. This application embodiment does not make specific limitations.

[0021] In some embodiments, when purifying environmental samples, surface water samples (50 mL) are filtered through a 0.45 μm membrane and 10 ng of internal standard is added. Soil and sediment samples are extracted using a 1:1 (v / v) acetonitrile / water mixed solvent. 10 ng of internal standard is added to each 0.2-1 g sample, and after equilibration at room temperature for 6 hours, 4 mL of extraction solvent is added, followed by ultrasonic extraction for 30 minutes. The extraction process is repeated three times, and the supernatants are combined. After adjusting the pH to 3 with acetic acid, the supernatant is purified using the solid-phase extraction method described above. Plant samples are extracted using a 1:1 (v / v) acetonitrile / water mixed solvent. Specifically, 10 ng of internal standard is added to each 0.2-1 g sample, and after equilibration at room temperature for 6 hours, 4 mL of extraction solvent is added, followed by ultrasonic extraction for 15 minutes. The extraction process is repeated three times, and the supernatants are combined. After adjusting the pH to 3 with acetic acid, the supernatant is purified using the solid-phase extraction method described above.

[0022] In some embodiments, when purifying biological test samples, fish muscle samples are extracted using an acetonitrile / water (3:1, v / v) mixed solvent. Specifically, 10 ng of internal standard is added to each sample (approximately 0.1 g), and the sample is equilibrated at room temperature for 6 hours. Subsequently, the sample is treated with 4 mL of extraction solvent under ultrasonic conditions for 30 minutes. The extraction process is repeated three times, and the supernatants are combined and concentrated to below 2 mL. 10 mL of ultrapure water is added, and the solution is acidified to pH 3 with acetic acid. Finally, the solution is concentrated using the same SPE procedure described above. The internal standard is... 13 C2-Trifluoroacetic acid ( 13 C2-TFA), 13C4-perfluorobutyric acid (PFA) 13 C4-PFBA), 13 C5-Perfluorovaleric acid ( 13 C5-PFPeA), 13 C3-Perfluorobutanesulfonic acid ( 13 C3-PFBS).

[0023] 102. After cleaning, the sample to be tested is subjected to solid-phase extraction, and the target analyte is detected by liquid chromatography-mass spectrometry to obtain a chromatogram of fluorine-containing anions.

[0024] In this embodiment of the application, in order to better detect fluoride-containing anions by liquid chromatography-mass spectrometry, solid phase extraction is performed on the sample to be tested after pretreatment.

[0025] In another embodiment of this application, for further definition and explanation, the step of performing solid-phase extraction on the sample to be tested after pretreatment includes: The sample to be tested was subjected to solid-phase extraction using a pre-set solid-phase extraction column. After the sample to be tested is loaded into the column, the sample is eluted.

[0026] The pre-set solid-phase extraction column was eluted sequentially with 5 mL of methanol and 5 mL of 0.2% acetic acid aqueous solution, and the elution operation was performed using 5 mL of methanol containing 5% ammonia aqueous solution. The pre-set solid-phase extraction column was either a weak anion exchange SPE column or a strong anion exchange SPE column.

[0027] In an example of a solid-phase extraction operation, such as Figure 2As shown, solid-phase extraction (SPE) can be performed using a WAX solid-phase extraction column (Bond ElutPFAS WAX, 6 mL, 200 mg; Agilent Technologies, USA). The WAX ​​column was pretreated sequentially with 5 mL of methanol and 5 mL of 0.2% acetic acid aqueous solution. After loading the sample pretreatment solution into the column, it was washed with 5 mL of deionized water. The target analyte was eluted with 5 mL of methanol containing 5% ammonia aqueous solution, and then slowly dried under nitrogen to a final volume of 1 mL. The 1 mL concentrate was then centrifuged to extract 0.5 mL of the supernatant for analysis.

[0028] It should be noted that, due to the strong polarity and negative charge of the analyte, the sample can be stably and efficiently ionized in aqueous solution using electrospray ionization (ESI) mode. Inorganic and organic fluoride-containing anions can generate characteristic fragment ions under collision-induced dissociation, thus enabling qualitative and quantitative analysis in multiple reaction monitoring (MRM) mode. (Except for BF4) - Except for TFA, all analytes were monitored using two parent ion-daughter ion pairs, which produce only F. - (m / z = 19) or CF3 - (m / z = 19) fragments. Considering the high polarity of these anions, traditional reversed-phase chromatography columns cannot provide sufficient retention and good separation. After solid-phase extraction, the target analyte is detected for fluorine-containing anions using liquid chromatography-mass spectrometry (LC-MS / MS) to obtain a chromatogram of fluorine-containing anions. Preferably, the LC-MS / MS is coupled with a TSQ-Quantiva triple quadrupole mass spectrometer, but high-resolution mass spectrometry such as LC-Orbitrap or LC-QTOF can also be used. The mass spectrometer is equipped with an electrospray ionization source; specific limitations are not made in the embodiments described in this application.

[0029] 103. Accurately quantify the fluoride anions contained in the sample by using the analyte standard curve.

[0030] In this embodiment, before testing the sample, an internal standard of known concentration is added to both the standard solution and the sample to be tested. After obtaining the fluoride anion chromatogram, the detection result of the fluoride anion is generated based on the peak area (or peak height) ratio of the fluoride anion to the internal standard, combined with a pre-established internal standard curve. The internal standard curve is obtained by plotting the concentration ratio of the target analyte to the internal standard in the standard solution using the response ratio (peak area ratio or peak height ratio) to the internal standard.

[0031] In another embodiment of this application, for further definition and explanation, before the step of accurately quantifying the fluoride anions contained in the sample using an analyte standard curve, the method further includes: The standard solution and internal standard containing fluoride anion of known concentration were detected by liquid chromatography-mass spectrometry to obtain standard chromatographic data. The standard chromatographic data were then subjected to chromatographic separation and mass spectrometric signal extraction to obtain the characteristic peaks of the target fluoride anion and internal standard. Based on chromatographic separation and mass spectrometry detection results, the response ratio of fluoride anions to internal standards in each standard solution was calculated, and an internal standard curve was established using the response ratio and the corresponding fluoride anion concentration for subsequent quantitative analysis of fluoride anions in samples. To use the standard curve as the analytical basis for fluoride anion chromatograms, standard fluoride anions were detected using liquid chromatography-mass spectrometry (LC-MS / MS) to obtain standard chromatograms, which were then subjected to chromatographic separation. Specifically, 12 lithium battery fluoride anion standards were prepared into mixed standard working solutions ranging from 0.1 to 100 ng / mL, and 10 µL of four internal standard mixed solutions, each with a concentration of 10 ng / mL, were added to each solution. Further, LC-MS / MS was used for determination, and a calibration curve was constructed by plotting the peak area ratio of the standard to the internal standard against the corresponding concentration ratio. The specific method used could be least squares linear or quadratic regression, depending on the compound characteristics; this embodiment does not specify a particular method. The calibration range was 0.1-100 ng / mL, and all correlation coefficients (R²) were used. 2 The values ​​all exceeded 0.999, indicating excellent linearity. The limits of detection (LOD) of the standards were 0.01~0.03 ng / mL.

[0032] In another embodiment of this application, for further definition and explanation, the step of performing chromatographic separation on the standard chromatogram includes: Chromatographic separation is performed using a reversed-phase ion-exchange column or a hydrophilic column.

[0033] The mobile phase used for chromatographic separation is an aqueous solution containing pure acetonitrile and 40 mmol / L ammonium acetate, or any one of ammonium formate or ammonium bicarbonate. The column temperature is 30 °C, and the flow rate is set to 0.8 mL / min. The injection volume of standard solution and sample is 5 µL.

[0034] In some embodiments, such as Figure 3 The lithium battery-related fluorine anion structure diagram shown below, after performing steps 101-103, yields the following result: Figure 4 The chromatogram of fluorine-containing anions is shown.

[0035] This application provides a method for detecting fluoride anions in lithium batteries based on liquid chromatography-mass spectrometry (LC-MS). Compared with existing technologies, this application pre-processes the test samples according to different sample types; performs solid-phase extraction on the pre-processed test samples; and detects the target analytes using LC-MS to obtain fluoride anion chromatograms. It accurately quantifies the fluoride anions in the samples using analyte standard curves. The mixed-mode WAX ​​column solid-phase extraction achieves efficient separation of various lithium battery-related fluoride anions, simultaneously separating highly polar inorganic and organic fluoride anions, thereby improving the selectivity and separation effect of the analysis and significantly enhancing the accuracy of fluoride anion detection in lithium batteries.

[0036] Obviously, those skilled in the art should understand that the modules or steps of this application described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using computer-executable program code, thereby storing them in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those presented here, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, this application is not limited to any particular combination of hardware and software.

[0037] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for detecting fluoride anions in lithium batteries based on liquid chromatography-mass spectrometry, characterized in that, include: Preprocessing operations are performed on the samples to be tested based on different sample types; Solid-phase extraction was performed on the sample to be tested after pretreatment, and the fluorine-containing anion was detected by liquid chromatography-mass spectrometry to obtain a chromatogram of fluorine-containing anions. The fluoride anions contained in the sample were accurately quantified by using the analyte standard curve.

2. The method according to claim 1, characterized in that, Before accurately quantifying the fluoride anions in the sample using an analyte standard curve, the method further includes: The standard fluorine-containing anions were detected by liquid chromatography-mass spectrometry to obtain a standard chromatogram, and the standard chromatogram was then subjected to chromatographic separation. Standard curves for analytes are generated based on the standard chromatograms after chromatographic classification.

3. The method according to claim 2, characterized in that, The solid-phase extraction operation on the sample to be tested after pretreatment includes: The sample to be tested was subjected to solid-phase extraction using a pre-set solid-phase extraction column, wherein the pre-set solid-phase extraction column was sequentially filled with 5 mL of methanol and 5 mL of 0.2% acetic acid aqueous solution. After the sample to be tested is loaded into the column, it is washed with 5 mL of ultrapure water and then eluted. The elution operation uses 5 mL of methanol containing 5% ammonia solution.

4. The method according to claim 3, characterized in that, The chromatographic separation of the standard chromatogram includes: Chromatographic separation was performed using a reversed-phase ion-exchange column or a hydrophilic column. The mobile phase used for chromatographic separation is an aqueous solution containing pure acetonitrile and 40 mmol / L ammonium acetate, or any one of ammonium formate or ammonium bicarbonate.

5. The method according to claim 4, characterized in that, The cleaning operation for the test samples based on different sample types includes: When the sample type is environmental, the sample to be tested is extracted with solvent and then purified. When the sample type is biological, the sample to be tested is subjected to solvent extraction, the extracted sample to be tested is acidified, and the acidified sample to be tested is purified.

6. The method according to any one of claims 1-5, characterized in that, The test samples include inorganic analytes containing fluoride anions and organic analytes containing fluoride anions.

7. The method according to claim 6, characterized in that, The preset solid-phase extraction column is a weak anion exchange SPE column or a strong anion exchange SPE column.

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