Rapid detection method for trace chloride ions in synthetic silicon dioxide and application of rapid detection method

Abstract

The invention discloses a rapid detection method for trace chloride ions in synthetic silicon dioxide and application of the rapid detection method. The rapid detection method for the trace chloride ions in the synthetic silicon dioxide comprises the processes of cleaning a sample dissolving tank, preparing a sample solution, preparing a standard chloride ion solution, detecting by ion chromatography, analyzing a test result, determining the content of the chloride ions in the synthetic silicon dioxide and the like. According to the method, volatilization of the chloride ions and the solvent is prevented, no extra cosolvent needs to be added, the method has the advantages of being easy to operate, short in consumed time, high in measurement precision, accurate in content measurement and the like, and an important sample treatment and detection means is provided for measurement of the concentration of the chloride ions in the ultra-pure synthetic silicon dioxide.

Description

Technical Field

[0001] The invention relates to the technical field of trace chloride ion detection, and in particular to a method for rapid detection of trace chloride ions in synthetic silicon dioxide and application thereof. Background Art

[0002] Silicon dioxide (SiO2), as a hard, high temperature resistant, corrosion resistant and chemically stable inorganic compound, is widely used in glass, optical fiber, silicone resin and semiconductor fields. In particular, ultra-high purity SiO2 is a key basic material for high-tech industries such as semiconductors, photovoltaics and cutting-edge optics, and has an important strategic position. Among them, SiO2 prepared by chemical synthesis using silicon-containing compounds as raw materials has a higher purity than purified SiO2, and is the most promising means to meet the future demand for ultra-high purity SiO2 in related industries.

[0003] At present, the main chemical synthesis method is to use chlorosilane as raw material, burn it in a hydrogen-oxygen flame to directly generate it or react with water or alcohol in the liquid phase to generate an intermediate, and then obtain SiO2 powder through subsequent treatment. Due to the presence of chlorine in the raw material, it is inevitable that a certain amount of chloride ions will remain in the SiO2 generated by the above method. The residual chloride ions may cause corrosion of the product and other adverse effects. Especially when used to manufacture crucibles for semiconductors and photovoltaics, trace chloride ion impurities, generally at the ppm level, may cause crucible crystallization and bubble generation, and even escape during long-term high-temperature use to affect product quality. Therefore, it is particularly important to accurately quantify trace chloride ion impurities in SiO2.

[0004] At present, there is no corresponding standard method in China for the analysis and detection of trace chloride ions in SiO2. There are four main methods in the relevant literature and patent technical solutions that can be consulted, namely, silver nitrate colorimetry, chloride ion selective electrode method, mercury salt titration method and ion chromatography. Among them, the silver nitrate colorimetry and mercury salt titration methods not only use toxic chemical reagents but also have low detection accuracy, which cannot meet the requirements of accurate determination of chloride ions in ultra-high purity SiO2. Compared with the chloride ion selective electrode method, ion chromatography has a lower detection limit and smaller relative error [Reference 1].

[0005] Although ion chromatography has been used to detect chloride ions, the detection objects are mainly solutions or solid leachates [References 2-4], and there are few studies on the determination of chloride ions in insoluble SiO2. [Reference 5] SiO2 was dissolved in a fluororesin beaker by heating a NaOH aqueous solution, and then the pH was adjusted and tested by ion chromatography. Although this operation can achieve complete dissolution of SiO2, the volatilization of chloride ions and solvents during the heating process will affect the determination of the chlorine content. At the same time, the alcohol cosolvent added to dissolve the hydrophobic SiO2 and the nitric acid added to adjust the pH will reduce the accuracy of ion chromatography. [Reference 6] The problem of chloride ion volatilization was solved by dissolving quartz glass in a hydrothermal reactor, and the chlorine content in quartz glass was measured with high precision and accuracy. However, the dissolution time is too long (24-72 h) and it needs to pass through an ion exchange column, which cannot meet the needs of rapid analysis. At the same time, the current ion chromatography for the establishment of the standard curve in the detection of trace chlorine does not exclude the influence of the background peak area, which will significantly affect the fitted standard curve and bring great errors to the determination of trace chlorine content. In addition, since the chlorine content in the sample to be tested is low, the container must be kept clean and no foreign impurities can be introduced. How to effectively clean the container and eliminate the interference of impurities in the determination of chlorine content is one of the keys generally ignored in the prior art.

[0006]

Document 1

[0007] [Document 2] Specification of Chinese Patent Application Publication No. 102914600.

[0008]

Document 3

[0009] [Document 4] Specification of Chinese Patent Application Publication No. 102652110.

[0010]

Document 5

[0011]

Document 6

[0012] In view of the above technical problems and the shortcomings in the art, the present invention provides a method for rapid detection of trace chloride ions in synthetic silica and its application. The present invention is a rapid detection technology for trace chloride ions in poorly soluble solids, in particular, a technology for determining the concentration of trace chloride ions in synthetic silica by ion chromatography.

[0013] The present invention is dedicated to preparing a sample solution by simply heating an alkaline solution to completely dissolve the synthetic silica, and then accurately determining the chloride ion content in the synthetic silica by ion chromatography. Through the above technical method, the use of complex reagents is avoided, the operation process is simplified, the time consumption is short, and the rapid and high-precision detection of chloride ions is achieved.

[0014] The invention discloses a rapid detection method for trace chloride ions in synthetic silica, comprising the processes of cleaning a sample dissolving tank, preparing a sample solution, preparing a standard chloride ion solution, detecting by ion chromatography, analyzing the test results and determining the chloride ion content in the synthetic silica.

[0015] The specific technical solutions are as follows: A rapid detection method for trace chloride ions in synthetic silicon dioxide, comprising: Cleaning the sample dissolving tank: Each time before using the sample dissolving tank to dissolve synthetic silica, the sample dissolving tank is subjected to ultrasonic cleaning, high-temperature pickling, high-temperature water washing and drying operations in sequence; the material of the sample dissolving tank is polytetrafluoroethylene PFA; the ultrasonic cleaning time is 5-10 minutes, and the sample dissolving tank is filled with water during the ultrasonic cleaning process; the temperature of high-temperature pickling is 125-135°C (preferably 130°C), the time is 180-200 minutes, and the pickling solution used is a mixed solution of nitric acid and water in a volume ratio of 0.5-1:1; the temperature of high-temperature water washing is 125-135°C (preferably 130°C), and the time is 180-200 minutes; the volume of the pickling solution used for high-temperature pickling and the water used for high-temperature water washing are not less than 2 / 3 of the volume of the sample dissolving tank; Prepare the sample solution: accurately weigh the synthetic silica and place it in a cleaned sample dissolving tank, add an alkaline aqueous solution, seal and heat to digest to obtain a colorless and clear sample solution; the temperature of the sealed heating digestion is 100-120°C, and the time is 20-180 min, for example, 40 min, 60 min, 100 min, etc.; Preparation of standard chloride ion solutions: prepare multiple standard chloride ion solutions of the same volume and with a certain concentration gradient; Ion chromatography detection: The prepared sample solution and standard chloride ion solution were measured by ion chromatography, and the characteristic peak area of ​​chloride ion was recorded; Analysis of test results: Use the characteristic peak area of ​​chloride ions of the standard chloride ion solution and the corresponding chloride ion concentration to draw a standard curve. The equation of characteristic peak area of ​​chloride ions and chloride ion concentration obtained by linear fitting is as follows: S'=a+b×C, where: S' represents the characteristic peak area of ​​chloride ions (in μs·min), and the characteristic peak area of ​​chloride ions S' is the value after deducting the background peak area. The background peak area is the characteristic peak area of ​​chloride ions measured by a standard chloride ion solution with a chloride ion of 0 ppm. C is the chloride ion concentration of the standard chloride ion solution (in mg / L), and a and b are standard curve fitting constants; Determine the chloride ion content in synthetic silica: Calculate the actual chloride ion characteristic peak area S in the sample solution: S=S1-S0, where: S1 represents the chloride ion characteristic peak area of ​​the sample solution (in μs·min), S0 represents the chloride ion characteristic peak area of ​​the blank solution (in μs·min); the difference between the blank solution and the sample solution is that no synthetic silica is added to the blank solution, and the rest are the same; Substitute the actual chloride ion characteristic peak area of ​​the sample solution into the fitted equation S'=a+b×C to obtain the chloride ion concentration in the sample solution; The chloride ion content in the synthetic silica was calculated based on the chloride ion concentration in the sample solution.

[0016] The inventor found in the research process that the sample dissolving tank made of PFA material is transparent, which is convenient for observing whether the synthetic silica is completely digested. However, if the PFA material is not fully cleaned during repeated use and detection, there will be impurities that affect the accuracy of trace chloride ion determination. These impurities may come from the residues of raw materials, medicines and other substances during the digestion process. Experiments have found that simple water washing cannot completely clean impurities. If hydrofluoric acid is used, fluorine ions are difficult to remove, which will interfere with subsequent ion chromatography detection, while hydrochloric acid will introduce chloride ions, which will further increase the error of chloride ion determination. Based on this, the present invention proposes that each time before using the sample dissolving tank, ultrasonic cleaning, high-temperature acid washing, and high-temperature water washing with specific requirements and parameter conditions are used to treat the sample dissolving tank to avoid the influence of impurities.

[0017] Subsequently, the present invention realizes rapid (no more than 3 h) heating and dissolution of synthetic silicon dioxide powder in a sample dissolving tank under the action of an alkaline solution, and prepares a clear liquid sample.

[0018] In addition, the present invention also adopts a data processing method of subtracting the background peak to draw a corresponding standard curve, which solves the problem of inaccurate low-content values ​​caused by the background peak area. The present invention has found that if the data processing method of subtracting the background peak proposed by the present invention is not adopted, when multiple standard chloride ion solutions are prepared by gradient dilution of NaOH solutions with different pH values ​​and the corresponding standard curves are drawn using these standard chloride ion solutions, the chloride ion concentrations of the same sample calculated according to these standard curves vary greatly, which leads to inaccurate trace chloride ions in the synthetic silica finally detected.

[0019] In summary, the method of the present invention prevents the volatilization of chloride ions and solvents and does not require the addition of additional co-solvents. It has the advantages of easy operation, short time consumption, high measurement accuracy and accurate content determination, and provides an important sample processing and detection method for the determination of chloride ion concentration in ultra-high purity synthetic silica.

[0020] In some embodiments, in the method for rapid detection of trace chloride ions in synthetic silica, the volume of the sample dissolution tank can be 60-80 mL.

[0021] In some embodiments, in the method for rapid detection of trace chloride ions in synthetic silica, the alkaline aqueous solution may be a sodium hydroxide aqueous solution, the concentration of sodium hydroxide in the sodium hydroxide aqueous solution may be 0.2-1 mol / L, and may further be 0.5-1 mol / L, for example, 0.4 mol / L, 0.8 mol / L, etc., the amount of the alkaline aqueous solution may be 30%-45% of the volume of the sample dissolving tank (for example, the amount of the alkaline aqueous solution may be 20-25 mL, etc.), and the ratio of the added mass of synthetic silica to the sample dissolving tank to the volume of the alkaline aqueous solution is (0.45-0.60 g):(20-25 mL).

[0022] In some embodiments, the method for rapid detection of trace chloride ions in synthetic silica is as follows: sealed heating digestion obtains a colorless and clear sample solution, which is then cooled to room temperature and filtered with a 0.22-micron nylon filter membrane, the first 2-3 mL of filtrate is discarded, and the remaining filtered sample solution is used for ion chromatography detection.

[0023] In some embodiments, in the method for rapid detection of trace chloride ions in synthetic silica, the synthetic silica may be hydrophilic silica and / or hydrophobic silica.

[0024] In some embodiments, the method for rapid detection of trace chloride ions in synthetic silica can be performed by gradient dilution of a NaOH solution to obtain multiple standard chloride ion solutions of the same volume and with a certain concentration gradient.

[0025] In some embodiments, the method for rapid detection of trace chloride ions in synthetic silica, the preparation of multiple standard chloride ion solutions of the same volume and with a certain concentration gradient may specifically include: diluting a standard chloride ion solution with a chloride ion concentration of 50 μg / mL (ppm) with a NaOH solution in a gradient manner to obtain multiple standard chloride ion solutions with a chloride ion concentration of 0-5 mg / L gradient distribution and the same volume. For example, 10 mL, 6 mL, 2 mL, 1 mL, 0.6 mL, 0.2 mL and 0 mL of a 50 μg / mL (ppm) standard chloride ion solution can be accurately measured in a 100 mL volumetric flask, fixed to volume with a NaOH solution, and shaken to prepare chloride ion standard solutions of different concentrations.

[0026] In some embodiments, in the method for rapid detection of trace chloride ions in synthetic silica, the pH of the NaOH solution may be 11.5-12.5.

[0027] In some embodiments, in the method for rapid detection of trace chloride ions in synthetic silica, the pH of the sample solution used for ion chromatography detection may be 11-13, and further may be 11.5-12.5.

[0028] In some embodiments, the method for rapid detection of trace chloride ions in synthetic silica uses an ion chromatograph to perform the ion chromatography detection. Specifically, the sample solution and the standard chloride ion solution can be respectively injected into the ion chromatograph through an injection needle, the ion chromatograph test program is started, and the corresponding chromatographic curve is obtained after waiting for a period of time, and the characteristic peak area of ​​the chloride ion is recorded.

[0029] In some embodiments, the ion chromatography test conditions of the method for rapid detection of trace chloride ions in synthetic silica may include: assembling an anion suppressor, the suppressor type is AERS-4 mm, and the suppressor current is 50 mA; using an AS19 separation column and an AG19 guard column, the column model is 4 mm × 250 mm; the eluent is 50 mmol / L KOH solution; the column box temperature is 30°C; and the injection volume is 25 μL.

[0030] In some embodiments, in the method for rapid detection of trace chloride ions in synthetic silica, the standard curve graph uses the chloride ion characteristic peak area of ​​the standard chloride ion solution as the ordinate and the chloride ion concentration as the abscissa.

[0031] In some embodiments, the method for rapid detection of trace chloride ions in synthetic silica, the method for calculating the chloride ion content in synthetic silica according to the chloride ion concentration in the sample solution may specifically include: Substitute the chloride ion concentration in the sample solution into the following formula to calculate the chloride ion content in the synthetic silica: w=c×v / M / 1000, where: w represents the chloride ion content in the synthetic silica, in mg / Kg (ppm), c represents the chloride ion concentration in the sample solution, in mg / L, v represents the volume of the sample solution, in L, and M represents the mass of the synthetic silica, in g.

[0032] The present invention also provides application of the rapid detection method in rapid detection of trace chloride ions in synthetic silicon dioxide.

[0033] Preferably, all chemical reagents used in the present invention are of premium grade purity or above, and the water used is 18.2 megohm grade ultrapure water.

[0034] In the present invention, the equation S'=a+b×C obtained by fitting is regarded as an effective working curve when the linear coefficient is above 0.999.

[0035] The purpose of the present invention is to achieve rapid and high-precision detection of the total amount of trace chloride ions in synthetic SiO2 at a lower detection limit without using complex reagents. Synthetic SiO2 is quickly dissolved by heating an alkaline aqueous solution in a closed sample dissolving tank to solve the problems of difficulty in completely releasing trace chloride ions in synthetic SiO2, interference from co-solvents, and possible overflow of chloride ions.

[0036] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention sequentially performs ultrasonic cleaning, high-temperature acid cleaning, and high-temperature water cleaning on the sample dissolving tank before dissolution, thereby avoiding errors caused by the introduction of impurities.

[0037] (2) The present invention uses sodium hydroxide solution without adding a co-solvent, and can achieve complete dissolution of the synthesized SiO2 by heating it for a short time in a closed PFA sample dissolution tank, thereby avoiding the influence caused by the additional addition of a co-solvent, overcoming the problem of possible volatilization of chloride ions during the digestion process, omitting the pH adjustment step, and making the operation simpler and faster.

[0038] (3) The present invention deducts the influence of the background peak when drawing the standard curve, thereby solving the problem of inaccurate low-content values ​​caused by the background peak area. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is the standard curve of chloride ion concentration after background subtraction (pH = 12.5).

[0040] Figure 2 This is the ion chromatogram of Example 1.

[0041] Figure 3 This is the ion chromatogram of Example 2.

[0042] Figure 4 is the standard curve of chloride ion concentration after background subtraction (pH = 11.5).

[0043] Figure 5 This is the ion chromatogram of Example 3.

[0044] Figure 6 The standard curve of chloride ion concentration without background subtraction (pH = 12.5).

[0045] Figure 7 This is the ion chromatogram of Example 5.

[0046] Figure 8 This is the ion chromatogram of Example 6.

[0047] Fig. 9 This is the ion chromatogram of Example 7.

[0048] Fig.10 This is the ion chromatogram of Example 8.

[0049] Fig.11 This is the ion chromatogram of Example 9.

[0050] Fig.12 The standard curve of chloride concentration without background subtraction (pH = 11.5).

[0051] Fig.13 This is the ion chromatogram of Example 11. DETAILED DESCRIPTION

[0052] The present invention will be further described below in conjunction with the accompanying drawings and specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0053] Unless otherwise specified, in the following examples, the volume of the sample dissolving tank is 60 mL and the material is polytetrafluoroethylene (PFA). Example 1

[0054] 1) Cleaning of the sample dissolving tank: Fill the sample dissolving tank with water and ultrasonicate for 5 minutes. Pour out the water and add 40 mL of nitric acid aqueous solution (the volume ratio of nitric acid to water is 1:1). Keep the temperature at 130℃ for 3 h. Pour out the nitric acid aqueous solution and add 40 mL of water and continue to keep the temperature at 130℃ for 3 h. Finally, dry the tank for later use.

[0055] 2) Preparation of sample solution: Accurately weigh 8 g of NaOH and dilute to 250 mL volumetric flask with ultrapure water to obtain 0.8 mol / L NaOH solution. Use an analytical balance to weigh the synthetic SiO2 powder numbered S-1 (hydrophilic, with a specific surface area of ​​150 m 2 / g, particle size is 7-40 nm). The weighed SiO2 powder is placed in a high temperature resistant sample dissolving tank, 20 mL of NaOH solution is measured in a reagent bottle, the seal is tightened, and it is placed on a constant temperature heating platform at 100°C for 30 min before being taken out. Cool to room temperature, use sterile injection to transfer 12 mL of solution, filter through a 0.22 μm nylon membrane filter, discard the first 2 mL of filtrate, and store the filtered solution in a PFA bottle. The sample solution to be tested with a pH value of 12.4 at 25°C is obtained by the above method. At the same pH, the solution prepared without adding SiO2 powder sample is the blank solution.

[0056] 3) Preparation of standard chloride ion solution: Accurately measure 10 mL, 6 mL, 2 mL, 1 mL, 0.6 mL, 0.2 mL and 0 mL of 50 μg / mL (ppm) standard chloride ion solution into a 100 mL volumetric flask, make up to volume with pH=12.5 NaOH aqueous solution, shake well to prepare standard solutions with chloride ion concentrations of 5 ppm, 3 ppm, 1 ppm, 0.5 ppm, 0.3 ppm, 0.1 ppm and 0 ppm, respectively.

[0057] 4) Ion chromatography detection: The solutions in steps 1) and 2) were detected using an ion chromatograph. The technical conditions of the ion chromatograph were as follows: equipped with an anion suppressor, the suppressor type was AERS-4 mm, and the suppressor current was 50 mA; AS19 separation column and AG19 guard column, the column model was 4 mm × 250 mm; the eluent was 50 mmol / L KOH solution; the column box temperature was 30°C; and the injection volume was 25 μL.

[0058] The measured chloride ion concentrations and the corresponding characteristic peak areas are shown in Tables 1 and 2. Figure 2 The ion chromatography test results of the sample solution (a) and the blank sample (b) of this example are shown.

[0059] Table 1 Standard chloride ion concentration and peak area

[0060] Table 2 Peak areas of sample solutions

[0061] 5) Test result analysis: With the standard chloride ion concentration as the horizontal axis and the peak area as the vertical axis, draw the chloride ion standard solution curve as shown in the figure below: Figure 1 , the fitting equation is shown in Formula 1.

[0062] S' / (μs·min) = 0.00412 + 0.2717 × C / (mg / L) Formula 1 Wherein, S' represents the characteristic peak area of ​​chloride ion after background deduction, C is the chloride ion concentration of the standard solution, and the linear coefficient is 0.9993.

[0063] 6) Calculation of chlorine concentration in the sample to be tested: First, the actual chloride ion characteristic peak area S in the sample solution to be tested is calculated using formula 2: S / (μs min) = S1 – S0 Formula 2 Wherein, S1 represents the characteristic peak area of ​​chloride ion of S-1 sample, and S0 represents the characteristic peak area of ​​chloride ion of blank solution.

[0064] Substituting the sample peak area of ​​0.354 and the blank solution peak area of ​​0.112 into Formula 2, the peak area of ​​S-1 sample was calculated to be 0.242. Subsequently, substituting the peak area of ​​S-1 into Formula 1, the corresponding chloride ion concentration c in the sample solution was obtained to be 0.8755 mg / L.

[0065] Finally, substitute the concentration into the following formula to calculate the chloride ion content w, w = c×v / M / 1000 Formula 3 Where: w – chloride ion content in SiO2 (ppm); c – Chloride ion concentration in the sample solution (mg / L); v – volume of the liquid to be tested (L); M – mass of SiO2 (g); Substitute the sample mass of 0.512 g and the volume of the test solution of 20 mL into Formula 3, and the chloride ion content in the S-1 sample is calculated to be 34.20 ppm. Example 2

[0066] 1) Cleaning of the sample dissolving tank: This part is consistent with Example 1.

[0067] 2) Preparation of sample solution: Accurately weigh 2 g of NaOH and dilute to a 250 mL volumetric flask with ultrapure water to obtain a 0.2 mol / L NaOH solution. Use an analytical balance to weigh the synthetic SiO2 powder numbered S-1. Place the weighed SiO2 powder in a high-temperature resistant sample dissolving tank, measure 20 mL of NaOH solution into the sample dissolving tank, seal it tightly, place it on a constant temperature heating table at 120°C and keep it warm for 20 min before taking it out. Cool to room temperature, use sterile injection to transfer 13 mL of solution, filter it through a 0.22 μm nylon membrane filter, discard the first 2 mL of filtrate, and store the filtered solution in a PFA bottle. The sample solution to be tested with a pH value of 11.4 at 25°C is obtained by the above method. At the same pH, the solution prepared without adding SiO2 powder sample is the blank solution.

[0068] 3) Preparation of standard chloride ion solution: Accurately measure 10 mL, 6 mL, 2 mL, 1 mL, 0.6 mL, 0.2 mL and 0 mL of 50 μg / mL (ppm) standard chloride ion solution into a 100 mL volumetric flask, make up to volume with pH=11.5 NaOH aqueous solution, shake well to prepare standard solutions with chloride ion concentrations of 5 ppm, 3 ppm, 1 ppm, 0.5 ppm, 0.3 ppm, 0.1 ppm and 0 ppm, respectively.

[0069] 4) Ion chromatography detection: The instrument parameter settings were consistent with those in Example 1. The measured chloride ion concentrations and the corresponding characteristic peak areas are shown in Tables 3 and 4. Figure 3 The ion chromatography test results of the sample solution (a) and the blank sample (b) of this example are shown.

[0070] Table 3 Standard chloride ion concentration and peak area

[0071] Table 4 Peak areas of sample solutions

[0072] 5) Test result analysis: With the standard chloride ion concentration as the horizontal axis and the peak area as the vertical axis, draw the chloride ion standard solution curve as shown in the figure below: Figure 4 , the fitting equation is shown in Formula 4; S' / (μs·min) = -0.011 + 0.2691 × C / (mg / L) Formula 4 Wherein, S' represents the characteristic peak area of ​​chloride ion after background subtraction, C is the chloride ion concentration of the standard solution, and the linear coefficient is 0.9995.

[0073] 6) Calculation of chlorine concentration in the sample to be tested: First, substitute the sample peak area of ​​0.285 and the blank solution peak area of ​​0.026 into Formula 2, and calculate the peak area of ​​the S-1 sample to be 0.259. Then, substitute the peak area of ​​S-1 into Formula 4, and the corresponding chloride ion concentration in the sample solution is 1.0033 mg / L. Finally, substitute the sample mass of 0.595 g and the volume of the test solution of 20 mL into Formula 3, and the chloride ion content in the S-1 sample is calculated to be 33.72 ppm. Example 3

[0074] 1) Cleaning of the sample dissolving tank: This part is consistent with Example 1.

[0075] 2) Preparation of sample solution: Accurately weigh 5 g of NaOH and dilute to a 250 mL volumetric flask with ultrapure water to obtain a 0.5 mol / L NaOH solution. Use an analytical balance to weigh the synthetic SiO2 powder numbered S-1. Place the weighed SiO2 powder in a high-temperature resistant sample dissolving tank, measure 20 mL of NaOH solution into the sample dissolving tank, seal it tightly, place it on a constant temperature heating table at 120°C for 30 min, and then take it out. Cool to room temperature, use sterile injection to transfer 12 mL of solution, filter it through a 0.22 μm nylon membrane filter, discard the first 2 mL of filtrate, and store the filtered solution in a PFA bottle. The sample solution to be tested with a pH value of 12.06 at 25°C is obtained by the above method. At the same pH, the solution prepared without adding SiO2 powder sample is the blank solution.

[0076] 3) Ion chromatography detection: The instrument parameters were set in the same manner as in Example 1. The measured chloride ion concentration and the corresponding characteristic peak area are shown in Table 5. Figure 5 The ion chromatography test results of the sample solution (a) and the blank sample (b) of this example are shown.

[0077] Table 5 Peak areas of sample solutions

[0078] 4) Calculation of chlorine concentration in the sample to be tested: First, substitute the sample peak area of ​​0.285 and the blank solution peak area of ​​0.085 into Formula 2, and calculate the peak area of ​​the S-1 sample to be 0.242. Then, substitute the peak area of ​​S-1 into Formula 1, and the corresponding chloride ion concentration in the sample solution is 0.8755 mg / L. Finally, substitute the sample mass of 0.500 g and the volume of the test solution of 20 mL into Formula 3, and the chloride ion content in the S-1 sample is calculated to be 35.02 ppm. Example 4

[0079] 1) Cleaning of the sample dissolving tank: This part is consistent with Example 1.

[0080] 2) Preparation of sample solution: This part is consistent with Example 1.

[0081] 3) Preparation of standard chloride ion solution: This part is consistent with Example 1.

[0082] 4) Ion chromatography detection: This part is consistent with Example 1. The measured chloride ion concentration and the corresponding characteristic peak area are shown in Table 1 and Table 6.

[0083] Table 6 Peak areas of sample solutions

[0084] 5) Test result analysis: With the standard chloride ion concentration as the horizontal axis and the peak area as the vertical axis, draw the chloride ion standard solution curve as shown in the figure below: Figure 6 , the fitting equation is shown in Formula 5; S' / (μs·min) = 0.11612 + 0.2717 × C / (mg / L) Formula 5 Wherein, S' represents the characteristic peak area of ​​chloride ion, C is the chloride ion concentration of the standard solution, and the linear coefficient is 0.9993.

[0085] 6) Calculation of chlorine concentration in the sample to be tested: First, substitute the sample peak area of ​​0.354 and the blank solution peak area of ​​0.112 into Formula 2, and calculate the peak area of ​​the S-1 sample to be 0.242. Then, substitute the peak area of ​​S-1 into Formula 5, and the corresponding chloride ion concentration in the sample solution is 0.4633 mg / L. Finally, substitute the sample mass of 0.512 g and the volume of the test solution of 20 mL into Formula 3, and the chloride ion content in the S-1 sample is calculated to be 18.09 ppm. Example 5

[0086] 1) Cleaning of the sample dissolving tank: Fill the sample dissolving tank with water and perform ultrasonic treatment for 5 minutes, then rinse it with ultrapure water several times, and finally dry it for later use.

[0087] 2) Preparation of sample solution: This part is consistent with Example 1.

[0088] 3) Preparation of standard chloride ion solution: This part is consistent with Example 1.

[0089] 4) Ion chromatography detection: This part is consistent with Example 1. The measured chloride ion concentration and the corresponding characteristic peak area are shown in Table 7. Figure 7 The ion chromatography test results of the sample solution (a) and the blank sample (b) of this example are shown.

[0090] Table 7 Peak areas of sample solutions

[0091] 5) Calculation of chlorine concentration in the sample to be tested: First, substitute the sample peak area of ​​0.368 and the blank solution peak area of ​​0.021 into Formula 2, and calculate the peak area of ​​the S-1 sample to be 0.347. Then, substitute the peak area of ​​S-1 into Formula 1, and the corresponding chloride ion concentration in the sample solution is 1.015 mg / L. Finally, substitute the sample mass of 0.518 g and the volume of the test solution of 20 mL into Formula 3, and the chloride ion content in the S-1 sample is calculated to be 39.20 ppm. Example 6

[0092] 1) Cleaning of the sample dissolving tank: This part is consistent with Example 1.

[0093] 2) Preparation of sample solution: Accurately weigh 2 g of NaOH and dilute to 250 mL volumetric flask with ultrapure water to obtain 0.2 mol / L NaOH solution. Use an analytical balance to weigh the synthetic SiO2 powder numbered S-2 (hydrophilic, with a specific surface area of ​​380 m 2 / g, particle size is 7-40 nm). The weighed SiO2 powder is placed in a high temperature resistant sample dissolving tank, 24 mL of NaOH solution is measured in the sample dissolving tank, the seal is tightened, and it is placed on a constant temperature heating platform at 120°C for 20 min before being taken out. After cooling to room temperature, 12.4 mL of the solution is transferred using a sterile injection solution, filtered through a 0.22 μm nylon membrane filter, the first 2 mL of the filtrate is discarded, and the filtered solution is stored in a PFA bottle. The sample solution to be tested with a pH value of 11.4 at 25°C is obtained by the above method. At the same pH, the solution prepared without adding SiO2 powder sample is the blank solution.

[0094] 3) Ion chromatography detection: The instrument parameter settings were consistent with those in Example 1. The measured chloride ion concentration and the corresponding characteristic peak area are shown in Table 8. Figure 8 The ion chromatography test results of the sample solution (a) and the blank sample (b) of this example are shown.

[0095] Table 8 Peak areas of sample solutions

[0096] 4) Calculation of chlorine concentration in the sample to be tested: First, substitute the sample peak area of ​​0.308 and the blank solution peak area of ​​0.112 into Formula 2, and calculate the peak area of ​​the S-2 sample to be 0.196. Then, substitute the peak area of ​​S-2 into Formula 4, and the corresponding chloride ion concentration in the sample solution is 0.7692 mg / L. Finally, substitute the sample mass of 0.522 g and the volume of the test solution of 24 mL into Formula 3, and the chloride ion content in the S-2 sample is calculated to be 35.36 ppm. Example 7

[0097] 1) Cleaning of the sample dissolving tank: This part is consistent with Example 1.

[0098] 2) Preparation of sample solution: Accurately weigh 8 g of NaOH and dilute to 250 mL volumetric flask with ultrapure water to obtain 0.8 mol / L NaOH solution. Use an analytical balance to weigh the synthetic SiO2 powder numbered S-3 (hydrophobic, with a specific surface area of ​​115 m 2 / g, particle size is 7-40 nm). The weighed SiO2 powder is placed in a high temperature resistant sample dissolving tank, 20 mL of NaOH solution is measured in the sample dissolving tank, the seal is tightened, and it is placed on a constant temperature heating platform at 100°C for 60 min before being taken out. After cooling to room temperature, 12 mL of the solution is transferred using a sterile injection solution, filtered through a 0.22 μm nylon membrane filter, the first 2 mL of the filtrate is discarded, and the filtered solution is stored in a PFA bottle. The sample solution to be tested with a pH value of 12.55 at 25°C is obtained by the above method. At the same pH, the solution prepared without adding SiO2 powder sample is the blank solution.

[0099] 3) Ion chromatography detection: The instrument parameter settings are consistent with those in Example 1. The measured chloride ion concentration and the corresponding characteristic peak area are shown in Table 9. Fig. 9 The ion chromatography test results of the sample solution (a) and the blank sample (b) of this example are shown.

[0100] Table 9 Peak areas of sample solutions

[0101] 4) Calculation of chlorine concentration in the sample to be tested: First, substitute the sample peak area of ​​0.376 and the blank solution peak area of ​​0.112 into Formula 2, and calculate the peak area of ​​the S-3 sample to be 0.264. Then, substitute the peak area of ​​S-3 into Formula 1, and the corresponding chloride ion concentration in the sample solution is 0.9565 mg / L. Finally, substitute the sample mass of 0.506 g and the volume of the test solution of 20 mL into Formula 3, and the chloride ion content in the S-3 sample is calculated to be 37.81 ppm. Example 8

[0102] 1) Cleaning of the sample dissolving tank: This part is consistent with Example 1.

[0103] 2) Preparation of sample solution: Accurately weigh 4 g of NaOH and dilute to a 250 mL volumetric flask with ultrapure water to obtain a 0.4 mol / L NaOH solution. Use an analytical balance to weigh the synthetic SiO2 powder numbered S-3. Place the weighed SiO2 powder in a high-temperature resistant sample dissolving tank, measure 20 mL of NaOH solution in the sample dissolving tank, seal it tightly, place it on a constant temperature heating table at 120°C and keep it warm for 40 min before taking it out. Cool to room temperature, use sterile injection to transfer 13 mL of solution, filter it through a 0.22 μm nylon membrane filter, discard the first 2 mL of filtrate, and store the filtered solution in a PFA bottle. The sample solution to be tested with a pH value of 11.63 at 25°C is obtained by the above method. At the same pH, the solution prepared without adding SiO2 powder sample is the blank solution.

[0104] 3) Ion chromatography detection: The instrument parameter settings were consistent with those in Example 1. The measured chloride ion concentration and the corresponding characteristic peak area are shown in Table 10. Fig.10 The ion chromatography test results of the sample solution (a) and the blank sample (b) of this example are shown.

[0105] Table 10 Peak areas of sample solutions

[0106] 4) Calculation of chlorine concentration in the sample to be tested: First, substitute the sample peak area of ​​0.366 and the blank solution peak area of ​​0.112 into Formula 2, and calculate the peak area of ​​the S-3 sample to be 0.254. Then, substitute the peak area of ​​S-3 into Formula 4, and the corresponding chloride ion concentration in the sample solution is 0.9848 mg / L. Finally, substitute the sample mass of 0.506 g and the volume of the test solution of 20 mL into Formula 3, and the chloride ion content in the S-3 sample is calculated to be 38.92 ppm. Example 9

[0107] 1) Cleaning of the sample dissolving tank: This part is consistent with Example 1.

[0108] 2) Preparation of sample solution: Accurately weigh 2 g of NaOH and dilute to a 250 mL volumetric flask with ultrapure water to obtain a 0.2 mol / L NaOH solution. Use an analytical balance to weigh the synthetic SiO2 powder numbered S-3. Place the weighed SiO2 powder in a high-temperature resistant sample dissolving tank, measure 20 mL of NaOH solution in the sample dissolving tank, seal it tightly, place it on a constant temperature heating table at 120°C and keep it warm for 120 min before taking it out. Cool to room temperature, use sterile injection to transfer 13 mL of solution, filter it through a 0.22 μm nylon membrane filter, discard the first 2 mL of filtrate, and store the filtered solution in a PFA bottle. The sample solution to be tested with a pH value of 11.48 at 25°C is obtained by the above method. At the same pH, the solution prepared without adding SiO2 powder sample is the blank solution.

[0109] 3) Ion chromatography detection: The instrument parameter settings were consistent with those in Example 1. The measured chloride ion concentration and the corresponding characteristic peak area are shown in Table 11. Fig.11 The ion chromatography test results of the sample solution (a) and the blank sample (b) of this example are shown.

[0110] Table 11 Peak areas of sample solutions

[0111] 4) Calculation of chlorine concentration in the sample to be tested: First, substitute the sample peak area of ​​0.296 and the blank solution peak area of ​​0.032 into Formula 2, and calculate the peak area of ​​the S-3 sample to be 0.264. Then, substitute the peak area of ​​S-3 into Formula 4, and the corresponding chloride ion concentration in the sample solution is 1.022 mg / L. Finally, substitute the sample mass of 0.518 g and the volume of the test solution of 20 mL into Formula 3, and the chloride ion content in the S-3 sample is calculated to be 39.46 ppm. Example 10

[0112] 1) Cleaning of the sample dissolving tank: This part is consistent with Example 1.

[0113] 2) Preparation of sample solution: This part is consistent with Example 8.

[0114] 3) Preparation of standard chloride ion solution: This part is consistent with Example 2.

[0115] 4) Ion chromatography detection: The instrument parameter settings were consistent with those in Example 1. The measured chloride ion concentrations and corresponding characteristic peak areas are shown in Tables 3 and 12.

[0116] Table 12 Peak areas of sample solutions

[0117] 5) Test result analysis: With the standard chloride ion concentration as the horizontal axis and the peak area as the vertical axis, draw the chloride ion standard solution curve as shown in the figure below: Fig.12 , the fitting equation is shown in Formula 6; S' / (μs·min) = 0.011 + 0.2691 × C / (mg / L) Formula 6 Wherein, S' represents the characteristic peak area of ​​chloride ion, C is the chloride ion concentration of the standard solution, and the linear coefficient is 0.9993.

[0118] 6) Calculation of chlorine concentration in the sample to be tested: First, substitute the sample peak area of ​​0.366 and the blank solution peak area of ​​0.112 into Formula 2, and calculate the peak area of ​​the S-3 sample to be 0.254. Then, substitute the peak area of ​​S-3 into Formula 6, and the corresponding chloride ion concentration in the sample solution is 0.9030 mg / L. Finally, substitute the sample mass of 0.506 g and the volume of the test solution of 20 mL into Formula 3, and the chloride ion content in the S-3 sample is calculated to be 35.69 ppm. Embodiment 11

[0119] 1) Cleaning of the sample dissolving tank: This part is consistent with Example 1.

[0120] 2) Preparation of sample solution: Accurately weigh 10 g of NaOH and dilute it to a 250 mL volumetric flask with ultrapure water to obtain a 1 mol / L NaOH solution. Use an analytical balance to weigh the synthetic SiO2 powder numbered S-4 (hydrophobic, with a specific surface area of ​​115 m 2 / g, particle size is 7-40 nm). The weighed SiO2 powder is placed in a high temperature resistant sample dissolving tank, 20 mL of NaOH solution is measured in the sample dissolving tank, the seal is tightened, and it is placed on a constant temperature heating platform at 120°C for 180 min before being taken out. After cooling to room temperature, 12.3 mL of the solution is transferred using a sterile injection solution, filtered through a 0.22 μm nylon membrane filter, the first 2 mL of the filtrate is discarded, and the filtered solution is stored in a PFA bottle. The sample solution to be tested with a pH value of 12.86 at 25°C is obtained by the above method. At the same pH, the solution prepared without adding SiO2 powder sample is the blank solution.

[0121] 3) Ion chromatography detection: The instrument parameter settings are consistent with those in Example 1, except that the test solution was diluted 10 times in this test. The measured chloride ion concentration and the corresponding characteristic peak area are shown in Table 13. Fig.13 The ion chromatography test results of the sample solution (a) and the blank sample (b) of this example are shown.

[0122] Table 13 Peak areas of sample solutions

[0123] 4) Calculation of chlorine concentration in the sample to be tested: First, substitute the sample peak area of ​​0.710 and the blank solution peak area of ​​0.112 into Formula 2, and calculate the peak area of ​​the S-4 sample to be 0.598. Then, substitute the peak area of ​​S-4 into Formula 1, and the corresponding chloride ion concentration in the sample solution is 2.186 mg / L. Finally, substitute the sample mass of 0.506 g and the volume of the test solution of 20 mL into Formula 3, and the chloride ion content in the S-4 sample is calculated to be 87.43 ppm.

[0124] The test data tables for each case are summarized as follows:

[0125] It can be seen from the results of Examples 1-3 of the S-1 sample and Examples 7-9 of the S-3 sample that the RSD of the sample measurement value of the determination method of the present invention is less than 10%, which meets the requirements of analysis and detection. Comparing the average values ​​of Examples 1-3 with the results of Example 4, it can be seen that the average value of the Cl content calculated using the standard curve with background subtraction is higher than the calculated value without background subtraction. In addition, the average values ​​of Examples 7-9 have the same trend compared with the results of Example 10. The results show that the standard curve affected by the background peak area value in the standard solution will affect the subsequent Cl content quantification, and the larger the background peak area value, the greater the influence on the calculation of the low content value.

[0126] By comparing the average values ​​of Examples 1-3 with the results of Example 5, it can be seen that the Cl content value finally obtained by the subsequent alkaline digestion after the sample dissolving tank is only washed with ordinary water is slightly higher than the average value of Examples 1-3, indicating that ordinary water washing cannot completely remove the attached Cl ions remaining on the inner wall of the sample dissolving tank. In addition, by comparing Examples 1-6 and 7-11, it is found that for the test of the Cl content in hydrophobic SiO2, the present invention can achieve complete digestion of SiO2 and accurate measurement of the chlorine content by appropriately extending the digestion time, increasing the digestion temperature and increasing the concentration of the alkali solution.

[0127] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for rapid detection of trace chloride ions in synthetic silicon dioxide, characterized in that: include: Cleaning the sample dissolving tank: Each time before using the sample dissolving tank to dissolve synthetic silica, the sample dissolving tank is subjected to ultrasonic cleaning, high-temperature pickling, high-temperature water washing and drying operations in sequence; the material of the sample dissolving tank is polytetrafluoroethylene PFA; the ultrasonic cleaning time is 5-10 minutes, and the sample dissolving tank is filled with water during the ultrasonic cleaning process; the temperature of high-temperature pickling is 125-135°C (preferably 130°C), the time is 180-200 minutes, and the pickling solution used is a mixed solution of nitric acid and water in a volume ratio of 0.5-1:1; the temperature of high-temperature water washing is 125-135°C (preferably 130°C), and the time is 180-200 minutes; the volume of the pickling solution used for high-temperature pickling and the water used for high-temperature water washing are not less than 2 / 3 of the volume of the sample dissolving tank; Prepare sample solution: accurately weigh synthetic silica and place it in a cleaned sample dissolving tank, add alkaline aqueous solution, seal and heat to digest to obtain a colorless and clear sample solution; the temperature of the sealed heating digestion is 100-120°C and the time is 20-180min; Preparation of standard chloride ion solutions: prepare multiple standard chloride ion solutions of the same volume and with a certain concentration gradient; Ion chromatography detection: The prepared sample solution and standard chloride ion solution were measured by ion chromatography, and the characteristic peak area of ​​chloride ion was recorded; Analysis of test results: The characteristic peak area of ​​chloride ions of the standard chloride ion solution and the corresponding chloride ion concentration were used to draw a standard curve. The equation of the characteristic peak area of ​​chloride ions and the chloride ion concentration was obtained by linear fitting as follows: S'=a+b×C, where: S' represents the characteristic peak area of ​​chloride ions, and the characteristic peak area of ​​chloride ions S' is the value after deducting the background peak area. The background peak area is the characteristic peak area of ​​chloride ions measured by a standard chloride ion solution with a chloride ion of 0 ppm. C is the chloride ion concentration of the standard chloride ion solution, and a and b are standard curve fitting constants; Determine the chloride ion content in synthetic silica: Calculate the actual chloride ion characteristic peak area S in the sample solution: S=S1-S0, where: S1 represents the chloride ion characteristic peak area of ​​the sample solution, S0 represents the chloride ion characteristic peak area of ​​the blank solution; the difference between the blank solution and the sample solution is only that no synthetic silica is added to the blank solution, and the rest are the same; Substitute the actual chloride ion characteristic peak area of ​​the sample solution into the fitted equation S'=a+b×C to obtain the chloride ion concentration in the sample solution; The chloride ion content in the synthetic silica was calculated based on the chloride ion concentration in the sample solution.

2. The rapid detection method for trace chloride ions in synthetic silicon dioxide according to claim 1, characterized in that: The volume of the sample dissolving tank is 60-80 mL.

3. The rapid detection method for trace chloride ions in synthetic silicon dioxide according to claim 1 or 2, characterized in that: The alkaline aqueous solution is a sodium hydroxide aqueous solution, the concentration of sodium hydroxide in the sodium hydroxide aqueous solution is 0.2-1 mol / L, the amount of the alkaline aqueous solution is 30%-45% of the volume of the sample dissolving tank, and the ratio of the added mass of synthetic silicon dioxide to the volume of the alkaline aqueous solution in the sample dissolving tank is (0.45-0.60 g):(20-25 mL).

4. The rapid detection method for trace chloride ions in synthetic silicon dioxide according to claim 1, characterized in that: The synthetic silica is hydrophilic silica and / or hydrophobic silica.

5. The rapid detection method for trace chloride ions in synthetic silicon dioxide according to claim 1, characterized in that: Use NaOH solution to dilute in gradients to obtain multiple standard chloride ion solutions of the same volume and with a certain concentration gradient.

6. The rapid detection method for trace chloride ions in synthetic silicon dioxide according to claim 5, characterized in that: The preparation of multiple standard chloride ion solutions of the same volume and with a certain concentration gradient specifically includes: diluting a standard chloride ion solution with a chloride ion concentration of 50 μg / mL with a NaOH solution in a gradient manner to obtain multiple standard chloride ion solutions with a chloride ion concentration gradient distribution of 0-5 mg / L and the same volume.

7. The rapid detection method for trace chloride ions in synthetic silicon dioxide according to claim 5 or 6, characterized in that: The pH of the NaOH solution is 11.5-12.

5.

8. The rapid detection method for trace chloride ions in synthetic silicon dioxide according to claim 1, characterized in that: The ion chromatography test conditions include: an anion suppressor was installed, the suppressor type was AERS-4 mm, and the suppressor current was 50 mA; an AS19 separation column and an AG19 guard column were used, and the column model was 4 mm × 250 mm; the eluent was 50 mmol / L KOH solution; the column box temperature was 30°C; and the injection volume was 25 μL.

9. The rapid detection method for trace chloride ions in synthetic silicon dioxide according to claim 1, characterized in that: The method of calculating the chloride ion content in the synthetic silica according to the chloride ion concentration in the sample solution specifically includes: Substitute the chloride ion concentration in the sample solution into the following formula to calculate the chloride ion content in the synthetic silica: w=c×v / M / 1000, where: w represents the chloride ion content in the synthetic silica, in mg / Kg (ppm), c represents the chloride ion concentration in the sample solution, in mg / L, v represents the volume of the sample solution, in L, and M represents the mass of the synthetic silica, in g.

10. Use of the rapid detection method according to any one of claims 1 to 9 in the rapid detection of trace chloride ions in synthetic silicon dioxide.

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