Method for rapidly determining main content of sodium fluoride

Abstract

The invention discloses a method for rapidly determining the main content of sodium fluoride. The method comprises the following specific conditions: (1) preparing a fluorine ion standard working solution; (2) preparing solutions of an impurity sodium sulfate standard substance and a sodium chloride standard substance determined by an experimental reagent; (3) operation conditions of an ion chromatograph: a chromatographic column is an anion exchange chromatographic column; the detector is a conductivity detector; the column temperature is 40 DEG C; the sample size is 10 [mu] L; the concentration of the leacheate is 15mM KOH; the flow rate is 1.0 mL / min; the suppression current is 45 mA; the operation time is 30 minutes; and (4) an ion chromatograph test method: an area normalization method. The method is high in automation degree, simple and easy to implement and good in identification performance.

Description

Technical Field

[0001] The invention relates to the field of chemical detection and analysis, and in particular to a method for rapidly determining the main content of sodium fluoride. Background Art

[0002] Sodium fluoride is an inorganic compound with toxicity. It is mainly used in the coating industry as a phosphating accelerator, agricultural pesticide, sealing material, preservative and other fields. The chemical properties of sodium fluoride are relatively stable. In addition to relatively stable sodium fluoride compounds, there are also trace amounts of chloride and sulfate depending on the production process. The current inspection standard GB / T 1264-1997 only conducts quantitative detection and analysis of sodium fluoride content and water-insoluble matter. The sodium fluoride content detection method activates the resin, collects the washing liquid, and then calculates the result by titration with sodium hydroxide and standard titration solution. It is cumbersome and time-consuming, and other impurities are only regulated by turbidimetry or colorimetry, and cannot provide accurate results for quantitative detection. Summary of the invention

[0003] In order to solve the above problems, the present invention aims to provide a method for quickly determining the main content of sodium fluoride. Sodium fluoride mainly includes sodium fluoride, sulfate, chloride, and fluorosilicate. Since the solubility of fluorosilicate in water is relatively low (at 25°C, the solubility of sodium fluorosilicate in water is 0.78%), it generally exists in the form of water-insoluble matter. The main content of sodium fluoride, sulfate, and chloride is identified.

[0004] The technical solution of the present invention is as follows: A method for rapidly determining the main content of sodium fluoride: the method uses ion chromatography for determination, and the specific conditions include the following: (1) Preparation of fluoride ion standard working solution: (2) Experimental reagents to determine the preparation of solutions of impurity sodium sulfate standard and sodium chloride standard; (3) Ion chromatograph operating conditions: (4) Ion chromatography test method: area normalization method.

[0005] Preferably, the fluoride ion standard working solution in step (1) comprises a sodium fluoride stock solution and a sodium fluoride single-label reference solution: the sodium fluoride stock solution is 200 μg / mL NaF; the sodium fluoride single-label reference solution is 3-5 μg / mL NaF solution.

[0006] Sodium fluoride standard should be dried at 145-155℃ for 3-5 hours as required before weighing.

[0007] Preferably, the fluoride ion standard working solution in step (1) comprises a sodium fluoride stock solution and a sodium fluoride single standard reference solution: the sodium fluoride stock solution is 200 μg / mL NaF: the sodium fluoride single standard reference solution is 4 μg / mL NaF solution; Sodium fluoride standard should be dried at 150℃ for 4 hours as required before weighing.

[0008] Preferably, the solutions of the sodium sulfate standard and the sodium chloride standard in step (2) specifically include: the sodium sulfate stock solution is 740-760 µg / mL Na2SO4: the sodium sulfate single-label reference solution is 12-17 μg / mL Na2SO4 solution; the sodium chloride stock solution is 870-880 μg / mL NaCl: the sodium chloride single-label reference solution is 0.6-0.9 μg / mL NaCl solution.

[0009] Further preferably, the solutions of the sodium sulfate standard and the sodium chloride standard in step (2) specifically include: the sodium sulfate stock solution is 750 µg / mL Na2SO4: the sodium sulfate single-label reference solution is 15 µg / mL Na2SO4 solution; the sodium chloride stock solution is 876 µg / mL NaCl: the sodium chloride single-label reference solution is 0.8 µg / mL NaCl solution.

[0010] Preferably, the (3) ion chromatography conditions: the chromatographic column is an anion exchange chromatographic column; The detector is a conductivity detector; Column temperature: 40°C; Injection volume: 10 μL; The eluent concentrations were: 15 mM KOH; Flow rate: 1.0 mL / min; Inhibition current: 45mA; Running time: 30min.

[0011] The beneficial effects of the present invention are as follows: This method has a high degree of automation, is simple and easy to implement, and has good identification. It is directly diluted with pure water and does not need to contact with acidic solutions, which saves costs and is safer. It can detect data in a timely manner, ensuring product quality for continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the calibration diagram of sodium fluoride peak time; Figure 2 Produce a calibration diagram for carbonate in pure water; Figure 3 This is the calibration diagram of the elution time of sulfate, an impurity peak in the sample; Figure 4 This is the peak time correction diagram of chloride impurity peak in the sample; Figure 5 Sodium fluoride reproducibility spectrum; Figure 6 Sodium fluoride standard curve; Figure 7 Sodium fluoride standard curve; Figure 8 Sample chromatogram. DETAILED DESCRIPTION The following will be combined with the specific embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0013] Ion chromatograph operating conditions: The chromatographic column is an anion exchange chromatographic column; The detector is a conductivity detector; Column temperature: 40°C; Injection volume: 10 μL; The eluent concentration was: 15 mM KOH; Flow rate: 1.0 mL / min; Inhibition current: 45mA; Running time: 30min.

[0014] Ion chromatography test method: area normalization method.

[0015] A method for rapidly determining the main content of sodium fluoride comprises the following specific steps: Step 1. Preparation of fluoride ion standard working solution: (a1) Sodium fluoride standard should be dried as required before weighing; (a2) Sodium fluoride stock solution 200 µg / mL NaF: Accurately weigh 0.180-0.220 g (accurate to 0.001 g) of sodium fluoride standard into a 1000 mL plastic volumetric flask, add ultrapure water to make up to volume, and calculate the exact concentration; (a3) Sodium fluoride single standard reference solution (4 μg / mL NaF solution): Use a pipette to accurately measure 1 ml of sodium fluoride stock solution (200 μg / mL) into a 50 mL plastic volumetric flask, and dilute to the mark with ultrapure water; Step 2. Preparation of samples to be tested: Accurately weigh 0.2g (accurate to 0.001g) of sodium fluoride raw material powder, transfer it to a 1000mL plastic volumetric flask, add a little ultrapure water, shake gently to dissolve, and dilute to the mark with ultrapure water. Use a pipette to accurately measure 1mL to a 50mL plastic volumetric flask, add ultrapure water to dilute to the mark and shake well. The solution before entering the instrument is filtered with a 0.22μm aqueous phase filter membrane and then tested; Step 3. Correction: (c1) Preparation of system identification solution: Preparation of sodium sulfate stock solution (750ug / mL Na2SO4): Accurately weigh 0.675-0.825g (accurate to 0.01g) of sodium sulfate and transfer it to a 1000mL volumetric flask, add ultrapure water to the volume, and shake well. Use a pipette to accurately measure 2mL to a 100mL plastic volumetric flask, add ultrapure water to the volume, and shake well; Preparation of sodium chloride stock solution (876ug / mL NaCl): Accurately weigh 0.87660g (accurate to 0.01g) of sodium chloride standard reagent burned to constant weight in a high-temperature furnace at 550℃±50℃ and transfer it to a 1000mL volumetric flask, add ultrapure water to the volume, and shake well. Use a pipette to accurately measure 1mL to a 1000mL plastic volumetric flask, add ultrapure water to the volume, and shake well; (c2) Correction method: After the instrument is stable, inject 5 injections of the above-mentioned concentration of sodium fluoride single-standard reference solution (1a3) and system identification solution (3c1), and integrate the collected spectra; The peak time of sodium fluoride in the sample is shown in Table 1 below, (corrected Figure 1 ).

[0016] Table 1

[0017] The peak time of carbonate in pure water is shown in Table 2 below (corrected Figure 2 ) Table 2

[0018] The elution time of the impurity peak sulfate in the sample is shown in Table 3 below (corrected Figure 3 ) Table 3

[0019] The peak time of chloride impurity in the sample is shown in Table 4 below, (corrected Figure 4 ) Table 4

[0020] Step 4. Method selection: Further, the method selection in step 4 is tested, using a sodium fluoride sample processed according to step 2, and detected using the area normalization method and the external standard method, and compared with the reported result of 99.39%; Example 1 (area normalization method) Take the sodium fluoride sample solution after filtration in step 2 and inject it 5 times continuously. According to the peak time determined in step 3 (c2), only the chromatographic peaks of sodium fluoride, sodium chloride and sulfate are retained, and the sodium fluoride content is calculated by the area normalization method. The test results are shown in Table 5 below, (spectrum Figure 5 ).

[0021] Table 5

[0022] Comparative Example 1 (External Standard Method) External standard method 1: single point control (d1) Filter the sodium fluoride standard according to the method in step 2 and inject one injection; (d2) Using the standard solution (a3), adopt the external standard method, with the concentration value as the horizontal axis and the peak area response value as the vertical axis, draw a sodium fluoride standard curve. Figure 6 ; (d3) Take the sodium fluoride sample solution after filtration in step 2 and inject it 5 times continuously. Use the external standard method and substitute the calculated results into the table below. The reproducibility spectrum is shown in Table 6. Figure 5 .

[0023] Table 6

[0024] External standard method 2: multi-point control (e1) Take the sodium fluoride stock solution 200 µg / mL NaF prepared in step 1 (a2) and pipette 1 mL, 2.5 mL, and 5 mL into three 100 mL plastic volumetric flasks to prepare 2 µg / mL, 5 µg / mL, and 10 µg / mL standard series; (e2) Using the standard series solution of (e1), adopt the external standard method, with the concentration value as the horizontal axis and the peak area response value as the vertical axis, draw a sodium fluoride standard curve. Figure 7 ; (e3) The same implementation method as (d3) in Comparative Example 1 was used, and the results obtained by the external standard method were shown in Table 7 below.

[0025] Table 7

[0026] From the data in Tables 5, 6 and 7, it can be seen that the area normalization method is simpler to operate than the external standard method, has a smaller standard deviation, and has a smaller absolute value of error compared with the national standard test results.

[0027] Example 2 Sample concentration selection (f1) According to the method in step 2, prepare sodium fluoride samples into solutions of different concentrations (2 μg / mL, 4 μg / mL, 6 μg / mL, 8 μg / mL, 10 μg / mL) and inject them continuously for 5 times.

[0028] (f2) Based on the peak time determined in step 3 (c2), only the chromatographic peak integrals of sodium fluoride, sodium chloride and sulfate are retained, and the sodium fluoride content is calculated using the area normalization method. The detected data are shown in Table 8 below.

[0029] Table 8

[0030] (f3) It can be seen from the above table that when the sample concentration is 4μg / mL, the standard deviation is small and the absolute value of the error with the national standard test result is small.

[0031] Step 5. Experiment: (g1) Determination of repeatability of sodium fluoride single standard reference solution: The sodium fluoride single-standard reference solution was injected 5 times, and the RSD of the repeatability of the 5 injections of the sodium fluoride single-standard reference solution was calculated to be 0.16%; (g2) Determination of sodium fluoride sample solution: Prepare the solution for injection of 10 sodium fluoride samples according to (f3). The sample results are calculated by retaining only the integral of the chromatographic peaks of sodium fluoride, sodium chloride, and sulfate according to the peak elution time determined in step 3 (c2), and calculating the sodium fluoride content using the area normalization method.

[0032] (g3) Sodium fluoride sample detection reproducibility determination: Randomly select 6 of the sodium fluoride sample solutions prepared according to (f3) and inject them three times continuously. According to the peak elution time determined in step 3 (c2), only retain the chromatographic peak integration of sodium fluoride, sodium chloride, and sulfate, and calculate the sodium fluoride content using the area normalization method.

[0033] (g4) Compare the test results of sodium fluoride content by ion chromatography and national standard method.

[0034] Step 6. Experimental results (e2) The specific test results of sodium fluoride samples are shown in Table 9. The sample chromatogram is as follows: Figure 8 .

[0035] Table 9 The determination results of sodium fluoride content

[0036] (d3) Test result reproducibility verification see Table 10: Table 10 Verification of reproducibility of ion chromatography test results

[0037] (d4) Test results are compared in Table 11: Table 11 Comparison of sodium fluoride content by ion chromatography and national standard method

[0038] It can be seen from Table 10 and Table 11 that the results of the main content of sodium fluoride detected by the ion chromatography area normalization method are compared, and the error is ≤0.2%, which meets the error requirements of the national standard titration determination. The repeatability test in Table 10 shows that the standard deviation of the test of 6 samples every 3 times is less than 0.15%. The time shown in Tables 1 to 4 shows that the peak time of sodium fluoride and impurities can be within 20 minutes, and the test results are accurate, time-saving and efficient.

[0039] The technical solution of the present invention is explained through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above specific embodiments to be implemented. Any improvements made by technicians in the relevant field based on the present invention, or equivalent replacement of the materials selected by the present invention, etc., fall within the scope of protection of the patent.

Claims

1. A method for rapidly determining the main content of sodium fluoride: characterized in that: The method uses ion chromatography for determination, and the specific conditions include the following: (1) Preparation of fluoride ion standard working solution: (2) Experimental reagents to determine the preparation of solutions of impurity sodium sulfate standard and sodium chloride standard; (3) Ion chromatograph operating conditions: (4) Ion chromatography test method: area normalization method.

2. The method for rapidly measuring the main content of sodium fluoride according to claim 1, wherein: The fluoride ion standard working solution in step (1) includes a sodium fluoride stock solution and a sodium fluoride single-label reference solution: the sodium fluoride stock solution is 200 μg / mL NaF; the sodium fluoride single-label reference solution is 3-5 μg / mL NaF solution. Sodium fluoride standard should be dried at 145-155℃ for 3-5 hours as required before weighing.

3. The method for rapidly measuring the main content of sodium fluoride according to claim 2, wherein: In step (1), the fluoride ion standard working solution includes a sodium fluoride stock solution and a sodium fluoride single standard reference solution: the sodium fluoride stock solution is 200 μg / mL NaF: the sodium fluoride single standard reference solution is 4 μg / mL NaF solution; Sodium fluoride standard should be dried at 150℃ for 4 hours as required before weighing.

4. The method for rapidly determining the main content of sodium fluoride according to claim 1, wherein: The solutions of the sodium sulfate standard and the sodium chloride standard in step (2) specifically include: a sodium sulfate stock solution of 740-760 µg / mL Na2SO4: a sodium sulfate single-label reference solution of 12-17 µg / mL Na2SO4 solution; a sodium chloride stock solution of 870-880 µg / mL NaCl: a sodium chloride single-label reference solution of 0.6-0.9 µg / mL NaCl solution.

5. The method for rapidly determining the main content of sodium fluoride according to claim 4, characterized in that: The solutions of the sodium sulfate standard and the sodium chloride standard in step (2) specifically include: a sodium sulfate stock solution of 750 µg / mL Na2SO4: a sodium sulfate single-label reference solution of 15 µg / mL Na2SO4 solution; a sodium chloride stock solution of 876 µg / mL NaCl: a sodium chloride single-label reference solution of 0.8 µg / mL NaCl solution.

6. The method for rapidly determining the main content of sodium fluoride according to claim 1, characterized in that: The (3) ion chromatography conditions: the chromatographic column is an anion exchange chromatographic column; The detector is a conductivity detector; Column temperature: 40°C; Injection volume: 10 μL; The eluent concentrations were: 15 mM KOH; Flow rate: 1.0 mL / min; Inhibition current: 45mA; Running time: 30min.

Images