GB/T 13748.13-2026Methods for chemical analysis of magnesium and magnesium alloys - Part 13: Determination of lead, calcium, potassium and sodium contents - Flame atomic absorption spectrometry (English PDF)

6.2.1 Hydrochloric acid (1 1). Transfer 500 mL of hydrochloric acid (rho=

1.19 g/mL, analytical grade) to 500 mL of water and mix well.

6.2.2 Ammonia (1 1). Transfer 100 mL of ammonia (rho=

0.90 g/mL, analytical grade) to 1000 mL of water and mix well.

6.2.3 Iron solution (1 mg/mL). Weigh

0.484 g of ferric chloride hexahydrate (FeCl3·6H2O), add 5 mL of hydrochloric acid (6.2.1), and dilute with water. Dissolve and dilute to 100 mL, then mix well.

6.2.4 Ammonia-Ammonium Chloride Washing Solution. Weigh 135g of ammonium chloride, dissolve it in 500mL of water, add 48mL of ammonia solution (6.2.2), and transfer to 1000mL of [preparation solution]. Dilute the solution to the mark with water in a volumetric flask and mix well; then transfer 10 mL of the solution to a 500 mL volumetric flask, dilute to the mark with water, and mix well.

6.2.5 Lead Standard Stock Solution (1 mg/mL). Weigh 1.0000 g of lead (wPb >= 99.99%), place it in a 400 mL beaker, and add... 30 mL nitric acid (1.2), cover with a watch glass, heat slowly until completely dissolved, boil for 5 minutes, cool, transfer to a 1000 mL volumetric flask, and use... Dilute with water to the mark and mix well. 1 mL of this solution contains 1 mg of lead. Alternatively, use a certified standard solution.

6.2.6 Lead Standard Solution A (100 µg/mL). Transfer

25.00 mL of lead standard stock solution (6.2.5) to a 250 mL volumetric flask, add... 1 mL of hydrochloric acid (6.2.1) is diluted to the mark with water and mixed well. 1 mL of this solution contains 100 µg of lead.

6.2.7 Lead Standard Solution B (20 µg/mL). Transfer

10.00 mL of lead standard stock solution (6.2.5) to a 500 mL volumetric flask, add... 2 mL of hydrochloric acid (6.2.1), diluted to the mark with water, and mixed well. 1 mL of this solution contains 20 µg of lead.

6.2.8 Phenolphthalein ethanol solution (1 g/L).

6.3 Test Procedure

6.3.1 Sample Weigh 2.50g of sample (Chapter 5), accurate to 0.0001g, and record it as m0.

6.3.2 Parallel Tests Perform the experiment twice in parallel and take the average value.

6.3.3 Blank Test A blank test was performed along with the sample.

6.3.4 Measurement

6.3.4.1 Place the sample in a 250mL beaker, cover with a watch glass, add approximately 5mL of water, and then add 35mL of hydrochloric acid (6.2.1) in portions. Allow to steep. After the strong reaction stops, heat until completely dissolved, then cool.

6.3.4.2 Add 4 mL of iron solution (6.2.3), and dilute with water to approximately 50 mL. Add 4 drops of phenolphthalein ethanol solution (6.2.8) while stirring. Add ammonia water (6.2.2) until the solution turns purple-red, then add an excess of 1 mL. Add 10 mL of ammonia-ammonium chloride washing solution (6.2.4) and let stand for 2 hours.

6.3.4.3 Filter using medium-speed quantitative filter paper, and wash the precipitate four times with ammonia-ammonium chloride washing solution (6.2.4). Place the precipitate in a 25 mL beaker, add... Dissolve the precipitate in hydrochloric acid (6.2.1) (hydrochloric acid temperature. 60°C~80°C), then transfer the solution to a 25mL volumetric flask and dilute to the mark with water. Mix well.

6.3.4.4 At a wavelength of 283.3 nm using a flame atomic absorption spectrometer, with an air-acetylene lean flame and zeroed with water, compare with the corresponding series... The absorbance of lead was measured simultaneously with the standard solution. After subtracting the absorbance of the blank test solution accompanying the sample, the mass of lead was determined from the working curve. Concentration (rhoPb).

6.3.5 Plotting the Working Curve

6.3.5.1 Based on the mass fraction of lead in the sample, the standard solutions for the working curve series are prepared as follows:

---When the lead mass fraction is 0.0010%~0.0040%. Transfer 0mL, 1.00mL, 2.00mL, 3.00mL, 4.00mL, and 5.00mL. Lead standard solution B (6.2.7) was placed in six 25 mL volumetric flasks, and 5 mL of hydrochloric acid (6.2.1) was added to each flask. The solutions were then diluted with water to the specified concentrations. Scale, mix well.

---When the lead mass fraction is >0.0040%~0.010%. Transfer 0 mL,

3.00 mL. Lead standard solution A (6.2.6) was placed in six 25 mL volumetric flasks, and 5 mL of hydrochloric acid (6.2.1) was added to each flask. The solutions were then diluted with water to the specified concentrations. Scale, mix well.

6.3.5.2 The series of standard solutions were analyzed using an air-acetylene lean flame at a wavelength of 283.3 nm on a flame atomic absorption spectrometer, with water added. Zero, the absorbance of lead is measured. The x-axis represents the mass concentration of lead, and the y-axis represents the absorbance minus the absorbance of the "zero concentration" solution. Plot the working curve.

6.5 Precision

6.5.1 Repeatability The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given in Table 2, represent the two test results. The absolute difference does not exceed the repeatability limit (r), and the number of cases exceeding the repeatability limit (r) does not exceed 5%. The repeatability limit (r) is calculated using linear data from Table 2. It can be obtained by interpolation or extension.

6.5.2 Reproducibility The measured values of two independent test results obtained under reproducibility conditions, within the range of the average values given in Table 3, represent the two test results. The absolute difference should not exceed the reproducibility limit (R), and the number of cases exceeding the reproducibility limit (R) should not exceed 5%. The reproducibility limit (R) is determined according to the data in Table 3. Obtained by linear interpolation or extrapolation.

7.2.8 Magnesium Solution A (40 mg/mL). Weigh

20.00 g of metallic magnesium (wMg >= 99.99%, wCa <= 0.0005%) and place it in a 1000 mL container of boiling water. In a cup, cover with a watch glass and add 400 mL of hydrochloric acid (7.2.5) in portions. After the vigorous reaction stops, slowly heat until completely dissolved. Evaporate at room temperature until the salts just precipitate out. Let it cool slightly, add an appropriate amount of water to dissolve the salts, cool again, transfer to a 500mL volumetric flask, and dilute with water to the mark. Mix well.

7.2.9 Magnesium Solution B (1 mg/mL). Weigh

0.50 g of metallic magnesium (wMg>=99.99%, wCa<=0.0005%) into a 100 mL beaker. Cover with a watch glass and add 40 mL of hydrochloric acid (7.2.5) in portions. After the vigorous reaction stops, heat slowly until completely dissolved and evaporate at low temperature. Once the salts have just precipitated, let it cool slightly, add an appropriate amount of water to dissolve the salts, cool again, transfer to a 500mL volumetric flask, dilute with water to the mark, and mix well.

7.2.10 Calcium Standard Stock Solution (500 µg/mL). Weigh 1.2486 g of calcium carbonate primary standard reagent, pre-dried at 105 °C, and place it in... In a 250mL beaker, cover with a watch glass, add 50mL of water and 10mL of hydrochloric acid (7.2.5), heat for 1 minute, and after the reaction is complete, cool and transfer to a container. Pour into a 1000mL volumetric flask, dilute to the mark with water, and mix well. 1mL of this solution contains 500µg of calcium. Alternatively, a certified standard solution can be used.

7.2.11 Calcium Standard Solution (20 µg/mL). Transfer

20.00 mL of calcium standard stock solution (7.2.10) to a 500 mL volumetric flask and dilute with water. Dilute to the mark and mix well. 1 mL of this solution contains 20 µg of calcium. Prepare fresh before use.

7.3 Test Procedure

7.3.1 Sample Weigh the corresponding sample according to Table 4 (Chapter 5), accurate to 0.0001g, and record it as m1.

7.3.2 Parallel Tests Perform the experiment twice in parallel and take the average value.

7.3.3 Blank Test A blank test was performed along with the sample.

7.3.4 Measurement

7.3.4.1 Place the sample in a 250mL beaker, cover with a watch glass, add 10mL~20mL of water, and add salt in portions, totaling 20mL. After the violent reaction stops, heat slowly, adding 2-3 drops of hydrogen peroxide (7.2.2) if necessary, until the sample is completely dissolved. Solution. Boil, slowly evaporate until the salts begin to precipitate, cool slightly, add 20mL~30mL of water, heat until the salts dissolve, and then cool.

7.3.4.2 If there are insoluble substances, filter [the filter funnel and filter paper should be washed with hydrochloric acid (7.2.5) and water to remove any calcium that may have been introduced]. Wash. Place the residue and filter paper in a platinum crucible, ashed at 550°C, and cool. Add 2 mL of perchloric acid (7.2.4) and 5 mL of hydrofluoric acid (7.2.1), and... Add nitric acid (7.2.3) dropwise until the solution is clear, heat to evaporate until no liquid remains, ignite at 700°C for several minutes, cool, and dissolve in a small amount of hydrochloric acid (7.2.5). Remove the residue, filter if necessary, and combine this solution with the original test solution (7.3.4.1).

7.3.4.3 Based on the mass fraction of calcium in the sample, proceed as follows:

---When the calcium mass fraction is 0.0020%~0.010%, transfer the test solution (

7.3.4.1 or 7.3.4.2) into a 100mL volumetric flask, add 10mL... Lanthanum chloride solution (7.2.6), diluted to the mark with water, mixed well, and the volume recorded as V. When the mass fraction of aluminum in the sample is not less than... At 6.0%, add 10 mL of 8-hydroxyquinoline solution (7.2.7) to the test solution (this solution is added along with the standard solution for the working curve series). join in).

---When the calcium mass fraction is >0.010%~3.00%, transfer the test solution (

7.3.4.1 or 7.3.4.2) into the corresponding volumetric flask according to Table 4. Dilute with water to the mark, mix well, and record the volume as V; then transfer the corresponding volume (V1) to a 100mL volumetric flask according to Table 4. Add 5 mL of lanthanum chloride solution (7.2.6), dilute with water to the mark, mix well, and record the volume as V2.

7.3.4.4 At a wavelength of 422.7 nm using a flame atomic absorption spectrometer, an air-acetylene-rich flame was used, and the instrument was zeroed with water. The corresponding system was then... Measure the absorbance of calcium simultaneously with the standard solution, subtract the absorbance of the blank test solution accompanying the sample, and find the corresponding calcium value from the working curve. Mass concentration (rhoCa).

7.3.5 Plotting the Working Curve

7.3.5.1 Based on the mass fraction of calcium in the sample, the standard solutions for the working curve are prepared as follows:

---When the calcium mass fraction is 0.0020%~0.010%. transfer 0 mL,

5.00 mL of calcium standard solution (7.2.11) was placed in a set of 100 mL volumetric flasks, and 25 mL of magnesium solution A (7.2.8) was added to each flask. 10 mL of lanthanum chloride solution (7.2.6) was diluted to the mark with water and mixed well. When the mass fraction of aluminum in the sample is not less than 6.0%, Add 10 mL of 8-hydroxyquinoline solution (7.2.7) along with the test solution.

7.5 Precision

7.5.1 Repeatability The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given in Table 5, represent the two test results. The absolute value does not exceed the repeatability limit (r), and the number of cases exceeding the repeatability limit (r) does not exceed 5%. The repeatability limit (r) is determined by linearity based on the data in Table 5. Obtained by interpolation or extrapolation.

7.5.2 Reproducibility The measured values of two independent test results obtained under reproducibility conditions, within the range of the average values given in Table 6, represent the two test results. The absolute difference does not exceed the reproducibility limit (R), and the number of cases exceeding the reproducibility limit (R) does not exceed 5%. The reproducibility limit (R) is calculated using linear regression based on the data in Table 6. It can be obtained by interpolation or extension.

8.2.3 Magnesium solution (20 mg/mL). Weigh

20.00 g of metallic magnesium (wMg >= 99.99%, wK <= 0.0005%, wNa <= 0.0005%) and place it in a container... In a 1000mL PTFE beaker, cover with a watch glass and add 600mL of hydrochloric acid (8.2.2) in portions, heating slowly until completely dissolved. Dissolve and cool. Transfer the solution to a 1000 mL volumetric flask, dilute to the mark with water, and mix well.

8.3 Test Procedure

8.3.1 Sample Weigh 0.50g of sample (Chapter 5), accurate to 0.0001g, and record it as m2.

8.3.2 Parallel Tests Perform the experiment twice in parallel and take the average value.

8.3.3 Blank Test A blank test was performed along with the sample.

8.3.4 Measurement

8.3.4.1 Place the sample in a 300 mL polytetrafluoroethylene beaker, add 20 mL of hydrochloric acid (8.2.2), and after the vigorous reaction stops, add... Add 2 drops of hydrogen peroxide (8.2.1), heat at low temperature until the sample is completely dissolved, and cool to room temperature. Transfer the solution to a 100 mL volumetric flask and dilute with water. Add water to the mark and mix well.

8.3.4.2 On a flame atomic absorption spectrometer, using an air-acetylene lean flame and zeroing with water, the corresponding series of standard solutions were simultaneously analyzed. Measure the absorbance of potassium at a wavelength of 766.5 nm and the absorbance of sodium at a wavelength of 589.2 nm, and subtract the absorbance of the blank test solution accompanying the sample. The absorbance was used to determine the corresponding potassium and sodium mass concentrations (rhoK/Na) from the working curve.

8.3.5 Plotting the Working Curve

8.3.5.1 Transfer 0 mL,

0.50 mL,

10.00 mL of potassium standard solution respectively. Prepare either solution (8.2.6) or sodium standard solution (8.2.7) in a set of 100 mL volumetric flasks, add 25 mL of magnesium solution (8.2.3), and dilute with water. Mix to the mark.

8.3.5.2 On a flame atomic absorption spectrometer, using an air-acetylene lean flame and zeroed with water, a series of standard solutions were analyzed at a wavelength of 766.5 nm. The absorbance of potassium was measured at 589.2 nm, and the absorbance of sodium was measured at 589.2 nm. The absorbance was plotted on the x-axis as the mass concentrations of potassium and sodium, with the corresponding absorbance minus... Using the absorbance of the "zero concentration" solution as the ordinate, plot the working curves.

8.5 Precision

8.5.1 Repeatability The measured values of two independent test results obtained under repeatability conditions, within the range of the average values given in Table 7, represent the two test results. The absolute value does not exceed the repeatability limit (r), and the number of cases exceeding the repeatability limit (r) does not exceed 5%. The repeatability limit (r) is determined by linearity based on the data in Table 7. Obtained by interpolation or extrapolation.

8.5.2 Reproducibility The measured values of two independent test results obtained under reproducibility conditions, within the range of the average values given in Table 8, represent the two test results. The absolute difference does not exceed the reproducibility limit (R), and the number of cases exceeding the reproducibility limit (R) does not exceed 5%. The reproducibility limit (R) is calculated using linear regression based on the data in Table 8. It can be obtained by interpolation or extension.