GB/T 13748.1-2026Methods for chemical analysis of magnesium and magnesium alloys - Part 1: Determination of aluminium content (English PDF)

6.2 Reagents or Materials Warning

---Benzene and chloroform are highly toxic substances. When handling them, it is your responsibility to wear protective equipment as required and avoid contact with skin and clothing. The items are handled and the operation is completed in a fume hood. Unless otherwise specified, only reagents confirmed to be of analytical grade and grade II water conforming to GB/T 6682 shall be used in the analysis.

6.2.1 Chloroform.

6.2.3 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.

6.2.4 Hydrochloric acid (1 10). Transfer 100 mL of hydrochloric acid (rho=

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

6.2.5 Hydrochloric acid [cHCl=0.2mol/L]. Transfer 17mL of hydrochloric acid (rho=1.19g/mL, analytical grade) to 1000mL of water and mix well.

6.2.6 Thioglycolic acid (1 4). Take 20 mL of thioglycolic acid (wC2H4O2S>=90.0%) and dissolve it in 80 mL of water, then mix well.

6.2.7 Ammonia (1 10). Transfer 100 mL of ammonia (rho =

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

6.2.8 Ammonium carbonate solution (200g/L). Weigh.200g of ammonium carbonate and dissolve it in 1000mL of water. Mix well and store in a plastic bottle.

6.2.9 Tantalum reagent-ethanol solution (20 g/L). Weigh 2 g of N-benzoyl-N-phenylhydroxylamine (tantalum reagent) and dissolve it in 100 mL of anhydrous ethanol. Mix well. Prepare fresh before use. 6.2.10 8-Hydroxyquinoline solution (50 g/L). Weigh 5 g of 8-hydroxyquinoline and dissolve it in 100 mL of acetic acid solution [cCH3COOH = 2 mol/L] Mix well, filter with medium-speed filter paper, and store in a brown reagent bottle.

6.2.11 Acetic acid-sodium acetate buffer solution. Mix equal volumes of anhydrous sodium acetate solution [cCH3COONa=2mol/L] and acetic acid solution. [cCH3COOH=2mol/L] mixture.

6.2.12 Aluminum Standard Stock Solution (1 mg/mL). Weigh 1.0000 g of aluminum (wAl >= 99.99%) into a 300 mL beaker, add... Add 60 mL of hydrochloric acid (6.2.3) and heat at low temperature until completely dissolved. Remove from heat and cool to room temperature. Transfer to a 1000 mL volumetric flask and add 40 mL of salt. Acid (6.2.3), dilute to the mark with water and mix well. 1 mL of this solution contains 1 mg of aluminum. Alternatively, use a certified standard solution.

6.2.13 Aluminum Standard Solution (10 µg/mL). Transfer

25.00 mL of aluminum standard stock solution (6.2.12) to a 250 mL volumetric flask, add... Add 5 mL of hydrochloric acid (6.2.3), dilute to the mark with water, and mix well. Then transfer

25.00 mL of this solution to a 250 mL volumetric flask, and add 5 mL of... Hydrochloric acid (6.2.3), diluted with water to the mark, mixed well. 1 mL of this solution contains 10 µg of aluminum.

6.2.14 Saturated solution of 2,4-dinitrophenol. Weigh

0.2 g of 2,4-dinitrophenol (C6H4O5N2) into a.200 mL beaker, add 100 mL of... Add water and stir continuously until 2,4-dinitrophenol no longer dissolves. Cool, let stand, and take the upper saturated solution.

6.3 Test Procedure

6.3.1 Sample Weigh the sample according to Table 1 (Chapter 5), accurate to 0.0001g, and record it as m0.

6.3.2 Parallel Tests Perform two parallel experiments 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 150mL beaker, add 10mL of hydrochloric acid (6.2.3), cover with a watch glass, and heat at low temperature until the sample is completely dissolved. Remove the solution and allow it to cool to room temperature. Transfer the solution to a 100 mL (V0) volumetric flask, dilute to the mark with water, and mix well.

6.3.4.2 Transfer

10.00 mL (V1) of the test solution into a 100 mL separatory funnel.

6.3.4.3 Add 1 mL of thioglycolic acid (6.2.6) and 1 drop of saturated 2,4-dinitrophenol solution (6.2.14), and adjust with ammonium carbonate solution (6.2.8). Continue adding water until the solution turns yellow, then add an excess of 5 mL, dilute with water to approximately 30 mL, add 1 mL of tantalum reagent-ethanol solution (6.2.9), and mix. Mix well and let stand for 10 minutes. Add 15 mL of benzene (6.2.2), shake for 3 minutes, let stand to separate the layers, and discard the aqueous phase. Add 15 mL of water to wash the organic phase. Mix the aqueous phase, shake for 15 seconds, allow to stand to separate into layers, and discard the aqueous phase. Add 15 mL of hydrochloric acid (6.2.5), shake for 3 minutes, and allow to stand to separate into layers.

6.3.4.4 Transfer the aqueous phase to a 50 mL separatory funnel, add 1 drop of saturated 2,4-dinitrophenol solution (6.2.14), and adjust to a final concentration with ammonia (6.2.7). The solution is yellow. Add hydrochloric acid (6.2.4) dropwise until the yellow color disappears, then add 5 mL of acetate-sodium acetate buffer solution (6.2.11) and

0.5 mL of sodium acetate buffer solution. Mix the 8-hydroxyquinoline solution (6.2.10) thoroughly and let stand for 5 minutes. Add

10.00 mL of chloroform (6.2.1), shake for 3 minutes, allow to stand until layering occurs, and discard the solution. Remove the aqueous phase and transfer the organic phase into a 10 mL dry colorimetric tube.

6.3.4.5 Transfer a portion of the test solution into a 1cm dry cuvette, using the blank test solution accompanying the sample as a reference, and analyze it on a spectrophotometer. The absorbance was measured at 390 nm, and the corresponding mass of aluminum (m1) was obtained from the working curve.

6.3.5 Plotting the Working Curve

6.3.5.1 Transfer 0 mL,

0.50 mL,

3.00 mL of aluminum standard solution (6.2.13) respectively. Place the mixture in a set of 100mL separatory funnels, add 15mL of water, and proceed according to 6.3.4.3~6.3.4.4.

6.3.5.2 Transfer a portion of the test solution into a 1cm dry cuvette, using the "zero" concentration solution in the working curve series of standard solutions as a reference, and... The absorbance was measured at a wavelength of 390 nm using a spectrophotometer. A working curve was plotted with the mass of aluminum on the x-axis and absorbance on the y-axis. The linear correlation coefficient of the curve should be no less than 0.999.

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 determined by linear regression based on the data in 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 calculated using linear regression based on the data in Table 3. It can be obtained by interpolation or extension.

7.2.1 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.

7.2.2 Hydrochloric acid (1 19). Dissolve 100 mL of hydrochloric acid (rho=

1.19 g/mL, analytical grade) in 1900 mL of water and mix well.

7.2.3 Ammonia solution (1 1). Dissolve 500 mL of ammonia solution (rho=

0.90 g/mL, analytical grade) in 500 mL of water and mix well. 7.2.4 2,4-Dinitrophenol ethanol solution (1 g/L). Weigh

0.1 g of 2,4-dinitrophenol, dissolve it in 50 mL of anhydrous ethanol, and use anhydrous ethanol... Dilute to 100 mL and mix well.

7.2.5 Ascorbic acid solution (10g/L). Weigh 1.0g of ascorbic acid, dissolve it in 50mL of water, dilute with water to 100mL, mix well, and use as needed. Prepared on the spot.

7.2.6 o-Phenanthroline solution (10 g/L). Weigh

5.0 g of o-Phenanthroline, dissolve it in 100 mL of anhydrous ethanol, and dilute with water to a final concentration of 10 g/L. Mix 500mL thoroughly.

7.2.7 Chromium azurite S-tetradecylpyridine chloride solution. Weigh

0.15 g of chromium azurite S and 1 g of tetradecylpyridine chloride, and dissolve them separately in a small amount of... Add to water, then mix, dilute with water to 500 mL, and mix well.

7.2.8 Acetic acid-sodium acetate buffer solution (pH 5.8). Weigh

90.2 g of anhydrous sodium acetate and dissolve it in water, then add

6.0 mL of glacial acetic acid (rho = Transfer

1.05 g/mL to a 1000 mL volumetric flask, dilute to the mark with water, and mix well.

7.2.9 Aluminum Standard Stock Solution (1 mg/mL). Weigh 1.0000 g of aluminum (wAl >= 99.99%) into a 300 mL beaker, add... Add 60 mL of hydrochloric acid (7.2.1) and heat at low temperature until completely dissolved. Remove from heat and cool to room temperature. Transfer to a 1000 mL volumetric flask and add 40 mL of salt. Acid (7.2.1), dilute to the mark with water and mix well. 1 mL of this solution contains 1 mg of aluminum. Alternatively, use a certified standard solution.

7.2.10 Aluminum Standard Solution (1 µg/mL). Transfer

25.00 mL of aluminum standard stock solution (7.2.9) to a 250 mL volumetric flask, add... 5 mL of hydrochloric acid (7.2.1) was diluted to the mark with water and mixed well. Then,

5.00 mL of this solution was transferred to a 500 mL volumetric flask, and 10 mL of water was added. Hydrochloric acid (7.2.1), diluted to the mark with water, mixed well. This solution contains 1 µg of aluminum per mL. Prepare fresh before use.

7.3 Test Procedure

7.3.1 Sample Weigh 0.10g of the sample (Chapter 5), accurate to 0.0001g, and record it as m2.

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.200mL beaker, add 5mL of water and 2mL of hydrochloric acid (7.2.1), and after a vigorous reaction, heat to evaporate to a solution. Prepare approximately 1 mL of solution and cool to room temperature. Transfer the solution to a 100 mL (V2) volumetric flask, dilute to the mark with water, and mix well. Take aliquots as shown in Table 4. The required volume (V3) of the test solution is placed in a 100 mL volumetric flask.

Note. In this solution, when the copper concentration is greater than 10 µg/mL, the cadmium concentration is greater than 10 µg/mL, and the strontium concentration is greater than 20 µg/mL, the aluminum content will be affected. The measurement may be subject to interference.

7.3.4.2 Dilute with water to approximately 50 mL, add 4 drops of 2,4-dinitrophenol ethanol solution (7.2.4), and add ammonia solution (7.2.3) until... The solution is yellow. Then add hydrochloric acid (7.2.2) dropwise until the yellow color disappears.

7.3.4.3 Add 2 mL of ascorbic acid solution (7.2.5) and 2 mL of o-phenanthroline solution (7.2.6) successively, and mix well after each addition. Add the solution along the wall of the flask. Add 10 mL of chromazin S-tetradecylpyridine chloride solution (7.2.7), mix gently, and then add 10 mL of acetate-sodium acetate buffer solution. (7.2.8) Dilute with water to the mark, mix well, and let stand for 20 minutes.

7.3.4.4 Transfer a portion of the test solution into a 1 cm cuvette, using the blank test solution accompanying the sample as a reference, and measure the solution at a wavelength of [wavelength missing] on a spectrophotometer. The absorbance was measured at 625 nm. The corresponding mass (m3) of aluminum was obtained from the working curve.

7.3.5 Plotting the Working Curve

7.3.5.1 Transfer 0 mL,

10.00 mL of aluminum standard solution (7.2.10) aliquots. Do not place in seven 100mL volumetric flasks, proceed according to

7.3.4.2 and 7.3.4.3.

7.3.5.2 Transfer a portion of the test solution into a 1cm cuvette, using the "zero" concentration solution in the working curve series of standard solutions as a reference, and spectrophotometer. The absorbance was measured at a wavelength of 625 nm using a photometer. A working curve was plotted with the mass of aluminum on the x-axis and absorbance on the y-axis. The linear correlation coefficient of the line should not be less than 0.999.

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 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 determined by linear regression based on the data in Table 5. It can be obtained by interpolation or extension.

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 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 calculated using linear regression based on the data in Table 6. It can be obtained by interpolation or extension.

8.2.13 Bromophenol blue ethanol solution (

0.2 g of bromophenol...