GB/T 6609.11-2026Chemical analysis and physical property determination methods for alumina - Part 11: Determination of manganese oxide and magnesium oxide - Flame atomic absorption spectrometry (English PDF)

6.2 Reagents Warning

---The chloroform used in this document can cause harm to the human body if inhaled or absorbed through the skin. It will react with oxygen in the air when exposed to light. The process involves the release of toxic gases, so protective equipment must be worn during the experiment, and the experiment must be conducted under well-ventilated conditions. Unless otherwise specified, only reagents confirmed to be of superior purity and Class II water conforming to GB/T 6682 shall be used in the analysis.

6.2.1 Hydrochloric acid (rho=1.19g/mL).

6.2.2 Chloroform, store protected from light.

6.2.3 Hydrochloric acid (1 120).

6.2.4 Sodium hydroxide solution (500g/L). Weigh 500g of sodium hydroxide and place it in a 1000mL plastic beaker. Add 400mL of water and dissolve. Completely transfer the solution to a 1L plastic volumetric flask, dilute with water to the mark, and mix well.

6.2.5 Potassium sodium tartrate solution (200 g/L). Weigh 100 g of potassium sodium tartrate into a 500 mL beaker, add 300 mL of water, and dissolve. Completely transfer the solution to a 500 mL volumetric flask, dilute with water to the mark, and mix well. 6.2.6 2-Methyl-8-hydroxyquinoline solution (20 g/L). Weigh

2.0 g of 2-methyl-8-hydroxyquinoline and dissolve it in 5 mL of glacial acetic acid in a high-boron solution. Dilute with water in a silica glass beaker, transfer to a 100mL volumetric flask, dilute to the mark with water, and mix well.

6.2.7 Manganese monoxide standard stock solution. Weigh 0.6196 g of metallic manganese (wMn>=99.9%) into a 150 mL beaker, add 12 mL of... Hydrochloric acid (1.1), cover with a watch glass, place on a hot plate and heat at low temperature until all the metallic manganese is dissolved, cool to room temperature, and transfer the solution to 1000 mL Dilute to the mark with water in a volumetric flask and mix well. 1 mL of this solution contains

0.8 mg of manganese monoxide.

6.2.8 Manganese monoxide standard solution. Transfer

10.00 mL of manganese monoxide standard stock solution (6.2.7) to a 1000 mL volumetric flask, and use... Dilute with water to the mark and mix well. 1 mL of this solution contains

0.008 mg of manganese monoxide.

6.3 Analysis Steps

6.3.1 Sample Weigh 1.50g of the sample (Chapter 5), accurate to 0.0001g.

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 Preparation of analytical solutions

6.3.4.1 Place the sample (6.3.1) into the reaction vessel of the polytetrafluoroethylene sealed sample dissolving apparatus (4.2), add 20 mL of hydrochloric acid (6.2.1), and seal the apparatus. Place the cup lid into the PTFE sealed sample dissolving container (4.2), close the sample dissolving container lid, place it in the steel sleeve, tighten the steel sleeve lid, and then place it in the oven (4.5). In the middle, the temperature is raised to 240°C±3°C, kept at this temperature for 6 hours, and then naturally cooled to room temperature.

6.3.4.2 Remove the polytetrafluoroethylene reaction vessel, transfer the solution to a 250mL beaker, wash the reaction vessel with water, and add the washing water to the beaker. Cover the beaker. Place a good watch glass on a hot plate and evaporate at a low temperature until the salts just begin to precipitate.

6.3.4.3 Remove the beaker, add 50 mL of water to dissolve all the salts, then add 25 mL of potassium sodium tartrate solution (6.2.5), stirring constantly. Slowly add 10 mL of sodium hydroxide solution (6.2.4) until the precipitated aluminum hydroxide is completely dissolved. Avoid using excessive sodium hydroxide. Add 5 mL of 2-methyl-8-hydroxyquinoline solution (6.2.6), stir until completely dissolved, allow to cool naturally to room temperature, and then dissolve using sodium hydroxide solution. (6.2.4) and hydrochloric acid (6.2.1), and the pH of the solution was adjusted to

11.8 by pH meter (4.4).

6.3.4.4 Transfer the solution to a 250 mL separatory funnel, extract with 20 mL of chloroform (6.2.2), shake for 1 min, and separate the organic phase. Continue extraction with 10 mL of chloroform (6.2.2) until the organic phase no longer turns green (usually 4 to 5 extractions are required). Collect the organic phase. Collect the contents in a beaker containing 1 mL of hydrochloric acid (6.2.1), cover with a watch glass, and evaporate to dryness on a hot plate at low temperature.

6.3.4.5 Remove the beaker, dissolve the residue with a small amount of hydrochloric acid (6.2.3), and rinse with hydrochloric acid (6.2.3) into a 25 mL volumetric flask. Allow to cool naturally until... At room temperature, dilute to the mark with hydrochloric acid (6.2.3) and mix well.

6.3.5 Measurement Under optimal operating conditions, using an air-acetylene flame on a flame atomic absorption spectrometer (4.1), at a wavelength of 279.5 nm, Zero the instrument with water, and measure the absorbance of a series of standard solutions and test solutions (6.3.4.5) and accompanying blank samples (6.3.3). Find the corresponding values from the working curve. The corresponding manganese monoxide mass concentration.

6.3.6 Drawing the working curve

6.3.6.1 Transfer 0 mL,

16.00 mL of manganese monoxide standard solution. (6.2.8) Place them in a set of 25mL volumetric flasks, dilute to the mark with hydrochloric acid (6.2.3), and mix well.

6.5 Precision

6.5.1 Repeatability (r) The measured values of the independent test results obtained under repeatability conditions, within the range of the average values given in Table 1, represent the absolute differences between the two test results. For differences not exceeding the repeatability limit (r), the number of cases exceeding the repeatability limit (r) should not exceed 5%. The repeatability limit (r) is determined by linear interpolation based on the data in Table 1. It can be obtained by the method of extension or extrapolation.

7.2.4 Lanthanum chloride solution (50 g/L). Weigh

12.5 g of lanthanum oxide (wLa2O3>=99.99%), place it in a 500 mL beaker, and add a small amount of water. Moisten the solution, add 45 mL of hydrochloric acid (1.1), blow a little water along the wall of the cup, heat until the solution is clear, cool, dilute with water to 250 mL, and mix well.

7.2.5 Aluminum matrix solution (50 g/L). Weigh

13.235 g of aluminum chips (wAl >= 99.99%), place them in a 500 mL beaker, and add.200.00 mL of... Hydrochloric acid (7.2.1), after being gently heated until completely dissolved, is transferred to a 500mL volumetric flask, diluted to the mark with water, and mixed well.

7.2.6 Magnesium oxide standard stock solution. Accurately weigh 1.0000 g of standard magnesium oxide (pre-calcined at 800°C to constant weight) into a.200 mL beaker. Add a small amount of water to the solution and dissolve it in

15.00 mL of hydrochloric acid (1.1). Transfer the solution to a 1000 mL volumetric flask, dilute to the mark with water, and mix well. One mL of the solution contains 1 mg of magnesium oxide.

7.2.7 Magnesium oxide standard solution. Pipette

10.00 mL of magnesium oxide standard stock solution (7.2.6) into a 1000 mL volumetric flask, add 5 mL of... Hydrochloric acid (7.2.1), diluted to the mark with water and mixed well. 1 mL of this solution contains 10 µg of magnesium oxide. Prepare fresh before use.

7.3.1 Sample Weigh

0.50 g of the sample (Chapter 5), accurate to 0.0001 g.

7.3.2 Parallel Tests Perform two parallel experiments and take the average value.

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

7.3.4 Preparation of analytical solutions

7.3.4.1 Sample Dissolution Method I 7.3.4.1.1 Place the sample (7.3.1) into the reaction vessel of the polytetrafluoroethylene sealed sample dissolving apparatus (4.2), add

8.0 mL of hydrochloric acid (7.2.1), and seal the container. Place the reaction cup lid into the PTFE-sealed sample dissolving container (4.2), close the container lid, and place the PTFE-sealed sample dissolving container (4.2) in a steel container. After tightening the steel cover, place it in an oven (4.5), heat it to 240°C±3°C, keep it at that temperature for 6 hours, and then let it cool naturally to room temperature. 7.3.4.1.2 Different operating procedures are adopted according to different magnesium oxide content ranges.

---When the magnesium oxide content (mass fraction) is 0.0010%~0.010%, transfer the solution to a 50mL volumetric flask, and rinse with water to remove any residue. Combine the washing water with the contents of the glass and the volumetric flask, add

10.00 mL of strontium chloride solution (7.2.3), dilute with water to the mark, and mix well.

---When the magnesium oxide content (mass fraction) is >0.010%~0.025%, transfer the solution to a 50mL volumetric flask, and rinse with water to remove any residue. Add the washing water to the volumetric flask, dilute with water to the mark, and mix well. Transfer

20.00 mL to a 50 mL volumetric flask and add...

5.00 mL of strontium chloride solution (7.2.3) was diluted with water to the mark and mixed well.

7.3.4.2 Sample Dissolution Method II

7.3.5 Measurement According to the instrument's operating conditions, on the flame atomic absorption spectrometer (4.1), using an air-acetylene flame, at a wavelength of 285.2 nm, water was used for adjustment. Zero, determine the absorbance of the analytical solution (7.3.4) and the blank solution (7.3.3) prepared along with the sample, and find the corresponding values from the working curve. Mass concentration of magnesium oxide.

7.3.6 Plotting the Working Curve

7.3.6.1 Different working curve plotting methods shall be adopted according to different magnesium oxide content ranges and dissolution methods.

---Sampling method I was adopted. - When the magnesium oxide content (mass fraction) is 0.0010%~0.010%, transfer 0 mL,

0.50 mL,

5.00 mL of magnesium oxide standard solution (7.2.7) were placed in a set of 50 mL volumetric flasks, and then added... Dilute

10.00 mL of aluminum matrix solution (7.2.5) and

10.00 mL of strontium chloride solution (7.2.3) with water to the mark and mix well; - When the magnesium oxide content (mass fraction) is >0.010%~0.025%, transfer 0 mL,

5.00 mL of magnesium oxide standard solution (7.2.7) were placed in a set of 50 mL volumetric flasks, and

4.00 mL of [unspecified ingredient] was added. The aluminum matrix solution (7.2.5) and

5.00 mL of strontium chloride solution (7.2.3) were diluted with water to the mark and mixed well.

---Sampling method II was adopted. - When the magnesium oxide content (mass fraction) is 0.0010%~0.010%, transfer 0 mL,

0.50 mL,

5.00 mL of magnesium oxide standard solution (7.2.7) were placed in a set of 50 mL volumetric flasks, and then added...

10.00 mL of sulfuric acid (7.2.2),

10.00 mL of aluminum matrix solution (7.2.5), and

7.5 Precision

7.5.1 Repeatability (r) The measured values of the independent test results obtained under repeatability conditions, within the range of the average values given in Table 3, represent the absolute differences between these two test results. For differences not exceeding the repeatability limit (r), the number of cases exceeding the repeatability limit (r) should not exceed 5%. The repeatability limit (r) is determined by linear interpolation based on the data in Table 3. It can be obtained by the method of extension or extrapolation.

7.5.2 Reproducibility (R) The measured values of the independent test results obtained under reproducibility conditions, within the range of average values given in Table 4, represent the absolute differences between the two test results. For differences not exceeding the reproducibility limit (R), the percentage exceeding the reproducibility limit (R) should not exceed 5%. The reproducibility limit (R) is determined by using the linear regression method based on the data in Table 4. Obtained by interpolation or extension.