Applications

Determination of Sodium Oxide in Aluminum Oxide Powder (Flame Atomic Absorption Spectrometry)

September 18, 2025

1. Method Overview

The sample is dissolved by heating in a quartz beaker using a mixed acid of sulfuric acid and phosphoric acid. An air-acetylene flame is employed, and the absorbance of sodium oxide is measured at a wavelength of 589.0 nm using an atomic absorption spectrometer. Within a certain concentration range, the absorbance of sodium is proportional to its content, and quantitative determination is performed by comparison with a standard series.

2. Instruments and Reagents

2.1 Instruments and Equipment

2.1.1 Testing Instruments

Serial No.	Name	Quantity	Technical Requirements	Accessories
1	Atomic Absorption Spectrophotometer (TAS-990)	1 set	–	Sodium Hollow Cathode Lamp
2	Air Compressor	1 set	Rated discharge pressure: 0.3 MPa	–
3	Acetylene Gas	1 cylinder	Purity ≥ 99.99%	–

2.1.2 Sample Pretreatment Equipment

Serial No.	Name	Quantity	Technical Requirements	Accessories
1	Quartz Beaker	6 pieces	50 mL	6 watch glasses
2	Glass Stirring Rod	1 piece	20 cm	–
3	Electric Stove	1 set	Temperature-adjustable	–
4	Standard Sieve	1 piece	0.125 mm	–
5	Adjustable Hot Plate	1 set	Rated temperature: Room temperature ~ 300℃	–
6	Oven	1 set	Rated temperature: Room temperature ~ 200℃	–
7	Micropipette	1 each	100 μL ~ 1000 μL; 1000 μL ~ 5000 μL	–
8	Volumetric Flask	Several	100 mL	–
9	Volumetric Flask	1 piece	500 mL	–

2.2 Reagents

2.2.1 Reagents

Serial No.	Name	Technical Requirements	Remarks
1	Sulfuric Acid	Guaranteed Reagent (GR)	–
2	Phosphoric Acid	Guaranteed Reagent (GR)	–
3	Aluminum Powder	Guaranteed Reagent (GR)	–
4	Cesium Chloride	Guaranteed Reagent (GR)	–

2.2.2 Prepared Reagents

Serial No.	Name	Preparation Method
1	Aluminum Matrix Solution	Accurately weigh 3.306 g of aluminum powder into a 50 mL quartz beaker. Add 125 mL of phosphoric acid and 25 mL of sulfuric acid, cover with a watch glass, and heat the beaker on an electric stove while shaking to dissolve the sample. After complete dissolution, immediately remove the beaker and cool it to 40℃ ~ 70℃. Rinse the watch glass with hot water (50℃), and transfer the rinsing solution into the original beaker. Wash the solution into a 500 mL volumetric flask using hot water (50℃), dilute with pure water to approximately 400 mL, shake evenly, cool to room temperature, then dilute to the marked volume with pure water, mix well, and store in a polyethylene bottle. This solution contains 12.5 mg of aluminum oxide per 1 mL.
2	Nitric Acid Solution (1+99)	Measure 10 mL of nitric acid, pour it into 990 mL of pure water, and shake well.

2.3 Reference Standards

2.3.1 Stock Solution

Serial No.	No.	Name	Technical Requirements	Remarks
1	GSBG62004-90-(1101)	Sodium Single-Element Standard Solution	1000 μg/mL	Central Iron and Steel Research Institute

3. Operational Procedures

3.1 Sample Handling

3.1.1 Preparation of Test Solution

Sample Pretreatment:
Pass the sample through a 0.125 mm standard sieve, dry it in an oven at 300℃ ± 10℃ for 2 hours, and cool to room temperature.
Sample Digestion:
Weigh 0.25 g (accurate to 0.0001 g) of the sample into a 50 mL quartz beaker. Add 25 mL of phosphoric acid and 5 mL of sulfuric acid, cover with a watch glass, place on an electric stove, and heat while shaking to dissolve the sample. After complete dissolution, immediately remove the beaker and cool it to 40℃ ~ 70℃. Rinse the watch glass with hot water (50℃), and transfer the rinsing solution into the original beaker. Wash the sample solution into a 100 mL volumetric flask using hot water (50℃), dilute with pure water to approximately 80 mL, shake evenly, cool to room temperature, then dilute to the marked volume with pure water, mix well, and set aside for testing. Weigh 0.1323 g of aluminum powder and perform a blank test alongside the sample.

3.1.2 Preparation of Standard Solutions

Preparation of Sodium Standard Intermediate Solution (100 μg/mL):
Accurately pipette 5 mL of the sodium standard solution (1000 μg/mL) into a 50 mL volumetric flask, and dilute to the marked volume with nitric acid solution (1+99), shake well.
Preparation of Sodium Standard Series:
Accurately pipette 0.0 mL, 0.4 mL, 0.8 mL, 1.2 mL, 1.6 mL, and 2.0 mL of the sodium standard intermediate solution (100 μg/mL) respectively into a set of 100 mL volumetric flasks that have been pre-added with 8 mL of aluminum matrix solution. Dilute to the marked volume with pure water, mix well, and store in polyethylene bottles. The concentrations of this sodium standard series are 0.0 μg/mL, 0.4 μg/mL, 0.8 μg/mL, 1.2 μg/mL, 1.6 μg/mL, and 2.0 μg/mL.

3.2 Sample Testing

Testing Conditions
Reference Conditions for Flame Atomic Absorption Spectrophotometer Detection

Parameter	Specification
Wavelength (nm)	589.0
Spectral Bandwidth (nm)	0.4
Element Lamp Current (mA)	2.0
Fuel Gas Flow Rate (mL/min)	1300
Burner Height (mm)	5.0
Air Compressor Pressure	0.22 MPa

Sample Testing:
Use an air-acetylene flame. At a wavelength of 589.0 nm on the atomic absorption spectrometer, zero the instrument with water, measure the absorbance, subtract the absorbance of the “zero-concentration” solution in the standard series, and draw a working curve.