Applications

Determination of Potassium Oxide in Alumina Powder (Flame Atomic Absorption Spectrometry)

October 10, 2025

1. Method Overview

The sample is dissolved by heating in a quartz beaker with a sulfuric acid-phosphoric acid mixed acid. After dilution with water, an air-acetylene flame is used to measure the absorbance of potassium at a wavelength of 766.5 nm using an atomic absorption spectrometer. Within a certain concentration range, the absorbance of potassium 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 (Model: TAS-990)	1 set	–	Potassium 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	Volume: 50 mL	6 watch glasses
2	Glass Stirring Rod	1 piece	Length: 20 cm	–
3	Electric Furnace	1 set	Temperature-adjustable	–
4	Standard Sieve	1 piece	Mesh size: 0.125 mm	–
5	Adjustable Hot Plate	1 set	Rated temperature range: Room temperature ~ 300 ℃	–
6	Oven	1 set	Rated temperature range: Room temperature ~ 200 ℃	–
7	Micropipette	1 each	Ranges: 100 μL ~ 1000 μL, 1000 μL ~ 5000 μL	–
8	Volumetric Flask	Several	Volume: 100 mL	–
9	Volumetric Flask	1 piece	Volume: 500 mL	–

2.2 Reagents

2.2.1 Raw 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	Remarks
1	Cesium Chloride Solution (1000 μg/mL)	Accurately weigh 0.1 g of cesium chloride into a 100 mL volumetric flask, dilute to the marked volume with deionized water, and mix well.	–
2	Aluminum Matrix Solution	Cover with a watch glass, place on an electric furnace, and heat while shaking to dissolve the sample. After complete dissolution, immediately remove and cool to 40 ℃ ~ 70 ℃. Rinse the watch glass with hot water at 50 ℃, and transfer the washing solution into the original beaker. Rinse the solution into a 500 mL volumetric flask with hot water at 50 ℃, dilute to approximately 400 mL with pure water, shake evenly, cool to room temperature, then dilute to the marked volume with pure water and mix well. Store in a polyethylene bottle. This solution contains 12.5 mg of alumina per 1 mL.	–
3	Nitric Acid Solution (1+99)	Measure 10 mL of nitric acid, pour it into 990 mL of pure water, and mix well.	–

2.3 Reference Standards

2.3.1 Stock Solution

Serial No.	No.	Name	Technical Requirements	Remarks
1	GSB G 62011-90-(1901)	National Potassium Standard Solution	Concentration: 1000 μg/mL	Central Iron and Steel Research Institute

3. Operational Procedures

3.1 Sample Preparation

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 of the sample (accurate to 0.0001 g) 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 furnace, and heat while shaking to dissolve the sample. After complete dissolution, immediately remove and cool to 40 ℃ ~ 70 ℃. Rinse the watch glass with hot water at 50 ℃, and transfer the washing solution into the original beaker. Rinse the sample solution into a 100 mL volumetric flask with hot water at 50 ℃, dilute to approximately 80 mL with pure water, shake evenly, cool to room temperature, then dilute to the marked volume with pure water and mix well for testing. Weigh 0.1323 g of aluminum powder and perform a blank test following the same procedure as the sample.

3.1.2 Preparation of Standard Solutions

Preparation of Potassium Standard Intermediate Solution (100 μg/mL)

Accurately pipette 5 mL of the potassium standard solution (1000 μg/mL) into a 50 mL volumetric flask, dilute to the marked volume with (1+99) nitric acid solution, and mix well.
Preparation of Potassium Standard Series

Pipette 0.0 mL, 0.4 mL, 0.8 mL, and 1.2 mL of the potassium standard intermediate solution (100 μg/mL) into a set of 100 mL volumetric flasks that have been pre-added with 4 mL of aluminum matrix solution respectively. Dilute to the marked volume with pure water, mix well, and store in polyethylene bottles. The concentrations of this potassium standard series are 0.0 μg/mL, 0.4 μg/mL, 0.8 μg/mL, and 1.2 μg/mL.

3.2 Sample Testing

1) Testing Conditions

Reference Conditions for Flame Atomic Absorption Spectrophotometer

Parameter	Specification
Wavelength (nm)	766.5
Spectral Bandwidth (nm)	0.4
Element Lamp Current (mA)	2.0
Burner Height (mm)	5.0
Air Compressor Pressure	0.22 MPa

2) Sample Testing

Use an air-acetylene flame. On the atomic absorption spectrometer, set the wavelength to 766.5 nm, zero the instrument with water, and measure the absorbance. Subtract the absorbance of the “zero-concentration” solution in the standard series, then plot a working curve.