GB/T 20975.34-2020 in English

Method principle and technical characteristics

This standard uses flame atomic absorption spectrometer to determine the sodium content. The technical route is: after the sample is dissolved in hydrochloric acid-hydrogen peroxide, cesium chloride is added to suppress ionization interference, and the absorbance is measured at a characteristic wavelength of 589.0nm. The method has a wide linear range of 0.0010%-0.50%, and the characteristic concentration requirement is ≤0.0075μg/mL.

Quality control requirements

• Precision control: RSD of 10 measurements of high concentration standard solution ≤1.0%, RSD of low concentration solution ≤0.5% of the average absorbance of high concentration
• Linearity verification of working curve: The absorbance difference ratio between the highest and lowest segments ≥0.70
• Blank test: High purity aluminum with Na≤0.0005% must be used as the substrate

Safety warning

The standard particularly emphasizes that experimental personnel must have formal laboratory work experience and use acetylene gas must strictly follow the safety operating procedures, and hydrochloric acid treatment should be carried out in a fume hood.

Compared with the earlier version, the 2020 version of the standard has the following major improvements:

1. Specify the use of BVⅢ grade high-purity hydrochloric acid to prepare reagents
2. Optimize the concentration of cesium chloride solution to 25g/L
3. Add precision data for three content ranges
4. Improve the linear interpolation calculation specification for the reproducibility limit (R)

An aluminum alloy manufacturer uses this standard to test cast aluminum alloy containing 0.12% sodium:

• Weigh 0.5002g of sample and process it according to the process of >0.10-0.50%
• The measured absorbance was 0.342, and the working curve calculated ρ=0.0241mg/mL
• The final result was Na=0.120%, RSD=1.8% (n=5)

The verification showed that the method met the requirement of reproducibility limit of 0.02%.