GB/T 1 2690.8-2003 regulates the determination of the amount of sodium in rare earth metals and their oxides. Using flame atomic absorption spectroscopy (AAS), the sample is first processed to convert the sodium element into a solution state. Sodium atomization is made through a Flame atomization device, and the absorption degree of sodium atoms to specific wavelengths of light is determined by a light spectrum meter, that is, Absorbance. Based on the corresponding relationship between Absorbance and sodium content, the amount of sodium in the sample is accurately calculated. This standard provides a key means for mass control of rare earth products, which helps to ensure the purity of rare earth products. It is widely used in rare earth production and related industries for testing.