The GB/T 20166.2-2012 standard specifies a method for the determination of fluorine content in rare earth polishing powders based on cerium-based rare earths. This method uses a fluorine ion selective electrode to determine the fluorine content after the sample is melted with alkali. The specific steps include alkali melting of the sample, leaching and infiltrating, and using a fluorine Ion selective electrode in a buffer solution with a pH value of 6.5~ 7.0 for measurement. This standard applies to rare earth polishing powders with a fluorine content range of 0.01%~ 10.0%, ensuring the Reliability of accurate determination of fluorine content.