GB/T 5173-1995 is used for the determination of anion active substances in surfactants and detergents, using the direct two-phase Titrimetric method. It is suitable for various related products. The principle is to use anion active substances to react with specific cation reagents in two-phase systems, and determine the content by titration. The standard specifies the required instruments, such as Burette, etc., to clarify the selection and preparation of reagents. Detailed description of Sample Handling steps, including sample dissolving, separation of impurities, etc., as well as titration operation procedures, such as titrant addition speed, endpoint judgment basis. According to this standard, the content of anion active substances can be accurately determined, providing key data for product mass control and performance evaluation.