Method for detecting related substances in oseltamivir phosphate starting material

The invention relates to a method for detecting related substances in an oseltamivir phosphate starting material. The oseltamivir phosphate starting material is 5-(pentane-3-yloxy) 7-oxo-bicyclo [4.1. 0] hept-3-ene-3-carboxylic acid ethyl ester, and the oseltamivir phosphate starting material is 5-(pentane-3-yloxy) 7-oxo-bicyclo [4.1. 0] hept-3-ene-3-carboxylic acid ethyl ester. According to the detection method, 5-(pentane-3-yloxy) 7-oxo-bicyclo [4.1. 0] hept-3-ene-3-carboxylic acid ethyl ester and seven related substance impurities thereof are detected by using a reversed-phase high-performance liquid chromatography and using acetonitrile-water as a flowing phase, and C10-SM1-ZZ9 is a process source of an impurity C10-ZZF (an impurity F in EP9.0) in an oseltamivir phosphate finished product. According to the detection method, the content of C10-SM1-ZZ9 can be quantitatively detected and is equal to 0.0084% of the concentration of a test sample, and the content of impurity F in a finished product can be effe