Method for purifying crude solid phase synthetic liraglutide

A method for purifying crude liraglutide obtained by solid phase synthesis, characterized in that comprises the following steps: Step 1: A solution of crude is obtained by dissolving crude liraglutide liraglutide obtained by solid phase synthesis in aqueous acetonitrile; Step 2: The crude solution liraglutide is subjected to a first purification by HPLC using silica bound octylsilane as stationary phase and using aqueous isopropanol containing 0.1-0.2% trifluoroacetic acid as mobile phase A and acetonitrile containing 0.1-0.2% trifluoroacetic acid as mobile phase B eluting at a linear gradient of 20-40% B 40-60% B, and the target peak is collected as the first fraction; Step 3: The first fraction is subjected to a second HPLC purification using cianosilano attached to silica as stationary phase and using aqueous perchloric acid solution to a 0.05 to 0.15% (mass concentration) as mobile phase A and perchloric acid to 0.05-0.15% (mass concentration) in acetonitrile as mobile phase B at a linear gradient elution from 40% B to 70% B, and the target is collected as the second peak fraction; Step 4: the second fraction is subjected to a third HPLC purification using octylsilane bonded to silica as stationary phase and aqueous ammonia solution using a 0.01 to 0.06% (mass concentration) as mobile phase A and acetonitrile chromatographic grade as mobile phase B at a linear gradient elution from 30% B to 60% B, and the target peak and the third fraction is collected; Step 5: purified peptide of the third fraction obtained by rotary evaporation reduced pressure and lyophilization.