英语语法分析

HPLC method for the testing of related substances in sultopride hydrochloride was established.

建立盐酸舒托必利注射液中的有关物质的检测方法。

DU 122290 was developed from sultopride and shows improved activity and selectivity. Suggest possible reasons for this.

DU 122290是由舒多普利改进得到的，增强了活性和选择性。请解释可能的理由。