2.1 Chemicals and Reagents
Imatinib (No. YM-160604) and apatinib (internal standard, IS, No. 668160505) were kindly supplied by Jiangsu Hengrui Medicine Co., Ltd. (Jiangsu, China). Formic acid and ammonium acetate were obtained from Mreda Technology Inc. (Dallas, TX, USA). Ultrapure water was purchased from A.S. Watson & Company (Guangzhou, China). Methanol and acetonitrile were purchased from Fisher Scientific (Fair Lawn, NJ, USA).