Acetonitrile of high performance liquid chromatography

Leaf and stem saponins of P. notoginseng (PNLSS) were supplied by Wenshan Qi Dan Pharmaceutical Co., Ltd. (Wenshan, Yunnan, China). Ginsenoside standards were obtained from the Shanghai R&D Centre for Standardization of Traditional Chinese Medicine (Shanghai, China). Methanol and acetonitrile of highperformance liquid chromatography (HPLC) grade were purchased from Fisher Scientific Co. (Santa Clara, CA, USA). Leucine–enkephalin, formic acid and sodium acetate were purchased from Sigma–Aldrich (St Louis, MO, USA). Glacial acetic acid was obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). Ultrapure water was prepared with the Milli-Q system (Millipore, Bedford, MA, USA). All other chemicals and regents were of analytical grade or better.