4. Materials and Methods 4.1. Chemicals and Reagents LKMS was provided by Henan Pulike Biological Engineering Co., Ltd. (Luoyang, China). LC-MS-grade methanol (MeOH), acetonitrile (ACN), and formic acid (FA) were purchased from Fisher Scientific (Pittsburgh, PA, USA). Ultrapure water was purified using a Milli-Q system (Millipore Corporation, Billerica, MA, USA). The following compounds were purchased from Sigma-Aldrich (St. Louis, MO, USA): PH, CAN, BP, TBD, DEX, CLN, and TS.
