TYL was brought from Hengtong Guanghua Factory (Xi’an, China), and ROX, SPM, JOS, and CLA were from European Pharmacopoeia (EDQM, Strasbourg, France). KIT, ERY, TIL, TUL, and AZI were obtained from Sigma Chemicals Co. (St. Louis, MO, USA). MED was obtained from the China Institute of veterinary drugs control (Beijing, China). The purity of each analytical standard is higher than 92.5%. The chromatographic grade methanol, acetonitrile, and formic acid (FA) were purchased from Fisher Scientific (Fairlawn, NJ, USA). Other organic solvents such as ammonium hydroxide, acetic acid, and chloroform were analytical grade and brought from Guangzhou Chemical Reagent Factory (Guangzhou, China). Ultrapure deionized water was produced by a Millipore MilliQ water system (Molsheim, France). C18 (200 mg, 3 mL) and SCX (60 mg, 3 mL) SPE cartridges were available from Agilent Technologies Co. (Santa Clara, CA, USA). The Oasis HLB cartridge (60 mg, 3 mL) was obtained from Waters Co. (Milford, MA, USA).
The stock standard solution (1.0 mg/mL) of each compound was prepared by dissolving 10 mg of analytical standard in 10 mL of methanol and can be stored at −20 °C for 3 months. Working solutions were obtained by diluting the stock solution with methanol, daily, according to practical requirements.
The stock standard solution (1.0 mg/mL) of each compound was prepared by dissolving 10 mg of analytical standard in 10 mL of methanol and can be stored at −20 °C for 3 months. Working solutions were obtained by diluting the stock solution with methanol, daily, according to practical requirements.