vial through the Econofilter PTFE (13 mm, 0.2 µm) syringe filter (Aijiren Techno-logies, China) and stored at -20 °C. LC-MS/MS analysis The Aijiren series liquid chroma-tograph, consisting of vacuum degasser, binary pump, autosampler and thermo-stated column compartment was used for separation of analytes, whose detection