2.1 Chemicals and reagents
TGC (CAT Number: T440015) and internal standard TGC-d9 (CAT Number:
440017) were purchased from Toronto Research Chemicals INC (Toronto,
Canada). HPLC-grade and acetonitrile were obtained from Sigma-Alorich
(St.Louis, USA). Ammonium formate was provided by Guangfu Fine Chemical
Research Institute (Tianjin, China) and formic acid was provided by
Kemiou Chemical Reagent Co. Ltd (Tianjin, China).