Ultra pure grade water system

PF (Lot: ST007001, purity: 99.4%) was purchased from Nature Standard (Shanghai, China). Tolbutamide (IS, Lot: 100369-201307, purity: ≥ 98.0%) was purchased from Yuanye Biotechnology (Shanghai, China). Verapamil Hydrochloride (Lot: LGVBJ-ET, purity: 98.0%) was subscribed from TCI (Shanghai, China). The structure of PF and Tolbutamide are shown in Figure 1. Acetonitrile, methanol and dimethyl sulfoxide, up to HPLC grade, were purchased from Merck (KGaA, Darmstadt, Germany). Deionized water was collected from a Milli-Q ultra-pure grade water system (Millipore Corp., Massachusetts, MA, USA). All the other chemicals were of analytical or HPLC grade.

Methanol (MeOH), Methoxyamine hydrochloride (MeOX), N-Methyl-N-(trimethylsilyl) trifluoroacetamide (MSTFA), trimethylchlorosilane (TMCS), and pyridine anhydrous were purchased from Sigma-Aldrich (Merck, Darmstadt, Germany). Internal standards 4-phenylbutyric, myristic acid-d27, and injection standard N-pentadecane were also obtained from Sigma-Aldrich (Merck, Darmstadt, Germany). Acetonitrile, Methyl-tert-butyl-ester (MTBE), and ammonium formate were obtained from CHEM-LAB NV (Zedelgem, Belgium). Deionized water was obtained from a Milli-Q ultra-pure-grade water system (Millipore, Bedford, MA, USA). LC-MS grade Acetonitrile and water used in the RP-HRMS/MS analysis were purchased from Romil Ltd., Cambridge, UK. Metabolite standards and formic acid used in the RP-LC-HRMS/MS analysis were purchased from Sigma-Aldrich (Gillingham, UK). Antibiotics, including metronidazole, vancomycin, kanamycin, gentamycin, colistin, and clindamycin, were purchased from Sigma–Aldrich (St. Louis, MO, USA).