Chemicals

Vitacoxib chewable tablets (30 mg/tablet) and pure vitacoxib powder (purity ≥ 99.8%, HPLC grade) were donated by Beijing Orbiepharm Co., Ltd (Beijing, PR China). Two main metabolites 4-(4-chloro-1-(5-(methyl sulfonyl) pyridin-2-yl)-1H-imidazol-5-yl) phenyl) methanol (M1) and 4-(4-chloro-1-(5-(methyl sulfonyl) pyridin-2-yl)-1H-imidazol-5-yl) benzoic acid (M2) (purity ≥ 98%) were synthesized by Beijing Orbiepharm Co., Ltd. Acetonitrile (HPLC grade), methyl tert-butyl ether (HPLC grade), and formic acid (LC/MS grade) were obtained from Fisher Scientific Co. (NJ, USA). Water for HPLC was purified using a Milli-Q Synthesis system (Millipore, MA, USA). Cyclophosphamide and carboxymethyl cellulose sodium (CMC-Na) were obtained from Tianjin Chemical Reagent Company (Tianjin, China). All other reagents and chemicals were of chromatography grade and supplied by Beijing Chemical Reagent Co., (Beijing, China).