Metabolism of 3-chloro-4-fluoroaniline in rat using [14C]-radiolabelling, 19F-NMR spectroscopy, HPLC-MS/MS, HPLC-ICPMS and HPLC-NMR

The metabolic fate of 3-chloro-4-fluoroaniline was investigated in rat following intraperitoneal (i.p.) administration at 5 and 50 mg kg−1 using a combination of HPLC-MS, HPLC-MS/MS, 19F-NMR spectroscopy, HPLC-NMR spectroscopy and high-pressure liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICPMS) with 35Cl and 34S detection. The metabolism of 3-chloro-4-fluoroaniline at both doses was rapid and extensive, to a large number of metabolites, with little unchanged compound excreted via the urine. Dosing at 5 mg kg−1 with [14C]-labelled compound enabled the comparison of standard radioassay analysis methods with 19F-NMR spectroscopy. 19F-NMR resonances were only readily detectable in the 0–12 h post-dose samples. Dosing at 50 mg kg−1 allowed the facile and specific detection and quantification of metabolites by 19F-NMR spectroscopy. Metabolite profiling was also possible at this dose level using HPLC-ICPMS with 35Cl-specific detection. The principal metabolites of 3-chloro-4-fluoroaniline were identified as 2-amino-4-chloro-5-fluorophenyl sulfate and 2-acetamido-4-chloro-5-fluorophenyl glucuronide. N-acetylation and hydroxylation followed by O-sulfation were the major metabolic transformations observed.