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 50mgkg⁻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 5mgkg⁻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 0–12h post-dose samples. Dosing at 50mgkg⁻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.