Qualitative and quantitative analysis of ranitidine and its metabolites by high-performance liquid chromatography-mass spectrometry.

Reversed-phase high-performance liquid chromatography systems for the separation of ranitidine and its metabolites ranitidine-N-oxide, ranitidine-S-oxide, and desmethylranitidine have been developed for use in high-performance liquid chromatography-mass spectrometry. A direct liquid introduction-high-performance liquid chromatography-mass spectrometry system to analyse qualitatively and quantitatively solutions containing ranitidine and its metabolites by reversed-phase chromatography is described. A sample of urine collected from a subject given an oral dose of 75 mg of ranitidine and 75 mg of tris-deuterated ranitidine was analysed by this system. Ranitidine and its metabolites were identified by the ion doublets in the mass spectra which were 3 a.m.u. apart.