Identification of caffeine and its metabolites in human urine extracts by electron ionization tandem spectrometry

Electron impact ionized purine bases such as caffeine and its metabolites (theophylline, theobromine, paraxanthine, 1-methylxanthine, 3-methylxanthine and 7-methylxanthine) were characterized by tandem mass spectrometry. The direct analysis of human urinary extracts by tandem mass spectrometry allows the unambiguous identification of caffeine and its metabolites present simultaneously in the urin