The use of preparative high performance liquid chromatography with tandem mass spectrometric directed fraction collection for the isolation and characterisation of drug metabolites in urine by nuclear magnetic resonance spectroscopy and liquid chromatography/sequential mass spectrometry.

Preparative high performance liquid chromatography (HPLC) coupled to tandem mass spectrometry has been used successfully for the isolation of several drug metabolites from urine. Nuclear magnetic resonance (NMR) spectroscopy has been employed to determine the exact chemical structure of these metabolites. The use of preparative HPLC has allowed the isolation of relatively large quantities of drug metabolites (> 0.5 mg) allowing insensitive, information-rich NMR experiments such as NOE, HMBC and HMQC to be performed. The coupling of the ion-trap mass spectrometer, operating in automatic MS/MS mode, to preparative HPLC allows the simultaneous collection and mass spectrometric analysis of eluting analytes to be performed, thus allowing the position of fractions containing drug-related material to be identified very rapidly.