Characterisation of oxazepam degradation products by high-performance liquid chromatography/electrospray ionisation mass spectrometry and electrospray ionisation quadrupole time-of-flight tandem mass spectrometry.

Oxazepam has been subjected to controlled degradation at 100 degrees C for 3 h in 0.5 M HCl and 0.5 M NaOH. Following neutralisation of the degradation mixture and removal of salts by solid-phase extraction (SPE), isocratic high-performance liquid chromatography/mass spectrometry (HPLC/MS) using water/methanol (25:75 v/v) as the mobile phase was carried out using a flow diverter to collect fractions prior to their characterisation by electrospray ionisation multi-stage mass spectrometry (ESI-MS(n)) and proposal of the corresponding fragmentation patterns. The elemental compositions of the degradation products and their MS fragments were evaluated using electrospray ionisation quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) which was then used to support the proposed fragmentation patterns.