Stability behaviour of antiretroviral drugs and their combinations. 1: characterization of tenofovir disoproxil fumarate degradation products by mass spectrometry

Tenofovir disoproxil fumarate (TDF), an antiretroviral drug, was evaluated for its degradation behaviour in solid and solution states. A total of twelve non-volatile degradation products were formed, which were separated on a C18 column in a gradient mode, using methanol and ammonium formate in the mobile phase. The same method was extended to liquid chromatography-high resolution mass spectrometry (LC-HRMS). First a comprehensive mass fragmentation pattern of the drug was established by direct injection and collection of HRMS and multi-stage tandem mass spectrometric (MSn) data. Then LC-HRMS studies were carried on the stability samples containing the degradation products. Also headspace gas chromatography-mass spectrometry (HS-GC-MS) studies were conducted to explore the formation of volatile components. The collated information was utilized for the characterization of all non-volatile and volatile degradation products. Eventually, the degradation pathway of the drug was established under the investigated conditions.