Study of forced degradation behaviour of cobicistat and atazanavir using LC/ESI/QTOF/MS; a combination of in-sourced and collision-induced dissociation for evaluation of the fragmentation patterns of degradation products
The present study describes the characterization of degradation products of cobicistat and atazanavir through mass spectrometry tools. Initially, cobicistat and atazanavir were subjected to stress degradation under different stress conditions. A single UPLC/PDA method was developed and applied separately for analysing the stressed samples of cobicistat and atazanavir. The degradation products were subjected to in-source fragmentation followed by collision-induced dissociations (CIDs) to produce further product ions simulating the MS3 step of ion-trap. This approach was applied to characterize five degradation products of cobicistat while the remaining degradation products of cobicistat and atazanavir were characterized by LC/QTOF/MS/MS experiments. Once the molecular weight of the degradation products was determined, various fragmentor voltages were applied to induce in-source fragmentation. These product ions were then further fragmented using conventional MS/MS, and the resulting spectra were analyzed to postulate the structures of rearranged product ions. All the data obtained from these studies provided valuable information on the fragmentation pathways of the degradation products of cobicistat and atazanavir. The developed UPLC/PDA method was validated with respect to the accuracy, precision, linearity, and robustness validation parameters.