Comparison of mass spectral techniques using organic peroxides related to artemisinin

The mass spectra of three peroxides related to artemisinin (1) are compared in nine different ionization modes. Ion trap mass spectrometry (MS/MS) spectra reveal numerous pathways for the electron impact (EI) decompositions. In the EI mode, the best spectra are obtained by using the ion trap mass spectrometer at low temperatures. Loss of oxygen is observed with the other EI spectrometers, suggesting catalytic decomposition in the ion source. Methane positive and negative chemical ionization (CI) spectra show considerable fragmentation, while isobutane CI spectra show only (M + H)+ for 1 and (M + H - H2O)+ for dihydroartemisinin (2) and (3). An unusually abundant (2M + H)+ is observed for 1 in both positive-ion plasma desorption and fast atom bombardment mass spectra.