The presence of additional fragments influences the ion internal energy calculations, especially at higher internal energies where the alternatives dissociation mechanisms become predominant. The consecutive fragmentation pathways of the p-NO2 BzPy were also studied by guided ion beam MS/MS , and the energy parsing validates the approach of summing the fragments ion intensities at m/z = 106, 90 and 78 with the benzylium fragment, while the m/z 169 signal should be summed with the precursor.