A method of obtaining and analyzing a chromatography / mass spectrometry spectrum of a sample comprising at least two components, having the following steps: a) setting a current value of a first energy level and a current value of a second energy level, wherein the first energy level promotes fragmentation or reaction of precursor ions within a collision cell within which a collision energy of the first energy level is applied to the precursor ions and wherein the second energy level corresponds to few or no precursor ions being fragmented or reacted within a collision cell within which a collision energy of the second energy level is applied to the precursor ions; b) separating the components of the sample using a chromatographic column; c) ionizing a portion of the separated components so as create the precursor ions; d) introducing a first portion of the precursor ions into a collision cell under application of a collision energy of the first energy level to the first portion of the precursor ions so as to generate a first sub-population of ions corresponding to the first energy level; e) separately introducing a second portion of the precursor ions into the same or a different collision cell under application of a collision energy of the second energy level to the second portion of the precursor ions so as to generate a second sub-population of ions corresponding to the second energy level; f) transferring a mixture of the first sub-population of ions and the second sub-population of ions into a mass analyzer; g) producing a mass-to-charge analysis of the ions of the mixture of the first and second sub-populations of ions using the mass analyzer; h) expelling the first and second sub-populations of ions from the mass analyzer; i) varying the current value of the first energy level according to a pre-determined cyclical variation of energy, wherein said variation causes a change in the extent and mechanism of fragmentation or reaction of the first portion of the precursor ions; j) repeating steps c) through g); and k) producing an analysis of a time-variation of the mass-to-charge analyses. a) setting a current value of a first energy level and a current value of a second energy level, wherein the first energy level promotes fragmentation or reaction of precursor ions within a collision cell within which a collision energy of the first energy level is applied to the precursor ions and wherein the second energy level corresponds to few or no precursor ions being fragmented or reacted within a collision cell within which a collision energy of the second energy level is applied to the precursor ions; b) separating the components of the sample using a chromatographic column; c) ionizing a portion of the separated components so as create the precursor ions; d) introducing a first portion of the precursor ions into a collision cell under application of a collision energy of the first energy level to the first portion of the precursor ions so as to generate a first sub-population of ions corresponding to the first energy level; e) separately introducing a second portion of the precursor ions into the same or a different collision cell under application of a collision energy of the second energy level to the second portion of the precursor ions so as to generate a second sub-population of ions corresponding to the second energy level; f) transferring a mixture of the first sub-population of ions and the second sub-population of ions into a mass analyzer; g) producing a mass-to-charge analysis of the ions of the mixture of the first and second sub-populations of ions using the mass analyzer; h) expelling the first and second sub-populations of ions from the mass analyzer; i) varying the current value of the first energy level according to a pre-determined cyclical variation of energy, wherein said variation causes a change in the extent and mechanism of fragmentation or reaction of the first portion of the precursor ions; j) repeating steps c) through g); and k) producing an analysis of a time-variation of the mass-to-charge analyses.