A method of processing a sample, comprising: utilizing an ion source to generate a plurality of precursor peptide or protein ions from a sample solution containing at least one peptide or protein; scanning a mass range of the precursor ions using a plurality of m/z isolation windows ; subjecting the precursor ions within each of the m/z isolation windows to an electron capture or electron transfer dissociation, ExD, reaction ; detecting product ions resulting from each of the ExD reactions so as to generate a plurality of ExD spectra corresponding to each of the m/z isolation windows, wherein at least a first ExD spectra corresponding to a first m/z isolation window exhibits one or more ExD fragment ions and one or more charge reduced species of the precursor ions within the first m/z isolation window; determining a precursor charge state and a molecular weight for one or more species of the precursor ions within the first m/z isolation window at least partially based on a m/z of the said one or more species of precursor ions within the first m/z isolation window and a m/z of the one or more charge reduced species of the precursor ions; determining a precursor charge state and molecular weight for each of one or more species of precursor ions within each of the m/z isolation windows; determining a precursor charge state pattern across the mass range for each of the precursor charge states of one or more species of precursor ions exhibiting a similar molecular weight; and correlating the one or more ExD fragment ions in the ExD spectra corresponding to each respective m/z isolation window with the precursor charge state pattern for each of the one or more species of precursor ions within said respective m/z isolation window. utilizing an ion source to generate a plurality of precursor peptide or protein ions from a sample solution containing at least one peptide or protein; scanning a mass range of the precursor ions using a plurality of m/z isolation windows ; subjecting the precursor ions within each of the m/z isolation windows to an electron capture or electron transfer dissociation, ExD, reaction ; detecting product ions resulting from each of the ExD reactions so as to generate a plurality of ExD spectra corresponding to each of the m/z isolation windows, wherein at least a first ExD spectra corresponding to a first m/z isolation window exhibits one or more ExD fragment ions and one or more charge reduced species of the precursor ions within the first m/z isolation window; determining a precursor charge state and a molecular weight for one or more species of the precursor ions within the first m/z isolation window at least partially based on a m/z of the said one or more species of precursor ions within the first m/z isolation window and a m/z of the one or more charge reduced species of the precursor ions; determining a precursor charge state and molecular weight for each of one or more species of precursor ions within each of the m/z isolation windows; determining a precursor charge state pattern across the mass range for each of the precursor charge states of one or more species of precursor ions exhibiting a similar molecular weight; and correlating the one or more ExD fragment ions in the ExD spectra corresponding to each respective m/z isolation window with the precursor charge state pattern for each of the one or more species of precursor ions within said respective m/z isolation window. <EOS>