 The size of the mass tolerance window typically depends on the mass accuracy and mass resolution of the instrument collecting the data.This is useful for re-examining data to detect previously-unsuspected analytes, to highlight potential isomers, resolve suspected co-eluting substances, or to provide clean chromatograms of compounds of interest.An extracted-ion chromatogram is generated by separating the ions of interest from a data file containing the full mass spectrum over time after the fact; this is different from selected-ion chromatograms, discussed below, in which data is collected only for specific m/z values.