A data independent acquisition method of mass spectrometry for analyzing a sample within a mass range of interest as it elutes from a chromatography system. The method comprises selecting precursor ions within a mass range of interest to be analyzed, performing at least one MS1 scan of the precursor ions using a Fourier Transform mass analyser and performing a set of MS2 scans by segmenting the precursor ions into a plurality of precursor mass segments, each precursor mass segment having a mass range of no greater than 5 amu, and for each precursor mass segment fragmenting the precursor ions within that precursor mass segment and performing an MS2 scan of the fragmented ions.