HYBRID MASS SPECTROMETER

A data independent acquisition method of mass spectrometry for analysing a sample within a mass range of interest. The method is performed within a time period based on a width of a chromatographic peak of the sample as it elutes from a chromatography system. The method comprising the steps of ionising the sample to produce a plurality of precursor ions, selecting precursor ions within a mass range of interest to be analysed, performing at least one MS1 scan of the precursor ions and performing a set of MS2 scans. Performing the MS1 scan comprises mass analysing precursor ions across the mass range of interest using a Fourier Transform mass analyser for identification and/or quantitation of the precursor ions in the MS1 domain. Performing the set of MS2 scans comprises 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. The MS2 scan is performed by forming an ion packet from the fragmented ions and injecting the ion packet of fragmented ions into a time of flight mass analyser (150) and mass analysing the fragmented ions.