A method of mass spectrometry comprising: ionising a sample eluting from a separation device in order to generate a plurality of parent ions; generating a target list of ions, wherein said target list comprises a predicted mass to charge ratio and at least one of: a predicted chromatographic retention or elution time; and a predicted ion mobility drift time, cross-sectional area or other data relating to ion mobility, derived from a model; performing multiple cycles of operation as said sample elutes from said separation device, wherein each cycle of operation includes: mass filtering said parent ions based on said target list so that selected ions having mass to charge ratios within a first mass to charge ratio range are onwardly transmitted to a fragmentation or reaction device; obtaining parent ion and/or fragment or product ion mass spectral data; comparing or checking said target list based on the ion mass spectral data and updating said model based on said comparing or checking; and adjusting said first mass to charge ratio range that is used to select ions for onward transmission to said fragmentation or reaction device and adjusting the width of said first mass to charge ratio range that is used to select ions for onward transmission to said fragmentation or reaction device in response to said updated model. ionising a sample eluting from a separation device in order to generate a plurality of parent ions; generating a target list of ions, wherein said target list comprises a predicted mass to charge ratio and at least one of: a predicted chromatographic retention or elution time; and a predicted ion mobility drift time, cross-sectional area or other data relating to ion mobility, derived from a model; performing multiple cycles of operation as said sample elutes from said separation device, wherein each cycle of operation includes: mass filtering said parent ions based on said target list so that selected ions having mass to charge ratios within a first mass to charge ratio range are onwardly transmitted to a fragmentation or reaction device; obtaining parent ion and/or fragment or product ion mass spectral data; comparing or checking said target list based on the ion mass spectral data and updating said model based on said comparing or checking; and adjusting said first mass to charge ratio range that is used to select ions for onward transmission to said fragmentation or reaction device and adjusting the width of said first mass to charge ratio range that is used to select ions for onward transmission to said fragmentation or reaction device in response to said updated model. mass filtering said parent ions based on said target list so that selected ions having mass to charge ratios within a first mass to charge ratio range are onwardly transmitted to a fragmentation or reaction device; obtaining parent ion and/or fragment or product ion mass spectral data; comparing or checking said target list based on the ion mass spectral data and updating said model based on said comparing or checking; and adjusting said first mass to charge ratio range that is used to select ions for onward transmission to said fragmentation or reaction device and adjusting the width of said first mass to charge ratio range that is used to select ions for onward transmission to said fragmentation or reaction device in response to said updated model. <EOS>