Mass spectrometer and method of mass spectrometry

A mass spectrometer for performing mass spectrometry on a sample across a mass range of interest, the mass spectrometer comprising:

• an ionization source for producing a plurality of precursor ions from the sample provided by a chromatography system;
• a mass selector for selecting a mass range of the precursor ions;
• a mass analyzer for performing an MS1 scan of the precursor ions in the MS1 domain;
• a fragmentation apparatus;
• a mass analyzer for performing an MS2 scan of fragmented ions in the MS2 domain;
• an ion packet or ion pulse forming apparatus;
• and a controller configured to:
• (i) cause the mass selector to select precursor ions within the mass range of interest,
• (ii) cause the mass analyzer for performing an MS1 scan to perform an MS1 scan of the precursor ions within the mass range of interest to obtain a MS1 spectrum of the precursor ions in the MS1 domain,
• (iii) determine ion intensity values within the MS1 spectrum,
• (iv) cause the mass selector to select within the mass range of interest a plurality of precursor mass segments, each precursor mass segment having a mass range,
• (v) control an amount of fragmented ions for each precursor mass segment, based on an intensity value for that precursor mass segment derived from the MS1 spectrum,
• (vi) cause the fragmentation apparatus to fragment the precursor ions within each precursor mass segment,
• (vii) cause the ion packet or ion pulse forming apparatus to form the amount of fragmented ions as one or more ion packets or ion pulses and to inject the ion packets or ion pulses of fragmented ions into the mass analyzer for performing an MS2 scan,
• (viii) cause the mass analyzer for performing an MS2 scan to mass analyze the amount of fragmented ions of the one or more ion packets or ion pulses.