Mass spectrometer and method

A method of determining masses of ions, the method comprising:

• providing a charge detection mass spectrometer comprising an electrostatic sector field ion trap and an inductive charge detector, wherein the electrostatic sector field ion trap comprises a set of electrostatic sectors, including a first electrostatic sector and a second electrostatic sector, wherein the first electrostatic sector and the second electrostatic sector are mutually spaced apart by a field-free region traversed by an ion path, wherein the inductive charge detector is disposed in the field-free region, and wherein the electrostatic sector field ion trap is configured to define, at least in part, the ion path via the inductive charge detector;
• moving, by the electrostatic sector field ion trap, a precursor ion around the ion path defined, at least in part, thereby, via the inductive charge detector;
• inducing, by the moving precursor ion, a signal in the inductive charge detector;
• determining a mass of the precursor ion using the induced signal;
• fragmenting the isolated precursor ion and providing a product ion therefrom;
• and
• determining a mass of the product ion.