Distance-of-flight mass spectrometry: a new paradigm for mass separation and detection.

Distance-of-flight mass spectrometry (DOFMS) offers the advantages of physical separation of ions, array detection of ions, focusing of initial ion energy, great simplicity, and a truly unlimited mass range. DOFMS instrumentation is similar to that of time-of-flight mass spectrometry (TOFMS) and shares its ion-source versatility, batch analysis, and rapid spectral-generation rate. With constant-momentum ion acceleration and an ion mirror, there is a time at which ions of all mass-to-charge values are energy focused at their particular distances along the flight path. A pulsed field orthogonal to the flight path drives the ions to reach the detector array at this specific time. Results from a 0.29-m proof-of-principle instrument verify the theoretically predicted energy focus and demonstrate how the range of mass-to-charge values that impinge on the detector array can be readily changed. DOFMS could be combined sequentially with TOFMS to enable simultaneous scanless tandem mass spectrometry.