A composite mass spectrum formed from mass spectral data obtained at different sensitivities

摘要

A mass spectrometer where the ion source 1, ion optics, or gain of the ion detector, is repeatedly switched between a first mode wherein ions are transmitted to the mass analyser 9, preferably an orthogonal acceleration mass analyzer (oaTOF-MS), at a relatively high sensitivity or ion transmission efficiency (figure 3A), and a second mode wherein ions are transmitted at a relatively low sensitivity or ion transmission efficiency (figure 3B). If it is determined that mass spectral data obtained in the first mode is suffering from saturation, distortion, or missed counts, then said data is replaced by suitably scaled mass spectral data obtained in the second mode, in order to from a composite mass spectrum. If problem is severe then the mass spectrum obtained in the first mode may be replaced in its entirety. Preferably the ion optics comprise a y-lens 3 and/or a z-lens 4 to deflect focus, defocus or collimate the beam of ions 2.