Patent ID: 7847248
Filing Date: 2010-12-07
Classification: H01J

Abstract:
1. A mass spectrometry apparatus, comprising a first quadrupole; an exit lens; and a linear ion trap disposed between the first quadrupole and the exit lens, the linear ion trap having a well-modulator quadrupole comprising at least two differently potentiated zones, defining at least two different sectors of the linear ion trap such that the linear ion trap operates to form potential wells, alternately or simultaneously, in at least two different sectors of the linear ion trap, the sectors including a proximal sector nearer the first quadrupole and a distal sector nearer the exit lens, whereby an ion population is loaded from said first quadrupole into a well formed in said distal sector and, by manipulation of the potentials of differently potentiated zones of the well-modulator quadrupole, some of those ions are transferred back to said first quadrupole by passage through a well formed in said proximal sector, the proximal sector well retaining a fraction of those ions, thereby preventing overfilling of the linear ion trap.