Patent ID: 6111250
Filing Date: 2000-08-29
Classification: H01J

Abstract:
A method of mass analyzing a sample comprising:(a) defining a volume between a set of elongated multipole rods, said volume having an elongated axial dimension and a radial dimension, and further including an entrance and an exit located on the axis,(b) providing a collision gas in said volume,(c) introducing ions at the entrance to the volume,(d) applying an AC potential at least to said rods to confine ions in said volume for passage through the volume from the entrance to the exit,(e) causing ions in said volume to fragment,(f) rapidly varying said ions introduced at the entrance from first ions of a first mass to charge ratio to second ions of a second and different mass to charge ratio, and repeating such rapid variation,(g) detecting ions leaving the exit of the volume, and providing a pause time of selected duration between detection of ions during supply of said first ions and detection of ions during supply of said second ions,(h) and establishing an axial DC electric field in said volume to cause substantially all of said first ions in said volume during said pause time to exit said volume within said pause time.