US 6,111,250 A · Quadrupole with axial DC field

Abstract

In a mass spectrometer, typically a quadrupole, one of the rod sets is constructed to create an axial field, e.g. a DC axial field, thereon. The axial field can be created by tapering the rods, or arranging the rods at angles with respect to each other, or segmenting the rods, or by providing a segmented case around the rods, or by providing resistively coated or segmented auxiliary rods, or by providing a set of conductive metal bands spaced along each rod with a resistive coating between the bands, or by forming each rod as a tube with a resistive exterior coating and a conductive inner coating, or by other appropriate methods. When the axial field is applied to Q0 in a tandem quadrupole set, it speeds passages of ions through Q0 and reduces delay caused by the need to refill Q0 with ions when jumping from low to high mass in Q1. When used as collision cell Q2, the axial field reduces the delay needed for daughter ions to drain out of Q2. The axial field can also be used to help dissociate ions in Q2, either by driving the ions forwardly against the collision gas, or by oscillating the ions axially within the collision cell.

Claims7

Dependent claims

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.

5 more elements

Dependencies are inferred from the claim text.

Quadrupole with axial DC field

Life of this patent

Quadrupole with axial DC field

Life of this patent

Abstract

Claims7