US 5,451,782 A · Mass spectometry method with applied signal having off-resonance frequency

Abstract

A mass spectrometry method in which a combined field (comprising a trapping field and a supplemental field) is established and at least one parameter of the combined field is changed to excite ions trapped in the combined field sequentially (such as for detection). The supplemental field is a periodically varying field having an off-resonance frequency, in the sense that the supplemental field frequency nearly matches (but differs from) a frequency of motion of an ion stably trapped by the trapping field alone. Sequential ion excitation in accordance with the invention can rapidly eject a sequence of ions from a trap, or rapidly excite each ion to a degree sufficient for a desired purpose but insufficient for ejection from the trap, because the supplemental field will increase the trajectory of each ion in the sequence and because the supplemental field can have a sufficiently large peak-to-peak amplitude to increase each ion trajectory to a desired magnitude within a desired short time period. The trapped ions can be sequentially excited by holding the supplemental field fixed while changing at least one parameter of the trapping field, or by changing (such as scanning) at least one parameter of the supplemental field while holding the trapping field fixed. The amplitude of the supplemental field is kept sufficiently high to excite ions (via an off-resonance excitation mechanism) before they undergo resonant excitation.

Claims22

Dependent claims

A mass spectrometry method, including the steps of:

(a) establishing a trapping field capable of stably trapping ions having mass to charge ratio within a selected range in a trap region;
(b) superimposing a supplemental field with the trapping field to form a combined field in the trap region, said supplemental field having an off-resonance frequency;
and
(c) changing the combined field to excite selected trapped ions in the trap region, wherein the trapping field is a quadrupole trapping field resulting from application of a voltage to at least one electrode of a quadrupole ion trap apparatus, wherein the supplemental field results from application of a second voltage to at least one electrode of the quadrupole ion trap apparatus, and wherein step (c) includes the step of:
changing a parameter of at least one of the voltage and the second voltage.

2 more elements

Dependencies are inferred from the claim text.

Mass spectometry method with applied signal having off-resonance frequency

Life of this patent

Mass spectometry method with applied signal having off-resonance frequency

Life of this patent

Abstract

Claims22