US 6,674,067 B2 · Methods and apparatus to control charge neutralization reactions in ion traps

Abstract

An ion trap mass spectrometer uses electrospray ionization to introduce multiply-charged positive ions in an axial direction into a quadrupole ion trap and glow discharge ionization to introduce singly-charged negative ions in a radial direction into the ion trap. Methods of controlling ion-to-ion charge transfer reactions include applying a combination of a dipolar DC voltage and a dipolar RF voltage across endcap electrodes to allow partial charge state neutralization reactions to occur between the positive and negative ions and then control suspension and resumption of further charge state neutralization reactions. The remaining ions can be further processed and transformed and a mass spectrum created by scanning a quadrupolar RF field.

Claims33

Dependent claims

A method of controlling an ion trap comprising the steps of

generating a trapping RF field for simultaneous trapping of positive ions and negative ions,
trapping first ions having charge states of one polarity by the trapping RF field,
trapping second ions having charge states of opposite polarity by the trapping RF field,
at least one of the first ions and second ions being in a multiply-charged state,
generating a DC field having a variable amplitude,
generating a supplemental RF field having a variable frequency,
applying a combination of the DC field at a selected amplitude and the supplemental RF field at at least one selected frequency to control charge state neutralization reactions between the first ions and second ions and migrate at least certain of the multiply-charged state ions to at least one lesser charge state having a higher mass-to-charge ratio.

4 more elements

Dependencies are inferred from the claim text.

Methods and apparatus to control charge neutralization reactions in ion traps

Life of this patent

Methods and apparatus to control charge neutralization reactions in ion traps

Life of this patent

Abstract

Claims33