High-Resolution Ion Cyclotron Mobility Spectrometry

A novel ion mobility spectrometry instrument incorporating a cyclotron geometry drift tube is presented. The drift tube consists of eight regions, four curved drift tubes and four ion funnels. Packets of ions are propagated around the drift tube by changing the drift field at a frequency that is resonant with the ion's drift time through each region. The approach trims each packet of ions as it leaves and enters each new region. An electrostatic gate allows ions to be kept in the drift tube for numerous cycles, increasing the ability to resolve specified ions. We demonstrate the approach by isolating the [M + 2H](2+) or [M + 3H](3+) charge state of substance P as well as individual trisaccharide isomers from a mixture of melezitose and raffinose. Resolving powers in excess of 300 are obtainable with this approach.