Mass spectrometry methods and systems for high pressure charge state control and/or fragmentation

Abstract

Systems and methods described herein provide for charge state control of multiply-charged anions in a front end, high pressure ion guide. In some example aspects, a mass spectrometer system is provided comprising a first vacuum chamber () maintained at a pressure above about 500 mTorr. At least one ion guide () is disposed within the first vacuum chamber, the at least one ion guide comprising a plurality of rods extending along a central longitudinal axis. A controller () is configured to adjust an amplitude of an RF voltage signal provided to the plurality of rods so as to alternatively operate the ion guide in a first mode of operation with a lower amplitude of the RF voltage signal so as to reduce the likelihood of charge reduction by electron detachment so as to substantially maintain the isotopic distribution of the ions during transmission of ions through the ion guide, and a second mode of operation with a higher amplitude of the RF voltage signal so as to increase the likelihood of electron detachment from ions being transmitted therethrough.