PNNL

Abstract

When coupled with high-performance capillary separations, Fourier transform ion cyclotron (FTICR) mass spectrometry provides powerful new capabilities for proteomic studies. Selective ion accumulation in a quadrupole external to an FTICR mass spectrometer has been shown to increase its sensitivity, dynamic range and duty cycle. In this work we have evaluated operation of a linear quadrupole ion trap coupled to a 3.5 tesla FTICR mass spectrometer in the presence of high space charge. Upon increasing the ion population in the linear quadrupole trap, pronounced m/z discrimination was observed. We have found that superposition of the applied quadrupole rf- and dc-fields, the effective dc-field from space charge within the quadrupole, and the qradrupole fringing fields at the quadrupole entrance and exit result in ion instability and m/z discrimination. After optimizing experimental parameters responsible for m/z discrimination, capillary LC-separated tryptic peptide ions (from a bovine serum albumin digest) were shown to be externally accumulated and detected using the FTICR mass spectrometer without evident m/z discrimination.