PNNL

Abstract

A key component of FT-ICR mass spectrometers is the trapped ion cell, where analyte ions are confined for excitation and detection. Recent advances in superconducting magnet technology make possible the construction of magnets with higher magnetic fields and regions of improved homogeneity, setting the stage for major advances in FT-ICR performance metrics. In particular, fitting next generation superconducting magnets with ICR cells incorporating harmonic trapping electric fields, suitably configured with electrodes for manipulating and detecting ions, will simultaneously improve resolving power, mass measurement accuracy, dynamic range and sensitivity of FT-ICR MS. Here, a focused conceptual approach for achieving cell harmonization is presented, using as a metric, the spatial uniformity of the radial electric field divided by radius. This new concept for cell harmonization utilizing external shims and two proof-of-principle examples for externally shimmed cell configurations developed using 3D potential calculations are described. These designs are based on a series of external electrodes that serve to generate the trapping potential and are electrically de-coupled from the detection and excitation electrodes. A nearly ideal 3D quadrupolar potential is achieved throughout the cell volume while simplifying electrical and mechanical connections for FT-ICR cells.