SIMPLIFIED APPLICATION OF QUADRUPOLAR EXCITATION IN FOURIER-TRANSFORMION-CYCLOTRON RESONANCE MASS-SPECTROMETRY

A new method for application of quadrupolar excitation to the trapped ion cell of a Fourier transform ion cyclotron resonance (FTICR) mass s pectrometer is presented. Quadrupolar excitation is conventionally app lied to the two pairs of opposed electrodes that normally perform the excitation and detection functions in the FTICR experiment. Symmetry a rguments and numerically calculated isopotential contours within the t rapped ion cell lead to the conclusion that quadrupolar excitation can be applied to a single pair of opposed side electrodes. Examples of e ffective quadrupolar axialization via this method include a sevenfold signal-to-noise enhancement derived from 50 remeasurements of a single population of trapped bovine insulin ions and the selective isolation of a single charge state of horse heart myoglobin after an initial me asurement that revealed the presence of 14 charge states.