SIMION analysis of a high performance linear accumulation octopole with enhanced ejection capabilities

Here, we present the results of extensive SIMION 7.0 modelling of a new linear octopole ion trap. The octopole was designed to increase the efficiency of an electrospray ion source coupled to a Fourier Transform Ion Cyclotron Resonance (FTICR) mass spectrometer. This improvement was achieved by applying a pulsed axial field to the octopole to eject the ion packet with a time and energy distribution that better match the acceptance criteria of the FTICR cell, thus increasing the trapping efficiency and sensitivity. The axial field was produced by applying a pulsed dc potential to the custom-designed ejection electrodes located between the octopole rods. The time and energy profiles of the ejected ion packets for several electrode shapes were calculated and are discussed in terms of their compatibility with efficient trapping of the ion packet in the FTICR cell. Preliminary experimental results show increased signal using the dc ejection electrodes of approximately 100%.