A simplified toroidal ion trap mass analyzer

A radiofrequency toroidal ion trap mass analyzer comprised of four cylindrical electrodes is described. The ion trap consists of two RF electrodes and an AC electrode that surround a central electrode. Mass-analyzed ions are ejected through a slit in the central cylinder. A conversion dynode and electron multiplier are contained within the central cylinder for ion detection. The orientation of the RF and AC electrodes allows for inward-radial ejection of ions, removing the need for ion collection optics. Resolution of the toluene m/z 91 ion was determined for both a forward mass selective instability scan as well as for a reverse scan with resonant ejection. These experiments were performed in parallel with the stretching and compressing of the RF ring electrode spacing. Experimental resolution (Δm) values compare well with previous toroidal ion traps. The stability diagram for the toluene m/z 91 ion is also reported. The diagram possesses a slightly asymmetric profile due to asymmetry of the trapping dimensions as well as the curvature of the toroidal trapping region. Finally, the tandem (MS2) mass spectrum of iso-butylbenzene is reported.

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► A toroidal ion trap mass analyzer utilizing cylindrical electrodes is presented.
► Resolution of toluene m/z 91 is evaluated for both scan direction and higher order multipole components.
► Optimal parameters yield resolution values superior to previously reported toroidal designs.
► The first stability diagram of an ion trap with a toroidal trapping geometry is presented and discussed.
► Tandem (MS2) mass spectrometry of iso-butylbenzene is demonstrated.