Improved performance of linear ion trap mass spectrometer with added octopole and dodecapole fields

The geometry of commercial ion trap mass spectrometer has been intentionally distorted. The distortion generates additional higher order multipole components. The non-linear resonance caused by the multipole components results in rapid ejection of ions and mass resolution and mass accuracy was improved. The non-linearity of the ion trap also increases the trap efficiency and improve sensitivity and dynamic range. But excess amount of multipole components degrade the mass isolation performance.
For example, with the sole presence of positive octopole field in addition to quadrupole field, the resonance curve has sharp edge on high frequency side but has gentle slope on low frequency side and that degrades the mass isolation resolution. We have reported that the mass isolation performance was improved by optimizing 3D ion trap geometry. Here we report that the same improvement can be achieved for linear ion trap mass spectrometer.