Effects of higher-order multipoles on the performance of a two-plate quadrupole ion trap mass analyzer

Abstract

We report on the effects of varying higher-order multipole components on the performance of a novel radiofrequency quadrupole ion-trap mass analyzer, named the planar Paul trap. The device consists of two parallel ceramic plates, the opposing surfaces of which are lithographically imprinted with 24 concentric metal rings. Using this device, the magnitude and sign of different multipole components, including octopole and dodecapole, can be independently adjusted through altering the voltages applied to each ring. This study presents a systematic investigation of the effects of the octopole and dodecapole field components on the mass resolution and signal intensity of the planar Paul trap. Also, the effect of dipole amplitude and scan speed under both forward and reverse scan modes have been investigated for various combinations of octopole and dodecapole. A trapping field in which the magnitudes of the octopole and dodecapole are, respectively, set to 0% and +8% of the magnitude of the quadrupole yields the highest mass resolution under the conditions studied. A small threshold voltage for dipole resonance ejection is observed for positive octopole, and to a lesser extent for positive dodecapole, but not for negative poles. When both octopole and dodecapole are negative, a reverse scan produces higher resolution, but this effect is not observed when only one of the components is negative.