Initial implementation of an electrodynamic ion funnel with Fourier transform ion cyclotron resonance mass spectrometry.

Fourier transform ion cyclotron resonance (FTICR) mass spectrometry has become a widely used method to study biopolymers. The method, in combination with an electrospray ionization (ESI) source has demonstrated the highest resolution and accuracy yet achieved for characterization of biomolecules and their noncovalent complexes. The most common design for the ESI interface includes a heated capillary inlet followed by a skimmer having a small orifice to limit gas conductance between a higher pressure (1 to 5 torr) source region and the lower pressure ion guide. The ion losses in the capillary-skimmer interface are large (estimated to be more than 90%) and thus reduce achievable sensitivity. In this work, we report on the initial implementation of a newly developed electrodynamic ion funnel in a 3.5 tesla ESI-FTICR mass spectrometer. The initial results show dramatically improved ion transmission as compared to the conventional capillary-skimmer arrangement. An estimated detection limit of 30 zeptomoles (approximately 18,000 molecules) has been achieved for the analysis of the proteins with molecular weights ranging from 8 to 20 kDa.