Characterization of an improved electrodynamic ion funnel interface for electrospray ionization mass spectrometry

An improved electrodynamic ion funnel for ion focusing at high pressure (>1 Torr) has been developed for a triple quadrupole mass spectrometer and its performance compared with that of an earlier prototype previously reported . The ion funnel consists of a series of ring electrodes of progressively s maller interval diameters to which rf and de electric potentials are co-app lied, The new design utilizes ring electrodes possessing larger internal di ameters that taper down to a relatively larger exit aperture. in the 1-10 T orr pressure range, the new design provides significant improvement in low m/z ion transmission. Additionally, the overall ion transmission range is i mproved by linked scanning of the ion funnel's rf voltage concomitantly wit h the scanning of the quadrupole mass analyzer. Transmission of a noncovale nt complex through the interface demonstrated that excessive ion heating wa s not problematic. Computer simulations of ion transport support the ion fu nnel design and help explain the relative performance of both designs. Both ion simulations and experimental results are in accord and indicate close to 100% ion transmission efficiency for electrosprayed biopolymer ions thro ugh the interface and into the mass analyzer.