An ion funnel interface for improved ion focusing and sensitivity using electrospray ionization mass spectrometry.
To improve upon the already impressive sensitivity achievable with electrospray ionization sources, a novel electrohydrodynamic ion funnel interface has been developed and implemented with a triple-quadrupole mass spectrometer. The ion funnel interface effectively consists of a series of ring electrodes of increasingly small internal diameters to which rf and dc electric potentials are coapplied. In the 1-10-Torr pressure range, the electric fields cause the collisionally damped ions to be more effectively focused and transmitted as a collimated ion beam. This paper describes the ion funnel design and presents an evaluation of its performance using a triple-quadrupole mass spectrometer. Ion transmission and m/z discriminating parameters (resulting in both effective low- and high-m/z cutoffs) are presented based upon both ion current measurements and mass spectra. Electrospray ionization mass spectra of selected protein solutions demonstrated well over 1 order of magnitude increase in signal relative to that of the instrument operated in its standard (inlet capillary-skimmer) configuration under similar conditions. The present results suggest that it will be feasible to realize close to 100% ion transmission efficiency for analytically relevant ions through the electrospray ionization interface and into the mass analyzer.
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 99352, USA.
S A
SA
Shaffer
D C
DC
Prior
G A
GA
Anderson
H R
HR
Udseth
R D
RD
Smith
D000818:Animals; D002417:Cattle; D003574:Cytochrome c Group / Q000032:analysis*; D004912:Erythrocytes / Q000378:metabolism; D006096:Gramicidin / Q000032:analysis*; D006736:Horses; D009206:Myocardium / Q000378:metabolism; D009211:Myoglobin / Q000032:analysis*; D015203:Reproducibility of Results; D018629:Spectrometry, Mass, Secondary Ion / Q000295:instrumentation / Q000379:methods*; D014452:Ubiquitins / Q000032:analysis*
D003574:Cytochrome c Group; D009211:Myoglobin; D014452:Ubiquitins; D006096:Gramicidin