A NOVEL ION FUNNEL FOR FOCUSING IONS AT ELEVATED PRESSURE USING ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY

The ability to effectively focus and transmit ions from relatively hig h pressure ion sources is a key factor that affects sensitivity and dy namic range in mass spectrometry, To improve upon the mass spectrometr ic sensitivity achievable with electrospray ionization sources a novel ion funnel interface has been developed and implemented with a triple quadrupole mass spectrometer, The ion funnel effectively consists of a series of ring electrodes of progressively smaller internal diameter to which RF and DC electric fields are co-applied. The electric field s create a pseudo-potential causing the collisionally damped ions to b e more effectively focused and transmitted as a collimated ion beam, T he ion funnel concept we describe is supported by results of SIMION si mulations, ion current measurements and implementation with a mass spe ctrometer, Electrospray ionization mass spectra for an initial ion fun nel configuration demonstrated over an order of magnitude increase in signal relative to that of the instrument operated in its standard (ca pillary inlet-skimmer) configuration under similar conditions, (C) 199 7 John Wiley & Sons, Ltd.