A SEGMENTED RADIOFREQUENCY-ONLY QUADRUPOLE COLLISION CELL FOR MEASUREMENTS OF ION COLLISION CROSS-SECTION ON A TRIPLE QUADRUPOLE MASS-SPECTROMETER

The gas collision cell of a triple quadrupole mass spectrometer has be en modified to consist of ten short quadrupole rod segments that allow an axial field to be applied to the cell in order to make measurement s of ion mobility. The radiofrequency (rf)-quadrupole field provides e ffective radial confinement that greatly reduces diffusional losses at low pressure. The mobilities of mass-selected ions from an ionspray s ource have been measured at a pressure of 8 x 10(-3) torr at electric fields of 0.1 to 3 V/cm, and used to calculate the collision cross sec tions of the ions. The measured cross sections compare well with those measured by other techniques. (C) 1997 American Society for Mass Spec trometry.