PRODUCT ION NODES IN MS MS

The transmission of ions through an RF-only quadrupole collision cell is affected by both the frequency and voltage applied to the quadrupol e. With a change in the RF-only quadrupole collision cell voltage (viz , the collision energy) ion intensities for both parent and product io ns determined by a final mass-analyzing quadrupole vary in a modulated fashion. This pattern of ion intensities has been described as quadru pole ''nodes''. Ion transmission through the RF-only quadrupole has be en carefully investigated here using energy-resolved mass spectrometry with variations in the collision cell pressure and the mass of the io ns. A theory is developed to explain the presence of product ion nodes that focuses on ion velocity as the critical parameter in their produ ction.