Lateral introduction of ions into RF ion guides
An ion guide system includes an ion guide with pole rods, a device for laterally introducing an ion species, and a mass spectrometer for analyzing product ions of reactions between different ion species. The device is configured and positioned such that an RF field with at least two-fold rotational symmetry with respect to the axis is generated. The device includes shortened pole rods and/or further electrodes. The pole rods and the further electrodes have at least two-fold rotational symmetry. The symmetry of the RF field allows ions to travel straight ahead through the ion guide with no hindrance. Such arrangements are particularly suitable for bringing together largely loss-free positive and negative ion species for reacting them. The reactions may be used to fragment multiply charged biopolymer ions by electron transfer or to remove excess charges of multiply charged biopolymer ions.
1. An ion guide system, comprising:
an octopole rod set having four opposing rod pairs, of which two opposing rod pairs are shortened at one end thereof such that RF fields with a two-fold rotational symmetry around an axis of the octopole rod set are generated; and
a deflective member located at said end of the octopole rod set opposing the two shortened rod pairs, the deflective member being configured and positioned for allowing passage of ions along the axis of the octopole rod set, and being supplied with DC voltages which deflect ions that are introduced laterally through a gap created by the shortening of two adjacent rods at said end of the octopole rod set.
2. A mass spectrometer for the acquisition of mass spectra of reaction products from reactions of ions of a first ion species with ions of a second ion species, comprising:
an ion source for producing ions of the first ion species;
an ion guide system, comprising an octopole rod set having four opposing rod pairs, of which two opposing rod pairs are shortened at one end thereof such that RF fields with a two-fold rotational symmetry around an axis of the octopole rod set are generated, and a deflective member located at said end of the octopole rod set opposing the two shortened rod pairs, the deflective member being configured and positioned for allowing passage of ions of the first ion species along the axis of the octopole rod set, and being supplied with DC voltages which deflect ions that are introduced laterally through a gap created by the shortening of two adjacent rods at said end of the octopole rod set;
an ion source to produce the ions of the second ion species, which are fed to the gap between ion guide and deflective member; and
a mass analyzer for acquiring the mass spectra of the reaction products.
3. The ion guide system of claim 1 , wherein the deflective member is one of a ring diaphragm and a grid arrangement.
4. The mass spectrometer of claim 2 , wherein the deflective member is one of a ring diaphragm and a grid arrangement.