An ion spectrometer is provided, comprising: an ion source, arranged to generate ions continuously with a first range of mass to charge ratios; and an ion trap, arranged to receive ions from the ion source along an axis, and to eject ions with a second range of mass to charge ratios orthogonally to that axis, the second range of mass to charge ratios being narrower than the first range of mass to charge ratios. In some embodiments, ions generated by the ion source continuously flow into the ion trap. Additionally or alternatively, ion optics receive ions ejected from the ion trap and cool the ions without substantial fragmentation. An ion analyser receives ions ejected from the ion trap or ion optics and separates the ions in accordance with at least one characteristic of the ions.

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.

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.

An ion spectrometer is provided, comprising: an ion source, arranged to generate ions continuously with a first range of mass to charge ratios; and an ion trap, arranged to receive ions from the ion source along an axis, and to eject ions with a second range of mass to charge ratios orthogonally to that axis, the second range of mass to charge ratios being narrower than the first range of mass to charge ratios. In some embodiments, ions generated by the ion source continuously flow into the ion trap. Additionally or alternatively, ion optics receive ions ejected from the ion trap and cool the ions without substantial fragmentation. An ion analyser receives ions ejected from the ion trap or ion optics and separates the ions in accordance with at least one characteristic of the ions.

An ion trap is disclosed comprising: a plurality of electrodes which define a toroidal or annular ion confining volume that extends around a central axis; a first device arranged and adapted to apply one or more DC voltages to said plurality of electrodes in order to generate a DC potential well which acts to confine ions in a radial direction within said toroidal or annular ion confining volume, wherein said radial direction is substantially perpendicular to said central axis; and a control system arranged and adapted to non-mass selectively eject ions from said toroidal or annular ion confining volume. The ion trap enables a large number of ions to be trapped and ejected simultaneously.

A method and corresponding devices to reduce the presence of unwanted ions within the pseudo-potential well of the RF fields for inductively coupled plasma mass spectrometry is disclosed. This method reduces space-charge effects and leaves more room available for the ions of interest and, hence, leads to increased transmission of the desired ions into the mass analyzer. In the present invention, the space charge is reduced by adding a low-band resolving DC potential, or a fast sweeping resolving DC potential with a notch, or a fast constant resolving DC potential with a notch, or by adding auxiliary quadrupolar or dipolar RF potential to the quadrupole ion guide, such that all the unwanted ions will be outside the stable region and therefore ejected. This reduces the charge density in the ion beam and ameliorate space charge effects.

A method for driving a linear ion trap having rod electrodes arranged so as to surround a central axis includes: an ion-introducing step for introducing ions into an ion-capturing space surrounded by the rod electrodes, and for capturing the ions by a multipole RF electric field created within the ion-capturing space; and an ion-ejecting step for creating both a DC electric field for ion extraction extending from an external area outside the ion-capturing space into the ion-capturing space through a space between two predetermined rod electrodes neighboring each other around the central axis among the plurality of rod electrodes and the multipole RF electric field, and for sequentially ejecting ions according to their m/z from the ion-capturing space toward the external area through the space between the two predetermined rod electrodes by changing at least one of the multipole RF electric field and the DC electric field.