Multipole ion mass filter having rotating electric field

An apparatus for filtering non-selected ions and passing selected ions according to a mass-to-charge ratio, the selected ions having a secular frequency, the apparatus comprising:

• a plurality of elongated electrodes, the elongated electrodes positioned substantially parallel to an axis;
• and
• a power supply in electrical communication with the plurality of elongated electrodes, the power supply generating two voltage components, the first voltage component having a first amplitude and a first frequency, the second voltage component having a second amplitude and a second frequency;
• wherein the second frequency is substantially equal to a secular frequency of motion for the selected ion and the second frequency component provided to each elongated electrode has a different phase.

An apparatus for filtering non-selected ions and passing selected ions according to a mass-to-charge ratio, the selected ions having a secular frequency, the apparatus comprising:

• a plurality of elongated electrodes, the elongated electrodes positioned substantially parallel to an axis;
• a power supply in electrical communication with the plurality of elongated electrodes, the power supply generating two voltage components, the first voltage component having a first amplitude and a first frequency, the second voltage component having a second amplitude and a second frequency, wherein the second frequency is substantially equal to a secular frequency of motion for the selected ion and the second frequency component provided to each elongated electrode has a different phase;
• an ion source positioned upstream from the elongated electrodes;
• and
• an ion detector positioned downstream from the plurality of elongated electrodes.

An apparatus for filtering non-selected ions and passing selected ions according to a mass-to-charge ratio, the selected ions having a secular frequency, the apparatus comprising:

• four elongated electrodes, the elongated electrodes positioned substantially parallel to and equidistant from an axis;
• a circular disk positioned downstream from the elongated electrodes, the circular disk being substantially orthogonal to and centered on the axis;
• and
• a power supply in electrical communication with the four elongated electrodes, the power supply generating two voltage components, the first voltage component having a first amplitude and a first frequency, the second voltage component having a second amplitude and a second frequency;
• wherein the second frequency is substantially equal to a secular frequency of motion for the ion and the second frequency component provided to the first electrode has a first phase, the second frequency provided to the second electrode is shifted about 90° from the first phase, the second frequency provided to the third electrode is shifted about 180° from the first phase, and the second frequency provided to the fourth electrode is shifted about 270° from the first phase;
• wherein ions travel along the axis and between the elongated electrodes and the second voltage component urges at least some of the ions traveling between the elongated electrodes into a generally spiral trajectory extending around the axis and the radii of the spiral trajectories for the selected ions is generally greater than the radius of the circular disk and the radii of the non-selected ions is generally less than the radius of the circular disk.