Reducing AC effects on ions entering ion guide with pulsing auxiliary AC

A method for sequentially ejecting ions from an ion guide according to mass-to-charge ratio (m/z) value using a ramped alternating current (AC) voltage while reducing or eliminating the effects of the AC voltage on ions entering the ion guide, comprising:

• during an accumulation time period of each time cycle of an ion guide and before an AC time period of the each time cycle in which a ramped AC voltage is applied to at least one set of axial rods of the ion guide to eject ions according to m/z value, receiving ions from outside of the ion guide through an entrance aperture of the ion guide and into a first cell of the ion guide, applying a low direct current (DC) voltage to a barrier electrode of the ion guide to receive ions from the first cell into a second cell of the ion guide, and applying a high DC voltage to an exit electrode of the ion guide to prevent ions from exiting the ion guide using a processor,
• wherein the entrance aperture is located at one end of the at least one set of axial rods, the exit electrode is located at the other end of the at least one set of axial rods, and the barrier electrode is located between the entrance aperture and the exit electrode and separates the ion guide into the first cell before the barrier electrode and the second cell after the barrier electrode;
• and
• during a cooling time period of the each time cycle and before the AC time period, applying a high DC voltage to the barrier electrode to trap and cool ions in the second cell and to allow ions to continue to be received into the first cell without being affected by the ramped AC voltage using the processor.

A computer program product, comprising a non-transitory tangible computer-readable storage medium whose contents include a program with instructions being executed on a processor so as to perform a method for sequentially ejecting ions from an ion guide according to mass-to-charge ratio (m/z) value using a ramped alternating current (AC) voltage while reducing or eliminating the effects of the AC voltage on ions entering the ion guide, comprising:

• providing a system, wherein the system comprises one or more distinct software modules, and wherein the distinct software modules comprise a control module;
• during an accumulation time period of each time cycle of an ion guide and before an AC time period of the each time cycle in which a ramped AC voltage is applied to at least one set of axial rods of the ion guide to eject ions according to m/z value, receiving ions from outside of the ion guide through an entrance aperture of the ion guide and into a first cell of the ion guide, applying a low direct current (DC) voltage to a barrier electrode of the ion guide to receive ions from the first cell into a second cell of the ion guide, and applying a high DC voltage to an exit electrode of the ion guide to prevent ions from exiting the ion guide using the control module,
• wherein the entrance aperture is located at one end of the at least one set of axial rods, the exit electrode is located at the other end of the at least one set of axial rods, and the barrier electrode is located between the entrance aperture and the exit electrode and separates the ion guide into the first cell before the barrier electrode and the second cell after the barrier electrode;
• and
• during a cooling time period of the each time cycle and before the AC time period, applying a high DC voltage to the barrier electrode to trap and cool ions in the second cell and allow ions to continue to be received into the first cell without being affected by the ramped AC voltage using the control module.