In one aspect, an ion filter for use in a mass spectrometer is disclosed, which includes a plurality of rods arranged in a multipole configuration to provide a passageway through which ions can travel, said plurality of rods being configured for application of RF voltages thereto to provide an electromagnetic field within the passageway for providing radial confinement of the ions and further configured for application of a DC voltage thereto. At least two pairs of auxiliary electrodes are interspersed between the plurality of rods and are configured for application of a DC bias voltage with one polarity to one of said pairs and a DC bias voltage with an opposite polarity to the other one of said pairs to provide a DC potential difference between the auxiliary electrodes and the plurality of rods.