Selective ion mobility filter

An ion mobility filter comprising:

• a tube having an inner wall with a pattern of electrodes along the inner wall, an RF generator that supplies the pattern of electrodes with a two phase RF voltage so that a multipolar RF field forms inside the tube, a network of resistors connected to the pattern of electrodes, at least one DC voltage generator, connected to the network of resistors, for generating axial potential profiles forming a first and a second electric field barrier inside the tube to form two low pass ion mobility filters in the tube, wherein the first DC electric field barrier blocks the passage of ions with a mobility of μ≧μ1 and the second DC electric field barrier blocks the passage of ions with a mobility of μ≧μ2, where μ<μ1 and wherein the maximum field strength up to the second field barrier having a maximum field strength higher than the maximum field strength of the first field barrier, and a gas source that generates a laminar gas flow inside the tube driving ions first against the first electric field barrier and subsequently against the second electric field barrier, wherein the first DC electric field barrier and the second DC electric field barrier are each stationary along an axis parallel to the direction of the flow of the gas.