An ion filter (10) for use in ion mobility spectrometry is described, together with a method for manufacturing the filter. The filter (10) is manufactured by removing portions from a monolithic structure to form a pair of electrodes which remain mechanically connected. The connecting portion (22) provides sufficient electrical impedance between the electrodes to effectively electrically separate the electrodes. The connecting portion may be doped or chemically modified to obtain a desired impedance, or this may be obtained through appropriate selection of physical dimensions.