The use of a miniaturised planar separation device with integrated conductivity detection for performing bidirectional isotachophoresis (ITP) is described. The chips were produced in poly(methyl methacrylate) (PMMA) using a milling procedure. To enable bidirectional ITP the devices were designed to inject samples into the centre of the section channel and incorporated two integrated on-column conductivity detectors, positioned at opposite ends of this channel. When used with a hydrodynamic sample transport system the devices were used for the analysis of a range of small ions: NH4+; Na+; Mg2+; Ca2+; Li+; NO3-; ClO4-; SO4(2-); F-. Results sucessfully achieved included the simultaneous separation of three anions and three cations.