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 separation 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⁻; SO₄²⁻; F⁻. Results sucessfully achieved included the simultaneous separation of three anions and three cations.