Abstract: An electrolyser for separating a mixture of components using isoelectric focusing in a liquid media comprises a series of blocks defining chambers. The chambers are separable by isoelectric membranes of known pH. End chambers are located at each end of the series of chambers. The blocks are clamped together using four tie rods to make the apparatus substantially liquid tight. An electrodes is provided in each end chamber for use in applying an electric field across the series of chambers. One of the tie rods is conducting and carries current from an electrode at one end of the apparatus to the opposite end of the apparatus. A lever operated clamping mechanism is provided for tensioning the tie rods and clamping the chambers together between the end blocks in a liquid tight fashion.