The present invention relates to a method and a device for small scale reactions, such as sample preparation of a desired substance in a sample. In the method using the device samples mixed with functionalized magnetic particles are magnetically transferred between different working stations on the device. The method uses a hydrophobic surface, such as a Petri dish, provided with hydrophilic spots of, for example, agarose beads located on said hydrophobic surface and provided with buffers, reactants or ligands.