A plurality of planar electrodes (5) in a microchannel (4) is used for separation, lysis and PCR in a chip (10). Cells from a sample are brought to the electrodes (5). Depending on sample properties, phase pattern, frequency and voltage of the electrodes and flow velocity are chosen to trap target cells (16) using DEP, whereas the majority of unwanted cells (17) flushes through. After separation the target cell (16) are lysed while still trapped. Lysis is carried out by applying RF pulses and/or thermally so as to change the dielectric properties of the trapped cells. After lysis, the target cells (16) are amplified within the microchannel (4), so as to obtain separation, lysis and PCR on same chip (1).