A cartridge, in particular a disposable cartridge, for use in an electrowetting sample processing system. The cartridge contains an internal gap with at least one hydrophobic surface for enabling an electrowetting induced movement of a microfluidic droplet that has magnetic beads and further has a bead accumulation zone, into which the microfluidic droplet is transferable by electrowetting force and the magnetic beads are exposable to a magnetic force of a bead manipulation magnet. The internal gap has a bead extraction opening adjacent to the bead accumulation zone. The bead extraction opening provides a passage from the gap to an exterior space of the cartridge and is configured to removably receive the bead manipulation magnet for enabling an extraction of the magnetic beads from the microfluidic droplet by a removal of the bead manipulation magnet.