A device for sample analysis, the device comprising: an electrically insulating support; a first electrode disposed at an outer edge of the support, the first electrode forming a first circle; a second electrode in a collection reservoir (4,10); wherein the second electrode is disposed at or connected with the center of the first circle; characterised by a first electrolyte disposed on the support within the first circle, the first electrolyte disposed closer to the first electrode than the second electrode; a second electrolyte disposed on the support within the first circle, the second electrolyte disposed closer to the second electrode than the first electrode, wherein: the second electrolyte comprises a first ion with a higher mobility than a second ion in the first electrolyte; the second electrolyte is surrounded by the first electrolyte, and the first electrolyte and the second electrolyte are prevented from mixing as a result of: the second electrolyte being stabilized by a gel or viscous additive, hydrodynamic separation, or the first electrolyte and the second electrolyte having thickness less than 100 μm; and a high voltage power supply which is configured to deliver a voltage difference between the first electrode and the second electrode. an electrically insulating support; a first electrode disposed at an outer edge of the support, the first electrode forming a first circle; a second electrode in a collection reservoir (4,10); wherein the second electrode is disposed at or connected with the center of the first circle; characterised by a first electrolyte disposed on the support within the first circle, the first electrolyte disposed closer to the first electrode than the second electrode; a second electrolyte disposed on the support within the first circle, the second electrolyte disposed closer to the second electrode than the first electrode, wherein: the second electrolyte comprises a first ion with a higher mobility than a second ion in the first electrolyte; the second electrolyte is surrounded by the first electrolyte, and the first electrolyte and the second electrolyte are prevented from mixing as a result of: the second electrolyte being stabilized by a gel or viscous additive, hydrodynamic separation, or the first electrolyte and the second electrolyte having thickness less than 100 μm; and a high voltage power supply which is configured to deliver a voltage difference between the first electrode and the second electrode. the second electrolyte comprises a first ion with a higher mobility than a second ion in the first electrolyte; the second electrolyte is surrounded by the first electrolyte, and the first electrolyte and the second electrolyte are prevented from mixing as a result of: the second electrolyte being stabilized by a gel or viscous additive, hydrodynamic separation, or the first electrolyte and the second electrolyte having thickness less than 100 μm; and the second electrolyte being stabilized by a gel or viscous additive, hydrodynamic separation, or the first electrolyte and the second electrolyte having thickness less than 100 μm; and a high voltage power supply which is configured to deliver a voltage difference between the first electrode and the second electrode.