Abstract: The combined capillary electrophoresis electrospray mass spectrometry apparatus has a circuit to handle excess current allows separations under a wide range of electrophoretic conditions. The apparatus includes an electrospray with an emitter and an electrospray interface connected with a separation capillary configured to transport a sample with an injection end and a distal end. The injection end of the separation capillary is inserted into a reservoir containing a background electrolyte and the distal end is threaded within the electrospray interface and sized and shaped to mate with the electrospray interface. A power supply is electrically connected to the injection end and an amplifier at least one first diode positioned between the amplifier and the distal end allows current to flow to the distal end only. A second diode positioned between the distal end and a ground configured to allow current flow to the ground.