To improve the health of patients with end-stage renal disease, there is a clear need for slow, continuous hemodialysis, and the primary barrier to a wearable device is the requirement of a large reservoir of dialysate. We describe an electrokinetic means of producing dialysate from the excess fluid extant in the peripheral blood of patients undergoing therapy. A critical feature of this process is the retention of essential components of blood, especially serum albumin. In progress toward this goal, we demonstrate the separation of charged from neutral species in blood plasma at a branched microchannel junction by ion concentration polarization (ICP). Further, we introduce a method that reduces the opportunity for damage to proteins and prevents electrode biofouling. The present approach results in as high as 99.7% retention of albumin and successful separation of neutral metabolites and excess fluid to be utilized as a precursor to dialysate.