Systems and methods are described for separating components of aqueous mixtures, including aqueous solutions and suspensions. In one implementation, an apparatus flows the aqueous mixture over a hydrophilic surface to form a first region of purified water and a second region of at least one concentrated non-aqueous component. The apparatus can draw off either the purified water or the concentrated non-aqueous components. In one implementation, an array of tubules performs the differential extraction. In another implementation, various hydrophilic and/or hydrophobic surfaces are disposed in multiple differential extractors and some effluents may be recycled to perform complex assaying and separation.