The present disclosure describes a field flow fractionator including (1) a top plate assembly including (a) a first non-corrosive material, and (b) at least three fluid fittings machined (simpler) into the material, (2) a spacer, (3) a membrane, (4) a bottom plate assembly including (a) a second non-corrosive material, (b) a cavity machined into the second non-corrosive material, (c) a frit configured to be placed into the cavity, and (d) at least one bottom plate o-ring configured to seal the bottom plate assembly to the spacer, and (5) where the top plate assembly, the spacer, the membrane, and the bottom assembly define a separation channel. In an embodiment, the at least three fluid fittings including a fitting for an in-flow, a fitting for an out-flow, and a fitting for a cross-flow.