Device for concentrating plasma

A device for concentrating a blood fraction comprising:

• a housing having first and second openings at first and second ends, respectively, and an outlet between said first and second ends, wherein said outlet is adapted to connect to a vacuum source;
• a semi-permeable membrane oriented in said housing to define a concentrate chamber that communicates with the first and second openings and a filtrate chamber that communicates with the outlet, said semi-permeable membrane having a molecular weight cut-off suitable for retaining a desired species within said concentrate chamber;
• first and second manifolds at the first and second ends, respectively, of said housing;
• first and second valves connected to said first and second manifolds, respectively, wherein a first flowpath through each of said valves communicates with the concentrate chamber in a first open position, and said first valve has a second open position wherein the first flowpath is replaced by a second flowpath;
• a fluid delivery system connected to said first valve, wherein the first flowpath through said first valve communicates an interior chamber of said fluid delivery system with the concentrate chamber of said housing;
• and
• a purge fluid delivery system connected to said first valve, wherein-the second flowpath through said first valve communicates with an interior chamber of said purge fluid delivery system and with the concentrate chamber of said housing.