a method and apparatus are provided for clearing toxic substances from biological fluids by using at least one microporous diaphragm whose pores are filled with a liquid , which is immiscible with the biological fluid , a washing fluid flows past one face of the diaphragm while the biological fluid flows past the opposite face of the diaphragm . the microporous diaphragm is made of a hydrophobic polymer and the immiscible liquid is a highly refined mineral oil , a highly hydrogenated plant oil , a highly hydrogenated animal oil or , a dimethylated silicone .