Loss of lipid to plastic tubing

14C-labeled oleic acid and (3)H-labeled monoether in a bile salt solution were perfused through three types of plastic tubing. Large proportions of lipid were lost to the walls of silicone rubber and polyvinyl chloride tubes. The major portion of the lipid lost was recoverable only when chloroform-methanol was perfused through the tubings. On the other hand, very little lipid was lost to the wall of polyethylene tubing. Polyethylene tubing should therefore be used in perfusion studies involving lipid-soluble compounds.