A method for the determination of free 131-I in radio-iodinated lipids.

Experiments are described showing that an anion exchange resin may be used as a simple means of determining the amount of free radio-activity in emulsions of triolein and oleic acid labelled with (131)I in the form of (131)ICl. In the case of radio-iodinated triolein no special modifications are necessary. With radio-iodinated oleic acid, the working solution is made up with an excess of unlabelled oleic acid emulsion to prevent uptake of bound radio-activity by the resin. Recovery experiments show the method to be approximately 90% efficient, which is adequate when the radio-lipids are to be used for clinical purposes.