A simple and efficient method to remove free radioiodide from *I-radiopharmaceuticals.

Removal of free radioiodide from *I-radiopharmaceuticals was easily performed by using a pure metallic silver membrane, placed in a screwable holder. Well-known radiopharmaceuticals such as 3-iodobenzylguanidine, Hippuran, iomazenil and fatty acids were treated successfully, and gave reproducible results. Only a trace of free radioiodide (< or = 1%) was left after passing the silver membrane, while rest activity due to retention of the radiopharmaceutical on the membrane was negligible (2%-5%). This simple and reliable method offers the possibility of application as a last purification step in routine productions, in research or in a nuclear medicine department's pharmacy.