A rapid quantitative method for the preparation of 123I-iodo-hippuric acid

The labelling of o-iodo-hippuric acid (hippuran) with 123I by several methods was investigated with a view to producing a simple one-step kit preparation. The requirements for the final product are high labelling efficiency and high radiochemical purity. A method which incorporates CuSO4 . 5H2O as a catalyst was found which gave promising preliminary results. Such variables as pH, mass of CuSO4 . 5H2O, volume of 0.02 N NaOH containing the 123I, reaction temperature and time were investigated in detail and optimum values obtained. The results have led to the production of a kit which can be stored for up to 3 months in liquid form and up to 9 months if freeze-dried. The kit has been used in several thousand patients and has yielded consistently good clinical results.