Aim: The reason of unreproducible data under diagnosis and therapy with radioiodine should be elucidated.
Methods: The iodine content of the capsules was tested by a colorimetric method and by activation analysis. Radiochemical purity was determined by HPLC and by electrophoresis. Solubility of the capsules was investigated under different conditions.
Results: The iodine content of the capsules varied between 0.8 and appr. 100 micrograms/capsule. The radiochemical purity of the capsule iodine varied between 75% and 99.5% (main contamination: iodate). The solubility of the capsules differed.
Conclusion: Additional non-radioactive iodine in the therapy capsules could be one reason of the reduced radioiodine-uptake under therapy.