Decomposition of Tc-99m pyrophosphate by peroxides in pertechnetate used in preparation

We describe an investigation of the stability of Tc-99m pyrophosphate (Tc-99m PPi). We hve shown that addition of exogenous hydrogen peroxide to Tc-99m PPi can initiate the oxidation of the complex, giving rise to 95% unbound pertechnetate. The presence of endogenous hydrogen peroxide in the sodium pertechnetate used in the preparation of Tc-99m PPi has been thought to influence its stability. We have prepared it using pertechnetate solutions of different specific activities. After preparation, an alumina column was used to detect free 99mTcO4-. The Tc-99m PPi and Na99mTcO4 solutions were then assayed by iodometric titration for hydrogen peroxide, which was detected in the pertechnetate solutions. The higher the specific activity of the solution used for the tracer preparation, the faster was the production of free pertechnetate.