Effect of experimental conditions on the in vitro stability of Tc-99m(Sn)-pyrophosphate
The in vitro stability of Tc-99m(Sn)-PyP as a function of experimental conditions of the preparation of the kit and time elapsed after labeling has been tested. The preparation was protected by using nitrogen-purged reactant solutions and kit vials and by ascorbic acid. The samples under nitrogen are stable for 6 h when the content of Tc-99m-pertechnetate raises to 5%. The best stability was achieved by addition of 5 mu g of ascorbic acid per ml of the kit (content of Tc-99m-pertechnetate about 0.5%). To accelerate the decomposition, exogenous hydrogen peroxide was used. In this case it was found that the presence of 10 mu g of ascorbic acid inhibits the effect both of oxygen and peroxide (6 mu g H2O2/ml of the kit). Radiochemically purity of 99mTc(Sn)-PyP remains practically unchanged for 6 h (content of Tc-99m-pertechnetate about 0.5%).