Shelf-life of Tc-99m(Sn)-pyrophosphate
The effect of the preparation conditions on the in vitro stability of Tc-99m(Sn)-pyrophosphate kit solution has been examined. To extend the shelf-life of the preparation, different methods of protection were tested. Nitrogen purging stabilizes the kit for at least 6 h after labeling when the content of (99)mTc-pertechnetate raises to about 5%. However, this method is ineffective in the presence of hydrogen peroxide. The protecting ability of two chemicals was also determined. Gentisic acid gave good results. In the presence of 50 mu g of gentisic acid per mi of the kit the content of pertechnetate was 1-2% throughout the examined time interval. To eliminate the influence of hydrogen peroxide (6 mu g per ml of the kit) about 100 mu g of gentisic acid is needed. N,N-diphenyl-p-phenylenediamine (DPPD) performs some protecting effect only when used in the samples protected by nitrogen purging. However its protecting ability is lower that in the case of gentisic acid.