Deterioration of stannous ion in radiopharmaceutical kits during storage

The deterioration of stannous ion (Sn++) in inhouse-prepared and commercial radiopharmaceutical kits was studied. Sn++ content of three types of nonlyophilized, deoxygenated, aqueous inhouse-prepared kits [diethylenetriamine pentaacetic acid (DTPA), pyrophosphate and glucoheptonate] and of three commercially prepared kits (two lyophilized pyrophosphate kits and one diphosphonate in sealed glass ampul kit) was measured by differential pulse polarography. Inhouse-prepared kits were assayed initially and after storage for 6, 12, 24 and 48 days at 24, 5 and -18 C. Commercial kits were assayed initially and after storage for 12, 24 and 48 days at 5 and 24 C. Of the inhouse-prepared kits, Sn++ stability when stored for 48 days at 5 and 24 C. Freezer storage should be used, when possible, to insure maximum stability of Sn++ in inhouse-prepared, nonlyophilized ratiopharmaceutical kits. The commercial procedures of lyophilization and of sealing the reagent in a sealed glass ampul prolong Sn++ stability.