Method for stabilizing radiolabeled organic compounds by adding a separate stabilizing compound

A method of stabilizing a solution of an organic compound labeled with a .beta.-emitting radionuclide against radiolytic degradation during storage and shipment which comprises adding to said solution a separate, stabilizing effective amount of a non-radiolabeled stabilizing compound which does not bind to said labeled organic compound, said stabilizing compound being selected from the group consisting of (i) heteroaryls having at least one nitrogen atom, said heteroaryl being substituted with at least one sulfur-containing moiety selected from the group consisting of thiol and thiocarbonyl provided that the nitrogen atoms are not adjacent to one another;

• (ii) aryls being substituted with at least one nitrogen-containing moiety selected from the group consisting of amino and isothiocyanate and with at least one sulfur-containing moiety selected from the group consisting of sulfonamide, sulfonate, and thiol;
• and (iii) alkylamines having at least one to four carbon atoms, said alkylamine being substituted with at least one sulfur-containing moiety selected from the group consisting of thioacid and thiocarbonyl provided that when the sulfur-containing moiety is a thioacid then the aminoalkyl contains only one nitrogen atom.