Development of techniques of production of sulfur-35 and its inorganic compounds

Techniques to produce routinely Curies of carrier-free sulfur-35 from neutron irradiated potassium chloride were developed. Firstly the ratio of sulfur-35 to phosphorus-32 produced respectively by the reactions 35Cl(n,p)35S and 35Cl(n,α)32P was determined. For the post-irradiation process, two processes of anion exchange and cation exchange were studied. The former process was based on the selective elution of carrier-free sulfate after precipitation of the bulk of potassium chloride by ethanol and the latter process on the selective adsorption of carrier-free phosphate on Fe+3-cation exchange resin. A gloved box with various appendant equipments was constructed for routine production and a glass apparatus was installed in it. Sulfur-35 from 1 Ci to 5 Ci has been produced by the cation exchange process several times every year during past few years, and products of high quality have been obtained with yields higher than 90% without any troubles. In the studies on the synthesis of sulfur-35 labeled inorganic compounds, sulfate[35S] was reduced with tin(II)-phosphoric acid to hydrogen sulfide[35S], which was oxidized to elementary sulfur[35S]. Sulfate[35S] of sodium or copper(II) was precipitated from an aqueous solution of sodium or copper(II) chloride containing carrier-free sulfate [35S] by adding carrier of either one of the sulfates and ethanol. Copper(II) sulfate[35S] was pyrolyzed to evolve sulfur[35S] dioxide, which was fixed in a sodium hydroxide solution as sodium sulfite[35S]. This was allowed to react with colloidal sulfur in a boiling solution in the presence of 2-octanol to form thiosulfate[35S] efficiently. By treating target potassium chloride before and after irradiation in an oxygen-free atmosphere, approximately 60% of sulfur-35 was recovered as thiosulfate. Reduction with nascent hydrogen and decomposition with acid of the thiosulfate were studied to prepare elementary sulfur [35S]. (author)