Efficient production and purification of 32P radioisotope from sulfur by dry distillation: A practical approach with high radiochemical purity

Abstract

The 32P radioisotope, with a half-life of 14.3 days and an energy level of 1.71 MeV, has diverse applications in medicine and research. Consequently, producing a carrier-free 32P radioisotope characterized by high radiochemical and radionuclide purity is imperative. Two primary methods for generating 32P radioisotopes exist: irradiating phosphorus through the nuclear reaction (n,γ) or irradiating sulfur through the nuclear reaction (n,p). Using sulfur as a target material provides several advantages. Besides the fact that the chemical element produced after irradiation (32P) differs from the irradiated element (32S), it also produces a32P radioisotope with a higher specific activity than using 31P as the target. The production of the radioisotope 32P from sulfur employs the dry distillation method, capitalizing on sulfur's easily sublimated nature. The volatility of sulfur when heated makes it easy to separate the resulting sulfur and radioisotope 32P without the need for additional reagents. This research aims to establish a practical method for producing the 32P radioisotope using the dry distillation technique. The dry distillation method utilizes a quartz ampoule containing a mixture of 32P and 35S radionuclides, a distillation tube wrapped with heating tape, and a condenser to collect the distilled sulfur. Sulfur, serving as the target material, undergoes irradiation in the reactor at the Central Irradiation Position (CIP) through the 32S(n,p)32P nuclear reaction with a fast neutron flux of 5.380 × 1013 n/cm2.sec. Separation is achieved through distillation at a temperature of 440 °C. The residual separation products are then dissolved in a 0.1 N HCl solution. The purification process involves using an AG50 WX8 cation exchange resin column, which is pre-conditioned with 0.1 N HCl. The resulting eluate contains the 32P radioisotope. The radiochemical purity of the 32P radioisotope is analyzed using thin-layer chromatography (TLC). In this analysis, a PEI Cellulose plate serves as the stationary phase, and a KH2PO4 solution acts as the mobile phase. This vacuum-free distillation method successfully separates the 32P radioisotope from sulfur, achieving a separation efficiency of 55.1 ± 9.9% (n = 7). The average activity produced after the purification process is 5.690E+10 Bq. Purifying the 32P radioisotope results in a radiochemical purity of 99.97% at Rf 0.7110, as orthophosphate, the radionuclide purity exceeds 99%.