The zirconium silicotungstate (ZrSiW) was studied as an effective sorbent material to be used in the .sup.113Sn/.sup.113mIn generator. The results elucidated that the distribution coefficient of .sup.113Sn (3700 mL/g) is greater than .sup.113mIn (275 mL/g) from 0.1 M HCl acid solution to the ZrSiW material. The maximum sorption capacity of Sn (IV) was found to be 33 mg per gram ZrSiW (~ 0.3 mmol/g). The elution yield of .sup.113mIn was found to be > 78 ± 6.4% with an acceptable purity of radionuclidic and radiochemical (greater than or equal to 99.99 and 96.8%, respectively). The rigorous separation of .sup.113mIn from the .sup.125Sb was carried out due to its long half-life (2.758 years) and beta emission that causes tissue damage. Zr, W and Si levels are below the permitted limit in the .sup.113mIn eluate.