Phosphinimines as selective extractants for Tc-99 pertechnetate

The triphenylphosphiniminium cation (Ph3P=NH2+) was evaluated for its selectivity for the pertechnetate anion (99TcO4-) using both solvent extraction and solid phase extraction methods. The solid phase extraction of TcO4- using trimethylsilyl-protected triphenylphosphinimine coated silica gel demonstrated the selectivity of the triphenylphosphiniminium cation for TcO4- over a variety of inorganic (NO3-, Cl-, H2PO4-, HSO4-/SO42-) and organic (fumarate) anions in aqueous solution (> 98% extracted when at pM TcO4- vs. 0.15 M anion). Iodide, lactate, benzoate and acetate were able to compete with pertechnetate (only 11-83% extracted) when present in large excess (0.15 M anion vs. 10-12 M 99mTcO4-), but not when the anion was present in a 10-fold excess. The triphenylphosphiniminium cation was significantly selective for TcO4- over ReO4-, a commonly used non-radioactive analog for 99Tc, when tracer amounts of both competed with the anions iodide, lactate, benzoate and acetate. (orig.)