NEW TC-99M GENERATOR TECHNOLOGIES UTILIZING POLYETHYLENE GLYCOL-BASEDAQUEOUS BIPHASIC SYSTEMS

Two new schemes for TcO4-/MoO42- separations from OH- and MoO42- media using polyethylene glycol (PEG)-based aqueous biphasic systems (ABS) have been developed. The two most important salt solutions in current Tc-99m-generator technologies, OH- and MoO42-, also salt out PEG to fo rm ABS. In liquid/liquid PEG-ABS, pertechnetate can be separated from molybdate with separation factors as high as 10,000. Stripping is acco mplished by reduction of the TcO4- and back extraction into a salt sol ution. The strip solution can be the salt of an imaging agent (e.g., N a(4)HEDPA) and thus may, under the appropriate conditions, be injected directly into the human body. (TcO4-)-Tc-99m can also be concentrated from a dilute load solution of (MoO42-)-Mo-99 in NaOH using an aqueou s biphasic extraction chromatographic technique (ABEC). A rinse with K 2CO3 assures that all (MoO42-)-Mo-99 is removed from the column, and t his is confirmed by a rapid drop in Mo-99 activity by the fourth free column volume (fcv) of rinse. The (TcO4-)-Tc-99m is then eluted with w ater. This chromatographic separation affords 94% of the (TcO4-)-Tc-99 m activity in 5 fcv, with the gamma spectrum showing less than 2 x 10( -4) of the original Mo-99 activity.