Aqueous carbonic acid: a readily removable electrolyte for the recovery of [18F]fluoride from anion exchange resins.

[18F]Fluoride was recovered from [18O]target water in high yield by trapping it on a microcolumn of an anion exchange resin (20 mg Dowex 1 x 8, 400 mesh) and subsequent elution of the column (in the reverse direction) by aqueous carbonic acid at 52 atm. The carbonic acid was removed from the [18F]fluoride solution by brief heating at 85 C, 1 atm. Thus no extraneous electrolyte was introduced by the extraction process. The resulting bicarbonate form of the resin was immediately capable of trapping further [18F]fluoride, permitting a repetitive remote system for recovery of [18O]water. Chloride was substantially retained on the column permitting separation of [18F]fluoride from the former.