Abstract
The practical upper limit of fluorineβ18 specific activity has remained constant for many years among cyclotron facilities internationally. Although there have been isolated reports of very high specific activity and hints concerning the sources of carrier, experiments designed to identify carrier sources have been inconclusive and largely ineffective. This report describes experiments to test the hypothesis that radiolysis of fluorinated components is a source of carrier fluoride. Controlled experiments were performed in which contributions of irradiated fluorinated components to the mass of synthesized [^18^F]fluorobenzaldehyde (FBA) were measured. There was clear correlation between irradiation of Teflon and carrier mass. There was an additive effect of carrier due to different fluoropolymer components. It was concluded that in typical target and radiosynthesis systems it is radiolysis of fluorinated material and not the material itself that generates a large majority of the carrier typically reported. All Teflon and other fluorinated materials in contact with the [^18^F]fluoride solution were removed. With no further efforts to reduce carrier fluoride, FBA produced from a modest irradiation attained a reduction in mass from over 500βnmol to 30βnmol, and an increase in specific activity from 0.1βTBq (3 Ci) to 1.9βTBq (51 Ci) per micromole. Copyright Β© 2009 John Wiley & Sons, Ltd.