Production, Identification, and Characterization of FLUORINE-18 Labeled Electrophilic Fluorinating Agents from Novel, Low Volume Target Systems

Target bodies made of aluminum, nickel, copper, silver and gold plated copper were investigated using the nuclear reactions, ^{18}O(p,n) ^{18}F (13.5 MeV), ^{20}Ne(d,alpha) ^{18}F (10.7 MeV), and ^{16}O(^3He,p) ^{18}F (26.8 MeV) for electrophilic ^{18}F production. This study also included spectroscopic identification of the chemically reactive and inert fluorinated species recovered from these target systems, evaluation of the ease of recovery of the ^{18}F and examination of the chemical reactivity of the ^{18 }F species. In all conditions examined, spectroscopic analysis verified the major post irradiation fluorinated component as F_2. In the post irradiation oxygen/fluorine mixes, oxygen difluoride (<=q 15%) and fluorine nitrate (<3%) were found as minor components. Spectroscopic analysis included ^{19}F NMR of fluorinated species, ^{17}O NMR of the OF_2, ^{15} N NMR of the FONO_2, and mass spectroscopic (using a residual gas analyzer) verification of the F_2, OF_2 and CF_4. Interestingly, the ratio of F_2/OF _2 was invariant to variables investigated such as target body and fluence, but measurably affected by the irradiation protocol and particle beam, with less OF_2 relative to F_2 observed in the single-step ^3He irradiation and the two-step proton irradiation. The use of an electroformed nickel target body showed superior recovery of the ^{18 }F with all three nuclear reactions, averaging 89% of the theoretical thick target saturation yields for the reactions of ^{20}Ne(d, alpha)^{18}F and ^{16}O(^3He,p)^{18 }F. This is probably due to more efficient heat conduction inherent to its thin wall design. Overall, the target body performance hierarchy was little affected by the nuclear reaction used. For the first time, aluminum has been demonstrated to be a useful target body material for gas phase ^{18}F production. (^{18}F] F_2>=nerated in the oxygen environment did not hinder the formation of acetyl hypofluorite. However, (^{18}F] F _2 obtained from an oxygen environment in the gold plated copper or nickel target body was unusable in the fluorodemercuration synthesis of 6-(^ {18}F) fluoro-L-dopa, while the fluorodestannylation method resulted in superior yields regardless of target body.