Identification and quantitation of gaseous compounds of fluorine generated in [ 18F]F 2 target systems

Abstract

The first direct evidence for the chemical identity of the electrophilic fluorinating agents generated in 20Ne(d,α) 18F (single-step), 18O(p,n) 18F (single-step and two-step) and 16O( 3He 2+,p) 18F (single-step) gas target systems, utilizing aluminum, silver, copper, nickel and gold plated copper target bodies, has been established with multinuclear NMR and mass spectral techniques. The major components of the reactive fraction from these targets were also quantitated using 19F NMR. Fluorine-19 NMR data of the reactive fraction of all proton and 3He 2+ irradiated oxygen gas target systems showed the presence of oxygen difluoride in various proportions. Samples from the single-step method contained up to 20% OF 2 while those from the two-step process had 0–5%. Fluorine nitrate (FONO 2) was observed only as a minor component (0–3%) in the reactive fraction. The presence of OF 2 and FONO 2 was further confirmed by 17O and 15N NMR, respectively, using [ 17O]O 2 and [ 15N]N 2 spiked oxygen gas targets. The NMR results were supported by mass spectral data collected with a residual gas analyzer (RGA). Both 19F NMR and mass spectroscopy showed CF 4 as the only major inert component in the single-step oxygen target products. As expected, the 19F NMR and mass spectral data showed that the reactive fraction of the neon gas target constituted only F 2 and the inert fraction comprised of CF 4 and NF 3.