18F-labeled lower fluoroalkanes; Reactor-produced gaseous physiological tracers

Abstract

Rapid high-yield syntheses of the four gaseous monofluoroalkanes, CH3F, C2H5F, n-C3H7F and i-C3H7F, labeled with 18F are described. The method involves silver (I) oxide catalyzed nucleophilic substitution of 18F- for iodide in the respective iodoalkanes, using acetonitrile as solvent at 120°C. The 18F- was made in a nuclear reactor by irradiation of Li2CO3, which was subsequently decomposed with H+ form ion exchange resin. The resulting aqueous 18F- was rotary-evaporated to dryness after addition of tetraethylammonium hydroxide. Ostwald solubility coefficients of the gases were determined radiometrically at 37°C in water, 0.9% saline, plasma, blood and paraffin oil. The aqueous solubilities are all near unity, while the values for oil rise from 1 to 12 in the series CH3F