For non-carrier-added 18F-labeling of organic compounds, details were studied concerning the previously developed KF-crown ether method. In the modified method, a minute amount of KOH instead of carrier KF is addede for the preparation of the anhydrous 18F from aqueous carrier-free 18F. The following factors were examined in order to determine optimum conditions for the preparation of the anhydrous non-carrier-added 18F and the labeling synthesis with it: effects of the vessel on the evaporation of the 18F-KOH solution andn the amount of added KOH for the conversion of aqueous 18F to anhydrous 18F, the solubilized activity of the 18F obtained by the evaporation in organic solutions containing 18-Crown-6 and the laveling reaction, as examplified by the synthesis of 21-fluoroprogesterone
