title: Cryptate mediated nucleophilic 18F-fluorination without azeotropic drying.
abstract: The radiosynthesis of the vast majority of 18F-labeled tracers rely on azeotropic drying of [18F]fluoride and subsequent cryptate mediated introduction of [18F]fluoride by nucleophilic substitution. THE AIM of this study was to develop a method for simplification of this process, based on preparation of reactive [K(+) is a subset of 2.2.2]18F(-) by solvent drying of [18F]fluoride adsorbed onto an anion exchange resin.
  
  
  METHODS
  Aqueous [18F]fluoride (0.5-1 ml) obtained from the 18O(p,n)18F nuclear reaction was trapped on a strong anion-exchange (SAX) cartridge. After washing the cartridge with dry CH3CN, [18F]fluoride was eluted with an anhydrous solution of [K(+) is a subset of 2.2.2]OH(-) in CH3CN and directly used for nucleophilic fluorination reactions.
  
  
  RESULTS
  [18F]Fluoride from target water was quantitatively retained by the SAX cartridge, and water-free [18F]fluoride recovered in an overall yield of 92±5% (n = 10). [18F]Fluoride obtained by this procedure led to radiochemical yields of 70-90% for [18F]FDG, [18F]FET, [18F]FLT, [18F]FAZA and [18F]Fallypride.
  
  
  CONCLUSIONS
  SAX-resin adsorbed [18F]fluoride can be dried with non-aqueous solvents and eluted with [K(+) is a subset of 2.2.2]OH(-) in CH3CN. The reactivity of [K(+) is a subset of 2.2.2]F(-) generated by the new method is comparable to that of [18F]fluoride obtained by azeotropic drying. The described procedure facilitates the automated production of 18F-radiopharmaceuticals in general, and may also simplify the use of microfluidic devices for 18F-radiotracer production.
authors: Chair of Pharmaceutical Radiochemistry, Technische Universität München, Munich, Germany.
authors: S H
authors: SH
authors: Wessmann
authors: G
authors: G
authors: Henriksen
authors: H-J
authors: HJ
authors: Wester
mesh_terms: D043844:Crown Ethers / Q000737:chemistry*; D003890:Desiccation / Q000379:methods; D005462:Fluorine Radioisotopes / Q000737:chemistry* / Q000302:isolation & purification*; D007553:Isotope Labeling / Q000379:methods; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000302:isolation & purification*
chemical_list: D043844:Crown Ethers; D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals