Related Experiment Video
Updated: May 28, 2026

18F-Labeling of Radiotracers Functionalized with a Silicon Fluoride Acceptor (SiFA) for Positron Emission Tomography
Published on: January 11, 2020
Cryptate mediated nucleophilic 18F-fluorination without azeotropic drying
S H Wessmann1, G Henriksen, H-J Wester
1Chair of Pharmaceutical Radiochemistry, Technische Universität München, Munich, Germany.
Unlabelled:
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.
Conclusion:
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.
Related Concept Videos
Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene
Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic SN1
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo, or cyano...
Preparation of 1° Amines: Hofmann and Curtius Rearrangement Mechanism
Preparation of 1° Amines: Hofmann and Curtius Rearrangement Overview
Nucleophilic Aromatic Substitution: Elimination–Addition
![Microwave-assisted One-pot Synthesis of N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB)](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F2755.jpg&w=3840&q=50)
![Radiosynthesis of 1-(2-[18F]Fluoroethyl)-L-Tryptophan using a One-pot, Two-step Protocol](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F63025.jpg&w=3840&q=50)