Cationic imidazolium polymer monoliths for efficient solvent exchange, activation and fluorination on a continuous flow system

Abstract

Polystyrene-imidazolium (PS-Im⁺Cl⁻) monolith was synthesized within a flow-through microfluidic chip and Teflon tubing for activating [¹⁸F]fluoride ions. The [¹⁸F]fluoride ions were trapped on the PS-Im⁺ monolith and were subsequently released with various phase-transfer catalysts (PTC) and carbonate or bicarbonate bases in microliter volumes of organic solvents containing 0.5% of water. The activated [¹⁸F]fluoride complex released from the PS-Im⁺ monolith was used to fluorinate various known PET probe precursors with diverse reactivity in a subsequent flow-through microfluidic chip without performing additional azeotropic distillation. The fluorination yields under the optimized condition for the protected [¹⁸F]FDG, protected [¹⁸F]FLT, 4-[¹⁸F]fluoroethylbenzoate, and [¹⁸F]fallypride were 93%, 96%, 77% and 73%, respectively. This method, utilizing the PS-Im⁺ monolith on a flow through microfluidic platform, enables the entire fluorine-18 radiochemistry to be performed on a flow-through microfluidic device within a shorter synthesis time and with fluorination efficiency that is comparable to or higher than conventional means.