Figure 3.

Rapid, room temperature (21 °C) ¹⁸F-¹⁹F IEX radiolabeling of 1. a) Kinetic analysis of room-temperature radiolabeling. A 0.5 mg quantity of 1 was dissolved with a SnCl₄/acetonitrile solution containing 0.6 mCi [¹⁸F]-fluoride ion. At different time points, 0.2 μL aliquots of the reaction were drop cast onto silica TLC with 100% methanol as the mobile phase. (Fraction-RCY is reported where 1.0 = 100% conversion). b) Analysis of fraction-RCY as a function of starting [¹⁸F]-fluoride-ion activity. Quantities of 1 (0.5 mg) were dissolved with SnCl₄/acetonitrile solutions containing increasing quantities of [¹⁸F]-fluoride ions. Fraction-RCYs were determined after 30 min. c) Determination of 1 molar activity as a function of 1 quantity. RCYs were measured after 30 min of room temperature radiolabeling with 0.32 mCi of [¹⁸F]-fluoride-ion in SnCl₄-containing anhydrous acetonitrile (200 μL in total volume) and decreasing quantities of 1 (25-1000 μM in concentrations). d) HPLC characterization of 1 radiosynthetic purity, and proof of isotopic exchange. At 20 min, 10%–60% linear acetonitrile/water gradient flow and C18 Reversed Phase HPLC was used to resolve the crude 1. A peak (6.1 min) indicating radiolabeled 1 is observed. An HPLC peak at ~1 min, where free [¹⁸F]-fluoride ion generally appears, is not visible.