Solid phase extraction method

A method to obtain a radiofluorinated compound of Formula I:

• wherein:
• R1 is hydrogen, halo or C1-3 alkoxy;
• R2 and R3 are independently methyl, ethyl or benzyl, or together with the nitrogen to which they are attached form a pyrrolidinyl, piperidinyl, azepanyl, or morpholinyl ring;
• Y1 is CH2, CH2—CH2, CH(CH3)—CH2, or CH2—CH2—CH2;
• and;
• n is 1, 2 or 3;
• wherein said method comprises:
• (i) providing a precursor compound of Formula Ia:
• wherein R1a-3a, Y1a and m are as defined for and are each the same as R1-3, Y1 and n of Formula I, respectively, and LG is a sulfonate leaving group;
• (ii) reacting said precursor compound of Formula Ia with a suitable source of [18F]-fluoride;
• (iii) purifying the reaction mixture obtained in step (ii), wherein said purifying step comprises:
• (a) providing one or more solid-phase extraction (SPE) cartridges wherein the sorbent comprises particles having a diameter between 10-120 μm and bonded hydrocarbons;
• (b) conditioning said one or more SPE cartridges;
• (c) loading the reaction mixture onto said one or more conditioned SPE cartridges;
• (d) washing said one or more SPE cartridges onto which said mixture is loaded using a first solvent system comprising a ratio of water:water-miscible organic solvent in the range 100:0-0:100;
• and,
• (e) eluting said one or more SPE cartridges following said washing step using a second solvent system comprising a ratio of water:water-miscible organic solvent in the range 70:30-0:100;
• with the proviso that in said purifying step HPLC is specifically excluded.