The invention relates to methods and apparatus for purifying a radiolabelled compound. The method comprises (i) passing a crude reaction mixture comprising the desired radiolabelled compound and one or more contaminants in a solvent through a narrow bore vessel at elevated temperature such that the organic solvent and either the radiolabelled compound or one or more contaminants is vaporised forming a vaporised component, and (ii) collecting the resulting vaporised component by condensing into a collection vessel.
