The present invention provides a method for the synthesis of 18F-labelled biomolecules, which is amenable to automation. The present invention also provides a cassette for automating the method of the invention. The method of the present invention provides numerous advantages over the prior art methods. One less purification step is required as compared with known methods. Also, one less reagent is required as a particular reagent is employed in two different steps. The chemistry process is thereby simplified, the cost of goods is reduced and the burden of validation and documentation of reagents required for GMP clinical production is minimized.