The invention provides an aqueous acidic formulation suitable for use as in the preparation of a pharmaceutically acceptable fluorocarbon-linked peptide formulation, which aqueous formulation comprises a first fluorocarbon-linked peptide, wherein: the peptide linked to the fluorocarbon is at least 20 amino acid residues long, comprises at least 50% hydrophobic amino acid residues and has an isoelectric point greater than or equal to 7; and the fluorocarbon-linked peptide is present in micelles.