Abstract: Methods of preparing 18F targeting biomolecules and small molecules with biological activity for therapeutic and/or diagnostic applications using fluorinated aromatic compounds. A fluorinated conjugated target tracer is synthesized and purified with temperature and solvent conditions that are mild for the tracer molecule. The purified fluorinated-conjugated target tracer is then labeled with 18F using 18F salts within a short reaction time, and with temperature and solvent conditions that are mild for the tracer molecule. The method provides a quick and convenient process that maintains the biological activities of the target molecules. The radio-labeled biomolecules may be used as contrast agents for Positron Emission Tomography (PET).