Potential of RadioHPLC for the Purification of [18F]anle138b, a Candidate Radiotracer for PET Diagnostics of Parkinson’s Disease

High radiochemical purity (RCP) is a crucial requirement to radiopharmaceuticals for positron emission tomography (PET). Semipreparative reversed-phase HPLC with UV and radioactivity detection is an efficient method for purifying radiopharmaceuticals. In separation of highly lipophilic molecules, most of the product remains on the chromatographic column owing to nonspecific sorption. We encountered this problem recently when developing a procedure for purifying [18F]anle138b, a candidate radiotracer for Parkinson’s disease diagnostics. In this study, we tested standard С18 columns, Supelco Ascentis RP-AMIDE, ACE 5 C18, and Macherey-Nagel Nucleosil, in the step gradient mode; however, the required RCP (>95%) was not reached. On the contrary, after the purification on a small monolithic Chromolith SemiPrep RP-18e column in the smooth gradient mode, RCP exceeded 98%. The procedure developed allows preparation of radiopharmaceuticals with the activity sufficient for preclinical studies.