HPLC method development using a mixed-mode column for following Ga-68-radiolabeling

The aim of our work was to develop a generally applicable liquid chromatographic method for the determination of the residue free Ga-68(3+) content of labeling reaction mixtures, in order to facilitate comparative labeling experiments in the early stages of chelator development. We achieved the retention of free Ga-68(3+) on a mixed mode cation exchanger HPLC column with a gradient program, which allowed the separation from the non-retained complexes. The effects of reaction conditions (time, temperature) and the application of non-coordinating buffers were examined. Furthermore, recovery of free Ga-68(3+) and these complexes were investigated, values of which were 94.9-97.4% and 87.4-99.6%.