To lower the eluent volume, the product outlet was connected to a switch valve, external to the main lead castle, where radioactivity could be measured with an external detector (Fig. ). This allowed for remote collection of the most concentrated fraction of eluent (Fig. ) and improved the radioactive concentration more than 3-fold to ~30 MBq/mL (n = 7). A noticeable limitation in the cartridge-based purification was the use of the commercially available Thermo Fisher Hypercarb cartridge (Vs1; Fig. ). [ 18 F]FSPG is passed through the Hypercarb cartridge as the final step of the cartridge purification. The Hypercarb cartridge is not designed for automated synthesis and consequently requires two adaptors to link the cartridge to the FASTlab tubing.