Automated injection of a radioactive sample for preparative HPLC with feedback control

The injection of a radioactive reaction mixture into a preparative HPLC column has been automated with computer control for rapid purification of routinely prepared positron emitting radiopharmaceuticals. Using pneumatic valves, a motor-driven pump and a liquid level sensor, two intelligent injection methods for the automation were compared with regard to efficient and rapid sample loading into a 2 mL loop of the 6-way valve. One, a precise but rather slow method, was demonstrated to be suitable for purification of ¹⁸F-radiopharmaceuticals, while the other, due to its rapid operation, was more suitable for ¹¹C-radiopharmaceuticals. A sample volume of approx 0.5 mL can be injected onto a preparative HPLC column in over 90% efficiency with the present automated system.