Combining high-performance liquid chromatography-positron detection and on-line microdialysis for animal metabolism study of positron emission tomography probes.

Automated ultra-performance liquid chromatography (LC) with a radiometric detection system has been developed to analyze compounds labeled with short-lived positron (beta(+))-emitting radionuclides in microdialysates. This system involves (1) on-line microdialysis sampling to submit dialysates directly into the LC, (2) ultra-performance LC for improving sensitivity, resolution and speed of analysis, and (3) tandem flow-through of beta(+) and electrochemical detectors for real-time monitoring of radioactive and endogenous compounds simultaneously. This system permitted ultrasensitive measurement of radioactive compounds at the lowest detection limit of about 1Bq with a high-temporal resolution of sampling and less operator attention. The developed system was used for the continuous monitoring of L-[beta-(11)C]-3,4-dihydroxyphenylalanine (L-[beta-(11)C]DOPA) metabolites in the rat brain.