Rapid and sensitive measurement of PET radioligands in plasma by fast liquid chromatography/radiometric detection.

A fast and sensitive liquid chromatographic (fast-LC) method with radiometric detection was developed and validated to analyze positron emission tomography (PET) radioligands in plasma during PET studies. The plasma samples were deproteinized with acetonitrile and the extracts were injected into the fast-LC system coupled to an on-line radioactivity detector. Under the optimum conditions, complete separation of target PET radioligands from their radioactive metabolites was achieved within the short run time of only 3.5-min. The limits of detection were 1.0-1.2 Becquerel (Bq) for (11)C and (18)F-labeled compounds. This method can successfully be applied to study the metabolism of a wide variety of PET radioligands in human and monkey plasma with higher numbers of samples to be analyzed compared to the traditional LC method.