"Mixed" anionic and non-ionic micellar liquid chromatography for high-speed radiometabolite analysis of positron emission tomography radioligands.

A mixed micellar liquid chromatographic (LC) method, the mobile phase consisting of anionic and non-ionic surfactants, has been developed for the high-speed direct radiometabolite analysis of positron emission tomography (PET) radioligands in plasma. The addition of Triton X-100 on an anionic surfactant sodium dodecyl sulphate (SDS) mobile phase improved elution strength and peak efficiency for many PET radioligands. Several radioligands could be easily separated from their radioactive metabolites with short run time of only 4 min using a "pure" (without organic solvent) mixed micellar mobile phase and semi-preparative monolithic C(18)-bonded silica column by simple isocratic elution without any treatment of plasma. Moreover, the use of "hybrid" mixed micellar mobile phase containing anionic, non-ionic surfactants and organic solvent was effective to further enhance peak efficiency and elute highly retained hydrophobic PET radioligands. These characteristics enabled significant shorting the radiometabolite analysis procedure of PET radioligands and simplifying the experimental setup.