Planar chromatographic analysis and quantification of short-lived radioactive metabolites from microdialysis fractions

A sensitive radiochromatographic method for the quantitative determination of compounds labelled with short-lived β-emitting radionuclides in microdialysates is described. The method is well suited for microdialysis (MD) samples, which have small volumes and low concentrations of compunds. An 18F-labelled (β+; T1/2 = 109.8 min) radiopharmaceutical, (1R,2S)-4-[18F]fluorometaraminol (FMR), was injected intravenously into rats, and microdialysis fractions were then collected from the blood at 15 min intervals. Fractions were analyzed for FMR and its radioactive metabolites by planar chromatography combined with digital photostimulated luminescence autoradiography. The lowest detectable 18F-radioactivity was 0.24 Bq/application and the limit of quantification was 0.31 Bq/application with 4–16 h exposure. The method was found to be highly sensitive and linear in the range of 0.1 Bq–2 kBq. This method thus allows the quantification of β-emitting radiopharmaceuticals in sequential microdialysis fractions with good time-resolution.