Improving the stability of (11)C–labeled L-methionine with ascorbate

BACKGROUND: Carbon-11 labeled L-methionine ((11)C–MET) is a popular tracer used in the clinic for imaging brain tumors with positron emission tomography. However, the stability of (11)C–MET in its final formulation is not well documented in literature. Recently, we observed fast degradation of HPLC-purified (11)C–MET over time, and systematic investigation was conducted to identify the cause. RESULTS: In this study, we verified the degraded product as (11)C–labeled methionine sulfoxide ((11)C–METSO). To minimize oxidation, ascorbate (100 ppm) was added to the HPLC eluant, and the resulting HPLC-purified (11)C–MET was stable in the final formulation solution without noticeable degradation for up to 1 h after the end of synthesis. CONCLUSIONS: Our data suggest that to minimize degradation, ascorbate can be added to the (11)C–MET formulation solution especially if it is not administered into patients soon after the end of synthesis. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s41181-017-0032-x) contains supplementary material, which is available to authorized users.