Detection of additional impurities in the UV-chromatogram of l-[S-methyl-11C]methionine
Samples of l-[S-methyl-11C]methionine prepared by on-column [11C]methylation on a C18 cartridge were analyzed by HPLC under different conditions in order to explain some anomalies observed in the UV-chromatograms. By so doing, two new unlabelled impurities were found and identified as iodide and homocystine. Their amounts are still compatible with the safe human use of the radiotracer solution. Nevertheless, if needed, iodide can be totally removed by elution through an anion-exchange resin, while homocystine can be reduced by either decreasing the amount of precursor used in the synthesis or preventing its air oxidation.
KeywordsMethionine Carbon-11 HPLC analysis Homocystine Iodide
This work was supported by the Project 5‰ “Development of Radiopharmaceuticals”, the AIRC Project “Molecular and Cellular Imaging of Cancer” and the Project PIO INT Ministero Lavoro.
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