Tetrabutylammonium is a phase‐transfer agent commonly used in PET radiochemistry. Its toxicity makes its quantification mandatory. However, the official HPLC method for tetrabutylammonium analysis reported in the European Pharmacopoeia (Ph. Eur.) apparently fails to achieve the described separation in most new generation reverse‐phase columns. The study highlights the differences in separation achievable by varying some of the chromatographic conditions, such as temperature, eluent composition and ion‐pairing agent concentration. In the end, variations to the method within the limits allowed by the Ph. Eur. were not sufficient to overcome the problem, thus forcing to a more radical change of the organic component of the mobile phase.
By adapting previously reported reaction conditions, [18F]FMISO was synthesized using a TracerLab FX‐FDG module in 31 min from no carrier added [18F]fluoride in 56% radiochemical yield. A novel and simple purification setup based on disposable cartridges was developed allowing the radiopharmaceutical to be obtained in high radiochemical purity (>99.5%) and with chemical impurities far below the Ph.Eur.'s thresholds. Moreover, the study pinpointed some shortcomings of the high‐performance liquid chromatography (HPLC) method reported in the dedicated Ph.Eur's monograph.
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