[en] Radiochemists/radiopharmacists, involved in the preparation of radiopharmaceuticals are regularly confronted with the requirement of continuous high quality productions in their day-to-day business. One of these requirements is high specific or molar activity of the radiotracer in order to avoid e.g. receptor saturation and pharmacological or even toxic effects of the applied tracer for positron emission tomography. In the case of ¹¹C-labeled radiotracers, the reasons for low molar activity are manifold and often the search for potential ¹²C-contaminations is time-consuming.