Keywords: high resolution mass spectrometry Substances: 5-Fluoro Cytosine (XRECTZIEBJDKEO-UHFFFAOYSA-N) 4-Dimethylaminoantipyrin (Aminopyrin) (RMMXTBMQSGEXHJ-UHFFFAOYSA-N) 6-benzyladenine (NWBJYWHLCVSVIJ-UHFFFAOYSA-N) 1-Methyl-Benzotriazole (HXQHRUJXQJEGER-UHFFFAOYSA-N) 4-Hydroxy-1-(2-hydroxyethyl)-2-2-6-6-tetramethylpiperidine (STEYNUVPFMIUOY-UHFFFAOYSA-N)