Keywords: high resolution mass spectrometry Substances: 5-Fluoro Cytosine (XRECTZIEBJDKEO-UHFFFAOYSA-N) 1-(3-Trifluoromethylphenyl)-piperazine (KKIMDKMETPPURN-UHFFFAOYSA-N) 2-Aminobenzimidazole (JWYUFVNJZUSCSM-UHFFFAOYSA-N) 3-5-Diiodo-L-tyrosine (NYPYHUZRZVSYKL-ZETCQYMHSA-N) AMDOPH (IRTZMJWVZQYURE-UHFFFAOYSA-N)