Keywords: high resolution mass spectrometry Substances: 4-Formylaminoantipyrin (4-FAA) (WSJBSKRPKADYRQ-UHFFFAOYSA-N) 5-Fluoro Cytosine (XRECTZIEBJDKEO-UHFFFAOYSA-N) 3-Phenoxybenzoeacid (NXTDJHZGHOFSQG-UHFFFAOYSA-N) 1-[(4-Chlorophenyl)phenylmethyl]piperazine (UZKBSZSTDQSMDR UHFFFAOYSA-N)