Keywords: high resolution mass spectrometry Substances: 5-Fluoro Cytosine (XRECTZIEBJDKEO-UHFFFAOYSA-N) 4-Dimethylaminoantipyrin (Aminopyrin) (RMMXTBMQSGEXHJ-UHFFFAOYSA-N) Adenosine (OIRDTQYFTABQOQ-UHFFFAOYSA-N) Acetochlor (VTNQPKFIQCLBDU-UHFFFAOYSA-N)