Keywords: high resolution mass spectrometry Substances: Acemetacin (FSQKKOOTNAMONP-UHFFFAOYSA-N) 5-Fluoro Cytosine (XRECTZIEBJDKEO-UHFFFAOYSA-N) 3-5-6-Trichloro-2-pyridinol (WCYYAQFQZQEUEN-UHFFFAOYSA-N) Adenosine (OIRDTQYFTABQOQ-UHFFFAOYSA-N)