Keywords: high resolution mass spectrometry Substances: Acemetacin (FSQKKOOTNAMONP-UHFFFAOYSA-N) 4-5-Dichloro-2-n-octyl-isothiazol-3(2H)-on (DCOIT) (PORQOHRXAJJKGK-UHFFFAOYSA-N) 5-Fluoro Cytosine (XRECTZIEBJDKEO-UHFFFAOYSA-N) 1-Methyl-Benzotriazole (HXQHRUJXQJEGER-UHFFFAOYSA-N)