Substances: 5-Fluoro Cytosine (XRECTZIEBJDKEO-UHFFFAOYSA-N) 4-Hydroxy Diclofenac (KGVXVPRLBMWZLG-UHFFFAOYSA-N) 4-Methyl-Benzotriazole (CMGDVUCDZOBDNL-UHFFFAOYSA-N) Keywords: high resolution mass spectrometry MetFrag monitoring