Keywords: high resolution mass spectrometry Substances: Acetazolamide (BZKPWHYZMXOIDC-UHFFFAOYSA-N) 5-Fluoro Cytosine (XRECTZIEBJDKEO-UHFFFAOYSA-N) 1-3-Dimethyl-2-imidazolidinon (CYSGHNMQYZDMIA-UHFFFAOYSA-N) 5-Hydroxy Diclofenac (VNQURRWYKFZKJZ-UHFFFAOYSA-N)