Variables: pH Keywords: high resolution mass spectrometry Substances: 4-Formylaminoantipyrin (4-FAA) (WSJBSKRPKADYRQ-UHFFFAOYSA-N) 5-Fluoro Cytosine (XRECTZIEBJDKEO-UHFFFAOYSA-N) Acetochlor-OXA (OTKTUNJJKYTOFF-UHFFFAOYSA-N)