Variables: dissolved_oygen concentration Keywords: high resolution mass spectrometry Substances: 4-Formylaminoantipyrin (4-FAA) (WSJBSKRPKADYRQ-UHFFFAOYSA-N) 1-Naphthylacetic acid (PRPINYUDVPFIRX-UHFFFAOYSA-N) 1-Propanesulfonate (KCXFHTAICRTXLI-UHFFFAOYSA-N)