Keywords: high resolution mass spectrometry Substances: 5-Fluoro Cytosine (XRECTZIEBJDKEO-UHFFFAOYSA-N) 3-Phenoxybenzoeacid (NXTDJHZGHOFSQG-UHFFFAOYSA-N) 4-5-Dichloro-2-n-octyl-isothiazol-3(2H)-on (DCOIT) (PORQOHRXAJJKGK-UHFFFAOYSA-N) Acetochlor (VTNQPKFIQCLBDU-UHFFFAOYSA-N)