Determination of aquatic photodegradation products of selected pesticides by gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry

The photodegradation of the organophosphorus pesticide fenitrothion and the chlorotriazine herbicide propazine has been investigated under different light conditions. The photodegradation of propazine was carried out using a xenon lamp in the suntest apparatus whereas a high-pressure mercury lamp was used for fenitrothion. For propazine, experiments were carried out in distilled water and artificial seawater containing humic acids at 44°c, whereas for fenitrothion a water-methanol (5:1) solution at 20°C was employed. Identification of the sufficiently volatile photodegradation products was achieved by gas chromatography-mass spectrometry (GC-MS) with electron impact (El), whereas for the direct characterization of the hydroxy metabolite of propazine thermospray liquid chromatography-mass spectrometry (LC-MS) is required. The photodegradation pathways of the pesticides in water included dealkylation, deamination, dehalogenation, hydroxylation, isomerization and solvolysis.