Photolysis of picloram in dilute aqueous solution

The photolysis of [2,6-14C]pyridine-labeled picloram (4-amino-3,5,6-trichloro-2-pyridine carboxylic acid) was studied at 25°C in sterile, buffered water at pH 7 and in a natural water sample taken from a forest ecosystem. The first-order half-life for picloram photodegradation was the same in both systems, averaging 2.6 d at 25°C for a 40°N latitude location, midsummer time frame. The photolytic decay of picloram in solution produced two major photoproducts. Thermospray liquid chromatography-mass spectrometry (TSP/LC/MS) and gas chromatography/mass spectrometry (GC/MS) in the electron impact and chemical ionization mode were used to elucidate the structures of the photolysis products. The two major 14C-labeled photoproducts were conclusively identified through comparison with analytical standards as oxamic acid (C2H3O4N) and 3-oxo-β-alanine (C3H5O4N).