Results are reported for a comparative photodegradation study of
atrazine and
desethylatrazine in water using TiO2/H2O2, FeCl3/H2O2, and photolysis. Deionized water and ground water spiked with
atrazine or
desethylatrazine at 36 micrograms/L were irradiated by using a
xenon arc lamp and/or sunlight. After irradiation, the water samples containing the spiked pesticides were preconcentrated by using C18 solid-phase extraction disks and analyzed by gas chromatography with
nitrogen-
phosphorus and mass spectrometric detection. A relative percentage of 7%
desethylatrazine was detected in samples removed after 20 and 4 min of sensitized photodegradation with TiO2 and Fe3+, respectively.
Atrazine and
desethylatrazine did not degrade when solar irradiation (in winter) and deionized water were used.
Atrazine degraded faster than
desethylatrazine when a
xenon arc lamp or sunlight plus FeCl3 was used, with half-lives varying from 5 to 11 min and from 19 to 26 min, respectively. In other photodegradation experiments, the degradation of
atrazine was slightly higher than that of
desethylatrazine. This study shows that
desethylatrazine has slightly higher stability than
atrazine in environmental water samples; this stability accounts for the frequent detection of
desethylatrazine together with
atrazine in natural waters.