Comparative degradation kinetics of chlorpyrifos in water by photocatalysis with fecl3, tio2 and photolysis using solid‐phase disk extraction followed by gas chromatographic techniques

Abstract

A comparative degradation study of chlorpyrifos spiked at 29–95 μg/L in water ‐using photocatalysis with FeCl3, TiO2 and photolysis using a xenon arc photoreactor and natural sunlight was performed. After irradiation the water samples were preconcentrated using solid‐phase disk extraction with C18 and analyzed by gas chromatography‐electron capture, gas chromatography‐mass spectrometry and liquid chromatography‐mass spectrometry (GC‐ECD, GC‐MS and LC‐MS), respectively. Three photoproducts were identified corresponding to 3,5,6‐trichloro 2‐pyridinol (TCP), O‐ethyl‐O‐(3,5,6‐trichloro‐2‐pyridyl) phosphorothioate and O,O‐diethyl‐O‐(3,5,6‐trichloro‐2‐pyridinyl) phosphate. Chlorpyrifos showed high stability in water when was exposed to natural sunlight irradiation for a period of 30 days. When using photocatalysis with FeCl3 or TiO2 the degradation was very fast with half lives varying from 15–27 minutes. The degradation kinetics followed a first order reaction and the coefficient of variation, for n = 3, varied from 1–3%.