Application of C18 disks followed by gas chromatography techniques to degradation kinetics, stability and monitoring of endosulfan in water

Abstract

A comparative degradation study of endosulfan spiked at 35 μg/l in water using photocatalysis with (FeCl3/H2O2)/(TiO2/H2O2) and photolysis using either a xenon arc lamp and/or sunlight was performed. After irradiation the water samples were preconcentrated using C18 solid-phase disk extraction and analysis by gas chromatography–electron capture and mass spectrometric detection. Endosulfan sulphate was found in the photodegradation studies. Endosulfan showed high stability in water when it was exposed to sunlight and xenon arc lamp, but by means of photocatalysis with FeCl3/H2O2, TiO2/H2O2, the degradation was very fast with half lives varying from 59–98 min. The degradation kinetics followed a first order reaction and the R.S.D. of rate constants, for n=3, varied from 4–17%. The stability of endosulfan on C18 Empore disks has been determined at 20°C, 4°C and −20°C for periods up to 3 months. Endosulfan was not degraded on C18 Empore disks. Ground water samples from south of Spain (Almeria) were monitored during 1 year. The compounds α-, β- and endosulfan sulphate were detected at concentration values varying from 0.5–540 ng/l.