Application of solid-phase microextraction (SPME) for photocatalytic studies of fenitrothion and methyl parathion in aqueous TiO2 suspensions

The photocatalytic degradation of the organophosphorus insecticides fenitrothion and methyl parathion has been studied in aqueous titanium dioxide TiO2 suspensions under simulated solar irradiation. The degradation kinetics followed a pseudo-first-order reaction and has been monitored by headspace solid-phase microextraction (HS-SPME) and gas chromatographic techniques (GC-FTD). Degradation of both insecticides has been a rapid process with half-lives varied between 3.7 and 12.9 min depending on the TiO2 concentration as well as on the structure of the compound. The generated transformation by-products formed during the process were extracted by SPME used in two approaches: (a) by direct immersion in the filtered sample and (b) by exposing the fiber in the sample headspace. The intermediates were formed predominately via oxidation processes and were identified by gas chromatography and mass spectroscopy techniques.