A comparative photodegradation studies of methyl parathion by using Lumistox test and conductometric biosensor technique

The photodegradation of methyl parathion, and the toxicity assessment of the resulting mixtures including the main degradation photoproducts (methyl paraoxon and 4-nitrophenol) have been investigated. The degradation was studied by monitoring the change in compounds concentration as a function of irradiation time by employing HPLC analysis. Toxicity tests were performed by using a conductometric biosensor based on cholinesterases and a bioassay based on a luminescent bacteria Vibrio fischeri (Lumistox). been found in the case of biosensors that the strongest inhibitor of immobilised cholinesterases was the methyl paraoxon and a strong synergistic effect of methyl parathion and methyl paraoxon occurred. Other results were obtained using Lumistox test, since in this case methyl parathion is the most toxic compound for V. fischeri, and similar toxicity were obtained for both 4-nitrophenol and methyl parathion. These results indicate that effect of toxic compounds on the luminescent bacteria is not related to cholinesterase activity. Both tests could be very useful to control an organophosphorous pesticides degradation process.