title: Decay profile and metabolic pathways of quinalphos in water, soil and plants.
abstract: The widespread occurrence of pesticide residues in different agricultural and food commodities has raised concern among the environmentalists and food chemists. In order to keep a proper track of these materials, studies on their decay profiles in the various segments of ecosystem under varying environmental conditions are needed. In view of this, the metabolites of quinalphos in water and soil under controlled conditions and in plants, namely tomato and radish in field conditions have been analysed and possible pathways suggested. In order to follow the decay of the pesticide, an HPLC procedure has been developed. Studies conducted in water at different temperatures, pH and organic content reveal that the persistence of the pesticide decreases with the increase in all the three variables. In the three different types of soils studied, the effect of pH is more or less apparent on a similar line. On an average a faster decay is observed in the case of plants than in water and soil. The decay profiles in all these cases follow first order kinetics. The metabolites were identified by GC-MS. The investigations reflect that degradation occurs through hydrolysis, S-oxidation, dealkylation and thiono-thiol rearrangement. The pathways seem to be complex and different metabolites were observed with the change in the matrix. Quinalphos oxon, O-ethyl-O-quinoxalin-2-yl phosphoric acid, 2-hydroxy quinoxaline and quinoxaline-2-thiol were observed in all the matrices. Results further indicate that the metabolites, 2-hydroxy quinoxaline and oxon, which are more toxic than parent compound, persist for a longer time.
authors.affiliation: Analytical Laboratory, Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247 667 (UK), India. bvgcyfcy@iitr.ernet.in
authors.forename: Bina
authors.initials: B
authors.lastname: Gupta
authors.forename: Manviri
authors.initials: M
authors.lastname: Rani
authors.forename: Rahul
authors.initials: R
authors.lastname: Kumar
authors.forename: Prem
authors.initials: P
authors.lastname: Dureja
mesh_terms: D002851:Chromatography, High Pressure Liquid; D008401:Gas Chromatography-Mass Spectrometry; D007306:Insecticides / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D009946:Organothiophosphorus Compounds / Q000378:metabolism*; D031224:Raphanus / Q000378:metabolism*; D012987:Soil / Q000032:analysis; D012989:Soil Pollutants / Q000378:metabolism*; D014867:Water / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D007306:Insecticides; D009946:Organothiophosphorus Compounds; D012987:Soil; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D014867:Water; C009145:quinalphos