Standardization and application of thin layer chromatography-enzyme inhibition method for detection of organophosphate and organocarbamate pesticides in model mixture.

摘要

A simple, rapid and sensitive thin layer chromatography-enzyme inhibition (TLC-EI) method was standardized for the separation of a model mixture of eight organophosphorus (OP; monocrotophos, malathion, parathion-methyl, dimethoate, phosphamidon, chlorpyriphos, phorate and quinalphos) and one organocarbamate (OCm; carbaryl) compounds, which were currently used in India. The best resolution was achieved with precoated TLC aluminium sheet (20 cm x 20 cm) of aluminium oxide 60 F254 neutral type E (200 micro ) with the solvent system acetone:hexane (30:70 v/v) at 25 degrees C. Reproducible results were achieved using TLC-enzyme inhibition (TLC-EI) technique with 10% goat liver homogenate in isotonic sodium phosphate buffer (0.01 M, pH 7.4) as source of esterase, 0.5% b-naphthyl acetate in acetone as substrate and 0.4% of 4-nitrobenzene diazonium tetrafluroborate in acetone as chromogenic agent. The locations of pesticide inhibition of enzyme on the chromatogram appeared as clear white spots on orange background, which were very stable. The detection limit of the method was 0.1 mg for chlorpyriphos, phorate, malathion, parathion-methyl, quinalphos and carbaryl. Detection limits were 2.5 and 7.5 micro g for dimethoate and monocrotophos and phosphamidon, respectively.