Electrochemical quantification of chlorpyrifos in white (Allium cepa l.) and green (Allium fistulosum l.) onions

The Linear sweep voltammetry method (LSP) of a common pesticide such as chlorpyrifos (CPF) an organophosphorus (POF) in white ( Allium cepa l.) and green onions ( Allium fistulosum l.) was investigated.  It used at a working electrode static mercury drop (HMDE), Ag/AgCl as reference electrode and platinum as a counter electrode.  The POF was extracted from the onion through liquid-liquid partition using acetone/dichloromethane as the solvent.  Validated method was compared with GC/ECD as a reference method . CPF concentration was not different between the two analytical techniques; the analysis was performed with a confidence level of 90%, corresponding to the polarographic method.  CPF concentration was 0.8400 ± 0.062 ppm in Allium cepa and 0.062 ± 0.300 ppm in Allium fistulosum L.  These values exceed the ADI and ARD values for chlorpyrifos established by current regulations.