A novel protocol for ultra-trace detection of pesticides: combined electrochemical reduction of Ellman's reagent with acetylcholinesterase inhibition.

This paper proposed a novel method for ultra-trace detection of pesticides combining electrochemical reduction of Ellman's reagent with acetylcholinesterase (AChE) inhibition. The amperometric biosensor, fabricated by immobilizing AChE on multi-walled carbon nanotubes-chitosan (MWCNTs-Chi) nanocomposites modified glassy carbon electrode, enjoyed high sensitivity owing to the excellent conductivity and favourable biocompatibility of MWCNTs-Chi nanocomposites. Meanwhile, the sensitivity of the biosensor was further enhanced using the electrochemical reduction signal of DTNB for determination. Under optimum conditions, methyl parathion was detected based on its inhibition effect on AChE activity and the subsequent change in electrochemical reduction response of DTNB. Good relationship was obtained between the reduction current and pesticide concentration in the ranges of 5.0 × 10(-7) to 1.0 × 10(-12) M with a detection limit of 7.5 × 10(-13) M (S/N = 3). Moreover, the proposed protocol was successfully employed for the determination of methyl parathion in water and soil samples.