Determination of pesticides in vegetable samples using an acetylcholinesterase biosensor based on nanoparticles ZrO₂/chitosan composite film

An amperometric pesticides inhibition biosensor has been developed and used for determination of pesticides in vegetable samples. To eliminate the interference of ascorbic acid, multilayer films of polyelectrolyte (chitosan/polystyrensulfonate) were coated on the glass carbon electrode. Then, acetylcholinesterase was immobilized on the electrode based on surface-treated nanoporous ZrO2/chitosan composite film as immobilization matrix. As a modified substrate, acetylthiocholine was hydrolysed by acetylcholinesterase and produced thiocholine which can be oxidized at +700 mV vs. SCE. Pesticides inhibit the activity of enzyme with an effect of decreasing of oxidation current. The experimental conditions were optimized. The electrode has a linear response to acetylthiocholine within 9.90 × 10−6 to 2.03 × 10−3 M. The electrode provided a linear response over a concentration range of 6.6 × 10−6 to 4.4 × 10−4 M for phoxim with a detection limit of 1.3 × 10−6 M, over a range of 1.0 × 10−8 to 5.9 × 10−7 M for malathion, and over a range of 8.6 × 10−6 to 5.2 × 10−4 M for dimethoate. This biosensor has been used to determine pesticides in a real vegetable sample.