A sensitive electrochemical acetylcholinesterase (AChE) biosensor was successfully developed on polyaniline (PANI) and multi-walled carbon nanotubes (MWCNTs) core-shell modified glassy carbon electrode (GC), and used to detect carbamate pesticides in fruit and vegetables (apple, broccoli and cabbage). The pesticide biosensors were applied in the detection of carbaryl and methomyl pesticides in food samples using chronoamperometry (CA). The GC/MWCNT/PANI/AChE biosensor exhibited detection limits of 1.4 and 0.95μmolL(-1), respectively, for carbaryl and methomyl. These detection limits were below the allowable concentrations set by Brazilian regulation standards for the samples in which these pesticides were analysed. Reproducibility and repeatability values of 2.6% and 3.2%, respectively, were obtained in the conventional procedure. The proposed biosensor was successfully applied in the determination of carbamate pesticides in cabbage, broccoli and apple samples without any spiking procedure. The obtained results were in full agreement with those from the HPLC procedure.

Bismuth films (BiF) deposited in situ on graphite-polyurethane composite electrodes were successfully used for the determination of Zn, Cd, Pb, Cu and Hg, simultaneously in acetate buffer solution pH 4.5 using square wave anodic stripping voltammetry. It is possible to determine metals reoxidized at potentials more negative and more positive than Bi using in situ deposited BiF; reoxidation was studied by electrochemical impedance spectroscopy. The BiFmodified electrode was applied to analyse tap water. The influence of surface-active compounds, Triton X-100 and bovine serum albumin, on the stripping of these metals was investigated; Nafion coatings did not significantly improve the performance.

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Food safety is a major concern for human health and wellbeing all over the world. A novel and sensitive biosensor based on reduced graphene oxide (rGO) and the enzyme acetylcholinesterase (AChE) was developed and applied for the detection of carbaryl in food samples. The glassy carbon/rGO/AChE biosensor was characterized morphologically and electrochemically using scanning electron microscopy and cyclic voltammetry/electrochemical impedance spectroscopy, respectively. Optimum differential pulse voltammetry conditions led to a nanomolar detection limit, and determination of carbaryl in tomato was achieved.

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