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Pesticides and herbicides contamination in soil, groundwater, rivers, lakes, rainwater and air is considered a matter of concern. Some techniques are used to detect the presence of those compounds, here in this review is considered some recent voltammetric techniques such as cyclic voltammetry, square wave voltammetry, differential pulse, electrochemical impedance spectra and bifferential pulse polarography. Besides, the most used materials in their electrodes such as carbon, polymers, clay materials, biomolecules, metal oxides and micro and nanostructured materials are briefly considered. For all those techniques and materials are shown some current studies, researches and new approaches, considering their high sensitivity and specificity for pesticides and herbicides detection.

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A synthesis of β-cyclodextrin (β-Cd) functionalized with polyamide dendrimer PAMAM G.0 complexed with silver and potassium hexacyanoferrate (III) forming a mixed-valence complex (β-Cd-PAMAM-Ag/Fe) was proposed. This material was characterized by scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), X-Ray diffraction (XRD), Energy Dispersion Spectroscopy (EDS) and Electron Paramagnetic Resonance (EPR). The hybrid complex was electrochemically investigated using cyclic voltammetry and some parameters (electrolyte, concentration of electrolyte, pH and scan rate) were evaluate in order to obtain optimum analytical responses. The β-Cd-PAMAM-Ag/Fe material was successfully applied in the electrocatalytic oxidation of dopamine (DOP) using Cyclic Voltammetry (CV) and Square Wave Voltammetry (SWV).

Inorganic-organic hybrid materials, such as silica gel functionalized with an organic group, offer many applications in several areas of interest. The adsorptive properties provided by these materials due to the presence of active donor atoms such as O, N and S of grafted organic groups, suggests their application in metal ions adsorption as well as in the preparation of electrochemical sensors for substances of interest. In this work a hybrid material formed by interaction of a 3-chloropropyl silica gel modified with imidazole was characterized by techniques such as infrared spectroscopy, 29 Si and 13 C nuclear magnetic resonance and analysis of surface area and porosity. Adsorption studies were carried out for cadmium (II) in different media, and the quantity of adsorbed metal increased according the following order of solvents: water < ethanol 42% < ethanol 99%. After cadmium ions adsorption, the material was reacted with potassium hexacyanoferrate forming the material CdHSGI that was incorporated into a graphite paste electrode. Electrochemical studies were conducted with cyclic voltammetry. The cyclic voltammogram showed one redox couple with average potential E θ = 0.25 V (vs Ag/AgCl, NaNO 3 1.0 mol L −1 ; v = 20 mVs −1), attributed to the Fe 2+ (CN) 6 / Fe 3+ (CN) 6 process. The modified electrode allowed the electrocatalytic ascorbic acid determination. Through voltammograms it was possible to observe a linear range from 1.0 × 10 −4 mol L −1 to 9.0 × 10 −4 mol L −1 (R = 0.996) for the ascorbic acid determination with a Devaney Ribeiro do Carmo