A Cameroonian smectite clay collected in a deposit on Sabga hill (West Cameroon, Central Africa – denominated as Sa) and a metal free meso-tetra(4-carboxyl phenyl)porphyrin (shortened as TCPP) were used to modify carbon paste electrodes. They were then exploited for the simultaneous electrochemical detection of dopamine (DA), acetaminophen (AC) and tyrosine (Tyr). Square wave voltammetry (SWV) revealed an increase in oxidation peak responses along with a negative shift of the corresponding anodic peak potentials for DA, AC and Tyr when using a carbon paste electrode modified with clay and porphyrin (TCPP–Sa/CPE), in comparison with those obtained at carbon paste electrodes modified with either clay (Sa/CPE) or porphyrin (TCPP/CPE). The TCPP–Sa/CPE exhibited attractive characteristics such as extended linear ranges, high sensitivities and selectivities, and low limits of detection for DA (0.1 μM), AC (0.2 μM) and Tyr (0.7 μM), using square wave voltammetry. The developed sensors were applied to the determination of AC in a pharmaceutical preparation and simultaneously DA, AC and Tyr in human urine.

In this work, an electrode modified with an amino-functionalized clay mineral was used for the electrochemical analysis and quantification of quercetin (QCT). The resulting amine laponite (LaNH₂) was used as modifier for a glassy carbon electrode (GCE). The organic–inorganic hybrid material was structurally characterized using X-ray diffraction, Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and CHN elemental analysis. The covalent grafting of the organosilane to the clay backbone was confirmed. The charge on the aminated laponite, both without and with the protonation of NH₂ groups, was evaluated via cyclic voltammetry. On the protonated amine (LaNH₃⁺)-modified GCE, the cyclic voltammograms for QCT showed two oxidation peaks and one reduction peak in the range of −0.2 V to 1.2 V in a phosphate buffer–ethanol mixture at pH 3. By using the differential pulse voltammetry (DPV), the modification showed an increase in the electrode performance and a strong pH dependence. The experimental conditions were optimized, with the results showing that the peak current intensity of the DPV increased linearly with the QCT concentration in the range from 2 × 10⁻⁷ M to 2 × 10⁻⁶ M, leading to a detection limit of 2.63 × 10⁻⁸ M (S/N 3). The sensor selectivity was also evaluated in the presence of interfering species. Finally, the proposed aminated organoclay-modified electrode was successfully applied for the detection of QCT in human urine. The accuracy of the results achieved with the sensor was evaluated by comparing the results obtained using UV–visible spectrometry.

Sawdust samples of ayous wood (Triplochiton scleroxylon) have been submitted to a warm pretreatment with NaOH and functionalized in dimethylformamide (DMF) by grafting with two amino organosilanes. The reagents were chosen for their ability to bind hydronium ions in acidic medium: 3-aminopropyltriethoxysilane (APTES) and 3-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS). The resulting materials were characterized by Fourier transform infrared (FTIR) and ¹³C nuclear magnetic resonance (NMR) spectroscopies, which revealed the Si-O-C covalent bond and the polymerization of the grafted silanes through siloxane bridges (Si-O-Si) leading to the stabilization of the structure. The cyclic voltammetry analyses were performed on a glassy carbon modified with native or functionalized sawdust films in contact with electrochemical probes ([Fe(CN)₆]^3- and [Ru(NH₃)₆]³⁺). By means of this method, the permselectivity and accumulation capacity of these functionalized materials could be evaluated. The presence of silanes in the functionalized sawdust leads to a progressive accumulation of anionic species, while the cationic species were repelled when the solution is gradually acidified.