No abstract

Despite the enormous development of instruments for analyzing a wide variety of compounds, applied in different fields such as health, environment or quality control, the demand for increasingly sensitive and selective techniques continues to grow. In this regard, efforts have been made to highlight more appropriate techniques. Electrochemical sensors based on molecularly imprinted polymers (MIPs) offer an interesting alternative since they allow reaching high sensitivity and selectivity and they are inexpensive and easily adaptable to miniaturization. The choice of the functional monomer in the synthesis of MIPs is based on its capacity to provide complementary interactions with the target molecules. The various excellent properties of chitosan, as a biosourced polymer, make it a promising alternative to conventional functional monomers. This review reports on the principle of the MIPs technique describing the different possible approaches in their synthesis. It aims to provide an overview of the value of using chitosan as a functional monomer by highlighting its applications in electrochemical sensors.

No abstract

The objective of this study is to optimize experimental conditions of the phenol adsorption process onto granular activated carbon by using an experimental design methodology. The process is studied in a fixedbed reactor. A rotatable and orthogonal central composite design at five levels allowed us to acquire a second-order model with the terms of interaction between the four influential factors chosen. The optimal values of flow rate solution, carbon bed height, temperature, and initial phenol concentration of the solution are equal to 1.67 mL · s -1 , 14.72 cm, 30°C, and 94.35 mg · L -1 , respectively. An optimal adsorption yield (99.33 %) is acquired after only 1 h of experimentation.

No abstract

A novel impedimetric microsensor based on a double-layered imprinted polymer film has been constructed for the sensitive detection of the herbicide, glyphosate (GLY), in water. It is based on electropolymerized polypyrrole films, doped with cobaltabis(dicarbollide) ions ([3,3′-Co(1,2-C2B9H11)2]), as a solid contact layer between the gold microelectrode surface and the molecularly imprinted chitosan film (CS-MIPs/PPy/Au). Electrochemical Impedance Spectroscopy (EIS) was used for the characterization of the CS-molecular imprinted polymers (MIPs)/PPy/Au in the presence of GLY concentrations between 0.31 pg/mL and 50 ng/mL. Experimental responses of CS-MIPs/PPy/Au are modeled for the first time using an exact mathematical model based on physical theories. From the developed model, it was possible to define the optimal range of the parameters that will impact the quality of impedance spectra and then the analytical performance of the obtained microsensor. The obtained microsensor shows a low detection limit of 1 fg/mL (S/N = 3), a good selectivity, a good reproducibility, and it is regenerable.

In this paper, a simple, economical, selective and sensitive electrochemical sensor is proposed for the quantification of vanillin (VAN) in real food samples. It consists of a carbon paste electrode (CPE) nanostructured with Fullerene (FNTs) and functionalized multi-walled carbon nanotubes (f-MWCNTs). The developed electroanalytical method was performed with cyclic voltammetry after optimization of operating conditions, such as supporting electrolytes, pH values and accumulation time. After optimization, the nanostructured sensor showed wide linear responses in the range from 5x10 -8 to 9x10 -6 mol.L -1 for VAN trace levels and from 10 -5 to 10 -4 mol.L -1 for higher concentrations, with a low detection limit of 3.4x10 -8 mol.L -1 . For concentrations lower than 10 -5 mol.L -1 , VAN was stripped after a previous quick adsorption step (300 s). The f-MWCNTs-FNTs/CPE sensor showed a good stability, repeatability and reproducibility (less than 7 %). This nanostructured sensor was successfully applied to determine VAN concentration as additive in commercial vanilla sugar samples with a satisfactory recovery and a good accuracy (< 6.5 %) in comparison with UPLC/UV control method.

A novel electrochemical impedance spectroscopy (EIS) microsensor was implemented for the dosage of traces of glyphosate, in real and synthetic water samples. Molecularly imprinted chitosan was covalently immobilized on the surface of the microelectrode previously modified with 4-aminophenylacetic acid (CMA). The characterization of the resulting microelectrodes was carried out by using cyclic voltammetry measurement (CV), scanning electron microscopy (SEM), and electrochemical impedance spectrometry (EIS). EIS responses of the CS-MIPs/CMA/Au microsensor toward GLY was well-proportional to the concentration in the range from 0.31 × 10−9 to 50 × 10−6 mg/mL indicating a good correlation. The detection limit of GLY was 1 fg/mL (S/N = 3). Moreover, this microsensor showed good reproducibility and repeatability, high selectivity, and can be used for the detection of GLY in river water.