Abstract
Mesoporous silicas have properties that allow their wide chemical application, due to the large amount of silanol groups on their walls. The possibility of introducing functional groups inside and on the surface of their pores becomes viable the use of these functionalized mesoporous materials for the adsorption of metal ions. Cooper ions are essential for vital functions, but in high concentrations, they are responsible for causing problems to the human organism. Therefore, it is important to monitor the species in different media, such as sugar cane spirit. Mesoporous materials type MCM-41 functionalized were obtained by three different methods using direct (in situ) and indirect (post-synthesis) routes. The mesoporous materials have exhibited properties according to the IUPAC classification. Modified carbon paste electrodes (MCPEs) were prepared by immobilizing the synthesized materials for Cu2+ analysis. The modified electrode obtained by the immobilization of functionalized mesoporous R2 (MCPE/R2) presented the best sensitivity for Cu2+ detection. Under optimum experimental conditions, the MCPE/R2 exhibited a linear range in between 0.99 and 11.80 μmol L-1, a sensitivity based on the Limit of Detection (LOD) of 0.50 μmol L-1and Limit of Quantification (LOQ) of 0.99 μmol L-1, precision (DPRmáx) equals to 10.6% and recovery of 92.2%. The developed method proved to be efficient for Cu2+ determination in sugar cane spirit and the accuracy of the results were comparable to those obtained by AAS.
Highlights
Mesoporous silica has physical-chemical properties that can be modified to be applied in several research areas [1]
The bands around 1555 and 693 cm-1 are attributed to NH deformation bond, evidencing the process of functionalization of the mesoporous silica [25]
The proposed routes were able to synthesize functionalized mesoporous silica matrices with pore sizes within the IUPAC established for this classification
Summary
Mesoporous silica has physical-chemical properties that can be modified to be applied in several research areas [1] Modifications of these materials can be carried out by direct (hydrothermal or non-hydrothermal) methods and indirect (post-synthesis) methods such as aqueous impregnation, ion exchange of the driver and immobilization. Brazilian legislation determines the limit of 5.0 mg L-1 of copper in sugar cane spirit while international legislation determines lower limits (2.0 mg L-1) [7, 8]. In this context, the search for sensitive, portable, versatile, and low-cost technique to analyze traces of copper ions is necessary [9]. Among the new methods suggested in the literature, such as resonance, calorimetry, fluorescence, raman scattering and optical sensors, the electrochemical sensors arise as a promising alternative, since they are sensitive and selective as conventional methods, in addition to ease operation and capacity of miniaturization [12]
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