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Preparação, caracterização e aplicação de um novo sensor baseado em nanopartículas de prata para a determinação de poluentes nitroaromáticos

  • Lima, Camila Alves de
Publication Date
Jan 01, 2016
Repositório Institucional da UFSC
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Abstract: This work describes the development of a modified electrode with silver nanoparticles (AgNPs) and the practical application for the detection of nitroaromatic pollutants. A colloidal dispersion containing stabilized AgNPs in chitosan was used to modify the glassy carbon electrode surface. The dispersion was characterized by techniques of UV-visible spectroscopy and transmission electron microscopy. The obtained device was named nAg-chitosan/GCE and it was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. Then, the sensor was applied for detection of nitroaromatic compounds. Initially, the nAg-chitosan/GCE was used to investigate the reduction electrochemical of 4-nitrophenol (4-NF). The nitrocompound showed a reduction signal at 0.410 V in Britton-Robinson buffer 0.1 mol L-¹(pH 3.0) and it was used as analytical signal to develop methodology. Using the optimized conditions of the square wave voltammetry, the calibration curve has showed a linear behavior in the range from 0.07 to 2.00 µmol L-¹ (R2 = 0.994) with a limit of detection (LOD) of 0.070 µmol L-¹ and limit of quantification (LOQ) of 0.286 µmol L-¹. As the sensor responded well to the nitro group reduction present in the 4-NF molecule, methods were developed for determination of two pesticides that have the nitro group in its chemical structure. The first methodology was developed for the determination of pesticide pendimethalin (PDM) and the second for the organophosphate ethyl parathion (EPT). For both, it was used Britton-Robinson buffer 0.1 mol L-¹ pH 4.0) and adsorptive stripping square wave voltammetry. The calibration curve was linear for PDM in the concentration range of 0.07 to 2.00 µmol L-¹ (R2 = 0.998) with a LOD and LOQ 0.039 and 0.119 µmol L-¹, respectively. The developed method was applied to determine PDM in mineral and tap water samples. Recovery assays ranged from 95-100% for the mineral water sample, and 93-103% for the tap water sample, indicating absence of interferents.The proposed methodology for determination of EPT has also showed good results. The linear working range obtained by the calibration curve was 0.04 to 8.00 µmol L-¹ (R2 = 0.993), with LD and LQ of 0.04 and 0.92 µmol L-¹ respectively. The determination of organophosphate was performed in lettuce and honey samples. The EPT recovery tests on lettuce sample ranged from 98-101% and on honey sample 96 to 101%. The results of the determination obtained by the comparative method to14both pesticides corroborate to the results obtained using the proposed sensor. All these results confirm that the use of nAg-chitosan/GCE sensor for determination of nitroaromatic pollutants was feasible, providing precise and accurate results.

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