Preparo e caracterização de um eletrodo modificado com biochar para a detecção voltamétrica e simult nea de catecol e hidroquinona

Abstract

Biochar (BO) is a material derived from the biomass pyrolysis in the absence or presence of low oxygen content and has recently been used as a low cost carbonaceous material for electroanalytical applications. In this work, biochar was prepared from pyrolysis of Babassu petiole and used as a modifier of glassy carbon electrode (GCE/BO). Firstly, the characterization of pyrolysed BO's using different temperatures was performed using the techniques thermogravimetry and simultaneous differential thermal analysis (TG-DTA) techniques, Fourier transform infrared (FTIR) spectroscopy and Brunauer-Emmett-Teller (BET) method. Then, the ECV modification was performed by the adsorption method, in which 8.0 L of a BO suspension (in water, dimethylformamide or chitosan of high and low molecular weight) were dropped onto the GCE surface (d = 3 mm) and the solvent allowed to evaporate for 2h at room temperature. By using cyclic voltammetry (CV) in the presence of potassium ferrocyanide solution in different GCE/BO, it was possible to note better stability and peak current when using a suspension containing 10 mg of BO (pyrolyzed at 800 ° C) in 1.0 mL of ultrapure water. In addition, CV and Randles-Sevcik equation showed an enhancement in the electroactive area of the modified electrode compared to the non-modified one (ECV/BO: 0.0720 vs ECV: 0.0265 cm2), behavior which was also verified by the BET method. Using this optimized ECV/BO, simultaneous detection of the emerging contaminants catechol (CT) and hydroquinone (HQ) was performed using square wave voltammetric detection. The best responses were obtained using Britton-Robinson buffer (pH 4) and optimized voltammetric parameters (Frequency: 10 Hz; Amplitude: 30 mV; Potential increase: 1.0 mV). In these conditions, ECV/BO showed good separation between the CT and HQ peaks (E = 132 mV), resolution not achieved in other working electrodes evaluated (glassy carbon, boron-doped diamond, graphite and nanofibre screen-printed electrodes). In order to demonstrate the ECV/BO potentiality, HQ and CT were simultaneously quantified in tap water using the standard addition method, in which recoveries close to 100 % for both analytes were reached. The results presented demonstrated high selectivity and sensitivity for these phenolic contaminants, and the ECV/BO is a promising electrode modifier, presenting good features for use in simultaneous determinations of similar chemical compounds at low concentration levels.