Eletrochemical evaluation of a sensor modified with tucumã biochar for analysis of environmental samples

Abstract

In this study, a carbon paste electrode modified with tucumã biochar (EPCM/TB) was produced for the determination of pyridine in industrial effluents. To develop the methodology, different paste proportions were evaluated, and a proportion of 40:30:30 (m/m/m) of graphite:tucumã biochar:binder was selected. Cyclic voltammetry was used to characterize the charge and mass transfer process of the electrochemical system; the reaction occurred with the transfer of two electrons. The reaction was irreversible and controlled by diffusion. The experimental variables such as the supporting electrolyte, pH and instrumental parameters of the differential pulse voltammetry (DPV) technique were evaluated. After the optimization of these parameters, four analytical curves were constructed using DPV to calculate the matrix effect (ME). The analytical curves in the presence of the matrix showed good linearity for the three effluents, with R2 values of 0.991, 0.997 and 0995. The limits of detection (LODs) for effluents 1, 2 and 3 were 34.9, 5.5 and 36.8 nmol/L, respectively. The limits of quantification (LOQs) for effluents 1, 2 and 3 were 116.6 nmol/L, 18.4 nmol/L and 122.6 nmol/L, respectively. The MEs of the three effluent samples showed values above 50.0 %, indicating strong MEs; therefore, the quantification of pyridine was performed using the matrix curves. The method had recoveries close to 100 % for the three effluents. The repeatability and reproducibility studies of the method provided RSD% values below 5 %; therefore, the method has potential application in the quantification of pyridine in textile effluents.