Voltametria de onda quadrada cíclica voltada para determinação sequencial de sulfanilamida e ciprofloxacina em amostras de água utilizando dispositivo eletroquímico obtido por impressão 3D

Abstract

Ciprofloxacin (CIP) and sulfanilamide (SAD) are synthetic broad-spectrum antibiotics, belonging to the class of fluoroquinolones and sulfonamides, respectively, and the excessive consumption and inappropriate disposal of these pharmacological species contritute to the increase in the level of contamination in aquatic environments and, consequently, generate risk to human health. In this sense, this work proposes the additive manufacture (3D printing) of an electrochemical sensor based on carbon black/polylactic acid (CB/PLA), subjected to an chemical/electrochemical activation process, aiming at the sequential determination os CIP and SAD, using the cyclic square wave voltammetry (CSWV) technique. Initially, the square-wave voltammetry (SWV) was employed, sweeping in the anodic direction, to evaluate the feasibility of quantifying the analytes by exploring their oxidation processes (Ox1CIP and Ox1SAD, at around +1,3 V e +1,1 V vs. Ag|AgCl|KCl(sat.), respectively). However, the method did not present satisfactory selectivity, when applied in wastewater samples, losing the differentiation capacity between the electrochemical processes analyzed. Therefore, the CSWV protocol was used to enable the selective quantification of CIP and SAD, exploring the Ox1CIP oxidation process, in the anodic scan and the Red1SAD reduction process (at around +0,5 V vs. Ag|AgCl|KCl(sat.)), in the cathodic scan. Thus, using the CSWV technique, under optimized intrumental conditions, analytical calibration curves were constructed, whose linear ranges varied from 4,96 to 40,61 µmol L-1 (r = 0,9977) for Ox1CIP and from 1,99 até 10,78 µmol L-1 (r = 0,9989) for Red1SAD. The limits of detection obtained for CIP and SAD were 0,6 and 0,2 µmol L-1, respectively, and the sensitivity increased by 25% for CIP and 60% for SAD in comparison to the methodology based on SWV (anodic direction). Furthermore, the CSWV protocol ensured satisfactory selectivity to the developed method, considering that the determination of the analytes is performed at distinct potentials. Thus, when the methodology is employed on water samples (no dilution step), satisfactory recovery values were obtained (85 – 112 %), suggesting the accuracy of the method. Therefore, this work shows a strategy that combines the use of the 3D printed CB/PLA electrode, with the CSWV technique and ensures an improvement in selectivity and sensitivity in the sequential determination of the two emerging pollutants, CIP and SAD