Desenvolvimento de um sistema miniaturizado para detecção eletroquímica em microvolumes

Abstract

The use of miniaturized systems has gained attention in electrochemical analysis, as they adequately respond to the requirements of high sensitivity, low-cost and sample consumption, minimizing the waste generation, which is highly desirable in the context involving Green Chemistry. Thus, a miniaturized system was made for electrochemical detection. This device consists of an electrochemical cell with three electrodes fixed in a conventional micropipette tip, which acts as a support. In the first step, aiming greater applicability, the device was tested as an amperometric detector for a single-line flow injection analysis (FIA) system. Initially, it was evaluated the main parameters of the FIA system, such as detection potential, flow rate and sampling loop. These studies allowed to visualize the effect of these parameters on the electrochemical signals. A potassium ferrocyanide solution was used as electrochemical probe for all analyzes and a 0.1 mol L-1 KCl solution was used as a carrier solution and supporting electrolyte. Subsequently, voltammetric studies were performed using a conventional electrochemical cell, which allowed to evaluate the use of the device in static mode by observing the voltammetric peaks corresponding to the [Fe(CN)6]4-/[Fe(CN)6]3- redox couple. For this study, cyclic voltammetry was used as characterization technique. After that, aiming to evaluate the versatility of the proposed device, electrochemical measurements were performed to detect carbendazim fungicide. For these studies, it was used a miniaturized electrochemical cell with a capacity of 500 µL of solution obtained from an eppendorff-like microtube. Differential pulse voltammetry was used as detection technique and the device produced great analytical signal for carbendazim. Based on these results, the proposed miniaturized device was efficient to be used as detector for static mode as well as flow analyses. Also, the device showed potentiality to be used in electroanalysis.