Construção de dispositivos microfluídicos usando técnicas alternativas de baixo custo: aplicação na determinação de contaminantes em amostras de interesse socioambiental

Abstract

Channel-based microfluidic devices have been useful in the miniaturized analytical system, however, the most critical part in the development of microfluidic platforms remains the detection system and its integration into the channel. Currently, electrochemical detectors are the most suitable for its integrations. There are many ways to manufacture the channel on microfluidic platforms, and, one way involves the use of alternative technologies that enable use of low-cost materials. This allows to produce several designs of microfluidic devices and new configurations of electrochemical detectors directly integrated. In this work, unconventional protocols were developed for building microfluidic devices based on polydimethylsiloxane (PDMS). As such, microfluidic devices with planar geometries, in which the internal channel (in the form of a serpentine), and a new configuration of electrochemical detection system were mounted onto a single chip. Target technology for produce microdevices is simple, low cost and requires minimal knowledge in microfabrication process. The proposed microfluidic platforms were tested for solve some problems arising from the use of automatic micropipettes during discrete injections as well as the use of surfactants into the carrier solution. The experimental results demonstrated the high performance of the integrated electrochemical detector system, showing high tolerance to the presence of air bubbles and no disturbance during the discrete injections. Also, we also showed the analytical performance of the PDMS-based microfluidic device for amperometric detection of salicylic acid (SA) in some aqueous samples. Then, this device was also used for separation of SA and caffeine (CAF) after activation of the inner channel wall with sodium hydroxide solution (2.0 mol L-1) and further simultaneously detection of both analytes in amperometric mode.