Desenvolvimento de dispositivo microfluídico híbrido PDMS/vidro para a detecção eletroquímica de glifosato

Abstract

Micro Total Analysis Systens (μTAS) enable the integration of several steps of a chemical analysis within a single device. These systems have advantages such as low sample consumption, portability, integration with different detection techniques and relatively fast analysis. In this sense, this work proposes the development of a hybrid PDMS / Glass microfluidic device for the electrochemical detection of glyphosate in environmental samples. The device used has a 5cm separation channel with lateral arms of 0.75cm, with off-channel alignment for the working electrode, pinched sample injection and addition of surfactant to allow a reverse electroosmotic flow. Three different working electrodes were evaluated, with the copper electrode being the most efficient. Using cyclic voltammetry, it was shown that the detection of glyphosate can be performed from the complexation of the analyte with Cu (II) ions generated on the surface of the electrode. In general, the electrochemical mechanism associated to the process involves a reversible electrochemical step with the formation of Cu (II) ions and an irreversible chemical step that comprises the formation of the Cu (II) -glyphosate complex. Voltammetric detection of glyphosate using borate buffer obtained linear response in the range of 30 - 100 μM, with R = 0.998. Regarding the amperometric detection of the analyte, it was verified that the conventional amperometry is not satisfactory and the pulse amperometry presented promising results. The use of this technique in Micro Total Analysis Systems is an alternative for glyphosate detection, which can help researches to solve problems and detect important species.