Desenvolvimento de sensores eletroquímicos à base de compósitos para a determinação simultânea de fármacos

Abstract

In this doctoral thesis different carbon materials were explored for the development of novel electrochemical sensor platforms. Thus, a glassy carbon electrode modified with a functionalized graphene film, chitosan and nickel oxide nanoparticles was initially proposed. This sensor was used for the simultaneous determination of paracetamol and ciprofloxacin in biological fluid samples using square wave adsorptive anodic stripping voltammetry. Analytical curves were a linear in the concentration range of 0.10 to 2.9 µmol L−1 for acetaminophen and of 0.040 to 0.97 µmol L−1 for ciprofloxacin, with limits of detection of 6.7 and 6.0 nmol L−1, respectively. Next, salbutamol and propranolol were determined simultaneously in synthetic urine and serum samples. For this, a glassy carbon electrode was modified with functionalized graphene, ionic liquid and silver nanoparticles all immobilized in a Nafion® film. The electrochemical determination provided linear concentration ranges of 0.079 to 2.9 μmol L−1 for salbutamol and of 0.10 to 2.9 μmol L−1 for propranolol with limits of detection of 13 and 17 nmol L−1, respectively. Subsequently, a sensor based on the modification of a glassy carbon electrode with a carbon black film, silver nanoparticles and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) was developed. The viability and efficiency of this sensor was verified by the simultaneous determination of paracetamol and levofloxacin in environmental and biological samples, with a linear response of 0.62 to 7.1 μmol L−1 for paracetamol and of 0.67 to 1.2 μmol L−1 for levofloxacin with limits of detection of 12 and 14 nmol L−1, respectively. Finally, in the last part of this work, a carbon paste electrode was modified with functionalized graphite and β-cyclodextrin. The electroanalytical potentiality of this new sensory architecture was investigated against the applicability of simultaneous determination of levodopa, piroxicam, ofloxacin and methocarbamol in synthetic urine and river water samples, with limits of detection of 65, 105, 89 and 400 nmol L−1, respectively. In addition, all modifications were morphologically characterized using scanning electron microscopy, transmission electron microscopy, dispersive energy spectroscopy and/or contact angle, and also electrochemically by cyclic voltammetry and/or electrochemical impedance spectroscopy. In addition, the selectivity, precision and accuracy of the proposed methods were evaluated by possible interferences studies, intra- and inter-day repeatability measurements and comparison with UV-Vis spectroscopy, respectively.