Desenvolvimento de dispositivo analítico usando impressão 3D para análises voltamétricas em microvolumes

Abstract

3D printing technology (additive manufacturing) has proven to be a powerful tool for building analytical devices. The novelty of this work is an adapter for commercial micropipettes, printed on a copolymer of acrylonitrile butadiene styrene (ABS) or polylactic acid (PLA), allowing the use of microelectrodes inside plastic tips. The work also deals with the construction of a simplified micropipette puller with materials easily obtained, for the making of the microelectrodes. The microelectrodes manufactured were characterized electrochemically and by optical microscopy, with a good agreement in the measured diameter values (about 10.01 μm for platinum and 18.57 μm for gold). The determination of catechol in synthetic sweat and saliva was performed using reduced sample volumes (5 μL), with recovery values ranging from 90 to 110%. It was also established instrumental detection and quantification limits of the order of 18 and 54 μmol L-1, respectively, for the synthetic saliva sample and 51.5 and 156.0 μmol L-1, respectively for the synthetic sweat sample. In a second moment, the adapter was tested in different organic and applied in the determination of ferrocene in 10 μL of DMF, presenting linearity in the range of 41 to 142 μmol L-1. Limits of detection and quantification of 7.5 and 22.8 μmol L-1, respectively, were established for the platinum microelectrode and 6.1 and 18.5 μmol L-1, respectively, for the gold microelectrode. It was also verified the process of radial diffusion involved, using the Thomeš criterion, obtaining a value of 55.2 mV. In the third moment of the project, an electroanalytical method was developed for determination of dopamine using platinum modified gold microelectrode. The tests showed that the modification brings a gain of about 40% of analytical signal, and that the presence of dopamine in the medium is highly dependent on the pH, with the consequent loss of analytical signal. The proposed method was evaluated with respect to the limits of detection and quantification, which were 15.6 and 51.9 μmol L-1, respectively. Favorable conditions were sought for the quantification of copper in a sample of water supply, with limits of detection and quantification of the order of 7.98 and 26.6 μg L-1 respectively and a linear range between the limit of quantification and 500 μg L-1. Finally, the determination of lead in water supply was carried out using gold microelectrode modified with bismuth film, with concentrations of lead between 30 and 180 μg L-1.