A novel disposable electrochemical microcell: construction and characterization

Abstract

Este trabalho apresenta uma técnica alternativa de microfabricação para construção de microcélulas eletroquímicas descartáveis contendo os eletrodos de trabalho, auxiliar e de referência em um único dispositivo. Trata-se de um processo simples no qual a termo-transferência de máscaras de toner sobre superfícies de ouro obtidas a partir de discos compactos graváveis (CD-R) definem o formato dos eletrodos (contornos). Numa etapa seguinte, o formato é manualmente coberto com tinta usando uma caneta de retroprojetor. A superfície de ouro não protegida pela tinta é convenientemente removida (corrosão química) e a tinta, por sua vez, é facilmente removida com etanol gerando superfícies de ouro sem contaminação. A área final e reprodutível dos eletrodos é definida pela termo-transferência de uma segunda máscara de toner. O eletrodo de referência é obtido por meio de uma deposição manual de cola de prata sobre uma banda de ouro. As microcélulas foram eletroquimicamente caracterizadas usando as técnicas de voltametria cíclica, voltametria linear e voltametria de onda quadrada e várias espécies eletroativas como sistemas modelo. A reprodutibilidade de área dos eletrodos para diferentes microcélulas foi estudada e um desvio-padrão relativo melhor do que 1,0% foi obtido. As microcélulas descartáveis foram usadas com sucesso para a análise de amostras em volumes menores que 200 µL demonstrando boa estabilidade e reprodutibilidade (RSD menor que 2,0%). Essas microcélulas também foram avaliadas para a quantificação de paracetamol e dipirona em formulações farmacêuticas.An alternative technique for the fabrication of disposable electrochemical microcells containing working, reference and auxiliary electrodes on a single device is reported. The procedure is based on thermal-transfer of toner masks onto CD-R (recordable compact discs) gold surfaces to define the layout of the electrodes (contour). In a subsequent step, the layout is manually painted with a permanent marker pen. The unprotected gold surface is conveniently etched (chemical corrosion) and the ink is then easily removed with ethanol, generating gold surfaces without contamination. The final and reproducible area of the electrodes is defined by heat transference of a second toner mask. Silver epoxy is deposited on one of the gold bands which is the satisfactorily used as reference electrode. These microcells were electrochemically characterized by cyclic, linear, and square wave voltammetry, and several electroactive species were used as model systems. The area reproducibility of the electrodes for different microcells was studied and a relative standard deviation better than 1,0% (n = 10) was obtained. Disposable electrochemical microcells were successfully used in analysis of liquid samples with volumes lower than 200 µL and good stability and reproducibility (RSD less than 2.0%) were achieved. These microcells were also evaluated for quantification of paracetamol and dipyrone in pharmaceutical formulations.Keywords: disposable electrochemical microcell, microfabri...

Three electrode electrochemical microfluidic cell: construction and characterization

“…This is in agreement with previous studies. 20 Moreover, the performance of the microfluidic cell was better when the pseudo reference electrode was used (located inside the microchannel), both with respect to sensibility and reversibility of the redox couple (ferro/ferricyanide). For cyclic voltammograms conducted in the stationary mode ( Figure 3A), the total current measured changed from 5.83 to 8.75 µA, when the conventional reference electrode was substituted by the silver composite pseudo-reference electrode.…”

“…The option for these ions as model analytes is supported by the potentiality of the gold working electrode used in the microcell to analyze these metals, as described in the literature. 24,25 Figure 4 presents the signals obtained for the simultaneous analysis of copper and mercury using potentiometric stripping analysis at constant current as function of the increasing concentrations of both metals (10,20,30,40 and 50 µg L -1 ). These chronopotentiograms were recorded using a flow rate of 60 µL min -1 and deposition time of 60 s. A comparison between the performance of the flow-through microcell with a conventional flow-through cell 26 shows a similar sensitivity for both cases, however, the flow rate necessary for the conventional cell to present the same response must be superior to 3.0 mL min -1 .…”

“…Some examples are: construction of amperometric microdetectors for conventional capillary electrophoresis system 5 and separation microsystems manufactured in polyester toner, 6 microfluidic cells with interdigitated array gold electrodes, 7 generator-collector electrochemical microdevices, [8][9][10] production of microchannels in glass, 11,12 microfluidics devices for sample treatment, 13,14 new procedures for flow rate control and sample injection in microfluidic cells, 15 microelectrode arrays, 16 electrodes with reproducible area, 17 integration of planar electrodes for contactless conductivity detection on polyester-toner electrophoresis microchips, 18 insertion of passive micromixers in microfluidic devices 19 and construction of electrochemical microcells containing the working, counter and reference electrodes in the same device. 20 In this work a simple methodology for the construction of flow through microcells with introduction of the three electrodes (working, counter and pseudo-reference) in microchannels is described. Two configurations of microcells are presented.…”

Analytical chemistry in Brazil: healthy and growing

“…Disposable electrochemical micro-cells incorporating working, reference and auxiliary electrodes on a single device were constructed by means of thermaltransfer of toner masks to gold surfaces obtained from recordable CDs. 289 Preparation of the micro-cells was very reproducible, with a relative standard deviation of the electrodes area better than 1.0% (n = 10). In another work, a three electrode electrochemical microfluidic cell was proposed and characterized.…”

Cheap and disposable gold and silver electrodes: Trends in the application of compact discs and digital versatile discs for electroanalytical chemistry

“…Ferreira et al [58] have utilised a similar approach for the determination dipyrone, along with Pb Cu, Hg, paracetamol and nitrite. Interestingly, their investigation showed the possibility to use a permanent marker pen to define the electrode design on the Au CD-R after defining by laser jet printing.…”