Pencil‐Drawn Dual Electrode Detectors to Discriminate Between Analytes Comigrating on Paper‐Based Fluidic Devices but Undergoing Electrochemical Processes with Different Reversibility

Abstract

A simple method is described to discriminate between analytes comigrating under on‐plate separation conditions, whose electrochemical behavior displays different reversible characters. It is based on the use of dual electrode detectors pencil‐drawn at the end of paper‐based fluidic channels defined by hydrophobic barriers. Simultaneous detection of comigrating species is achieved by applying to the upstream pencil‐drawn working electrode a potential for the oxidation (or reduction) of both analytes, while to the downstream pencil‐drawn working electrode a potential is imposed for the reverse process involving the product of the sole analyte undergoing a reversible enough electrochemical process. The performance of these inexpensive devices was preliminarily optimized by adopting hexacyanoferrate(II) as prototype species undergoing a reversible anodic process at carbon electrodes. They were then used as dual electrode detectors for thin‐layer chromatographic runs conducted on paper‐based microfluidic devices. Two types of synthetic solutions, one containing different contents of dopamine (DA) and ascorbic acid (AA) and the other of paracetamol (PA) and AA, were chosen as model samples. This choice was prompted us by the fact that in both cases these analytes comigrated under the adopted experimental conditions and required similar enough oxidation potentials. Nevertheless, DA and PA underwent reversible enough anodic processes while an irreversible electrochemical reaction is involved in the AA oxidation. Satisfactory results were found for both couples of target analytes, whose simultaneous detection was achieved within 230 s and was characterized by good enough repeatability and sensitivity. In particular, this approach appears to be well suited for the rapid and inexpensive assembling of electrochemical detectors for flow analysis systems.

Detection of Analgesics and Sedation Drugs in Whiskey Using Electrochemical Paper‐based Analytical Devices

“…Considering the manual processing for manufacturing ePADs, the achieved RSD is acceptable and demonstrates that the proposed approach exhibits high reproducibility. It is important to highlight that the RSD values achieved in this current study are lower than most reports associated with ePADs created with graphite pencil . The low RSD values can be associated with the use of a polyester mold for defining the electrode area, which ensures better reproducibility.…”

The voltammetric behaviour of lead at a hand drawn pencil electrode and its trace determination in water by stripping voltammetry

“…Hydrogen peroxide formed during the enzymatic reaction of glucose resulted in the oxidation of 4-aminophenylboronic acid to 4-aminophenol which was determined voltammetrically at the Pencil drawn electrode (PDE). Dossi et al [17] have also explored the electrochemical behaviour of ascorbic acid, dopamine and paracetamol by cyclic voltammetry at their PDEs and have reported well-defined redox behaviour. Thin-layer chromatography was used to separate mixtures of these compounds and co-eluting species could be identified using a dual electrode redox system formed from two in series PDEs.…”

Desenvolvimento de sensores eletroquímicos e colorimétricos para aplicações em amostras de interesse forense

“…Algumas das vantagens do dispositivo proposto é o baixo custo do papel sulfite utilizado como substrato, como previamente mencionado, sem necessidade de um processo de isolamento com um polímero sobre a face de trás do dispositivo para evitar perda de solução durante as medições [47,48,134], além de que não foi observado deformações do papel quando molhado pelo líquido durante as análises como observado com os dispositivos feitos com papel cromatografico. A Tabela 5 apresenta uma comparação entre os substratos, eletrodos, materiais e instrumentação necessária para a fabricação de alguns dispositivos baseados em papel relatados na literatura.…”

“…Podem ainda ser confeccionados os eletrodos usando métodos mais sofisticados como a deposição metálica por sputtering [42,43]. Para uso de eletrodos carbonáceos, além do uso de tinta condutiva, há trabalhos que fazem o uso do grafite [44,45] e da pintura direta no papel com minas de grafite [46][47][48]. Uma abordagem alternativa é o uso de fios metálicos fixados sobre a superfície do substrato de papel [49,50].…”

“…No campo que concerne o desenvolvimento de sensores eletroquímicos descartáveis e portáteis, há diversas pesquisas realizadas na literatura para a fabricação de eletrodos do tipo impressos através de diferentes tecnologias, mas basicamente utilizando tintas condutivas de carbono e outros metais [125][126][127], utilizando fios metálicos [49,128], construção de dispositivos em circuitos eletrônicos [78,129], confecção a partir de CDs (CDtrodos) [130][131][132], utilização direta de grafites [45,101] ou ainda "pintando/desenhando" com grafite sobre um substrato, comumente papel [47,48], entre outras formas.…”