Liquid Chromatography/Electrochemistry : Thin-Layer Multiple Electrode Detection

Roston, Daryl A.; Shoup, Ronald E.; Kissinger, Peter T.

doi:10.1021/ac00250a767

Cited by 35 publications

(45 citation statements)

References 25 publications

(26 reference statements)

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“…This drawback could be avoided whenever comigrating analytes undergo electrochemical processes with different reversibility, if a detection strategy profiting from the detector performance is adopted. In this connection, the use of dual electrode detectors, already adopted for selective determinations in HPLC 33 and consisting of two parallel working electrodes with different applied potentials 34, 35, appears to be particularly profitable.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2013

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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.

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Section: Introductionmentioning

confidence: 99%

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

et al. 2013

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“…An ampli®cation factor of about three was reported by Takahashi et al [33], when employing redox cycling based detection in FIA. As a result of the relatively low degrees of redox cycling found for mLamin¯ow rates, it has been suggested that redox cycling based detection at microelectrode arrays is best suited for use in conjunction with miniaturized separation techniques operated at low (e. g.,`10 mLamin) ow rates [27,34]. The aim of the present paper is to evaluate the degree of redox cycling at microarray electrodes in conjunction with¯ow rates less than ca.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Detection Based on Redox Cycling Using Interdigitated Microarray Electrodes at µL/min Flow Rates

2000

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The in¯uence of convection on the degree of redox cycling at interdigitated microarray electrodes in a¯ow system was investigated in the end column detection mode for¯ow rates below 20 mL/min. It was found that the degree of redox cycling increased with decreasing¯ow rates and values of 2.9 and 2.2 were obtained for a¯ow rate of 2 and 20 mL/min, respectively, using photolithographically fabricated interdigitated arrays consisting of 140 microbands separated by 6 mm. The obtained degrees of redox cycling were lower than the value of 4.4 obtained in a stationary solution in the batch mode as a result of a decreased collection ef®ciency between adjacent microbands and a relatively low conversion ef®ciency at each microband in the presence of the¯ow. It is shown that a collection ef®ciency of more than 90 % is needed to produce an order of magnitude increase in the current due to redox cycling in a stationary solution. When using a microarray electrode consisting of 280 microbands in a thin layer¯ow cell, a conversion ef®ciency of close to 100 % could be obtained at¯ow rates below 1 mL/min. In the latter case, a signi®cantly larger¯ow rate dependence of the current was found compared to that for a single microband electrode.

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“…Como no início dos anos 2000 os LED UV surgiram, mas ainda com potências e fluxos radiantes bastante baixos (a exemplo o LED NSHU551A da Nichia de 100 mW), 119 a mínima espessura apresentada nas células microfluídicas era um requisito, já que o diodo emissor não daria conta de destruir com brevidade muito além do que a quantidade de matéria restringida no volume projetado acima do eletrodo. Mas, no início dos anos 2010, os LEDs UV de maior potência foram integrando o mercado, como o modelo NCSU033C da Nichia com potência nominal de 3,0 W, 120 sendo assim possível aumentar a espessura das células, atingindo a condição de células de camada delgada convencionais, como aquelas utilizadas em detectores de HPLC, 121 melhorando consideravelmente o controle de potencial durante a operação. Desse modo, Baccaro e Gutz 122 desenvolveram um protótipo de camada delgada do tipo sanduíche com espessura de 0,6 mm ( Figura 7).…”

Section: O Emprego Do Tio 2 Nanoparticulado Sob Irradiação Uv Para a unclassified

FOTOCATÁLISE MEDIADA POR TiO2 NO ESTADO NANOPARTICULADO: REVISÃO DA REATIVIDADE PELO CONCEITO DE TRAPS E ALGUMAS APLICAÇÕES EM QUÍMICA ANALÍTICA

Baccaro¹,

Cordon²,

Nishimura³

et al. 2019

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TiO 2-MEDIATED PHOTOCATALYSIS AT THE NANOPARTICULATE STATE: REVIEW OF THE REACTIVITY BY THE TRAPPING CONCEPT AND SOME APPLICATIONS IN ANALYTICAL CHEMISTRY. TiO 2 has been used as a white pigment and studied since the first decades of the XX century for the undesirable chalking of outdoor paintings exposed to sunlight. Since the first report of Honda and Fujishima (1972) of the water splitting by the harvesting of sunlight on a n-type single crystal TiO 2 electrode, the engagement of researchers with the field has grown steadily. TiO 2-photocatalysis has joined the group of advanced oxidation processes for potential new water and wastewater treatments but, despite of its high chemical and photochemical stability and the great oxidizing power of its photogenerated holes, photons in UVA spectral region are needed to accomplish the high band gap, limiting the yield of sun-driven environmental applications. Nevertheless, this shortcoming has not restricted benchtop research and small and medium scale applications also relying on artificial UV sources, especially nowadays that highly-efficient UVA-LEDs are available. Herein, we review the fundamental aspects and the practical attributions of the trapping model in the charge transfer kinetics of photogenerated holes in nanoparticulate TiO 2. Regarding to new practical uses, we focus our attention on some ingenious applications of this photocatalyst in the field of analytical chemistry, covering also subjects never reviewed before.

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Liquid Chromatography/Electrochemistry : Thin-Layer Multiple Electrode Detection

Cited by 35 publications

References 25 publications

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

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

Electrochemical Detection Based on Redox Cycling Using Interdigitated Microarray Electrodes at µL/min Flow Rates

FOTOCATÁLISE MEDIADA POR TiO2 NO ESTADO NANOPARTICULADO: REVISÃO DA REATIVIDADE PELO CONCEITO DE TRAPS E ALGUMAS APLICAÇÕES EM QUÍMICA ANALÍTICA

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