• Journal of Electrochemical Science and Technology
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• v.1 no.2
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• pp.121-126
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• 2010

An amperometric ascorbic acid selective sensor utilizing the transfer reaction of proton liberated from the dissociation of ascorbic acid in aqueous solution across an elliptic micro-hole water/organic gel interface is demonstrated. This redox inactive sensing platform offers an alternative way for the detection of ascorbic acid to avoid a fouling effect which is one of the major concerns in redox based sensing systems. The detection principle is simply measuring the current change with respect to the assisted transfer of protons by a proton selective ionophore (e.g., ETH 1778) across the micro-hole interface between the water and the polyvinylchloride-2-nitrophenyloctylether gel phase. The assisted transfer reaction of protons generated from ascorbic acid across the polarized micro-hole interface was first characterized using cyclic voltammetry. An improved sensitivity for the quantitative analysis of ascorbic acid was achieved using differential pulse stripping voltammetry with a linear response ranging from 1 to $100\;{\mu}M$ concentrations of ascorbic acid. As a demonstration, the developed sensor was applied for analyzing the content of vitamin-C in different types of commercial pharmaceutical tablets and syrups, and a satisfactory recovery from these samples were also obtained.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1734-1740
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• 2012

Voltammetric characterization of hydrophilic anion transfer processes across a 66 microhole array interface between the water and polyvinylchloride-2-nitrophenyloctylether gel layer is demonstrated. Since the transfer of hydrophilic anions including $Br^-$, $NO_3{^-}$, $I^-$, $SCN^-$ and $ClO_4{^-}$ across the liquid/gel interface usually sets the potential window within a negative potential region, a highly hydrophobic organic electrolyte, tetraoctylammonium tetrakis(pentafluorophenyl)borate, providing a wider potential window was incorporated into the gel phase. The transfer reaction of perchlorate anions across the microhole-water/gel interface was first studied using cyclic voltammetry and differential pulse voltammetry. The full voltammetric response of perchlorate anion transfer was then used as a reference for evaluating the half-wave transfer potentials, the formal transfer potentials and the formal Gibbs transfer energies of more hydrophilic anions such as $Br^-$, $NO_3{^-}$, $I^-$, and $SCN^-$. The current response associated with the perchlorate anion transfer across the micro-water/gel interface versus the perchlorate concentration was also demonstrated for sensing applications.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.443-455
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• 2013

Electrochemical studies on charge transfer reactions across the interface between two immiscible electrolyte solutions (ITIES) have greatly attracted researcher's attentions due to their wide applicability in research fields such as ion sensing and biosensing, modeling of biomembranes, pharmacokinetics, phase-transfer catalysis, fuel generation and solar energy conversion. In particular, there have been extensive efforts made on developing sensing platforms for ionic species and biomolecules via gelifying one of the liquid phases to improve mechanical stability in addition to creating microscale interfaces to reduce ohmic loss. In this review, we will mainly discuss on the basic principles, applications and future aspects of various sensing platforms utilizing ion transfer reactions across the ITIES. The ITIES is classified into four types : (i) a conventional liquid/liquid interface, (ii) a micropipette supported liquid/liquid interface, (iii) a single microhole or an array of microholes supported liquid/ liquid interface on a thin polymer film, and (iv) a microhole array liquid/liquid interface on a silicon membrane. Research efforts on developing ion selective sensors for water pollutants as well as biomolecule sensors will be highlighted based on the use of direct and assisted ion transfer reactions across these different ITIES configurations.