Chronopotentiometric method for the assessment of ionophore diffusion coefficients in solvent polymeric membranes

Bodor, Sándor; Zook, Justin M.; Lindner, Ernő; Tóth, Klára; Gyurcsányi, Róbert E.

doi:10.1007/s10008-008-0614-3

Cited by 24 publications

(35 citation statements)

References 47 publications

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“…Such stability of the asymmetric membrane might be attributed to the high PVC content in the membrane matrix which prolongs the penetration of the ion exchanger from the surface layer into the membrane bulk. 31 …”

Section: +mentioning

confidence: 99%

Trace-Level Potentiometric Detection in the Presence of a High Electrolyte Background

Qin

Liang

et al. 2012

Anal. Chem.

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Polymeric membrane ion-selective electrodes (ISEs) have become attractive tools for trace-level environmental and biological measurements. However, applications of such ISEs are often limited to measurements with low levels of electrolyte background. This paper describes an asymmetric membrane rotating ISE configuration for trace-level potentiometric detection with a high-interfering background. The membrane electrode is conditioned in a solution of interfering ions (e.g., Na + ) so that no primary ions exist in the ISE membrane, thus avoiding the ion-exchange effect induced by high levels of interfering ones in the sample. When the electrode is in contact with the primary ions, the interfering ions in the membrane surface can be partially displaced by the primary ions due to the favorable ion−ligand interaction with the ionophore in the membrane, thus causing a steady-state potential response. By using the asymmetric membrane with an ion exchanger loaded on the membrane surface, the diffusion of the primary ions from the organic boundary layer into the bulk of the membrane can be effectively blocked; on the other hand, rotation of the membrane electrode dramatically reduces the diffusion layer thickness of the aqueous phase and significantly promotes the mass transfer of the primary ions to the sample−membrane interface. The induced accumulation of the primary ions in the membrane boundary layer largely enhances the nonequilibrium potential response. By using copper as a model, the new concept offers a subnanomolar detection limit for potentiometric measurements of heavy metals with a high electrolyte background of 0.5 M NaCl. S ince the discovery of lowering the detection limit of ionselective electrodes (ISEs) in 1997, 1 spectacular progress in the development and application of potentiometric sensors has been made, and the new wave of ISEs has already arrived. 2−4The lower detection limit of polymeric membrane ISEs has been improved by a factor of up to 10 6 , while the discrimination of interfering ions has even improved by a factor up to 10 10 . 5Nowadays, ISEs have evolved to be a promising technique for trace-level environmental and biological measurements. 6−9However, it should be noted that most of the applications of polymeric membrane-based ISEs developed so far are limited to measurements with low levels of electrolyte background, typically for drinking water 10,11 or well-controlled solutions. 8,9Very few polymeric membrane ISEs have been reported for potentiometric detection with a high-interfering background. The ISE with an optimal internal solution buffered for primary ions has been used for determination of low levels of calcium with an intracellular fluid background containing high concentrations of K + , Na + , and Mg 2+ . 12 To avoid super-or sub-Nernstian behavior, tedious optimization of the inner solution is required for each sample. By coupling the microliter potentiometric detection to an efficient online electrochemical accumulation step, solid-contact ion-selective microele...

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Section: +mentioning

confidence: 99%

Trace-Level Potentiometric Detection in the Presence of a High Electrolyte Background

Qin

Liang

et al. 2012

Anal. Chem.

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“…The experiments were performed in custom-made electrochemical transport cells as described previously [3]. Briefly, the membrane separated two 20 mL volume compartments.…”

Section: Experimental Methods For Ca and Cpmentioning

confidence: 99%

“…More recently, it was shown that CP can be used in the same way. However, CP has both theoretical and experimental advantages [3,6]: i) the constant current assumption is only strictly true in CP experiments; ii) it is usually easier to determine the transition times from the CP voltage-time transients than from the CA current -time curves.…”

Section: Introductionmentioning

confidence: 99%

“…More recently, it has been shown that breakpoints in the CA or CP transients of ion-selective membranes can emerge either when the free ionophore (L) or the ion-ionophore complex (IL nþ k Þconcentration reaches zero at one of the membrane boundaries [3,6]. In a specific experiment, the relative concentrations and the diffusion coefficients of the ionophore and the ion-ionophore complex determine which species concentration will drop first to zero at one of the membrane boundaries and cause the breakpoint in the CA or CP transients.…”

Section: Introductionmentioning

confidence: 99%

“…However, a variety of non-equilibrium techniques have been devised to probe membrane characteristics or alter membrane response. For example, chronoamperometric (CA) [1 -5] and chronopotentiometric (CP) [3,6] methods have been used to determine either the concentration or the diffusion coefficient of the free ionophore inside the membrane. Determination of the free ionophore concentration in membranes can be used to assess leaching of the ionophore or lipophilic anion from the membrane over time.…”

Section: Introductionmentioning

confidence: 99%

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Assessment of Ion‐Ionophore Complex Diffusion Coefficients in Solvent Polymeric Membranes

et al. 2009

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Chronoamperometric (CA) and chronopotentiometric (CP) transients have been used previously for the determination of the diffusion coefficients of free ionophores in ion-selective liquid membranes. In this work, the CA and CP transients are utilized to determine the diffusion coefficients of a variety of ion-ionophore complexes in these membranes. The conditions under which the ion-ionophore complex diffusion coefficients can be determined from the CA and CP transients are discussed. For most ionophores, the ion-ionophore complex diffusion coefficients were found to be slightly smaller or similar to the previously calculated free ionophore diffusion coefficients. However, for a couple of ionophores, the ion-ionophore complex diffusion coefficients were found to be significantly smaller than expected. Significant ion-pair formation in the membranes can explain this disparity.

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Voltammetric Determination of Diffusion Coefficients in Polymer Membranes: Guidelines to Minimize Errors

et al. 2017

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Diffusion coefficients are important in the design, optimization, and selection of membranes used in many applications including chemical and biosensors. Since the diffusion‐controlled transport of the analyte and interfering ions and molecules through polymer membranes may affect the rate of response, detection limit, selectivity, lifetime, etc. of chemical and biosensors, having a rapid and accurate method for the determination of diffusion coefficients of different compounds in a variety of membranes is uniquely important. In our contribution, we present a simple protocol for the rapid determination of the diffusion coefficients of electrochemically active analytes by linear sweep voltammetry. The expected errors in the estimated coefficients have been analyzed through modeling and the correlation between the magnitude of the unknown diffusion coefficients and the method's related maximum error is presented as a contour plot for different working electrode dimensions. It is also shown that our analysis protocol can be used to estimate the diffusion coefficient in complex membrane matrices and non‐ideal experimental conditions with a maximum systematic error of 14 % even without any experimental parameter optimization.

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Chronopotentiometric method for the assessment of ionophore diffusion coefficients in solvent polymeric membranes

Cited by 24 publications

References 47 publications

Trace-Level Potentiometric Detection in the Presence of a High Electrolyte Background

Trace-Level Potentiometric Detection in the Presence of a High Electrolyte Background

Assessment of Ion‐Ionophore Complex Diffusion Coefficients in Solvent Polymeric Membranes

Voltammetric Determination of Diffusion Coefficients in Polymer Membranes: Guidelines to Minimize Errors

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