Salt Bridges of Porous Glass and Ion Exchange Membranes

Carson, W.N.; Michelson, C. E.; Koyama, K.

doi:10.1021/ac60099a052

Cited by 20 publications

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“…A common approach for satisfying both of these criteria is based on the separation of the reference and sample solutions by a porous material filled with an electrolyte (which is usually the same electrolyte as used in the reference solution) . Porous glass frits with a high density of nanopores (4.0 nm average pore size) were made commercially available under the brand name Vycor and were first recommended for use in reference electrodes in 1955 . Nanoporous Vycor offered the advantage of restricting excessive mass transfer of reference and sample components across a stable low-resistance junction. , Since then, Vycor has been widely used for the fabrication of both in-house-prepared and commercial reference electrodes. − Unfortunately, until very recently, there have been no systematic studies investigating the performance and limitations of reference electrodes with nanoporous frits. , …”

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confidence: 99%

“…Porous glass frits with a high density of nanopores (4.0 nm average pore size) were made commercially available under the brand name Vycor and were first recommended for use in reference electrodes in 1955 . Nanoporous Vycor offered the advantage of restricting excessive mass transfer of reference and sample components across a stable low-resistance junction. , Since then, Vycor has been widely used for the fabrication of both in-house-prepared and commercial reference electrodes. − Unfortunately, until very recently, there have been no systematic studies investigating the performance and limitations of reference electrodes with nanoporous frits. , …”

mentioning

confidence: 99%

“…7 Nanoporous Vycor offered the advantage of restricting excessive mass transfer of reference and sample components across a stable low-resistance junction. 4,7 Since then, Vycor has been widely used for the fabrication of both in-house-prepared and commercial reference electrodes. 4−7 Unfortunately, until very recently, there have been no systematic studies investigating the performance and limitations of reference electrodes with nanoporous frits.…”

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Avoiding Errors in Electrochemical Measurements: Effect of Frit Material on the Performance of Reference Electrodes with Porous Frit Junctions

et al. 2016

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In many commercially available and in-house-prepared reference electrodes, nanoporous glass frits (often of the brand named Vycor) contain the electrolyte solution that forms a salt bridge between the sample and the reference solution. Recently, we showed that in samples with low ionic strength, the half-cell potentials of reference electrodes comprising nanoporous Vycor frits are affected by the sample and can shift in response to the sample composition by more than 50 mV (which can cause up to 900% error in potentiometric measurements). It was confirmed that the large potential variations result from electrostatic screening of ion transfer through the frit due to the negatively charged surfaces of the glass nanopores. Since the commercial production of porous Vycor glass was recently discontinued, new materials have been used lately as porous frits in commercially available reference electrodes, namely frits made of Teflon, polyethylene, or one of two porous glasses sold under the brand names CoralPor and Electro-porous KT. In this work, we studied the effect of the frit characteristics on the performance of reference electrodes, and show that the unwanted changes in the reference potential are not unique to electrodes with Vycor frits. Increasing the pore size in the glass frits from the <10 nm into the 1 μm range or switching to polymeric frits with pores in the 1 to 10 μm range nearly eliminates the potential variations caused by electrostatic screening of ion transport through the frit pores. Unfortunately, bigger frit pores result in larger flow rates of the reference solution through the pores, which can result in the contamination of test solutions.

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Avoiding Errors in Electrochemical Measurements: Effect of Frit Material on the Performance of Reference Electrodes with Porous Frit Junctions

et al. 2016

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“…Frit materials can vary, from glass (available under brand names such as CoralPor, Electroporous KT, and Vycor) to polymeric materials (such as polyethylene or Teflon). Reference electrodes with nanoporous glass frits in particular have been used frequently in many types of electrochemical experiments for several decades, 20 but only in 2013 were the limitations of these devices discussed systematically. 18,21 Notably, the small pore sizes (commonly 4-10 nm pores with ~4 µL/h flow rates ) used in frit-based liquid salt bridges can lead to charge screening, resulting in electrostatic forces acting on electrolyte ions caused by negatively charged surface groups on the glass surface.…”

Section: Flow-restricted Liquid Salt Bridgesmentioning

confidence: 99%

Recent progress in the development of improved reference electrodes for electrochemistry

et al. 2022

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A vital part of almost every experimental electrochemical set up is the reference electrode. As the development of working and indicator electrodes progresses to sensors with greater long-term stability and efficiency, it is important for reference electrodes to keep up with that progress. In this review, the deficiencies of commonly used reference electrodes are discussed, and recent work in the development of new reference electrode designs for more stable and reliable electrochemical experiments is highlighted. This encompasses work with salt-bridge reference electrodes comprising nanoporous and capillary junctions, solid-contact reference electrodes, and ionic liquid-based reference electrodes.

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“…They often comprise of a porous frit filled with an electrolyte solution or ionic liquid, − where the porous material or ionic liquid forms a barrier between the sample and the inner filling solution of the reference electrode, minimizing mixing of these two solutions while maintaining electrical contact . Mesoporous glass frits with pore sizes of ∼10 nm and, more recently, macroporous polymers with pore sizes of ∼1 μm are often used for this purpose. − However, the use of the former can introduce errors in many measurements due to electrostatic screening caused by the surface charge density on the silica pore walls, while the latter are not suitable for long-term measurements, as the larger pore sizes allow for more rapid cross contamination of the sample and reference solution. , To address these limitations, we developed an alternative frit material that reduces the dependence of the reference potential on the sample while still maintaining low flow rates. Specifically, we prepared a new polymeric monolith with pores sizes in the 10 nm range and uncharged, hydrophilic pore surfaces.…”

Section: Introductionmentioning

confidence: 99%

Functionalized Mesoporous Polymers with Enhanced Performance as Reference Electrode Frits

Anderson

Saba

Loomis

et al. 2017

ACS Appl. Nano Mater.

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Mesoporous glasses (∼10 nm pores) and macroporous polymers (∼1 μm pores) are often used as frits in the fabrication of aqueous reference electrodes. These frits function as salt bridges that allow for electrical contact between the sample and reference solutions while slowing cross contamination of the two solutions. Unfortunately, mesoporous glass and macroporous polymer frits used for these purposes inherently result in sample-dependent potentials or in rapid cross contamination of the sample and reference solutions, respectively. To address these issues, we synthesized mesoporous polymer frits, with much smaller pore sizes (∼10 nm) and electrically neutral hydrophilic pore walls. These monoliths were prepared from a bicontinuous, microphase-separated, and cross-linked block polymer precursor, that is, poly(lactide)-b-poly(isoprene)-b-poly(styrene-co-divinylbenzene), PLA-b-PI-b-P(S-co-DVB). The PLA serves as a selectively etchable sacrificial block, the PI provides latent reactive sites on the pore walls, and the P(S-co-DVB) forms the mechanically robust matrix. Subjecting the PI repeat units in the monoliths to epoxidation and subsequent hydrolysis reactions renders the pore walls hydrophilic and uncharged, permitting the use of the polymer as a porous frit material in reference electrodes with aqueous electrolyte solutions. This monolith chemistry allows for reference electrodes with reduced flow rates that approach those of mesoporous glass frits and thus mitigated cross contamination. Moreover, reference electrode potential variations are reduced across a large range of electrolyte concentrations.

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Salt Bridges of Porous Glass and Ion Exchange Membranes

Cited by 20 publications

References 0 publications

Avoiding Errors in Electrochemical Measurements: Effect of Frit Material on the Performance of Reference Electrodes with Porous Frit Junctions

Avoiding Errors in Electrochemical Measurements: Effect of Frit Material on the Performance of Reference Electrodes with Porous Frit Junctions

Recent progress in the development of improved reference electrodes for electrochemistry

Functionalized Mesoporous Polymers with Enhanced Performance as Reference Electrode Frits

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