Steady-State and Nonsteady-State Transport through Membranes Using Rotating-Disk Electrode Polarography: Description and Properties of a Rapid Response New Technique

Chien, Yie W.; Olson, Carl R.; Sokoloski, Theodore D.

doi:10.1002/jps.2600620316

Cited by 21 publications

(5 citation statements)

References 21 publications

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“…This effect becomes more apparent with decreasing membrane permeability as shown in Figure 2. Thus, a possible explanation might be afforded for the observation previously reported in the literature (8) of the effect of rotation rate on current density: slight inaccuracy in the measurement of diffusion current might lead to the incorrect conclusion that the current density is linear with rotation rate at low rotation rates but proportionally lower than the Levich current.…”

Section: Theoreticalmentioning

confidence: 95%

“…More recently, Flegg (3) and Richmond (4) developed enzymatic methods for analyzing cholesterol utilizing cholesterol oxidase isolated from soil bacteria. Since that time, many enzymatic methods have appeared in the literature (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). All these enzymatic cholesterol assays were claimed to be more specific, sensitive, precise, and simple than the direct chemical ones.…”

Section: Electrode Designmentioning

confidence: 99%

“…A variety of analytical detection methods have been used for the enzymatic methods. These include spectrophotometry (5)(6)(7)(8)(9)(10)(11)(12), fluorometry (13), potentiometry (17), and amperometry (14-16). The enzymatic spectrophotometric methods seemed to have some problems with bilirubin and ascorbic acid interferences, and most of the enzymatic procedures required calibration with cholesterol standards which sometimes have questionable reliability.…”

Section: Electrode Designmentioning

confidence: 99%

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Membrane-covered, rotated disk electrode

Gough¹,

Leypoldt²

1979

Anal. Chem.

228

111

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Section: Theoreticalmentioning

confidence: 95%

Section: Electrode Designmentioning

confidence: 99%

Section: Electrode Designmentioning

confidence: 99%

See 1 more Smart Citation

Membrane-covered, rotated disk electrode

Gough¹,

Leypoldt²

1979

Anal. Chem.

228

111

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“…rotated disc electrode has been previously used by other investigators in conjunction with a transient method to characterize transport parameters i n membranes. Chien, Olson. and Sokoloski (1973) used a carbon rotated disc electrode covered by a Millipore VC niembraiie to study the transport of p-nitrophenol.…”

Section: Introductionmentioning

confidence: 99%

A novel rotated disc electrode and time lag method for characterizing mass transport in liquid‐membrane systems

Gough¹,

Leypoldt²

1980

AIChE Journal

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A time lag method is described for use with a membrane-covered, rotated disc electrode that allows determination of the partitioning and diffusivity of small molecules in hydrophilic gel membranes Polymeric membranes have found many applications in biomedical and industrial technology. Many separation processes such as reverse osmosis, hemodialysis, filtration, and blood oxygenation are based on membranes. There is a need to accurately characterize the transport of solutes in these membranes as a basis for design of more effective processes. If the membrane can be approximated as a homogeneous phase containing a linear distribution of solute, a parameter that describes diffusive transport of the solute within the membrane is membrane permeability, P,, given by:where a is the partition coefficient, D,, is the diffusion coefficient for the solute within the membrane, and 6, is the membrane thickness.In this formulation, membrane permeability depends on the product of two physical parameters, a and D,, which must be measured independently and represent different mechanisms of transport control by the membrane. Thc partition cocfficicnt is the equilibrium ratio of solute concentration in the membrane to that in the external phase, and can have an effect even in the absence of net transport through the membrane. The partitioning effect can be dominant where processes occur in the membrane that are a function of the local concentration, such as absorption or chemical reaction of the solute in immobilized enzyme systems (Filippusson and Hornby, 1970;Engasser and Horvath, 1976). Conversely, the diffusion coefficient is a measure of the resistance to transport through the membrane once the solute has already entered and exited the membrane phase. If instantaneous equilibria across the membrane-solution interface can be assumed, D , alone is the important transport parameter in the decay of transient phenomena in the membrane. Therefore, complete characterization, that could facilitate the design of new membranes, requires direct measurement of either Lyor CUD,6, P, = -D, in addition to P, and 6,.Accurate meaurement of the diffusion coefficient of small molecules within the membrane is complicated by transport in the layers of solution on either side of the membrane. In early studies, attempts were made to eliminate these concentration boundary layers by intensive stirring. However, it is now thought that complete elimination is impossible and that the effects of the solution layers must be taken into account (Smith et al., 1968; M a h e and Anderson, 1977). A quantitative measure of the significance of the solution boundary layer effects in the measurement of membrane permeability is the mass transfer Biot number (Eckert and Drake, 1972): Bi = P,/P, where P, is the permeability o r mass transfer coefficient for the solution layer. For a membrane with gas phases on either side the Biot number is very large and hence boundary layer effects are negligible. However, for membranes in contact with liquid phases, the Biot num...

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“…For thinner films, they concluded that kinetic parameters were extractable directly from Tafel plots at low current densities after applying the Koutecký-Levich (K-L) correction for O 2 diffusion in the bulk electrolyte. Chien et al 7 were some of the first researchers who investigated mass transport through F1385 with SA values under comparable conditions to the work of Paulus et al 15 In employing Nafion caps, researchers often implicitly postulate a discrete Nafion film located over the catalyst layer and calculate a hypothetical cap thickness based on density and volume of ionomer used. These assumptions are unrealistic and only applicable when present over a smooth non-porous bulk material like poly-Pt; for a porous Pt/C catalyst layer, the aliquot of Nafion used to form a cap penetrates and distributes itself over the depth of the catalyst layer.…”

mentioning

confidence: 99%

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique

Shinozaki

Zack

Pylypenko

et al. 2015

J. Electrochem. Soc.

245

191

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Platinum electrocatalysts supported on high surface area and Vulcan carbon blacks (Pt/HSC, Pt/V) were characterized in rotating disk electrode (RDE) setups for electrochemical area (ECA) and oxygen reduction reaction (ORR) area specific activity (SA) and mass specific activity (MA) at 0.9 V. Films fabricated using several ink formulations and film-drying techniques were characterized for a statistically significant number of independent samples. The highest quality Pt/HSC films exhibited MA 870 ± 91 mA/mg Pt and SA 864 ± 56 μA/cm 2 Pt while Pt/V had MA 706 ± 42 mA/mg Pt and SA 1120 ± 70 μA/cm 2 Pt when measured in 0.1 M HClO 4 , 20 mV/s, 100 kPa O 2 and 23 ± 2 • C. An enhancement factor of 2.8 in the measured SA was observable on eliminating Nafion ionomer and employing extremely thin, uniform films (∼4.5 μg/cm 2 Pt ) of Pt/HSC. The ECA for Pt/HSC (99 ± 7 m 2 /g Pt ) and Pt/V (65 ± 5 m 2 /g Pt ) were statistically invariant and insensitive to film uniformity/thickness/fabrication technique; accordingly, enhancements in MA are wholly attributable to increases in SA. Impedance measurements coupled with scanning electron microscopy were used to de-convolute the losses within the catalyst layer and ascribed to the catalyst layer resistance, oxygen diffusion, and sulfonate anion adsorption/blocking. The ramifications of these results for proton exchange membrane fuel cells have also been examined.

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Steady-State and Nonsteady-State Transport through Membranes Using Rotating-Disk Electrode Polarography: Description and Properties of a Rapid Response New Technique

Cited by 21 publications

References 21 publications

Membrane-covered, rotated disk electrode

Membrane-covered, rotated disk electrode

A novel rotated disc electrode and time lag method for characterizing mass transport in liquid‐membrane systems

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique

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