A Bipartite Expression for the Transient Amperometric Current at a Membrane Covered Planar Electrode to Characterize Solute Diffusion Through the Membrane

Abstract

A simple bipartite expression for transient amperometric currents at a membrane covered planar electrode has been derived. This expression is uniquely applicable across the entire measurement time frame and enables a rapid, comprehensive dynamic simulation of solute diffusion through the membrane barrier. The effective diffusion coefficient through the membrane for an electrochemically active solute can be readily obtained by employing the simple curve fitting routine. The diffusion coefficients for 4-acetaminophenol through 0.05 and 0.025 mm pore diameter mixed cellulose esters membranes were determined to be 1.96 Â 10 À7 and 1.21 Â 10 À7 cm 2 /s, respectively. For catechol respective values were 1.55 Â 10 À7 and 1.15 Â 10 À7 cm 2 /s. Diffusion coefficients were reduced following membrane exposure to bovine serum albumin and this change provided a functional counterpart to conventional structural measures of surface biofouling. The approach has relevance to both sensors and membrane separation systems in biomedicine, and has the potential to offer a rapid assessment of membrane surface biofouling.

Influence of nanopatterns on endothelial cell adhesion: Enhanced cell retention under shear stress

“…By solving Eq. (1) under the experimental condition of a time dependent sensor response to a step change in concentration, current response, I, is given by [27]:…”

“…Small molecule diffusivity through the collagen films was measured with or without seeding with the endothelial cells. The molecules selected (oxygen and 4-acetaminophenol) were readily detectable electrochemically and their diffusion to a polarized electrode surface readily tracked [27]. Furthermore, cell viability, cell proliferation and cell adhesion strength during shear stress caused by medium laminar flow over the films was determined.…”

Bipartite expressions for amperometric currents of recessed, membrane covered planar and hanging mercury drop electrodes

“…We have fitted simulated transient currents under initial condition 2 and boundary condition 1 to the experimental data by stretching and shifting the experimental current curve vertically and stretching and shifting the calculated current curve horizontally [19]. Similarly, for other initial and boundary conditions, the experimental current curve can be stretched and shifted vertically and a simulated curve stretched and shifted horizontally for a best fit and therefore D value.…”

“…(4) or (5) is 1.7 Â 10 À4 , which well satisfies practical applications. These equations were used to determine the diffusion coefficients of acetaminophen and catechol through a mixed cellulose acetate membrane [19] and to analyse oxygen diffusion through a hydrogel layer [20] by a simulation, where the initial value for diffusion coefficient was obtained from the time t 0.5 when transient electrode current reached half steady state:…”

Effective diffusion coefficient determination within cylindrical granules of adsorbents using a direct simulation method

“…The release of the water-soluble antibiotics from a coated cylinder followed Fick's Second Law for a simple slab and effective diffusion coefficients were obtained by fitting the simulated to experimental release curves [17]. The above mentioned parameter for acetaminophen at a membrane was determined by fitting simulated concentration gradients to experimental amperometric currents [18].…”