A method for determining the mutual diffusion coefficient of molecular solutes based on surface plasmon resonance sensing

An experimental method, combining surface plasmon resonance sensing and microfluidics, to determine the mutual diffusion coefficient of molecular solutes, as ethanol and bovine serum albumin, is presented. Representative refractive index variations of analyte samples over time, and associated dynamic solute concentration profiles, respectively, have been employed to access molecular transport parameters. From both, Fick’s diffusion length and Taylor’s pulse dispersion methods, solute and solvent mutual diffusion coefficients for diluted ethanol and concentrated protein aqueous solutions have been obtained. Additionally, the dynamic behavior and geometry effects of molecular transport have been exploited using finite element simulations for the 3-dimensional case and confirmed experimentally. The numerical simulation also addresses the influence of temperature effects.