The dissolution products from engineered nanoparticles (NPs) are often toxic to aquatic organisms, yet accurately separating these two components is not a trivial endeavor.   Physical and chemical processes such as sorption, thermodynamic equilibrium, and counter ion concentrations can hinder accurate dissolution product measurements.  In this work, we demonstrate that the Donnan Membrane Technique (DMT) is a very suitable and robust technique for quantifying free ion concentrations in NP solutions.  The DMT uses a cation exchange membrane that acts as a barrier to NP transport, thus promoting only ionic transport to the acceptor solution while maintaining chemical equilibrium in the donor solution.  Using citrate-capped Ag NPs, we will compare the DMT with other size separation techniques, such as ultracentrifugation and membrane filtration.

Donnan membrane technique: Separating nanoparticles from ions

244th National Meeting (2012)

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