Chromatographic Separation of Gold Nanoparticles: Fractionation, Characterization, and Comparison with Polymers

Size exclusion chromatography (SEC) is the standard technique for the characterization of molecular weight distributions of polymers in aqueous and organic solvents. The separation mechanism is based on the size-dependent diffusion of compounds into the porous network of the stationary phase, ideally suppressing attractive interactions with the column material. In recent publications, we extended the applicability of SEC to the classification and characterization of different nanoparticle systems. Since the chromatography of nanoparticles is still a novel field of application, we systematically investigate in this article the elution behavior and separation performance of different gold nanoparticle (AuNP) sizes as a function of various process parameters including column length, pore size, flow rate, and temperature. Moreover, we compare the elution characteristics of AuNPs with those of hydrophilic and hydrophobic polymers and find similarities between both systems. By a detailed study of peak resolutions, we provide general guidelines on achievable separations and optimization strategies for improved column performance. Additionally, we investigate the band broadening of individual AuNP dispersions by van Deemter curves and extract effective pore diffusion coefficients, which decrease drastically for AuNP sizes approaching the pore diameter of the stationary phase. With our study, we demonstrate that nanoparticles and polymers show similar retention behavior in SEC separations, which enables fast method transfer of well-known dependencies in polymer separations to nanoparticulate systems.