A New Separation Metric for the Optimization of AF4 Separations of Polydispersed Nanomaterials

A.A. Galyean, W.N. Vreeland, J.J. Filliben, R.D. Holbrook, H.S. Weinberg
University of North Carolina at Chapel Hill, US

Keywords: nanomaterials, asymmetric flow field flow fractionation, AF4, separation, complex matrix, polydispersity, quasi-elastic light scattering, QELS, differential number fraction


The development of standardized and optimized methods to monitor the behavior of engineered nanomaterials (ENMs) in complex environments is considered a critical component in ENM risk assessment. Robust, rigorously optimized methods are currently lacking, in part because of matrix variability, sample polydispersity, and a lack of understanding how primary instrument factors affect method performance. To this end, a practical and effective separation method has been explored that optimizes asymmetric flow field flow fractionation (AF4) separation protocols with an online quasi-elastic light scattering (QELS) detector. An assessment metric to better interpret particle sizing data following separation of complex nanomaterial samples was identified using a hydrodynamic radius differential that determines relative separation protocol success. Using this metric, the AF4 separation of a complex sample can be optimized. Full optimization is realized when a higher retention separation does not produce a smaller measured radius differential that is larger than the associated uncertainty.