Asymmetrical flow field flow fractionation methods to characterize submicron particles: application to carbon-based aggregates and nanoplastics

In the last 10 years, asymmetrical flow field flow fractionation (AF4) has been one of the most promising approaches to characterize colloidal particles. Nevertheless, despite its potentialities, it is still considered a complex technique to set up, and the theory is difficult to apply for the characterization of complex samples containing submicron particles and nanoparticles. In the present work, we developed and propose a simple analytical strategy to rapidly determine the presence of several submicron populations in an unknown sample with one programmed AF4 method. To illustrate this method, we analyzed polystyrene particles and fullerene aggregates of size covering the whole colloidal size distribution. A global and fast AF4 method (method O) allowed us to screen the presence of particles with size ranging from 1 to 800 nm. By examination of the fractionating power F (d), as proposed in the literature, convenient fractionation resolution was obtained for size ranging from 10 to 400 nm. The global F (d) values, as well as the steric inversion diameter, for the whole colloidal size distribution correspond to the predicted values obtained by model studies. On the basis of this method and without the channel components or mobile phase composition being changed, four isocratic subfraction methods were performed to achieve further high-resolution separation as a function of different size classes: 10-100 nm, 100-200 nm, 200-450 nm, and 450-800 nm in diameter. Finally, all the methods developed were applied in characterization of nanoplastics, which has received great attention in recent years.