Theoretical principles of field-flow fractionation and SPLITT fractionation

Architecture of soil microaggregates: Advanced methodologies to explore properties and functions

“…While the largest aggregates can be gently isolated by sieving and crushing, small microaggregates and particles (<20 µm) need more advanced techniques for size separation, such as the gravitational split‐flow thin‐cell (SPLITT) technique. This technique is applied for continuous and preparative size fractionation (Williams, 2022), and has been used to separate and isolate size fractions of both, marine sediments (Dickens et al., 2006; Keil et al., 1994; Moon et al., 2005) and soils (e.g., Kiem et al., 2002). SPLITT utilizes gravity to differentiate size fractions in a size range of 1–300 µm according to particle settling velocity (Giddings, 1985; Springston et al., 1987).…”

“…This results in different retention time of particles according either directly to their hydrodynamic diameters or to other properties such as mass and electrophoretic mobility, which are also possibly related to the hydrodynamic diameter (Kowalkowski et al., 2006; Ornthai et al., 2016). Accordingly, particles of different sizes will be eluted from the channel at distinct time yielding specific elution profiles, the so‐called fractogram (Schimpf et al., 2000; Williams, 2022). Asymmetrical‐flow FFF (AF 4 ), relying on a crossflow‐based field, has been frequently applied to fractionate and characterize natural colloids and nanoparticles in soils and streams (Baalousha et al., 2006; Missong et al., 2018; Wang et al., 2020) and can be coupled to DLS or multiangle light scattering to produce size‐profiles of particles.…”