Asymmetric Flow Field-Flow Fractionation (AF4) Systems

Asymmetric Flow Field-Flow Fractionation (AF4) is a column-free separation technique used to characterize particles, macromolecules, and aggregates in solution based on their hydrodynamic size. Unlike chromatography, AF4 uses a channel with a controlled cross-flow field rather than a stationary phase.

AF4 systems gently separate analytes ranging from a few nanometers to several micrometers — ideal for fragile biotherapeutic particles such as AAV vectors, mRNA-LNPs, and protein aggregates.

When coupled with detectors such as Multi-Angle Light Scattering (MALS), Dynamic Light Scattering (DLS), or UV/dRI, AF4 provides absolute molar mass, size distribution, and aggregation profiles across a broad dynamic range.

Key Applications
Determining AAV or LNP size distribution and aggregation state

Characterizing protein or mRNA nanoparticle formulations

Resolving empty and full capsid populations (orthogonal to AEX-HPLC or SV-AUC)

Assessing formulation stability without shear or adsorption artifacts

Advantages
Matrix-free, gentle separation (no stationary phase)

Broad dynamic range (1 nm–1 µm)

Compatible with multiple detectors (MALS, DLS, UV/dRI)

Orthogonal to chromatographic methods such as SEC or AEX