AF4-MALS Nanoparticle Fractionation and Analysis System

What is the AF4-MALS Nanoparticle Fractionation and Analysis System?

A system combining asymmetric flow field-flow fractionation with multi-angle light scattering, UV and refractive index detection. It first separates particles or macromolecules by hydrodynamic size, then measures size, molar mass and concentration for each fraction, resolving mixtures, aggregates and polydisperse samples.

Overview

In asymmetric flow field-flow fractionation (AF4), sample is injected into a thin channel with a semi-permeable membrane at the accumulation wall. A cross-flow pushes particles toward the wall while diffusion pushes them back; smaller particles with higher diffusion sit higher in the parabolic channel flow and elute first. The eluent passes through an in-line multi-angle light scattering detector, UV detector and differential refractive index detector. MALS provides root-mean-square radius and molar mass, and dynamic light scattering can be added for hydrodynamic radius. Unlike column chromatography, there is no stationary phase, so shear and adsorption are minimised, which helps with fragile aggregates, vesicles and lipid nanoparticles. Typical range is 1 nm to 1 µm. Method development of cross-flow profile, membrane cut-off and carrier composition takes time.

How does it work?

Nanoparticle tracking analysis illuminates a dilute suspension with a laser sheet and records the scattered light of individual particles with a camera; software follows each track and derives a diffusion coefficient, converted to hydrodynamic diameter with the Stokes–Einstein equation, and counts particles per millilitre in a known volume. Resistive pulse sensing passes particles through a nanopore in an electrolyte; each particle transiently reduces ionic current in proportion to its volume, giving size and concentration. Field-flow fractionation separates particles in a thin channel by diffusion under a cross-flow before in-line light scattering detectors measure size and molar mass. Nano flow cytometers use hydrodynamic focusing and sensitive side-scatter and fluorescence detection to phenotype single particles. Sample dilution and calibration with reference beads are essential.

What are the key features?

• Asymmetric flow channel with replaceable membranes of several cut-offs
• Multi-angle light scattering for size and molar mass per fraction
• In-line UV and differential refractive index detectors
• Programmable cross-flow gradients for wide size ranges
• Optional dynamic light scattering detector
• Gentle separation without stationary phase, limiting adsorption

What are the technical specifications?

A typical af4-mals nanoparticle fractionation and analysis system configuration offers size range of 1 nm–1 µm, separation principle of Asymmetric flow field-flow fractionation, MALS detector of 18 angles, 659 nm laser, cross-flow range of 0–5 mL/min programmable, channel flow of 0.1–5 mL/min and membrane cut-off of 1–30 kDa regenerated cellulose or PES. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The AF4-MALS Nanoparticle Fractionation and Analysis System is used in lipid nanoparticle and liposome fractionation, virus-like particle and AAV aggregate analysis, polymer and nanoparticle molar mass distribution, protein aggregate resolution and environmental and food nanomaterials. Across the wider Nanoparticle Analyzers class, laboratories also deploy it for liposome and lipid nanoparticle characterisation, extracellular vesicle and exosome research and viral vector and vaccine particle counting.

Which standards and certifications apply?

Relevant standards and methods include ISO 19430, ISO 13322-1, ISO 22412, ISO/TS 21362, ASTM E2834, ISO 21363 and GB/T 19627. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Nanoparticle measurements are very sensitive to sample preparation. Use particle-free, filtered diluents and clean glassware, and dilute to the instrument's optimum concentration window. Dust and bubbles produce false counts. Verify size and concentration with certified polystyrene or silica nanosphere standards at start-up and after changes of settings, and report camera level, detection threshold, temperature and number of tracks, because these parameters change results. Keep laser optics, flow cells and nanopores clean and stored as advised. Install in a stable, temperature-controlled room. Regulated work needs IQ/OQ/PQ, locked methods and audit trails.

How do I select the right AF4-MALS Nanoparticle Fractionation and Analysis System?

Choose AF4-MALS when mixtures or aggregates must be resolved and characterised by molar mass and size, where a column would shear or adsorb the sample. Specify size range, sample type, carrier composition, detectors (UV, dRI, DLS), injection volume and validation requirements. Simple monomodal samples do not need the added method development.

How does it compare with other Nanoparticle Analyzers variants?

Decide what the measurement must deliver: concentration and size distribution of polydisperse samples, fluorescent subpopulation counts, high-resolution separation of mixtures, or single-particle phenotype. Nanoparticle tracking suits 30 to 1000 nm particles at 10⁷ to 10⁹ particles/mL. Resistive pulse sensing gives high-resolution, refractive-index-independent size for conductive dispersions. Field-flow fractionation coupled to multi-angle light scattering resolves mixtures and aggregates. Nano flow cytometry is preferred when labelling and marker analysis are needed. Check detection limit versus your smallest particle, required dynamic range, sample volume, and optical property dependence. Consider whether applicable guidance such as ISO 19430 and regulatory expectations for liposomes or vaccines apply, and who will operate and maintain the system.