Both Multi-Angle Light Scattering (MALS) and Dynamic Light Scattering (DLS) provide non-perturbative, solution-based size measurements based on absolute analysis, independently of calibration standards. These techniques are complementary and orthogonal, analyzing different properties of the scattered light.

Size by Multi-Angle Light Scatteting (MALS)

MALS examines the angular dependence of the time-averaged scattering intensity to determine the mass-averaged root mean square radius rg (a.k.a. 'radius of gyration') from 10 nm to several hundred nanometers, independent of shape, as described in Classical Light Scattering Theory.

If the sample conforms to specific shape models such as sphere, random coil or coated sphere then the radius or half-length can be determined from 10nm to as much as 600nm by the DAWN 8+ 8-angle MALS detector.

Size distribution by On-line (fractionated) Multi-Angle Light Scattering (SEC-MALS)

Coupling a MALS detector to a fractionation method such as Size Exclution chromatography (SEC-MALS) is the most common method for MALS characterization of size distributions of homogeneous or heterogeneous samples. MALS analysis provide the rms radius rg of the analyte at each elution volume, independently of retention time. Since the detection volume of the MALS flow cell is much smaller than a typical monomeric peak eluting from SEC or MALS provides accurate size distributions limited only by the separation technique.

SEC-MALS determine the size distribution of :

• Biopolymers
• PEGylated proteins and large protein complexes
• Synthetic polymers
• Liposomes or exosomes
• Large protein aggregates

Size by Dynamic Light Scatteting (DLS)

Dynamic Light Scattering (DLS) utilizes the time-dependent fluctuations of scattered intensity, which arise from Brownian motion, in order to determine the diffusion constant. The hydrodynamic radius Rh is then calculated directly. Unlike MALS, DLS does not usually require accurate knowledge of sample concentration but does need accurate values of solvent viscosity and temperature.

Size distribution by On-line (fractionated) Dynamic Light Scattering (SEC-DLS)

Dynamic Light Scattering (DLS) may be measured on-line in SEC by integrating a WhyattQuels module into a DAWN MALS detector, or by transferring light collected in the MALS detector via optical fiber to a batch DLS detector. Depending on the collection angle, laser wavelength and flow rate, online DLS can analyze R from 1nm up to ~250nm.