Multi-angle light scattering (MALS) is primarily used to determine molecular weight, size- and shape-related parameters of macromolecules or nanoparticles as they elute from a separation device. In batch (unfractionated) mode, MALS provides the weight-average molecular weight <M>w and the z-average mean square radius <Rg 2>z. The DAWN® HELEOS® II is particularly well suited for these tasks owing to its flow cell design, holding a mere ~67 µl and readily connecting to a fluid line through HPLC-type fittings. This very same design can be used profitably to study a sample evolving in time, such as a polymerization or degradation reaction, by injecting a sample into the flow cell with a stopped-flow apparatus.


