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Field-Flow Fractionation
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
FFF with multi-angle light scattering (MALS) detection is popular for the analysis of macromolecules (Andersson et al., 2001b). The combination is also used for colloids in the size range between 20 and 300 nm. In MALS, the angular distribution of the light scattering intensity yields information on molar mass, and if the particle diameter is between 20 and 300 nm, information on size as well. Without the separation step, MALS yields only an average value of the size or molar mass of a sample, with no information on the breadth and modality of the distribution. On the other hand, the determination of size or molar mass by FFF without MALS is complicated by the influence of parameters that govern the interaction of the analyte with the field. By combining the two techniques, size and/or molar mass information is obtained on hundreds of elution slices as they exit the FFF channel, leading to highly precise information on molar mass or particle size distributions.
Biophysical and Biochemical Characterization of Peptide, Protein, and Bioconjugate Products
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
Tapan K. Das, James A. Carroll
Mass measurement studies can be performed using LS detectors that are commercially available in various configurations such as low-angle light scattering (LALS), right-angle light scattering, and MALS [136]. These LS detectors need to be coupled with a concentration measurement detector (absorbance, RI, or both) in order to extract molecular mass of the fractionated species. MALS measurements are frequently used in the development of protein pharmaceuticals, in which a series of detectors are placed around the flow cell at various angles to collect angular dependence information, for example, to aid determination of molecular weight of different species separated via SEC or other techniques. When the angle increases, intramolecular interference results in a reduction of LS intensity for molecules larger than approximately 10 nm (and more prominently for molecule sizes of greater than 1/20th of the incident beam wavelength). In addition to deriving molecular mass using a MALS detector, the angular dependence of the scattering intensity can provide size (radius of gyration) information of the separated aggregate species. Commercially available MALS detectors use an array of detectors placed in a range of angles approximately from low (20°) to high (160°). Data on molecular size can also be obtained in the form of root mean square radius, also referred to as radius of gyration. However, if the shape of the separated aggregates is not known, it is difficult to accurately estimate the size. Angular dependence is diminished when the size (diameter) of protein monomer or aggregate is less than approximately 10 nm (with incident laser light wavelength in the visible range), and size (diameter) can no longer be determined accurately. Molecular mass determined by online MALS ranges from several hundred Daltons to millions of Daltons and higher. But practically when a mixture of species is fractionated using separation techniques (such as SE-HPLC and AF4), some of the components can be present in small quantity. In such cases, determining their molecular mass (and size) by MALS can be very challenging due to a low signal-to-noise ratio. In either MALS or LALS mode, an integrated unit of several detectors (e.g., absorbance, RI, LS) is commercially available that provides a convenient option to researchers to get a wealth of data from a single sample injection.
Colloidal lead in drinking water: Formation, occurrence, and characterization
Published in Critical Reviews in Environmental Science and Technology, 2023
Javier A. Locsin, Kalli M. Hood, Evelyne Doré, Benjamin F. Trueman, Graham A. Gagnon
Static, multi-angle light scattering (MALS) addresses the single measurement angle limitations of DLS by simultaneously measuring the intensity of scattered light at different scattering angles. This technique can provide users with information on the shape and structure of particles. There are some limitations in using MALS, particularly in environmental samples where neither the analyte concentration, the molecular weight, nor the refractive index increment are known (Kammer et al., 2005).