Charge & Zeta Potential
Commonly associated with the stability of suspensions, zeta potential (ζ) / molecular charge is also useful in assessing chemical modifications to biomolecules such as polysaccharides or IgG. In order to be relevant the charge must be measured in the solvent or formulation buffer of interest. That's why the Mobius® offers solutions for all solutions – volatile organics or highly conductive aqueous, as well as the more usual low-conductivity aqueous.
Both molecular charge and zeta potential are calculated from three primary measurements: electrophoretic mobility µ, hydrodynamic radius Rh and solvent conductivity σ. Light scattering determines electrophoretic mobility via Massively Parallel Phase Analysis Light Scattering (MP-PALS), and hydrodynamic radius via Dynamic Light Scattering (DLS). Only the Mobius plus integrated WyattQELS DLS module offers simultaneous measurement of µ and Rh. Conductivity is measured in the MP-PALS cell as well. Please see Electrophoretic Light Scattering Theory for more details.
For more detailed information on size and zeta potential, the Mobility system implements electrical/asymmetric-flow field flow fractionation (EAF4). EAF4 provides high-resolution,simultaneous distributions of particle size and zeta potential that are just not possible in a batch (unfractionated) measurement.
- Optimizing stability of colloidal solutions such as quantum dots, liposomes, and monoclonal antibodies
- Indication of chemical modifications that add or subtract charged residues (e.g., drug molecules in antibody-drug conjugates or super-sulfated heparin)