HDR-Multifit
HDR-MULTIFIT – Analysis of Turbidity Data and Determination of Particle Size Distributions
Presenter: Johannes Walter, FAU, Germany
DescriptionAnalytical Ultracentrifugation is perfectly suited for the analysis of particle size distributions (PSDs). However, the characterization of polydisperse PSDs is making high demands to any characterization technique. For sedimentation analysis, it has to be taken into account that the sedimentation rate scales with the particle size squared. To tackle such challenging systems, MWL gravitational sweep (GS) experiments at a fixed radial position were developed which are based on a continuously increasing rotor speed. GS experiments are of particular importance when studying polydisperse PSDs due the much larger dynamic range compared to traditional sedimentation velocity (SV) experiments. HDR-MULTIFIT can be used to analyze GS data and provides the ability to determine the optical properties of individual components in polydisperse mixtures and to relate this data to the hydrodynamic properties. For spherical NPs having well-defined refractive indices, high dynamic range (HDR) particle size analysis is possible. The analysis benefits from the direct fractionation of different particle sizes in the measurement cell during sedimentation, while the optimum signal to noise ratio for the whole PSD is achieved by automatically tuning the wavelength used for data evaluation. Besides GS experiments, it is demonstrated that HDR-MULTIFIT can also be used for the post-processing of sedimentation coefficient distributions from sedimentation velocity experiments (derived by e.g., SEDFIT, SEDANAL, Ultrascan, DCDT+). Concentration coupling and the simultaneous determination of size and density are further capabilities offered by HDR-MULTIFIT. The workshop will tackle the following topics:
- Determination of particle sizes and their distributions
- The influence of scattering and the role of Mie’s theory
- Correction of size distributions and their weighting
- Multiwavelength analysis of GS experiments
- Concentration coupling experiments for polydisperse distributions
- Simultaneous analysis of size, density and refractive index increment using density variation