Molecular and colloid chemical characterization

Analytical ultracentrifugation (AUZ)


Polymers or nanoparticles that are soluble or dispersible in aqueous media or organic solvents are suitable for the method. The required sample quantity is 100-500 mg. The method covers approximately the molar mass range from 103 to 1014  and particle sizes from 1 nm to about 500 nm.



  • Instrument: Optima XL-I analytical ultracentrifuge (Beckman-Coulter, USA)
  • Speed: 2000 to 60000 rpm
  • Solvents: water and aqueous salt solutions as well as organic solvents such as THF, toluene, DMF, DMF+LiCl, DMAc, etc.
  • Measuring cells: double sector cells made of carbon filled epon, aluminum, possibly titanium; multi-channel cells for sedimentation equilibria; overlay cells
  • Detection: absorption (200 - 800 nm), interference optics (if necessary striation optics MOM 3180)



  • Measurement of sedimentation velocity
    • Sedimentation coefficients s or s-distribution g (s)
    • Median molar masses / distributions using s-M calibration relations
    • Size distribution of nanoparticles
  • Measurement of concentration distribution in sedimentation-diffusion equilibrium
    • Median molar masses Mw, Mz (absolute value) and 2nd virial coefficient A2,o
  • Overlay experiment at low speeds
    • Diffusion coefficient Dx
  • Overlay experiment for density gradient centrifugation
    • Density ρ or density distribution g (ρ) of polymer particles