Molecular and colloid chemical characterization

Membrane osmometry


The method is suited for polymers and nanoparticles, which can be dissolved or dispersed in aqueous media or organic solvents. The required amount of sample is in the range between 100 and 500 mg. The method covers the molar mass range from 104 to 105.



  • GONOTEC Membranomometer OSMOMAT 090
  • Membranen: Cellulose-Triacetat (cut-off 5000, 10000 and 20000 g/mol), Regenerierte Cellulose (cut-off 20000 g/mol)
  • Solvents: water and aqueous saline solutions, organic solvents, such as tetrahydrofurane, toluene and chloroform


Evaluation methods and targets

  • Measurement of the osmotic pressure p in dependence of the polymer concentration and extrapolation of the reduced osmotic pressure to the concentration 0
  • number-averaged molar mass Mn and 2nd virial coefficient A2


Application example

  • Molecular characterization of reference materials from Poly-DADMAC (→ PDF)


Comparative and additional methods

  • Gel permeation chromatography (Mn; MW; D)
  • Static light scattering (MW; RZ; A2)
  • Analytical ultra centrifugation (MZ; D)
  • Differential refractometry (dn/dc)
  • Dynamic light scattering (dH)
  • Vapour pressure osmometry (Mn)