A Molecular Mass calculator from Diffusion measurements

Version 0.5


This page implements the estimate of molecular mass from the measurement of diffusion coeeficient as proposed in :
Augé et al. J Phys Chem B (2009) 113 p1914-1918 DOI: 10.1021/jp8094424


In this wotk, a power law relating molecular mass with diffusion coefficients is described and found to be valid over 4 orders of magnitude. From this law, the fractal dimension of the molecular family can be measured, with experimental values ranging from 1.41 to 2.56 in full agreement with theoretical approaches.

Experimental NMR diffusion measure are presented. These results, complemented with results found in the literature, enable a general description of effective fractal dimension for objects such as small organic molecules, sugars, polymers, DNA, and proteins.

From this measurements, it is possible to estimate the molecular mass of unknown solutes. For this, a molecule of reference, present in the solution along with the unknown molecule has to be used, and all the analysis is performed on the diffusivity Dr defined as the ratio of the diffusion coefficients :

Dr = Dinterest / Dreference

In this case, it is shown that the molecular mass is estimated from :

MW = ( Cr / Dr ) dF

where Cr is specific to the studied system (molecular familly; solvent; reference molecule) and dF is the fractal dimension.

This relation can be used on a homogeneous molecular familly for which the parameters have been experimentally determined.


To use this tool, you should


Select Molecule type : Select solvent : select reference molecule :

Diffusion coefficient of molecule of interest +/-

Diffusion coefficient of reference molecule +/-

Diffusion coefficients can be entered in any unit, as long as the same unit is used for both entries
Error bars are optional, put 0.0 if not available, but 10% error is typical

What is available

as of Dec 18th, 2009, Version 0.5


  1. NMR measure of Translational Diffusion and Fractal Dimension. Application to molecular mass measurement.
    Sophie Augé, Pierre-Olivier Schmit, Christopher A. Crutchfield, Mohammad Islam, Douglas J. Harris, Emmanuelle Durand, Martin Clemancey, Anne-Agathe Quoineaud, Jean-Marc Lancelin, Yann Prigent, Francis Taulelle, and Marc-André Delsuc

    J Phys Chem B (2009) 113 p1914-1918 DOI: 10.1021/jp8094424

  2. Validation of molecular mass measurements by means of Diffusion-Ordered NMR Spectroscopy; Application to Oligosaccharides.
    Olivier Assemat, Marie-Aude Coutouly, Redouane Hajjar, Marc-André Delsuc C.R. Chimie in press DOI: 10.1016/j.crci.2009.10.005

© M-A Delsuc