Molecular mass estimation by PFG NMR spectroscopy

A simplified PFG NMR diffusion analysis method was developed to estimate the molecular mass of small molecules in dilute aqueous and organic solutions. Internal referencing was utilized to improve the experimental robustness and simplify the data analysis. Specifically, tetramethylsilane (TMS) and HDO were chosen for the organic and aqueous reference molecules, respectively. Relative diffusivity-molecular mass correlations were empirically developed in the range of 2-1280 g/mol for dilute CDCl3 and D2O solutions. The median error in the predicted molecular mass was found to be 10 rel%. The utility of the method was demonstrated by analyzing the major and minor components in olive oil.