Application of high-resolution-magic-angle-spinning (HR-MAS) NMR spectroscopy to cosmetic emulsions

HR-MAS NMR spectroscopy was utilized for the characterization of three cosmetic emulsions. The emulsions had the same chemical composition and were prepared in the same way except the homogenization step. Magic angle spinning (MAS) of the emulsions was applied to improve signal resolution by eliminating susceptibility changes as well as residual dipolar interactions within the sample. Spin-lattice relaxation times (T-1) were determined according to the inversion recovery technique in the temperature range of -10 degrees C to 40 degrees C to find out phase changes of the sample ingredients. H-1 and C-13 NMR signals of the individual components were assigned by use of different 1D and 2D NMR experiments. The HR-MAS NMR technique offers many possibilities to further investigate samples between the liquid and the solid state.