High-resolution magic angle spinning description of the interaction states and their kinetics among basic solutes and functionalized silica materials.

Modeling of the interaction is crucial to understanding and predicting chromatography. However, the complexity and variety of the grafted motifs render the creation of an accurate model overwhelmingly challenging, so that most often the classification of column separation properties is described by monitoring the retention times of carefully selected control molecules. We analyzed here the characteristics of the interplay of compounds of basic nature by (1)H HRMAS NMR, which provide relevant descriptors for products with pharmaceutical properties, with chromatographic phases for Reversed Phase Liquid Chromatography.

Chromatographic-nuclear magnetic resonance can provide a prediction of high-pressure liquid chromatography shape selectivity tests.

NMR diffusometry has been recently demonstrated as a means of investigating the mobility variations of solutes induced by chromatographic phases (under the acronym chromatographic-NMR). Particularly, a given compound has its average diffusivity reduced proportionally to its affinity towards the solid. In this work we propose the first comparison of chromatographic-NMR and tests for assessment of column performance, to investigate to what measure the novel approach could provide an assay of the outcome of a given stationary phase without the need of packing the relative column.

Chromatographic NMR in NMR solvents.

Recently, it was demonstrated that pseudo-chromatographic NMR experiments could be performed using typical chromatographic solids and solvents. This first setup yielded improved separation of the spectral components of the NMR spectra of mixtures using PFG self-diffusion measurements. The method (dubbed Chromatographic NMR) was successively shown to possess, in favorable cases, superior resolving power on non-functionalized silica, compared to its LC counterpart.

Pulsed field gradient magic angle spinning NMR self-diffusion measurements in liquids.

Several investigations have recently reported the combined use of pulsed field gradient (PFG) with magic angle spinning (MAS) for the analysis of molecular mobility in heterogeneous materials. In contrast, little attention has been devoted so far to delimiting the role of the extra force field induced by sample rotation on the significance and reliability of self-diffusivity measurements. The main purpose of this work is to examine this phenomenon by focusing on pure liquids for which its impact is expected to be largest.