Proton mobilities in phosphonic acid-based proton exchange membranes probed by 1H and 2H solid-state NMR spectroscopy.

Two novel phosphonic acid-based "dry" proton exchange membrane materials that may allow for fuel cell operation above 100 degrees C have been prepared and characterized via solid-state 1H and 2H MAS NMR spectroscopy. We obtained information on both the nature of hydrogen bonding and local proton mobilities among phosphonic acid moieties. In particular, 2H MAS NMR line shape analysis yielded apparent activation energies of the underlying motional processes.

Monitoring the interactions of tocopherol homologues with reversed-phase stationary HPLC phases by 1H suspended-state saturation transfer difference high-resolution/magic angle spinning NMR spectroscopy.

The separation process in reversed-phase high-performance liquid chromatography employing C18 phases is mainly due to hydrophobic interactions. The separation of tocopherol isomers, exhibited by the C30 phases, however, is additionally driven by shape selectivity. This phenomenon is investigated by suspended-state nuclear magnetic resonance spectroscopy using the saturation transfer difference technique, which was originally introduced to study protein-ligand interactions.

Interactions of bupivacaine with a molecularly imprinted polymer in a monolithic format studied by NMR.

A trimethylolpropane trimethacrylate-based monolith of dimensions carefully chosen to fit exactly in a standard 4-mm solid-state CP/MAS NMR rotor was photopolymerized and subsequently molecularly imprinted with bupivacaine using a grafting protocol with methacrylic acid and ethylene dimethacrylate as monomers. As no crushing or grinding of the monolith was necessary, additional unspecific surface area was not created. This procedure ascertains that differences observed between imprinted and nonimprinted polymers are due only to graft imprinted surfaces and give therefore better results in NMR spectroscopy due to less unspecific interactions between analyte and monolith.