Abstract
A new on-line sample preparation system using column-switching HPLC was developed for the structure elucidation of compounds in mixtures by NMR. This system consists of three HPLC sections, separating the compounds of interest (LC-1), trapping the separated compounds on a trapping column using H2O and then replacing H2O with D2O (LC-2), and eluting the compounds from the trapping column using a deuterated solvent for an NMR measurement (LC-3). The system allows easy separation of a trace amount of the compounds from a mixture, desalting and concentration of the separated compounds, and the use of a deuterated solvent, such as CD3OD, for an NMR measurement. It was successfully applied to the structure elucidation of (±)-propranolol hydrochloride and a mixture of vitamin E derivatives as models. This new tool should be of considerable value in various fields for rapid sample preparation for NMR measurements.
