Direct On-Line Coupling of Capillary HPLC with (1)H NMR Spectroscopy for the Structural Determination of Retinyl Acetate Dimers:  2D NMR Spectroscopy in the Nanoliter Scale

This paper presents the application of directly coupled capillary high-performance liquid chromatography (capillary HPLC) and proton high-field nuclear magnetic resonance spectroscopy (NMR) for structural elucidation of a so-far unknown kitol isomer. One- and two-dimensional continuous- and stopped-flow NMR spectra were recorded in a 180 μm i.d. capillary, corresponding to a detection volume of only 200 nL. Unequivocal structural assignment on the basis of 1D and 2D stopped-flow capillary HPLC-NMR experiments was performed. The kitol isomer mixture was present in a sample of thermally isomerized retinyl acetate and separated on a capillary column.