APPLICATION OF ONLINE CAPILLARY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY NUCLEAR-MAGNETIC-RESONANCE SPECTROMETRY COUPLING FOR THE ANALYSIS OFVITAMIN-A DERIVATIVES

The direct on-line coupling between capillary high-performance liquid chromatography (capillary HPLC) and proton high-field nuclear magnetic resonance (NMR) spectrometry has been used to derive structural infor mation about constituents of a mixture of vitamin A derivatives. H-1 N MR spectra were recorded in the stopped-few and continuous-flow mode w ithin a 180 mu m I.D. capillary column mounted in a micro probe on a 6 00 MHz NMR spectrometer. The resolution of the H-1 NMR spectra obtaine d in capillary HPLC-NMR coupling experiments is sufficient to determin e coupling constants in the order of 1.5 Hz. The detection limit is in the lower nanogram range. A stopped-flow 2D-TOCSY experiment of a 1% solution of vitamin A acetate acquired within 4 h reveals that the acq uisition of 2D NMR spectra is possible in the nanoliter detection scal e without any loss of structural information.