REVERSE-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY NUCLEAR-MAGNETIC-RESONANCE SPECTROMETRY IN PROTONATED SOLVENTS

On-line continuous flow high-performance liquid chromatography/nuclear magnetic resonance (HPLC-NMR) separations are performed in fully protonated reverse-phase solvent systems by using the 1-1 hard pulse retains the spectral quality achieved in deuteriated solvents as spectra resolution remains data point limited and a 50-.mu.g injection of caffeine yields a signal to noise (S/N) ratio of 12:1 in continuous flow mode for a 28-.mu.L cell volume. The effects of solvent gradients on the NMR signal are examined for H2O-acetonitrile and H2O-methanol at pH 7 and 4.4. Conditions are then chosen to perform a gradient separation of vitamins by HPLC/NMR.