CAPILLARY HPLC-NMR COUPLING HIGH-RESOLUTION NMR-SPECTROSCOPY IN THE NANOLITER SCALE

Coupling HPLC and NMR is one of the most powerful techniques for simul taneous separation and structural elucidation of unknown compounds in mixtures, To date, however, minimizing the detection volume, as is req uired when coupling NMR with miniaturized separation techniques, has b een accompanied by a dramatic loss in resolution of the NMR spectra, H ere, we report on the coupling of gradient capillary HPLC with on-colu mn, high-resolution NMR detection. On-line stopped-flow and static H-1 NMR spectra were acquired with capillary columns of 75-315 mu m i.d. With detection over a length of 1.2 cm, cell volumes cover a range of 50-900 nL, An on-line-detected NMR separation of dansylated amino acid s was carried out in a 315 mu m i.d. fused silica capillary packed to a length of 12 cm with C-18 stationary phase, The low solvent consumpt ion makes the use of fully deuterated solvents economically feasible. NMR spectra with resolution on the order of 3 Hz were obtained using a 50 nL detection cell to measure 1.1 nmol of dansylated gamma-aminobut yric acid under static conditions in a 75 mu m i.d. capillary.