Capillary HPLC−NMR Coupling:  High-Resolution 1H NMR Spectroscopy in the Nanoliter Scale

• Published in: Analytical chemistry (Washington) 1996-04, Vol.68 (7), p.1110-1115
• Main Authors: Behnke, Beate, Schlotterbeck, Götz, Tallarek, Ulrich, Strohschein, Sabine, Tseng, Li-Hong, Keller, Tony, Albert, Klaus, Bayer, Ernst
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; NMR; Nuclear magnetic resonance; Other chromatographic methods; Scientific imaging
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac950925a

Coupling HPLC and NMR is one of the most powerful techniques for simultaneous separation and structural elucidation of unknown compounds in mixtures. To date, however, minimizing the detection volume, as is required when coupling NMR with miniaturized separation techniques, has been accompanied by a dramatic loss in resolution of the NMR spectra. Here, we report on the coupling of gradient capillary HPLC with on-column, high-resolution NMR detection. On-line stopped-flow and static 1H NMR spectra were acquired with capillary columns of 75−315 μm 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 acids was carried out in a 315 μm i.d. fused silica capillary packed to a length of 12 cm with C18 stationary phase. The low solvent consumption 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 γ-aminobutyric acid under static conditions in a 75 μm i.d. capillary.