Chapter One
LC-NMR: Theory and Experiment
KLAUS ALBERT
Institut für Organische Chemie, Universität Tübingen, Tübingen, Germany
1.1 INTRODUCTION
The conventional way of recording solution-state NMR spectra is by the use of
a 5 mm cylindrical NMR tube in which the compound of interest is dissolved in
0.5 m1 of a deuterated solvent. The sample is constantly available for an infinite
time period for the registration of NMR spectra. With the commonly applied
Pulse Fourier-Transform acquisition mode, a gain in signal-to-noise ratio (S/N)
of the acquired NMR spectrum can be obtained by co-adding the Free Induction
Decays (FIDs) resulting from pulse excitation. The FID is dependent upon
the relaxation time [T.sub.2], which effects the line shape and the resolution of a
spectrum. The recovery of equilibrium magnetization is determined by the spin-lattice
relaxation time [T.sub.1] (Figure 1.1). After pulse excitation, it takes a time
period of three to five times the [T.sub.1] to establish the full Boltzmann distribution,
together with full magnetization of the nuclei. Then, ... read full excerpt from On-line LC-NMR and Related Techniques ebook
