ABSTRACT
Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful techniques available for studying the structure of molecules. The NMR technique has developed very rapidly since the rst commercial instrument, a Varian HR-30, was installed in 1952 at the Humble Oil Company in Baytown, Texas. These early instruments with small magnets were useful for studying protons (1H) in organic compounds, but only neat liquids or solutions with a high concentration of analyte. That has now changed-much more powerful magnets are available. NMR instruments and experimental methods are now available that permit the determination of the 3D structure of proteins as large as 900,000 Da. “Magic angle” NMR instruments are commercially available for studying solids such as polymers, and 13C, 19F, 31P, 29Si, and other nuclei are measured routinely. NMR imaging techniques under the name magnetic resonance imaging (MRI) are in widespread use in noninvasive diagnosis of cancer and other medical problems. NMR instruments coupled with liquid chromatographs and mass spectrometers for separation and characterization of unknowns are commercially available. Resolution and sensitivity have both increased; detection and identication of ppm concentrations of substances with NMR is easily achieved in modern instruments, and detection limits are approaching nanogram levels. NMR detection is being coupled with liquid chromatographic separation in high-performance liquid chromatography (HPLC)–NMR instruments for identication of components of complex mixtures in the owing eluent from the chromatograph, and NMR is now used as a nondestructive detector combined with mass spectrometry (MS) and chromatography in HPLC-NMR-MS instruments, an extremely powerful tool for organic compound separation and identication. In short, the eld has broadened greatly in scope, especially since the 1970s, and gives every indication of continuing to advance for many years to come.
