Chemical-shift referencing and resolution stability in methanol:water gradient LC-NMR.
Solvent-gradient LC-NMR can generate wide ranges of solvent conditions during an experiment. This complicates the chemical-shift referencing of the resulting NMR data. This problem and other experimental issues are evaluated here for LC-NMR in methanol:water, using solvent mixtures running from 0% to 100% methanol. It is shown that the use of the methanol methyl signal is superior to the use of the water signal in any form (either the 1H or the 2H signal), either as a secondary reference, as a signal for shimming, or as a lock signal. Also shown are the limitations of the referencing methods and other experimental parameters, and the limitations of the solvent-gradient ramp parameters, primarily as they affect lineshapes.
Keifer
Paul A
PA
Varian, Inc., 3120 Hansen Way D-298, Palo Alto, CA 94304-1030, United States. PAKeifer@gmail.com
D000465:Algorithms; D002851:Chromatography, High Pressure Liquid; D003903:Deuterium / Q000737:chemistry; D017666:Deuterium Oxide / Q000737:chemistry; D004058:Diffusion; D004574:Electromagnetic Fields; D017665:Hydroxyl Radical; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D000432:Methanol / Q000737:chemistry*; D012997:Solvents; D014867:Water / Q000737:chemistry*
D012997:Solvents; D014867:Water; D017665:Hydroxyl Radical; D003903:Deuterium; D017666:Deuterium Oxide; D000432:Methanol