The benefit of precise chemical shift and concentration referencing in NMR applications
“In Nuclear Magnetic Resonance (NMR) spectroscopy, the chemical shift and intensity of NMR signals provide critical information about a sample's molecular structure, reaction conditions, and material properties. For the precise determination of structures and properties, it is critical to know sample or reaction conditions such as temperature, pH, concentration, or absolute amount of material. Chemical-shift and signal-intensity calibrations play a key role for extracting the maximum amount of information from NMR experiments. In this dissertation, internal and external reference standards are used to calibrate NMR spectra with respect to chemical shift and signal intensity. Sealed capillary tubes filled with specific solutions (e.g., chloroform, trifluoroacetic acid, hydrochloric acid, ethylene glycol, methanol, aqueous solutions with small amounts of CuSO4) were utilized as external references for chemical-shift and signal-intensity calibrations in liquid-state and solid-state NMR applications. Absolute concentration calibrations are an essential part for quantitative NMR investigations. For concentration calibrations, a number of parameters must be optimized prior to conducting quantitative NMR experiments. Several calibration techniques are presented such as using capillary-tube inserts or CapPack devices as external references. In addition to concentration calibrations, CapPack devices are also used to determine sample temperatures or pH values in liquid-state and solid-state NMR. Applications presented here include (a) determination of residual water in ionic-liquid rocket monopropellants, (b) determination of chemical shifts, relaxation times, and intermolecular transfer of signal saturation for the analysis of interactions between polymer micelles and small molecules in solution, and (c) innovative studies of the release kinetics of small molecules from loaded porous-wall hollow glass microspheres”--Abstract, page iii.
Cappack device, Chemical shift, Concentration referencing, NMR, PWHGMs, Temperature, Organic Chemistry, Physical Chemistry
Missouri University of Science and Technology
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