The effectiveness of hetero-COSY, HETCOR, HMQC, and HSQC two-dimensional NMR pulse sequences for detection of (19)F-(1)H correlations by scalar coupling was evaluated on monofluorinated and polyfluorinated test compounds. All four of these sequences were effective in observing (1)H-(19)F correlations, using either (19) F or (1)H as the observe nucleus. All four sequences were amenable, to some degree, to adjustment to observe larger or smaller couplings preferentially. A 1/2J echo filter was effectively applied to remove artifacts from (2)JFF strong coupling. The HETCOR experiments afforded the best overall combination of sensitivity, resolution and selectivity for JHF.
The advent of benchtop nuclear magnetic resonance (NMR)
instrumentation
has paved the way for the use of this technology away from traditional
NMR facility settings. Still, a wider adoption of benchtop NMR systems
for routine identification testing has been hampered by inherent instrumental
limitations (including low sensitivity and reduced signal dispersion)
and workflow automation challenges. The present study summarizes the
results of a cross-company collaboration aiming at the development
of rapid, automated identification tests for incoming materials in
liquid form intended for pharmaceutical manufacturing. Potential scenarios
that analysts may encounter during the development of identification
tests using benchtop NMR instrumentation are described, and suitable
strategies for data collection and analysis are discussed. Challenges
and opportunities for benchtop NMR implementation are illustrated
using common organic solvents and laboratory reagents in a neat form,
for which reference NMR data are provided.
NMR spectroscopy is a uniquely convenient and information-rich tool for the study of chemical reactions in the gas phase. This report discusses strategies employed to address the special experimental challenges posed by elevated pressure and temperature, and the spectroscopic peculiarities of the gas phase. The extensive literature on the application of gas phase NMR to the study of reaction kinetics (consisting of 11 publications) is surveyed. A study of the gaseous decomposition of di-tert-butyl peroxide, as conducted with modern instrumentation and software, is described in detail. The report concludes with a summary of recent work applying two-dimensional NMR correlation and diffusion experiments to gaseous analytes.
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