Nuclear magnetic resonance monitoring

Boulanger, Y. Vinay, P. (1989). Nuclear magnetic resonance monitoring of sodium in biological tissues. Can. J. Physiol. Pharmacol. 67, 820-828. 

Medina, I., Sacchi, R., and Aubourg, S., 1994, nuclear magnetic resonance monitoring of free fatty acids release after fish thermal processing, JAOCS, 71, 479. 

Nuclear magnetic resonance monitoring of the synthesis of amphiphilic copolymers has also been reported by Larazz et al. [174] for the copolymerization of a methacrylic macromonomer with amphiphilic character derived from Triton X-100 (MT) with acrylic acid (AA). In situ H NMR analysis was used to monitor comonomer consumption throughout the copolymerization reactions, initiated by AIBN in deuterated dioxane, at 60 °C. The results from two different approaches used by the authors to estimate the reactivity ratio of the macromonomer indicate that AA is less reactive than the macromonomer MT and a model monomer with lower molecular weight but same structure, suggesting that methacrylic double bond reactivity was not affected by poly(oxyethylene oxide) chain length. 

Lutz J-F, Matyjaszewski K. Nuclear magnetic resonance monitoring of chain-end functionahty in the atom transfer radical polymerization of styrene. J Polym Sci A Polym Chem 2005 43 897-910. 

Some preliminary laboratory work is in order, if the information is not otherwise known. First, we ask what the time scale of the reaction is surely our approach will be different if the reaction reaches completion in 10 ms, 10 s, 10 min, or 10 h. Then, one must consider what quantitative analytical techniques can be used to monitor it progress. Sometimes individual samples, either withdrawn aliquots or individual ampoules, are taken. More often a nondestructive analysis is performed, the progress of the reaction being monitored continuously or intermittently by a technique such as ultraviolet-visible spectrophotometry or nuclear magnetic resonance. The fact that both reactants and products might contribute to the instrument reading will not prove to be a problem, as explained in the next chapter. 

It is particularly important to study process phenomena under dynamic (rather than static) conditions. Most current analytical techniques are designed to determine the initial and final states of a material or process. Instmments must be designed for the analysis of materials processing in real time, so that the cmcial chemical reactions in materials synthesis and processing can be monitored as they occur. Recent advances in nuclear magnetic resonance and laser probes indicate valuable lines of development for new techniques and comparable instmmentation for the study of interfaces, complex hquids, microstmctures, and hierarchical assemblies of materials. Instmmentation needs for the study of microstmctured materials are discussed in Chapter 9. 

The development and reports of methods for colorless chlorophyll derivative (RCCs, FCCs, and NCCs) analysis are relatively recent and the structures of the compounds are being elucidated by deduction from their chromatographic behaviors, spectral characteristics (UV-Vis absorbance spectra), mass spectrometry, and nuclear magnetic resonance analysis. The main obstacle is that these compounds do not accumulate in appreciable quantities in situ and, moreover, there are no standards for them. The determination of the enzymatic activities of red chlorophyll catabolite reductase (RCCR) and pheophorbide a monoxygenase (PAO) also helps to monitor the appearance of colorless derivatives since they are the key enzymes responsible for the loss of green color. ... 

Use of nuclear magnetic resonance imaging as a viscometer for process monitoring), Chem. Eng. Sd. 52, 2049. 

Online detection using 4H nuclear magnetic resonance (NMR) is a detection mode that has become increasingly practical. In a recent application, cell culture supernatant was monitored on-line with 1-dimensional NMR for trehalose, P-D-pyranose, P-D-furanose, succinate, acetate and uridine.33 In stopped-flow mode, column fractions can also be analyzed by 2-D NMR. Reaction products of the preparation of the neuromuscular blocking compound atracurium besylate were separated on chiral HPLC and detected by 4H NMR.34 Ten isomeric peaks were separated on a cellulose-based phase and identified by online NMR in stopped-flow mode. 

The pulsed field gradient nuclear magnetic resonance (PFG NMR) technique is experimentally distinct from the radiotracer technique but the principle is very similar. A fraction of the nuclei of each constituent is labelled by flipping their spins and monitoring the diffusion of these species. Both techniques are influenced by the presence of neutral associates unlike the Hittorf/Tubandt method. 

S. Clark, N.W. Barnett, M. Adams, LB. Cook, G.A. Dyson, and G. Johnston, Monitoring a commercial fermentation with proton nuclear magnetic resonance spectroscopy with the aid of chemometrics. Anal. Chim. Acta, 563, 338-345 (2006). 

Monitoring reaction progress throughout a multistep synthesis is a relatively difficult task.22 Typical methods used for solution-phase synthesis, including thin-layer chromatography (TLC), GC, and most types of mass spectrometry (MS), are less informative for solid-phase methods. However, Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) are particularly useful in solid-phase strategies. 

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