Nuclear magnetic resonance quality control

Nuclear Magnetic Resonance (nmr). The nmr analysis has been used in the polymer industry for some time to measure properties such as amount and type of branching, polymerized ethylene oxide content, and hydroxyl content. The same techniques are applicable to waxes, and are used for both characterization and quality control. 

Advanced techniques like molecularly imprinted polymers (MIPs), infrared/near infrared spectroscopy (FT-IR/NIR), high resolution mass spectrometry, nuclear magnetic resonance (NMR), Raman spectroscopy, and biosensors will increasingly be applied for controlling food quality and safety. 

Schmidt, H. L. (1986). Food quality control and studies on human nutrition by mass spectro-metric and nuclear magnetic resonance isotope ratio determination. Fresenius Z. Anal. Chem. 324, 760-766. 

P. J. McDonald 1995, (The use of nuclear magnetic resonance for on line process control and quality assurance), in Food Processing Recent Developments, ed. A. G. Gaonkar, Elsevier, Oxford, (pp.) 23-36. 

Li, C.-Y. et al., Efficient IH nuclear magnetic resonance method for improved quality control analyses of ginkgo constituents, J. Agric. Food Chem., 52, 3721, 2004. 

Numerous analyses in the quality control of most kinds of samples occurring in the flavour industry are done by different chromatographic procedures, for example gas chromatography (GC), high-pressure liquid chromatography (fiPLC) and capillary electrophoresis (CE). Besides the different IR methods mentioned already, further spectroscopic techniques are used, for example nuclear magnetic resonance, ultraviolet spectroscopy, mass spectroscopy (MS) and atomic absorption spectroscopy. In addition, also in quality control modern coupled techniques like GC-MS, GC-Fourier transform IR spectroscopy, HPLC-MS and CE-MS are gaining more and more importance. 

DSC is increasingly being applied to the study of epoxy resin cure in combination with other analytical methods such as nuclear magnetic resonance and Fourier transform infra-red spectroscopy, chromatographic methods, and dynamic mechanical or dielectric studies. It is probably as part of such combined investigations that DSC can be used most effectively in basic research, and in quality control and assessment. 

Pearson, R.M. and Adams, J.Q. 1990. Automatic use of small nuclear magnetic resonance spectrometers for quality control measurements. In NMR Applications in Biopolymers (J.W. Finley, S.J. Schmidt, and A.E. Serianni, eds.) pp. 499-509. Plenum Press, New York. 

Nowadays, 3 P-NMR (nuclear magnetic resonance) is sometimes proposed as a better alternative, because this technique requires only a minimum amount of sample pretreatment (12-14). In our opinion, its high investment cost and need for highly qualified operators will cause P-NMR to remain a research technique rather than a quality-control method. However, being an absolute technique, P-NMR seems ideally suited to certify the composition of standard solutions whose quality largely determines the accuracy of both TLC and HPLC results (15,16). 

Duarte, I., Barros, A., Belton, P. S., Righelato, R., Spraul, M., Humpfer, E., and Gil, A. M. (2002). High-resolution nuclear magnetic resonance spectroscopy and multivariate statistical analysis for the characterization of beer.. Agric. Food Chem. 50, 2475-2481. Duarte, I. F., Barros, A., Almeida, C., Spraul, M., and Gil, A. M. (2004). Multivariate analysis of NMR and FTIR data as a potential tool for the quality control of beer. J. Agric. Food Chem. 52, 1031-1038. 

In the pharmaceutical industry, the techniques are being used to examine off-target effects particularly for the early identification of toxicity. MOA can be studied through metabolomics and can also be used as a quality control tool for complex mixtures such as foods or herbal medicines. Similarly, the tools and expertise of natural products chemists are essential in metabolomics, particularly in biomarker discovery (see also Volume 9). Biomarker discovery via untargeted metabolomics can lead to metabolite signatures (nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), etc.) that are not present in current metabolomics databases. This is particularly true for plant secondary metabolism studies and nonmammalian metabolites. Structure elucidation then becomes critical to understanding the metabolomics results and for biomarker development. 

Maciel, G.E. NMR in industrial process control and quality control. In Nuclear Magnetic Resonance in Modem Technology Maciel, G.E., Ed. Kluwer Academic Netherlands, 1994. 

After purification, quality control of solvent purity is necessary. For this purpose, many different analytical methods are utilized. Generally, chromatographic methods such as GC, GC-MS, and HPLC are used. Moreover, UV, infrared, and nuclear magnetic resonance spectroscopy can also be applied but they tend to be less sensitive toward trace impurities. Water in organic solvents is usually determined by Karl-Fisher titration. On the basis of experimental data obtained before and after purification, the efficiency of the clean-up procedure is determined. In general, the efficiency of purification, e.g., the recovery, is expressed by the coefficient R. This parameter is defined as the ratio of the amount of impurities removed to the amount of solvent before purification ... 

The quality control of radiopharmaceuticals labeled with short-lived radionuclides has to rely on indirect methods for the identification of the compound. Direct methods such as nuclear magnetic resonance (NMR) and infrared spectroscopy cannot be used. Some tests, such as measurement of pH and LC-analysis, can be performed before the radiopharmaceutical is released for use. The radiopharmaceutical is mixed with authentic reference substance and if... 

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