Nuclear magnetic resonance data processing

J. C. Cobas, F. J. Sardina, Nuclear magnetic resonance data processing. MestRe-C A software package for desktop computers. Concepts in Magnetic Resonance Part A (2003), 19A (2), 80-96. 

X. Gao, Reeent Advances in Computational Methods for Nuclear Magnetic Resonance Data Processing, Genomics, Proteomics Bioinf., 2013,11, 29. 

Although relaxation measurements have been widely used in nuclear magnetic resonance studies of solid catalysts and adsorbed molecules, they have not found such favor in similar ESR work. Relaxation phenomena, however, do play a very important role in any magnetic resonance experiment, whether or not this aspect of the problem is studied. In fact, the temperature at which most ESR experiments are conducted is dictated by the relaxation process. Furthermore, even qualitative data on relaxation times can be used as supporting evidence in the identification of a paramagnetic species. 

R. Lefort, J. W. Wiench, M. Pruski and J.-P. Amoureux, Optimization of data acquisition and processing in Carr-Purcell-Meiboom-Gill multiple quantum magic angle spinning nuclear magnetic resonance. /. Chem. Phys., 2002,116, 2493-2501. 

Use of an integrated system incorporating CCC separation, PDA detector, and LC-MS proved to be a valuable tool in the rapid identification of known compounds from microbial extracts.6 This collection of analytical data has enabled us to make exploratory use of advanced data analysis methods to enhance the identification process. For example, from the UV absorbance maxima and molecular weight for the active compound(s) present in a fraction, a list of potential structural matches from a natural products database (e.g., Berdy Bioactive Natural Products Database, Dictionary of Natural Products by Chapman and Hall, etc.) can be generated. Subsequently, the identity of metabolite(s) was ascertained by acquiring a proton nuclear magnetic resonance ( H-NMR) spectrum. 

One of the principal contributions of electronic data processing over the past several years in terms of chemical analysis is the saving of manual effort in interpreting analytical data. Special techniques, such as Fourier transform, have increased speed (as well as sensitivity) by orders of magnitude in connection with infrared, nuclear magnetic resonance, and mass spectroscopy, Of course, for on-line process analyses, essentially instantaneous interpretation is required to provide the proper error signal that is used to position the final control element (valve, feeder, damper, etc.). 

Several spectroscopic techniques, namely, Ultraviolet-Visible Spectroscopy (UV-Vis), Infrared (IR), Nuclear Magnetic Resonance (NMR), etc., have been used for understanding the mechanism of solvent-extraction processes and identification of extracted species. Berthon et al. reviewed the use of NMR techniques in solvent-extraction studies for monoamides, malonamides, picolinamides, and TBP (116, 117). NMR spectroscopy was used as a tool to identify the structural parameters that control selectivity and efficiency of extraction of metal ions. 13C NMR relaxation-time data were used to determine the distances between the carbon atoms of the monoamide ligands and the actinides centers. The II, 2H, and 13C NMR spectra analysis of the solvent organic phases indicated malonamide dimer formation at low concentrations. However, at higher ligand concentrations, micelle formation was observed. NMR studies were also used to understand nitric acid extraction mechanisms. Before obtaining conformational information from 13C relaxation times, the stoichiometries of the... 

The original linear prediction and state-space methods are known in the nuclear magnetic resonance literature as LPSVD and Hankel singular value decomposition (HSVD), respectively, and many variants of them exist. Not only do these methods model the data, but also the fitted model parameters relate directly to actual physical parameters, thus making modelling and quantification a one-step process. The analysis is carried out in the time domain, although it is usually more convenient to display the results in the frequency domain by Fourier transformation of the fitted function. 

Nuclear Magnetic Resonance Concepts and Methods by Daniel Canet42 contains particularly clear presentations on techniques and data processing for Fourier transform NMR and related methods. Articles in the Encyclopedia of NMR on Fourier Transform Spectroscopy,43 Fourier Transform and Linear Prediction Methods, 39 and Maximum Entropy Reconstruction44 are also very informative. A Handbook of NMR includes a very clear description of the maximum entropy method and its limitations.19... 

In most fields of physical chemistry, the use of digital computers is considered indispensable. Many things are done today that would be impossible without modem computers. These include Hartree-Fock ab initio quantum mechanical calculations, least-squares refinement of x-ray crystal stmctures with hundreds of adjustable parameters and mar r thousands of observational equations, and Monte Carlo calculations of statistical mechanics, to mention only a few. Moreover computers are now commonly used to control commercial instalments such as Fourier transform infrared (FTIR) and nuclear magnetic resonance (FT-NMR) spectrometers, mass spectrometers, and x-ray single-crystal diffractometers, as well as to control specialized devices that are part of an independently designed experimental apparatus. In this role a computer may give all necessary instaic-tions to the apparatus and record and process the experimental data produced, with relatively little human intervention. 

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