Nuclear magnetic resonance (NMR) spectroscopy (original) (raw)
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Nuclear Magnetic Resonance (NMR) as Spectroscopy Analysis Method
Proton NMR is without a doubt the single most important spectroscopic technique for organic chemists who are attempting to determine or confirm the identity of a compound. I want to emphasize here that the theory and uses of NMR are very complex. There are dozens if not hundreds of NMR experiments that can be performed besides the carbon and proton NMR experiments that are familiar to you from your undergrad organic course. If you want to learn more about the theory behind NMR and the myriad ways it can be used, you can look into taking an NMR class at your university
Nuclear Magnetic Resonance (NMR
NMR spectroscopy is an analytical chemistry technique used in quality control and reserach for determining the content and purity of a sample as well as its molecular structure.
NMR-the basic principles and its use in studies of water/ethanol/mixture
2012
NMR is the one of the most widely used and helpful spectroscopic technicque. It's theoritical parts depend on quantum physics, this technique has transformed the practice of chemistry.It's principle based on spin angular momentum and NMR interactions in a static magnetic field. Proton shows two orientations named α and β. When spins pulsed, spins are changed from one orientation to another. After pulse technique, spin relaxes. Longitudinal relaxation time,T 1 , called spin-lattice relaxation. If all spins relaxed enough, informations about molecules can be obtained from peaks and integrate of peaks. And peaks also represent chemical exchange in the mixtures. This project work, based on determine to principles and interactions of NMR and determine to usefully experiments on water/ethanol samples.
IOP Conference Series: Materials Science and Engineering, 2019
The injection of surfactant is potential to be lost during the process due to the adsorption of surfactant into the core. It is therefore crucial to analyzed the concentration of surfactant before and after injection to the core. Many methods are developed for determining the content of surfactant using UV-Vis Spectrophotometer by utilizing the chromophore group of the chemical. In this study, quantification of nonionic surfactant that absent of chromophore group was performed using a combination of mobile Nuclear Magnetic Resonance (NMR) with Solid Phase Extraction (SPE). SPE was used to extract the samples that dissolved in water, whereas NMR was used to identify the levels of nonionic surfactants that dissolved in deuterized solvents. Internal standard chemical was added to the sample to verify the concentration of samples. As a stationary phase was SPE C-18 and eluent was methanol, ethyl acetate, and nhexane. Furthermore, the SPE results were measured using mobile 1 H NMR 43 MHz with selected solvents namely deuterated chloroform (CDCl3) and internal standard Dimethyl Formamide (DMF). Optimization results for determination of surfactant concentration up to 0.5% w/w was using the C-18 stationary phase, mobile phase methanol, ethyl acetate, and nhexane.
Guide to NMR Method Development and Validation – Part I: Identification and Quantification
Nuclear Magnetic Resonance (NMR) spectroscopy is one of the most versatile methods of analysis. Till the early 1970s, NMR spectroscopy was exclusively used for structure elucidation and purity testing of synthesized compounds. Nowadays, however, the range of successful applications covers identification and structure elucidation of organic and biochemical molecules, precise quantitative determination of individual analytes and multicomponent analysis as well as so-called "non-targeted screening" in combination with different chemometric techniques [1, 2]. Since NMR is a very selective analytical tool (each molecule has its own spectral fingerprint), not only quantification of ingredients is possible, but also comparison, discrimination or classification of foods, beverages and other consumer products can be achieved (e.g., authenticity evaluation, determination of origin and botanical variety of certain products) [1]. "Non-targeted" NMR analysis allows a fast and highly selective sample screening, from which much more information can be obtained than by using any other analysis technique that was previously used for this purpose [1]. NMR techniques have been an integral part of scientific research for a long time and are increasingly used in the monitoring of foods, beverages, cosmetics and pharmaceuticals. The special criteria proposed in this report should facilitate development of any practical application of a NMR method in these areas of applications. Furthermore, our suggestions are in accordance with quality management (QM) system required for governmental food control [3-5]. It should be mentioned, however, that the conditions listed in this report must always be adapted for the specific analytical problem, the most recent QM requirement and the matrix under investigation.
Environmental Toxicology and Chemistry, 2019
Non-aqueous phase liquids (NAPLs), composed primarily of organic solvents and other immiscible liquids, can be found in the subsurface at many industrial sites. The chemical composition of NAPL is often complex and, in many instances, difficult to fully characterize using conventional analytical techniques based on targeted compound analysis. Incomplete characterization of NAPL leaves gaps in the understanding of the chemical profile at an impacted site. Previous work has shown that nuclear magnetic resonance spectroscopy (NMR) may be able to assist in the improved characterization of complex NAPL samples. In general, NMR provides an unbiased approach for the analysis of organic compounds as different classes of compounds are all treated and analyzed using the same methods. Additionally, NMR provides unique structural information that can be used to elucidate unknowns. This paper describes the use of NMR spectroscopy as a non-targeted tool to characterize the composition of NAPL collected from an impacted site. It is shown that NMR can be a complimentary tool to be used in site assessments to help provide improved understanding of NAPL chemistry, leading to the development of improved conceptual site models, and improved strategies for remedial and managerial activities at impacted sites.
Characterization of emulsions by NMR methods
Journal of Colloid and Interface Science, 1991
Pulsed-gradient spin-echo NMR experiments are performed on emulsions stabilized by nonionic, cationic, and anionic surfactants. The mean displacements during the measuring time of the liquid inside the emulsion droplets are of the same order of magnitude or larger than the diameter of the droplet, and as a consequence the molecules undergo restricted diffusion. Murday and Cotts' equation for restricted diffusion inside spherical cavities can be fitted to the experimental data using the bulk diffusion coefficient value for the liquid. The continuous medium gives normal diffusion coefficients, slightly reduced due to obstruction effects of the emulsion droplets. For some cases the stimulated spin-echo technique must be used to evaluate the diffusion coefficients as short T2's make it difficult to perform experiments with the ordinary PGSE sequence, The approach can be used in dilute and nondilute systems to infer information about the droplet size and size distribution and whether a particular emulsion is of the O/W or the W/O type.
Nuclear Magnetic Resonance Spectroscopy
2004
Over the past fifty years, nuclear magnetic resonance spectroscopy (NMR) has gained popularity in a wide variety of research areas. Its non-invasive character makes it ideal for the study of biomolecules and tissue samples. The possibility of determining the solution structure of molecules with the use of NMR has led to important advances in many areas including pharmacy, biology, botany, medicine, sensor design, study of polymers and more. The technology used in spectrometer and probe design have advanced to allow the study of molecules in solids, liquids, and gels. Additionally, data in the form of images, multidimensional spectra, or relaxation profiles can be obtained to study systems from different fronts. The possibility of detecting multiple nuclei allows intimate examination and characterization of a wide variety of materials. This Special Issue devoted to NMR, and the associated Special Issue reprint, contain papers covering some of the most innovative and exiting NMR applications to different systems.
Analytical Chemistry, 1998
Nuclear magnetic resonance (NMR) can be used to provide an independent and intrinsically reliable determination of chemical purity. Unlike chromatography, it is possible to employ a universal reference standard as an internal standard for the majority of chemical products assayed by quantitative NMR (QNMR). This is possible because the NMR response can be made the same for all chemical components, including the internal standard, by optimizing certain instrumental parameters. Experiments were performed to validate the quantitative NMR method described in this paper for the analysis of organic chemicals. Experimental precision, accuracy, specificity, linearity, limits of detection and quantitation, and ruggedness were systematically addressed, and system suitability criteria were established. The level of the major chemical ingredient can be determined with accuracy and precision significantly better than 1%, and impurities may be quantified at the 0.1% level or below. Thus, QNMR rivals chromatography in sensitivity, speed, precision, and accuracy, while avoiding the need for a reference standard for each analyte. Examples are given of 1 H and 31 P NMR used for quantitative analysis of agricultural chemicals, and a method for characterization of analytical standards is presented.