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Nuclear Magnetic Resonance (NMR) in Food Processing Applications
Published in Azharul Karim, Sabrina Fawzia, Mohammad Mahbubur Rahman, Advanced Micro-Level Experimental Techniques for Food Drying and Processing Applications, 2021
Azharul Karim, Sabrina Fawzia, Mohammad Mahbubur Rahman
Based on the NMR spectrum and magnetic resonance imaging (MRI) techniques, NMR technology is of two types: high-resolution NMR (HR-NMR) and low-field NMR (LF-NMR) [15]. NMR technology has been widely used in food science in recent years due to the need for effective quality control analysis and the growing need for technological and product innovation in the food industry. NMR spectroscopy is used to determine the relaxation time, and the relaxation time of NMR is used to assess the consistency of food and to measure chemical compositions [17]. NMR relaxation technology is very common in the food industry.
Automated Reactions in Continuous Flow Reactors
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Frederic G. Buono, Bing-Shiou Yang
Several examples described flow cells in HF NMR machines, or microcoils for microfluidic applications (Harel, 2009; Jones and Larive, 2012; Gökay and Albert, 2012; Buser and McFarland, 2014). The capability to quantitatively monitor dissolved hydrogen gas concentration by 1H NMR at high pressure with continuous circulation was developed and provided valuable insight for the characterization of organic reactions (McFarland and Buser, 2014). However, the analytical performance of HF NMR is associated with expensive instrumentation and the need for specific facilities. Recently, a new generation of low field NMR (LF NMR) spectroscopy benchtop spectrometers relying on non-cryogenic magnets was developed. These spectrometers are practical, transportable, ecofriendly, and relatively cheap. In addition, the quality of the 1H spectra of these spectrometers has been improved, particularly in terms of sensitivity and stability (Küster et al., 2011; Sans et al., 2015) . However, the low magnetic field inevitably leads to a reduced dispersion of frequencies, generating numerous peak overlaps. Moreover, the real-time identification of chemical compounds is further complicated by the strong couplings commonly encountered in LF NMR, and the application range of LF NMR monitoring has been limited to relatively simple reactions in which the peaks of interest are well isolated. Magritek Company has developed a platform for synthetic chemistry incorporating an inline benchtop NMR that uses a compact permanent magnet (43 MHz) based on the Hallbach design employing individual magnet blocks arranged in a cylindrical fashion with additional rectangular blocks that can be adjusted to manually correct the inhomogeneities of the magnetic field (Danieli et al., 2010, 2013). Using this platform, structural characterization of reaction mixtures can be done using 19F, 13C, distortionless enhancement by polarization transfer (DEPT), and 2-D NMR spectroscopy (correlations spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), and 19F-COSY). Recently a configurable flow platform controlled via a modular LabView software control, NMR, data analysis, and feedback optimization was developed (Figure 20.21) (Sans et al., 2015).
Characterization of oil-in-water pickering emulsions stabilized by β-cyclodextrin systems
Published in Journal of Dispersion Science and Technology, 2023
Sophie Piot, Léon Mentink, Anne-Marie Pensé-Lhéritier
Low field NMR (nuclear magnetic resonance). Low field Nuclear Magnetic Resonance (NMR) was used to compare the compartmentalization of water in the O/W emulsions formulated using the blends as emulsifying system and thus to highlight their different physico-chemical behaviors. Analysis have been realized on a Minispec mq 20 of Bruker type operating at 20 MHz. For each emulsion, three series of measurements were performed by low field NMR. Analysis gave information related to:The total amount of visible protons present in the sample,The state of structuring of the product (texture information),The compartmentalization of protons (highly bound/bound/highly free protons).
Effect of shape on depth profile Nuclear Magnetic Resonance data of multilayered composite structure
Published in Nondestructive Testing and Evaluation, 2023
Sanjaya K Sahoo, Srinivas Kuchipudi, Ch. Sri Chaitanya, R Narasimha Rao, Manoj K Buragohain
Single-sided low field NMR system is based on the principle of inside-out NMR, where the sample is outside the magnet. These systems are provided with stepper motor for precise lifting of magnets to magnetise the region of interest inside the sample. For the present studies, we have used commercially available single sided low frequency NMR system (Model PM 25, Make: Magritek) with 12.88 MHz RF frequency. The profile NMR-MOUSE (PM 25) is a portable open NMR sensor equipped with a permanent magnet (Bo equivalent to 0.3 T) geometry that generates a highly uniform gradient perpendicular to the scanning surface outside the magnets. Figure 2 shows the low field NMR experimental setup and its schematic used for the present work. A flat sensitive volume is excited and detected by a surface RF coil (frequency 12.88 MHz) placed on top of the magnet at a position that defines the maximum penetration depth into the sample. The single sided NMR system consists of RF coil of 12.88 MHz matching with the Larmour frequency of proton. Hence, proton NMR is being used for the non-destructive evaluation of multi-layered structures having non-conduction materials. The system is not designed for the variable frequency selection, hence, in this case, the frequency selection is not possible. The stepper motor assembly does not interfere with the magnetic field. By repositioning the sensitive slice across the object, this scanner produces 1D profiles of the sample with a spatial resolution of 100 μm. Carr-Purcell-Meiboom-Gill (CPMG) pulse sequences were used for determining the T2 relaxation times [20]. The present study reports results from the experiments performed with CPMG pulse sequence at predefined position programmed using Prospa software. The sensor excites a sensitive volume at a fixed distance from the magnet surface as per the program. By mechanically moving the sensor, the sensitive volume is stepped through the sample and the CPMG sequence is then applied at each position with an echo-time of 60 µs. Then, signal from each position is plotted as amplitude versus depth plot to generate depth profile of the sample. The main setting and experimental parameters are given in Table 1.