Low-field NMR Relaxometry Research Articles

Low Field NMR Relaxometry Characterization of Water Adsorption in Corn Stover Anatomical Fractions

Low Field NMR Relaxometry Characterization of Water Adsorption in Corn Stover Anatomical Fractions

Chert outcrops differentiation by means of low-field NMR relaxometry

Siliceous rocks served as raw materials in the production of stone tools from the Middle Paleolithic onwards. Due to migration, the provenance of archaeological artefacts can differ from their natural outcrop location. The aim of this work was the application of 1D and 2D low-field nuclear magnetic resonance (LF-NMR) relaxometry to distinguish cherts by their original source. Herein, bedded cherts and accompanying nodular cherts coming from three different outcrops of Kraków-Częstochowa Upland were investigated. 1D and 2D (T1-T2) experiments of water-saturated and dry rock sample states delivered T1, T2 times and T1/T2 ratios of distinct hydrogen populations – parameters sensitive to pore size, surface properties, and hydrogen bonding length. In-depth analysis of NMR data showed substantial differences in the porosity, pore surface and pore structure properties of investigated chert samples tested in the three different saturation levels (100% water-saturated, dried and differential). Finally, principal component analysis (PCA) was performed to reduce the number of correlations obtained and highlight the most important NMR properties specific to the particular outcrop localization."Please check captured corresponding author email if correct.""The email is correct"

Investigating the crystallinity of hard candies prepared and stored at different temperatures with low field-NMR relaxometry.

In this study, hard candies were produced by using sucrose, glucose syrup and water. They were cooked at different temperatures, changing from 135 to 145 °C with an interval of 2.5 °C. They were stored at different storage temperatures, which were 25, 4, -18 and -80 °C. Hard candies placed at room temperature were stored for 2 months. In order to understand the crystallization characteristics of the hard candies, time domain (TD) proton nuclear magnetic resonance (1H-NMR) parameters of longitudinal relaxation time (T1) and second moment (M2) measurements were conducted. Moisture contents of the hard candies were determined by Karl-Fischer titration. X-ray diffraction experiments were also conducted as the complementary analysis. Increasing cooking temperature increased the crystallinity and decreased the moisture content of the hard candies significantly (P ≤0.05). Furthermore, storage temperature and storage time had significant effects on the crystallinity of the hard candies (P ≤0.05). The results of T1 and M2 correlated with each other (r > 0.8, P ≤ 0.5) and both produced the highest value at the cooking temperature of 145 °C and storage temperature of 4 °C (P ≤ 0.05). The values of T1 and M2 were obtained as 245.9 ms and 13.0 × 10-8 Hz2, respectively, for the cooking temperature of 145 °C and storage temperature of 4 °C. This study demonstrated that the crystallinity of hard candies can be observed and examined by TD-NMR relaxometry, as an alternative to commonly used methods. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Understanding Polymer-Colloid Gels: A Solvent Perspective Using Low-Field NMR

The present work emphasizes the relevance of low-field NMR relaxometry to investigate colloid-polymer hydrogels by probing water dynamics across a wide range of formulations between 10°C and 80°C. By examining...

Comparative analysis of vegetable oils by 1H NMR in low and high magnetic fields

High-resolution 1H NMR, high-field 1H NMR relaxometry, and low-field (<0.5 T) NMR relaxometry have been applied to study different types of olive and soybean oils. It has been shown that the use of spectral and relaxation information in high-field NMR is an effective tool for the detection of oil adulteration and identification of food oils, including oils with close content. We have also shown that low-field NMR relaxation measurements can be applied for the discrimination between various food oils in the case of a limited group of samples. This work has demonstrated the possibilities of the different types of pulse NMR experimental methods for the analysis of vegetable oils.

Using 1H low-field NMR relaxometry to detect the amounts of Robusta and Arabica varieties in coffee blends

Low-field nuclear magnetic resonance (LF-NMR) is a method of widespread use in food research due to its non-destructive character and the relatively low cost of the instruments, allowing the determination of oil / fat contents and the achievement of images of different types of food materials, among other uses. In this work, 1H LF-NMR relaxometry was used to distinguish the contributions due to Arabica and Robusta coffee varieties present in coffee blends. As the method detects preferentially the NMR signals due to phases with high molecular mobility, which exhibit longer values of the 1H transverse relaxation time (T2), the difference in the oil contents associated with Arabica and Robusta coffee was the key factor responsible for the detection of the contributions due to each variety. The analysis presented in this work showed that the relative hydrogen index is a useful parameter to be used in quantitative analyses of the contents of each coffee variety present in the blends. The results illustrate the high potential of applicability of LF-NMR relaxometry as a screening tool for quality control and adulteration detection of coffee-related products.

Monitoring settling of anaerobic digestates using low-field MRI profiling and NMR relaxometry measurements

Dewatering of anaerobic digestate from red meat processing was assessed using low field MRI profiling and NMR relaxometry. Samples were flocculated using a cationic flocculant (EM640CT) at dosing range (0 to 1.6% v/v) and monitored during the initial 30 min of settling via MRI profiling to assess changes in water fraction, settling time and initial settling velocity. The profiles showed decreasing settling time and increasing initial settling velocity with increased dosing, while sample porosity was observed to increase up to the optimal dosing point (0.8% v/v). Significant increases in sample variability were observed past this point due to flocculant overdosing. The samples were then analysed in terms of turbidity and NMR relaxometry. Increasing flocculant concentration caused turbidity to decrease from 210 to 13 NTU. The relaxation rate of free water showed a strong positive correlation with turbidity. T2 peaks observed before overdosing could be assigned to different water structures (free, interstitial, vicinal and hydration). An additional T2 population emerged in the T2 distributions at the optimal dosing point. Multivariate exploratory data analysis (MEDA) showed that this T2 population from the solids layer was strongly correlated with the total solids layer height and turbidity of the watery layer. This T2 peak formation may therefore be used to study opaque flocculated solids to monitor for water structures associated with flocculant overdosing. Further studies using this technique will aim to assess the potential of low field T2 relaxometry monitoring inline before mechanical dewatering, to monitor optimal flocculant dosing during continuous operations on systems with high solids concentration.

Evaluation of multicomplex systems on pomegranate concentrate loaded alginate hydrogels by low-field NMR relaxometry: physicochemical characterization and controlled release study.

The online version contains supplementary material available at 10.1007/s13197-023-05730-2.

Carbonaceous Materials Porosity Investigation in a Wet State by Low-Field NMR Relaxometry.

The porosity of differently wetted carbonaceous material with disordered mesoporosity was investigated using low-field 1H NMR relaxometry. Spin−spin relaxation (relaxation time T2) was measured using the CPMG pulse sequence. We present a non-linear optimization method for the conversion of relaxation curves to the distribution of relaxation times by using non-specialized software. Our procedure consists of searching for the number of components, relaxation times, and their amplitudes, related to different types of hydrogen nuclei in the sample wetted with different amounts of water (different water-to-carbon ratio). We found that a maximum of five components with different relaxation times was sufficient to describe the observed relaxation. The individual components were attributed to a tightly bounded surface water layer (T2 up to 2 ms), water in small pores especially supermicropores (2 < T2 < 7 ms), mesopores (7 < T2 < 20 ms), water in large cavities between particles (20−1500 ms), and bulk water surrounding the materials (T2 > 1500 ms). To recalculate the distribution of relaxation times to the pore size distribution, we calculated the surface relaxivity based on the results provided by additional characterization techniques, such as thermoporometry (TPM) and N2/−196 °C physisorption.

Low-field time-domain NMR relaxometry for studying polymer hydration and mobilization in sodium alginate matrix tablets

Sodium alginate is used in various industries, including food, pharmaceutical, and agriculture. Matrix systems, e.g., tablets, and granules, are macro samples with incorporated active substances. During hydration, they are neither equilibrated nor homogenous. Phenomena occurring during hydration of such systems are complex, determine their functional properties and hence require multimodal analysis. Still, there's a lack of comprehensive view. The study aimed to obtain unique characteristics of the sodium alginate matrix during hydration, particularly considering polymer mobilization phenomena using low-field time-domain NMR relaxometry in H2O and D2O.An increase in total signal during 4 h of hydration in D2O of ca. 30 μV resulted from polymer/water mobilization. Modes in T1–T2 maps and changes in their amplitudes reflected physicochemical state of the polymer/water system: e.g. air-dry polymer mode (T1/T2 ~ 600) and two mobilized polymer/water modes (at T1/T2 ~ 40 and T1/T2 ~ 20).The study describes the approach to evaluating the hydration of the sodium alginate matrix in terms of the temporal evolution of proton pools: those existing in the matrix before hydration and those entering the matrix from the bulk water. It provides data complementary to spatially resolved methods like MRI and microCT.

Monitoring Cr(VI) photoreduction at different depths by operando low-field NMR relaxometry

Chromium (VI) (Cr(VI)), a toxic metal ion, is widely present in industrial wastewater. To reduce the contamination of Cr(VI), many technologies for the photocatalytic reduction of Cr(VI) to Cr(III) have been developed in the past decades. However, the practical application of photocatalysts for the reduction of Cr(VI) in wastewater treatment is often hindered by the complicated photoreduction processes due to the sedimentation and stratification of catalyst particles that present during the treatment of the wastewater. Probing and understanding the influences of the sedimentation and stratification of the catalyst particles on the photoreduction processes are long-term challenges in the field. Herein, we demonstrate that this issue can be solved by using layer location integrated low-field time-domain nuclear magnetic resonance (LF-NMR) relaxometry. With paramagnetic Cr (III) cation as the molecular probe, we successfully monitored the Cr(VI) photoreduction processes by operando probing the 1H T2 relaxation time of the photoreduction systems. The influences of catalyst sedimentation and the light wavelength on photocatalysis were studied and discussed. The results showed the great potential of LF-NMR relaxometry in the study of Cr (VI) photoreduction processes during industrial wastewater treatments.

Study of zeolite anti-caking effects for fertilisers by 1H low-field NMR

Caking is associated with the consolidation of dry powder and granules, leading to losses of function and/or quality. It has been object of studies in the pharmaceutical, food and fertiliser areas since 1920′s because of its significant impact on product quality and value. Caking has been described as a three-step event consisting of sorption-dissolution-recrystallisation phases and constitutes a critical factor in fertilisers losses during storage while also hampering fertiliser application. Current methods for the evaluation of water sorption dynamics are expensive, time-consuming and/or inaccurate. This manuscript describes an unprecedented application of low-field 1H NMR relaxometry for the kinetic study of humidity uptake, in real-time, by urea mixed with different concentrations of an anti-caking agent (zeolite). The proposed method allows to follow the water uptake in different domains of the mixed fertiliser/zeolite samples. To our knowledge, this dynamic has not been observed and quantified so far in real-time.Furthermore, we presented the use of 2D-ILT for kinetic studies, being the first dimension the usual transverse relaxation and the second dimension the kinetic one. With this approach, the NMR relaxation times T2 correlated to time constants associated with the uptake kinetics of the water. This method could be extended to several kinetic studies and experiments with temperature variation. Depending on the kinetics of the studied process, the kernel of the Laplace transform must be suitably adapted.

A comparative physio-chemical study of steel slag blended cementitious materials in presence of hydroxyethyl methyl cellulose

The applications of steel slag (SS) in the cement industry provide a sustainable solution both for construction materials and industrial solid wastes, but the problem of easily bleeding presents a threat to its later performance and utilization efficiency. This work was designed to improve the water retention of SS blended cement by using hydroxyethyl methyl cellulose (HEMC) and evaluate the physio-chemical properties of the modified SS cement. The interaction mechanism between HEMC and SS blended cement was explored via calorimetry, acoustic and electroacoustic spectrometer, low-field NMR relaxometry, XRD, TG-DSC, as well as fluorescent microscopy. Results show that the water retention of SS blended cement mortar is improved both by ultra-fine grinding and incorporating HEMC, while the water retention rates are prominently increased from 84.87% to 94.35% by 0.1% HEMC. Ultra-fine grinding is able to activate SS and improve water retention ability more efficient compared with the application of HEMC. HEMC does not modify the amount of hydration heat but postpones the occurrence of the exothermic peak. A sudden increase in zeta potential demonstrates the Ca2+-adsorption on surfaces of SCM and cement particles. An additional peak commences on the 1H NMR spectrum of HEMC incorporated cement paste, which reflects the water adsorbed by HEMC, starting to submerge after 500 min via the desorption of water. HEMC affects the SS blended mortar via adsorbing on particles in the paste, capturing water and Ca2+ around it, thus improving the water retention and retarding the hydrate-polymerization.

Estimating Water Content in Water–Oil Mixtures and Porous MEDIA They Saturate: Joint Interpretation of NMR Relaxometry and Dielectric Spectroscopy

This article deals with the topical problem of estimating water content in water–oil mixtures within porous media they saturate, according to low-field NMR relaxometry and dielectric spectroscopy. The aim of the research is experimental validation of the capability of complex data interpretation to acquire information on the filtration-volumetric properties of drill cuttings, relaxation characteristics of oil-containing fluids, the water/oil ratio in water–oil mixtures, and their saturation of drill cuttings to control the composition of liquids produced from boreholes. The studies are carried out on samples of cuttings and oils taken from fields in the Northern regions of the West Siberian oil-and-gas province, where NMR studies have not been performed before. Based on the experimental data obtained, the possibility of water content assessment in water-in-oil mixtures and porous media they saturate were proved through NMR relaxometry. With the use of the proposed methodology, the amount of water in oil–water mixtures was established, and their main NMR characteristics were determined. The relative error in evaluating the proportion of water in mixtures based on high-viscosity oils is less than 10%, and about 20% for those based on light oils. When determining the oil–water ratio in the pore space of the drill cuttings, the error is about 15%. It was proven that joint use of these two techniques makes it possible to increase the reliability of the oil–water ratio assessment of all the samples studied. Furthermore, it was revealed that the NMR spectrum shifts to the right, and the spectrum of the complex permittivity shifts downwards during the transition from high-viscosity oils to light ones.

Oxygen saturation-dependent effects on blood transverse relaxation at low fields

ObjectiveBlood oxygenation can be measured using magnetic resonance using the paramagnetic effect of deoxy-haemoglobin, which decreases the textit{T}_{2} relaxation time of blood. This textit{T}_{2} contrast has been well characterised at the textit{B}_{{0}} fields used in MRI (1.5 T and above). However, few studies have characterised this effect at lower magnetic fields. Here, the feasibility of blood oximetry at low field based on textit{T}_{2} changes that are within a physiological relevant range is explored. This study could be used for specifying requirements for construction of a monitoring device based on low field permanent magnet systems.MethodsA continuous flow circuit was used to control parameters such as oxygen saturation and temperature in a sample of blood. It flowed through a variable field magnet, where CPMG experiments were performed to measure its textit{T}_{2}. In addition, the oxygen saturation was monitored by an optical sensor for comparison with the textit{T}_{2} changes.ResultsThese results show that at low textit{B}_{{0}} fields, the change in blood textit{T}_{2} due to oxygenation is small, but still detectable. The data measured at low fields are also in agreement with theoretical models for the oxy-deoxy textit{T}_{2} effect.Conclusiontextit{T}_{2} changes in blood due to oxygenation were observed at fields as low as 0.1 T. These results suggest that low field NMR relaxometry devices around 0.3 T could be designed to detect changes in blood oxygenation.

Kinetic Inhibition of Clathrate Hydrate by Copolymers Based on N-Vinylcaprolactam and N-Acryloylpyrrolidine: Optimization Effect of Interfacial Nonfreezable Water of Polymers.

Amphiphilic polymers have now been designed to achieve an icephobic performance and have been used for ice adhesion prevention. They may function by forming a strongly bonded but nonfreezable water shell which serves as a self-lubricating interfacial layer that weakens the adhesion strength between ice and the surface. Here, an analogous concept is built to prevent the formation of clathrate hydrate compounds during oil and natural gas production, in which amphiphilic water-soluble polymers act as efficient kinetic hydrate inhibitors (KHIs). A novel group of copolymers with N-vinylcaprolactam and N-acryloylpyrrolidine structural units are investigated in this study. The relationships among the amphiphilicity, lower critical solution temperature, nonfreezable bound water, and kinetic hydrate inhibition time are analyzed in terms of the copolymer compositions. Low-field NMR relaxometry revealed the crucial interfacial water in tightly bound dynamic states which led to crystal growth rates changing with the copolymer compositions, in accord with the rotational rheometric analysis results. The nonfreezable bound water layer confirmed by a calorimetry analysis also changes with the polymer amphiphilicity. Therefore, in the interface between the KHI polymers and hydrate, water surrounding the polymers plays a critical role by helping to delay the nucleation and growth of embryonic ice/hydrates. Appropriate amphiphilicity of the copolymers can achieve the optimal interfacial properties for slowing down hydrate crystal growth.

Nuclear Magnetic Resonance (NMR) study of Palm Kernel Stearin: Effects of cooling rate on crystallization behaviour

In this study, effects of different cooling rates (0.5,3.3,4.7 and 6.9 °C/min) on the crystallization behavior of palm-kernel-stearin (PKS) were studied by low-field NMR relaxometry. According to results, solid fat content (SFC), longitudinal relaxation time (T1), second moment (M2) and degree of crystallinity (%) of the samples increased with increase in cooling rate from 0.5 to 6.9 °C/min. In contrast, transverse relaxation time (T2) demonstrated an opposite behavior with respect to T1 and decreased when the cooling rate increased. Additionally, effects of cooling rate on the changes of polymorph structures were detected by X-ray measurements. Degree of crystallinity showed high Pearson correlation values (α ≤ 0.05) with SFC (r= 0.771) and T1(r= 0.932). Changes in the crystal polymorphs could also be explained by NMR parameters to some extent as can be observed by the strong correlation between the β crystal content and T2 (r= 0.927). At the highest cooling rate, β′ crystals were the dominant polymorphic form and constituted 75(%) of the total crystals present. Results of this study suggested that NMR relaxometry could be used as a complementary tool to interpret the crystallization behavior of PKS.

Interaction of resorcinol-formaldehyde carbon aerogels with water: A comprehensive NMR study

Carbon aerogels prepared from resorcinol-formaldehyde aerogels are promising platforms for electrodes, catalysts, adsorbents in environmental chemistry and as electric conductors. For these applications the knowledge of their structure and behavior in aqueous medium is essential. In this work two resorcinol-formaldehyde (RF) carbon aerogels prepared in different ways were characterized with various NMR methods while their pore structure was stepwise saturated with water. The wetting properties were studied by vapor adsorption and low-field NMR relaxometry, while the morphology was followed by NMR cryoporometry during the hydration process. At several water saturation levels the self-diffusion of water was measured. The comprehensive evaluation of the results led to a detailed description of the wetting process of these carbon aerogels beyond the pore size distributions. At low hydration level water clusters formed on and around the hydrophilic functional groups of the surface being able to adsorb water, but no continuous water layer developed on the surface. With increasing water content, spherical water drops formed inside the pore system, and vapor phase diffusion was observed in the partially filled pores. Subsequently the interconnected pore structure was saturated. The determined wet structure was compared to low temperature nitrogen gas adsorption results and scanning electron microscopy images.

Detecting Dye-Contaminated Vegetables Using Low-Field NMR Relaxometry.

Dyeing vegetables with harmful compounds has become an alarming public health issue over the past few years. Excessive consumption of these dyed vegetables can cause severe health hazards, including cancer. Copper sulfate, malachite green, and Sudan red are some of the non-food-grade dyes widely used on vegetables by untrusted entities in the food supply chain to make them look fresh and vibrant. In this study, the presence and quantity of dye-based adulteration in vegetables are determined by applying 1H-nuclear magnetic resonance (NMR) relaxometry. The proposed technique was validated by treating some vegetables in-house with different dyes and then soaking them in various solvents. The resulting solutions were collected and analyzed using NMR relaxometry. Specifically, the effective transverse relaxation time constant, T2,eff, of each solution was estimated using a Carr–Purcell–Meiboom–Gill (CPMG) pulse sequence. Finally, the estimated time constants (i.e., measured signatures) were compared with a library of existing T2,eff data to detect and quantify the presence of unwanted dyes. The latter consists of data-driven models of transverse decay times for various concentrations of each water-soluble dye. The time required to analyze each sample using the proposed approach is dye-dependent but typically no longer than a few minutes. The analysis results can be used to generate warning flags if the detected dye concentrations violate widely accepted standards for food dyes. The proposed low-cost detection approach can be used in various stages of a produce supply chain, including consumer household.

A Quantitative Study of Photocatalytic Reduction of Cr(VI) by Operando Low-Field NMR Relaxometry

A Quantitative Study of Photocatalytic Reduction of Cr(VI) by Operando Low-Field NMR Relaxometry