Solid samples nuclear magnetic resonance

Although it is required to refine the above condition I in actuality, this rather simple but impressive prediction seems to have much stimulated the experiments on the electrical-conductivity measurement and the related solid-state properties in spite of technological difficulties in purification of the CNT sample and in direct measurement of its electrical conductivity (see Chap. 10). For instance, for MWCNT, a direct conductivity measurement has proved the existence of metallic sample [7]. The electron spin resonance (ESR) (see Chap. 8) [8] and the C nuclear magnetic resonance (NMR) [9] measurements have also proved that MWCNT can show metallic property based on the Pauli susceptibility and Korringa-like relation, respectively. On the other hand, existence of semiconductive MWCNT sample has also been shown by the ESR measurement [ 10], For SWCNT, a combination of direct electrical conductivity and the ESR measurements has confirmed the metallic property of the sample employed therein [11]. More recently, bandgap values of several SWCNT... 

Crosslinked polymer networks formed from multifunctional acrylates are completely insoluble. Consequently, solid-state nuclear magnetic resonance (NMR) spectroscopy becomes an attractive method to determine the degree of crosslinking of such polymers (1-4). Solid-state NMR spectroscopy has been used to study the homopolymerization kinetics of various diacrylates and to distinguish between constrained and unconstrained, or unreacted double bonds in polymers (5,6). Solid-state NMR techniques can also be used to determine the domain sizes of different polymer phases and to determine the presence of microgels within a poly multiacrylate sample (7). The results of solid-state NMR experiments have also been correlated to dynamic mechanical analysis measurements of the glass transition (1,8,9) of various polydiacrylates. 

Nuclear magnetic resonance (NMR) spectroscopy is most frequently used to analyze liquid samples, but in the magic angle spinning (MAS) mode, this spectroscopy can also be employed to characterize solid catalysts, zeolites in particular [116-120], For example, the 29Si NMR signal can... 

In an attempt to delineate the degree of preservation of lignin in pre-Tertiary coal, we examined numerous coalified wood samples ranging in age from Carboniferous to Cretaceous. The samples were initially screened by solid-state l C nuclear magnetic resonance to detect the possible presence of methoxyl carbon. Once such carbons were detected, the samples were subjected to analytical pyrolysis to determine the relative yields of methoxyphenols which would provide an indication of the state of preservation of the lignin-derived structu units. We report here on the identification of lignin-derived methoxyphenols in the coalified wood samples selected for analytical pyrolysis. 

Solid-state C variable-amplitude cross polarization magic-angle spinning (VACP/MAS) nuclear magnetic resonance (NMR) spectra were acquired for the sorbitol samples. Proton decoupling was achieved by a two-pulse phase modulation (TPPM) sequence. Identical C spectra were measured for the y-form sorbitol samples, and a representative spectrum is shown in Figure 9. 

Another method (ASTM D-4808) covers the determination of the hydrogen content of petroleum products, including vacuum residua, using a continuous-wave, low-resolution nuclear magnetic resonance spectrometer. Again, sample solubility is a criterion that will not apply to coal but will apply to coal extracts. More recent work has shown that proton magnetic resonance can be applied to solid samples and has opened a new era in coal analysis by this technique (de la Rosa et al., 1993 Jurkiewicz et al 1993). 

Both of these methods have been used for DOM isolation from major rivers and the surface ocean, and the general characteristics of these fractions of DOM are presented in Table I. The major C functional groups of humic substances and ultrafiltered DOM (UDOM) have been characterized by solid-state, cross-polarization magic angle spinning 13C nuclear magnetic resonance (NMR) spectroscopy. The samples of humic substances that were characterized by NMR spectroscopy were collected from the Amazon River... 

LC-NMR. Separations using reverse-phase (RP) liquid chromatography are potentially more powerful because samples can be studied without derivatization. Numerous attempts have been made to separate NOM and while most studies exhibit some degree of separation, to date the complete separation of a NOM sample has not been accomplished. Even only partial separation is possible, and it is worth to hyphenate a separation method with structure information-oriented analytical applications. Liquid chromatography combined with nuclear magnetic resonance and preliminary studies with solid-phase extraction were conducted on NOM isolated from freshwater and soil (Simpson et al., 2004). 

Figure 15.8. 13C CPMAS NMR spectra of the IHSS Pahokee Peat and a Canadian Grassland (black chernozem) soil and their corresponding humin samples. Reprinted from Simpson, M. J., and Johnson, P. C. E. (2006). Identification of mobile aliphatic sorptive domains in soil humin by solid-state 13C nuclear magnetic resonance. Environ. Toxi. Chem. 25, 52-57, with permission from the Society of Environmental Toxicology and Chemistry.

Simpson, M. J., and Preston, C. M. (2007). Soil organic matter analysis by solid-state 13C nuclear magnetic resonance spectroscopy. In Soil Sampling and Methods of Analysis. CRC Press, Boca Raton, FL, pp. 195-200. 

It is useful to emphasise from the outset that alternative techniques for investigating solid samples, other than NMR spectroscopy of the quadrupolar halogen nuclei, tend to be considered first this is likely due to the (perceived) difficulty of the technique and may be related to the issues of sensitivity and line broadening mentioned above. However, the information gained is often complementary, and hence solid state nuclear magnetic resonance (SS NMR) spectroscopy is primarily used when it can provide unique insight unavailable with other techniques. 

The water slurry of SP-300 was acidified to pH 2 with 10% HCL to obtain two forms of precipitates one was lumpy and the other was powder-like. After separation from the solution, each form of precipitate was dried. The former was designated as fraction I and the latter, fraction J. The solid product from SP-300 was acidified, separated from the solution and dried. Then the product was extracted with pyridine at room temperature with a solvent/sample ratio of 10. The soluble portion was called fraction K. Thus SP-300 was divided into four fractions fractions I, J, K, and Pyridine-Insoluble. Likewise, SP-320 was divided into four fractions fractions I Jf, K, and Pyridine-Insoluble. Figure 1 summarizes the procedures used in the preparation of all CDL products. Elemental compositions, molecular weight, nuclear magnetic resonance and infrared spectra were obtained for each major fraction. Details of the preparation of specific fractions of HVL-P and solubilization products and analyses can be found elsewhere (13,14). 

Pulsed nuclear magnetic resonance (pNMR) has become the preferred method for measuring the percentage of solid fat in a partly solidified fat sample in most parts of the world because of its speed, precision and utility (Kaylegian and Lindsay, 1994). In contrast to dilatometry, pNMR measures the true solid fat content (SFC) rather than an index of this. 

Nuclear Magnetic Resonance (NMR) [42]. When a sample (solid or liquid) consisting of nuclei of spin I and magnetization Mis placed in an external DC magnetic field H0, the Larmor frequency v0 (Hz, or cycles per second) for nuclear spin projection transitions Anti = 1 is... 

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