13C solid-state NMR spectroscopy

Malcolm RE, Vaughan D (1979) Effects of humic acid fraction on invertase activities in plant tissues. Soil Biol Biochem 11 65-72 Malcolm RL (1989) Application of solid-state 13C NMR spectroscopy to geochemical studies of humic substances. In Hayes MHB, MacCarthy P, Malcolm RL, Swift RS (eds) Humic substances II. In search of structure. Wiley, Chichester, UK, pp 339-372... 

Solid state 13C NMR spectroscopy has emerged as a very useful tool for characterizing SOM (Kinchesh et al. 1995 Preston 1996). Several workers have reported that Koc of HOCs was linearly or exponentially related to the aromatic carbon contents of HAs or whole soils as determined by 13C NMR analysis (Ahmad et al. 2001 Chen et al. 1996 Chin et al. 1997 Gauthier et al. 1987 Perminova et al. 1999). The Koc value of humic materials can vary by as much as an order of magnitude, depending upon their origins (Fig. 1). 

The use of solid state 13C NMR spectroscopy along with elemental analysis provides useful information on the chemical composition of SOM samples. In assessing the influence of SOM composition on the partition of... 

Kolbl A, Kogel-Knabner I (2004) Content and composition of free and occuluded particulate organic matter in a differently textured arable Cambisol as revealed by solid-state 13C NMR spectroscopy. J Plant Nutr Soil Sci 167 45-53... 

In the present work, we use quantitative solid-state 13C NMR spectroscopy to study the polymerization process of multiacrylates and the effects of thermal history/aging on the free radical life in polymultiacrylates. 

Lorenz, K., Preston, C.M., Kandeler, E. 2006. Soil organic matter in urban soils Estimation of elemental carbon by thermal oxidation and characterization of organic matter by solid-state 13C NMR spectroscopy. Geoderma, 130, 312-323. 

More recently, Markovich et al. (91) utilized a combination of solid-state infra-red (IR) and NMR methods to study the amorphous to crystalline API transition of SCH 48461 in solid dispersion capsule formulations. In this illustrative study, dissolution testing initially revealed inter-and intralot variations of capsules stored under accelerated stability conditions (25°C/60% RH, 30°C/60% RH, and 40°C/80% RH). PXRD analysis could not explain the dissolution data being collected on lots stored at accelerated conditions and revealed no differences from original diffraction patterns. Two additional analytical techniques, attenuated total reflectance IR (ATR-IR) spectroscopy and solid-state 13C NMR spectroscopy, were employed to study the physical form in the actual solid dispersion formulations. 

Infrared spectroscopy was widely used in the second half of the 20th century, and this technique has allowed some advances to be made in awareness of functionalities in, and of complexes formed by, humic molecules. However, the greatest advances in determinations of functionalities, in aspects of compositions and structures, and now in aspects of humic interactions have been made since the introduction of solid-state 13C NMR spectroscopy (Wilson, 1987 Malcolm, 1989). Chapter 15 in this book (by Simpson and Simpson) has reviewed in detail the applications of NMR in the solid and liquid states to studies of compositions and interactions of NOM. We now have a good indication of the types of functionalities that compose HS, and combinations of modem NMR technologies and principal component analysis (PCA) techniques allow us to deduce the origins of some of the functionalities (Novotny et al., 2007). 

Baldock, J. A., Oades, J. M., Nelson, P. N., Skene, T. M., Golchin, A., and Clark, R (1997). Assessing the extent of decomposition of natural organic materials using solid-state 13C NMR spectroscopy. Aust. J. Soil Rese. 35,1061-1083. 

Samburova, V., Zenobi, R., and Kalberer, M. (2005). Characterization of high molecular weight compounds in urban atmospheric particles. Atmos. Chem. Phys. 5, 2163-2170. Sannigrahi, P., Sullivan, A. P, Weber, R. I, and Ingall, E. D. (2006). Characterization of water-soluble organic carbon in urban atmospheric aerosols using solid-state 13C NMR spectroscopy. Environ. Sci. Technol. 40, 666-672. 

Malcolm, R. L. (1989). Applications of solid-state 13C NMR spectroscopy to geochemical studies of humic substances. In Humic Substances II. In Search of Structure, Hayes, M. H. B., MacCarthy, P., Malcolm, R. L., and Swift, R. S., John Wiley and Sons Ltd., New York, 340-372. 

Sannigrahi, P, A.P. Sullivan, R.J. Weber, and E.D. Ingall. 2006. Characterization of water-soluble organic carbon in urban atmospheric aerosols using solid-state 13C NMR spectroscopy. Environ. Sci. Technol. 40 666-672. 

The mechanism of the accelerated sulfur vulcanisation of EPDM is probably similar to that of the highly unsaturated polydiene rubbers. The vulcanisation of EPDM has been studied with emphasis on the cure behaviour and mechanical and elastic properties of the crosslinked EPDM. Hardly any spectroscopic studies on the crosslinking chemistry of EPDM have been published, not only because of the problems discussed in Section 6.1.3 but also because of the low amount of unsaturation of EPDM relative to the sensitivity of the analytical techniques. For instance, high-temperature magic-angle spinning solid-state 13C NMR spectroscopy of crosslinked EPDM just allows the identification of the rubber type, but spectroscopic evidence for the presence of crosslinks is not found [72]. 

The chemical microstructures of cis-polyisoprene (HR) vulcanised with sulfur and N-t-butyl-2-benzothiazole sulfenamide (TBBS) accelerator were studied as a function of extent of cure and accelerator to sulfur ratio in the formulations by solid-state 13C NMR spectroscopy at 75.5 MHz [29]. Conventional (TBBS/Sulfur=0.75/2.38), semi-efficient (SEV=1.50/1.50) and efficient (EV=3.00/1.08) vulcanisation formulations were prepared, which were cured to different cure states according to the magnitude of increase in rheometer torque. The order and types of the sulfurisation products formed are constant in all the formulation systems with different accelerator to sulfur ratios. However, the amount of sulfurisation has been found to vary directly with the concentration of elemental sulfur. 

Solid-state 13C NMR spectroscopy was used to study accelerated [33] and unaccelerated [34] sulfur-vulcanisation and sulfur-donor (TMTD) [35] vulcanisation of czs-polybutadiene (BR). Olefinic and methylene carbons of the czs-BR repeating unit typically resonate at 129.5 and 27.5 ppm, respectively. The dominant products occurring in the vulcanisation... 

Microstructural changes of an accelerated sulfur vulcanisation of HR with TMTD/ZnO/ sulfur has been studied by solid-state 13C NMR spectroscopy [47]. The HR containing 2% isoprene and 98% isobutylene were formulated using EV and cured at 160 °C for several cure times. The resonances at 20.3 and 24.4 ppm, which are due to trans isoprene units in the HR, decrease with cure, while the resonances at 26.9 and 25.2 ppm which arise from cis isoprene units increase with cure times. The cis trans ratio increases up to a maximum ratio of approximately 4 1 at a cure time of 60 minutes. New resonances are observed at 15, 21, 23.6 and 49 ppm. The peak at 49 ppm is assigned to the mixture of the isoprene units in czs-IIR, polysulfidic Alt and polysulfidic Ale structures. The resonance peaks at 15, 21 and 23.6 ppm are assigned to the isoprene units in mono- and polysulfidic Bit, mono- and polysulfidic Blc and polysulfidic Alt structures, respectively. No reaction occurs in the isobutylene units. No migration of the double bond saturation, internal cyclisation or sulfurisation resulting in Clt and Clc structures is observed. 

Vulcanised SBR/EPDM diblends were quantitatively characterised by solid-state 13C NMR spectroscopy. The SBR/EPDM blend ratio can be determined as well as the czs-1,4, transit and vinyl-1,2 butadienes and styrene ratios in the SBR and the ethylene and propylene contents in the EPDM. No evidence for homo- and co-vulcanisation has been obtained in these systems. No evidences are found for the change in cisitrans ratio in the SBR upon the vulcanisation [52],... 

M. Lahaye, C. Rondeau-Mouro, E. Deniaud, and A. Buleon, Solid-state 13C NMR spectroscopy studies of xylans in the cell wall of Palmaria palmata (L. Kuntze, Rhodophyta), Carbohydr. Res., 338 (2003) 1559-1569. 

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