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51.
高效液相色谱-核磁共振联用技术及其应用 总被引:3,自引:0,他引:3
高效液相色谱-核共共振在线联用技术是同时进行未知混合物的分离和结构鉴定的量好手段之一。详细介绍了在HPLC-NMR联用技术中H谱的分辨率,检测限手多重溶剂峰抑制的最新进展,并简要评述了其它分离方法与NMR联用情况。 相似文献
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Solvent Suppression in Intermolecular Magnetic Resonance Spectra Multiple-Quantum Coherence Nuclear with Only z-axis Gradients
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The solvent peak in the intermolecular multiple-quantum coherence spectra can be suppressed by either applying pulse field gradients or spinning sample along the magic angle direction (φ = 54.7). However, these two methods also suppress the signals of the solute. We design two pulse sequences with only z-axis gradients to suppress the solvent peak without reducing the intensity of solute signals. Compared to the former pulse sequence, the latter pulse sequence is insensitive to the imperfection of pulse flip angles. When the flip angles of the second pulse sequence are purposely deviated 1/10 from the optimal values, the solvent peak is still weak. Theoretical expressions, experimental observations and computer simulations demonstrate that the two methods can be used to effectively suppress solvent peak in intermolecular multiple-quantum coherence spectra. 相似文献
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Apparent diffusion behaviour of intermolecular double-quantum coherence modulated by a distant dipolar field in solution NMR
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A modified correlated spectroscopy (COSY) revamped with
asymmetric Z-gradient echo detection sequence was designed to
investigate the influence of diffusion behaviour on intermolecular
double-quantum coherence signal attenuation during the
pre-acquisition period. Theoretical formulas were deduced and
experimental measurements and simulations were performed. It is
found that the diffusion behaviour of intermolecular double-quantum
coherence in the pre-acquisition period may be different from that of
conventional single-quantum coherence, depending on the relative
orientation of diffusion weighting gradients to coherence selection
gradients. When the orientation of the diffusion weighting gradients is
parallel or anti-parallel to the orientation of the coherence
selection gradients, the diffusion is modulated by the distant
dipolar field. This study is helpful for understanding the signal
properties in intermolecular double-quantum coherence magnetic
resonance imaging. 相似文献
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在合成和表征了一系列新的异核异价三核过渡金属羧酸配合物[Fe2IMIO)-(OOCC2H5)6L3](M=Co,Ni,Mn;L=C5H5N,H2O)的基础上,利用多种NMR技术并结合UV谱研究了这些配合物在不同溶剂介质和温度下的谱学特征和动力学性质.利用谱峰积分比例、线宽、相同骨架分子的配体取代和纵向弛豫时间对1H NMR谱进行了归属.实验结果表明:这类配合物的金属离子间通过中心氧桥存在一定的反铁磁相互作用,从而在整体上削弱了顺磁性的影响,仍能观察到NMR谱.实验还发现这些配合物在CD3CN和DMSO)溶剂中的结构与晶体结构一致,而在水中则分解为金属离子、羧酸盐和吡啶.这些结果有助于指导类似配合物的合成. 相似文献
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Monitoring the formation of oil–water emulsions with a fast spatially resolved NMR spectroscopy method
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In the present study, a fast chemical shift imaging(CSI) method has been used to dynamically monitor the formation of oil–water emulsions and the phase separation process of the emulsion phase from the excessive water or oil phase on the molecular level. With signals sampled from series of small voxels simultaneously within a few seconds, high-resolution one-dimensional(1D) ~1H nuclear magnetic resonance(NMR) spectra from different spatial positions for inhomogeneous emulsion systems induced by susceptibility differences among components can be obtained independently. On the basis of integrals from these ~1H NMR spectra, profiles obtained explicitly demonstrate the spatial and temporal variations of oil concentrations. Furthermore, the phase separation time and the length of the oil–water emulsion phase are determined. In addition, effects of oil types and proportions of the emulsifier on the emulsification states are also inspected. Experimental results indicate that 1D PHASICS(Partial Homogeneity Assisted Inhomogeneity Correction Spectroscopy) provides a helpful and promising alternative to research on dynamic processes or chemical reactions. 相似文献