NMR Spectrometer (nmr + spectrometer)

Distribution by Scientific Domains


Selected Abstracts


Research Article: Fingerprinting Analysis of Saposhnikovia divaricata using 1H Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid Chromatography

JOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2010
Yue-Yang Xin
The 1H nuclear magnetic resonance (1H NMR) fingerprints of fractionated non-polar and polar extracts (control substance for plant drug [CSPD] A and B) from the roots of 12 specimens of Saposhnikovia divaricata (Turcz.) Schischk were achieved with Fourier Transform (FT)-NMR spectrometer and assigned by comparison to each other and to the 1H NMR spectra of the isolated individual compounds. These fingerprints were found to be uniform in terms of the specificity for the implication of all 12 specimens being systematically of the same origin. The uniformity was further affirmed by high performance liquid chromatography (HPLC), which also revealed exactly identical specificity for the identified S. divaricata species with the 1H NMR appearances of corresponding CSPD on the part of the composition of characteristic constituents when comparing to corresponding individual compounds. This investigation unambiguously shows that the specific signals from the chemotaxonomically significant compounds of chromones and coumarins in S. divaricata are exhibited distinctively in the composite features of both 1H NMR fingerprints and HPLC profiles. The 1H NMR and HPLC profiles established can successfully be used as reference for the authentication of the origin of S. divaricata species as well as for chemotaxonomic studies. [source]


Fingerprinting Analysis of Rhizoma Chuanxiong of Commercial Types using 1H Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid Chromatography Method

JOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2009
Hai-Lin Qin
Abstract The 1H nuclear magnetic resonance (1H NMR) fingerprints of fractionated non-polar extracts (control substance for a plant drug (CSPD) A) from Rhizoma chuanxiong, the rhizomes of Ligusticum chuanxiong Hort., of seven specimens from different sources were measured on Fourier Transform (FT)-NMR spectrometer and assigned by comparing them with the 1H NMR spectra of the isolated pure compounds. The 1H NMR fingerprints showed exclusively characteristic resonance signals of the major special constituents of the plant. Although the differences in the relative intensity of the 1H NMR signals due to a discrepancy in the ratio of the major constituents among these samples could be confirmed by high performance liquid chromatography analysis, the general features of the 1H NMR fingerprint established for an authentic sample of the rhizomes of L. chuanxiong exhibited exclusive data from those special compounds and can be used for authenticating L. Chuanxiong species. [source]


23Na and 87Rb relaxation study of the structural phase transitions in the Tutton salts Na2Zn(SO4)26H2O and Rb2Zn(SO4)26H2O single crystals

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2010
Ae Ran Lim
Abstract The NMR spectrum, spin,lattice relaxation times, T1, and the spin,spin relaxation times, T2, for the 23Na and 87Rb nuclei in Tutton salts Na2Zn(SO4)26H2O and Rb2Zn(SO4)26H2O single crystals were determined by using an FT NMR spectrometer. The NMR spectrum and relaxation times for the 23Na and 87Rb nuclei in two crystals undergo significant changes near TC. These changes close to TC were the only detectable result of the structural transformation; the change is due to the fact that the electric field gradient value becomes 0. Especially, T1 and T2 for 87Rb in the Rb2Zn(SO4)26H2O crystals at high temperature have similar values on the order of milliseconds, which is indicative of a liquid-like system. The motion giving rise to this liquid-like behavior is probably related to superionic motion at high temperature. [source]


Identification of isomeric dicaffeoylquinic acids from Eleutherococcus senticosus using HPLC-ESI/TOF/MS and 1H-NMR methods

PHYTOCHEMICAL ANALYSIS, Issue 6 2002
Ari Tolonen
Abstract Liquid chromatography,electrospray time-of-flight mass spectrometry (HPLC-ESI/TOF/MS) and a novel NMR technique, developed to maximise the sensitivity obtained from the standard NMR spectrometer, have been applied to the identification of the phenolic constituents of Eleutherococcus senticosus. In addition, molecular modelling and dihedral bond angle calculations based on the vicinal 3JHH -coupling constants have been used in the unambiguous assignment of signals in the 1H-NMR spectra. 5,- O -Caffeoylquinic acid and three isomeric compounds, 1,,5,- O -dicaffeoylquinic acid, 3,,5,- O -dicaffeoylquinic acid and 4,,5,- O -dicaffeoylquinic acid, have been isolated and identified from a sample. The isolation and structure determination of the latter two compounds are reported for the first time from this plant. Copyright 2002 John Wiley & Sons, Ltd. [source]


NMR chemical shift measurements revisited: High precision measurements

CONCEPTS IN MAGNETIC RESONANCE, Issue 4 2007
P. Granger
Abstract Accurate chemical shifts are now accessible with high field NMR spectrometers. After the recall of the basic formulae, methods are proposed to measure chemical shifts with a high precision. Using two coaxial rotors at the magic angle, the necessary parameters used for correction are measured. The influence of different factors on the precision of the NMR measurements is discussed. Some proposals are given for MAS experiments used with solid-state samples. 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 184,193, 2007. [source]


1H NMR study of internal motions and quantum rotational tunneling in (CH3)4NGeCl3

MAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2008
K. J. Mallikarjunaiah
Abstract (CH3)4NGeCl3 is prepared, characterized and studied using 1H NMR spin lattice relaxation time and second moment to understand the internal motions and quantum rotational tunneling. Proton second moment is measured at 7 MHz as function of temperature in the range 300,77 K and spin lattice relaxation time (T1) is measured at two Larmor frequencies, as a function of temperature in the range 270,17 K employing a homemade wide-line/pulsed NMR spectrometers. T1 data are analyzed in two temperature regions using relevant theoretical models. The relaxation in the higher temperatures (270,115 K) is attributed to the hindered reorientations of symmetric groups (CH3 and (CH3)4N). Broad asymmetric T1 minima observed below 115 K down to 17 K are attributed to quantum rotational tunneling of the inequivalent methyl groups. Copyright 2007 John Wiley & Sons, Ltd. [source]


A new approach to automated first-order multiplet analysis

MAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2002
Sergey Golotvin
Abstract The dependence of the values of NMR spin,spin coupling constants on molecular conformation can be a valuable tool in the structure determination process. The continuing increase in the resonance frequency of modern NMR spectrometers allows an increasing number of resonances to be examined using first-order multiplet analysis. While this can easily be done for the simplest patterns (doublets, triplets, quartets), more complex patterns can be extremely difficult to analyze. The task of deducing the coupling constant values from a multiplet is the reverse process of generating a conventional splitting tree from a single line (chemical shift) by sequential branching using a given set of coupling constants. We present a simple, straightforward method of deducing coupling constant values from first-order multiplets based on a general inverted splitting tree algorithm but also including a peak intensity normalization procedure that utilizes multiplet symmetry and generates a set of possible first-order intensity distribution patterns. When combined with an inverted splitting tree algorithm, it is possible to find an intensity pattern that allows the deduction of a proper set of coupling constants. Copyright 2002 John Wiley & Sons, Ltd. [source]