scholarly journals Determination of Diethyl Phthalate and Polyhexamethylene Guanidine in Surrogate Alcohol from Russia

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Yulia B. Monakhova ◽  
Thomas Kuballa ◽  
Jenny Leitz ◽  
Dirk W. Lachenmeier
Keyword(s):  
Diethyl Phthalate ◽  
Rapid Screening ◽  
Multivariate Curve Resolution ◽  
Spectroscopic Techniques ◽  
Eosin Y ◽  
H Nmr ◽  
Polyhexamethylene Guanidine ◽  
Hawthorn Extract ◽  
Nmr Methods

Analytical methods based on spectroscopic techniques were developed and validated for the determination of diethyl phthalate (DEP) and polyhexamethylene guanidine (PHMG), which may occur in unrecorded alcohol. Analysis for PHMG was based on UV-VIS spectrophotometry after derivatization with Eosin Y and1H NMR spectroscopy of the DMSO extract. Analysis of DEP was performed with direct UV-VIS and1H NMR methods. Multivariate curve resolution and spectra computation methods were used to confirm the presence of PHMG and DEP in the investigated beverages. Of 22 analysed alcohol samples, two contained DEP or PHMG.1H NMR analysis also revealed the presence of signals of hawthorn extract in three medicinal alcohols used as surrogate alcohol. The simple and cheap UV-VIS methods can be used for rapid screening of surrogate alcohol samples for impurities, while1H NMR is recommended for specific confirmatory analysis if required.

scholarly journals Intermolecular Interactions between Eosin Y and Caffeine Using 1H-NMR Spectroscopy

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Macduff O. Okuom ◽  
Mark V. Wilson ◽  
Abby Jackson ◽  
Andrea E. Holmes
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr Spectroscopy ◽  
Date Rape ◽  
Proton Exchange ◽  
Eosin Y ◽  
Club Drugs ◽  
Hydroxybutyric Acid ◽  
Color Changes ◽  
H Nmr ◽  
Nmr Methods

DETECHIP has been used in testing analytes including caffeine, cocaine, and tetrahydrocannabinol (THC) from marijuana, as well as date rape and club drugs such as flunitrazepam, gamma-hydroxybutyric acid (GHB), and methamphetamine. This study investigates the intermolecular interaction between DETECHIP sensor eosin Y (DC1) and the analyte (caffeine) that is responsible for the fluorescence and color changes observed in the actual array. Using 1H-NMR, 1H-COSY, and 1H-DOSY NMR methods, a proton exchange from C-8 of caffeine to eosin Y is proposed.

Structure of Thermally Modified Wood Studied by Liquid State NMR Measurements

Holzforschung ◽  
2002 ◽  
Vol 56 (5) ◽  
pp. 522-528 ◽  
Author(s):  
S. Hietala ◽  
S. L. Maunu ◽  
F. Sundholm ◽  
S. Jämsä ◽  
P. Viitaniemi
Keyword(s):  
Relaxation Times ◽  
Nmr Relaxation ◽  
Spectroscopic Techniques ◽  
H Nmr ◽  
Yield Information ◽  
Cell Dimensions ◽  
Relaxation Measurements ◽  
Nmr Methods ◽  
Thermally Modified Wood ◽  
Pfg Nmr

Summary Thermal modification is a technique to produce wood with increased dimensional stability and lower equilibrium moisture content. 2H NMR relaxation measurements and pulsed field gradient (PFG-NMR) methods are non-invasive spectroscopic techniques that can be used to measure the response of liquid confined in porous materials and yield information on the size and distribution of the pores. These methods were used to study the structure and changes in structure of thermally modified Scots pine wood. The 2H longitudinal relaxation measurements of wood samples at different moisture contents showed different relaxation times and relaxation time distribution in the thermally treated samples. The effect of the thermal treatments on the cell size in wood samples was studied by PFG-NMR measurements with different dwell times. The PFG-NMR measurements showed no clear change in the cell dimensions of the thermally modified samples compared with control samples taken from the same log.

scholarly journals Rapid Determination of Total Thujone in Absinthe Using 1H NMR Spectroscopy

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Yulia B. Monakhova ◽  
Thomas Kuballa ◽  
Dirk W. Lachenmeier
Keyword(s):  
Nmr Spectroscopy ◽  
Rapid Determination ◽  
Previous Method ◽  
Rapid Screening ◽  
H Nmr ◽  
Chromatographic Techniques ◽  
Liquid Liquid Extraction ◽  
Relative Standard ◽  
The Eu

1H NMR spectroscopy is utilized to quantify total thujone (sum of α- and β-isomers) in absinthe. For sample preparation, a simple dilution with buffer is required. Thujone produces a distinct peak of the CH2 group in the cyclopentanone moiety in the 2.13–2.11 ppm range. No overlap with other typical constituents such as anethole or fenchone occurs. The detection limit of 0.3 mg/L is adequate to control the EU maximum limit. The relative standard deviation was 6%, and linearity was observed from 1 to 100 mg/L. Applicability was proven by analysis of 69 authentic absinthes. The correlation between NMR and our previous method consisting of liquid-liquid extraction followed by GC/MS was significant (P<0.0001,R=0.93). The simple and cheap NMR method can be used for rapid screening of absinthes for total thujone content while chromatographic techniques are recommended for more specific (α- and β-thujone isomers) analysis if required.

scholarly journals NMR Methods to Characterize Protein-Ligand Interactions

2019 ◽  
Vol 14 (5) ◽  
pp. 1934578X1984929 ◽  
Author(s):  
Sanhita Maity ◽  
Ravi Kumar Gundampati ◽  
Thallapuranam Krishnaswamy Suresh Kumar
Keyword(s):  
Molecular Mechanisms ◽  
Structural Information ◽  
Rapid Screening ◽  
Biological Macromolecules ◽  
Spectroscopic Techniques ◽  
Binding Affinities ◽  
Binding Interactions ◽  
Protein Ligand Interactions ◽  
Ligand Interactions ◽  
Nmr Methods

Structural information pertaining to the interactions between biological macromolecules and ligands is of potential significance for understanding of molecular mechanisms in key biological processes. Recently, nuclear magnetic resonance (NMR) spectroscopic techniques has come of age and has widened its scope to characterize binding interactions of small molecules with biological macromolecules especially, proteins. NMR spectroscopy-based techniques are versatile due to their ability to examine weak binding interactions and for rapid screening the binding affinities of ligands with proteins at atomic resolution. In this review, we provide a broad overview of some of the important NMR approaches to investigate interactions of small organic molecules with proteins.

Elucidation of the structures of the hydridothiolato complexes WH(SC6H2Pri3-2,4,6)3(L)(PMe2Ph), L = PMe2Ph or pyridine, by NMR and X-ray techniques

1995 ◽  
Vol 73 (7) ◽  
pp. 1092-1101 ◽  
Author(s):  
Timothy E. Burrow ◽  
Alan J. Lough ◽  
Robert H. Morris ◽  
Raymond L. Richards
Keyword(s):  
X Ray Diffraction ◽  
Pyridine Ligand ◽  
Nmr Spectrum ◽  
X Ray ◽  
H Nmr ◽  
Pyridine Ligands ◽  
Trigonal Bipyramidal ◽  
Hydride Ligand ◽  
Nmr Methods

Measurement of the T1 values of the 31P nuclei in the unusual capped trigonal bipyramidal complexes WH(tipt)3(PMe2Ph)2 (1, tipt = SC6H2Pri3-2,4,6) and W(2H)(tipt)3(PMe2Ph)2 allows the determination of the phosphorus–hydride distance of 2.2 ± 0.2 Å and the P-W-H angle of about 62 ± 7°. An approximate location of the hydride on an S2P face is proposed on the basis of steric interactions. The crystal structure of WH(tipt)3-(NC5H5)(PMe2Ph) (2) is reported; the WS3NP core consists of a distorted trigonal bipyramidal system with the phosphine and pyridine ligands axial and the thiolate ligands equatorial. The hydride ligand was not located by X-ray diffraction but can be positioned on an open S2P face at an angle P-W-H of about 65°. The small P-W-H angle results in large 2J(H,P) couplings for 1 and 2. The 1H NMR spectrum of complex 2 is assigned by use of NOE and homodecoupling NMR methods. This complex has the same crowded structure in solution as in the crystalline state. The pyridine ligand, which is sandwiched between two tipt aryl groups, is hindered from rotating around the W—N bond. Keywords: molybdenum, tungsten, thiolate, hydride, NMR, NOE.

21,22-Disubstituted 18α,19βH-Ursane Derivatives with Oxabicyclooctane System in Ring E

1993 ◽  
Vol 58 (1) ◽  
pp. 173-190 ◽  
Author(s):  
Eva Klinotová ◽  
Jiří Klinot ◽  
Václav Křeček ◽  
Miloš Buděšínský ◽  
Bohumil Máca
Keyword(s):  
Spectral Data ◽  
Spin Systems ◽  
Coupling Constants ◽  
Complete Analysis ◽  
Nmr Spectrum ◽  
Proton Proton ◽  
H Nmr ◽  
Proton Coupling ◽  
C Nmr

Reaction of 3β-acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) and 20β,28-epoxy-21,22-dioxo-19α,19βH-ursan-3β-yl acetate (IIIb) with diazomethane afforded derivatives XII-XIV with spiroepoxide group in position 21 or 22, which were further converted into hydroxy derivatives XV and XVII. Ethylene ketals VIII-X were also prepared. In connection with the determination of position and configuration of the functional groups at C(21) and C(22), the 1H and 13C NMR spectral data of the prepared compounds are discussed. Complete analysis of two four-spin systems in the 1H NMR spectrum of bisethylenedioxy derivative Xb led to the proton-proton coupling constants from which the structure with two 1,4-dioxane rings condensed with ring E, and their conformation, was derived.

Determination of the Accurate Values of the Rate Constant and Thermodynamic Parameters for the Rotation About the C(sp2)-C(aryl) Bond; Adamantan-1-yl 3-Bromo-2,4,6-trimethylphenyl Ketone

1998 ◽  
Vol 63 (7) ◽  
pp. 955-966
Author(s):  
Eva Přibylová ◽  
Miroslav Holík
Keyword(s):  
Thermodynamic Parameters ◽  
Shape Analysis ◽  
Rate Constants ◽  
Line Shape ◽  
Microsoft Excel ◽  
Hindered Rotation ◽  
H Nmr ◽  
Line Shape Analysis ◽  
Coalescence Temperature

Four programs for the 1H NMR line shape analysis: two commercial - Winkubo (Bruker) and DNMR5 (QCPE 165) and two written in our laboratory - Newton (in Microsoft Excel) and Simtex (in Matlab) have been tested in order to get highly accurate rate constants of the hindered rotation about a single bond. For this purpose four testing criteria were used, two of them were also developed by us. As supplementary determinations the rate constants obtained for the coalescence temperature and for the thermal racemization of chromatographically separated enantiomers were used which fitted well the temperature dependence of the rate constants determined by the line shape analysis. As a test compound adamantan-1-yl 3-bromo-2,4,6-trimethylphenyl ketone was prepared and studied. It was shown that supermodified simplex method used in our algorithm (Simtex), though time consuming, gives the most accurate values of the rate constants and consequently the calculated thermodynamic parameters Ea, ∆H≠, and ∆S≠ lay in relatively narrow confidence intervals.

scholarly journals Interactions between 4-thiothymidine and water-soluble cyclodextrins: Evidence for supramolecular structures in aqueous solutions

2016 ◽  
Vol 12 ◽  
pp. 549-563 ◽  
Author(s):  
Vito Rizzi ◽  
Sergio Matera ◽  
Paola Semeraro ◽  
Paola Fini ◽  
Pinalysa Cosma
Keyword(s):  
Inclusion Complexes ◽  
Pyrimidine Ring ◽  
Protective Role ◽  
Supramolecular Structures ◽  
Water Soluble ◽  
Aqueous Environment ◽  
Spectroscopic Techniques ◽  
Guest Molecules ◽  
H Nmr ◽  
Cv Measurements

Since several years the inclusion of organic compounds (guests) within the hydrophobic cavity (host) of cyclodextrins (CDs) has been the subject of many investigations. Interestingly, the formation of inclusion complexes could affect the properties of the guest molecules and, for example, the influence of the delivery system can be a method to improve/change the photochemical behavior of the guest. In particular, very recent studies have shown the protective role of CDs preventing the degradation of the encapsulated guest. Starting from this consideration, in this work, only the structure and complexation mode of the inclusion complexes involving 4-thiothymidine (S4TdR, a known photosensitizer) and five CDs, namely 2-hydroxypropyl-α-cyclodextrin (2-HP-α-CD), 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD), 2-hydroxypropyl-γ-cyclodextrin (2-HP-γ-CD), heptakis-(2,6-di-O-methyl)-β-cyclodextrin (DIMEB CD) and heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB CD) were investigated by different spectroscopic techniques (UV–vis, FTIR–ATR, 1H NMR) and cyclic voltammetry analysis (CV). This work is necessary for a prospective research on the photoreactivity of S4TdR in aqueous environment and in the presence of CDs to prevent its degradation under irradiation. UV–vis, FTIR–ATR and CV measurements suggested the formation of supramolecular structures involving the employed CDs and mainly the pyrimidine ring of S4TdR. 1H NMR analyses confirmed such indication, unveiling the presence of inclusion complexes. The strongest and deepest interactions were suggested when TRIMEB and DIMEB CDs were studied. The S4TdR affinity towards CDs was also evaluated by using the Benesi–Hildebrand (B–H) equation at 25 °C employing CV and 1H NMR methods. The stoichiometry of the interaction was also inferred and it appears to be 1:1 for all examined CDs.

scholarly journals Diorganotin(iv) benzyldithiocarbamate complexes: synthesis, characterization, and thermal and cytotoxicity study

2020 ◽  
Vol 18 (1) ◽  
pp. 453-462
Author(s):  
Jerry O. Adeyemi ◽  
Damian C. Onwudiwe ◽  
Nirasha Nundkumar ◽  
Moganavelli Singh
Keyword(s):  
Cell Lines ◽  
Human Tumor ◽  
Complexation Reaction ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
Human Tumor Cell Lines ◽  
H Nmr ◽  
Cytotoxicity Studies ◽  
Final Residue ◽  
Mcf 7

AbstractAmmonium benzyldithiocarbamate, represented as NH4L, was prepared and used in the complexation reaction involving three organotin(iv) salts, represented as R2SnCl2 (R = CH3, C4H9, and C6H5). The structures of the synthesized complexes [(CH3)2SnL2] (1), [(C4H9)2SnL2] (2), and [(C6H5)2SnL2] (3) were established using various spectroscopic techniques (Fourier transform infrared spectroscopy, 1H NMR, 13C NMR, and 119Sn NMR) and elemental analysis. Thermal decomposition of the complexes using thermogravimetric analysis under nitrogen showed no definite pathway in the pattern of the complexes even though they are structurally related. X-ray diffraction studies of the final residue showed a common diffraction pattern for the complexes and confirmed SnS as the product of the thermal treatment. Cytotoxicity studies of these complexes against the human tumor cell lines (HeLa and MCF-7) compared favorably with the used standard 5-fluorouracil drug, with complexes 2 and 3 showing very good activity toward the used cell lines.

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