A NMR method for the analysis of mixtures of alkanes with different deuterium substitutions

Loaiza, Alfonso; Borchardt, Dan; Zaera, Francisco

doi:10.1016/s1386-1425(97)00159-5

Cited by 15 publications

(14 citation statements)

References 15 publications

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“…However, some additional uncertainty is introduced in the experiment with the light alkane because of the large signals from the C 2 D 4 ϩ ion (responsible for ϳ95% of the intensity of the 16 Da peak). In any case, the results for the C 2 H 6 ϩ D 2 mixture are in excellent agreement with previous analysis using 13 C NMR (30% CD 2 HCH 3 :70% CDH 2 CDH 2 ) [7,12].…”

Section: Resultssupporting

confidence: 90%

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Regiospecificity in deuterium labeling determined by mass spectrometry

Loaiza

Zaera

2004

J. Am. Soc. Mass Spectrom.

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Several mass spectrometry methods were explored to determine the regiospecificity of deuterium substitutions in hydrocarbon mixtures. The case investigated in this work was that of ethane mixtures obtained by catalytic H™D exchange between either C 2 H 6 and D 2 or C 2 D 6 and H 2 over platinum surfaces. A total of ten isotopologs are possible, and were indeed detected in all cases. Deconvolution of low-resolution mass spectra was found sufficient to determine the composition of the gas mixtures in terms of the total number of deuterium substitutions, but not to identify symmetric versus asymmetric substitutions in the C 2 D 2 H 4 , C 2 D 3 H 3 , and C 2 D 4 H 2 products. High-resolution mass spectrometry allowed the separation of the intensities due to C 2 X 4 ϩ fragments from those from molecular C 2 X 6 ϩ signals (X ϭ H or D), and with that for a more accurate determination of the composition of the mixtures. Relative probabilities were determined for the symmetric versus asymmetric removal of X 2 from C 2 X 6 ϩ ions and for isotope scrambling in the mass spectrometer, and with that information fairly good cracking patterns were then calculated for the C 2 X 4 ϩ fragments produced by each individual pure C 2 X 6 isotopologue. However, total deconvolution of all ten components in the ethane mixtures obtained by H™D exchange catalysis was beyond the experimental accuracy of the measurements. Tandem mass spectrometry/collision-induced decomposition mass spectrometry (MS/CID-MS) proved more useful for this task. In particular, it was possible to determine the proportion of symmetric versus asymmetric double H™D exchange in samples for which the total ethane-d 2 (in the case of C 2 H 6 ϩ D 2 ) or ethane-d 4 (with C 2 D 6 ϩ H 2 ) amounted to only ϳ3% on the ethane mix. A comparison with other analytical methods, NMR in particular, is provided. (J Am Soc Mass Spectrom 2004, 15, 1366 -1373

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Section: Resultssupporting

confidence: 90%

“…It should be noted that there are alternative methods for the determination of isotopic substitutions. In particular, we were quite successful in the past with the characterization of our ethane mixtures using NMR [7,12]. Nevertheless, we see the two approaches as complementary.…”

Section: Discussionmentioning

confidence: 94%

Regiospecificity in deuterium labeling determined by mass spectrometry

Loaiza

Zaera

2004

J. Am. Soc. Mass Spectrom.

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“…[9] Finally, ESI-MS analysis provided the expected value for the molecular ion of the proposed formulation of 3. The formation of 3 is puzzling.…”

Section: Angewandte Chemiementioning

confidence: 99%

A Chromium Ethylidene Complex as a Potent Catalyst for Selective Ethylene Trimerization

et al. 2011

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“…NMR spectroscopy is a powerful analytical tool for identification, quantification and investigation of the chemical composition of carbohydrate compounds in the extracts of a given sample [27][28][29][30]. Moreover, a proton nuclear magnetic resonance ( 1 H-NMR) spectroscopy is inherently a quantitative analytical method as the intensity of the NMR peak is proportional to the concentration of the H nuclei.…”

Section: Introductionmentioning

confidence: 99%

Advanced characterization of dissolved organic matter released by bloom-forming marine algae

Rehman¹,

Jeong²,

Tabatabai³

et al. 2017

Desalination and Water Treatment

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a b s t r a c tAlgal organic matter (AOM), produced by marine phytoplankton during bloom periods, may adversely affect the performance of membrane processes in seawater desalination. The polysaccharide fraction of AOM has been related to (bio)fouling in micro-filtration and ultrafiltration, and reverse osmosis membranes. However, so far, the chemical structure of the polysaccharides released by bloom-forming algae is not well understood. In this study, dissolved fraction of AOM produced by three algal species (Chaetoceros affinis, Nitzschia epithemoides and Hymenomonas spp.) was characterized using liquid chromatography-organic carbon detection (LC-OCD) and fluorescence spectroscopy. Chemical structure of polysaccharides isolated from the AOM solutions at stationary phase was analyzed using proton nuclear magnetic resonance ( 1 H-NMR). The results showed that production and composition of dissolved AOM varied depending on algal species and their growth stage. AOM was mainly composed of biopolymers (BP; i.e., polysaccharides and proteins [PN]), but some refractory substances were also present. 1 H-NMR spectra confirmed the predominance of carbohydrates in all samples. Furthermore, similar fingerprints were observed for polysaccharides of two diatom species, which differed considerably from that of coccolithophores. Based on the findings of this study, 1 H-NMR could be used as a method for analyzing chemical profiles of algal polysaccharides to enhance the understanding of their impact on membrane fouling.

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A NMR method for the analysis of mixtures of alkanes with different deuterium substitutions

Cited by 15 publications

References 15 publications

Regiospecificity in deuterium labeling determined by mass spectrometry

Regiospecificity in deuterium labeling determined by mass spectrometry

A Chromium Ethylidene Complex as a Potent Catalyst for Selective Ethylene Trimerization

Advanced characterization of dissolved organic matter released by bloom-forming marine algae

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