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El-Awad, A.M.

doi:10.1023/a:1010137313622

Cited by 15 publications

(7 citation statements)

References 20 publications

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“…The use of new computational techniques are essential to provide a complete understanding of the cleavage site and mechanisms channels after the MS fragmentation, as it has been shown for phytylated chlorophylls. The application of new methods of analysis able to determine new product ions is essential for estimation of natural components in living organisms, as they can be unique probes for adulteration control [37] and metabolomics [38,39].…”

Section: Discussionmentioning

confidence: 99%

“…When starting from a determined initial concentration, positive results were obtained for Mg 2+ -free derivatives, but not for the metal-containing samples, which showed a different behavior with temperature regimes, as well as the final intended standard which is more prone to oxidation in the case of Mg 2+ -containing derivatives. Several kinetic studies developed to measure the thermal stability of metal complexes show that the activation energy of the complex is relatively low, indicating the autocatalytic effect of the metal ion on the thermal decomposition of the complex [37] as overcome with a fine-tuning of the reaction conditions to heat-sensitive compounds or by increasing the substrate concentration, although as stated before, it is not convenient considering the limited availability of commercial chlorophyll standards especially for chlorophyll-b.…”

Section: Preparation and Isolation Of Chlorophyll Standardsmentioning

confidence: 99%

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Development of an accurate and high-throughput methodology for structural comprehension of chlorophylls derivatives. (I) Phytylated derivatives

Chen

Ríos

Pérez‐Gálvez

et al. 2015

Journal of Chromatography A

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Phytylated chlorophyll derivatives undergo specific oxidative reactions through the natural metabolism or during food processing or storage, and consequently pyro-, 13(2)-hydroxy-, 15(1)-hydroxy-lactone chlorophylls, and pheophytins (a and b) are originated. New analytical procedures have been developed here to reproduce controlled oxidation reactions that specifically, and in reasonable amounts, produce those natural target standards. At the same time and under the same conditions, 16 natural chlorophyll derivatives have been analyzed by APCI-HPLC-hrMS(2) and most of them by the first time. The combination of the high-resolution MS mode with powerful post-processing software has allowed the identification of new fragmentation patterns, characterizing specific product ions for some particular standards. In addition, new hypotheses and reaction mechanisms for the established MS(2)-based reactions have been proposed. As a general rule, the main product ions involve the phytyl and the propionic chains but the introduction of oxygenated functional groups at the isocyclic ring produces new and specific productions and at the same time inhibits some particular fragmentations. It is noteworthy that all b derivatives, except 15(1)-hydroxy-lactone compounds, undergo specific CO losses. We propose a new reaction mechanism based in the structural configuration of a and b chlorophyll derivatives that explain the exclusive CO fragmentation in all b series except for 15(1)-hydroxy-lactone b and all a series compounds.

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Section: Discussionmentioning

confidence: 99%

Section: Preparation and Isolation Of Chlorophyll Standardsmentioning

confidence: 99%

Development of an accurate and high-throughput methodology for structural comprehension of chlorophylls derivatives. (I) Phytylated derivatives

Chen

Ríos

Pérez‐Gálvez

et al. 2015

Journal of Chromatography A

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“…Therefore, in this work, we focused on the mechanism of step one [30]. Based on the results of former researchers [14,31] and our present work, a hypothetical mechanism of the first step of LiClO 4 decomposition of the Ce x Cu 1−x O 1x catalyst is proposed, as shown in Fig. 8.…”

Section: G Hypothetic Mechanism Analysis Of Liclo 4 Decompositionmentioning

confidence: 73%

Catalyst for Lithium Perchlorate Decomposition

Zhang

Yan

Qiu

et al. 2015

Journal of Propulsion and Power

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The use of metal oxide additives to modify the ability of solid propellants and other energetic materials has been the topic of much study. This work reports the enhancement of the decomposition of lithium perchlorate (LiClO 4 ) by means of employing Ce x Cu 1−x O 1x as a catalyst. The Ce x Cu 1−x O 1x composite catalysts synthesized through the collosol-gelling method with different mole ratios were designed to strongly enhance LiClO 4 decomposition through comparison with blank tests. The synthesized catalysts were characterized by scanning electron microscope, Brunauer-Emmett-Teller, x-ray diffraction, x-ray photoelectron spectra, and H 2 -TPR analyses. Results showed that a solid solution was formed in the Ce x Cu 1−x O 1x catalysts. The Ce x Cu 1−x O 1x composite catalysts showed more lattice defects, smaller crystallites, larger surface area, and more oxygen vacancies than pure CuO and CeO 2 samples because of the interaction of Ce and Cu ions. Lattice defects, especially the reduced surface sites (that is, Ce 3 , Cu , and oxygen vacancies), played dominant roles in catalytic reactions of LiClO 4 decomposition. In addition, a hypothetical mechanism for LiClO 4 catalytic decomposition of the Ce x Cu 1−x O 1x catalyst was proposed.

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“…The kinetic and thermodynamic parameters viz order of reaction (n), energy of activation (E a ), pre-exponential factor (z), entropy of activation (ΔS) and free energy change (ΔG) together with correlation coefficient (r) for non-isothermal decomposition of metal complexes have been determined by Horowitz-Metzer (HM) approximation method and Coats-Redfern integral method [29,24]. …”

Section: Kinetic Calculationsmentioning

confidence: 99%