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951.
Conjugated linoleic acids (CLA) have been a subject of extensive investigation for their anticarcinogenic, hypolipidemic, antiatherosclerotic and immune-enhancing activities. Stability of CLA in foods has not received much attention by both academics and industry. Although CLA has shown many beneficial effects, its decomposition must be prevented when CLA in foods is processed, stored and transported. However, no study to date has addressed the stability of CLA in foods. The present study was carried out further to examine the stability of CLA in egg yolk during the storage and frying, using gas liquid chromatography (GLC) and silver ion high-performance liquid chromatography (Agt-HPLC). The eggs, containing 4.0% CLA per gramme of egg yolk, were 40s. Either storage for 6 months or frying for 40 s did not significantly change the composition of CLA in egg yolk. However, the degradation of CLA was statistically significant when the CLA components of egg yolk protected CLA from degradation. It is concluded that CLA is well preserved in egg before it is consumed. 相似文献
952.
18-Crown-6-tetracarboxylic acid (18C6H4) is a chiral selector with high selectivity for the enantioseparation of solutes bearing the primary amine function. This work presents the simultaneous separation of positional enantiomers of methyl-DL-tryptophans by using 18C6H4 as an additive to the background electrolyte. Separation conditions such as pH, the concentration of 18C6H4, and the applied voltages have critical inference on the simultaneous separation. The addition of cyclodextrins as anionic surfactants to the background electrolyte did not improve the separation. The selector-selectand interactions between 18C6H4 and the positional enantiomers have been investigated. It was observed that both the position and type of substituents contribute to the enantioselectivity. The migration order and resolution depended on the distance from the substituents to the asymmetric carbon of the enantiomers. 相似文献
953.
Nitrogen-15 labeled pyrroles have been prepared from commercially available 15N glycine or sodium nitrite using the Barton-Zard, Knorr, and Kleinspehn approaches. These pyrroles were used as intermediates in the synthesis of per-15N labeled porphyrins needed for the analysis and assignment of vibrational spectra for sedimentary porphyrins. Etioporphyrin-I was prepared via pyrromethene intermediates, while etioporphyrins II-V and a related tetrahydrobenzoporphyrin were synthesized via stepwise routes involving the copper(II) mediated cyclization of a,c-biladienes as the key step. Detailed analyses of both the proton and carbon-13 NMR spectra provide nitrogen-15 coupling constants for these important structures. 相似文献
954.
Upon the electrochemical oxidation of tris(2,2′-bipyridyl) ruthenium(II) [Ru(bpy)2+3] and hydroxyl carboxylic acids, for instance, citric acid, tartaric acid, malic acid, and
-gluconic acid, bright electrochemiluminescences (ECLs) were observed. Different luminescent reactions were presented depending on the applied potential. The light emission was mainly caused by the reaction between alkoxide radical ion and Ru(bpy)3+3below the potential +1.80 V (vs Ag/AgCl). The luminescence intensity obviously increased because of the more complex reaction process. The luminescence wavelength of 608 nm, which could be found either at higher potential than +1.80 V or in the potential range from +1.30 to +1.80 V, confirmed that ECL was caused by Ru(bpy)2+3*. The factors which affect the determination and HPLC separation of the four acids were also investigated. 相似文献
955.
Jingfei Luan Zhigang Zou Minghui Lu Guoyou Luan Yanfeng Chen 《Research on Chemical Intermediates》2006,32(1):31-42
In2BiTaO7 was synthesized using the solid-state reaction method and its photocatalytic properties were investigated. The results of
powder X-ray diffraction (XRD) indicated that the compound crystallizes in the pyrochlore-type structure, cubic system with
space group Fd-3m. The lattice parameter is 10.6972(1) ?. In addition, the compound shows strong optical absorption in the
visible region (λ > 420 nm) and the band gap of In2BiTaO7 was estimated to be about 2.47 eV. For the photocatalytic reaction, H2 or O2 evolution was observed from CH3OH/H2O or AgNO3 solution respectively with In2BiTaO7 as the photocatalyst under visible light irradiation, indicating that In2BiTaO7 is responsive to visible light for splitting water. Furthermore, the catalyst remained photoactive in the wavelength range
up to 510 nm. Photocatalytic degradation of methylene blue (MB) dye over the compound was further investigated under visible
light irradiation. The results showed that complete removal of aqueous MB could be achieved after irradiation for 135 min
over In2BiTaO7. Furthermore, under visible light irradiation In2BiTaO7 showed markedly higher catalytic activity compared to P-25 for MB photocatalytic degradation. 相似文献
956.
957.
Photosensitized oxidation of trialkylalkenes 2-methyl-2-pentene (1), 1-methylcyclohexene (2), trans-3-methyl-2-pentene (3), cis-3-methyl-2-pentene (4), and 2-methyl-2-butene (5) included in the internal framework of Na-ZSM-5 zeolites was investigated. The zeolite samples having adsorbed the alkenes were suspended in isooctane, and the sensitizer, tetraphenylporphyrin (TPP), was dissolved in the solution. Singlet oxygen produced in the solution diffused into the internal framework of the zeolites and reacted with alkenes. For all the substrates studied, the ene-type allylic hydroperoxides were obtained in a highly regioselective manner. The regiochemistry for 1-4 in favor of the allylic hydrogen abstraction from the largest substituents is in contrast to their photooxidation within the dye-supported zeolite Na-Y, where the secondary hydroperoxides are preferentially produced. The tight confinement of the alkenes within the narrow channels of the ZSM-5 zeolites is likely to be responsible for this selectivity. 相似文献
958.
959.
Gengliang Yang Zhiwei Li Dexian Wang Zhefeng Zhang Erdong Liu Yi Chen 《Chromatographia》2002,56(7-8):515-518
Summary A high-performance liquid chromatographic method was developed for the chiral separation of a new anti-diabetic agent, N-(trans-4-isopropylcyclohexylcarbonyl)-D-phenylalanine,
and its L-enantiomer. The separation was performed on a Sumichiral OA-3300 column. Optimized mobile phase was 0.025 mol.L−1 ammonium acetate in methanol solution. UV detection was at 210 nm. Baseline chiral separation was obtained within 12 minutes.
The detection limits are 80 pg for the D-enantiomer and 120 pg for the L-enantiomer. RSD of the method was below 1% (n=5). 相似文献
960.