A high-performance liquid chromatographic (HPLC) fingerprint of Chinese Angelica (CA) was developed basing on the consistent chromatograms of 40 CA samples (Angelica sinensis (Oliv.) Diels). The unique properties of this HPLC fingerprints were validated by analyzing 13 related herbs including 4 Japanese Angelicae Root samples (JA, A. acutiloba Kitagawa and A. acutiloba Kitagawa var. sugiyame Hikino), 6 Szechwan Lovage Rhizome samples (SL, Ligusticum chuanxiong Hort.) and 3 Cnidium Rhizome samples (CR, Cnidium officinale Makino). Both correlation coefficients of similarity in chromatograms and relative peak areas of characteristic compounds were calculated for quantitative expression of the HPLC fingerprints. The amount of senkyunolide A in CA was less than 30-fold of that in SL and CR samples, which was used as a chemical marker to distinguish them. JA was easily distinguished from CA, SL and CR based on either chromatographic patterns or the amount of coniferyl ferulate. No obvious difference between SL and CR chromatograms except the relative amount of some compounds, suggesting that SL and CR might have very close relationship in terms of chemotaxonomy. Ferulic acid and Z-ligustilide were unequivocally determined whilst senkyunolide I, senkyunolide H, coniferyl ferulate, senkyunolide A, butylphthalide, E-ligustilide, E-butylidenephthalide, Z-butylidenephthalide and levistolide A were tentatively identified in chromatograms based on their atmospheric pressure chemical ionization (APCI) MS data and the comparison of their UV spectra with those published in literatures. 相似文献
The decomposition kinetic behaviors of methane hydrates formed in 5 cm3 porous wet activated carbon were studied experimentally in a closed system in the temperature range of 275.8-264.4 K. The decomposition rates of methane hydrates formed from 5 cm3 of pure free water and an aqueous solution of 650 g x m(-3) sodium dodecyl sulfate (SDS) were also measured for comparison. The decomposition rates of methane hydrates in seven different cases were compared. The results showed that the methane hydrates dissociate more rapidly in porous activated carbon than in free systems. A mathematical model was developed for describing the decomposition kinetic behavior of methane hydrates below ice point based on an ice-shielding mechanism in which a porous ice layer was assumed to be formed during the decomposition of hydrate, and the diffusion of methane molecules through it was assumed to be one of the control steps. The parameters of the model were determined by correlating the decomposition rate data, and the activation energies were further determined with respect to three different media. The model was found to well describe the decomposition kinetic behavior of methane hydrate in different media. 相似文献
Nanoporous alumina membranes, loaded with palladium and ruthenium nanoparticles of various size, were used for gas phase hydrogenation of 1, 3‐butadiene and for oxidation of carbon monoxide, respectively. Those membranes contain 109 ‐ 1011 pores per cm2, all running perpendicular to the surface. Membrane discs of 20 mm in diameter and only 60 μm thick, incorporated in a reactor in which the reactants can be pumped in a closed circuit through the pores, turned out to very actively catalyze hydrogenation of butadiene (Pd) and oxidation of CO (Ru). The activity of the Pd catalysts depends characteristically on the particles size, the gas flow, and of the educts ratio. As could be expected, larger particles are less active than smaller ones, whereas increasing gas flows in case of hydrogenation accelerates the reactions. Excessive hydrogen reduces selectivity with respect to the various butenes, but favours formation of butane. 相似文献
N‐(2‐Chlorobenzyl)‐1,2,3,4‐tetrahydroisoquinoline‐1,3‐dione, C16H12ClNO2, crystallizes in P21/n with three crystallographically independent molecules in the asymmetric unit, which differ slightly in conformation, N‐(2‐bromo‐4‐methylphenyl)‐1,2,3,4‐tetrahydroisoquinoline‐1,3‐dione, C16H12BrNO2, crystallizes in P21/n with one molecule in the asymmetric unit andN‐(2,3‐dichlorophenyl)‐1,2,3,4‐tetrahydroisoquinoline‐1,3‐dione, C15H9Cl2NO2, crystallizes in P21/c with one molecule in the asymmetric unit. In all three structures, the heterocyclic rings adopt approximately planar conformations. The pyridine rings are orthogonal to the substituted phenyl rings. In all three structures, the crystal packing is stabilized by intermolecular C—H?O hydrogen bonds. 相似文献
The cover picture shows that sequential 1,1‐dihydrosilylation of terminal aliphatic alkynes with primary silanes enabled by one earth‐abundant cobalt catalyst has been developed. This protocol is operationally simple using readily available aliphatic alkynes, including simple acetylene and complex drug derivative, for efficient access to valuable gem‐bis(dihydrosilyl)alkanes in highly regioselective and atom‐economic manners. Corresponding asymmetric transformations are achieved with excellent enantioselectivities. More details are discussed in the article by Lu et al. on page 457–461.