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991.
W. Gołkiewicz 《Chromatographia》1986,21(5):259-264
Summary Equations describing multi-step gradient elution with a mobile phase of constant composition in each step were derived. These
equations useful for calculating the retention volumes in both gradient HPLC and TLC were derived on the basis of the relationship
between the isocratic capacity factor and the volume fraction of the organic modifier. The validity of the equations was experimentally
verified in a LiChrosorbRP-18-water/methanol system for 11 methyl- and chlorobenzenes and phenols. A satisfactory agreement
between the theoretical and experimental k′ values was found. 相似文献
992.
It is well known that porphyrin derivatives play a key role in the primary process of photo-synthesis[1], in which porphyrins directly absorb the sunlight or indirectly acquire excitation en-ergy from light-harvesting antenna system to reach their excited state, and then donate electrons to quinone acceptors to yield a series of charge-separated species. In general, only first singlet ex-cited state of porphyrins is involved in energy transfer process[2]. However, highly excited state (S2 stat… 相似文献
993.
994.
995.
Afarin Moezzi Marylin M. Olmstead Doris C. Pestana Philip P. Power 《无机化学与普通化学杂志》1995,621(11):1933-1938
The reaction of either Li2PPh or Li2AsPh with the diborane(4) derivative B2(NMe2)2Br2 affords the compounds [PhP(BNMe2)2]2 ( 1 ) or [PhAs(BNMe2)2]2 ( 2 ) in good yield. Both 1 and 2 have cyclic structures featuring non-planar P2B4 or As2B4 six-membered rings which have chair configurations. Although all four borons in each ring have planar coordination, the two phosphorus or arsenic centers have different degrees of pyramidalization. Bond distances within the rings indicate that the B? B, B? P or B? As bonds are single, whereas the exo-B? N bond lengths are consistent with significant π-bonding. The ring structures of 1 and 2 are in sharp contrast to the related boron-nitrogen species (t-BuN)2N4Me4 which has a nido-N2B4 framework. The attempted synthesis of the nitrogen analogue of 1 or 2 by using a similar approach did not result in the isolation of [PhN(BNMe2)2]2, instead the tetramino diborane(4) species [B(NMe2)NHPh]2 ( 3 ), which has a structure similar to other tetramine diborane(4) compounds, was isolated. 相似文献
996.
A flow-electrolytic cell containing a strand of carbon fibers has been designed and characterized for use in a voltammetric detector for high-performance liquid chromatography. The detector was used for determination of triclosan (2,4,4-trichloro-2-hydroxydiphenyl ether) in rabbit serum and urine. Analysis of rabbit serum and urine 1 day and 1 to 5 days, respectively, after ingestion of oral triclosan revealed that the concentration of triclosan was higher than for control serum and urine. The concentration reached maximum levels after 6 h and 34 h or 44 h in serum and urine, respectively. When triclosan was determined in rabbit samples with the method proposed the results obtained were comparable with those obtained by high-performance liquid chromatography with ultraviolet detection. 相似文献
997.
A simple procedure for the determination of manganese in different sections of human brain samples by graphite furnace atomic absorption spectrometry has been developed. Brain sections included cerebellum, hypothalamus, frontal cortex, vermix and encephalic trunk. Two sample preparation procedures were evaluated, namely, slurry sampling and microwave-assisted acid digestion. Brain slurries (2% w/v) could be prepared in distilled, de-ionized water, with good stability for up to 30 min. Brain samples were also digested in a domestic microwave oven using 5 ml of concentrated HNO3. A mixed palladium+magnesium nitrate chemical modifier was used for thermal stabilization of the analyte in the electrothermal atomizer up to pyrolysis temperatures of 1300 °C, irrespective of the matrix. Quantitation of manganese was conducted in both cases by means of aqueous standards calibration. The detection limits were 0.3 and 0.4 ng ml−1 for the slurry and the digested samples, respectively. The accuracy of the procedure was checked by comparing the results obtained in the analysis of slurries and digested brain samples, and by analysis of the NIST Bovine Liver standard reference material (SRM 1577a). The ease of slurry preparation, together with the conventional set of analytical and instrumental conditions selected for the determination of manganese make such methodology suitable for routine clinical applications. 相似文献
998.
Two novel quassinoids, javanicolides A and B, and one novel quassinoid glucoside, javanicoside A were isolated from the seeds of Brucea javanica Merr. (Simaroubaceae), along with four known quassinoids, yadanziolides A and D, and bruceins D and E, and two known quassinoid glucosides, yadanziosides D and L. Their structures were elucidated by the analysis of spectral data and chemical evidence. 相似文献
999.
Dependence of Performance of Organic Light-emitting Devices on Sheet Resistance of Indium-tin-oxide Anodes 总被引:2,自引:0,他引:2
ZHOU Liang ZHANG Hong-jie YU Jiang-bo MENG Qing-guo PENG Chun-yun LIU Feng-yi DENG Rui-ping PENG Ze-ping LI Zhe-feng 《高等学校化学研究》2006,22(4):427-431
IntroductionIndium-tin-oxide(ITO) has been widely used asthe anode material in organic light-emitting devices(OLEDs) because of its high transmittance in the visi-ble region and low electrical resistivity. In the pastyears, many investigations focused on … 相似文献
1000.
The thermal decomposition of some M
2
I
HPO3 (M-Li, Na, K) phosphites under nitrogen atmosphere was investigated. A stepwise mechanism of thermal decomposition has been proposed.
Zusammenfassung Es wurde die thermische Zersetzung von Phosphiten M 2 I HPO3 (M-Li, Na, K) in Stickstoffatmosphere untersucht. Die Schritte des Mechanismus der thermischen Zersetzung wurden vorgeschlagen.相似文献