排序方式: 共有27条查询结果,搜索用时 31 毫秒
1.
Tyihk Ern Mricz gnes M. Ott Pter G. Hajnos Michal L. Gowniak Kazimierz 《平面色谱法杂志一现代薄层色谱法》2008,21(5):331-336
JPC – Journal of Planar Chromatography – Modern TLC - The accumulation of hydrogen peroxide (H2O2) is an early and crucial step in paclitaxel-induced cancer cell death before commitment... 相似文献
2.
Sajewicz Mieczysław Wojtal Łukasz Hajnos Michał Waksmundzka-Hajnos Monika Kowalska Teresa 《平面色谱法杂志一现代薄层色谱法》2010,23(4):270-276
JPC – Journal of Planar Chromatography – Modern TLC - In a previous paper we discussed the possibility of fractionating the essential oils of different sage species by low-temperature... 相似文献
3.
Cieśla L Bogucka-Kocka A Hajnos M Petruczynik A Waksmundzka-Hajnos M 《Journal of chromatography. A》2008,1207(1-2):160-168
There are a lot of taxonomic classifications of the genus Heracleum, and many authors indicate they need revision. Morphological identification is difficult to perform, as there are only few characteristic differences between each Heracleum species, varieties and forms. Furanocoumarins are characteristic compounds for the Apiaceae family, and they can be found in the whole genus in large quantities. Despite this fact, it is difficult to use the furanocoumarin profiles of plants, for their discrimination, as furanocoumarins are difficult to separate, due to their similar chemical structures and physicochemical properties. In this paper, a new, simple method is proposed for the discrimination of selected species, varieties and forms of the genus Heracleum. Thin-layer chromatography (TLC) with an adsorbent gradient (unmodified silica gel+octadecylsilica wettable with water) enables complete separation of the structural analogues. The proposed method gives the possibility to distinguish selected species, varieties and forms of the Heracleum genus, as they produce distinctive furanocoumarin fingerprints. The method is characterised by high specificity, precision, reproducibility and stability values. It is for the first time that graft TLC is used for constructing fingerprints of herbs. The complete separation of ten structural analogues, by combining gradient TLC with the unidimensional multiple development technique, has not been reported yet. 相似文献
4.
Petruczynik A Waksmundzka-Hajnos M Michniowski T Plech T Tuzimski T Hajnos ML Gadzikowska M Józwiak G 《Journal of chromatographic science》2007,45(7):447-454
Selected alkaloids are chromatographed on cyanopropyl-silica thin layers using various nonaqueous and aqueous eluents. Because of the strong retention of these basic compounds, nonaqueous eluents containing medium polar diluents, strongly polar modifiers, and silanol blockers (ammonia or diethylamine) are required for separation. Likewise, aqueous eluents containing modifiers (acetonitrile, methanol, and tetrahydrofuran), buffered aqueous solutions at pH 2-8, ion-pair reagents [octane sulfonic acid sodium salt, sodium dodecyl sulphate, and bis-(2-ethylhexyl)phosphoric acid], or silanol blockers (ammonia, tetrabutyl ammonium chloride, and diethyl amine) are investigated. The separation selectivity as well as spot symmetry and efficiency system in the applied eluent systems are analyzed. The most selective and efficient systems are used in two-dimensional separations of isoquinoline alkaloids' mixture and the plant extracts Chelidonium majus, Fumaria officinalis, and Glaucium flavum. Two-dimensional thin-layer chromatography on cyanopropyl layer with diode array detection densitometry enables the separation and identification of some alkaloids in plant extracts. 相似文献
5.
CM Silva MF Duarte ML Mira MH Florêncio K Versluis AJ Heck 《Rapid communications in mass spectrometry : RCM》1999,13(12):1098-1103
Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
6.
Catarina IV Ramos Flávio Figueira Marcelo D Polêto Francisco ML Amado Hugo Verli João PC Tomé M Graça PMS Neves 《Journal of mass spectrometry : JMS》2016,51(5):342-349
Electrospray mass spectrometry/mass spectrometry was used to investigate the gas‐phase properties of protonated expanded porphyrins, in order to correlate those with their structure and conformation. We have selected five expanded meso‐pentafluorophenyl porphyrins, respectively, a pair of oxidized/reduced fused pentaphyrins (22 and 24 π electrons), a pair of oxidized/reduced regular hexaphyrins (26 and 28 π electrons) and a regular doubly N‐fused hexaphyrin (28 π electrons). The gas‐phase behavior of the protonated species of oxidized and reduced expanded porphyrins is different. The oxidized species (aromatic Hückel systems) fragment more extensively, mainly by the loss of two HF molecules. The reduced species (Möbius aromatic or Möbius‐like aromatic systems) fragment less than their oxidized counterparts because of their increased flexibility. The protonated regular doubly fused hexaphyrin (non‐aromatic Hückel system) shows the least fragmentation even at higher collision energies. In general, cyclization through losses of HF molecules decreases from the aromatic Hückel systems to Möbius aromatic or Möbius‐like aromatic systems to non‐aromatic Hückel systems and is related to an increase in conformational distortion. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Selected alkaloid standards were chromatographed on C18 W layers using various aqueous eluents containing an organic modifier and pH 3 buffer to suppress silanol ionization or an organic modifier and pH 8 buffer to suppress alkaloid ionization. Anionic ion pairs such as sodium dodecyl sulfate, octane-1-sulfonic acid sodium salt, pentane-1-sulfonic acid sodium salt, and bis(2-ethylhexyl)ortho-phosphoric acid are used to improve peak shape, efficiency, and selectivity. Amines (e.g., diethylamine, triethylamine, and tetrabutylamonium chloride) are incorporated into mobile phases to block surface silanols. The effect of chromatographic conditions on the separation of the investigated alkaloids is analyzed by the comparison of particular densitograms, asymmetry factor, or theoretical plate number. The best efficiency, peak symmetry, and separation selectivity of the investigated compounds is obtained through the addition of amine (especially diethylamine) to the mobile phases. 相似文献
9.
JPC – Journal of Planar Chromatography – Modern TLC - Alkaloid standards have been chromatographed on silica layers with a variety of aqueous and nonaqueous mobile phases. The effect on... 相似文献
10.
A Soibel SS Banerjee Y Myasoedov ML Rapparort E Zeldov S Ooi T Tamegai 《Pramana》2002,58(5-6):893-898
Using a novel differential magneto-optical imaging technique we investigate the phenomenon of vortex lattice melting in crystals
of Bi2Sr2CaCu2O8 (BSCCO). The images of melting reveal complex patterns in the formation and evolution of the vortex solid-liquid interface
with varying field (H)/temperature (T). We believe that the complex melting patterns are due to a random distribution of material disorder/inhomogeneities across
the sample, which create fluctuations in the local melting temperature or field value. To study the fluctuations in the local
melting temperature/field, we have constructed maps of the melting landscape T
m(H, r), viz., the melting temperature (T
m) at a given location (r) in the sample at a given field (H). A study of these melting landscapes reveals an unexpected feature: the melting landscape is not fixed, but changes rather
dramatically with varying field and temperature along the melting line. It is concluded that the changes in both the scale
and shape of the landscape result from the competing contributions of different types of quenched disorder which have opposite
effects on the local melting transition. 相似文献