Thin-layer chromatography

About: Thin-layer chromatography is a research topic. Over the lifetime, 7494 publications have been published within this topic receiving 124179 citations. The topic is also known as: TLC.

Bioassay-guided isolation of antioxidants from Astragalus altaicus by combination of chromatographic techniques.

Abstract: An efficient method for bioassay-guided preparative isolation of antioxidants from the n-butanol extract of Astragalus altaicus Bunge was ingeniously developed by combination of silica gel column chromatography and high-speed counter-current chromatography. Under the bioassay-guidance of antioxidant activities, the antioxidants were gradually separated from the crude sample of Astragalus altaicus Bunge by silica gel column chromatography and high-speed counter-current chromatography. Silica gel column chromatography separation was performed with chloroform, chloroform-methanol (100:1∼5:1, v/v) and chloroform-methanol-water (5:1:0.1∼2:1:0.1, v/v/v). High-speed counter-current chromatography separation was performed with a two-phase solvent system composed of ethyl acetate-n-butanol-water (2:1:6, v/v/v), which was successfully selected by thin layer chromatography analysis, at a flow rate of 1.5 mL/min. As a result, isorhamnetin-3-gentiobioside (20.8 mg), rutin (82.0 mg), and narcissin (12.8 mg) were obtained for the first time from 200 mg of the crude sample, ABS-5 of Astragalus altaicus Bunge. The purities were all at over 95% by high-performance liquid chromatography analysis, and their structures were unambiguously identified by mass spectroscopy, 1H, and 13C nuclear magnetic resonance spectroscopy. Antioxidant activities of the three compounds were also assayed by in vitro ABTS [2,2'-azino-bis-(3- ethylbenzothiazoline-6-sulphonic acid) diamonium salt] radical cation scavenging activity. Among them, rutin possessed the highest antioxidant capacity with SC50 value of 22.15 μg/mL. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determination of sulfur compounds in high-boiling petroleum distillates by ligand-exchange thin-layer chromatography

Abstract: Determination of sulfur compounds in high-boiling petroleum distillates was carried out by ligand-exchange thin-layer chromatography (LETLC). Mercaptans, sulfides, and disulfides were separated from aromatic hydrocarbons by LETLC on a mercury-loaded silica gel. It was, however, difficult to separate dibenzothlophene from aromatic hydrocarbons. Alkyl mercaptan formed a strong complex with mercury and was not developed at all, even with polar solvent. Sulfur compounds were isolated by this procedure from petroleum aromatic concentrate and were identified by GLC/MS.

Multimodal thin layer chromatographic separation of taxol and related compounds from Taxus brevifolia

Abstract: Two multimodal two dimensional TLC procedures are described for the separation of taxol and cephalomannine from other natural products found in the bark of Taxus brevifolia. For the first procedure, a cyano modified silica gel plate was developed in the first dimension in methylene chloride: hexane acetic acid (9:10:1) and in the second dimension in water: acetonitrile: methanol: tetrahydrofuran (8:5:7:0.1). For the second procedure, a diphenyl modified silica gel plate was developed in the first dimension in hexane: isopropanol: acetone (15:2:3) and in the second dimension in methanol: water (7:3). In both procedures, taxol was resolved from cephalomannine and at least another twenty compounds

Characterization of Triacylglycerol Composition of Fish Oils by Using Chromatographic Techniques

Abstract: Triacylglycerols (TAG) of two different refined fish oils from sardine and a mixture of tuna and sardine oil were separated by reverse phase high performance liquid chromatography (RP-HPLC) with a binary solvent gradient of acetone/acetonitrile. Different fractions were observed in the chromatogram and TAG species were tentatively identified by subsequent analysis of the fatty acid (FA) profile in each fraction by capillary Gas Chromatography (GC). Peak identities were assigned on the basis of a multiple linear regression analysis by using factors such as carbon number, number of double bonds, number of monounsaturated fatty acids (MUFA) and number of polyunsaturated fatty acids (PUFA) in the molecule as predictors for TAG retention time. A successful correlation was obtained between retention times and the equivalent carbon number (ECN) of triacylglycerols. Regiospecific analysis of fatty acids in the TAG has been conducted by ethanolysis of the fish oil by using an immobilized lipase. The subsequent separation of 2-monoacylglycerol (2-MAG) by TLC (thin layer chromatography) analysis showed that ethanolysis system is effective for analysis of FA composition at the 2-position in oils containing PUFA. Principal components analysis (PCA) has been also applied to establish correlations between the different fatty acids in the TAG.

Liquid chromatography on carbosilochrom and carbosilica gel-silica adsorbents with a modified carbon surface

Abstract: The silica adsorbent Silochrom C-120 which is homogeneous, macroporous and thermally stable, and Spherisorb S20W which is a wide-pore silica gel have been modified by the deposition on them of carbon formed by the pyrolysis of benzene. The adsorbent structures before and after modification have been studied. Columns packed with the Carbosilochrom and Carbosilica gel so obtained were used for studies of their selectivity in the liquid chromatography of an homologous series of polymethyl-and monoalkylsubstituted benzenes, alkylnaphthalenes, methylphenols and benzoic esters on elution with solutions of methanol + water of different concentrations. An increase in the amount of carbon deposited on the adsorbent and an increase in solvent polarity results in an increase in adsorbent selectivity. In the case of polymethylsubstituted benzenes this increase is greater than in the case of isomeric monoalkylsubstituted benzenes. For phenols this increase is less than that for the corresponding hydrocarbons. The separating power of the column can be controlled by changing the degree of specificity of the carbosilica and the polarity of the eluent.