Alcohol separation by thin-layer chromatography. II

Summary Thin-layer chromatography on rice starch, maize starch, cellulose and talc makes possible the separation of the homologous series of 3,5-dinitrobenzoates of aliphatic alcohols C₁ to C₂₀. Six different solvent systems have been employed. Dependence of R _f-values on the number of C-atoms on various supports is discussed.Part I: Fresenius Z. Anal. Chem. 264, 415 (1973)     

Improved separation of amino acids by thin-layer chromatography

Summary The separation of 35 amino acids on Avicel F layers was investigated and 6 solvent systems are recommended for use either singly or in combination in 2-dimensional chromatography. The mechanisms and limitations of these methods are discussed.     

Fluorescence detection by intensity changes for high-performance thin-layer chromatography separation of lipids using automated multiple development

Changes in emission of berberine cation, induced by non-covalent interactions with lipids on silica gel plates, can be used for detecting and quantifying lipids using fluorescence scanning densitometry in HPTLC analysis. This procedure, referred to as fluorescence detection by intensity changes (FDIC) has been used here in combination with automated multiple development (HPTLC/AMD), a gradient-based separation HPTLC technique, for separating, detecting and quantifying lipids from different families. Three different HPTLC/AMD gradient schemes have been developed for separating: neutral lipid families and steryl glycosides; different sphingolipids; and sphingosine-sphinganine mixtures. Fluorescent molar responses of studied lipids, and differences in response among different lipid families have been rationalized in the light of a previously proposed model of FDIC response, which is based on ion-induced dipole interactions between the fluorophore and the analyte. Likewise, computational calculations using molecular mechanics have also been a complementary useful tool to explain high FDIC responses of cholesteryl and steryl-derivatives, and moderate responses of sphingolipids. An explanation for the high FDIC response of cholesterol, whose limit of detection (LOD) is 5 ng, has been proposed. Advantages and limitations of FDIC application have also been discussed.     

Retention and separation studies of cholesterol and bile acids using thermostated thin-layer chromatography.

The influence of temperature on retention and separation of cholesterol and bile acids, using reversed-phase thin-layer chromatography, was studied. As mobile phases methanol-water mixtures of various compositions were used. Chromatographic experiments were performed using vapor-saturated chambers at temperatures ranging from 5 to 60 degrees C. A linear relationship between R(M) values and temperature (1/T) as well as mobile phase composition was observed. The elution order of steroids under the conditions investigated was discussed. Each chromatogram was evaluated using simple optimization parameters and the best chromatographic conditions for the separation of multicomponent samples were chosen.     

A rapid separation of citrus carotenoids by thin-layer chromatography

Summary A rapid separation of citrus carotenoid pigments is achieved by successive thin-layer chromatographic separations on two different adsorbents. The first chromatography on silica gel G developed with the solvent system acetone-petroleum ether (30∶70) gives a preliminary fractionation into groups with different polarity (hydrocarbons, monols, diols and polyols). A further separation of each group into individual carotenoids is obtained by rechromatography on MgO-Kieselguhr (1∶1, w/w). The same solvent system is used, the acetone percentage being increased according to the polarity of each group (from 4% to 30%).     

Separation and micro determination of lipids by thin-layer chromatography followed by densitometry

Summary A method is presented for the rapid analysis of mixtures of lipids, particularly those from blood serum. The lipids are separated by thin-layer chromatography on silicagel, then charred with 10% aqueous sulphuric acid and the amount of carbon on the slides is measured densitometrically. 5–10 g of lipid mixture are needed for determination of the relative amounts of free sterol, sterol esters, glycerol esters, free fatty acids and total phospholipids.

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Zusammenfassung Es wird eine Methode beschrieben zur schnellen Analyse von Lipidgemischen, insbesonders von Lipiden aus Blutserum. 5–10 g eines Gemisches werden mit Hilfe der Dünnschicht-Chromatographie auf Kieselgel in Sterinester, Glycerinester, freie Steroide, unveresterte Fettsäuren und Phospholipide getrennt. Nach Verkohlung durch Erhitzen mit 10%iger Schwefelsäure werden die verschiedenen Typen densitometrisch bestimmt.

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The investigation forms part of a study on the chemical aspects of atherosclerosis, carried out under the auspices of the Netherlands Organisation of Health Research TNO.     

Determination of caprolactam by adsorptive voltammetry after separation by thin-layer chromatography

Caprolactam (2-oxohexamethyleneimine) can be determined in wastewaters and natural waters by adsorptive stripping voltammetry after separation of the product of the reaction between caprolactam and p-(N,N-dimethylamino)benzene-p′-azobenzoyl chloride. When a hanging mercury drop electrode is used with an accumulation time of 60 s in stirred solution, caprolactam can be determined from a lower limit of 0.2 μg ml^?1. With a 360-s accumulation time, linear calibration plots are obtained for 8 × 10^?10?8 × 10^?9 mol l^?1 caprolactam. The effect of interfering sample components is eliminated by the TLC separation.