Showing papers on "Thin-layer chromatography published in 1997"

Validated method for quantitation and identification of 4,4-desmethylsterols and triterpene diols in plant oils by thin-layer chromatography-high resolution gas chromatography-mass spectrometry.

Abstract: Alkaline hydrolysis was performed on a series of different vegetable oils. The unsaponifiable lipid matter was extracted with ethyl ether, and the class of 4,4-desmethylsterols (sterols) plus the triterpene diols (diols) erythrodiol, uvaol, and betulinol were isolated by thin-layer chromatography. A validated method using the acetate derivatives of sterols instead of their silyl ethers is presented. The acetate derivatives were analyzed by high resolution gas chromatography (HRGC). Retention time, precision, recovery studies, and absolute response factors were calculated for these esters, and GC/mass spectrometric structure of the assigned retention times was confirmed for the sterols and triterpene diols.

Lipase-based quantitation of triacylglycerols in cellular lipid extracts: Requirement for presence of detergent and prior separation by thin-layer chromatography

Abstract: A protocol, based on the use of Pseudomonas lipase, is presented to measure quantitatively the amount of triacylglycerols in extracts from cultured cells or tissues. Since the lipase also acts on di- and monoacylglycerols, separation of the extracts by thin-layer chromatography is recommended. In order to allow the lipase-catalyzed hydrolysis to proceed efficiently, lipid extracts or eluates from silica scraping were mixed with the detergent Thesit [dodecylpoly(ethylene glycol ether)], prior to drying. After dissolution of the dried residues in water, the amount of triacylglycerols was quantified using Pseudomonas sp. lipase, glycerol kinase, glycerol-phosphate oxidase, and peroxidase. The activity of the latter enzyme was followed either colorimetrically in the presence of 4-aminoantipyrine and 2,4,6-tribromo-3-hydroxybenzoic acid or fluorimetrically in the presence of homovanillic acid.

High performance liquid chromatographic separation of cholesterol oxidation products

Abstract: A fast, sensitive, high performance liquid chromatographic method for the simultaneous determination of cholesterol hydroperoxides and other major oxysterols, using two different detection systems (ultraviolet at 210 nm and light scattering), is here described. The hydroperoxy derivatives were obtained by cholesterol photoxidation, isolated by thin layer chromatography and joined with a standard mixture of 10 oxysterols (epoxy, hydroxy and keto derivatives). Aliquots were directly injected onto a 5-μm particle size, 25×0.46 cm i.d. Spherisorb S5 CN normal phase column, usingn-hexane/anhydrous ethanol (97:3, v/v) as mobile phase and a flow rate of 0.8 mL min−1. This method allowed, in a single isocratic analysis, the separation and quantification of the primary and secondary cholesterol oxidation products in 30 minutes. The light scattering detector was particularly useful for the determination of nonderivatized 5,6-epoxides and cholestane-3β,5α,6β-triol. The sensitivity of both detectors was very similar for most of the oxysterols, except for the 5,6-epoxides and the 7-ketocholesterol. The method suitability for the determination of cholesterol oxidation products in food matrices was successfully tested on a saponified lipid extract from egg yolk powder.

Identification of cyclopentenyl fatty acids by 1H and 13C nuclear magnetic resonance

Abstract: Gorlic, chaulmoogric and hydnocarpic fatty acids, specific to the seed oil of the genus Hydnocarpus sp. (Flacourtiaceae), are determined only with difficulty by gas chromatography. These fatty acids were isolated in their methyl ester form by a combination of different chromatographic techniques (thin-layer chromatography/Ag+ and high-pressure liquid chromatography). The proton and carbon nuclear magnetic resonance analysis of these fatty acid methyl esters showed some characteristic signals of the cyclopentenyl ring. The presence of these signals in the proton and/or carbon nuclear magnetic resonance spectrum of an oil thus will allow us to confirm the presence of these cyclopentenyl fatty acids in lipids.

Enantiomeric Separation of Aromatic Amino Alcohol Drugs By Chiral Ion-Pair Chromatography On A Silica Gel Plate

Abstract: Four chiral aromatic amino alcohol drugs were separated by TLC on a general-purpose silica gel plate with ammonium-D-10-camphorsulfonate (CSA) as chiral ion-interaction agent. The chiral aromatic amino alcohols are all of pharmacological importance as β-adrenergic blockers. The influence of eluent composition, temperature and concentration of CSA on the chiral separation is discussed. It is found that the temperature is also one of the important parameters to be varied for optimum separation in ion-pair chiral resolution. Among four drugs, three enantiomeric drugs were resolved at lower temperature (5°C). In this study, analytical reagent grade methanol and dichlormethane can be directly used as mobile phase without using molecular sieve before use.

Planar Chromatography for the Multiclass, Multiresidue Screening of Chloramphenicol, Nitrofuran, and Sulfonamide Residues in Pork and Beef

Abstract: A method is described for multiclass and multiresidue qualitative detection of chloramphenicol, nitrofuran, and sulfonamide residues in animal muscle. The drugs are extracted from 1 g tissue with 2 mL ethyl acetate and purified by silica solid-phase extraction. After elution of the cartridge, the collected solution is evaporated, and the residue is dissolved in methanol and chromatographed on a Si 60 high-performance thin-layer chromatography plate. After evaporation of solvent, nitrofurans are visualized first by their specific UV photochemical reaction with pyridine. Then chloramphenicol is reduced to its amino derivative, and this derivative and the sulfonamides are visualized by long-wave UV after reaction with fluorescamine. Chloramphenicol, nitrofurans, and sulfonamides are detected at residue level of 10, 5, and 100 μg/kg, respectively, or less in pork and beef.

A study of the cyclodextrin complexes of flavonoids by thin layer chromatography

Abstract: The complexation of various flavonoids with cyclodextrins and cyclodextrin derivatives was studied using thin layer chromatography on cellulose The results indicate that the flavonoids examined do not complex readily with α-cyclodextrin or with succinylated α-cyclodextrin However, most do complex with β-cyclodextrin, succinylated β-cyclodextrin, succinylated γ-cyclodextrin, α-cyclodextrin polymer, β-cyclodextrin polymer and γ-cyclodextrin polymer With γ-cyclodextrin elongated trails are obtained, suggesting that the kinetics are somewhat slower © 1997 John Wiley & Sons, Ltd

Compound Identification in Thin-Layer Chromatography Using Spectrometric Methods

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Separation and identification of triximenynin from Santalum spicatum R. Br.

Abstract: Seed lipids of Western Australian sandalwood (Santalum spicatum) were separated using preparative thin-layer chromatography. The oil contains about 49% oleic acid and about 40% ximenynic acid. The individual triacylglycerol bands were characterized by high-performance liquid chromatography and gas chromatography. The oil consisted of three major triglycerides: triximenynoyl-glycerol (triximenynin), an oleoyl-diximenynoyl-glycerol, and a dioleoylximenynoyl-glycerol, as demonstrated by gas chromatography with mass selective detection.

Planar chromatography for quantitative determination of ampicillin residues in milk and muscle.

Abstract: A method involving protein precipitation with trichloroacetic acid and ampicillin hydrolysis with sodium hydroxide was developed for determination of ampicillin residue in milk and muscle. The hydrolysis product reacts in an acidic medium, in the presence of mercuric chloride, to form a fluorescent compound, which is extracted from the matrix with dichloromethane and concentrated on a silica Sep-Pak cartridge in a single step. After elution of the silica cartridge and evaporation of the solvent, the residue is recovered in 100 microL ethyl acetate, and 20 microL is deposited on a chromatoplate and chromatographed with ethyl acetate. The method allows determination of ampicillin residues in milk and muscle fortified at 4 micrograms/L and 50 micrograms/kg, respectively.

Determination of cortisol in guinea pig urine by high performance thin-layer chromatography, high performance liquid chromatography, and thin-layer chromatography/radioimmunoassay

Abstract: In order to collect urinary samples from unrestrained guinea pigs, animals were kept in their familiar home cages with wood shavings for bedding. Cortisol was removed from shavings by a simple washing step, and an attempt was made to measure its concentrations by high performance thin-layer chromatography (HPTLC), high performance liquid chromatography (HPLC), or thin layer chromatography/radioimmunoassay (TLC-RIA). After intramuscular administration of 25 mg cortisol, cortisol excretion increased from about 20–30 μg/day to 400–500 μg/day (HPTLC: 531 μg/day, HPLC: 493 μg/day; TLC-RIA: 394 μg/day). Similarly, the treatment of the animals with 20 IU ACTH resulted in an augmented cortisol excretion, with mean values of 294 μg/day (HPTLC), 256 μg/day (HPLC) and 143 μg/day (TLC-RIA), respectively. The present study shows, for the first time, that cortisol excretion in unrestrained laboratory animals can be determined. Whilst the cortisol values measured by HPTLC and HPLC agree, the amounts measured by TLC-RIA were significantly lower. These differences are probably due to the presence of substances in urine or shavings which interfere with the radioimmunological determination. Hence, cortisol should be determined either by HPTLC or HPLC. Beside having a desirable specificity, these methods are more suited than TLC/RIA for steroid analysis since they confer the possibility of measuring additional steroids (e.g. precursors and/or metabolites of cortisol) in a single urine extract. This is especially the case for the HPTLC method since substances can be transformed into fluorescent derivatives.