Showing papers on "Thin-layer chromatography published in 2000"
TL;DR: The all-liquid chromatographic technique of high-speed countercurrent chromatography (HSCCC) has been applied for separations of anthocyanin mixtures and antioxidant activity of the purified pigments was determined using the Trolox equivalent antioxidant capacity test.
Abstract: The all-liquid chromatographic technique of high-speed countercurrent chromatography (HSCCC) has been applied for separations of anthocyanins. The biphasic mixture of tert-butyl methyl ether/n-butanol/acetonitrile/water (2:2:1:5) acidified with trifluoroacetic acid was found to be a suitable solvent system for anthocyanin separation. In some cases, enrichment of the pigments on Amberlite XAD-7 resin prior to HSCCC has been carried out. The anthocyanin mixtures from red cabbage, black currant, black chokeberry, and roselle were successfully fractionated using HSCCC. Peak purity control was done by nuclear magnetic resonance spectroscopy as well as electrospray ionization ion trap multiple mass spectrometry. Finally, antioxidant activity of the purified pigments was determined using the Trolox equivalent antioxidant capacity test.
175 citations
TL;DR: An overview of analytical methods for the measurement of biologically important tea catechins is presented; liquid chromatography and capillary electrophoresis are the most cited techniques for catechin separation, identification and quantitation.
172 citations
TL;DR: Several Aspergillus species were examined for their ability to degrade ochratoxin A and A. niger CBS 120 was found to effectively eliminate ochRatoxin A from both liquid and solid media, and the degradation product, och ratoxin alpha, was also decomposed.
172 citations
TL;DR: ERU is an extremely reactive ketose, which rapidly glycates and crosslinks proteins, and therefore may mediate the AsA-dependent modification of protein (ascorbylation) seen in vitro, and also proposed to occur in vivo in human lens during diabetic and age-onset cataract formation.
151 citations
107 citations
TL;DR: Folic acid and 6-formylpterin solutions of pH in the range 4.5–6.0 were photolysed at 350 nm at room temperature and a ‘red intermediate’ is observed, which is thermally oxidised producing 6-carboxypterin on admission of oxygen.
Abstract: Folic acid and 6-formylpterin solutions of pH in the range 4.5–6.0 were photolysed at 350 nm at room temperature. The photochemical reactions were followed by UV–VIS spectrophotometry, thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). In the presence of oxygen, folic acid is photochemically cleavaged yielding 6-formylpterin and p-aminobenzoylglutamic acid. As the photolysis proceeds, 6-carboxypterin arises from 6-formylpterin, as observed when solutions only containing the latter compound are irradiated in the presence of oxygen. In the absence of oxygen, folic acid is not light-sensitive. However, when oxygen free solutions of 6-formylpterin are irradiated, a ‘red intermediate’ is observed, which is thermally oxidised producing 6-carboxypterin on admission of oxygen. The quantum yields of substrates disappearance and of photoproducts formation are reported.
92 citations
87 citations
TL;DR: This is the first report clearly indicating the involvement of a microorganism in the chemotaxis and biodegradation of methyl-4-nitrophenol and formation of catechol as an intermediate in the degradative pathway.
77 citations
TL;DR: In this article, cyclohexyl carbamates of cellulose and amylose were prepared and their resolving abilities for enantiomers were evaluated as chiral stationary phases (CSPs) for high-performance liquid chromatography.
Abstract: Cyclohexylcarbamates of cellulose and amylose were prepared and their resolving abilities for enantiomers were evaluated as chiral stationary phases (CSPs) for high-performance liquid chromatography. The CSPs showed high resolving abilities, which are comparable to those of popular CSPs, tris(3,5-dimethylphenylcarbamate)s of cellulose and amylose. The cycloalkylcarbamates could also be used as CSPs for thin-layer chromatography because of the absence of a phenyl group, which causes the difficulty of detection by UV radiation. In addition, these two derivatives were soluble in chloroform and exhibited chiral discrimination to some chiral compounds in 1H NMR spectroscopy as well as in HPLC.
60 citations
TL;DR: This unit describes methods for spotting test compounds onto a TLC plate, developing the plate in a suitable solvent system, visualizing the results, and calculating the retention factor (Rf).
Abstract: TLC is used extensively in nucleic acid chemistry to monitor the progress of chemical reactions, to assay fractions collected from a larger chromatographic separation (e.g., column chromatography), and to determine optimal conditions prior to column chromatography. This unit describes methods for spotting test compounds onto a TLC plate, developing the plate in a suitable solvent system, visualizing the results, and calculating the retention factor (R(f)). Candidate compounds can be co-spotted for identification without relying on R(f) values.
49 citations
TL;DR: In this article, a combination of high-performance thin-layer chromatography (HPTLC) using automated multiple development was modified for semi-preparative purposes, with subsequent liquid chromatography-electrospray mass spectrometry for the profiling of ceramides.
TL;DR: A high-performance thin-layer chromatographic (HPTLC) method for the determination of the two main potato glycoalkaloids, alpha-chaconine and alpha-solanine, in different parts of the potato plant, is described.
TL;DR: In this paper, a thin-layer chromatography and flame-ionization detection (TLC/FID) system was designed to investigate the changes in free fatty acid (FFA) of rice during storage using a thin layer chromatography.
Abstract: A convenient method which possessed simplicity and high sensitivity was designed to investigate the changes in free fatty acid (FFA) of rice during storage using a thin-layer chromatography and flame-ionization detection (TLC/FID) system. In this method, two different solvent systems for TLC were used according to the purpose of experiments. Solvent system A (hexane and diethyl ether and acetic acid 80:20:1) was suitable to obtain a chromatogram showing the overall state of rice lipid degradation. Using solvent system A, the degradation of triglyceride or the increase in FFA during storage was clearly visualized as changes in the chromatogram. Solvent system B (hexane and acetic acid 100:1) was used to improve the low reproducibility of the TLC/FID method. When methyl stearate was used as an internal standard with solvent system B, high reproducibility of the FFA value was obtained, and very small changes were detectable in stored white milled rice. This method has small sample size and simple op...
TL;DR: In this article, a review describes analytical methods developed for the separation, identification and quantification of trans-isomers of unsaturated fatty acids in milk fat, such as infrared spectroscopy, direct gas chromatography, and liquid chromatography coupled with mass spectrometry.
Abstract: This review describes analytical methods developed for the separation, identification and quantitation of trans-isomers of unsaturated fatty acids. Although these methods are applicable to a wide variety of food matrices, we have particularly emph a- sised the analysis of trans unsaturated fatty acids in milk fat. Various methods are described such as infrared spectroscopy, direct gas chromatography, gas chromatography in combination with either thin-layer chromatography or liquid chromatography both impregnated with silver nitrate and gas chromatography coupled with mass spectrometry. The field of application, the advantages and the drawbacks of each method are evaluated and discussed.
TL;DR: A simple and reproducible high-performance thin-layer chromatographic method was developed and can be used for the detection, monitoring, and simultaneous quantification of bergenin and gallic acid in B. ligulata.
Abstract: A simple and reproducible high-performance thin-layer chromatographic method was developed for the simultaneous determination of bergenin and gallic acid in Bergenia ligulata. Water and methanol were used as the extracting solvents. The concentrations of bergenin and gallic acid in both of these solvents were found to be almost the same. The method involves separation of the components by thin-layer chromatography on a precoated Silica Gel 60 F254 plate with a solvent system of ethyl acetate-formic acid-acetic acid-water (100 + 11 + 11 + 27). The sensitivity of the method for bergenin was 0.30 microg, whereas for gallic acid it was 0.25 microg. The proposed method is precise and sensitive and can be used for the detection, monitoring, and simultaneous quantification of bergenin and gallic acid in B. ligulata.
TL;DR: Different combinations of acetonitrile-methanol-water were found to be successful in resolving the DL-amino acids and the spots were detected by ninhydrin and the detection limit was 0.66 microg.
Book•
06 Dec 2000
TL;DR: This chapter discusses the critical factors that govern a successful quantitative chromatographic analysis sample collection, transport and storage sample preparation the chromatography detector processingchromatographic data.
Abstract: Introduction to quantitative chromatographic analysis: the critical factors that govern a successful quantitative chromatographic analysis sample collection, transport and storage sample preparation the chromatography detector processingchromatographic data. Quantitative gas chromatographic analysis: gas chromatographic apparatus for quantitative analysis gas chromatography applications. Quantitative liquid chromatography analysis: liquid chromatographic apparatus for quantitativeanalysis liquid chromatography applications. Thin layer chromatography: thin layer chromatography apparatus thin layer chromatography applications.
TL;DR: Procedures for the separation of Galfbeta1-->XGlcNAc and Galpbeta1 -->4(Galp beta1-->6)Glc NAcol as the corresponding alditols by high-pH anion-exchange chromatography with pulse amperometric detection are presented.
TL;DR: A two-dimensional thin-layer chromatographic method was developed for the qualitative determination of the cardiotoxins oleandrin, gitoxin, digitoxin, gitoxigenin, and grayanotoxins I, II, and III in gastrointestinal contents, feces, and plant material.
Abstract: A two-dimensional thin-layer chromatographic method was developed for the qualitative determination of the cardiotoxins oleandrin, gitoxin, digitoxin, gitoxigenin, and grayanotoxins I, II, and III in gastrointestinal contents (stomach, rumen, colon, and cecum contents), feces, and plant material. The cardiotoxins were extracted with dichloromethane. The extract was cleaned up by charcoal and reverse phase solid-phase extraction columns. Analysis was performed by two-dimensional thin-layer chromatography on silica gel plates and visualized by aluminum chloride followed by chloramine T spray. The method detection limits were 0.05 μg/g for oleandrin, 0.1 μg/g for gitoxin, and 0.2 μg/g for the other toxicants in gastrointestinal contents and feces and were 5 times higher in plant material. Four replicate fortifications of bovine rumen contents, bovine feces, and alfalfa at these levels were all well recovered. The diagnostic utility of the method was tested by analyzing samples submitted to the veterinary tox...
TL;DR: A high-performance thin-layer chromatographic method was used to determine the glycoalkaloids alpha-solanine and alpha-chaconine in potatoes and good results with respect to linearity, accuracy, and precision were obtained in the concentration range studied.
Abstract: A high-performance thin-layer chromatographic (HPTLC) method was used to determine the glycoalkaloids alpha-solanine and alpha-chaconine in potatoes. Alpha-solanine and alpha-chaconine are extracted from dehydrated potatoes with boiling methanol-acetic acid (95 + 5, v/v). The analytes are separated on a Silica Gel 60 F254 HPTLC plate by a saturated mixture of dichloromethane-methanol-water-concentrated ammonium hydroxide (70 + 30 + 4 + 0.4, v/v), which is used for vertical development of the plate up to a distance of 85 mm. For visualization, the plate is dipped 3 times into a modified Carr-Price reagent, 20% (w/v) antimony(III) chloride in acetic acid-dichloromethane (1 + 3, v/v), and subsequently heated on a hot plate at 105 degrees C for 5 min. The glycoalkaloids all appear as red chromatographic zones on a colorless background. Densitometric quantification is performed at 507 nm by reflectance scanning. After determination of the appropriate response function, the proposed method was validated. Good results with respect to linearity, accuracy, and precision were obtained in the concentration range studied.
TL;DR: In this paper, the reaction parameters for microwave assisted synthesis of arylpiperazines were optimized via their rapid synthesis on thin layer chromatography (TLC) plates, where reaction parameters were optimized using microwave assisted reaction parameters.
TL;DR: The dansyl ester of anandamide was prepared and showed intense fluorescence on silica gel thin-layer chromatography when viewed under long-wavelength ultraviolet light (detection limit, 15 fmol) and a high-performance liquid chromatography method for the quantitation of an andamide was developed.
TL;DR: Thin layer chromatography (TLC) analysis revealed that destructive distillation of Juniperus procera tree gave ten major components, whereas Croton megalocarpus tree yielded five components.
TL;DR: In this article, two-dimesional thin-layer chromatography has been used to screen plant samples for ecdysteroids, and satisfying separations were obtained even in the presence of substantial impurities and for mixtures containing many ecdystersoids.
Abstract: Two-dimesional thin-layer chromatography has been used to screen plant samples for ecdysteroids. Satisfactory separations were obtained even in the presence of substantial impurities and for mixtures containing many ecdysteroids. Normal-phase silica and octadecyl silica plates were used to differntiate apolar and polar ecdysteroids, respectively. The major advantages of thin-layer chromatography are multiple detection, which enables specific detection of the ecdysteroids. Use of a small amount of water in the mobile phase in the fist dimension, the a water-free mobile phase in the second dimension, can afford favorable separations.
TL;DR: In this paper, 20-hydroxy-arachidonic acid (20-HETE) was determined in urine by an isotope dilution assay using gas chromatography/mass spectrometry (GC/MS).
Abstract: 20-Hydroxy-arachidonic acid (20-HETE) was determined in urine by an isotope dilution assay using gas chromatography/mass spectrometry (GC/MS). After addition of 18O2-internal standard, 20-HETE was extracted from urine with hexane either directly or after treatment with glucuronidase. 20-HETE was derivatized to the pentafluorobenzylester and the sample was applied to thin layer chromatography with iso-octane/iso-propanol 9:1 (v/v) as the developing solvent. The corresponding zone was extracted and 20-HETE was hydrogenated. After derivatization to the trimethylsilylether, 20-HETE was determined by GC/MS using the [M-pentafluorobenzyl]- -ion in the negative ion chemical ionization mode. Excretion rates of free and glucuronide conjugated 20-HETE was determined in healthy children and in children with hyperprostaglandin-E-syndrome/antenatal Bartter syndrome (HPS/aBS) with or without indomethacin treatment. Compared to the controls, the HPS/aBS children showed higher excretion rates of 20-HETE, which were suppressed to normal values under indomethacin medication. Free and glucuronide conjugated 20-HETE do not correlate with PGE2 excluding any participation in HPS/aBS.
TL;DR: In this paper, a new highly selective and sensitive visual method for the determination of trace aluminium with Dihydroxyazobenzene (dhab) has been developed, which uses an octadecylsilanized (ODS) thin layer, a positively charged fluorescent 1∶1 aluminium(III) chelate is retained at a spotting position when ascending with acetone is performed.
Abstract: A new, highly selective and sensitive visual method for the
determination of trace aluminium with
o,o′-dihydroxyazobenzene (dhab) has been developed.
In this method, which uses an octadecylsilanized (ODS) silica thin layer, a
positively charged fluorescent 1∶1 aluminium(III) chelate
([Al(dhab)]+) is retained at a spotting position when ascending
development with acetone is performed. Conversely, other metal chelates and
excess reagent, which are neutral or negatively charged, are eluted close
to the solvent front. The charge difference plays an important role in the
chromatographic separation. The specific immobilization of
[Al(dhab)]+ is attributed to the electrostatic interaction
between it and the anionic charge of silanol groups on the ODS silica
plate. Insolubility of the chelate in organic solvents also contributes to
its immobilization: [Al(dhab)]+ is more hydrophilic than other
metal–dhab chelates because the chelate with the tridentate ligand
dhab2− has water molecules in its coordination sphere.
When 10 μl of ethanol–aqueous (1 + 4) sample solution containing
metal–dhab chelates is applied to the hydrophobic surface of the ODS
silica plate, the sample retains a spherical shape rather than spreading as
in conventional thin layer chromatography. The drying step results in
effective enrichment of the analyte into a fleck of 3 mm in diameter prior
to the chromatographic separation. When the resulting fleck is viewed under
ultraviolet light in the dark, the visual detection limit is 1 μg
l−1. This method has been successfully applied to the
determination of ppb levels of aluminium ion in tap water, river water and
tea samples.
TL;DR: A monospecific polyclonal anti-GalNAc-GA1 antibody, prepared in rabbit and purified by affinity chromatography, stained the neurons of cerebral cortex and cerebellum including Purkinje cells in adult rat brain, indicating that the novel GalNAc -GA1 is associated with cerebellar and other neurons in vertebrate central nervous system.
Abstract: A pair of novel neutral glycosphingolipids (Ngsls) has been identified in bovine brain. Their mobilities on thin layer chromatography were slightly different from a standard pentaglycosylceramide (nLcOse(5)Cer from bovine erythrocytes). The compounds were purified to homogeneity by column chromatography. Their fatty acid and base compositions, their monosaccharide compositions and sugar linkage positions were determined by gas-liquid chromato-graphy/mass spectrometry. Carbohydrate sequence analy-sis by(1)H NMR spectroscopy and stepwise exoglyco-sidase digestion indicated the following pentaglycosyl structure for the oligosaccharide moiety of both Ngsls: GalNAcbeta1-4Galbeta1-3GalNAcbeta1-4Galbeta1-4Gl c. The two Ngsls (abbreviated as IV(4)GalNAcGgOse(4)Cer or GalNAc-GA1), differ in their ceramide compositions, having d18:0 and d18:1 sphingosine as their long chain bases. A monospecific polyclonal anti-GalNAc-GA1 antibody, prepared in rabbit and purified by affinity chromatography, stained the neurons of cerebral cortex and cerebellum including Purkinje cells in adult rat brain, indicating that the novel GalNAc-GA1 is associated with cerebellar and other neurons in vertebrate central nervous system.
TL;DR: In this article, the retention and selectivity of separations of 23 flavonoids (aglycones and glycosides) relationships between R676 F and modifier concentration were determined for silica and diol adsorbents.
Abstract: To characterize the retention and selectivity of separations of 23 flavonoids (aglycones and glycosides) relationships betweenR
F and modifier concentration were determined for silica and diol adsorbents (with mixtures of ethyl acetate and methanol as mobile phases), for cyanopropyl silica (with mixtures of ethyl acetate and dichloromethane as mobile phases), for aminopropyl silica (with mixtures of ethyl acetate, methanol and water as mobile phases) and for octadecyl silica (with mixtures of methanol and water as mobile phases). Owing to large polarity differences between aglycones and glycosides, these groups of compounds cannot be separated other than by use of reversed-phase systems, for which the selectivity is lower. It follows from correlation plots ofR
F1 againstR
F2 that for some pairs of adsorbents (e. g. silica and diol) selectivity differences are small; for others the points in the plot are widely dispersed, indicating selectivity differences. The chemometric database obtained can be used to choose optimum chromatographic systems for the separation of given sets of flavonoids and for planning gradient elution programs for separation of flavonoid aglycones and glycosides in a single TLC experiment.