Application of TLC and OPLC in the Determination of Pigments from Natural Products

JPC – Journal of Planar Chromatography – Modern TLC - Planar chromatographic methods thin-layer chromatography (TLC) and over-pressure thin-layer chromatography (OPLC) have been...     

Modification of an Office Scanner for the Determination of Aflatoxins after TLC Separation

JPC – Journal of Planar Chromatography – Modern TLC - A computer-driven office scanner has been modified to enable measurement of the fluorescence of aflatoxins on thin-layer...     

Use of Micelles in the TLC Separation of Polynuclear Aromatic Compounds and Amino Acids

Abstract

The polynuclear aromatic compounds (PNA): anthracene, napthalene, phenanthrene, pyrene, pyrenecarboxaldehyde, benzo (a) pyrene, benzo (e) pyrene, perylene and fluorene can be chromatographed on polyamide TLC sheets using an aqueous micellar solution cf sodium dodecylsulfate (SDS) as the mobile phase. Reversed micellar solutions (of sodium dioctylsulfosuccinate) were used in a reverse phase chromatographic separation of amino acids. Some amino acids tended to streak slightly rather than move as discrete spots. Conditions could be adjusted, however, so that most of the amino acids and all PNA's would move as spots.     

Investigation of Thyme (Thymus vulgaris L.) Essential Oil by Use of the BioArena System

JPC – Journal of Planar Chromatography – Modern TLC - The composition of the essential oil of Thymus vulgaris L. has been determined by GC-FID and GC-MS. Because separation of thymol,...     

Fully On-Line Hyphenation of an Experimental OPLC Separation Unit with Diode-Array Detection and Mass-Spectrometry (OPLC-DAD-MS) for Analysis of Xanthine Compounds

JPC – Journal of Planar Chromatography – Modern TLC - The newly developed experimental OPLC separation unit 100 (OSU 100) has been used for fully on-line multiple hyphenation using the...     

Effect of trans-Resveratrol and Ascorbigens on the Fire Blight Pathogen Erwinia amylovora in the BioArena System

JPC – Journal of Planar Chromatography – Modern TLC - On the basis of our earlier observations, preliminary experiments were conducted with the fire blight pathogen Erwinia amylovora...     

A new method for the quantitative continuous elution and collection of TLC Spots without damaging the layer

Summary A method is described which combines the attractive properties of ascending TLC with the advantage of a continuous removal and collection of the products successively reaching the top. This is achieved by using as support for the thin layer a glass capillary which continuously removes the solvent reaching the top by means of pressure applied from outside, without damaging the layer. The fractions thus obtained are led either directly to some detecting device or to a microfraction collector in order to be analyzed later on. An auxiliary device has been constructed which allows the application of the component mixture at the bottom of the layer without touching the layer. The same layer can now be used repeatedly; its performance does not decrease after at least ten runs. Micro-weighing is used as detection method.

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Zusammenfassung Es wird ein Verfahren beschrieben, das die vorteilhaften Eigenschaften der aufsteigenden Dünnschicht-Chromatographie mit der kontinuierlichen Abnahme und Sammlung des Eluates verbindet. Dies wird dadurch erreicht, daß die Dünnschicht auf einer Capillare aufgetragen ist, die die am oberen Rand ankommende Flüssigkeit unter Einwirkung eines äußeren Drucks laufend ableitet, ohne daß die Schicht geschädigt wird. Die einzelnen Fraktionen werden in einem Kollektor gesammelt oder unmittelbar einem geeigneten Detektor zugeleitet. Hier wird die Mikrowägung zu diesem Zweck benutzt. Zum Auftragen der Probelösung wurde eine Hilfsvorrichtung entwickelt, durch die es ermöglicht wird, die Schicht nicht zu berühren und mehrfach zu benutzen.

     

Separation of Sulfur Species in Water by Co-Electroosmotic Capillary Electrophoresis with Direct and Indirect UV Detection

Co-electroosmotic capillary electrophoresis (co-CZE) with both direct and indirect UV detection was investigated for the separation of sulfur species. With direct UV detection, the separation of S₂O^2? ₃, S₂O^2? ₄ was possible using 20 mM phosphate electrolyte containing 0.75 mM tetradecyltrimethylammonium bromide (TTAB) and 15% acetonitrile. To obtain optimal peak shape and sensitivity using indirect UV detection, a range of background electrolytes (BGEs), including benzoate, phthalate, 2,6-pyridinedicarboxylate (2,6-PDCA) and trimellitate, were examined as the BGEs. Of all the BGEs, 2,6-PDCA gave high selectivity and indirect UV response due to its mobility matching to that of sulfur species and its high absorptivity. Detection limits in range of 3-6 μM were obtained using either direct UV or indirect UV detection. The proposed CZE methods were used for the determination of sulfur species in water samples, and provided fast separation of sulfur species in less than 5 min.     

Electron Donor-Acceptor Complexing Reagents for the Detection of Pesticides on TLC

The formation of π-complexes to detect and identify a representative group of carbamate, anilide and urea pesticides was investigated. Results obtained with several electron-acceptor reagents used by previous workers are compared with those obtained with a group of nitro-substituted fluorene derivatives. The pesticides studied were chosen for their potential ability to act as electron donors. Detection limits after thin-layer chromatography ranged from 0.5 to 5.0 micrograms, depending upon the strength of the complex formed. Various chromatographic systems were studied and applications of in situ reflectance spectroscopy and mass spectrometry were investigated. The method combines a reasonable sensitivity with good selectivity and the pesticide may be recovered from the complex for further study. This non-destructive method of analysis should be of particular use in the separation and identification of these pesticides and their metabolites.     

Ruthenium (II) 1,10-Phenanthroline Salts as Mobile Phase Additives for the Separation and Indirect Detection of Free Amino Acids

Abstract

Ruthenium (II) 1,10-phenanthroline, Ru(phen)²⁺ ₃, salts are used as ion interaction reagents in a basic mobile phase for the retention, resolution, and indirect photometric detection (IPD) of free amino acids on a polystyrene divinylbenzene (Hamilton PRP-1) column. Mobile phase Ru(phen)²⁺ ₃ concentration and pH and type and concentration of organic modifier and counteranion affect retention and IPD. Underivatized amino acid elution order is influenced by side chain structure typical of ion exchange processes. Detection limits for the separation and detection of free amino acids using an isocratic elution condition are about 0.1 nmole for lower retained amino acids and 0.25 nmole for higher retained amino acids for a 3:1 signal:noise ratio. Gradient elution is possible but at higher detection limits.     

Potential of the Flowing Eluent Wall and Aliquot On-Line Detection in the OPLC 50 and 100 Systems

JPC – Journal of Planar Chromatography – Modern TLC - The flowing-eluent-wall (FEW) procedure is suitable for single and multi-channel on-line overpressured-layer chromatographic (OPLC)...     

A New Indirect Electrochemical Method for Determination of Ozone in Water Using Multiwalled Carbon Nanotubes

A new electrochemical methodology has been developed for the detection of ozone using multiwalled carbon nanotubes (MWCNT). The method presented here is based on the reaction of ozone with indigo blue dye producing anthranilic acid (ATN). The electrochemical profile of ATN on an electrode of glassy carbon (GC) modified with MWCNT showed an oxidation peak potential at 750 mV vs. Ag/AgCl. An analytical method was developed using differential pulse voltammetry (DPV) to determine ATN in a range of 50–400 nmol L^?1, with a detection limit of 9.7 nmol L^?1. Ozonated water samples were successfully analyzed by GC/MWCNT electrode and the recovery procedure yielded values between of 96.5 and 102.3 %.     

Electrochemiluminescence Detection of Clarithromycin in Biological Fluids after Capillary Electrophoresis Separation

Abstract

A sensitive analytical method for the determination of clarithromycin in biological fluids with electrochemiluminescence detection after capillary electrophoresis separation was proposed in this paper, based on the enhancing effect of clarithromycin on electrochemiluminescence of tris(2,2-bipyridyl) ruthenium(II) (Ru(bpy)₃ ²⁺). Various factors influencing the separation and detection of clarithromycin were examined to establish the detection system. Under the optimized conditions, the electrochemiluminescence intensity is proportional with the concentration of the analyte over the range of 0.1–10 µM with a detection limit of 30 nM (S/N = 3). The proposed method has been successfully applied for clarithromycin content determination in spiked human plasma and urine samples.     

新型毛细管电泳化学发光系统应用于氨基酸分离测定

本研究建立一种以过氧草酸酯为化学发光体系的新型毛细管电泳化学发光系统,并将该系统应用于氨基酸的分离测定.该系统设计了新型的电极模式与反应混和模式以获得高的信号稳定性与检测灵敏度.以一端与高压电源负极相连的铂丝连接到不锈钢注射针头为接地电极,电泳毛细管穿过注射针头,且其末端到达注射针头的出口,电泳毛细宇航局末端与化学发光试剂在反应池中以相对的方向靠近.实验结果表明,该系统稳定性好、分离效率高、灵敏度高、精密度好,对天冬氨酸与亮氨酸的检出限分别为2.0和 1.1 nmol/L.峰高及迁移时间的相对标准偏差分别为2.3%～3.8%和1.2%～1.5%.     

Use of an Infrared Laser in a Detection System for Liquid Chromatography

Abstract

A liquid chromatography detection system based on an infrared laser has been constructed and some tentative evaluations of its performance have been made. Although restricted to use with a very few solvents (mainly halocarbons), this system should be applicable whenever chloroform or a halocarbon solvent of lower strength (polarity) can be used. Injected sample quantities as small as one microgram have been detected on elution.     

Detection and Inhibition of an Organic Interference in the Indigo Method for Ozone

Abstract

Aqueous samples of organic solutes often exhibit a delayed reaction in the indigo test for dissolved ozone which is similar to the reaction of ozone itself. This phenomenon has made timing critical in aqueous ozone measurements and has been observed in both laboratory situations with high organic carbon:ozone ratios and in a potable water treatment plant with low organic carbon:ozone ratios. Organic hydroperoxides, singlet oxygen, and Fenton's reagent but not triplet oxygen, hydrogen peroxide, nor p-benzoquinone were found to interfere. Addition of phenolic antioxidants was found to inhibit the interference. These results extend the utility of the indigo method to solutions of high organic carbon concentration.     

Cation Exchange Liquid Chromatography with Amperometric Detection as a Method for the Analysis of Endogenous Catecholamine Concentrations in Plasma or Serum

Abstract

A chromatographic system which permits determination of catecholamines, isolated from a few ml of plasma or serum, is described in detail. Some factors of importance for the improvement of the signal-to-noise ratio at subpicomole detection levels have been carefully investigated.     

Reagents for Detection of Carboxylate Anion Ligands after Chromatographic Separation of Zinc Carboxylato Complexes

JPC – Journal of Planar Chromatography – Modern TLC - Reagents for detection of carboxylate anions as components of zinc carboxylato mixed-ligand complexes, after chromatographic...     

Exploiting Sulphide Generation and Gas Diffusion Separation in a Flow System for Indirect Sulphite Determination in Wines and Fruit Juices

A flow system for sulphite determination in wines and fruit juice samples has been developed exploiting H₂S generation and gas diffusion separation. The composed sandwich gas diffusion cell was coupled in the flow manifold to permit sulphite reduction to H₂S and H₂S diffusion through a microporous PTFE membrane to produce methylene blue resulting from the reaction with N,N-dimethylphenylene diamine (DMPD) and Fe³⁺. The flow parameters were optimized, and the best results were obtained by using NaOH solution for H₂S collection. Interferences of H₂S, CO₂ and ascorbic acid were evaluated. Limits of detection (3σ) for the free and total sulfite were calculated at 0.12 and 0.25 mg L⁻¹, respectively. The results obtained by the proposed process were in agreement with the reference methods for a 95% confidence level.     

Use of Computer-Assisted Color Treatment of Chromatograms in the TLC Determination of Tartrazine

A procedure was developed for the treatment of thin-layer chromatograms in the analysis of the Tartrazine E102 synthetic food dye. The procedure includes the conversion of a TLC plate into the Windows 95/98 bit-mapped graphics format using scanning on a flatbed scanner followed by the processing of the image obtained with the Adobe Photoshop 5.0 program package in the RGB color mode (red, green, and blue color channels).