Showing papers on "Thin-layer chromatography published in 2007"

IR-MALDI-MS Analysis of HPTLC-Separated Phospholipid Mixtures Directly from the TLC Plate

Abstract: The application of a recently developed direct coupling of high-performance thin-layer chromatography (HPTLC) and infrared matrix-assisted laser desorption/ionization orthogonal extracting time-of-flight mass spectrometry (Dreisewerd, K.; Muthing, J.; Rohlfing, A.; Meisen, I.; Vukelic, Z.; Peter-Katalinic, J.; Hillenkamp, F.; Berkenkamp, S. Anal. Chem. 2005, 77, 4098−4107) to the analysis of phospholipid mixtures is demonstrated. Mixtures of six phospholipid types were exemplarily analyzed. The sensitivity was found to be in the range between about 10 and 150 pmol of material spotted for HPTLC, depending on phospholipid acidity, Rf value, and ion polarity. The lateral resolution of the analysis is on the order of the laser focus diameter of about 220 × 300 μm2, allowing differentiation between phospholipid species of different acyl chain composition within one single HPTLC band, which were undistiguishable by a mere visual assessment. Analyte diffusion due to the addition of glycerol to the HPTLC plate wa...

An investigation of the method of determining trimethylamine in fish muscle extracts by the formation of its picrate salt—Part I

Abstract: Summary Thin layer chromatography, gas liquid chromatography and colorimetric procedures were used to identify and determine amines present in standard solutions, cod muscle extracts, and in the toluene phase of a modified TMA procedure. These tests show that the use of potassium hydroxide solution to liberate TMA from formalized trichloracetic acid extracts of fresh or frozen cod is superior to potassium carbonate solution.

Quantitative Determination of Four Water-Soluble Compounds in Herbal Drugs from Lamiaceae Using Different Chromatographic Techniques

Abstract: HPTLC-densitometric and HPLC–UV techniques were used for qualitative and quantitative determination of luteolin-7-O-glucuronide, lithospermic acid, rosmarinic acid and caffeic acid in several herbal drugs from the Lamiaceae family: Thymi herba, Serpylli herba, Majoranae herba and Menthae piperitae folium. Unmodified silica gel (HPTLC Si60) and silica gel chemically modified with aminopropyl groups (HPTLC NH2) were used during the investigation process. Among HPTLC methods the best resolution and selectivity was achieved with mobile phases: diisopropyl ether–acetone–formic acid–water (50:30:10:10, v/v/v/v) and acetone–formic acid (85:15, v/v), respectively. Plates were densitometrically evaluated. Contents of analyzed compounds in the studied aqueous extracts prepared from herbal drugs were established using both techniques. The results from the HPTLC-densitometric analysis have been compared with those from HPLC–UV on a C18 column with acetonitrile–water–formic acid as a mobile phase. The chromatographic methods were validated for linearity, LOD, LOQ, repeatability, intermediate precision and recovery. An analysis of variance showed that the HPTLC-densitometric and HPLC–UV methods are equivalent and sufficiently precise for the estimation of polyphenolic compounds mentioned above, in investigated herbal drugs. All of the suggested methods (HPTLC NH2, HPTLC Si60 and HPLC RP18) give results with good agreement.

Preparative-Scale Chromatography of Ecdysteroids of Serratula wolffii Andrae

Abstract: Numerous ecdysteroids are isolated from the herb of Serratula wolffii Andrae, a cultivated plant. The isolation procedure includes a variety of low-pressure liquid chromatography, thin-layer chromatography (TLC), gel chromatography, and high-performance liquid chromatography (HPLC) methods. The progress of separation is monitored by TLC, and the final proof of purity is carried out by HPLC. The isolation process involves the removal of proteins, flavonoids, chlorophylls, other sterines, etc. The purification also includes the separation of the target ecdysteroids from each other. Isolation of the pure compounds requires 2-8 chromatographic steps. The consecutive steps are based on the different physicochemical properties of the ecdysteroids. In some cases, a special peak-cut method employing a flush of dichloromethane into the dichloromethane-isopropanol-water mobile phase is used. This flush of dichloromethane leads to an almost perfect separation of otherwise unresolved peaks. Two ecdysteroids, 25-hydroxydacryhainansterone and 14-epi-20-hydroxyecdysone, are identified as natural products for the first time. The structure-chiroptical relationships for some ecdysteroids are also discussed.

The synthetic organic chemist's companion

Abstract: Preface. Acknowledgments. 1. Searching the Literature. 1.1. Commercial availability. 1.2. Literature preparations. 2. Reagents. 2.1. Short path distillation. 2.2. Ampules. 2.3. Reagent solutions. 2.4. Titration. 2.5. Reagent storage. 2.6. Subtle reagent variations. 2.7. Dangerous reagents. 2.8. Reagent properties. 3. Gases. 3.1. Lecture bottles. 3.2. Tanks or cylinders. 3.3. Gas safety. 4. Reactions on a Small Scale - 1-25 mmol. 4.1. Reaction flasks. 4.2. Stirring. 4.3. Glass joints. 4.4. Inert atmosphere. 4.5. Apparatus for addition. 4.6. Condensers. 4.7. Other equipment and considerations. 5. Temperature Control. 5.1. Heating. 5.2. Cooling. 6. Solvents. 6.1. Selection. 6.2. Purity. 6.3. Degassing. 6.4. Ammonia. 7. The Research Notebook. 8. Conducting the Reaction Itself. 8.1. Reagents supplied as dispersions. 8.2. Azeotropic drying. 8.3. Stoichiometry. 8.4. Syringe and inert atmosphere techniques. 8.5. General procedure for transfer of materials by syringe. 8.6. Addition. 8.7. Special techniques. 8.7.1.Water removal. 8.7.2.Reactions above atmospheric pressure. 8.7.3.Reagent gases. 8.7.4.Ultrasonication. 8.8 Quenching . 8.9. Specialized reagents. 8.9.1. Diazomethane. 8.9.2. Lithium aluminum hydride. 8.9.3.Hydrogen peroxide. 8.10. Reaction time vs. purification time. 9. Following the Reaction. 9.1. Thin layer chromatography (TLC). 9.1.1. Cutting glass TLC plates. 9.1.2. Spotting TLC plates. 9.1.3. Eluting TLC plates. 9.1.4. Visualizing TLC plates. 9.2. Gas chromatography (GC). 9.3. High pressure liquid chromatography (HPLC). 9.4. NMR spectroscopy. 10. Working Up Reactions. 10.1. Solvent extracation. 10.2. Drying organic solutions. 10.3. Specialized work-ups. 10.3.1. Reactions producing triphenylphosphine oxide. 10.3.2. Reactions involving boron compounds. 10.3.3. Reactions involving copper salts. 10.3.4. Reactions involving aluminum reagents. 10.3.5. Reactions involving tin reagents. 11. Evaporation. 12. Vacuum Systems. 12.1. Vacuum sources. 12.2. Vacuum manifolds. 12.3. Vacuum gauges. 13. Purification of Products. 13.1. Distillation. 13.2. Silica gel chromatography. 13.3. Flash column chromatography. 13.4. Gradients. 13.5. Special absorbents. 13.5.1. Triethylamine-treated silica gel. 13.5.2. Oxalic acid-coated silica gel. 13.5.3. Silver nitrate-impregnated silica gel. 13.5.4. Other sorbents. 13.6. Preparative gas chromatography. 14. Methods for Structure Elucidation. 14.1. Nuclear magnetic resonance spectroscopy. 14.2. Infrared spectroscopy (IR). 14.3. Ultravilolet spectroscopy (UV). 14.4. Combustion analysis. 14.5. Mass spectrometry. 14.6. Crystallography. 15. Cleaning Up After the Reaction. 16. Specific Examples. 16.1. The experimental. 16.2. The Org. Syn. Prep. 16.3. Comparison. 17. Strategies for Reaction Organization. Appendices. 1. NMR spectral data of common contaminants of organic reaction products. 2. Synthetic solvent selection chart. 3. Recipes for TLC stains. 4. Mixotropic series. 5. Stuck joints. 6. Acidities of organic functional groups. 7. Acidities of organic functional groups in DMSO. 8. Web resources for synthetic chemistry.

Capsaicinoid Quantitation by In Situ Densitometry of Thin Layer Chromatography Plates

Abstract: A method for measuring the content of total capsaicinoids by in situ densitometry on thin layer chromatography (TLC) plates is described This method is easy to perform, reproducible, and can detect up to 05 µg of capsaicinoids in unpurified organic extracts Identity of the compounds was assigned by comparing the chromatographic behavior of the putative capsaicinoids with that of standards Under the assayed conditions, capsaicin could not be separated from dihydrocapsaicin by TLC; however, the amounts detected in different tissues was always equal to the sum of the individual compounds, as quantified by gas chromatography, suggesting that the method is reliable

Smart thin layer chromatography plate.

Abstract: We present an innovative thin layer chromatography plate, which integrates a linear array of amorphous silicon photodiodes for real-time qualitative and quantitative chromatographic analysis.

Simultaneous estimation of pantoprazole and domperidone in pure powder and a pharmaceutical formulation by high-perfomance liquid chromatography and high-performance thin-layer chromatography methods.

Abstract: This paper describes validated high-performance liquid chromatography (HPLC) and high-performance thin-layer chromatography (HPTLC) methods for the simultaneous estimation of pantoprazole (PANT) and domperidone (DOM) in pure powder and capsule formulations. The HPLC separation was achieved on a Phenomenex C18 column (250 mm id, 4.6 mm, 5 μm) using 0.01 M, 6.5 pH ammonium acetate buffer-methanol-acetonitrile (30 + 40 + 30, v/v/v, pH 7.20) as the mobile phase at a flow rate of 1.0 mL/min at ambient temperature. The HPTLC separation was achieved on an aluminum-backed layer of silica gel 60F 254 using ethyl acetate-methanol (60 + 40, v/v) as the mobile phase. Quantification was achieved with ultraviolet (UV) detection at 287 nm over the concentration range 400-4000 and 300-3000 ng/mL with mean recovery of 99.35 ± 0.80 and 99.08 ± 0.57% for PANT and DOM, respectively (HPLC method). Quantification was achieved with UV detection at 287 nm over the concentration range 80-240 and 60-180 ng/spot with mean recovery of 98.40 ± 0.67 and 98.75 ± 0.71% for PANT and DOM, respectively (HPTLC method). These methods are simple, precise, and sensitive, and they are applicable for the simultaneous determination of PANT and DOM in pure powder and capsule formulations.

Thin-Layer Chromatography of Alkaloids on Cyanopropyl Bonded Stationary Phases. Part I

Abstract: Selected alkaloids are chromatographed on cyanopropyl-silica thin layers using various nonaqueous and aqueous eluents. Because of the strong retention of these basic compounds, nonaqueous eluents containing medium polar diluents, strongly polar modifiers, and silanol blockers (ammonia or diethylamine) are required for separation. Likewise, aqueous eluents containing modifiers (acetonitrile, methanol, and tetrahydrofuran), buffered aqueous solutions at pH 2-8, ion-pair reagents [octane sulfonic acid sodium salt, sodium dodecyl sulphate, and bis-(2-ethylhexyl)phosphoric acid], or silanol blockers (ammonia, tetrabutyl ammonium chloride, and diethyl amine) are investigated. The separation selectivity as well as spot symmetry and efficiency system in the applied eluent systems are analyzed. The most selective and efficient systems are used in two-dimensional separations of isoquinoline alkaloids' mixture and the plant extracts Chelidonium majus, Fumaria officinalis, and Glaucium flavum. Two-dimensional thin-layer chromatography on cyanopropyl layer with diode array detection densitometry enables the separation and identification of some alkaloids in plant extracts.

Fast separation and quantification of C60 and C70 fullerenes using thermostated micro thin-layer chromatography.

Abstract: Thermostated micro planar chromatography was applied for systematic separation studies of C60 and C70 fullerenes using n-alkanes as mobile phases on TLC and HPTLC plates coated with polyamide, silica gel, aluminum oxide as well as two types of octadecylsilica (C18) sorbents. Retention data were collected at constant temperature at 20 degrees C (+/-0.05 degrees C) using an unsaturated chamber mode with an eluent, such as n-pentane, n-hexane and n-heptane. The separation results under both saturated and unsaturated chamber modes for selected mobile/stationary phases were also examined, and several parameters, including separation factor (alpha) and resolution (R(S)), were compared with data obtained with high-performance liquid chromatography conditions. Interestingly, C60/C70 fullerenes separation performed on HPTLC plates with a developing distance of 45 mm was better for those observed on a 25 cm length analytical HPLC column under similar conditions to that on carbon coverage of the stationary phase, n-hexane as the mobile phase and separation temperature (R(S) = 1.84 and 1.68 for HPTLC, and HPLC, respectively). Moreover the advantage of the planar chromatographic separation of fullerenes studied is a short elution time of less than 6 min. Furthermore, the reported separation protocol shows a capability for the evaluation of fullerenes quantity in commercial samples.

Stability Indicating HPTLC and LC Determination of Dasatinib in Pharmaceutical Dosage Form

Abstract: Two sensitive and reproducible methods are described for the quantitative determination of dasatinib in the presence of its degradation products. The first method was based on high performance thin layer chromatography (HPTLC) followed by densitometric measurements of their spots at 280 nm. The separation was on HPTLC aluminium sheets of silica gel 60 F254 using toluene:chloroform (7.0:3.0, v/v). This system was found to give compact spots for dasatinib after development (R F value of 0.23 ± 0.02). The second method was based on high performance liquid chromatography (HPLC) of the drug from its degradation products on reversed phase, PerfectSil column [C18 (5 μm, 25 cm × 4.6 mm, i.d.)] at ambient temperature using mobile phase consisting of methanol:20 mM ammonium acetate with acetic acid (45:55, v/v) pH 3.0 and retention time (t R = 8.23 ± 0.02 min). Both separation methods were validated as per the ICH guidelines. No chromatographic interference from the tablet excipients was found. Dasatinib was subjected to acid–alkali hydrolysis, oxidation, dry heat, wet heat and photo-degradation. The drug was susceptible to acid–alkali hydrolysis and oxidation. The drug was found to be stable in neutral, wet heat, dry heat and photo-degradation conditions. As the proposed analytical methods could effectively separate the drug from its degradation products, they can be employed as stability indicating.

Quantitative TLC and Gas Chromatography Determination of the Lipid Composition of Raw and Microwaved Roasted Walnuts, Hazelnuts, and Almonds

Abstract: Analytical and preparative thin‐layer chromatography (TLC) on intact silica gel and silica gel layers modified with either silver nitrate (Ag‐TLC) or dimethyldichlorosilane (RP‐TLC), combined with densitometric quantification and gas chromatography (GC), have been used to elucidate the lipid classes, their fatty acid profiles, the triacylglycerol, and sterol compositions of raw and microwaved roasted walnuts, hazelnuts and almond kernels harvested in Bulgaria. The results on fatty acid and triacylglycerol compositions are in good agreement with those reported for other geographical regions. Microwave roasting on full power for 3 min produced ready‐to‐consume kernels and no changes in lipids were detected. The combination of TLC techniques used for identification and quantification of triacylglycerols gave results comparable with those obtained using reversed phase liquid chromatography‐mass spectrometry (LC‐MS).

A new procedure for separation of complex mixtures of pesticides by multidimensional planar chromatography.

Abstract: The objective of this communication is to report a new procedure for the separation of complex mixtures of pesticides by a combination of different modes of multidimensional planar chromatography. Complete separation of a mixture of pesticides was carried out by multidimensional planar chromatography on silica gel plates. The plates were videoscanned to show a real picture of the experimental results. Complete separation of all compounds was not possible by a single development on silica gel. The separation can be characterized as [PC×(nPC + PC + PC + PC)]. With the aid of this new procedure a complex mixture of fourteen compounds was separated on a 10×10 cm TLC plate.

Isolation of Three Components from Spearmint Oil: An Exercise in Column and Thin-Layer Chromatography.

Abstract: Three major components of spearmint oil, (+)-limonene, L-(−)-carvone, and (1R,2R,4R)-dihydrocarveol, are separated by silica gel column chromatography. The separation is monitored by thin-layer chromatography (TLC), with IR analysis employed to verify the identity of the separated components. Spearmint oil was chosen because it is relatively nontoxic and the separation and analysis involves colorless components. Since most organic compounds are colorless liquids, this experiment gives students a more authentic laboratory experience in separations technology than experiments involving colored mixtures or compounds that are easily crystallized. In addition, students are required to use indirect visualization methods on a TLC plate to detect the major components of the original mixture and determine the success of the column chromatographic separation.

Enantioseparation of S,R‐(±)‐Ketoprofen on Plain Silica Gel Layers with Achiral Mobile Phase

Abstract: In an earlier study, we provided sufficient experimental evidence in favor of the hypothesis that—contrary to the conviction widespread among the practitioners of thin layer chromatography (TLC)—silica gel used for the coating of chromatographic plates is not amorphous, but microcrystalline and chiral. This evidence was procured both by the spectroscopic measurements of the circular dichroism of the binder‐free silica gel samples (manufactured specially for coating of the TLC plates) and by TLC measurements with densitometric detection. From the chromatographic measurements, it was found that silica gel employed in the planar chromatographic mode enables two‐dimensional enantioseparation of the racemic (or scalemic) mixtures of the selected test profens in the one‐dimensional development mode, without using chiral mobile phases. In our present study, this striking ability of the silica gel layers is further investigated with one more racemic mixture from the group of profens [i.e., S,R‐(±)‐ketopr...

Separation of multicomponent mixtures of pesticides by graft thin-layer chromatography on connected silica and octadecyl silica layers

Abstract: Mixtures of pesticides have been separated by graft thin-layer chromatography on connected layers — silica and octadecyl silica wettable with water. Separation of pesticide mixtures was achieved by two-dimensional planar chromatography using a non-aqueous mobile phase in the first dimension and an aqueous reversed-phase mobile phase in the second dimension.

HPTLC Method for Determination of 20-Hydroxyecdysone in Sida rhombifolia L. and Dietary Supplements

Abstract: Naturally occurring 20-hydroxyecdysone is an important anabolic ecdysteroid. A simple thin-layer chromatography method to quantitate 20-hydroxyecdysone in methanolic extract of the whole plant material of Sida rhombifolia L. was developed. This method was successfully applied for quantitative evaluation of dietary supplements. The separation was achieved on glass TLC plates coated with silica gel 60F254, using chloroform: methanol (8:2 v/v) as developing solvent. Densitometric evaluation of 20-hydroxyecdysone was performed at 250 nm in reflectance/absorbance mode. The calibration was in the range of 200–1,000 ng spot−1 and correlation coefficient for the calibration curve was >0.999. In addition, for six different Sida species unique fingerprints were obtained on the HPTLC plate.

Review of advances in the thin layer chromatography of pesticides: 2004-2006.

Abstract: Applications of thin layer chromatography and high performance thin layer chromatography for the separation, detection, and qualitative and quantitative determination of pesticides, other agrochemicals, and related compounds are reviewed for the period from July 1, 2004 to November 1, 2006. Analyses are covered for a variety of samples, such as food, crops, biological, environmental, pharmaceuticals, and formulations, and for residues of pesticides of various types, including insecticides, herbicides, and fungicides, belonging to different chemical classes. In addition to references on residue analysis, studies such as pesticide-structure relationships, metabolism, degradation, and lipophilicity are covered, many of which make use of thin layer radiochromatography.

Prenylated Flavonoids and Flavonostilbenes from Sophora pachycarpa. Roots

Abstract: Seven known compounds including three prenylated flavonoids (sophoraisoflavanone A, sophoraflavanone G, and 3′-isoprenylgenistein), two flavonostilbenes (alopecurone A and alopecurone B), in addition to two steroid glucosides (sitosterol 3-O.-glucoside and stigmasterol 3-O.-glucoside), were isolated using silica gel column chromatography and preparative thin layer chromatography from the roots of Sophora pachycarpa. C. A. Mey. (Papilionaceae) for the first time. The structures were characterized by 1D and 2D NMR experiments.

Analysis of counterfeit drugs by thin layer chromatography

Abstract: Economical and reliable thin layer chromatography methods for rapid screening of counterfeit drugs are described. The methods, which can be carried out in the field by inspectors with limited expertise, are based on the use of portable kits with standard reference tablets to eliminate weighing. Separations are performed on silica gel layers containing fluorescent indicator, and separated spots are detected under ultraviolet lamps and with iodine detection reagent. Development and iodine detection are carried out in polyethylene bags or glass jars. Sample spots are compared to reference standards developed on the same layer to identify the active ingredient and determine if its content is within the specification range. Additional methods described are visual inspection of packages and their contents and simple colorimetric tests for active ingredients, as well as column chromatographic and spectrometric methods for augmenting and validating TLC results.

Study of the oscillatory in-vitro transenantiomerization of the antimers of flurbiprofen and their enantioseparation by thin-layer chromatography (TLC)

Abstract: In our earlier studies on the spontaneous in-vitro oscillatory transenantiomerization of profens we investigated optically pure S-(+)-ibuprofen and S-(+)-naproxen and the racemic mixtures S,R-(±)-2-phenylpropionic acid and S,R-(±)-ketoprofen, which remained in a state of dynamic equilibrium between the two antimers yet also had the ability to transenantiomerize. In this study we have demonstrated, for the first time, the spontaneous oscillatory in-vitro transenantiomerization of S-(+)-flurbiprofen (an important non-steroidal anti-inflammatory drug, NSAID) and R-(−)-flurbiprofen, as monitored by polarimetry. It is also noteworthy that – as far as we are aware – this is the first report of separation of the enantiomers of flurbiprofen by TLC. This separation was achieved by two-dimensional development using a simple chromatographic system comprising a commercial silica gel layer impregnated with L-arginine as stationary phase and ethanol containing a few drops of glacial acetic acid as mobile phase. Unfortunately, this chromatographic system resulted in catalysis of structural conversion of the optically pure flurbiprofen enantiomer, either S-(+), or R-(−), to the scalemic or racemic mixture of the two antimers. This is an interesting contribution to general knowledge about the reactivity of this particular profen, although the spontaneous and rapid conversion observed prevents use of this TLC system for identification and quantification of individual flurbiprofen enantiomers.

Analysis of Flavonol Aglycones and Terpenelactones in Ginkgo biloba Extract: A Comparison of High-Performance Thin-Layer Chromatography and Column High-Performance Liquid Chromatography

Abstract: Advancements in automated high-performance thin-layer chromatography (HPTLC) have made it feasible to assess its use for the quantitative analysis of marker compounds in botanical preparations. We report here the findings of method comparisons for the terpenelactones and flavonol aglycones by column high-performance liquid chromatography (HPLC) with evaporative light scattering and UV detection, and HPTLC with a scanning densitometer. For the HPTLC assay of terpenelactones, total bilobalide, ginkgolide A, and ginkgolide B consistently achieved <70% of the total determined using HPLC, regardless of variations to postchromatographic derivatization time and temperature. Accuracy testing showed the possibility of a matrix interference. In contrast, a good relationship (95%) was determined between HPTLC and HPLC for determination of total flavonol glycosides (calculated from combined quercetin, kaempferol, and isorhamnetin) from an acid-hydrolyzed Ginkgo biloba L. (GBE) sample. The HPTLC flavonol aglycone method also performed well in terms of accuracy (overall average of 96% recovery for the 3 aglycones) and consecutive plate repeatability (overall percent relative standard deviation of 4.4). It is demonstrated that HPTLC can be a time-saving complement to HPLC for routine analysis of the flavonol glycosides in GBE.