Two-dimensional thin-layer chromatography of selected coumarins

Polar-bonded stationary phases (CN-silica and Diol-silica) are used with nonaqueous eluents in adsorption mode or with aqueous eluents in partition mode. This enables the application of these systems in two-dimensional separations because of the different selectivity and application to the separation of closely related compounds of similar physicochemical properties and retention behaviour. Similarly, multiphase plates, connected with C18 strips and silica layers, are used with aqueous and nonaqueous eluents. Such layers were applied for the separation of selected coumarins. Thus, differences in separation selectivity are applied for the separation of coumarin fractions from plant extracts of the Apiaceae family by two-dimensional thin-layer chromatography.     

薄层色谱法拆分手性药物对映体

用性能稳定的薄层色谱用β-环糊精(β-CD)、硅胶手性固定相拆分手性药物对映体.在适当比例的乙腈-1%乙酸三乙胺(TEAA)、己烷-异丙醇、乙腈-甲醇-乙酸-三乙胺、甲醇-1%TEAA及乙腈-1%TEAA-三乙胺溶剂系统中展开,8种临床常用的手性药物对映体得到有效分离,对映异构体之间的相对比移值α为1.53～4.89.     

The application of triphenylmethane dyes to visualization of selected aliphatic compounds in thin-layer chromatography

Selected triphenylmethane dyes were used as new visualizing agents in thin-layer chromatography of higher fatty acids, higher fatty alcohols, and higher aliphatic amines.     

Application of thin-layer chromatography in enantiomeric chiral analysis-an overview

Several chiral drugs are produced and administered as pure enantiomers, whereas many others, especially of synthetic origin, are used mainly in the form of racemates. The biological and pharmacological activity of chiral compounds depends on their configuration. The racemic drugs may exhibit quite different activity from the optically pure drugs. Often only one of the enantiomers is pharmacologically active and/or even can be toxic. Since numerous enantiomers have been shown to behave differently from at least one point of view, whether pharmacokinetic, pharmacodynamic, toxicological or interaction, there seems to be hardly any exception to the general rule that a racemate cannot be considered as a single drug entity. A variety of chromatographic methods have been developed for optical resolution recently. Usually direct separation of the enantiomers is carried out on HPTLC chiral precoated plates or on plates impregnated with chiral substances. TLC techniques are a developing branch of separation and quantitation of drugs, both in pharmaceutical dosage forms and in biological material. This review presents an overview of the current successful enantioseparations of drugs by TLC and their potential in the analysis of the drug racemates.     

Two-dimensional thin-layer chromatography of selected Polygonum sp. extracts on polar-bonded stationary phases

Two-dimensional thin-layer chromatographic systems on cyano-bonded polar stationary phases were used for the separation of some phenolic compounds extracted from two species of Polygonum: Polygonum hydropiper L. and Polygonum cuspidatum L. Non-aqueous solvents were used in the first direction and aqueous solvents were used in the second direction on CN silica TLC plates. For the separation of phenolics' standards optimal chromatographic systems were chosen from the retention data collected in one-dimensional TLC experiments by plotting graphs of R(F) vs. R(F) dependencies. Using above described method the satisfactory results of separations were obtained.     

Graphical and visualizing method of identification of selected groups of aliphatic compounds in thin-layer chromatography

A new method of group identification was established for selected aliphatic compounds giving homologous series, based upon constant ΔR_M and directional coefficient “a” values (the “a” values being tangents of the angle between the course of the R_M = f(n_c) function and the “x” axis).The results presented concern identification of higher fatty acids and their ethyl esters, amides of higher fatty acids, higher aliphatic amines, ethylalkyl ketones, and dicarboxylic acids.Simultaneously, another method of identifying groups of aliphatic compounds was established, taking advantage of differentiated visualizing effects.     

Practitioner's guide to method development in thin-layer chromatography

The authors provide a personal perspective of method development in thin-layer chromatography for the novice and more experienced chromatographer alike. No attempt has been made at a comprehensive survey of the literature. Instead we provide an overview with insights into a smaller number of approaches that the authors have found useful in their own work and indicate the factors responsible for the variation in retention and their control. The main topics covered are the relationship between sorbent chemistry and retention, the selection of primary solvents for mobile phase optimization and mobile phase optimization using the PRISMA and solvation parameter models.     

Application of preparative liquid chromatography to the isolation of enantiomers of a benzodiazepinone derivative.

The isolation of milligram amounts of the enantiomers of a benzodiazepinone derivative was performed on an analytical cellulose tribenzoate-based column by multiple repetitive injections. An enantiomeric purity greater than 98% was required. First, an analytical method was developed to maximize the resolution by adjusting the mobile phase composition, flow-rate and most importantly the column temperature. Then the preparative separation was optimized by adjusting the sample size and detecting the sample where its UV absorbance was low. The locations of the cut points were determined by use of detector response levels. The method development, preparative separations and analytical assays of the fractions obtained were all performed on analytical columns.     

Determination of betaxolol enantiomers by high-performance liquid chromatography. Application to pharmacokinetic studies

A high-performance liquid chromatographic (HPLC) method is described for the determination of (R)- and (S)-enantiomers of betaxolol in blood and other biological fluids. Separation of the enantiomers is performed after preparation of diastereomeric derivatives with the chiral reagent R(-)-naphthylethylisocyanate by reversed-phase HPLC. Fluorimetric detection allows the quantification of betaxolol enantiomers down to 0.5 ng/ml. This method was used to evaluate the pharmacokinetic profile of the betaxolol enantiomers in three subjects following one single oral dose (20 mg) of racemic betaxolol. No significant difference was observed in blood levels of the isomers.