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.     

Separation of coumarins from Archangelica officinalis in high-performance liquid chromatography and thin-layer chromatography systems

Complex, multicomponent mixtures are difficult to separate in a single chromatographic run. Therefore, the possibility to separate twelve coumarins from Archangelica officinalis was studied by combining a HPLC and a TLC system. HPLC optimized by the use of DryLab for Windows software was performed on RP-18 column and TLC was performed on silica plates. Fractions from the RP column were evaporated, applied on silica plate and developed in non-aqueous solvent. Possibilities of complete separation of investigated coumarins were discussed in RP and NP systems. The result of their complete separation was presented by HPLC chromatograms, DryLab simulated chromatograms and a video scan of TLC plate.     

Retention behaviour of some coumarins in normal-phase high-performance thin-layer and column chromatography

Summary A number of coumarins, furocoumarins and pyranocoumarins were investigated using HPTLC and HPLC systems consisting of silica gel and binary and ternary solvents containing a polar modifier (acetonitrile, dioxane, diisopropyl ether, methyl ethyl ketone, ethyl acetate, 2-propanol or tetrahydrofuran) and a non-polar or weakly polar diluent (n-heptane or dichloromethane). The experimental results obtained on thin layers, under isocratic conditions, showed a linear relationship between the R_M values and the log of the concentration of the polar modifier.The influence of the modifier and the individual substituents in the solute molecule on retention is presented as chromatographic spectra by plotting the R_M and logk values against the mobile phase used.Preliminary communication of this work was presented at the 46th International Congress of Pharmaceutical Sciences, in Helsinki, Finland, 1–5 September, 1986.     

Two-dimensional thin-layer chromatography fingerprint profiles of ten Cirsium species by chemometric processing

JPC – Journal of Planar Chromatography – Modern TLC - Ten methanolic extracts of selected Cirsium species were analyzed using two-dimensional thin-layer chromatography (2D-TLC) system...     

Two-dimensional thin-layer chromatography with adsorbent gradient as a method of chromatographic fingerprinting of furanocoumarins for distinguishing selected varieties and forms of Heracleum spp

There are a lot of taxonomic classifications of the genus Heracleum, and many authors indicate they need revision. Morphological identification is difficult to perform, as there are only few characteristic differences between each Heracleum species, varieties and forms. Furanocoumarins are characteristic compounds for the Apiaceae family, and they can be found in the whole genus in large quantities. Despite this fact, it is difficult to use the furanocoumarin profiles of plants, for their discrimination, as furanocoumarins are difficult to separate, due to their similar chemical structures and physicochemical properties. In this paper, a new, simple method is proposed for the discrimination of selected species, varieties and forms of the genus Heracleum. Thin-layer chromatography (TLC) with an adsorbent gradient (unmodified silica gel+octadecylsilica wettable with water) enables complete separation of the structural analogues. The proposed method gives the possibility to distinguish selected species, varieties and forms of the Heracleum genus, as they produce distinctive furanocoumarin fingerprints. The method is characterised by high specificity, precision, reproducibility and stability values. It is for the first time that graft TLC is used for constructing fingerprints of herbs. The complete separation of ten structural analogues, by combining gradient TLC with the unidimensional multiple development technique, has not been reported yet.     

Overpressured thin-layer chromatography

The properties, apparatus and applications of overpressured thin-layer chromatography (OPTLC) have been reviewed. In the Introduction planar chromatography has been briefly characterized, with particular attention to TLC. The general properties of OPTLC and methods of development of chromatograms in this technique have been then given. The construction of chambers and equipment for OPTLC has been described, paying attention to two-dimensional columns. The properties of chambers for OPTLC have been characterized considering the flow of eluent, sorbent-eluent interactions and the efficiency of various systems. OPTLC, TLC and HPTLC have been compared and also a comparison between OPTLC with a constant (linear) eluent flow-rate and with a decreasing eluent flow-rate has been made. Analytical applications of OPTLC have been described and examples of separations of mixtures have been given.     

Cone thin-layer chromatography

A new variant of chromatography, cone chromatography, is suggested. In this variant, a thin-layer chromatography (TLC) plate on a flexible support (for example, foil) is cone-shaped. This variant is compared with the classic linear and circular variants using chromatographic characteristics (retardation factor R _f and efficiency H, μm) and the time of chromatographing with ethanol as a mobile phase. Cone chromatography is intermediate in the series linear-cone-circular TLC variants.     

Three-dimensional thin-layer chromatography

A three-dimensional variation of planar chromatography is proposed and realized. In this new variation of planar chromatography, components of the mixture under investigation migrate under the action of the mobile phase flow in one direction, then in another direction at an angle to the first direction, and then in a third direction at an angle to the second direction; in this case, all elution processes are carried out using different volatile eluents and drying the plate between the three elution processes. Using the example of separation of a mixture of dyes, it is shown that three-dimensional planar chromatography is appropriate for practical purposes.     

Effects of modifier and molecular structure of some coumarins on retention in reversed-phase high-performance thin-layer and column chromatography

Coumarins, furocoumarins and pyranocoumarins (29 compounds) were investigated in silanized silica (HPTLC RP-2 and RP-18 and HPLC RP-18)-water organic modifier (methanol, acetonitrile, dioxane, tetrahydrofuran and methanol containing acetic acid) systems. The physico-chemical properties of these compounds were characterized by their hydrophobicity parameters (RMw), determined by extrapolation of the linear relationships for retention data in binary solvent systems [RM = f(phi)] to pure water. The effect of individual substituents on retention was quantified by using the group contribution parameter delta RM or delta log k'.     

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.