Diol Plates Research Articles

High performance thin-layer chromatography–mass spectrometry methods on diol stationary phase for the analyses of flavan-3-ols and proanthocyanidins in invasive Japanese knotweed

We developed the first four HPTLC methods for the separation of proanthocyanidins according to degree of polymerization on HPTLC diol F254S plates. Acetonitrile, ethyl acetate, ethyl acetate–formic acid (9:0.1, v/v) and toluene–acetone–formic acid (3:6:1, v/v) were used as developing solvents and 4-dimethylaminocinnamaldehyde (DMACA) as the detection reagent. Each of these methods enables separation of standards of procyanidin dimers from procyanidin trimer (procyanidin C1) and separation of B-type dimers (procyanidins B1, B2, B3) from A-type dimers (procyanidins A1, A2). Based on these HPTLC methods we developed four new HPTLC-MS/MS methods for analyses of proanthocyanidins on HPTLC diol F254S plates and we identified B-type proanthocyanidins from monomers up to decamers in crude extracts of invasive Japanese knotweed (Fallopia japonica Houtt., Polygonum cuspidatum Sieb. & Zucc.) rhizomes. Monomers, monomer gallates, dimers, dimer gallates, dimer digallates, trimers, trimer gallates, tetramers, tetramer gallates, pentamers, pentamer gallates, hexamers, hexamer gallates, heptamers, octamers, nonamers and decamers were tentatively identified in Japanese knotweed rhizomes using developing solvents acetonitrile and toluene–acetone–formic acid (3:6:1, v/v). Ethyl acetate enabled separation from monomers up to hexamer gallates and ethyl acetate–formic acid (9:0.1, v/v) from monomers up to hexamers. During the five hours of stability testing of (–)-epicatechin and procyanidin B2 standards on HPTLC diol plates developed with all solvents we observed enhanced absorption at 280 nm. This was a totally unexpected phenomenon. This new discovery confirmed what we reported in our previous study on HPTLC silica gel. Enhanced absorption is influenced by the developing solvent (more than 30%), the stationary phase (up to 24%) and the light (up to 15%).

Chromatographic analysis of simple phenols in some species from the genus Salix

Salicis Cortex, made from willow bark is a herbal remedy, which is standardised based on the content of salicin, a compound with analgesic and antiphlogistic properties. However, clinical trials suggest that other compounds also present in Salicis Cortex can contribute to the pharmacological effects. To characterise the composition of phenolic acids in the barks of different species and clones from the genus Salix by use of chromatographic methods--HPTLC and HPLC. The phenolic acid composition was analysed by MGD (multiple gradient development)-HPTLC technique. The separation was performed on HPTLC Diol plates with gradient elution using a mixture of chloroform:hexane:ethyl acetate with increasing concentration of ethyl acetate from 10 to 25%. Derivatisation with thymol reagent was employed for the first time for specific detection of phenolic acids containing methoxyl groups. The presence of all phenolic acids previously reported in the genus Salix was confirmed, namely p-hydroxybenzoic, vanillic, cinnamic, p-coumaric, ferulic and caffeic acids. Furthermore, pyrocatechol as a constituent of willow bark was revealed. The highest concentration of this compound was observed in the S. purpurea bark (2.25 mg/g). The presence of a relatively high content of pyrocatechol in Salix species may raise doubts about the safe application of this herbal medicine.

Analysis of some fibrate-type antihyperlipidemic drugs by AMD

Conditions have been established for separation of six fibrate drugs by automatic multiple development (AMD). The best system was selected by using results from systematic investigation of relationships between R M values and mobile-phase composition. The drugs were separated by multiple development on diol plates with tetrahydrofuran-hexane as mobile phase. The results of multiple development analysis predicted by computer simulation were compared with experimental results.

Separation of Selected Bile Acids by TLC. VI. Separation on Cyano‐ and Diol‐Modified Silica Layers

Seven selected bile acids: cholic acid (C), glycocholic acid (GC), glycolithocholic acid (GLC), deoxycholic acid (DC), chenodeoxycholic acid (CDC), glycodeoxycholic acid (GDC), and lithocholic acid (LC) were separated on silica gel modified by cyano and diol groups, with the use of a mobile phase: n‐hexane–ethyl acetate–acetic acid in different volume compositions, at 18°C. The estimation of separation was carried out on the basis of the separation factors values: ΔRF and RS. Almost all bile acids, except for CDC/DC, were completely separated on cyano‐modified silica plates when a mobile phase n‐hexane–ethyl acetate–acetic acid in the volume composition 49:49:2 was used; whereas, the optimal separation for all examined bile acids was obtained on diol plates, using a mobile phase n‐hexane–ethyl acetate–acetic acid in the volume composition 42:42:16.

The retention behavior in normal-phase chromatographic systems of some fibrate-type antihyperlipidemic drugs

Relationships between R M values and mobile phase composition have been determined for the six antihyperlipidemic agents-bezafibrate, ciprofibrate, clofibrate, clofibric acid, fenofibrate, and gemfibrozil. The drugs were separated on silica gel, CN, and Diol plates using mobile phases containing n -hexane as weakly polar diluent and five polar modifiers: acetone, dioxane, ethyl methyl ketone, ethyl acetate, and tetrahydrofuran. The optimum mobile phases were also investigated on alumina, NH 2 , and polyamide phases for comparison. The linearity of relationships between R M and modifier volume fraction, molar fraction, and logarithm of molar fraction was calculated. Plates were developed in horizontal chambers, visualized under UV irradiation at λ = 254 nm, and scanned with a densitometer in the multi-wavelength scan mode. Most results fitted the Snyder-Soczewinski equation with r > 0.9; for approximately half r > 0.99. Separation of all the drugs was achieved on Diol plates with mobile phases containing 2...

Multiple gradient development TLC in analysis of complex phenolic acids fromLycopus europeaus L.

Phenolic acids fromLycopus europaeus L. (Lamiaceae) were chromatographed on thin layers of precoated silica, LiChrospher silica, propylamine, diol layers using stepwise multiple development and, additionally, on an octadecyl layer with an isocratic mobile phase. The eluent contained decreasing concentrations of formic acid in a mixture of diisopropyl ether-cyclohexane for silica gel plates or methyl-ethylketone inn-hexane for diol plates and increasing concentrations of acetic acid in acetone for the propylamine layer. Extracts were separated into 25 components, 14 of which were identified using a mixture of standards. 2,4-Dihydroxybenzoic, gentisic, protocatechuic and 3,5-dihydroxybenzoic acids were ascribed to this genus for the first time. The adsorbent-eluent systems described were very efficient and rapid.

Retention characteristics of CN, NH 2 and diol precoated high-performance thin-layer chromatographic plates in the adsorption and reversed-phase separation of some benzodiazepine derivatives

The retentions of eighteen benzodiazepine (BZD) derivatives on CN, diol and NH 2 high-performance thin-layer chromatographic layers was determined using eight adsorption (carbon tetrachloride-ethyl acetate) and five reversed-phase (water-methanol) eluent systems. In most instances a linear correlation was found between the R M value of BZD and the ethyl acetate or methanol concentration in the eluent, which allows the calculation of the optimum eluent composition. In aqueous eluents the lipophilicity of BZD determines the retention, that is, the plates behave as real reversed-phase stationary phases. The differences in the reversed-phase retentions of BZD were lower than in adsorption chromatography, advocating the application of adsorption chromatography for their separation. The low retention capacity and elongated spot shape make the NH 2 plate unsuitable for the reversed-phase separation of BZD without further modification of the composition of the mobile phase. As chlordiazepoxide and medazepam form distorted spots on CN and diol plates, for the best separation of these BZD, NH 2 plates in the adsorption separation mode are recommended.