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  • Author or Editor: Anna Petruczynik x
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The retention behavior of thirteen quinolines on cyanopropyl stationary phase was studied using different mobile phases prepared from mixtures of methanol, acetonitrile, 2-propanol, tetrahydrofuran, and dioxane with addition of buffer at different pH, ion-pairing reagents, or silanol blockers. Strong silanophilic interactions that can occur with these analytes and the adsorbent surface led to poor peak shape and resolution. Mobile phases containing anionic ionpair reagents such as sodium dodecyl sulfate, octanesulfonic acid sodium salt, or HDEHP were used to improve efficiency, peak shape, and selectivity. The effect of silanol blockers — different amines — on retention, efficiency, and peak shape for RP systems, was studied.

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The retention behavior of selected alkaloids on C18 and CN stationary phases in different eluent systems — mixtures of methanol and water with addition of buffers, acetic acid, ammonia, 1-octanesulfonic acid sodium salt, or diethylamine — has been determined. The separation of weak organic bases such as alkaloids is difficult because of their partial ionization in aqueous solutions. Improvement of separation selectivity, spot shapes, and system efficiency by use of special development methods: unidimensional multiple development (UMD), incremental multiple development (IMD), gradient multiple development (GMD), bivariant multiple development (BMD), and two-dimensional thin-layer chromatography (2D-TLC) was obtained. The effect of applied special development methods on chromatographic parameters obtained for investigated alkaloids in eluents of various composition on two layers was examined.

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Alkaloid standards have been chromatographed on silica layers with a variety of aqueous and nonaqueous mobile phases. The effect on retention, efficiency, and peak symmetry of pH, anionic ionpairs, DEA, and ammonia in aqueous mobile phases was examined. The effect of the concentration of ion-suppressing reagent — diethylamine — on retention, separation efficiency, and peak shape in normal-phase systems was also studied. Systems with the best selectivity and efficiency were used to separate alkaloid standards mixtures and plant extracts by 2D TLC.

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Ionic and ionizable solutes constitute a large group of compounds characterized with biological activity. Chromatographic analysis of these compounds is more difficult when compared to nonionic substances. This review focuses on different approaches used for the separation of basic and acidic substances by means of thin-layer chromatography. Biologically active basic compounds are more often used as prescribed drugs; therefore, chromatographic analysis of these substances was described in more detail when compared to acidic solutes.

Direct stimulus to write this review was the 65th anniversary of Prof. Monika Waksmundzka-Hajnos’ birthday. Prof. Hajnos is known for her great contributions to chromatographic analysis of ionic solutes.

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In this study, authors propose a simple and cost-effective two-dimensional thin-layer chromatography (2D-TLC) method for the simultaneous determination of eleven standards alkaloids: allocryptopine (A), berberine (Be), boldine (Bo), chelidonine (Ch), glaucine (G), papaverine (Pa), emetine (E), columbamine (Col), magnoflorine (M), palmatine (Pal), and coptisine (Cop). Separation of the alkaloid mixture was achieved by 2D-TLC using an aqueous mobile phase (RP) in the first dimension (80% methanol + water + 0.05 mL−1 diethylamine) and a normal phase (NP) in the second dimension (18% methanol, 18% acetone in 63% diisopropyl ether containing 1% ammonia, v/v) on bilayer Multi-K CS5 plates. The composition of the mobile phases was optimized in terms of retention, separation selectivity, spots symmetry, and system efficiency. The procedure was evaluated in terms of natural samples analysis. Magnoflorine and berberine were identified in Thalictrum foetidum root extract. Additionally, the alkaloids in the extract sample were confirmed by high-performance liquid chromatography—diode-array detection method.

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A simple and inexpensive two-dimensional thin-layer chromatography (2D-TLC) method was applied with mobile phase containing ionic liquid (IL) for the separation of ten components of a mixture of isoquinoline alkaloids such as allocryptopine (A), berberine (Be), boldine (Bo), chelidonine (Ch), papaverine (Pa), emetine (E), columbamine (Col), magnoflorine (M), palmatine (Pal), and coptisine (Cop). Separation of the alkaloid mixture was achieved by 2D-TLC using an aqueous mobile phase (RP) in the first dimension (80% methanol—water–0.05 M L−1 diethylamine) and a normal phase (NP) in the second dimension (75% methanol [MeOH], 24.75% ethyl methyl ketone–0.25% IL (1-butyl-3-methylimidazolium tetrafluoroborate) (v/v) on bilayer Multi-K CS5 plates. The procedure was evaluated in terms of natural samples analysis. Coptisine, palmatine, and berberine were identified in Rhizoma Coptidis (Huang Lian) extract. Additionally, the alkaloids in the extract sample were confirmed by high-performance liquid chromatography–diode-array detection (HPLC—DAD) method with application of a Synergi Polar RP column and a mobile phase consisting of a mixture of 25% acetonitrile (MeCN), 0.25% IL (1-butyl-3-methylimidazolium tetrafluoroborate), and 74.75% water (v/v). The composition of the mobile phases was optimized in terms of retention, separation selectivity, spots symmetry, and system efficiency. Limits of detection (LODs) were from 0.10 and 0.13 μg mL−1 and limits of quantification (LOQs) between 0.31 and 0.41 μg mL−1.

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Coumarins are natural, biologically active substances, normally found in complex mixtures. Unfortunately their separation causes many difficulties, because of to their similar chemical structure and physicochemical properties. A new, reliable method has been established for analysis of coumarin fractions present in selected fruit extracts. The substances were separated in chromatographic systems that enabled use of orthogonal separation mechanisms (i.e. characterized by different selectivity). The greatest selectivity differences were obtained by use of two chromatographic systems — first dimension CN-silica with 30% ACN in H 2 O as mobile phase (triple developed) and second dimension SiO 2 with 35% AcOEt in n -heptane as mobile phase (triple developed), or first dimension SiO 2 with 35% AcOEt in n -heptane as mobile phase (triple developed) and second dimension RP-18 with 55% MeOH in H 2 O as mobile phase. The aforementioned two-dimensional TLC systems were used for separation of coumarin fractions present in extracts from Archangelica officinalis, Pastinaca sativa and Heracleum sphondylium fruits .

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Coumarins are interesting group of natural compounds, because of their biological and pharmacological activity, and are widely investigated. They are normally found in complex mixtures, e.g. plant extracts, and are difficult to separate in one chromatographic run. Mixtures of coumarins have been separated by two-dimensional thin-layer chromatography on CN-silica plates by use of aqueous and nonaqueous mobile phases. Complete separation was also achieved by use of graft thin-layer chromatography on connected layers — silica with RP-18W or CN-silica with silica. The systems characterized by the best efficiency and selectivity were used for separation of coumarin fractions from extracts of selected Apiaceae plants. These orthogonal systems were used for quantitative analysis of selected coumarins. The results obtained show two dimensional thin-layer chromatography is useful tool for quantification of some furanocoumarins in plant extracts. The best results were obtained on connected silica and octadecyl silica layers.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Maria Gadzikowska, Anna Petruczynik, Monika Waksmundzka-Hajnos, Mirosław Hawrył and Grzegorz Jóźwiak

Plant extracts from Datura innoxia Mill. contain tropane alkaloids which are pharmacologically active, and compounds used in medicine are isolated industrially from the plant. Control of the composition and content of these alkaloids is, therefore, an important task. Thin-layer chromatography is an effective method for analysis of these compounds, because they are difficult to detection with UV light. In the work discussed in this paper separation of closely related alkaloids was achieved by two-dimensional TLC in optimized NP and RP systems by use of multiphase plates. The work enabled identification of tropane alkaloids present in plant extracts. Normal-phase separation on silica layers was optimized for quantitative analysis of the alkaloids scopolamine and tropine and the sum of atropine and homatropine.

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