Thin Layer Chromatographic Separation of Ortho,Meta, and Para Substituted Benzoic Acids and Phenols with Aqueous Solutions of α-Cyclodextrin

Abstract

The use of aqueous solutions of α-cyclodextrin as the mobile phase in thin layer chromatography (TLC) is described. A series of eighteen substituted benzoic acid compounds were chromatographed on polyamide thin layer sheets. The R_f values were dependent on the concentration of α-cyclodextrin in the mobile phase as well as the structure and size of the individual molecules. Possible advantages of this technique over those which use pure or mixed solvent systems as the mobile phase are discussed.     

Coupling protocol for thin layer chromatography/matrix-assisted laser desorption ionization

Summary This paper reports the investigation and optimization of the thin layer chromatography/matrix-assisted laser desorption/ionization (TLC-MALDI) coupling protocol. The fundamental coupling parameters which influence sensitivity and lateral analyte spreading are extraction solvent selection, extraction time, and pressure. Selection of the solvent is dependent upon its extraction efficiency, which has been correlated with extraction solventR _f value. Maximum extraction efficiency occurs after two minutes for the analyte/solvent system studied. High extraction efficiency solvents cause significant lateral spreading of analyte; up to a three-fold increase in initial analyte spot size. Analyte recovery was found to be limited by the silica gel inter-partice porosity and the solvent extraction efficiency. For maintaining chromatographic resolution and maximizing signal intensity, extraction solvents withR _f values between 0.4 to 0.6 are optimal. The upper analyte recovery limit, using extraction solvents within thisR _f range, is estimated at 22%. Dedicated to Professor Werner Haerdi on the occasion of his 70^th birthday.     

Thin-Layer chromatography of inorganic ions on cellulose phosphate in sulfuric acid-organic solvent media

Summary Thin-layer chromatographic behavior of 49 inorganic ions on cellulose phosphate (P-cellulose) has systematically been surveyed with binary solvent mixtures consisting of sulfuric acid and an organic solvent such as methanol or acetone. The R_f values of many bivalent and monovalent ions as well as Te(VI) decrease on the P-cellulose layer with an increasing concentration of the organic solvent. Polyvalent ions which form strong phosphato-complexes and precipitate insoluble sulfate are strongly retained on P-cellulose. Oxy-anions, Au(III) and Pt(IV) are not adsorbed on the cellulose to any great extent. Feasibilities of the separation of multicomponent mixtures are demonstrated on the P-cellulose layer.     

Die Dünnschichtchromatographie von Thalidomid und seinen Hydrolyseprodukten

Zusammenfassung Eine neue dünnschichtchromatographische Methode zur Trennung von Thalidomid und seinen Metaboliten wurde beschrieben. Die günstigsten Ergebnisse erhält man auf Schichten von Kieselgel G bzw. GF₂₅₄ mit verschiedenen Laufmittelsystemen. DieR _f -Werte von Thalidomid und zwölf Hydrolyseprodukten werden angegeben.

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Thin-layer chromatography of thalidomide and its hydrolysis products

Summary A new method for the separation of thalidomide and its metabolites by thin layer chromatography is described. The most favorable results are obtained on layers of Kieselgel G and GF₂₅₄ respectively with various solvent systems. TheR _f -values of thalidomide and twelve hydrolysis products are given.

     

The Effect of Substituent Groups on the Migration of Metal Ions in Thin Layer Chromatography

Abstract

A reverse phase thin layer partition chramotography has been performed on metal ions using silica gel G as an adsorbent. The effect of chlorosubstituent groups on the migration of cations has been studied. The use of aqueous solutions of acetic acid, monochloro, dichloro and trichloro acetic acid in the solvent system revealed profound effect of substituent groups on the R_f values of metal ions. The effect of concentration and pH of the mobile phases have been studied. Many qualitative ternary separations have been sucessfully achieved.     

Mycotoxin separation on thin layer of corn starch

Summary Twelve mycotoxins were separated on corn starch thin layers with the solvent systems: benzene, toluene, xylene and mixture of benzene-toluene-cyclohexane-ethanol (abs.) (3:3:5:0.1). R_f-values were determined. The effect of solvent systems on mycotoxin fluorescence was also described.     

HPTLC separation of platinum metal 8-hydroxyquinolinates

High performance thin layer chromatography has been used to separate all the platinum metal 8-hydroxyquinolinates on polar stationary phases. The dependence of R_f values on the composition of mobile phases prepared from chloroform – tetrahydrofuran or chloroform – alcohol mixtures has been investigated. Retention was found to be partially dependent on alcohol chain length in chloroform – alcohol systems. The results obtained from TLC are dependent on the method of sample preparation used for the analyte.     

The Effect of Binary Solvent Composition and Polarity on Separations in Reversed Phase Thin Layer and High Performance Liquid Chromatography

Abstract

The effect of the solvent's composition and polarity on separation in reversed phase thin layer and high performance liquid chromatography is discussed. These results show that retention times cannot be predicted merely from the polarity of the binary mobile phase. Although organic modifiers with the same physico-chemical properties and from the same solvent group were used, the retention times obtained using binary mobile phases having the same polarity, were different. It was also observed that normal chain carbon alcohols gave retention times different from those with a branched chain (n-propanol vs. iso-propanol), and the longer the alcohol chain the higher the R_f value. The results also show that not only the organic modifier used is important but the solute mixture used.     

How Many Molecular Layers of Polar Solvent Molecules Control Chemistry? The Concept of Compensating Dipoles

The extension of the solvent influence of the shell into the volume of a polar medium was examined by means of anti‐collinear dipoles on the basis of the E_T(30) solvent polarity scale (i.e., the molar energy of excitation of a pyridinium‐N‐phenolatebetaine dye; generally: E_T=28 591 nm kcal mol^?1/λ_max) where no compensation effects were found. As a consequence, solvent polarity effects are concentrated to a very thin layer of a few thousand picometres around the solute where extensions into the bulk solvent become unimportant. A parallelism to the thin surface layer of water to the gas phase is discussed.     

The Behavior of Some Carboxy and Hydroxy Benzene Derivatives on Thin Layers of Plain and Fe(III)-Impregnated Silica-Gel

Abstract

The behavior of some carboxy and hydroxy benzene derivatives related to lignin and humic materials was examined by thin layer chromatography on plain and Fe(III)-impregnated silica-gel plates, in three solvent systems. The mobility differences on impregnated and plain plates, expressed as R_i values, were calculated and can be used as one of the parameters for identification of the compounds tested.     

Separation Studies of Metal Ions in Sodium Thioglycolate Medium by Thin Layer Partition Chromatography

Abstract

A thin layer partition chromatographic method has been developed for separation of Fe(III), Ni(II), Zn(II), Cu(II), Pb(II) and Mn(II) on thin layers of silica gel-G as an adsorbent. The R_f values were determined using 0.01–0.2 aqueous solution of sodium thioglycolate as a mobile phase. The dependence of R_f values on the migration time, pH and concentration of mobile phase has been studied. The optimum conditions for possible 3-component separation have been determined. Metal ions have been separated, detected, eluted and quantitatively determined by atomic absorption spectroscopy. The present method was applied to the separation and determination of zinc in forensic samples.     

Fluoro-ketones IV. Synthesis of phenylperfluoroalkyl ketones - mechanism of reaction between phenyllithium and fluoroesters

Although fluorine containing ketones (R_fC(O)R_f and R_fC(O)R, R_f = perfluoroalkyl) have been prepared from the reaction between organolithium reagents and perfluoroalkyl esters, the reaction has not found general applicability. Variable yields of ketones and co-production of secondary and tertiary alcohol by-products have in most instances been experienced. We have examined in more detail the factors e.g., temperature, mode of addition and perfluoroalkyl ester structure which influence ketone product and by-products formation. By controlling experimental conditions excellent yields of C₆H₅C(O)R_f compounds can be attained. A lithium salt of a hemiketal (II) has been isolated and shown to be the active intermediate in the production of the ketone. The stability of the salt and its potential reaction with the solvent dictates the type of reaction products. Low temperature favors stability of the lithium salt of the hemiketal whereby high yields of ketones are produced on hydrolysis.     

The thin-layer chromatography of dinucleotides

Conclusions 1. The chromatographic behavior of the dinucleotides of an RNA hydrolysate in thin layers of ECTEOLA- and DEAE-cellulose and on a cellulose powder has been studied. The Rf values of the four dinucleotides A_pC_p, A_pU_p,G _pC_p andG _pU_p in various solvent systems have been determined. It has been shown that in a thin layer of DEAE cellulose the dinucleotide fraction of a ribonuclease hydrolysate is separated into the four individual components.2. Conditions for the separation of authentic mixtures of dinucleotides and of mixtures of mono- and dinucleotides have been found.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 4, pp. 287–291, 1969     

Physicochemical Nature of Perfluoroalkyl Compounds Induced by Fluorine

Perfluoroalkyl (R_f) compounds have unique characters represented by a significantly high hydrophobic property, which often makes us consider that R_f groups should be interacted with each other via the ‘hydrophobic interaction’ as found for a normal hydrocarbon. Due to a similar intuitive and simplistic speculation, the R_f‐specific material properties have long been enveloped in darkness for comprehensive understanding, which should lucidly be discussed within a framework of physical chemistry. Here, we show studies on the stratified dipole arrays (SDA) theory, which readily explains the R_f‐specific material characters in a comprehensive manner based on only a few fundamental physical parameters of fluorine. The SDA theory encompasses some conventional theories that account for only a part of material properties. In addition, we show that the concept of vibrational spectroscopy of R_f compounds should also be revised, since the mass of fluorine is larger than that of carbon, which is opposite to the hydrocarbon case. In this manner, chemistry of R_f compounds needs another fully revised concept, which cannot be replaced by an extended concept of normal hydrocarbon compounds.     

Beitr?ge zur Papierchromatographie organischer Substanzen

Zusammenfassung Ungesättigte Verbindungen, hauptsächlich Olefine C₂–C₁₂, werden als Quecksilber(II)-salze mit Hilfe der Papierchromatographie und Dünnschichtchromatographie aufgetrennt. Geeignete Lösungsmittelgemische werden angegeben und die Zusammenhänge mit Fleckengröße und R_f-Werten graphisch dargestellt.

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Summary Unsaturated compounds, mainly olefines C₂–C₁₂, are separated in form of their mercuric salts by help of chromatography on paper or on thin layers of silica gel. Suitable solvent mixtures are given and their relations to spot sizes and R_f-values are represented in graphs.

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IV. Mitteilung: Kabil, A., u. V. Prey: Mh. Chem. 89, 497 (1958).     

Analysis time in conventional and continuous development thin-layer chromatography

Equations for predicting analysis time in thin-layer chromatography as a function of spot separation, solvent velocity constant, ΔR_f and R_f, are presented and discussed.     

Vapor-controlled thin-layer chromatography on reversed-phase layers

The chromatographic behavior of some hydrocarbons and some of their nitro derivates after preconditioning with solvent vapors has been investigated. After preloading with cyclohexane or hexane an improved separation of some sample pairs is observed. Furthermore, inversion of R_f values takes place. The preloading of the reversed-phase plates permits utilization of mobile phase with higher water content, thus leading to a significant shortening of developing time.     

Reactions of perfluoronitriles. II. Interactions with phenylphosphine

Treatment of perfluoro-n-octanonitrile with phenylphosphine gave tetraphenyltetraphosphine and a spectrum of reduction and interaction products. Fifteen compounds were identified. The imine, (R_fC₇F₁₅) R_fCHNH, and the amine, R_fCH₂NH₂, were the primary reduction products. Secondary phosphorus-free products, some formed following ammonia evolution, were the following: R_fCHNCH₂R_f, R_fCH₂CH(NH₂)R_f, R_fC(NH)NCR_f(NH₂), R_fCH₂NHCR_f(NH), (R_fCN)₃, R_fCHNCR_fNCR_f(NH), R_fCH₂NCR_fNHCH₂R_f, and R_fCH₂NCR_fNHCR_f(NH). Only three phosphorus-containing materials were definitely identified: R_fCH(NH₂)P(C₆H₅)H, R_fCH[P(C₆H₅)H]NCHR_f, and R_fC(NH)P(C₆H₅)CR_f(NH). Depending on reaction conditions, specific phosphorus-containing compounds could be preferentially produced. All the structure assignments are based solely on mass spectral breakdown patterns, since pure compounds were not isolated.     

Isolierung,Identifizierung und quantitative Bestimmung neutraler und saurer Arzneimittel

Zusammenfassung Zur Isolierung der sauren und neutralen Arzneimittel aus biologischem Material wird in den Untersuchungsgang vonStas-Otto die Dünnschicht-chromatographie zweckentsprechend eingebaut. Dieses Verfahren erlaubt die Isolierung und Erkennung der meisten praktisch in Betracht kommenden Verbindungen im Verein mit chemischen und physikalisch-chemischen Identifizierungsmethoden. Die Einfachheit der Dünnschichtchromatographie wird durch die Verwendung von nur drei Elutions- und wenigen Sprühmitteln gewahrt. Die angegebenen R_f-Werte zahlreicher Verbindungen ermöglichen dem Toxikologen eine rasche Orientierung bei der Auffindung unbekannten Substanzen.

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Summary Thin layer chromatography has been appropriately incorporated into theStas Otto investigative procedure in order to isolate the acid and neutral drugs from biological material. This procedure permits the isolation and recognition of most of the compounds that come into practical consideration in connection with chemical and physico-chemical identification methods. The simplicity of thin layer chromatography is preserved by the use of only three eluants and only a few spraying agents. The stated R_f-values of numerous compounds make it possible for the toxicologists to arrive at a speedy orientation when confronted with unknown substances.

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Herrn Prof. Dr.H. Lieb zu seinem 80. Geburtstag gewidmet.