Some effective solvent systems for the rapid resolution of DNP-amino acids by thin-layer chromatography

Summary The DNP-amino acids have been divided into two groups depending upon their chromatographic behaviour on silicagel thin layers in different solvent systems. Five solvent systems were developed for each of the two groups. The systems reported provide rapid resolution and can separate mixtures of six to eight DNP-amino acids. The systems provide separations of DNP-ala/pro, leu/phe and leu/ile which are difficult to separate by one-dimensional TLC.     

A rapid separation of citrus carotenoids by thin-layer chromatography

Summary A rapid separation of citrus carotenoid pigments is achieved by successive thin-layer chromatographic separations on two different adsorbents. The first chromatography on silica gel G developed with the solvent system acetone-petroleum ether (30∶70) gives a preliminary fractionation into groups with different polarity (hydrocarbons, monols, diols and polyols). A further separation of each group into individual carotenoids is obtained by rechromatography on MgO-Kieselguhr (1∶1, w/w). The same solvent system is used, the acetone percentage being increased according to the polarity of each group (from 4% to 30%).     

Effect of halides on the TLC resolution of amino acids below their isoelectric points

TLC of a fifteen component mixture of amino acids has been carried out in two ways; firstly, the amino acids were treated with halides below their isoelectric points and chromatographed on plain silica plates, and secondly the amino acids in their cationic forms were chromatographed on silica plates impregnated with halides, keeping the same solvent system. The resolution is considered to be affected by hydrophobic interactions between silica gel and amino acid molecule and by the polarity and the flow of the mobile phase. The method provides resolution of 10–11 amino acids from the fifteen component mixture.     

New strategy for the identification of amino acids by TLE and TLC using basic or buffered mobile phases

Summary Direct, simple and reliable means for characterization of the common amino acids, using mixtures of structural analogues of amino acids and combinations of low-voltage electrophoresis (1.04 mol dm^–3 formic acid) and chromatography (tert-butanol/methanol/pyridine/formic acid/water, 33:43:9.6:0.4:20, v/v, methanol/pyridine/formic acid/water, 70:9.6:0.4:20, v/v, or tertpentanol/methylethylketone/pyridine/water, 37.5:37.5:5:20, v/v) on amorphous cellulose thin-layer are given. The efficiency of the procedures is evaluated in various examples.Abbreviations used: TLC = thin-layer chromatography, TLE = thin-layer electrophoresis, TLP = thin-layer plate; other abbreviations: see Table I and end of text.for structural analogues of amino acids and glucosamine, see Table I.     

TLC resolution of enantiomeric mixtures of amino acids

Summary Resolution of enantiomeric mixtures of DL-amino acids (Nine) using silica gel layers impregnated with (-)-bruncine is reported. The solvent system used was Butanol: Acetic acid: Chloroform (3∶1∶4). The diastereomers were formed and hydrolysed, by dilute HCl spray, on the chromatogram only and the amino acids thus resolved were located by ninhydrin spray. The cross resolution possibilities of enantiomers were also calculated.     

Cellulose conformation responsible for resolution of DL-amino acids

Summary For the purpose of biochemical study, the resolution of non-derivatized DL-amino acids was carried out by using native-cellulose thin-layer and column chromatography. Its resolution capability was known to be in proportion to the increase of environmental hydrophobicity. It is suggested that the resolutions of DL-amino acids might be resulted from the cellulose conformation change under hydrophobic conditions. The model structures of cellulose are proposed in order to understand the mechanism of chiral selection of amino acids on its molecular surface. LEB/OU contribution No. 70     

HRGC of wine free amino acids as a tool for elementary wine characterization

In this paper we show that wine free amino acids derivatized as isopropyl N-heptafluorobutyryl esters can be used as a tool for wine characterization. Elementary wines of eight Vitis vinifera varieties were studied during a seven year period. The characteristic wine amino acids for each variety were assessed by means of pattern recognition techniques. A “star symbol plot” was used for graphic representation.     

Poly(ethylene glycol) as Impregnator for Silica Gel in Salting-Out Thin-Layer Chromatography of Some Co(III) Complexes

Silica gel impregnated with poly(ethylene glycol) of different molecular mass (400, 1000, 1540, 4000, and 5500) was investigated for salting-out thin-layer chromatography of 15 mixed aminocarboxylato Co(III) complexes using eight ammonium sulphate solutions as mobile phases. Regularities established earlier for non-impregnated adsorbents are also valid in this work. Poly(ethylene glycol) of high molecular mass increases the hydrophobicity of the adsorbent. Positive linear dependence of R_M values and of salting-out efficiency on average poly(ethylene glycol) molecular mass was usually observed. In contrast with non-impregnated silica gel, separation was achieved between complexes with the smallest hydrocarbon groups.     

A rapid and reliable direct method for quantifying meat acylglycerides with monomode microwave irradiation

A rapid methodology for direct analysis of meat acylglycerides is proposed. A transesterification is carried out in a microwave reactor consisting of a monomode oven using chlorotrimethylsilane (CTMS) and methanol. High-temperature gas chromatography was used to check the absence of underivatized acylglycerides. Whereas transesterification is complete after 30 s at 90 °C in the microwave method, the reference method needs 2 h to complete this process. Moreover, the CTMS–microwave method shows higher recoveries of individual saturated, monounsaturated and polyunsaturated fatty acids. No influence of microwave irradiation on the composition of the fatty acids was observed.     

酸掺杂聚二茂铁-茴香醛的合成与表征

二茂铁聚合物是一类极具发展和应用前途的金属有机聚合物,它经过缩聚、共聚和改性后可得到具有特殊的电、磁等性能的功能高分子材料。聚二茂铁-茴香醛是一种重要的二茂铁缩聚物,其结构如图1所示：     

Influence of column temperature,water content,polarity, and acidity of isohydric solvents on the separation of butyrophenones on silica gel

Summary The behaviour of butyrophenones in high performance liquid chromatography on silica gel using isohydric solvent systems has been studied. The influence of column temperature, water content, acidity and polarity of isohydric solvents on the retention, column efficiency and resolution of a series of butyrophenones have been investigated. Through the results obtained more insight has been gained into the theoretical aspects of the adsorption process on silica gel with isohydric solvent systems.     

Determination of urinary organic acids by HPLC

Summary A high-performance liquid chromatographic method for the simultaneous determination of urinary organic acids and creatinine for following the metabolism of aromatic solvents is reported. After extraction of acidified, filtered urine with diethylether followed by evaporation, the dried residue is dissolved in mobile phase. Hydroxybenzoic acid is used as internal standard. A column of Nucleosil C₁₈ is used with a precolumn of the same material. The mobile phase is acetonitrilephosphate buffer, pH 3.3 (1783). For determination of creatinine the sample is simply diluted 10-fold and the eluate monitored at 215 nm (UV). This technique gives highly reproducible results and is simple, reliable and useful for biological monitoring.     

Influence of various salts on the reversed-phase retention of some dansylated amino acids in TLC

Summary The retention of 14 dansylated amino acid derivatives was determined using aqueous LiCl, NaCl, KCl, RbCl and CsCl solutions as eluents in reversed-phase thinlayer chromatography. The salts exerted typical salting-out effects, the retention of each dansylated amino acid increased with increasing concentration of salt in the eluent. This effect has been tentatively explained by the suppression of the dissociation of the polar groups in the solute molecules resulting in increased apparent lipophilicity. The correlation between the increased retention of dansyl amino acids and the salt concentration was found to be linear. The hydrated radii and energy of hydration of cations as well as the hydrophobicity of free amino acids and the pK value of the -amino groups simultaneously influenced the retention.     

Quantitative HPTLC analysis of carboxylic acids in wine and juice

The need for quick and specific assay of carboxylic acids in wine and non-fermented beverages is explained. The method developed in this work is based on high performance thin-layer chromatography (HPTLC) followed by densitometric evaluation. Untreated samples, with the exception of red wines which were destained, were directly sprayed onto the cellulose layer. The chromatogram was developed with ethyl acetate-toluene-water-formic acid 60:20:20:15, then stained with xylose-aniline reagent. Densitometric scanning is by absorbance at 546 nm. The method is quick, sensitive, and has a wide dynamic range for the acids analyzed.     

Retention parameters of some isomeric 2-benzoylbenzoic acids in reversed-phase ion-pair high performance thin-layer and column chromatography

Summary The 2-benzoylbenzoic acid series was investigated by reversed-phase, high-performance, thin-layer and column chromatography using various alkylammonium salts and di(2-ethylhexyl)orthophosphoric acid as polar associating reagents. The effects of the individual substituents on retention were quantified by log k and R_M values. The compounds investigated differing in molecular structure (hydrophilic and hydrophobic substituents) commonly occurring groups in drugs and biologically active substances provide information on molecular interaction in these ion-pair systems. The combined effects on retention of organic modifier and ion-pair reagent concentration were investigated.     

Separation studies of amino acids,proteins and enzymes on bonded 1,2-dihydroxy-, 1,2-hydroxylamino-and amino silica packings

Summary 1,2-dihydroxy-3-propoxypropyl (HPPS), 1-amino-2-hydroxy-3-propoxypropyl (AHPS) and 1-aminoethyl-3-aminopropyl (AEAPS) silica were synthesized by means of both a surface modification procedure (I) and a bulk modification procedure (II). Method (I) gave a surface concentration, , of functional groups of 2–3 mole/m², whereas method (II) gave values up to 5 mole/m². Retention times, peak asymmetries and plate heights of thiamine and ascorbic acid eluted with aqueous buffer solutions ranging from pH 5.3 to 9.2 gave only a±5% variation over periods of 12 hours and more.The recoveries of selected enzymes and proteines examined under static and dynamic conditions were between 60% and 100% depending on the functional group of the packing and on the solute. With HPPS silica, which showed the least adsorption and denaturing effects, separation of biopolymers depended on a size exclusion effect in the relative molecular mass range 10,000 to 80,000 and could be achieved within 10 min.A part of the paper was presented at the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Febr. 28 to March 4, 1977, Cleveland, Ohio, U.S.A.     

Separation and identification of lichen acids of the pulvinic acid series

Lichen acids, pulvinic acid, vulpinic acid, pinastric acid, leprapinic acid, lsoplnastric acid and pulvinic acid dilactone, which occur in certain yellow varieties of lichens and are difficult to separate, have been successfully separated and identified by TLC on chlorobenzene-impregnated silica gel plates.     

Separation of DABS derivatives of amino acids by multiple gradient development (MGD) in thin-layer chromatography

Summary A mixture of 13 DABS-amino acids has been chromatographed on high-performance silica gel layers developed with eluents containing increasing concentrations of ethyl acetate in heptane + chloroform, using a modification of stepwise multiple development MGD described in a earlier paper. Densitograms were obtained at 485 nm. The MGD method was very efficient, separating all 13 DABS-amino acids, and rapid, owing to the use of a non-aqueous mobile phase.