Chromatographic separation and colorimetric determination of gold

Gold(III) is selectively sorbed from 1M hydrochloric acid by a short column containing a special acrylate resin. Then the gold is eluted from the column with acetone-hydrochloric acid, and the absorbance of the effluent is measured at 340 nm. Gold(III) may be successfully separated and determined in samples containing many other metal ions.     

Chromatographic determination of the mycotoxin patulin in fruit and fruit juices

Patulin is a mycotoxin produced by several fungal species of the genera Penicillium and Aspergillus, but principally by Penicillium expansum on fruit such as apples. The occurrence of patulin as a natural contaminant of apple juice is a worldwide problem and international recommendations and regulations have been made for maximum levels permitted in consumer products. This paper reviews currently available analytical methods for its determination in fruit and fruit juices. Of these, HPLC with ultraviolet or, preferably, photodiode array detection is most widely used, although GC and TLC methods have also been described.     

Chromatographic determination of amino acids in foods

Amino acids in foods exist in a free form or bound in peptides, proteins, or nonpeptide bonded polymers. Naturally occurring L-amino acids are required for protein synthesis and are precursors for essential molecules, such as co-enzymes and nucleic acids. Nonprotein amino acids may also occur in animal tissues as metabolic intermediates or have other important functions. The development of bacterially derived food proteins, genetically modified foods, and new methods of food processing; the production of amino acids for food fortification; and the introduction of new plant food sources have meant that protein amino acids and amino acid enantiomers in foods can have both nutritional and safety implications for humans. There is, therefore, a need for the rapid and accurate determination of amino acids in foods. Determination of the total amino acid content of foods requires protein hydrolysis by various means that must take into account variations in stability of individual amino acids and resistance of different peptide bonds to the hydrolysis procedures. Modern methods for separation and quantitation of free amino acids either before or after protein hydrolysis include ion exchange chromatography, high performance liquid chromatography (LC), gas chromatography, and capillary electrophoresis. Chemical derivatization of amino acids may be required to change them into forms amenable to separation by the various chromatographic methods or to create derivatives with properties, such as fluorescence, that improve their detection. Official methods for hydrolysis and analysis of amino acids in foods for nutritional purposes have been established. LC is currently the most widely used analytical technique, although there is a need for collaborative testing of methods available. Newer developments in chromatographic methodology and detector technology have reduced sample and reagent requirements and improved identification, resolution, and sensitivity of amino acid analyses of food samples.     

Chromatographic separation and determination of noble metals in matte-leach residues

The practical application of various chromatographic methods to the analysis of residues obtained from the leaching of copper-nickel mattes is described. The procedure involves the separation of gold on a TBP-treated Porasil column, the separation of base metals by cation-exchange, the separation of tellurium from platinum-group metals, and the separation of the non-volatile platinum-group metals on one cellulose column.     

Chromatographic separation and determination of Zr in bauxites and aluminum alloys

Summary A simple thin-layer chromatographic method for the complete separation of Zr from aluminum is described. The optimum solvent composition is evaluated by means of the simplex method of optimization. Quantitative determination and regression analysis is carried out.     

Chromatographic determination of D-amino acids as native constituents of vegetables and fruits

Summary Free D-amino acids (D-AA) were detected as native constituents in juices of vegetables (cultivars of cabbage, tomato, carrot, garlic) and fruits (organes, clementine, grapefruit, lemon, apples, pear, grapes) using gas chromatography (GC) or high-performance liquid chromatography (LC). For investigation by GC, AA enantiomers were converted into theirN(O)-pentafluoropropionyl 2-propyl esters and resolved on a Chirasil-L-Val capillary column. For determination by LC, precolumn derivatization of AA enantiomers usingo-phthaldialdehyde together with the chiral thiolsN-isobutyryl-L-cysteine orN-isobutyryl-D-cysteine and fluorescence detection of the diastereomeric isoindole derivatives, resolvable on an octadecylsilyl stationary phase, were used. D-Ala (0.6–3.8%) was detected in all freshly pressed plant juices usually in the highest relative amounts. Other D-AA detected were D-Asx (0.1–1.9%), D-Glx (0–1.3%), D-Ser (0–1.7%), D-Arg (0.4–1.2%, in grapes, orange, grapefruit, and clementine) and D-Leu and D-Val (1% in cabbage). Absolute amounts of native D-AA were totally 28–57 mol L^–1 in fruit juices, 14.5 mol L^–1 in a tomato juice and 8.5 mol L^–1 in a carrot juice.Presented in part as lecture at 3rd International Congress on Amino Acids, Peptides and Analogues, August 23–27, 1993, Vienna; and as posters at 31st Scientific Meeting of German Society of Nutrition, Giessen, March 17th and 18th, 1994 [19]; and at Analytica Conference, April 19–22, 1994, Munich [20].     

Chromatographic separation of uranium

Summary A solvent mixture of methanol and saturated ammonium acetate solution (18:2) is employed for the separation of uranium in ppm quantities from iron (up to 1000 fold excess) by paper chromatography. The separation from both iron and copper can be achieved by using a solvent mixture of methyl ethyl ketone, acetic acid, and diluted nitric acid (1613).

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Zusammenfassung Zur papierchromatographischen Trennung von ppm-Mengen Uran von Eisen (in bis zu 1000 fächem Überschuß) wird ein Laufmittel aus Methanol und gesätt. Ammoniumacetatläsung (182) benutzt. Die Trennung von Eisen und Kupfer wird mit einem Gemisch aus Methyläthylketon, Essigsäure und verd. Salpetersäure (1613) durchgeführt.

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The author is highly thankful to Prof. Bh. S.V. Raghava Rao for his valuable suggestions and guidance throughout the progress of this work.Thanks are also due to the Department of Geology, Andhra University for supplying the samples and to the Counsil of Scientific and Industrial Research, New Delhi for the award of a fellowship.     

Chromatographic separation of isoflavones

The optimum ratios of the components of the solvent systems have been determined with the aid of the simplex-grid method of experimental planning and the separation of a number of isoflavones has been carried out with the aid of these systems in thin layers of silica gel (Silufol plates); in addition, the chromatographic constants of the functional groups have been determined, which makes it possible to obtain the R_f values of compounds under investigation in an analysis of plant material by a mathematical method.Pyatigorsk Pharmaceutical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 712–716, November–December, 1983.     

Simultaneous determination of N-unsubstituted and N-substituted nitroazoles and criteria for their identification-III Chromatographic separation and polarographic determination of halo-nitroimidazoles

Methods for identifying and determining halo-nitroimidazoles appearing together during synthetic processes, regardless of the preparation methods, are proposed. Polarographic determination can be used in all synthetic processes when halo-nitroimidazoles have been obtained by nitration of the halo-imidazoles. When the halo-nitroimidazoles have been obtained from 5(4)-halo-4(5)-nitroimidazoles by substitution of the imino hydrogen atom, and when only one N-substituted derivative has been obtained in a reaction mixture, simultaneous polarographic determination of both compounds is possible, but only when an alkaline medium is used as supporting electrolyte. In some cases, simultaneous polarographic determination of all three compounds present in a reaction mixture during N-substitution processes [one 5(4)-halo-4(5)-nitroimidazole and two N-substituted isomers] is also possible with alkaline supporting electrolyte. Explanations are given of the phenomena on which the simultaneous polarographic determination is based. When simultaneous polarographic determination cannot be used to determine the amount of each polarographically-active compound present in a reaction mixture, the compounds can be separated chromatographically and then determined individually by polarography.     

Simultaneous determination of N-unsubstituted and N-substituted nitroazoles and criteria for their identification-II Chromatographic separation and polarographic determination of nitropyrazoles

The N-unsubstituted nitropyrazoles have an imino hydrogen atom, in contrast to the N-substituted derivatives, and react with hydroxide to give nitropyrazole anions. The strongly negative shift of E(1 2 ) for these anions makes possible simultaneous polarographic determination of any pair of compounds, one of which is an N-unsubstituted nitropyrazole and the other a corresponding N-substituted derivative. Simultaneous polarographic determination of three compounds [3(5)-, 3- and 5-nitropyrazoles] is also possible with 0.1M sodium hydroxide as supporting electrolyte, but only when DeltaE(1 2 ) between the N-substituted isomers is at least 100 mV. In this case adequate DeltaE(1 2 ) is caused by the different electron densities of the nitro-groups of isomers. In the medium mentioned it is possible to determine simultaneously even four compounds [1-, 3(5)-, 3- and 5-nitropyrazoles], because the E(1 2 ) value of 1-nitropyrazole does not change with pH, contrary to other nitropyrazoles. Developers for the chromatographic separation are proposed. Some criteria are given for the distinction of the N-unsubstituted- and the corresponding N-substituted nitropyrazoles. The structures of two new compounds have been determined. Methods are recommended for the simultaneous identification and determination of the compounds appearing together in the reaction mixtures during the substitution of the imino hydrogen atom, or during the rearrangements of the 1-nitropyrazoles to the N-unsubstituted ones.     

Chromatographic separation of tocopherols.

alpha-, beta-, gamma-, and delta-Tocopherols were separated by reversed-phase high-performance thin-layer chromatography (C18RP-HPTLC), normal-phase high-performance liquid chromatography (NP-HPLC), reversed-phase high-performance liquid chromatography (C18RP-HPLC), and gas chromatography (GC). The selected topological indices based on connectivity (M, 1chi(v)), on distance matrix (W, (o)B, MTI) and on information theory (I(AC), I(AC)) were calculated for these tocopherols. The observed chromatographic separations of investigated tocopherols were compared. This comparison indicated that the C18RP-HPTLC, NP-HPLC, and GC are the best techniques for the separation of these tocopherols. Topological index (o)B was the most significant. We obtained definite dependence between the numerical values of topological index (o)B and the chromatographic separation of the investigated tocopherols.     

Chromatographic methods in the determination of absolute and relative configurations of fatty acids.

Chromatographic techniques for determination of configurations of branched and substituted long-chain fatty acids, both absolute and relative, are reviewed. Gas-liquid chromatographic and thin-layer chromatographic procedures are emphasized.     

The separation and determination of glycolic and malic acids by ion-exchange chromatography

An ion-exchange chromatographic method for the separation of glycolic and malic acids was developed. It was found that the resin structure plays an important role in the resolution of the two acids. The best system for separating the acids was a 2.8-mm i.d., 122-cm long Amberlite CG-400 anion-exchange column. The acids in concentrations of 1–10% in 2 M formic acid gave linear peak area responses.     

Chromatographic determination of lactulose

Summary Lactulose is a disaccharide with important implications in medicine, nutrition and dairy technology. It has to be determined usually as a minor component in complex matrices containing many other sugars. This paper describes the different chromatographic techniques (planar, liquid and gas chromatography) which have been proposed for the separation and quantification of lactulose in mixtures with other carbohydrates; the advantages of each technique are compared and some features where more research is necessary are outlined.