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  • 1
    ISSN: 1438-2385
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Zusammenfassung Die gelchromatographisch abgetrennten und isolierten niedermolekularen Purin- und Pyrimidinverbindungen wurden nach hydrolytischem Druckaufschluß an einem Kationenaustauscher als freie Basen bestimmt. Diese Daten werden auch im Verhältnis zu den Gesamtgehalten der Basen des Substrates mitgeteilt. Es zeigte sich, daß bei unbehandelten Proben der Anteil der niedermolekular gebundenen Basen 5–15% (je nach Base und Lebensmittel) der jeweiligen Gesamtbasenmenge beträgt. Bei frischen, nicht erhitzten Lebensmittelproben findet ein schneller Abbau von Adeninnucleotiden zu Inosinnucleotiden und zu Hypoxanthin statt, so daß nur geringe Adeningehalte aus niedermolekularen Verbindungen angetroffen werden. Bei erhitzten Lebensmitteln ist der Anteil niedermolekular gebundener Purin- und Pyrimidinbasen durch Teilhydrolyse von Nucleinsüren höher. Er beträgt dann 30–50% (je nach Base und Lebensmittel) der jeweiligen Gesamtbasenmenge.
    Notes: Summary Compounds with purine and pyrimidine bases of low-molecular weight were separated and isolated by gelpermeation-chromatography. After acid hydrolysis of nucleotides to free bases in a pressure digestion vessel the bases were separated on cation exchange resins. The data obtained are also reported in relation to the total base content of the substrate. It could be demonstrated that in untreated samples the portion of combined bases of low-molecular weight results in 5 to 15% of the corresponding total base content, depending on base and kind of food. In fresh unheated food samples adenine nucleotides are con verted rapidly to inosine nucleotides and hypoxanthine; therefore only a small share of adenine is found from compounds of low-molecular weight. In heated food the portion of combined low-molecular weight purine and pyrimidine bases proves to be much higher, due to partial hydrolysis of nucleic acids. It amounts to 30 to 50% of the total base content, depending on base and kind of food.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1438-2385
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Zusammenfassung Eine Methode zur Auftrennung und quantitativen Bestimmung der in Lebensmitteln aus Nucleinsäuren, Nucleosiden oder Nucleosiden freigesetzten und freien Purin- und Pyrimidinbasen wurde ausgearbeitet. Nach saurer Hydrolyse der Nucleotidpolymeren bis zu den freien Basen bei gleichzeitiger ausreichender Proteinspaltung in einem Druckaufschlußgefäß wurden die Basen durch stufenweise Elution an zwei verschiedenen Kationenaustauscherharzen getrennt. Die Identifizierung und quantitative Bestimmung erfolgte mittels kontinuierlich registrierender UV-Messung bei λ = 260 nm. Die Auswertung wurde nach dem Verfahren des Internen Standards mit Hilfe einer in der Natur nicht vorkommenden Purinbase durch elektronische Integration vorgenommen. Zusätzliche Identifizierungen der eluierten Basen konnten durch Fraktionssammlung und damit Reinstisolierung der Peaks mittels UV-Spektralphotometrie oder anderer chromatographischer Methoden (DC, GC) durchgeführt werden, da aufgrund des hohen Elutionsflusses und der hochkapazitiven Trennsäule erhebliche Substanzmengen (bis zu 200 μg je Einzelkomponente) getrennt werden konnten.
    Notes: Summary A method was developed for the separation and quantitative determination of purine and pyrimidine bases liberated from food nucleic acids, nucleotides and nucleosides. After acid hydrolysis of nucleotide polymers to the free bases and simultaneous splitting of the proteins in a pressure digestion vessel, the bases were separated by gradient elution on two different cation exchange resins. The Internal Standard Method was used for identification and quantitative determination, by adding a non-natural purine base, continuously monitoring the UV-measurement at λ = 260 nm and integrating it electronically. Furthermore the eluted bases were fractionally collected, which meant purest isolation of the peaks, and identified by UV-spectrophotometry and/or other chromatographic methods (TLC, GLC). In this way, because of the high elution flow and the high capacity of the separation column, considerable amounts, up to 200 μg of each compound could be separated and isolated.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European food research and technology 184 (1987), S. 8-10 
    ISSN: 1438-2385
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Zusammenfassung Die chemischen Grundlagen der Nucleinsauren-und Nucleotidhydrolyse zur Ermittlung der in Lebensmitteln enthaltenen, gebundenen Purin- und Pyrimidinbasen wurden untersucht. Es konnte gezeigt werden, daß das Säurengemisch Trifluoressigsaure/Ameisensaure durch die Bildung von Kohlenmonoxid (CO) bei der Hydrolyse einen Schutz der Purinbasen vor oxydativem Abbau bewirkt. Weiterhin wurde ein zeitsparendes Rechnerprogramm entwickelt und vorgestellt, das die Berechnung der in Lebensmitteln enthaltenen Nucleinsauren, Nucleotide und der Purinstickstoffgehalte aus den einzelnen Basen erlaubt.
    Notes: Summary In order to determine the amount of combined purine and pyrimidine bases in foods we investigated the chemical fundamentals of their hydrolytic digestion it was demonstrated that the digestion mixture used, containing trifluoracetic- and formic acids, protected the purine bases during hydrolysis from oxidative degradation due to carbon monoxide formation. Further, a time-saving computer-program was developed and presented. This program allows, depending on the purine composition, the calculation of the corresponding nucleic acids, the nucleotides and the purine-nitrogen-content of the food.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European food research and technology 185 (1987), S. 119-122 
    ISSN: 1438-2385
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Zusammenfassung Proteinreiche Lebensmittel wurden mit Hilfe der bereits früher mitgeteilten Analysen-methode auf ihren Gehalt an Nucleostoffen untersucht. Die Gehalte bestimmter Nucleobasen (Purine und Pyrimidine) und die daraus errechneten Anteile zugehöriger Nucleinsäuren (RNA, DNA) sowie die dem Hypoxanthin äquivalente Menge an IMP werden in drei Tabellen mitgeteilt. Auf die bei der Verarbeitung von Lebensmitteln durch thermische Behandlung auftretenden Veränderungen an den Nucleostoffen wird durch experimentelle Daten besonders hingewiesen. Die Untersuchungen an einigen Meerestieren zeigen die hohen Anteile an Hypoxanthin und Guanin, während der Anteil der Nucleinsäuren gering ist.
    Notes: Summary The content of nucleo-compounds was investigated in protein rich food by the analytical methods as reported in previous publications. The data obtained for nucleobases (purines and pyrimidines) as well as the contents of nucleic acids (RNA, DNA) calculated therefrom and the content of IMP corresponding to the determined content of hypoxanthine are reported in three tables. The experimental data show remarkable alterations that have occurred on the nucleo-compounds in heat-treated food. The investigation of some sea-fishes pointed out the high content of hypoxanthine and guanine, and a low content of nucleic acids.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 827-833 
    ISSN: 0935-6304
    Keywords: GC ; Lubricating Oil ; Polycyclic aromatic hydrocarbons (PAH) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Liquid - liquid extraction with N-methyl-2-pyrrolidone, combined with solid-phase extraction on silica gel using n-pentane and dichloromethane as solvents, has been used for the isolation and concentration of the aromatic fraction from lubricating oil.The identification of individual compounds in this aromatic fraction was performed by capillary gas chromatography-mass spectrometry (CGC-MS) and by determination of retention indices. Quantitative results were obtained by flame ionization detection (CGC-FID). Eighty four compounds, predominantly naphthalenes, phenanthrenes, biphenyls, fluorenes, dibenzo-thiophenes, and their alkylated derivatives, have been identified in a commercial lubricating oil. The total amount of the aromatic fraction did not exceed 0.04 % of the oil.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 682-685 
    ISSN: 0935-6304
    Keywords: HPLC ; Polycyclic aromatic sulfur heterocycles (PASH) ; Sulfone method ; Diesel fuel ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An oxidation method (sulfone method) for the determination of polycyclic aromatic sulfur heterocycles (PASH) in diesel fuel is presented. The aromatic fraction of a diesel fuel, isolated by solid phase extraction, is oxidized under controlled conditions with hydrogen peroxide. The oxidation products, mainly methylated dibenzosulfone, are determined and quantified directly, without further clean-up, by HPLC with photodiode-array detection.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Solid phase extraction ; Structure-type separation ; Polycyclic aromatic hydrocarbons (PAHs) ; Diesel fuel ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple and effective solid phase extraction (SPE) method using silica gel micro glass columns has been developed for the separation of diesel fuel into groups of aliphatic, and mono-, di- and polyaromatic hydrocarbons. It is based on a stepwise gradient of dichloromethane in n-pentane. The resulting fractions were analyzed by capillary gas chromatography with a flame ionization detector and coupled gas chromatography-mass spectrometry.Commercially available standards, and retention indices and mass spectra were used for identification of individual aromatic compounds. The principal polycyclic aromatic hydrocarbons (PAHs) in diesel fuel are naphthalene, biphenyl, fluorene, phen-anthrene and their alkylated derivatives. Sulfur-containing PAHs are mainly represented by methyl-substituted dibenzo-thiophenes.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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