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  • 1
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary A simple titrimetric ultramicro method allows the determination of carbon in not easily volatile organic compounds using sample weights of 10–30 μg. Comparable quantities of S, P, N, Cl, Br, I do not interfere. The standard deviation of the method is ± 0,08 μg C. Sulphur-free substances are burnt at 1000°C in pure oxygen, sulphur containing substances at 550°C in presence of an Ag-Mn-PbCrO4 catalyst. The combustion is carried out with an electrically heated Pt-spiral in a slow stream of oxygen. The carbon dioxide is absorbed in 0.01 M Ba(OH)2 solution. Complete absorbance is attained by using a special stirrer. The excess of Ba2+ ions is photometrically back-titrated with a 0.01 M EDTA solution and phthalein purple as indicator.
    Notes: Zusammenfassung Eine einfache titrimetrische Ultramikromethode gestattet die Bestimmung des Kohlenstoffs schwerflüchtiger organischer Substanzen (10–30 μg) nach Lösungsteilung. Schwefel, Phosphor, Stickstoff, Chlor, Brom und Jod stören nicht, wenn sie in der gleichen Größenordnung wie der Kohlenstoff vorliegen. Die Standardabweichung der Methode beträgt ±0,08 μg Kohlenstoff. Schwefelhaltige Substanzen werden bei 550°C mit einem Ag-Mn-Bleichromatkatalysator, alle anderen Verbindungsklassen in einem reinen Sauerstoffstrom bei über 1000°C verbrannt. Gezündet wird mit einer elektrisch heizbaren Platinspirale. Zur Bestimmung wird das Kohlendioxid in 0,01 m Bariumhydroxidlösung unter Zuhilfenahme eines hochtourigen Glockenrührers absorbiert und der Überschuß der Bariumionen in 60% dioxanhaltiger Lösung gegen Phthaleinpurpur komplexometrisch zurücktitriert. Die Endpunktsanzeige wurde photometrisch vorgenommen.
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  • 4
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary For the determination of chlorine in ultramicro amounts of nonvolatile organic compounds 1–10μg of the substance are measured by taking an aliquot of a solution of known strength. This aliquot is filled into a small quartz tube, the solvent is evaporated by blowing with a stream of filtered air, and the remaining substance is burnt in a stream of oxygen at 1000–1100° C. The HCl formed is absorbed in glacial acetic acid and titrated by help of differential electrolytic potentiometry. The relative standard deviation is ±1,5%. Quantities of N, P, S and F comparable to the amount of chlorine do not interfere. For the determination of chlorine in substances containing bromine and iodine silver electrodes are to be used.
    Notes: Zusammenfassung Zur Ultramikrobestimmung schwerfüchtiger organischer Stoffe werden 1–10 μg Substanz durch Lösungsteilung abgemessen und nach Entfernung des Lösungsmittels im Sauerstoffstrom bei 1000–1100°C verbrannt. Der gebildete Chlorwasserstoff wird in einer Vorlage in Eisessig absorbiert und argentometrisch titriert. Die Endpunktsanzeige erfolgt durch differentielle elektrolytische Potentiometrie mit AgCl-Elektroden. Die relative Standardabweichung beträgt 1,5%. Stickstoff-, P-, S- und F-Mengen in der Größenordnung des Chlorgehaltes verursachen keine Störungen. Bei brom- bzw. jodhaltigen Verbindungen müssen reine Silberelektroden verwendet werden.
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  • 5
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Zur Herabsetzung der Nachweisgrenze von Organohalogeniden in der Dünnschichtchromatographie durch Fluorescenznachweise wurden 24 fluorescierende Verbindungen verschiedener Stoffklassen untersucht. Durch Sprühreagentien mit N,N,N′,N′-Tetraäthyl-benzidin, N,N-Dimethylamino-fluoranthen, N-Methyl-carbazol, 3-Amino-pyren, Rhodamin B oder Resorufin in z.B. Aceton/dest. Wasser werden nach Bestrahlen der Dünnschichtplatte (1–15 min) mit UV-Licht (254 oder 350 nm) Substanzmengen bis zu 20 ng von polychlorierten Insecticiden (z.B. Aldrin®, Telodrin®, Thiodan®) nach dünnschichtchromatographischer Trennung aufSilicagelGMerck oder Aluminiumoxid G Merck nachgewiesen. Die Empfindlichkeit der Nachweise läßt sich in erster Linie auf geringe Fluorescenzindicatorkonzentrationen (10−2-10−3%) und auf den Zusatz eines geeigneten hochsiedenden Lösungsmittels (z.B. Dimethylformamid) zum Sprühreagens zurückführen.
    Notes: Summary In order to reduce the limit of detection of organohalides following thinlayer chromatography 24 fluorescent substances of various types were studied. The lowest amount of polychlorinated insecticides (e.g. Aldrin, Telodrin, Endosulfan) to be detected on silicagel G Merck or Al2O3 G Merck was 20 ng. The spots were made visible by spraying the thin-layer with fluorescent reagents containing 4.4′-bis-diethylamino-diphenyl, 3-dimethylamino-fluoranthene, 9-methyl-carbazole, 3-amino-pyrene, rhodamine B, or resorufin in e.g. acetone/dest. water. After irradiating the plates with ultraviolet light at 2536 or 3500 Å for 1–15 min the spots showed fluorescence or quenching. The sensitivety of detection is caused primarily by the low concentration of the fluorescent indicator (10−2-10−3%) and by adding suitable solvents of high boiling point (e.g. dimethyl formamide) to the spray solution.
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  • 6
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Zur Ultramikrobestimmung von Brom in schwerflüchtigen organischen Verbindungen werden 1–5 μg Substanz (mit dieser Methode sind auch größere Substanzmengen analysierbar) durch Lösungsteilung abgemessen und nach Absaugen des Lösungsmittels im Wasserstoffstrom bei einer konstanten Temperatur von etwa 900°C pyrolysiert, wobei sich Brom quantitativ zu Bromwasserstoff umsetzt, der in einer Vorlage in Eisessig absorbiert und argentometrisch titriert wird. Die Endpunktsanzeige erfolgt bipotentiometrisch. Bei Abwesenheit von anderen Halogeniden und Sulfid werden Silberbromid-Elektroden benutzt, andernfalls SilberElektroden. Die relative Standardabweichung der Methode beträgt im ersten Fall ±1.4% und erhöht sich auf etwa ±3%, wenn gleichzeitig Chlor, Jod oder Schwefel vorliegen.
    Notes: Summary For the determination of bromine in ultramicro amounts of non-volatile organic compounds 1–5 μg of the substance (this method can be used for larger amounts as well) are measured by taking an aliquot of a solution of known concentration. After evaporation of the solvent the sample is pyrolyzed in a hydrogen stream at a constant temperature of about 900°C. Hydrogen bromide obtained in a quantitative reaction, is absorbed in glacial acetic acid and titrated argentometrically. The endpoint of the titration is found by a bipotentiometric method. In the absence of other halogenides or sulphide silver bromide electrodes are used, otherwise silver electrodes. The relative standard deviation is ±1.4% in the first case and about ±3% in the latter.
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  • 7
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 9
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Various possibilities for the determination of trace impurities in high-purity iron by atomic spectrometry were investigated in detail. For Ba, Bi, Cd, Co, Cr, Cu, Mn, Ni, Pb, Ti and V, flame AAS, furnace AAS and ICP-OES were firstly evaluated in terms of their power of detection. Detection limits in the μg/g-range could be achieved by direct determination. For determination in the ng/g-range a removal of iron by a solvent extraction technique prior to the instrumental measurement was required. The power of detection of direct determination, and of combined procedures were compared with regard to routine applicability and a minimization of systematic errors.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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