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  • Chemistry  (98)
  • Industrial Chemistry  (21)
  • Column liquid chromatography  (4)
  • 42.75
  • Atomic and molecular processes in external fields, including interactions with strong fields and short pulses
  • 1995-1999  (103)
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Keywords
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Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 337 (1995), S. 245-249 
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Spectroscopic Investigations on the Acidity of O,O′-Dithiophosphoric Acid Esters in Nonpolar Aprotic Solvents
    Additional Material: 3 Tab.
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  • 2
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    In:  Nederlandse Faunistische Mededelingen (01692453) vol.9 (1999) p.109
    Publication Date: 2007-01-10
    Description: The rearing of the botfly Cephenemyia auribarbis (Diptera: Oestridae) After several failures we finally succeeded in rearing botflies Cephenemyia from third-instar larvae. From a red deer shot at 13 March 1998 about one hundred larvae of Cephenemyia auribarbis (Meigen, 1824) were collected. Ten individuals reached the pupal stage. After 22 days, one fullgrown male died in the pupa, and two males emerged and lived for 17 and 18 days respectively. This is one of the few recorded succesful attempts to rear botflies.
    Keywords: Insecta ; Diptera ; Oestridae ; Cephenemyia auribarbis ; Nederland ; Verspreiding ; 42.75
    Repository Name: National Museum of Natural History, Netherlands
    Type: Article / Letter to the editor
    Format: application/pdf
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  • 3
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Two-dimensional separation ; D- and L-amino acids ; Enantioseperation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A two-dimensional, column liquid chromatographic system is used for the determination of the D- and L-enantiomers of amino acids in biological samples. Separation of the amino acids is first on ion-exchange column by gradient elution with a sodium citratesodium chloride buffer. Enantioseparation is by subsequent injection of 3 μl heart-cuts of the individual amino acids onto a second column with a chiral crown ether stationary phase. Finally, fluorescence detection is after post-column labelling of the amino acids using ano-phthalaldehyde-2-mercaptoethanol reagent solution. The high separation power and selectivity of the system allow processing of complex samples with hardly any additional treatment and the determination of small quantities of D-amino acids in the presence of excess L-form. Applicability of the system is illustrated by the determination of D- and L-aspartate, serine, glutamate and alanine in various complex biological samples, such as protein hydrolysates, urine and biotechnological and food samples. Data are given on detectability, repeatability and linearity.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Macrocyclic [4n + 2]-Hückel Aromatic Systems up to n = 9 and [4n] Antiaromatic Systems up to n = 10: Homologous Sequences from Tetraepoxy[24]annulene(2.0.2.0) to Tetraepoxy[40]annulene(12.0.12.0) and from the ‘Tetraoxa[22]porphyrin(2.0.2.0)-’ to the ‘Tetraoxa[38]porphyrin(12.0.12.0’-Dication1)2)Tetraepoxy[32]annulene(8.0.8.0) 3, tetraepoxy[36]annulene(10.0.10.0) 4, and tetraepoxy[40]annulene(12.0.12.0) 5 are synthesized and oxidized to give the ‘tetraoxa[30]-’, ‘tetraoxa[34]-’, and ‘tetraoxa[38]porphyrin’ dications 8-10. The annulenes as well as the ‘porphyrins’ are mixtures of at least two different configurational isomers, which can be analyzed by 1H-NMR techniques. Together with systems described already earlier, a complete homologous sequence from tetraepoxy[24]annulene(2.0.2.0) to tetraepoxy[40]annulene(12.1.12.0) and from ‘tetraoxa[22]porphyrin(2.0.2.0)’ to ‘tetraoxa[38]porphyrin(12.0.12.0)’ dications are available for the first time. The UV/VIS-absorptionmaxima in the annulene series are shifted to longer wavelengths with an increment of 12 nm per additional C=C bonds, and the Δδ values of the 1H-NMR spectra demonstrate a decreasing paratropic character (Δδ = 5.97 (1), 2.80 (3), and 4.23 ppm (4). The averaged λmax values of the Soret bands of the ‘tetraoxaporphyrin’ dications show a linear bathochromic shift with an increment Δδ of 58 nm per two additional double bonds, the absorptions of the most intensive Q-bands also increase linearly with an increment of ca. 160 nm. The Δδ values of the 1H-NMR spectra of the ‘tetraoxaporphyrin’ dications are increasing with the ring size (Δδ = 24.04 (7a) to 25.17 (9a) ppm), respectively, decreasing (Δδ = 21.55 (6) to 21.50 (9b) ppm) with a small maximum of 22.60 ppm for 7b, depending on the configuration of the isomers. The results confirm the antiaromatic character of the annulenes with up to 40π electrons and the aromatic character of the ‘tetraoxaporphyrin’ dications with up to 38π electrons.
    Additional Material: 18 Ill.
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  • 5
    ISSN: 0009-2940
    Keywords: Organotungsten selenolates ; 77Se NMR ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organotungsten-selenolato complexes were prepared in moderate yields by insertion of selenium into the alkali metaltungsten bonds of MSeW(CO)3cp (M = Li, Na) and subsequent reactions with the organohalides o-, m-, and p- C6H4(CH2Br)2, C6H5CHBr2, m-C6H4(CHBr2)2 and C6H5CCl3. The 77Se-NMR data of the new complexes are discussed and compared with those of related complexes derived from organomonohalides. Moreover, the X-ray crystal structures of C6H5CH2W(CO)3cp (1), μ-[m-C6H4{CH2SeW(CO)3cp}2] (3), μ-[p-C6H4{CH2SeW(CO)3cp}2] (4), and C6H5CH[SeW-(CO)3cp]2 (5) were determined. In complex (1), the W-CH2 bond length is 2.374 Å; the W-Se bond lengths in the complexes 3, 4 and 5 are all in the range 2.625-2.655 Å, corresponding to W-Se single bonds.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 81-87 
    ISSN: 0887-624X
    Keywords: 2-methylene-1,3-dioxolanes, benzoyl peroxide reaction of ; 2-methylene-1,3-oxazolidines, benzoyl peroxide reaction of ; polyacetals ; charge-transfer polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 2-methylene-1,3-dioxolanes and 2-methylene-1,3-oxazolidines with benzoyl peroxide (acceptor radical) and with N-ethylmaleimide (acceptor) was investigated. It was shown that benzoyl peroxide adds to monomers 1a and 1b, giving the corresponding linear diester amides 1a and 1b respectively. The oxazolidine 1c adds benzoyl peroxide, without ring opening, by addition to the exomethylene group. Together with N-ethylmaleimide the oxazolidines 1a or 1b produce deep-colored charge transfer complexes, resulting in high molecular poly-N-ethylmaleimides probably via a radical mechanism. The 1,3-dioxolanes 2a and 2b were radically polymerized to produce polyacetals by vinyl polymerization. 2c was polymerized to produce randomly containing acetal units and ester units. The mechanism of polymerization of 2e is complex, affording polymers of nonuniform character. 2-Methylene-4-phenyl-1,3-dioxolane polymerization leads to polyester as the main structure, and to a lesser degree polyacetal structures. The chemical structures of the polymers were confirmed by NMR spectra and elemental analysis. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 49-54 
    ISSN: 0887-624X
    Keywords: polymer membranes ; poly(vinyl pyrrolidone) ; hypochlorite ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sodium hypochlorite solutions are used to treat membranes prepared from a polymeric blend containing poly(vinyl pyrrolidone) (PVP) to increase their water permeability. Sodium hypochlorite affects the membrane material in such a way that PVP is selectively removed from the membrane matrix. The mechanism of the reaction between hypochlorite and PVP is investigated by several chemical analysis techniques of the reaction products. Strong indications are found that the reaction involves chain scission of PVP according to a radical mechanism. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 8
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Short-Column LC ; Environmental water samples ; MS-MS detection ; Pesticide degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The applicability of solid-phase extraction-LC using two short columns (SPE-LC) and/or single-short-column liquid chromatography (SSC) combined on-line with tandem mass spectrometry (MS) was demonstrated for the rapid study of pesticide degradation. A fast analytical procedure was developed to provide preliminary information concerning experimental conditions, approximate rates of degradation and identity of the degradation products. Surface water samples were spiked at relevant concentration levels with well-known microcontaminants and photolysis was used to transform parent compounds into their degradation products. In general, the strategy was as follows: at 30-min intervals 10-mL samples were on-line enriched, separated by short-column LC and recorded in full-scan MS to obtain information on the disappearance of the parent compound and the appearance of breakdown products. To obtain structural information, product-ion spectra of selected compounds appearing in the full-scan MS chromatogram were recorded; this enabled the identification of several degradation products. Total analysis time of enrichment/separation and detection was about 10–15 min.
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  • 9
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sugars ; Amperometric detection ; Chemically modified electrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A chemically modified electrode was applied as a working electrode for the amperometric detection of sugars in liquid chromatography. A mixture of cuprous oxide and conductive carbon cement was used as electrode material. Cuprous oxide acted as a catalyst for the oxidation of sugars. Cyclic voltammetry was used to examine the oxidation of the sugars at the electrode surface. The stability and sensitivity of a cuprous oxide/conductive carbon cement (20/80 %, w/w) electrode were tested in flow injection analysis experiments. For liquid chromatography, sugars were separated on an ion-exclusion column with 0.01 M H2SO4 as mobile phase. After the separation, 0.2 M NaOH was added post-column and the sugars were determined at 550 mV vs. Ag/AgCl. Calibration was linear in the range of 10−6·10−3 M with limits of detection of approximately 1·10−6M. The application of the modified electrode for the determination of sugars in fruit beverages and dairy products following chromatographic separation is shown.
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  • 10
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; On-line coupling ; Ion-exchange membrane ; Ion-pair reagent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In order to enable the coupling of reversed-phase liquid chromatography (RPLC) with capillary gas chromatography (GC), the performance of an anion-exchange micromembrane device has been studied to remove the ion-pair reagent methanesulphonic acid from an acetonitrile/water LC eluent. The regenerant in the membrane was tetrabutylammonium hydroxide dissolved in acetonitrile/water, which effects an anion-exchange of methanesulphonate ions for regenerant hydroxide ions. The efficiency of the exchange process was found to be 99.9%. This enabled the direct introduction of the LC eluent, free of ions and with the proper acetonitrile/water ratio, into the GC. The applicability of the on-line LC-micromembrane-GC system has been illustrated for the potential drug eltoprazine, which is quantitatively recovered with a coefficient of variation for standard solutions of 3% at the 150 μg/ml analyte level.
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