Bibliothek

X
feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • 1985-1989  (3.387)
  • 1980-1984  (2.383)
  • Engineering General  (3.850)
  • Physical Chemistry  (1.220)
  • Gas chromatography
  • Nuclear reactions
Datenquelle
Materialart
Erscheinungszeitraum
Jahr
Schlagwörter
  • 1
    Digitale Medien
    Digitale Medien
    An improved method for the determination in urine of alkoxyacetic acids (1989)
    Springer
    International archives of occupational and environmental health 61 (1989), S. 249-254 
    Details
    ISSN: 1432-1246
    Schlagwort(e): Ethylene glycol ethers ; Alkoxyacetic acids ; Pentafluorobenzylbromide ; Gas chromatography ; Urine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary A sensitive and specific method for the determination in urine of alkoxyacetic acids, the metabolites of ethylene glycol monoalkyl ethers, was developed by combining the advantages of two previously described methods. The acids were determined gas chromatographically as their pentafluorobenzylesters. The alkylation with pentafluorobenzylbromide was performed after dissolving the dry residue of lyophilized urine in methanol. Quantitative derivatization was obtained when the urinary pH was adjusted to pH 7.0, when the reagent concentration was 5% v/v, and when the reaction mixture was heated at 90°C for 3 h. Sample clean-up was performed by adding bidistilled water and the esters were extracted with methylene chloride with high yields (95%). Alkoxyacetic acid concentrations in the range of 0.1 to 200 mg/l could be determined with an average imprecision of ± 3.5%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00381422
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 2
    Digitale Medien
    Digitale Medien
    Analysis of ethylene glycol ether metabolites in urine by extractive alkylation and electron-capture gas chromatography (1989)
    Springer
    Archives of toxicology 63 (1989), S. 107-111 
    Details
    ISSN: 1432-0738
    Schlagwort(e): Analysis ; Biological monitoring ; Butoxyacetic acid ; Ethoxyacetic acid ; Gas chromatography ; Glycol ethers ; Metabolism ; Methoxyacetic acid ; Pentoxyacetic acid ; Urine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Alkoxyacetic acids are metabolically formed and excreted in urine after exposure to ethylene glycol monoalkyl ethers (alkoxyethanols) or their acetate esters. This paper presents a sensitive method based on extractive alkylation for determination of alkoxyacetic acids in urine. Alkoxyacetate ions were extracted from 200 μl urine into methylene chloride, with tetrabutylammonium acting as counter ion, and derivatized with pentafluorobenzyl bromide in a single step. After separation of the methylene chloride phase, evaporation, and dissolution of the residues in hexane the esters were analyzed by fused silica capillary column gas chromatography and electron capture detection. The esters formed were stable for at least 2 weeks at room temperature. The limit of quantification was estimated to 2 μM (corresponding to an injected amount of 2 pg) for methoxyacetic (MAA) and ethoxyacetic acid (EAA) in urine. The corresponding values for butoxyacetic acid (BAA) were 4 μM and 5 pg, respectively. The detector response was linear up to 80 μM and the formation of derivative at least up to 1 mM. The method error may be reduced by using a second alkoxyacetic acid derivative, EAA, BAA or 2-pentoxyacetic acid (PAA), as an internal standard. The sensitivity, stability, reduced number of extractions, and small volumes of reagents and sample needed make the present method useful in biomonitoring of occupational exposure to ethylene glycol ethers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00316431
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 3
    Digitale Medien
    Digitale Medien
    Sampling and analysis of airborne methylbromide (1989)
    Springer
    Chromatographia 27 (1989), S. 37-43 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Methylbromide ; Charcoal tubes ; Pollution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Air sampling of methylbromide using 900 mg HBr-treated activated charcoal tubes, followed by solvent desorption and FID or ECD chromatographic analysis, makes it possible to evaluate concentrations ranging from 0.2 ppm (1 mg×m−3) to 250 ppm (1g×m−3) at ambient temperature even with a high hygrometric level. Thermal desorption does not lead to satisfactory results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290402
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 4
    Digitale Medien
    Digitale Medien
    The mass loadability of various stationary phases in gas chromatography (1989)
    Springer
    Chromatographia 27 (1989), S. 60-66 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Mass loadability ; Stationary phase capacity ; Capillary columns
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary In GLC the mass load can be normalized with respect to the amount of stationary phase in one plate. This quantity can be used for a specified solute-liquid phase combination in any capillary or packed column, irrespective of the column dimensions or the number of plates. For each individual solute in a given stationary phase a unique factor β″ can be found, which accounts for the specific shape of the isotherm of this particular combination. this factor β″ corresponds well with the activity coefficients of the solutes in the stationary phase, by which a fairly good approximation of the mass loadability of the column at hand can be made without need for experiment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290407
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 5
    Digitale Medien
    Digitale Medien
    Relative rates of bromination and chlorination of 4-substituted cyclopentenes in methanol, ethanol and acetic acid (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 26-34 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A set of 4-monosubstituted cyclopentenes, , were synthesized and their relative rates (kX/kH) for bromination and chlorination were determined in methanol, ethanol and acetic acid at 25 °C by competitive method. log(kX/kH) for most of the substituents can be correlated by means of Taft's equation, log(kX/kH) = ρI σI + C. In methanol ρI, Br2 = -2·91, ρI, Cl2 = -0·49, in ethanol ρI, Br2 = -3·07, ρI, Cl2 = -0·70 and in acetic acid ρI, Br2 = -1·64, ρI, Cl2 = -0·65. The presence of C(〈0) is due to a constant steric effect. The deviation of X = H is ascribed to the absence of the steric effect and that of X = CO2Me and CO2Et is accounted for in terms of anchimeric assistance. For chlorination no anchimeric assistance was observed.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020104
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 6
    Digitale Medien
    Digitale Medien
    Kinetics and mechanism of the acid-catalyzed hydration of dihydro-1,4-dioxin (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 43-50 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The cyclic vinyl ether dihydro-1,4-dioxin is converted to its cyclic hemiacetal hydration product, 2-hydroxy-1,4-dioxane, in aqueous solution by an acid-catalyzed reaction for which kH+ = 1·80 × 10-5 M-1 S-1 at 25°C. This reactivity and the solvent isotope effect kH+/kD+ = 2·2 show that the reaction occurs by rate-determining proton transfer from catalyst to substrate and not by a pre-equilibrium mechanism as recently proposed.2
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020106
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 7
    Digitale Medien
    Digitale Medien
    The cation radical vinylcyclobutane rearrangement (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 57-88 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The cation radical vinylcyclobutane (VCB) rearrangement is found to be a reaction of substantial scope, synthetic utility, and exceptional kinetic facility. In conjuction with cation radical cyclobutanation, it constitutes an effective method for net (indirect) Diels-Alder addition to electron rich dienophiles. Reactions can be carried out with either aminium salt or photosensitized electron transfer (PET) initiation and are powerfully facilitated by ionizable substituents such as p-anisyl, phenylthio, and phenoxy at the 2-position of the vinylcyclobutane. The intramolecularity of the reaction is clearly established and in four discrete systems preferred sr (suprafacial/retention) stereochemistry is observed. A theoretical basis for sr stereochemistry in the cation radical VCB rearrangement is advanced. The transition state for the reaction is considered to be similar to that for the direct cation radical Diels-Alder cycloaddition, another cation radical pericyclic reaction which converges on the same product. This model of the VCB rearrangement transition state is used to rationalize the strong rate-retarding effect of a Z-methyl substituent attached to the vinyl group and of a methyl substituent at the 4-position of the vinylcyclobutane ring cis to the vinyl substituent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020108
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 8
    Digitale Medien
    Digitale Medien
    Multifunctional catalysis for transamination reaction of α-amino acids with glyoxylic acid in synthetic bilayer memberane (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 110-116 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The transamination reaction of α-amino acids with glyoxylic acid as catalyzed by copper(II) ions was investigated kinetically in an aqueous medium at pH 5·0 and 30·0°C. L-Phenylalanine transferred its amino group to glyoxylic acid most readily among seven different amino acids used here in the single-walled bilayer vesicle formed with N,N-dihexadecyl-Nα-[6-(trimethylammonio)hexanoyl]-L-histidinamide bromide (N+C5His2C16). Such rate enhancement was found to originate from the cooperative trifunctional catalysis: a coordination effect exercised by copper(II) ions, a general acid-base catalysis by the imidazolyl group of the lipid, and a hydrophobic field effect provided by the bilayer vesicle. Lack of any of the three functions failed to give out significant rate enhancement. As regards correlation between the reactivity and the nature of α-amino acids, the copper(II)-catalyzed transamination was progressively enhanced as hydrophobicity of the α-amino acid was increased in the N+C5His2C16 vesicle.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020204
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 9
    Digitale Medien
    Digitale Medien
    Masthead (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989) 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020301
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 10
    Digitale Medien
    Digitale Medien
    The ‘dimer mechanism’ in aromatic nucleophilic substitution by amines in aprotic solvents (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 1-14 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The mechanism of aromatic nucleophilic substitutions by amines in protic solvents is well established; on the contrary the mechanism/s of the reactions in aprotic solvents is/are still subject of controversy. The present paper describes several systems for which fourth-order kinetics (third-order in amine) were observed. A mechanism is proposed to account for this as well as other observation such as: overall negative energies of activation, quadratic dependence of kA with non-nucleophilic tertiary bases, spectacular effects of hydrogen-bond donor (HBD) and hydrogen-bond acceptor (HBA) catalysts, etc. Other alternative mechanisms are also discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020102
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 11
    Digitale Medien
    Digitale Medien
    Cross interaction constants as a measure of the transition state structure (part III). Mechanism of reactions between 1-phenylethyl benzenesulfonates with N,N-dimethylanilines (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 35-42 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The kinetics and mechanisms of the reactions between 1-phenylethyl benzenesulfonates (1-PEB) with N,N-dimethylanilines are investigated in methanol at 35·0°C. Reactivity and selectivity trends were found to be similar to those for the reactions of 1-PEB with anilines, but the magnitudes of cross interaction constants, ρXZ, between substituents X in the nucleophile and Z in the leaving group were substantially smaller indicating no hydrogen-bond bypass bridge formation in the transition state. However, the magnitude of ρXZ suggested a direct electrostatic interaction between the reaction centers in the nucleophile and leaving group in the frontside nucleophilic attack with a loose transition state structure.
    Zusätzliches Material: 6 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020105
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 12
    Digitale Medien
    Digitale Medien
    Twisted internal charge transfer emission in B,B-bis(mesityl) pyrroloboranes (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 89-92 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Spectral characteristics of several simple substituted B,B-bis(mesityl)pyrroloboranes are reported which support a theoretical treatment by Bonacic-Koutecky and Michl (J. Am. Chem. Soc. 107, 1765 (1985)) describing the excited states of simple aminoboranes as an example of twisted internal charge transfer. In the aminoboranes the pyrrolo moiety functions as the electron donor group and the empty p-orbital of the boron atom as the acceptor.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020109
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 13
    Digitale Medien
    Digitale Medien
    Masthead (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989) 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020201
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 14
    Digitale Medien
    Digitale Medien
    Reassignment of the fundamental vibrations of azetidine from ab initio calculations (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 183-186 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The harmonic vibrational frequencies were calculated analytically at the 6-31** level for azetidine using the GAUSSIAN 82 program. The results strongly indicate the presence of several errors in a recent assignment of the fundamentals of azetidine based on a normal coordinate analysis and a revised assignment is suggested. It is concluded that reliable vibrational data for azetidine in the gas phase are needed in order to resolve the remaining ambiguities in the interpretation of the spectra.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020210
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 15
    Digitale Medien
    Digitale Medien
    Mechanism of the Grignard reaction (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 205-213 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Mechanism of the Grignard reactions of aromatic ketones in THF was studied by spectroscopic and kinetic methods. The stable radical intermediates generated in the initial electron transfer from Grignard reagent to ketones are in a state of aggregated dimer of corresponding ion-radical pairs; in which two ketone anion radicals are bridged by a dimer di-cation of Grignard reagent. Subsequent alkyl radical transfer from dimeric Grignard reagent cation moiety to ketone anion radical aggregated each other are promoted by a participation of another neutral Grignard reagent. Proposed mechanism by present authors is able to explain well addition products/reduction products ratios in the Grignard reactions.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020303
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 16
    Digitale Medien
    Digitale Medien
    Non-hierarchical classification of organic solvents using characteristic vector analysis of physical and empirical solvent parameters (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 232-242 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Characteristic vector analysis of a set of six physical and empirical parameters of 103 commonly used organic solvents (bp, ∊r, μ, nD, ETN, and δ) gives four vectors describing 95% of the total data variability. Non-hierarchical cluster analysis, applied to our results, leads to ten separate classes of organic solvents.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020306
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 17
    Digitale Medien
    Digitale Medien
    A preliminary quantum-chemical study of the mechanisms for the reactions of perchlorofluoroethanes with nucleophiles initiated by chlorophilic attacks (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 103-109 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: A preliminary theoretical study of the mechanisms for the reactions of the perchlorofluoroethanes CF2ClCCl3 (1), CF2ClCCl2F (2) and CF3CCl3 (3), with nucleophiles has been carried out by the MNDO method, following the experimentally suggested process shown in Scheme 1. The unlikely chlorophilic attack in the first step of Scheme 1 has been shown to be feasible for 1, 2 and 3 by analysis of the MO interactions. The second step has been found to be affected by the anionic hyperconjugation which stabilizes the anions CF2ClCCl2- (4), CF2ClCClF- (5) and CF3CCl2- (6) and would make reactions (2) (the second step) unfeasible in gas phase, but in solution reaction (2) may still easily occur for 4 and 5.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020203
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 18
    Digitale Medien
    Digitale Medien
    Studies on organophosphorus compounds XXXII. A molecular mechanics study of the hydrolytic reaction of alkylphosphonates and alkylphosphonyl chlorides (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 146-160 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The alkaline hydrolysis of several alkylphosphonates and alkylphosphonyl chlorides has been investigated by molecular mechanics calculations (MM2, 1985 version). The difference of the steric energies (ΔE) between tetracoordinate substrate and pentacoordinate transition state of phosphorus compounds represents the activation energy (ΔE≠) in hydrolysis. The change of ΔE for various alkyl groups relative to methyl group (ΔΔER) is suggested as a measure of the steric effect of substituents. Thus the correlation analysis involving log k and ΔΔER of the branched alkyl group gives good results and it is reasonable to anticipate that analogous treatment using ΔΔER for the straight chain alkyl group is not satisfactory owing to the minor contribution of steric effect of the latter. However, the multiple regression analysis of log k with ΔΔER and Taft's σ* provides very good results. As shown by us, for the hydrolytic reactions studied, the proposed ΔΔER is much better than Taft's Es and Charton's ν, the commonly used well-known steric parameters in the chemistry of carbon compounds.
    Zusätzliches Material: 7 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020207
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 19
    Digitale Medien
    Digitale Medien
    Theoretical studies of the singlet and triplet potential energy surfaces of cyclobutanediyl (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 161-176 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Cyclobutanediyl (2) has been studied in both its singlet and triplet states by ab initio electronic structure theory. The triplet, which is the ground state of the molecule, exists in both C2h and C2v forms which interconvert via a Cs transition state. For the singlet, only a C2h form is found. It passes, via a Cs transition state, onto the C2v surface on which bicyclobutane (3) is the only minimum. The ring-flipping (inversion) process in 3 includes the singlet biradical as an intermediate, and involves a novel, non-least motion path similar to one previously proposed by Gassman. Semiclassical periodic orbit theory indicates that the various minima on both the singlet and triplet surfaces can interconvert via quantum mechanical tunneling.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020208
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 20
    Digitale Medien
    Digitale Medien
    Radioactivity detection in capillary gas chromatography of3H- and14C-labelled compounds (1989)
    Springer
    Chromatographia 27 (1989), S. 552-558 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Radio gas chromatography ; 3H- and14C-labelled compounds ; Isotope effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Radio gas chromatography (RGC) is a valuable tool for the analysis of radioactively labelled compounds. Recent advances in capillary GC, especially in column technology and instrumentation have also induced new possibilities in this field. With regard to the preservation of the achieved separation efficiency, radioactivity detection is the main problem in capillary RGC. Based on published data and on our extensive experience in conventional RGC, a simple, reliable and versatile method has been developed for the radioactive detection: purge gas is added to the effluent of the capillary column and the RGC detection unit with conversion tube and flow-through proportional counter is used maintaining small dead volumes and dimensions. The influence of the extra-column volumes and of the total gas flow rate (of the carrier, purge and quenching gases) on the peak shape was investigated. It was also found that the isotopic effect commonly known in GC of2H- and3H-labelled compounds is hardly measurable for larger [G-14C] labelled species such as [G-14C] labelled higher fatty acids with high isotopic abundance of14C, even on the highly efficient capillary columns. The quantitative aspects of the detection method used are discussed and some applications to the analysis of labelled biochemicals (amino and fatty acids) are demonstrated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02258977
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 21
    Digitale Medien
    Digitale Medien
    Gas chromatography on macroporous sulfonated cation exchangers (1989)
    Springer
    Chromatographia 27 (1989), S. 644-648 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Ion exchange resins ; Polymeric supports ; Chloromethanes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The retention of compounds of various classes on macroporous sulfonated cation exchangers in the form of the fourth period elements in Mendeleev's table (i. e. in the K, Ca, Co, Ni, Cu, Zn-forms) has been investigated. It has been shown that these sorbents are characterized by a high specificity of molecular interaction. It has also been established that the gas-chromatographic properties of cation exchangers depend on the nature and valency of the metal ion in the ionogenic group.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02258996
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 22
    Digitale Medien
    Digitale Medien
    Column packing for gas chromatography containing immobilized poly(ethylene glycol) stationary phase (1989)
    Springer
    Chromatographia 27 (1989), S. 109-112 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Packed columns ; Immobilized stationary phase ; Poly(ethylene glycol) phase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Carbowax 20M poly(ethylene glycol) stationary phase was immobilized on Chromosorb W by cross-linking with pluriisocyanate. The properties of the prepared packing material were investigated. Column efficiencies of 10,960 and 7,510 theoretical plates/meter were obtained for n-pentadecane and 1-heptanol, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02265860
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 23
    Digitale Medien
    Digitale Medien
    Effects of hydrocarbon quenching in gas chromatography when using the flame photometric detector (1989)
    Springer
    Chromatographia 27 (1989), S. 159-163 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Flame photometric detector ; Sulfur compounds ; Response quenching
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The long time retardation of the main hydrocarbon peak in the chimney of the flame photometric detector greatly reduces the responses of later-eluting sulfur compounds. In the absence of hydrocarbons in the flame, the slope (s) of the log I vs. log [S] plot (where I is the sulfur response and [S] is the sulfur concentration in the sample) is of the highest value and is constant for all experimental conditions tested. Flame hydrocarbons cause the s value to decrease, and this is dependent on the oxygen to hydrogen ratio in the flame (O/H) and, under certain conditions, also on the sulfur to carbon ratio (S/C) of the sample. The abnormalities observed in the determination of methyl thiol in natural gas are explained on the basis of the present study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02265869
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 24
    Digitale Medien
    Digitale Medien
    A simple and versatile end-sealing for static coating of wide-bore glass capillaries (1989)
    Springer
    Chromatographia 27 (1989), S. 631-632 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Wide-bore glass capillary columns ; End-sealing ; Static coating
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An end-sealing method to be used for static coating of wide-bore glass capillaries is described. After the capillary was completely filled with the coating solution, one end is connected to a gas-tight syringe (10-ml volume) via silicone tubing and the other end is fixed with shortcutted silicone tubing for sealing with a plug. The method is highly successful.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02258993
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 25
    Digitale Medien
    Digitale Medien
    Direct quantification of ethyl carbamate in distilled alcoholic beverages using a cold capillary injection system and optimised selected ion monitoring (1989)
    Springer
    Chromatographia 27 (1989), S. 209-215 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Ethyl carbamate ; Direct injection quantification ; Cold injection system ; Optimised SIM
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An integrated procedure is described which allows direct injection quantitative screening to single figure parts per billion (μg/L) levels of ethyl carbamate in the natural matrix of distilled alcoholic beverage. Injection and detection performance was studied and optimized to allow this routine, reproducible, trace analysis without any sample pre-treatment. All aspects of the analysis including autosampler run sequences and automated internal standard report generation are initiated and controlled from a single GC/MS workstation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260448
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 26
    Digitale Medien
    Digitale Medien
    Surface free energy of silane-covered materials measured by gas chromatography (1989)
    Springer
    Chromatographia 27 (1989), S. 455-460 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Surface free energy ; Silane-covered materials ; Film pressure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The surface free energy, or film pressure, π0, is measured for mica (Mica HK), silane-covered mica (Mica NP), Chromosorb W DMCS and glass beads. The film pressure is obtained from gas chromatography. The materials are used as adsorbents and benzyl alcohol and n-dodecane are used as molecular probes. Adsorption isotherms at 353 K are obtained from gas chromatography data and the surface free energy is computed with the help of the Gibbs equation. Values of π0 for a given surface are found to vary with the molecular probe. With benzyl alcohol π0 varies from 44 erg/cm2 for Mica 60 HK to 76 erg/cm2 for glass. In the case of n-dodecane π0 is found to vary in the same manner but the values range from 25 to 45 erg/cm2. The results are in good agreement with the values obtained with the contact angle method.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02319563
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 27
    Digitale Medien
    Digitale Medien
    Headspace gas chromatographic analysis for the determination of traces of ethylene oxide in sterilized materials (1989)
    Springer
    Chromatographia 27 (1989), S. 469-471 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Headspace analysis ; Ethylene oxide ; Capillary column
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A headspace gas chromatographic method for determination of traces of ethylene oxide (EO) in sterilized materials has been developed. The method allows the determination of the amount of EO by putting the samples directly into acetonitrile and analysing by means of headspace GC. The procedure described is simple, sensitive, reproducible and linear. The lower limit of detection is 0.015 μg/g of sterilized material.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02319567
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 28
    Digitale Medien
    Digitale Medien
    Gas chromatographic study of some local anesthetics (1989)
    Springer
    Chromatographia 28 (1989), S. 24-26 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Anesthetics ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A sensitive capillary gas chromatographic method is described for the simultaneous determination of lidocaine, tetracaine, procaine and dibucaine. The method was applied to the determination of anesthetics in tissue homogenates incubated at 38°C at doses between 10 and 400 mg/kg. In the liver tissue thein vitro metabolization of the studied anesthetics is most rapid for tetracaine, also fast for procaine, while for lidocaine and dibucaine the metabolization is very slow. In brain tissue thein vitro metabolization of anesthetics is very slow. The method shows good analytical parameters: linearity between 5 and 40 μg/ml; day-to-day reproducibility ca. 8% for a concentration of 20 μg/ml, precision ca. 7% for a concentration of 20μg/ml. Accuracy is also very good.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290377
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 29
    Digitale Medien
    Digitale Medien
    Sample plug tailing and cold trap effect in hot split sampling (1989)
    Springer
    Chromatographia 28 (1989), S. 639-642 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Capillary columns ; Split injection ; Sample tailing and cold trap effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Sample plug tailing together with a cold trap effect brings about discrimination against low boiling components at an initial column temperature above the boiling point of the solvent. In conventional split injection, this compensates for the opposite effects of such factors as the gas phase viscocity change and the pressure wave during the split period, and reasonable results are obtained. In stop-flow injection, however, since the influences of the opposite factors are diminished, the sample plug tailing and the cold trap effect may produce results showing lower than true concentrations for the low boiling components.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260693
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 30
    Digitale Medien
    Digitale Medien
    A novel sealing method in static coating fused-silica capillary column (1989)
    Springer
    Chromatographia 28 (1989), S. 313-314 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Fused-silica columns ; Static coating ; Sealing method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary In this paper a new sealing method for the static coating of capillary columns is described. When one end of the fully filled capillary was immersed into liquid nitrogen in a Dewar flask, the coating solution at this end would be frozen and became a temporary seal, and an air-free solvent/seal interface was obtained. No bumping has ever been found at the interface, even when butane was used as solvent. By applying this sealing method, several capillary columns, including some narrow bore capillary, had been successfully coated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260783
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 31
    Digitale Medien
    Digitale Medien
    Variation of retention index of a solute due to the presence of a large neighboring peak (1989)
    Springer
    Chromatographia 28 (1989), S. 502-504 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Retention variation ; Effect of sample composition on retention
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The variation of the retention index of a solute due to the presence of a closely neighboring peak is discussed. The neighboring peak is likely to modify the original stationary liquid by forming a temporary “mixed” stationary phase. The extent of the retention index variation is influenced by many experimental parameters and becomes pronounced when the stationary phase is overloaded by the neighboring peak and the film thickness of the stationary phase is not very large. However, the exact extent of this variation is rather unpredictable. The practical significance of this finding is also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02261069
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 32
    Digitale Medien
    Digitale Medien
    Characterization of animal fats via the GC pattern of fame mixtures obtained by transesterification of the triglycerides (1989)
    Springer
    Chromatographia 27 (1989), S. 31-36 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; FAME fingerprinting ; Animal fats ; Transesterification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The triglycerides of animal fats from milk, meat or cheese can also be characterized by the gaschromatographic pattern of the fatty acid methylesters (FAME) after conversion by an unsophisticated transesterification procedure. Even from the FAME pattern falsifications of commercial animal fats can be revealed by the fast separation of the FAME using a standard CW 20 M (polyethyleneglycol) capillary column. Characteristic patterns of FAME originating from different animals are shown. The patterns of the FAME from different races of the same animal are very similar, so that the characterisation according to the type of animal is not disturbed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290401
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 33
    Digitale Medien
    Digitale Medien
    Non-linearity in constant-current electron-capture detection (1989)
    Springer
    Chromatographia 27 (1989), S. 71-76 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Electron-capture detector ; Constant-current mode ECD ; Non-linearity of ECD
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The effects of the ionization source activity, sample input rate, electron capture rate constant, ventilation rate constant and baseline frequency on the linearity, detectability and sensitivity of the constant-current electron-capture detector (CC-ECD) were investigated. The proposed model representing an extension of the Wenthworth-Lovelock model proved to be useful in demonstrating that the CC-ECD can be highly nonlinear for strong electron capturers, at high ionization source activities, at a low ventilation rate constant and at low baseline frequencies. Optimization of the CC-ECD operation is possible by a reasonable adjustment of the studied parameters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290409
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 34
    Digitale Medien
    Digitale Medien
    Coke oven gas control by one-line gas chromatography (1989)
    Springer
    Chromatographia 27 (1989), S. 611-616 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Coke oven gas evolution ; On-line gas analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A gas chromatograph will thermal conductivity detector (TCD) connected on line via a cleaning train to the semi-industrial scale Coke Oven Text Plant of the Spanish National Coal Institute (INCAR), has been used to control the evolution of the permanent gases during the coking process. The undesirable presence of oxygen in the coke oven gas can be detected with this system that will be applied to determine the end of the coking process by quantitative analysis of the gas evolved.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02258988
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 35
    Digitale Medien
    Digitale Medien
    New approach to the GC separation of hydrocarbons by using LC-like microcolumns (1989)
    Springer
    Chromatographia 27 (1989), S. 182-184 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Micropacked columns ; Alkyl-modified silica ; Hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Micropacked columns for liquid chromatography were evaluated for the gas chromatographic separation of hydrocarbons. A glass-lined stainless-steel tube of 30 cm×0.3 mm i.d., packed with 5-μm alkyl-modified silica, was employed as the separation column. The micropacked columns were successfully applied to the separation of components of a light oil and a kerosine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260442
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 36
    Digitale Medien
    Digitale Medien
    A numerical interpolation of Kováts indices without dead time correction (1989)
    Springer
    Chromatographia 27 (1989), S. 205-208 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Kováts indices ; Numerical interpolation ; Dead time
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Comparison with normal procedures shows that numerical interpolation of the logarithms of gross retention times generates quite useful Kováts indices for gas chromatographic analysis. The dead time concept is not used in the interpolation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260447
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 37
    Digitale Medien
    Digitale Medien
    A gas chromatographic study of the adsorption of organics on thermally treated clinoptilolite (1989)
    Springer
    Chromatographia 27 (1989), S. 306-310 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Adsorption studies ; Clinoptilolite ; Zeolite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Adsorption properties of NH4-clinoptilolite, thermally treated at 400, 550 and 650°C, were investigated by gas-solid chromatography. Adsorption of ten hydrocarbons, including aliphatic, alicyclic, chlorinated and aromatic compounds is discussed in the light of adsorbate-adsorbent interactions. The imporatant thermodynamic parameters of adsorption are determined. A detailed discussion is presented on the alteration of the surface properties of NH4-clinoptilolite caused by thermal treatment. Experimental data obtained show that NH4-clinoptilolite treated at 650°C can be successfully employed as a column packing in analytical gassolid chromatography.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02321274
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 38
    Digitale Medien
    Digitale Medien
    Comparison of the gas-chromatographic properties of mesomorphic polymeric stationary phases (1989)
    Springer
    Chromatographia 27 (1989), S. 436-440 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Liquid crystal stationary phases ; PAH ; FAME ; Mesomorphic polysiloxane phases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The gas-chromatographic properties of two mesomorphic polysiloxane (MEPSIL) stationary phases, one smectic (SB) and the other nematic (N), were investigated. The retention indices and separation factors (relative retentions), α, of several pairs of polycyclic aromatic hydrocarbon (PAH) and fatty acid methyl ester (FAME) isomer solutes were used to gauge differences in the selectivity provided by each. The heats of solution of the PAH showed that the smectic MEPSIL is more selective for solutes with different length-to-breadth ratios. Also, five peaks were resolved for sixcis andtrans octadecenoic FAME isomers with this solvent. The nematic MEPSIL, on the other hand, was found to be more useful at higher temperatures because of its higher clearing point. In addition, solute capacity factors were smaller than those observed with the smectic MEPSIL, as evidenced by lower retention indices. The former was therefore more useful for the analysis of high molecular-weight PAH.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02319560
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 39
    Digitale Medien
    Digitale Medien
    Colloid stationary phases including nematic liquid crystals and high-disperse mineral particles (1989)
    Springer
    Chromatographia 28 (1989), S. 556-560 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Colloidal stationary phases ; Liquid crystals as stationary phases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Colloid systems consisting of the nematic liquid crystals p,p′-azoxyphenetol and p,p′-methoxyethoxyazoxybenzene and high-disperse mineral particles (aerosil, carbon black) are proposed to be used as stationary phases in gas chromatography. The dependence of the retention of normal paraffins, Rohrschneider and McReynolds test solutes (benzene, ethanol, methyl ethyl ketone, nitromethane, pyridine, butanol-1, 2-pentanone, and nitropropane) on the composition of the colloid systems was investigated. The investigated colloid sorbents including liquid crystals retain their selectivity for meta/para isomers up to 50% of the aerosil content and practically at all studied carbon black concentrations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260676
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 40
    Digitale Medien
    Digitale Medien
    Sampling and analysis of airborne chlorinated methanes — Comparison of FID and ECD (1989)
    Springer
    Chromatographia 28 (1989), S. 617-619 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Chlorinated methanes ; Activated charcoal sampling ; Pollution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A sampling method using activated charcoal, followed by percolation with ethanol and FID or ECD chromatographic analysis, depending on the concentrations to be monitored, makes it possible to evaluate concentrations of methylene chloride between 5 and 1000mg m−3, chloroform between 0.1 and 2000mg m−3, and carbon tetrachloride between 0.015 and 1000mg m−3.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260689
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 41
    Digitale Medien
    Digitale Medien
    The strength of interaction of highly retentive silanols with hydrocarbons on porasil C (1989)
    Springer
    Chromatographia 28 (1989), S. 139-142 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Silica surface ; Silanols ; Strongly interacting sites
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The paper describes how the method of gas-phase titration of the strongest adsorption sites can be utilized to calculate a relative strength of interaction of the sites with chromatographic solutes. An excellent correlation with earlier, theoretical predictions of Giddings is noted. Significant influence of the sites on the width of a chromatographic band is observed when the interactions are an order of magnitude stronger than those of normal sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02319635
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 42
    Digitale Medien
    Digitale Medien
    Determination of residual monomer in polymer or polymer solution by sealed glass capillary sampling (1989)
    Springer
    Chromatographia 28 (1989), S. 167-169 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Determination of monomer in polymers ; Sealed glass capillary sampling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Residual styrene in polystyrene and free phenol in phenolic plywood adhesive have been determined by sealing samples in glass capillary tubes. To prevent loss of sample the ends of the capillary tubes were sealed with a kind of putty made of anhydrous calcium sulfare, calcium carbonate and a small quantity of phenylmethylsilicone fluid. No volatile compounds were released from this sealing material when the capillary tubes were placed in a quartz vaporising furnace at temperatures up to 300°C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02319641
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 43
    Digitale Medien
    Digitale Medien
    An experimental study of residual chemicals in elastomeric stoppers for injectables: a MS/GC survey and a headspace/GC purity test (1989)
    Springer
    Chromatographia 28 (1989), S. 545-550 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; GC/MS and headspace GC ; Elastomeric stoppers for injectables ; Trace hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Elastomeric stoppers for injectables have been surveyed by means of GC/MS screening. Residual contamination by hexanes (2-methylpentane, 3-methylpentane, n-hexane, methylcyclopentane, cyclohexane) toluene and xylenes occurred in all the samples tested. A headspace GC purity test is suggested, by using these residual chemicals as purity indexes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260674
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 44
    Digitale Medien
    Digitale Medien
    Computer optimization of separation in gas-solid chromatography, optimization model and computer-modified mapping procedure (1989)
    Springer
    Chromatographia 28 (1989), S. 274-278 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Optimization of gas-solid separations ; Plate height equation ; Computer mapping procedure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary This paper proposes an optimization model for gas-solid chromatographic separations in a non-linear programming form and an approximate equation of the plate height for the model. A computer-modified mapping procedure is also described for searching the optimum separation conditions. Just five experiments and about 20 minutes of the computer time are needed to establish the optima of column temperature and of the carrier gas linear velocity. The relative deviation between the predicted and the experimental values was found to be within 20% for the plate heights, and within 1.5% for the retention times.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260774
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 45
    Digitale Medien
    Digitale Medien
    Monte-carlo simulation of gas chromatographic separation for the prediction of retention times and peak half widths (1989)
    Springer
    Chromatographia 28 (1989), S. 241-248 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Renewal theory ; Monte-Carlo simulation ; Prediction of retention and peak widths
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A new method for prediction of gas chromatographic retention times and peak half widths is based on the renewal theory. The only requirements are the heats of vaporization of the compounds to be separated and one calibration measurement. With this data, retention times and peak half widths can be predicted for isothermal as well as temperature-programmed gas chromatography. For the separation of non-polar substances on non-polar stationary phases the prediction error for retention times is approx. 1–2%. First simulations of polar molecules and polar stationary phases indicate that this method is also applicable in these cases but some extension will be required.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260768
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 46
    Digitale Medien
    Digitale Medien
    Detection of thiophenes in the offgas condensate of an oil shale retort by a GC-microwave induced helium plasma detector (1989)
    Springer
    Chromatographia 27 (1989), S. 44-48 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Microwave plasma detector ; Thiophenes ; Shale oil distillates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A series of alkylthiophenes and dimethyl disulfide were tentatively identified in an oil shale retort gas condensate from a 6-kg bench-scale retort using gas chromatography with a microwave-induced helium plasma detector (GC-MIP). The sulfur species were present in concentrations ranging from 1.5 to 10.7 mol ppm in the undiluted offgas. The GC-MIP technique was successful in selectively detecting the sulfur components in the complex mixture. Quantitation was simplified relative to GC with flame-photometric detection because of the absence of quenching or other interference problems at the concentrations studied. Attempts to determine stoichiometry of the sulfur components by comparison of carbon, hydrogen, and sulfur ratios with those of standards were unsuccessful because of the complexity of the carbon and hydrogen chromatograms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290403
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 47
    Digitale Medien
    Digitale Medien
    Automatic determination of selected C2–C4 hydrocarbons in urban air by solid sorbent sampling and gas chromatography (1989)
    Springer
    Chromatographia 27 (1989), S. 55-59 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Air pollutants ; Adsorbent enrichment ; Thermal desorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A new automatic method is described for quantitative determination of some light C2–C4 hydrocarbons in urban air: ethene, ethyne, propane, propene, butane and iso-butane. This method is based on an enrichment step at room temperature using a solid sorbent and subsequent thermal desorption for gas chromatographic separation and FID detection. The instrument is built up of a small commercial gas chromatograph and a laboratory-made trap and desorption unit. The sampling parameters, sample volume, concentration and humidity of air have been investigated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290406
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 48
    Digitale Medien
    Digitale Medien
    Gas Chromatographic/mass spectrometric analysis of azines (1989)
    Springer
    Chromatographia 27 (1989), S. 596-600 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Mass spectrometry ; Azines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary We have studied the gas chromatographic behaviour of several 3-methyl-2-benzothiazolone-azines. In HPLC analysis all the unsymmetrical azines show double peaks, whereas in HRGC analysis only some of these compounds show the two peaks corresponding to the Z (syn) and E (anti) isomers. By means GC/MS analysis the mass spectrum of each azine was recorded. We have assigned the E and Z configurations to the first and second gas chromtographic peaks on the basis of the ratio between the relative abundances of the two most significant framment ions at m/z 163 and 164.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02258985
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 49
    Digitale Medien
    Digitale Medien
    Large volume sample application by a simplified “closed” on-column injector in capillary gas chromatography (1989)
    Springer
    Chromatographia 27 (1989), S. 221-224 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Large volume sample injection ; Closed on-column injector
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A new simplified version of a “closed” on-column injector is introduced. Because of its design isobaric injection conditions do not have to be followed and a wide range of injection temperatures above the boiling point of the sample solvent can be chosen for on-column injections in capillary gas chromatography. Also, when following certain basic injection rules, injections of large sample volumes (≥20 μl or more) give accurate and reproducible results without further problems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260450
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 50
    Digitale Medien
    Digitale Medien
    Amino acid profiling using HRGC-FTIR oftert.-Butyldimethylsilyl derivatives (1989)
    Springer
    Chromatographia 27 (1989), S. 233-237 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; FTIR ; Hemoglobin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The use of N, O (S)-tert.-Butyldimethylsilyl derivatives of amino acids for capillary gas chromatography and FTIR identification of amino acids is described. Rapid identification is achieved by computerised comparison of FTIR spectra. Derivatives that are characterised by identical sets of ions in gas chromatography-mass spectrometry experiments are clearly distinguished and identified by means of their infrared spectra. This, for example, is the case with alanine, β-alanine and sarcosine, which norvaline and valine, and with norleucine, leucine and isoleucine. Unknows are also promptly detected. This is especially useful in screening biological samples for less common amino acids. Screening of hemoglogin hydrolysates for amino acid adducts is exemplified.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260453
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 51
    Digitale Medien
    Digitale Medien
    Detemination of carboxylic acids in biological samples as their trichloroethyl esters by gas chromatography (1989)
    Springer
    Chromatographia 27 (1989), S. 483-488 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Trichloroethyl ester ; Dicarboxylic acid ; Urine samples ; Electron capture ; Biological monitoring
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Dicarboxylic acids were esterified by 2,2,2-trichloroethanol by using trifluoroacetic anhydride and phosphoric acid as catalysts. The method was developed to facilitate the evaluation of workers' exposure to sensitising acid anhydrides and other compounds metabolised to acids in the body. The sensitivity of the acid determination in urine was in the order of 2–4 ng ml−1 for aliphatic and alicyclic acids and 15ng ml−1 for phthalic acid.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02319570
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 52
    Digitale Medien
    Digitale Medien
    Some comments on the “Space charge” model of electron-capture detector (1989)
    Springer
    Chromatographia 27 (1989), S. 499-508 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Electron capture detector ; Space-charge model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Mathematical analysis, allowing the determination of the distribution of the electron and positive ion concentration in an electron-capture detector with a cylindrical electrode arrangement and with constant and pulsed voltage supplies, has been carried out. The measurements obtained confirm the assumptions concerning the “space change” model of the ECD introduced by Gobby et al. and cast doubt upon the general assumption of the complete removal of the electrons from the detector by the voltage pulse. The physical factors influencing the current characteristics of the detector and the possible distortions connected with the electrode geometry have been explained on the basis of the measurements carried out.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02319573
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 53
    Digitale Medien
    Digitale Medien
    Physicochemical quantities in catalytic reactions measured simultaneously by gas chromatography (1989)
    Springer
    Chromatographia 27 (1989), S. 333-339 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Catalytic reactions ; Adsorption and desorption rate constants ; Reversed-flow techniques
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A small volume of reactant, 1-butene, is injected onto a catalytic bed and is allowed to diffuse away from it together with the product butane, along a narrow empty chromatographic tube; the latter is connected perpendicularly to the middle point of another similar tube through which hydrogen flows as reactant and carrier gas, transferring both 1-butene and butane to the detector through an analytical column. By using the reversed-flow GC technique, extra peaks are obtained in the chromatographic trace, sampling the concentration of both the readtant and product at the junction of the two tubes as a function of time. These concentrations are the result of the diffusion of the substances along the narrow empty tube, modified by the adsorption-desorption rates and the rate of the catalytic reaction. From the extra peaks of the reactant and product, a number of physicochemical quantities pertaining to the catalytic reaction can be calculated simultaneously, using appropriate mathematical analysis. These include adsorption rate constants, reaction rate constants, desorption rate constants, partition coefficients, and the overall mass transfer coefficients of the reactant across the gas-solid boundary of the catalytic bed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02321280
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 54
    Digitale Medien
    Digitale Medien
    Thermodynamic evaluation of the intermolecular interactions of potassium fluoride crystal dihydrate in gas chromatography (1989)
    Springer
    Chromatographia 28 (1989), S. 179-182 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; KF·2H2O as stationary phase ; Alcohols ; Organic bases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Potassium fluoride crystal dihydrate is used as the stationary phase for the rapid analysis of polar compounds in aqueous solutions. KF·2H2O is compared with some conventional stationary phases, organic salts and molten crystal hydrates of inorganic salts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02319643
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 55
    Digitale Medien
    Digitale Medien
    Uncertainty resulting from inconstancy in the slope of the log plot of homologous series (1989)
    Springer
    Chromatographia 28 (1989), S. 237-240 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Slope of log plot ; Homologous series ; Retention index ; Retention time ; Uncertainty ; Free energy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The free energy of partition of a methylene group $$\Delta G_{CH_2 }^ \circ $$ is constant within a homologous series down to C5 and nearly constant to C3, contrary to the finding of Golovnya and Grigoryeva [5]. Retention indices are linear with carbon number: values may be extrapolated from higher carbon numbers to C5 within experimental uncertainty, to C4 with error no greater than 5 units and to C3 with error no greater than 10 units. Error in extrapolating the logarithm of the adjusted retention time, log t′R, to C5 is thus negligible, to C4 has possible error up to 5b/100 and to C3 up to 10b/100, whereb is the slope of the plot of log t′R against carbon number.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260767
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 56
    Digitale Medien
    Digitale Medien
    Optimization in equilibrium headspace GC/FTIR (1989)
    Springer
    Chromatographia 28 (1989), S. 631-638 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Headspace GC/FTIR ; Optimization ; Detection limits ; Cryogenic trapping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary For the trace analysis of volatile components in a nonvolatile matrix, the headspace sampling technique offers the potential to lower detection limits in GC/FTIR experiments. Optimization of chromatographic operating parameters for Headspace GC/FTIR is discussed, aiming at the best compromise between maximum chromatographic resolution and highest S/N ratio of the infrared spectra. It is shown that the combination of headspace sampling with cryogenic capillary head trapping is able to provide Headspace GC/FTIR with the best performance in terms of sensitivity and chromatographic resolution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260692
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 57
    Digitale Medien
    Digitale Medien
    Dicyclopentadiene dissociation in a chromatographic reactor. Effect of the liquid phase polarity on the reaction rate (1989)
    Springer
    Chromatographia 28 (1989), S. 300-302 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Reaction rate studies ; Dicyclopentadiene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The gas chromatographic reactor technique was used to study the kinetics of dicyclopentadiene dissociation in several liquid phases (Versamid 900, neopentyl glycol sebacate, Triton X-305, Carbowax 6000, ethylene glycol phthalate and diethylene glycol succinate). Reaction rates and Arrhenius parameters are reported in the temperature range of 170–200°C. Kinetic data for the lower polarity liquid phases are in good agreement with literature values for liquid phases of the same nature reported previously. Reaction rates are higher when polar liquid phases are used. This behavior can be explained as a result of side reactions which lead to high molecular weight compounds which can be observed in the reaction chromatogram.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02260779
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 58
    Digitale Medien
    Digitale Medien
    Basic aspects of stop-flow split injection (1989)
    Springer
    Chromatographia 28 (1989), S. 385-390 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Capillary column ; Split injection ; Stop-flow method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Major concerns in the development of the stop-flow split injection are discussed. Split ratio fluctuation caused by the pressure wave, solvent recondensation and gas viscosity change can be substantially diminished through the formation of a nearly uniform gaseous sample plug. Instrumental variables exerting influence on the accuracy of quantitation were studied. Higher injector temperature and the use of a carrier gas with higher heat conductivity benefit the quick vaporization of the sample liquid, and thus, help in the formation of a sample plug with more unformity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02261020
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 59
    Digitale Medien
    Digitale Medien
    A simple method for concentrating volatile flavor compounds in aqueous systems using RP-HPLC (1989)
    Springer
    Chromatographia 28 (1989), S. 405-411 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Gas chromatography ; Concentration of volatile flavor compounds ; ODS packing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Volatile flavor compounds in aqueous model systems, distillates of coffee extract and juices such as apple, tomato, pineapple and grape were adsorbed on an ODS column during HPLC and monitoring absorption at 280nm. The adsorbed volatile compounds were eluted with a small volume of ethanol. Volatile compounds in the eluates were concentrated 22 to 100 times those in the distillates. Recovery of compounds was 50–90%. Breakthrough of specific compounds such as γ-valerolactone, furfuryl acetate and t-2-hexenal in the model systems and several compounds in the juice distillates was detected by capillary GC. Pattern similarity calculated between the GC profiles of a juice distillate and the corresponding eluate gave a qualitative comparison. This novel and versatile method utilizing conventional RP-HPLC may be widely applicable for concentrating volatiles in aqueous systems, at levels from ppm to ppb.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02261023
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 60
    Digitale Medien
    Digitale Medien
    Fused silica columns for high-temperature simulated distillation (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 181-183 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Column technology ; Simulated distillation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120316
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 61
    Digitale Medien
    Digitale Medien
    Analysis of methyl tert-butyl ether and 1,2-dihaloethanes in estuarine water and sediments using purge-and-trap/gas-chromatography (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 184-186 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Purge-and-trap ; Environmental tracers ; Motor vehicle exhaust ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120317
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 62
    Digitale Medien
    Digitale Medien
    Applications of coupled LC-GC: A review (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 193-207 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Multidimensional chromatography ; Liquid chromatography ; Gas chromatography ; Gupercritical fluid chromatography ; Fuels ; Foodstuffs ; Environmental ; Biological ; Pharmaceutical ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Although coupled liquid chromatographygas chromatography (LC-GC) was first demonstrated ten years ago, only in the last few years has there been a sudden surge of interest in the technique. Approximately 70% of the total number of LC-GC applications have been published in the last two years (1987-88) alone. This review categorizes LC-GC publications into four main application areas: fossil fuels, foods, environmental samples, biologiical/pharmaceutical samples, and miscellaneous samples. Multidimensional separations carried out using other coupled-column chromatographic techniques (such as supercritical fluid chromatography (SFC) with GC, and on-line trace enrichment-GC) have also been included in this review.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120402
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 63
    Digitale Medien
    Digitale Medien
    Systematic investigation of enantiomer resolution of N-pivaloyl derivatized amino acid esters. Preparation of glass capillary columns coated with the chiral phase XE-60-L-val-pea (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 213-217 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Capillary columns, glass ; XE-60-L-valine-(S)-α-phenylethylamide ; Amino acid derivatization, general procedure ; N-Pivaloyl amino acid esters ; Amino acid enantiomer separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A laboratory working procedure is described for silanization of glass capillaries with bis(cyanopropyl)tetramethyldisiloxane, prior to coating with XE-60-L-valine-(S)-α-phenylethylamide as chiral stationary phase. GC columns thus prepared exhibit good inertness and no long-term deterioriation of enantioselectivity up to 220°C. A general procedure is given for derivatization of simple and of polyfunctional amino acids, in a batch mixture, simultaneously, and completely at both the N- and the C-terminus and all other protic functions. Within the seven series of N-pivaloyl amino acid esters tested (methyl to neopentyl), baseline separation is obtained for all R/S pairs, including the proline derivative.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120405
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 64
    Digitale Medien
    Digitale Medien
    Capillary gas chromatographic analysis of amino acids in geological environments with electron capture detection (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 239-243 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Fused-silica capillary ; Electron-capture detection ; Amino acid biogeochemistry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Studies have been performed on the analysis of 21 amino acids using a fused-silica open tubular (FSOT) capillary column, and electron-capture detection (ECD) or flame-ionization detection (FID). It was shown with the N(O)-heptafluorobutyryl (HFB) amino acid isobutyl esters that the ECD response was several hundred times more sensitive than the FID response. The relative standard deviation (RSD) of retention relative to norleucine is determined with the ECD. RSD values for all N(O)-HFB amino acid isobutyl esters are relatively small (≦ 0.5%). This method has been successfully applied to trace analysis of most of the amino acids from fossil brachiopods and black shales.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120410
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 65
    Digitale Medien
    Digitale Medien
    A new configuration for coupling purge-and-trap/cryogenic focusing/capillary column gas chromatography with splitless injection mode (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 779-783 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Capillary column ; Purge-and-trap ; Cryogenic focusing ; Splitless injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new configuration for coupling a purge-and-trap unit to a capillary column gas chromatograph via a cryogenic focusing interface has been developed. In this configuration, the precolumn of the cryogenic focusing interface was inserted through the septum of a split/splitless injection port where it served as both sample transfer and carrier gas supply lines. The injection port of the gas chromatograph was modified by plugging the carrier gas and the septum purge lines. This configuration allowed for the desorption of analytes at high flow rates while maintaining low, analytical-column flow rates which are necessary for optimum capillary column operation. The capillary column flow rate is still controlled by the column backpressure regulator. Chromatograms of purgeable aromatics exhibited improved resolution, especially for early eluting components compared to those obtained by direct liquid injection using the normal splitless injection mode. Quantitative sample transfer to the analytical column afforded excellent linearity and reproducibility of compounds studied.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240121203
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 66
    Digitale Medien
    Digitale Medien
    Gas chromatographic method for simulated distillation up to a boiling point of 750°C using temperature-programmed injection and high temperature fused silica wide-bore columns (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 16-22 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Wide bore capillary columns ; Temperature programmed injection ; Simulated distillation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: It is demonstrated that linear injection characteristics are obtained for a wide boiling point range sample using a temperature-programmed injector in combination with wide-bore fused silica columns. The applicability of the described combination for high temperature simulated distillation is described. The method, using external standardization, gives accurate and repeatable results for different types of samples in the boiling range between 50 and 750°C. The lifetime of the fused silica wide-bore columns was found to be acceptable, viz. over 80 temperature-programmed cycles between ambient and 430°C. Some comments are made on the accuracy of boiling points for normal alkanes.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120106
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 67
    Digitale Medien
    Digitale Medien
    New methodologies in trace analysis of volatile organic compounds (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 138-141 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Volatile samples ; Sample enrichment ; Trace analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Two methods for sampling and concentration of volatile organic compounds are reported. In the first method, traps coated with a very thick film (ca. 100 μm) of cross-linked silicone stationary phase are employed. Such thick films can be prepared with a modified dynamic coating procedure, which is briefly described. The low phase ratio traps can be utilized for enrichment of volatiles from gaseous as well as aqueous matrices.The second technique is based on chromatographic evaporation of a solvent in a capillary tube, where the process is sustained by a repeated sample injection and a cyclic flow reversal. In this way, large solvent volumes can be handled by a small volume system. Under optimal conditions, when using a solvent barrier, quantitative recovery is possible even for compounds of comparatively high volatility. Another important application of the technique is extraction of trace components from gases such as headspace samples, polluted air, etc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120305
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 68
    Digitale Medien
    Digitale Medien
    The computer-aided optimization of capillary columns for minimum time analysis and minimum detectabiliy (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 149-160 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Optimization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A model utilizing the extended Golay-Giddings equation, with an added term that expresses the instrumental contributions to the plate height, has been tested and found to accurately predict the chromatograph's output for a given set of operating conditions. The model forms the basis of a computer program that will recommend the length of column (of a specified inside diameter and film thickness) to be used (at a given temperature and input pressure) to obtain a minimum time analysis of the most difficult to separate pair of the mixture. Alternative solutions are available that specify the length of column, operating pressure, and the maximum permissible sample size required to provide a minimum analysis time for a system with specified minimum detection limits.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120307
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 69
    Digitale Medien
    Digitale Medien
    Quantitative determination of oxocarboxylic and hydroxycarboxylic acids in normal individuals and ketoacidotic patients (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 160-163 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Sample preparation ; Urine analysis ; Oxocarboxylic acids ; Hydroxycarboxylic acids ; Ketoacidosis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Oxo- and hydroxycarboxylic acids as metabolites of valine, leucine, and isoleucine and of ketogenesis are simultaneously quantitated in the form of their methyl esters and methyl esters/O-methyloximes by gas chromatography using internal and external standards. Normal values for the urinary excretions of the amino acid metabolites are between 3 ± 2 μmol/24 h (mean value ± standard deviation) for 2-oxoisocaproic acid and 122 ± 58 μmol/24 h for 3-hydroxyisobutyric acid. In diabetic ketoacidosis the values are increased by a factor of 2-10.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120308
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 70
    Digitale Medien
    Digitale Medien
    Determination of amino acids in human cerebrospinal fluid by gas chromatography (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 234-238 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Packed column ; Wide bore column ; Fused silica column ; Amino acids ; Cerebrospinal fluid (CSF) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In the present study, the use of gas chromatography (GC) for the determination of amino acids in human cerebrospinal fluid (CSF) is described. Although some amino acids may be determined using a packed column following the removal of glucose, the major interfering component, the inadequate resolution of other amino acids from remaining unidentified components results in poor quantitation. The use of wide bore columns improves reproducibility considerably, but still it does not provide sufficient resolution to enable quantitative determination of all amino acids in human CSF. Good reproducibility data, with CV values for all amino acids of 7% or less and recoveries generally between 80% and 100%, can only be obtained using the fused silica open tubular (FSOT) column. Normal amino acid levels are presented for 10 samples of human CSF, which compare well with data previously reported in the literature.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120409
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 71
    Digitale Medien
    Digitale Medien
    Determination of amino acids in urine by gas chromatography (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 437-441 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Fused silica column ; Amino acids ; Urine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This report describes a convenient means of reducing the complex matrix which is responsible for interference during gas chromatographic determination of amino acids in urine. The pre-chromatographic clean-up employs the principle of solid phase extraction using bonded silica incorporating cation exchange groups. This approach avoids the detrimental effects on amino acid recoveries associated with resin-based cation exchangers. In spite of significant reduction in the complexity of chromatograms, only the high efficiency and resolving power offered by the analytical capillary column (e. g. fused silica open tubular, FSOT) is sufficient for quantitative and analysis of amino acids in urine. Reproducibility data from the complete procedure are determined, coefficients of variation (CV) for most amino acids being better than 5% with a mean recovery of 96%.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120703
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 72
    Digitale Medien
    Digitale Medien
    Gas chromatographic determination of amino acids in river water by enantiomer labeling (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 661-664 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Enantiomer labeling method ; Amino acids in river water ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240121006
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 73
    Digitale Medien
    Digitale Medien
    Chromatographic properties of various polysiloxane stationary phases for separation of 2,3,7,8-chloro-substituted dibenzo-p-dioxin and dibenzofuran isomers-a systematic comparison (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 665-668 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Glass capillary columns ; OH-Terminated polysiloxane phases ; PS-347.5, OV-17-OH, OV-240-OH ; SP-2330 ; Polychlorinated dibenzo-p-dioxin ; Polychlorinated dibenzofuran ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Glass capillaries coated with four crosslinked and surface-bonded OH-terminated polysiloxanes [PS 347.5, OV-17-OH, OV-225-OH, and OV-240-OH] were compared with commonly used methyl-terminated SP-2330-coated columns with respect to their selectivity for the separation of 2,3,7,8-chloro-substituted dibenzo-p-dioxins and dibenzofurans. The methyl- and phenyl-substituted phases [PS 347.5 and OV-17-OH] exhibit only moderate isomer selectivity which limits their applicability in this field. The examined 3-cyanopropyl-substituted phases [OV-225-OH, OV-240-OH, and SP-2330] allow complete separation of all 2,3,7,8-chlorosubstituted PCDDs and PCDFs. With SP-2330 longer columns are required (50 m) for baseline separation of critical groups of isomers. OV-225-OH was found to be the most suitable phase as to isomer selectivity. In comparison to SP-2330, the analysis times can be reduced by a factor of two.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240121007
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 74
    Digitale Medien
    Digitale Medien
    Gingerol analysis without artifact formation (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 677-679 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Mass sprectrometry ; Ginger ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240121011
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 75
    Digitale Medien
    Digitale Medien
    Chromatographic and chemical study of Berberis ruscifolia Lam. of regional origin (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 691-692 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Berberis ruscifolia Lam. ; Berberidaceae ; Hydrocarbons ; Alcohols ; Sterols ; Anthocyanins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240121015
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 76
    Digitale Medien
    Digitale Medien
    γ-Immobilized SE-30 on chromsorb supports for use in packed-column gas chromatography (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 500-502 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Non-polar stationary phase ; Immobilization ; γ Irradiation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120724
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 77
    Digitale Medien
    Digitale Medien
    Gas chromatographic determination of organolead compounds with an alternating current plasma detector (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 522-526 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Plasma emission detection ; Alternating current plasma detector ; Organolead ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The performance of the gas chromatography/alternating current plasma detector as a selective detector for organolead compounds is investigated. The helium make-up flow rate and the spatial position from which the lead emission is viewed, have an effect on the detector response. The detection limit for tetrabutyl lead was established as 130 pg/s and the lead selectivity ratio was found to exceed 13,800. Some applications of organolead determination in complex matrices were also studied in order to demonstrate the selectivity and sensitivity of the alternating current plasma detector.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120805
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 78
    Digitale Medien
    Digitale Medien
    A new method for in situ crosslinking of stationary phases on fused silica capillary columns (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 537-539 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Capillary columns ; Crosslinking ; Stationary phase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A new mixed crosslinking agent composed of dicumyl peroxide and tetra(methylvinyl)cyclotetrasiloxane was used to prepare fused silica capillary columns with in situ crosslinked stationary phases including PEG-20M, SE-54, and OV-1. These columns proved to have good thermostability and inertness. As examples of potential applications a mixture of isomers of nitrotoluene and dinitrotoluene, and pyrolyzates of polystyrene were separated by using these columns.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120808
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 79
    Digitale Medien
    Digitale Medien
    Effect of molecular structure on the retention parameters of cyclic ketone diperoxides in different stationary phases (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 423-425 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Tetraoxanes ; Structural effects ; Kováts index ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120623
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 80
    Digitale Medien
    Digitale Medien
    Simple method to prepare non-polar wide-bore columns for gas chromatography (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 431-432 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Wide bore columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120627
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 81
    Digitale Medien
    Digitale Medien
    Sampling device for a simple, fast calibration technique in gas chromatographic trace analysis of gas phases and vapor phasesVapor phase=gas phase in contact with the liquid or solid phase of the same substance. (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 742-748 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Gas phase analysis ; Calibration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In order to accommodate continually changing tasks in the [μl/l]-[nl/m3] ranges of gas chromatographic trace analysis of gas phases and vapor phases, a simple and time-saving calibration technique is presented which renders unnecessary conventional test mixtures of the abovementioned concentration ranges.This new method is based on the simulation of such mixtures at the inlet of the GC unit with the aid of commercially available multiway sampling valves of various volumes by means of partial pressure sampling.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240121110
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 82
    Digitale Medien
    Digitale Medien
    Separation and quantification of the ethylfluoro and the dimethylfluoromethyl derivatives from their parent silicon compounds by gas chromatography (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 430-431 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; Separation and identification ; Silicon-containing compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jhrc.1240120626
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 83
    Digitale Medien
    Digitale Medien
    Non-linear stochastic response of marine vehicles (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 27 (1989), S. 169-183 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The dynamic behaviour of marine vehicles in extreme sea states is a matter of great concern following some recent and dramatic mishaps. The complex problem of its prediction can be approached from the study, yet of broader scope, of non-linear dynamic systems subjected to stochastic excitations. However, a general non-linear stochastic dynamic theory is not yet available.A new technique, the so-called linearize-and-match method, for predicting the response statistics of non-linear systems, is presented. Essentially, the technique involves the construction of an infinite series of linear systems aimed at the prediction of the response statistical moments of a given order.The linear systems are successively defined by linearizing the original, non-linear system and matching the Volterra functional model response statistics to the desired order. The linear system for predicting second order statistics is shown to coincide with the one obtained using the method of equivalent linearization.Response probability distributions can be constructed from the knowledge of such statistics. Particular attention is devoted to the distribution of maximum entropy and its justification in such underdetermined moment problems.Finally, applications to the roll motion of ships serve to exemplify as well as to assess the accuracy and the versatility of the overall method. Response distributions of maxima so predicted compare very well with digital simulation estimates.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620270114
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 84
    Digitale Medien
    Digitale Medien
    F.E. solution of a vertically averaged model for regional land subsidence (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 27 (1989), S. 215-230 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: In this paper a mathematical model is presented, based on the application of an averaging technique, in which the equations governing the behaviour of saturated porous media are integrated (averaged) over the smallest dimension of the domain of the problem (thickness). This results in a two dimensional model, in which the three dimensional nature of the problem is accounted for. In fact, the solution is sought in terms of the mean values over the thickness of the field variables and of the transverse displacement components. For the solution of the resulting governing equations a partitioned procedure is employed, which improves the efficiency of the method. The proposed model is very useful in solving problems in which the spatial nature prevents the applications of two dimensional models.Examples are presented, which illustrate the validity of this approach.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620270117
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 85
    Digitale Medien
    Digitale Medien
    Some recent developments in numerical modelling of fracture toughness in brittle matrix composites (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 27 (1989), S. 233-255 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Finite element analysis was used to study the fracture toughening of a ceramic by a stress induced dilatant transformation of second phase particles. The finite element method was based on a continuum theory which modelled the composite as subcritical material. Transient crack growth was simulated in the finite element mesh by a nodal release technique. The crack's remote tensile opening load was adjusted to maintain the near-tip energy release rate at the level necessary for crack advance. The transformation zone surrounding the crack developed as the crack propagated through the composite. Resistance curves were computed from the analysis; and the results show that during crack advance maximum toughness is achieved before a steady state is reached.The toughening effect of a crack-bridging ductile phase in a brittle material may be predicted if ligament deformation is characterized. A plastically deforming ligament constrained by surrounding elastic matrix material is modelled using finite elements and the relevant toughness enhancement information extracted. Comparison is made to model experiments as well as to toughness measured for technologically important materials. The results suggest that debonding along the interface between the ligament and the matrix may enhance the toughening effect of a ductile phase.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620270203
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 86
    Digitale Medien
    Digitale Medien
    Fatigue life estimation of graphite/epoxy laminates under consideration of delamination growth (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 27 (1989), S. 323-341 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A closed form approach to the assessment of the fatigue life of graphite/epoxy laminates under cyclic tension-compression loading has been developed. The model is mechanistic and uses cyclic energy release rates for prediction of delamination growth and of critical delamination sizes which induce buckling and the final failure of the laminates. Tests performed with graphite/epoxy specimens of stacking order [0n, φm]s with severed central plies [φ], and of stacking order [02, +45, 02, -45, 0, 90]s with a central unloaded hole, indicate good correlation between estimated values and observed delamination growth, critical buckling strength of separated plies and load cycles to failure.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620270208
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 87
    Digitale Medien
    Digitale Medien
    Analysis of viscoelastic structural elements in the frequency domain (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 27 (1989), S. 429-436 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper presents a formulation in the frequency domain for the viscoelastic material behaviour of structural elements. This approach is equally valid for deterministic forces, but also in the case of probabilistic descriptions of those forces. The method takes advantage of readily available experimental data and shows how to introduce them in e.g. finite element formulations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620270213
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 88
    Digitale Medien
    Digitale Medien
    Conference diary (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 27 (1989), S. 449-452 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620270215
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 89
    Digitale Medien
    Digitale Medien
    A dual adaptive procedure for the automatic determination of iteration parameters for Chebyshev acceleration (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 27 (1989), S. 483-499 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Chebyshev acceleration for a symmetrizable basic iterative method u(n+1) = Gu(n) + k; requires estimates of the extreme eigenvalues m(G) and M(G) of the iteration matrix G. Adaptive procedures are often used in order to obtain good estimates for m(G) and M(G). Some existing adaptive procedures are able to give an estimate of either m(G) or M(G) but not both on any given iteration. In this paper we present an adaptive procedure which can estimate both m(G) and M(G) at the same time and which has other useful properties. Numerical results are given which show the new procedure usually requires fewer iterations than previous procedures.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620270305
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 90
    Digitale Medien
    Digitale Medien
    Experience with the conjugate gradient method for stress analysis on a data parallel supercomputer (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 27 (1989), S. 523-546 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The storage requirements and performance consequences of a few different data parallel implementations of the finite element method for domains discretized by three-dimensional brick elements are reviewed. Letting a processor represent a nodal point per unassembled finite element yields a concurrency that may be one to two orders of magnitude higher for common elements than if a processor represents an unassembled finite element. The former representation also allows for higher order elements with a limited amount of storage per processor. A totally parallel stiffness matrix generation algorithm is presented. The equilibrium equations are solved by a conjugate gradient method with diagonal scaling. The results from several simulations designed to show the dependence of the number of iterations to convergence upon the Poisson ratio, the finite element discretization and the element order are reported. The domain was discretized by three-dimensional Lagrange elements in all cases. The number of iterations to convergence increases with the Poisson ratio. Increasing the number of elements in one special dimension increases the number of iterations to convergence, linearly. Increasing the element order p in one spatial dimension increases the number of iterations to convergence as pα, where α is 1·4-1·5 for the model problems.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620270307
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 91
    Digitale Medien
    Digitale Medien
    On an SSOR matrix relationship and its consequences (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 27 (1989), S. 559-570 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A matrix relationship connecting the Jacobi and the Symmetric Successive Overrelaxation (SSOR) matrices associated with a k-cyclic consistently ordered matrix A is presented. Next the equivalence of the SSOR method and a certain monoparametric k-step one for the solution of the linear algebraic system Ax = b is established. The aforementioned equivalence can be exploited to derive regions of convergence, optimum parameters involved, etc. of the two iterative methods above. This is done by studying the simplest of the two methods that is the monoparametric k-step one. To show how the idea works the case k = 2 is very briefly discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620270309
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 92
    Digitale Medien
    Digitale Medien
    On a class of preconditioned iterative methods on parallel computers (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 27 (1989), S. 637-654 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The standard implementations of iterative solvers for finite element and finite difference methods frequently use a diagonal (Jacobi) preconditioner, particularly for element-by-element schemes. However, for such methods the actual order of the condition number with respect to mesh size is not reduced by the preconditioner. In the present paper we describe an iterative method where, in addition, the condition number is reduced by an order of magnitude. Moreover, the scheme may also be implemented as an element-by-element method. The method uses a generalized SSOR preconditioner and a wave front or multi-frontal ordering of the mesh nodes. For a general irregular finite element mesh a striped irregular wave front ordering may be used. The performance of the method as well as various iterative acceleration techniques for a parallel computer are examined in the numerical studies.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620270314
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 93
    Digitale Medien
    Digitale Medien
    Correction (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. ii 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620280102
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 94
    Digitale Medien
    Digitale Medien
    Geometrically non-linear formulation for three dimensional curved beam elements with large rotations (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 43-73 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: This paper presents a geometrically non-linear formulation (GNL) for the three dimensional curved beam elements using the total Lagrangian approach. The element geometry is constructed using co-ordinates of the nodes on the centroidal or reference axis and the orthogonal nodal vectors representing the principal bending directions. The element displacement field is described using three translations at the element nodes and three rotations about the local axesThe element displacement field has also been described in the literature using Euler parameters, Milenkovic parameters, or Rodriges parameters representing the effects of large rotations.. The GNL three dimensional beam element formulations based on these element approximations are restricted to small nodal rotations between two successive load increments. The element formulation presented here removes such restrictions. This is accomplished by retaining non-linear nodal terms in the definition of the element displacement field, and the consistent derivation of the element properties. The formulation presented here is very general and yet can be made specific by selecting proper non-linear functions representing the effects of nodal rotations. The details of the element properties are presented and discussed. Numerical examples are also presented to demonstrate the behaviour and the accuracy of the elements. A comparison of the results obtained from the present formulation with those available in the literature using a linearized element approximation clearly demonstrate the superiority of the formulation in terms of large load steps, large rotations between two load steps and extremely good convergence characteristics during equilibrium iterations. The displacement approximation of these elements is fully compatible with the isoparametric curved shell elements (with large rotations), and since the elements possess offset capability, these elements can also serve as stiffeners for the curved shells.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620280106
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 95
    Digitale Medien
    Digitale Medien
    Evaluation of boundary integrals for plate bending (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 75-93 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The alternative to quadrature, as a procedure for dealing with the integrations required in the direct boundary element method (DBEM), is to carry out the integration analytically and code the results directly. The potential benefits are efficient computer programs; the avoidance of numerical instability; and generally, better accuracy. The technique is developed in this paper.Serious problems arise when Gauss quadrature is employed for the integration of functions which contain, or are close to singularities. A numerical integration approach may fail at the first stage of the analysis, that is, during the assembly of the discrete equations; or it may fail at the subsequent stage of computing domain points near the boundary. The severity of the problem is dependent both on the strength of the singularity, and on geometry. These points are illustrated with examples.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620280107
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 96
    Digitale Medien
    Digitale Medien
    Frictionless geometrically non-linear contact using quadratic programming (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 127-144 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The successive quadratic programming (SQP) method is used with the finite element method (FEM) to solve frictionless geometrically non-linear contact problems involving large deformations of the elastica in the presence of flat rigid walls. To formulate the SQP problems, the potential energy (PE) is expanded in a Taylor series of second order in displacement increments about a configuration near a contact solution. The SQP problems consist of minimizing the Taylor expansion of the PE subject to the inequality constraints which represent contact. The quadratic programming (QP) method is made part of a Newton-Raphson (NR) search in which the QP corrections are made when a NR step does not satisfy the constraints. A revised simplex method developed by Rusin is used to solve the QP problems. The elastica is modelled with a total Lagrangian FEM developed by Fried. Solutions are obtained for the end loaded buckled elastica in point contact with a rigid wall and for a uniformly loaded elastica in regional contact with a rigid wall. The problems are also solved using a penalty method. The results obtained for the point contact problem are compared to an analytical solution. Calculations were made to obtain numerical information on maximum load step size and the number of inverse operations required for each load step. Cases in which the elastica stiffened substantially as a result of the initiation of contact are also discussed.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620280110
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 97
    Digitale Medien
    Digitale Medien
    The FDM in arbitrary curvilinear co-ordinates - formulation, numerical approach and applications (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 261-277 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The basic concept, formulation and numerical application of a fully automatic version of the finite difference method (FDM) on a two-dimensional manifold embedded in three-dimensional Euclidean space are presented. This version of the FDM was developed in order to enable automatic solution of problems formulated in arbitrary curvilinear co-ordinate systems in terms of covariant derivatives (e.g. shell equations).In the classical version of the FDM all operations in the curvilinear co-ordinates (the derivation of base vectors, curvature tensors and so on) have to be performed manually. The goal of the present work was to transfer this job to a computer, in order to minimize the user's effort during the numerical formulation of the physical problem. The relevant version of the fully automatized program FIDAMF, based on the FDM on arbitrary irregular grids,1,2 has been worked out. This code performs automatically all stages of the numerical analysis, starting from the mesh generation and approximation of the shape of the manifold, through computation of necessary objects on this manifold, to the solution of linear or non-linear problems formulated in terms of covariant derivatives.The method has been extended to the analysis of problems in which the co-ordinate system changes during the computation (e.g. the analysis of large deformations in the convectional description). This version of the curvilinear FDM was applied to the analysis of large deformations of hyperelastic membrane shells.The approach and the numerical routines, although used here with the FDM, can be combined with any other approximation method, in particular the finite element method.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620280203
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 98
    Digitale Medien
    Digitale Medien
    Approximate direct-search minimax circuit optimization (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 359-368 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A direct-search optimization strategy, involving pattern-searches, pattern-moves and a simplex algorithm, has been applied to a number of frequency-domain circuit problems. We show that an approximate minimax result can be obtained with our simple approach, which includes using a modified minimax error function. In the examples attempted, the method comes quite close to the accuracy, if not the efficiency, of true minimax optimizers, and yields an accuracy as good as or better than a least-pth (p = 10) gradient optimizer. The method is broadly appropriate wherever it is difficult or inconvenient to calculate the gradients required for conventional minimax optimization.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620280208
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 99
    Digitale Medien
    Digitale Medien
    Implementation of curvilinear geometry into p-version HT plate elements (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 431-443 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The formulation of the recently presented hybrid-Trefftz (HT) p-version elements1 has thus far been restricted to straight-sided polygonal elements. The present paper removes this limitation. Two alternative formulations are studied. In the first one any curvilinear geometry is represented accurately but the rigid body modes are recovered only in the limit as the p-refinement level is increased. In contrast, the second formulation represents the rigid modes exactly while the actual curvilinear geometry is approached with increasing accuracy as the p-refinement level is increased. The practical efficiency of the two alternative approaches is studied and assessed on pertinent examples of thin plates in bending.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620280212
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 100
    Digitale Medien
    Digitale Medien
    Books received (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 477-478 
    Details
    ISSN: 0029-5981
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/nme.1620280217
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...