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  • Wiley-Blackwell  (109)
  • 1
    ISSN: 0935-6304
    Keywords: Capillary GC ; Selectivity ; Compound group separation ; Clean-up ; Adsorption of sulfur compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A small amount of mercuric non-porous resin placed in the liner of the injection splitter of a gas chromatograph retains mercaptans but allows other organic sulfur and non-sulfur compounds to be chromatographed normally: mercaptans in the gaseous state are retained by the mercuric resin. The method works well at 200°C but an increasing number of impurity peaks are observed as the temperature is increased to 250°C.
    Additional Material: 4 Ill.
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  • 2
    ISSN: 0935-6304
    Keywords: Liquid - solid disk extraction ; Gas chromatography (GC) ; Phenols ; Supercritical fluid extraction (SFE) ; Water ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method combining the techniques of liquid - solid disk extraction (LSDE) and supercritical fluid elution (SFE) has been developed for the phenols regulated by the Clean Water Act. LSDE uses a disk or membrane made of polytetrafluoroethylene (PTFE) fibrils impregnated with small particles, e.g. styrene divinylbenzene (SDB) resin, to extract phenols from water. After disk extraction the retained analytes are eluted from the disk using SFE. SFE is used as an alternative to liquid solvent elution with an organic solvent. Analytes are separated, identified, and quantified using gas chromatography - ion trap detector mass spectrometry (GC-ITDMS). The method is capable of sub parts per billion detection limits, and precision of 5-28% RSD. Evaluation of various disks or membranes, such as C18-silica disks, SDB disks, and ion exchange membranes, has also been performed for the extraction of phenols from water. The results obtained from the in-situ aqueous acetylation of phenols and extraction of their acetates are quantitative. The utilization of LSDE and SFE techniques has proven to be a more effective approach than liquid - liquid extraction in minimizing air pollution and solvent waste.
    Additional Material: 5 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: HPLC ; Molecular sieve ; Cis-trans isomers ; Phenols ; Selectivity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A molecular sieve known as Silicalite was used as the column packing for HPLC. Silicalite contains channels (or cavities) approximately 6 Å in diameter but, unlike most other molecular sieves, Silicalite is hydrophobic. The retention times of methyl ketones and substituted phenols containing n-alkyl groups increase with increasing chain length of the substituent. However, phenols with very bulky substituents appear to be excluded from the Silicalite channels and elute very quickly. Excellent separations were obtained for a number of compounds with only slight differences in chemical structure. These include phenol isomers with a primary- or secondary alkyl group, position isomers of substituted phenols, and aliphatic cis-trans isomers.
    Additional Material: 10 Ill.
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  • 4
    ISSN: 0935-6304
    Keywords: Capilliary electrophoresis ; Alkanesulfonic acid ; Amino Acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino Acids are cations at low PH and can be readily separated by capillarty electrophoresis provided an alkanesulfonic acid is added to the elecrolyte carrier. Formation of a Positive net charge on the bare fused-silica surface at low PH was confirmed by measurement of an anodic electroosmotic flow. The addition of ethanesulfonic acid or octanesulfonic acid to the electrolyte carrier causes a reversal of the EOF. A mechanism is proposed in which the alkanesulfonic acid adsorbs to the positively-charged capillary wall through electrostatci attraction. Adsorption of a second molecule of alkanesulfonate by hudrophobic attraction to the carbon chain forms a negatively-charge coating on the capillary wall. The alkanesuflfonate also imparts selectivety to the system by participation in ionpairing interactions with the native amino acids to improve resolution. The CE separation of a mixture of the twenty common amino acids at PH 2.8 with direct absorabance detection at 185 nm resulted in 17 amino acid peals in 20 minutes with a 30 KV applied voltage. The effect of several variables was studied including electrolyte carrieres containing different alkanesulfonic acids, the influence of PH, applied voltage, and concentration of electrolyte carrier.
    Additional Material: 10 Ill.
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  • 5
    ISSN: 0935-6304
    Keywords: Capillary GC ; Selectivity ; Compound group separation ; Clean-up ; Adsorption of basic compounds ; Sulfonated resin ; Quantitation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A small amount of a lightly sulfonated non-porous resin placed in the liner of the injection splitter of a gas chromatograph retains basic organic compounds but allows neutral compounds to be chromatographed normally. The organic bases in the gaseous state react with sulfonic acid groups on the resin surface to form protonated ions. Abstraction of bases is complete at a base: neutral molar ratio as high as 200:1 and a large number of samples can be injected before the sulfonated resins need to be replaced.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 7
    ISSN: 0935-6304
    Keywords: Electrophoretic capillary chromatography ; Organic modifiers ; Hydrophobic association ; Capacity factors ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Very good separations of non-ionic organic compounds have been achieved by capillary zone electrophoresis (CZE) using a tetrahep-tylammonium salt as an additive in aqueous acetonitrile as solvent. A systematic study was undertaken to determine the effect of experimental parameters on electroosmotic mobility and electro-phoretic mobility. It was found that pH, acetonitrile concentration, and the type and concentration of quaternary ammonium salt are important experimental variables. Under appropriate conditions, the separation window was enlarged and a broad range of electrically neutral organics, including very hydrophobic compounds (e. g. poly-cyclic aromatic hydrocarbons) and fairly hydrophilic compounds were separated in a relatively short time. By adjusting the separation conditions, high resolution CZE of a specific group of neutral organic compounds could be achieved. A method for calculation of capacity factor was proposed and capacity factors for a variety of non-lonic organic compounds were calculated.
    Additional Material: 10 Ill.
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  • 8
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; CTAB ; Dipeptides ; Enkephalins ; Proteins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Incorporation of a low concentration of cetyltrimethylammonium bromide (CTAB) in the running electrolyte is shown to dynamically coat the silica capillary and to reverse the direction of electroosmotic flow. The CTAB coating prevented interaction of proteins with the capillary surface and enabled sharp peaks to be obtained in the electropherograms. A systematic study of experimental parameters demonstrated the importance of selecting a suitable buffer electrolyte and an appropriate pH. Excellent separations were obtained for five proteins, three enkephalins, and six dipeptides with an efficiency of approximately 500,000 theoretical plates per meter. The method developed is very simple to perform and was found to give excellent reproducibility.
    Additional Material: 9 Ill.
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  • 9
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Metal cations ; Acid solution ; UV detection, direct and indirect ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methods for the detectionn of metal cations under acidic conditions, near PH 2, in capillary electrophoresis (CE) were investigatged. Conditions for direct UV detection of UV absorbing metal cations such as Cr3+, Cu2+, Fe3+, UO22+, VO2+, and VO2+ were established With aqueous HCl or HClO4 as the electroyte carrier. The speciation of vanadium(IV) and vanadium(V) at PH 2.3 by CE was achieved with direct detection at 185 nm. With the strong absorbance at 185 nm, no complexation was needed to detect the metal cations. An indirect UV detrection scheme for acidic conditions was also investigated. Several background carrier electolytes (BCES) were studied including 4-methylbenzylamince, nicontinamide, pyridazine, guanidine, 3-picoline, and chromium (III) to determine their effectivencess under very acidic conditions. The efect of ioni c surfactants and the nonionic surfactant, Trition X-100, on the peak heights and N Values was also studied.
    Additional Material: 4 Ill.
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  • 10
    ISSN: 0886-1544
    Keywords: inhibition of cell motility and proliferation by interferon-β ; interferon-β increases stationary time in fibroblasts ; interferon-β decreases translocation rate in fibroblasts ; fibroblast motility in culture ; cell motility: translocation rate and stationary time ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The rate of translocation and the percent of the time that cells are stationary have been measured by computer-assisted time-lapse cinemicrography in over 1,000 freshly planted human foreskin fibroblasts (FS-4 cell strain) for periods of up to a week and the effects of interferon-β (IFN-β) on these parameters have been determined. Cells were planted at 2.5 × 103 cells/cm2 in Eagle's minimal essential-medium (MEM) with 10% fetal bovine serum (FBS). Frames were taken every 2 or 4 minutes and data were collected on both cell location and cell division as a function of time. After planting FS-4 cells require ∼48 hr to reach maximum motility both with respect to the translocation rate when moving and percent time cells are moving. Recombinant human IFN-β (800 μ/ml) caused a marked increase in the fraction of time cells were stationary and a decrease of lesser magnitude in the translocation rate, as quantitated during the period during which the stationary fraction for control cells was at a minimum. IFN-β also decreased the rate of cell proliferation, without any evidence of degeneration or death of cells. Our results contribute new evidence that the fraction of time cells spend moving directionally is an important determinant of their locomotory behavior and that this determinant is responsive to modulation by cytokines.
    Additional Material: 12 Ill.
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