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  • 1
    ISSN: 0935-6304
    Keywords: GC/MS ; Capillary columns, fused silica ; Priority pollutants ; Quantitation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Operational characteristics have been determined for fused silica capillary column (FSCC) GC/MS as applied to “extractable” priority polutants. Chromatographic data show excellent relative retention time (RRT) intralaboratory precision and interlaboratory accuracy when multiple internal standards are empolyed. Potential chromatographic problems, such as column overload and “double peaking”, are addressed. Response factor relative standard deviations (RSD) at 50 ng for most of the extractable priority pollutants over the long term indicated precise determination (i.e. RSD generally ≤ 10%). Linearity was demonstrated over two orders of magnitude for FSCC GC/MS analysis of compounds with relatively low and high RF (response factor) values. Potential quantitative problems, such as saturation, are discussed. For certain aromatic priority pollutants interlaboratory RF agreement was observed. This was noted as perhaps the most important property of FSCC GC/MS analysis when the multiple internal standard approach is utilized. Determinations of extractable priority pollutants are directly compared for paced column GC/MS and FSCC GC/MS analysis of separate and composited extracts. For six extracts analyzed in triplicate, the latter configuration was shown to produce more consistent results. In view of the superior analysis logistics of composite extract FSCC GC/MS analysis, this approach was established as the preferred method for the analysis of priority pollutants classified as extractable.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Liquid crystal ; N,Ń, Bis (p-phenylbenzylidene)-α, α′-bi-p-toluidine (BPhBT) ; Steroids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A gas-chromatographic separation of underivatized steroids is described, in which the liquid crystal N,Ń-bis(p-phenylbenzylidene)α,α′-bi-p-toluidine (BPhBT) was used isothermally at 265°C for the stationary phase. The nematic range of this crystal is 247 to 403°C. Use of the BPhBT crystal allowed operations in a temperature range where steroids are volatile and unlikely to display broad elution peaks and long retention times.With columns precoated with 2.5 weight percent of BPhBT, steroids containing minor structural differences in the ring system were readily differentiated. For example, 5-androsten-17α-ethinyl-3β, 17β-diol was found to elute more rapidly than its 3-keto analog, ethisterone. Ethisterone was distinguished readily also from its 19-nor analog, norethisterone. Additionally, differences in side-chain functionality and resultant molecular dimensions facilitated the separation of steroids of identical ring structure, as in the comparison of cholesterol with methyl 3β-hydroxy-5-cholenate and 25-hydroxycholesterol.An enhancement of separation according to the molecular length-to-breadth ratio was observed; in general, the larger this length-to-breadth ratio, the greater the retention period on the column.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0935-6304
    Keywords: HPLC ; Reverse-phase ; UV detection ; Fluorescence detection ; Polycyclic aromatic hydrocarbons ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modern liquid chromatographic (LC) conditions which effect a separation of polycyclic aromatic hydrocarbons (PAH) containing up to ten rings are described. The LC conditions include reverse-phase chromatographic columns in combination with a quaternary solvent system. Methanol and water are combined to form solvent system A, while tetrahydrofuran and acetonitrile form solvent system B. Solvent systems A and B are then combined in a linear gradient relationship to effect the separation. The separation of benzo(a)pyrene and perylene along with benzo(ghi)perylene and indeno (1,2,3-cd)pyrene is achieved. In the same chromatogram the PAHs, coronene, dibenzo(a,e), (a,i), (a,h)pyrene and tribenzo(a,e,i)pyrene are also separated. An increase in column temperature from 45°C to 55°C is shown to shorten the elution time and increase chromatographic resolution of many of the PAHs examined. At least 25 PAHs ranging in molecular weight from 178 to 536 are examined for their chromatographic behavior. As examples, the application of this method to samples from a coal liquefication process are included. The samples are examined with both a UV detector and fluouescence detector to demonstrate the utility of dual detectors when analyzing for PAHs in complex matrices. With minor modification of the gradient this method is applicable to PAHs containing ring systems other than those reported here.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1426-1430 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This study focuses on the effect of various processing and cooling conditions upon the subsequent melting and solidification behavior of blends of poly(butylene terephthalate) (PBT) and high density polyethylene (HDPE). Differential scanning calorimetry (DSC) measurements have shown that the crystallization of reprocessed PBT is different from the crystallization behavior of virgin samples. Two melting endotherms for PBT were observed for reprocessed PBT and for PBT-PE blends. The nature of each PBT peak is discussed in relation to processing history, solidification conditions, and composition. The presence of two crystallization peaks for the PE component in blends of PE and PBT are thought to be associated with the restriction of molecular motion of PE in the presence of the second component. The relative magnitudes of the two exotherms of PE vary with composition and cooling rate during solidification.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The differential (incremental) storage modulus E′ was measured intermittently at 1 Hz during the stress relaxation of cylindrical specimens of polycarbonate subjected to finite static strains in both simple compression and extension. (In measuring E′, the amplitude of the applied sinusoidal strain was 0.2%.) Application of each static strain gave a value of E′/E′0 less than unity, where E′0 is the storage modulus at 1 Hz of the undeformed specimen. This behavior results from an increase in the mobility of short molecular segments; it signifies a partial erasure of the state of physical aging, a change also termed de-aging or rejuvenation. After a static strain had been applied, E′ increased continuously, a reflection of physical aging that results from a progressive decrease in segmental mobility. Plots of E′/E′0 at an aging time of 100 s against the absolute value of the static strain show that simple extension de-ages a specimen somewhat more than does a strain of the same magnitude in compression. This difference results from the increase or decrease in volume (or free volume) effected by strains in extension or compression, respectively. The dominant cause of de-aging, however, is the deviatoric (shear) component of the strain tensor. The increase or decrease in volume produced by an applied strain modifies only slightly the segmental mobility.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The compatibility of polymer blends of poly(∊-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN) containing various acrylonitrile (AN) contents was studied to evaluate the influences of copolymer composition and PCL concentration upon blend compatibility. Blend compatibility was characterized by the occurence of a single glass transition intermediate between the transitions of the respective pure components. The glass transitions were determined by differential scanning calorimetry (DSC) and dynamic mechanical measurement (Rheovibron). It was found that SAN and PCL form compatible blends when the AN content of SAN ranges from 8% to 28% by weight. These blends are compatible in all proportions except for SAN 28 (AN wt % = 28) and PCL blends containing 70 or 85 wt % PCL. Blends of PCL and SAN were found to be incompatible when the AN content in SAN is greater than 30 wt % or less than 6 wt %. Lower critical solution temperature (LCST) behavior, which can be attributed to phase separation, was found to occur when these blends were heated to elevated temperatures. The cloud point, or phase separation, was found to vary with AN content in SAN and the concentration of SAN in the blend.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0076-2083
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 72 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 37-41 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experiments are reported in which the drag of single liquid droplets settling in a tall column of another lighter immiscible liquid are measured. The experimental data for the eight pairs of liquids that were tested covered a range of droplet Reynolds numbers from 10-3 to 104. Two regimes of droplet settling were encountered. In the first regime, the droplets remained spherical, and the drag agreed very well with established solid sphere drag models. In the second regime, the droplets became deformed and oscillated; the drag was found to depart suddenly from predictions of spherical models and to increase with increasing Reynolds number. Empirical models for the point of departure from spherical drag and the coefficient of drag in the unstable regime are derived.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A computer program, used to ‘curve-fit’ complex spectra of overlapping peaks in other spectral applications, has been used with X-ray fluorescence data. Compensation is made for analytical error introduced through peak overlap. A typical case of this ‘inter-element interference’, that of titanium upon vanadium, is taken to demonstrate the method. A comparison between the computer-generated results and those determined by the conventional inter-element correction method favours the curve-fitting procedure.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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