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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 15 (1982), S. 426-432 
    ISSN: 1612-1112
    Keywords: Polymer analysis ; Molecular weight distribution ; Steric exclusion chromatography ; Field-flow fractionation ; Light scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The classical method for the determination of the molecular weight distribution (MWD) curve of a polymer requires fractionation according to the molecular weight and prior calibration of the separator. It is shown that the use of a dual detection system which includes a molecular mass sensitive detector eliminates the need for prior calibration. The principles of operation of a low-angle light scattering photometer, working as such a detector, are presented, as well as the basic equations for determination of the MWD curve from the elution curve and of the average molecular weights. Then the performances of the light scattering photometer are discussed with special emphasis on the various sources of errors and unaccuracies in these determinations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 34 (1992), S. 325-330 
    ISSN: 1612-1112
    Keywords: Field-flow fractionation ; Secondary chemical equilibria ; Colloidal systems ; Retention theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The application range of field-flow fractionation (FFF) can be extended to low molecular weight solutes, as demonstrated a few years ago by Berthod et al., by taking profit of secondary chemical equilibria (SCE) occurring between the bulk carrier and a retained carrier component. The theory of solute retention in this SCE-FFF method is developed for any value of the solute distribution coefficient and of the retention ratio of the retained carrier component, provided that the Brownian mode of retention applies for this component and that the flow velocity profile is parabolic. This removes some of the limitations of the model previously developed by Berthod and Armstrong and sheds light on the potentialities of the SCE-FFF method for physico-chemical studies about secondary chemical equilibria in colloidal systems. Remaining assumptions in the model are discussed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1612-1112
    Keywords: Field-flow fractionation ; Three-dimensional flow velocity profile ; Rectangular cross-section channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The shape of the velocity profile established in a carrier liquid flowing in a duct of rectangular cross-section under conditions of isoviscous flow is well known and can be calculated by using an approximate or the exact solution of Navier-Stokes equation. The series evaluated when applying the exact solution were found to converge very rapidly. Consequently, computing can be substantially shortened without loss of accuracy by summing only the first three terms of the series. A fair agreement between the approximate solution of Takahashi and Gill and the exact solution was obtained for all practically applicable aspect ratios of the separation channels used in field-flow fractionation. This conclusion is of interest when calculating various separation parameters in three-dimensional channels for field-flow fractionation.
    Type of Medium: Electronic Resource
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