Chromatography molecular weight averages

ASTM D 5296 - 92 (1994). Standard Test Method for Molecular Weight Averages and Moleeular Weight Distribution of Polystyrene by High Performance Size-Exclusion Chromatography. Annual Book of ASTM Standards, Vol.08.03, pp. 419-431. 

ASTM D-3536-91, Standard Test Method for Molecular Weight Averages and Molecular Weight Distribution by Liquid Exclusion Chromatography (Gel Permeation Chromatography-GPC), ASTM Annual Books of ASTM Standards, Vol. 08.02, P. 349—359. This method was deleted in the 1997 edition of the ASTM book. 

Ordinate values of the molecular weight distribution rather than molecular weight averages obtained from size exclusion chromatography were used in the modelling (3.9). [Pn] in Equation (1) can be transformed into (log M), the ordinate of the molecular weight distribution using (2) ... 

Specialty calculations for gel permeation chromatography (GPC) where the integrator would calculate the molecular weight distribution, molecular weight average, and polynomial curves for calibration. 

The major factor influencing the thermal and mechanical properties is the composition differences between the polymers. Gel permeation chromatography measurements have shown that the molecular weight averages and molecular weight distributions are not significantly different for the samples which have been studied and are therefore not seen as important as far as Tg and mechanical measurements are concerned. 

The data for the molecular weight averages, and Mq, obtained by gel permeation chromatography for the samples of polystyrene and poly(methyl methacrylate) are shown In Table I and II, respectively. Although the values are not absolute, they provide the ability to study the molecular weight development In the emulsion polymerization of these monomers In a relative sense. Figures 5 and 6 provide graphical representation for the data. 

A combination of liquid adsorption chromatography with SEC has recently been developed by several workers. Poly(styrene-methyl methacrylate) copolymers were fractionated according to chemical composition by liquid adsorption chromatography and the molecular weight averages of each fraction were measured by SEC [5,6]. 

ASTM D-3593 Test Method for Molecular Weight Averages/Distribu-tion of Certain Polymers by Liquid Size Exclusion (Gel Permeation) Chromatography—GPC Using Universal Calibration (has also been adapted to the investigation of molecular weight distribution in petroleum fractions). 

Figure 7.17. Gel-permeation chromatography (GPC) analysis of a polystyrene foam sample using UV detection. Annotations are calculated molecular weight averages and polydispersity.

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