ISSN:
1022-1352
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
An iterative, approximative procedure is presented, to calibrate the determination of molar masses of polymers with gel-permeation chromatography, additionally using viscometry, and transformations, according to Benoit's concept of universal calibration, even if only polymers with broad molar mass distribution are available. The calculated (intermediate) values of the average molar masses from each step of iteration converge to final values. With at least two fractions of the polymers to be analyzed, and with measured intrinsic viscosities of the fractions, a calibration curve of gel-permeation chromatography and Mark-Houwink's constants can be determined. Assumptions for the use of the calibration procedure are the existence of linear calibration curves for gel-permeation chromatography, constant Mark-Houwink's exponents, and a common universal calibration curve according to Benoit, of the polymers of interest, and of another polymer for comparison. From this second polymer the Mark-Houwink equation must be known (or measurable with acceptable expense), and sufficient uniform fractions for chromatography must be available. In aqueous saline the assumptions are fulfilled by hyperpolymers of human haemoglobin, and by native proteins, as shown in a previous paper. The new procedure was applied to fractions of those hyperpolymers, it was evaluated, and variants of the procedure were compared. The evaluation was done by comparison of the number-and mass-averages of the molar masses of the fractions of haemoglobin hyperpolymers, determined with gel-permeation chromatography calibrated with the new procedure, with the values obtained from osmometry and light scattering. The goodness of the new procedure, especially the power of correction of molar masses, can be demonstrated with the application to fractions of haemoglobin hyperpolymers, it changes with their uniformity. Furthermore, the new procedure shows its efficiency, when three steps of iteration are enough to reach the final values. At last, with a Benoit transformation of the averages of molar masses, obtained by a theoretical consideration within the given marginal conditions, a rectification of the new procedure is given.
Zusätzliches Material:
7 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/macp.1996.021971014
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