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Die bestimmung des molekulargewichts aus zwei punkten und dem maximum der gradientenkurve der ultrazentrifuge

1960; Elsevier BV; Volume: 45; Linguagem: Inglês

10.1016/0006-3002(60)91446-3

1878-2434

Rainer Jaenicke, Matatiahu Gehatia,

Adsorption, diffusion, and thermodynamic properties of materials

Abstract The determination of the molecular weight from two points and the maximum of the ultracentrifugal gradient curve The theory of Brownian motion in the centrifugal field, derived previously, provides a new method, the “Zweipunkt-Methode”, (2PM), for the determination of the sedimentation coefficient s as well as the diffusion coefficient D from the maximal gradient and two points of a single experimental gradient curve obtained by means of the usual optical systems of the ultracentrifuge. The experimental conditions and the verification of this method are discussed for three various substances with molecular weights between 20,000 and 150,000. The obtained results in case of these substances are in good agreement with the data given in the literature. The mean error of the values of s and D for medium molecular weights (∼ 100,000), obtained at optimal conditions of experiment and evaluation, was 1 to 3%, i.e. only one third of the error in the case of the three-points-method mentioned in a previous paper. For small molecular weights the mean error does not exceed 8%. The variations of s/D are less than 5% for medium molecular weights, for small ones they approach 20% as a maximum. Comparing the various former methods with the 2PM it seems that the 2PM has some advantages in the case of ideal systems of homogeneous particles; on the other hand the 2PM seems to be suitable to detect qualitatively the heterogeneity of strong polydisperse systems.