SynopsisAn iteration method has been developed to prepare a calibration curve for gel permeation chromatography (GPC). It requires a number of samples of the same polymer which may have broad molecular weight distributions (MWD) of which two molecular weight averages must be known previously. The method has been applied to dextran standards with known and an. Modifi-cations involving the use of branched polymers are discussed.

The determination of averages of diffusion coefficients and among others, from them, the number‐average molecular weight, becomes possible after reformulation of Sundelöf's method of processing of free diffusion data. An index of heterogeneity may be calculated too.

SAMENVATT I NGEen a a n t a l dextranen (Pharmacia) met bekende molecuulgewichten M gedraagt z i c h , b l i j k e n s een gecombineerd v i s c o s i m e t r i e -en GPC-onderzoek aan oplossingen i n water (30 O C ) , a l s een homologe reeks, ook opzichtens vertakking, met welbepaalde GPC-ijkfuncties betrokken op M dan we1 h e r v i s c o s i t e i t s g e t a l [I)]. U i t deze f u n c t i e s werd een V O O K d i s p e r s i e gecorrigeerde Mark-Houwinkbetrekking a f g e l e i d : [I)] = 7,53. 10-2*M0~523 (ml/g) voor l o 4 5 M 5 l o 5 ; i n h e t hoogmoleculaire geb i e d d a a l t de exponent t o t 0 , 3 4 . Verwerking van k l a s s i e k e d i f f u s i e m e t i n g e n , volgens SundelEf, maakt bepaling e n e r reeks diffusieco6fficigntgemiddelden Bp, p > -1, u i t de d e v i a t i e f u n c t i e mogel i j k , n a a s t de gereduceerde oppervlakte-hoogteverhouding DA. Langs numerieke weg kan m e t hen, de chromatogramen en de i ' k f u n c t i e op M een voor d i s p e r s i e gecorrigeerd D,M-verband a f g e l e i d worden: D = 8 , 8 4 . 1 0 -~. M -~* '~~ (cm2/s) voor l o 4 < M < lo5. Beschikbaarheid van aantalgemiddelde Mwaarden maakt d e s z e l f s o p s t e l l i n g mogelijk b -4, from the devi a t i o n f u n c t i o n , and, moreover, of t h e reduced height-area r a t i o DA , Using the chromatograms, the M-based c a l i b r a t i o n curve and t h e s e D-averages, we c o r r e c t e d t h e D,M-relation f o r d i s p e r si o n : D = 8 . 8 4 . 1 0 -~. K~*~' 6 ( c m 2 / s ) , f o r lo4 5 M 5 lo5. With t h e number-averaged M v a l u e s a t o n e ' s d i s p o s a l , the use of GPC may be circumvented i n t h e c a l c u l a t i o n of the r e l a t i o n . From t h i s and the d e v i a t i o n f u n c t i o n s e v e r a l averages of M r e s u l t e d , being reasonably i n accordance w i t h t h e GPC values. The r a t i o of r a d i i , r,.,/yf, c a l c u l a t e d from M, very c l o s e...

The role of the intrinsic viscosity [η] as separation parameter in gel permeation chromatography (GPC) was studied for dextrans (from Leuconostoc mesenteroids B512) dissolved in water with deactivated silicagel (Porasil) as the column‐filling material. For that purpose specific viscosities of dextran fractions eluted by GPC were measured as a function of the elution volume v. Provided that the elution volumes are corrected for zonal spreading, they are related to the intrinsic viscosities in an unambiguous way, probably reflecting a unique relationship between degree of branching and molecular weights. This was further investigated by developing an iteration method to prepare two calibration curves γ(v) and g(v), respectively, relating ln[\documentclass{article}\pagestyle{empty}\begin{document}$\left[ {\bar \eta } \right]$\end {document}] and InM (M is the molecular weight) to v. It required that the weight‐average molecular weight Mw, the number‐average molecular weight Mn, and the average intrinsic viscosity [\documentclass{article}\pagestyle{empty}\begin{document}$\left[ {\bar \eta } \right]$\end {document}] for a number of dextran samples (broad distributions) be previously known. The calibration curves found lead to consistent values of the above‐mentioned averages. Moreover, they allow‐establishment of the [\documentclass{article}\pagestyle{empty}\begin{document}$\left[ {\bar \eta } \right]$\end {document}]‐M relationship over the range 5000 < M < 500,000.