My student is working on a polysaccharide hydrogel as pharmaceutical excipient. We want to determine its molecular weight. We are trying to do it by viscosity method, in which we have to determine the intrinsic viscosity and using Mark-Howvink equation, we can go for molecular weight. But, the problem is determination of Mark-Howink constants for this polymer.
hello, you can not use only mark howvink equation .you should use mark howvink equation and "gpc" measurment to determine "K" and "a" .
Sir,
Thank you.
I want to know how to go for 'gpc' measurement to determine 'K' and 'a'. Can you give me any reference or method for it? You may give me a personal mail to [email protected]
I assume that you can make several molecular weights of this polymer. If so, you can measure their molecular weights by light scattering. Once you have three or more molecular weights of this polymer, you can determine their intrinsic viscosity by measuring the viscosity of each molecular weight sample as a function of the samples concentration and extrapolate to zero concentration to obtain the intrinsic viscosity. Then plot the log of the intrinsic viscosity against the log of the molecular weight. The slope of the line will give you the Mark-Houwink. exponent "a" and the intercept will give you "k". If you have a GPC setup hooked up to concentration and light scattering detectors and your polymer is polydisperse, you can obtain Mark-Houwink exponents from software supplied by the manufacturer of the light scattering detector. There are several companies out there that can use that technique to determine the Mark-Houwink constants.
To determine the Mark-Houwink constant log intrinsic viscosity ([h]) is plotted versus log molecular weight (M) of GPC-MALLS. The a-value is the slope of the straight line and log k is the axis intercept. Log [h] = log k + a x log M (Mark-Houwink-Equation)
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