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Size exclusion chromatography (SEC) is used to determine the molar mass distribution of polymers
SEC is not an absolute method
It requires calibration
Narrow molar mass fractions of atactic polystyrene are commonly used for calibration
The time for a given molecular species to flow through the column is dependent on the hydrodynamic volume of the molecule
It has been shown that the hydrodynamic volume is proportional to the product of the intrinsic viscosity [η ] and the molar mass M
The Mark-Houwink equation relates the two quantities according to:MK][where K and α are constants unique for a given combination of polymer, solvent and temperature
Derive the relationship between the molar masses of the polymer studied and of atactic polystyrene for a given eluation time
解:At e