relative SEC and hydrodynamic volume


I have been analyzing some polymers with a more polar solvent on SEC - ELSD detection. (relative to Polystyrene)

Where I normally measure a MW of 30K for PLA (relative to Polystyrene) in chloroform, I now measure a MW of 140K. 

In other words, in this polar solvent, the PLA has a bigger hydrodynamic volume, right?

If the solvent surrounds the polymer more, and this causes a bigger hydrodynamic volume, would the analysis then be incorrect?

Let me know what you think,


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