MW determination using SAXS

[akshayc]

I am trying to calculate molecular weight using absolute calibration however I got stuck on determining partial specific volume.
It is polydispersed nanoparticle suspension with ambiguity in polymorphic phase of the nanoparticle.
As per my understanding when we do not know the density of the nanoparticle material the method of partial specific volume is used.
I measured the density of the suspension at different concentrations.

I have used the formula mentioned in the following article
(Reference: E. Mylonas and D. Svergun, J. Appl. Cryst. (2007). 40, s245–s249 is attached)

But I am getting absurd number.
What should be the typical values of vapp for nanoparticle? I suppose it should be positive number less than 1.
Also can vapp be used for the density of material as it will be required for calculation of e- moles/cm3?

Kindly help me to resolve this.

Thanks
Akshay