Hello! To solve this problem you need to use a coefficient of " shrinkage " - ie, compare the wet and dry weight of the tissue fragment . It is better to build a calibration curve (5-10 points ) , which evaluates these changes in fragments of different masses , for example , 25 , 50, 75, 100 mg , etc. Unfortunately , there is no data at hand for the liver of rodents , but for embryos and placentas it makes 0,16-0,18 , respectively.

Thanks for answer Svetlana,

But how can we build a calibration curve? I have lot of data ie, different concentration of heavy metals in different tissues, how can i change them? Can you explain again with examples? 

Thank you so much