I am doing RNA extractions on plant roots which I plan to grind in liquid N prior to extraction. For my purposes, I want to precisely know the dry mass of the tissue that I extract, which means that I also need to determine the percent moisture of my samples. I don't have very much tissue, so I would like to do the moisture determination on a pretty small subsample of the ground root mass (~100-200 mg if possible). Does anyone have recommendations for how to do this? I am not sure which container will be best, perhaps a pre-weighed 1.5 mL eppendorf?