does RNA conc increase after freezing

[shohag]

I extracted RNa from my smaple and then used nanodrop to measure their conc and OD.I got
sample 1- 254.9ng/microL and 260/280- 2.09
sample2-211.7ng/microlitre and 260/280- 2.09
and then I froze them at -80deg for 2days.
After 2 days I measured again and the conc was
sample 1-313.4ng/microlitre and 260/280 -2.08
sample 2 - 305.8ng/microlitre and 260/280 - 2.07
what was the problem?
I used nanodrop1000

[Pijl]

Maybe the RNA was not completely dissolved when you measured it for the first time? If you overdry the pellet, it may be hard to dissolve.

Cheers
Dennis

[cathbr]

If you obtain different values when you measure your samples in triplicates the same day, the problem comes probably from the nanodrop. If you don't, then I would believe that your problem comes from RNA dissolution (as Pijl proposed).
best