RNA extraction from snap frozen lung - (May/12/2004 )

I have extracted RNA from snap frozen lung using Trizol and while the UV spectrometry resuts are favourable the RNA gel is smeared. I use a mortar and pestle to grind the tissue in the Trizol but it takes upto 30 min.Is this too long for homogenization or is it ok as it is in Trizol? Is the RNA degraded or is it DNA contamination?

Any assistence would be welcome.

Beware of RNase contamination instead of DNA contamination. 30' won't be a problem. Do you use liquid nitrogen when doing homogenization?

No i haven't been using Liquid Nitrogen but I think that it clearly is the best way.