How did you measure the OD of the RNA? If you add "pure" RNA to water the 260/280 OD ratio will be lower (1.7-1.8), but if you add "pure" RNA to 10 mM Tris pH 7.4 the OD ratio will be 2.0-2.1.

260/280 ratio is variable from tissue to tissue. Additionally you will get different ratios with different RNA extraction methods. If possible check the RNA curve in nanodrop.

Thank you all, I extracted RNA from liver tissue and some I got 1.7, hope to work with me.

How did you measure the OD of the RNA? If you add "pure" RNA to water the 260/280 OD ratio will be lower (1.7-1.8), but if you add "pure" RNA to 10 mM Tris pH 7.4 the OD ratio will be 2.0-2.1.

Oh, I added it to water, then should be OK

Thank you