Hi all, I use a TRIZOL and chloroform-based protocol for RNA extraction from rodent brain samples.

For these samples, after collecting the aqueous phase, I added half-volume isopropyl alcohol and centrifuged for 10 min after 10 minutes on ice. Then I removed the supernatant and washed it with 1 mL 75% ethanol. Since, RNA could be stored for months in 75% ethanol at -20°c, I stopped at this step and stored the samples at -20°c. Now, 2 days later, I started again by centrifuging my samples at 12,000 × g for 5 minutes at 4°C, but I don't see any pellets. Usually at this step, the pellet is pretty visible.

Any suggestions on what happened and how to fix it is greatly appreciated.