Optimization of the ethanol precipitation of RNA from formamide containing solutions.

This study shows that high variability and low recoveries are obtained when conventional ethanol precipitation is used to recover RNA from the 70%-90% formamide containing solutions that are used to elute poly(U) Sepharose columns. Precipitations of RNA at different formamide concentrations show that the variability of the recovery increases with increasing formamide concentration and the recovery decreases by 7% for each 10% increase in the formamide concentration. The formamide concentration curve shows that these factors can be optimized by diluting the formamide containing solutions at least to 30% formamide prior to the precipitation.