Acid guanidinium thiocyanate-phenol-chloroform extraction

This method may take longer than a column-based system such as the silica-based purification, but has higher purity and the advantage of high recovery of RNA.

It was originally devised by Piotr Chomczynski and Nicoletta Sacchi, who published their protocol in 1987.

Guanidinium thiocyanate, a chaotropic agent, is added to the organic phase to aid in the denaturation of proteins (such as those that strongly bind nucleic acids or those that degrade RNA).

The 2-propanol is then washed with ethanol and the pellet briefly air-dried and dissolved in TE buffer or RNAse free water.

The major downside is that phenol and chloroform are both hazardous and inconvenient materials, and the extraction is often laborious, so in recent years many companies now offer alternative ways to isolate RNA.