This procedure is complicated by the ubiquitous presence of ribonuclease enzymes in cells and tissues, which can rapidly degrade RNA.
[1] Several methods are used in molecular biology to isolate RNA from samples, the most common of these is guanidinium thiocyanate-phenol-chloroform extraction.
[4] RNA extraction in liquid nitrogen, commonly using a mortar and pestle (or specialized steel devices known as tissue pulverizers) is also useful in preventing ribonuclease activity.
Broad RNAse inhibitors are also commercially available and sometimes added to in vitro transcription (RNA synthesis) reactions.
Two-phase wash to solve the ubiquitous contaminant-carryover problem in commercial nucleic-acid extraction kits; by Erik Jue, Daan Witters & Rustem F. Ismagilov; Nature, Scientific reports, 2020.