The exact composition of Buffer RW1 is confidential. Buffer RW1 is a proprietary component of RNeasy Kits. Buffer RW1 contains a guanidine salt, as well as ethanol, and is used as a stringent washing buffer that efficiently removes biomolecules such as carbohydrates, proteins, fatty acids etc., that are non-specifically bound to the silica membrane. At the same time, RNA molecules larger than 200 bases remain bound to the column.
Note: Buffer RW1 should not be used for isolation of small RNAs, for example, microRNAs or fragmented RNA from formalin-fixed tissues, as these smaller fragments will be washed away. Buffer RWT should be used instead.