Norgen Biotek has developed various products (Plasma/Serum Circulating RNA Purification Kits and Exosome RNA Purification Kits) that are specifically optimized for purifying circulating or exosomal RNA (large RNA and microRNA) from plasma/serum or urine with the following advantages:

Simple and Fast Procedure with no lengthy phenol:chloroform extraction, filtration or precipitation

Scalable Purification of RNA from 50 µL to 5 mL of plasma/serum and 1 mL to 10 mL of urine

High Yield, High Quality and Inhibitor-Free RNA isolated from all types of plasma, serum or urine

http://www.nature.com/app_notes/nmeth/2012/121311/full/an8749