The orcinol method has worked for me in determining the RNA content of
mammalian cells. A 1 ml sample ( in my case a HCLO4 RNA precipitate )
was pipetted into a glas tube large enough and strong enough to stand the
rest of the protocol. To this 3 ml of the orcinol mixture was added ( 4
parts 90 mg FeCl3.6H2O in 100 ml HCL and 1 part 1gr orcinol in 100 ml H2O
). This mixture is heated to 100 C for 20 minutes, then cooled with tap
water. 8 to 10 ml of butanol is added and the A672 nm is read.
You can use ribose as a standard, then you have to time the 20 minutes at
100 C exactly, if you use RNA as a standard this isn't as critical.
As the method is based on a reaction with the sugar other sugars may
A good reference is Methods in microbiology part 5B, Eds Norris,J.R.;
Ribbons, D.W. Acad.Press. '71 London, New York.