formaldehyde gel for RNA

[Wong Yong Wee]

Dear netter,

I'd tried to run my RNA sample on formaldehyde agarose as protocol on
Molecular cloning by Sambrook several times, but I get smear bands for
samples and marker and failed to get two distinct band for 28S and 18S as
expected. I'd eliminated the possibility of RNase contamination. Is these
caused by quality of formaldehyde or pH?  Can I have references for these
problem? 

Thanks in advance.  
Jason