Hi Neelofar,

The pH of phenol is around 4.5 to 5 .....and it is used for isolation of RNA os RNA because at this pH...DNA due to its charge properties remains in the organic phase and RNA comes out in aqueous phase.....if the pH of the phenol goes above 5 or like 7.5 to 8....as in case of DNA isolation....then DNA will start coming into aqueous phase....and will contaminte the RNA preparation...this is the reason you have to maintain pH of phenol between 4.5 to 5.0

bye

thanks. I read somewhere (Sambrook or T A Brown) dat phenol dissolves mRNA, no other detail was given. so dat means there should be a pH at which RNA also remains in organic phase

A detailed explanation available at below link...

https://biology.stackexchange.com/questions/56432/rna-isolation-role-of-ph