High A260/A280 ratio for RNA - Is there a contamination? (Mar/23/2001 )

when quantitating RNA, we are finding that our A260/A280 ratio is often around 2.2. I know that ideally it should be 2.0, but what does it mean when the ratio is higher? Does it indicate a contamination in the sample?

Yes, probably the RNA is contaminated by phenol.

Good luckMonica

Michelle,

When purifying RNA produced from an in vitro transcription reaction I would routinely get 260/280 ratios in the 2.1-2.5. Range. The purification method was a little Qiagen Viral RNA spin column kit...no Phenol was used. Take home message is....highly pure RNA will give you a high ratio.

You may also want to take an A320 reading to get a feel for any background contamenation.

More importantly how does you RNA work in the downstream application?

Mark