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Absurdly high A260/280 ratio for RNA - (Jun/02/2013 )

Today I isolated RNA from 16 samples and quantified the RNA using spectrophotometers.
15 of the samples had A260/280 ratio between 1.9 and 3.5. I think the range was still acceptable although 3.5 is actually quite high.
But...the remaining one sample had an A260/280 ratio of about 30!
I checked with 2 spectrophotometers and both gave me the same reading.
What does this absurdly high A260/280 ratio mean?

-jamestoon1-

What method did you use for the extraction? An abnormally high A260 reading could be an indication of Phenol contamination, giving you the unusually high A260/A280 ratio.

-Yissue-

Yissue on Mon Jun 3 02:51:00 2013 said:


What method did you use for the extraction? An abnormally high A260 reading could be an indication of Phenol contamination, giving you the unusually high A260/A280 ratio.

I used RNeasy.
I wonder how that particular sample become contaminated with phenol when the other 15 were fine.
And I was told that RNeasy spin columns could effectively remove phenol.

-jamestoon1-