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purity of genomic DNA, low 260/230? - (Oct/29/2009 )

Hi, i isolated some mouse genomic DNA (600ul) using qiagen mini blood kit. I eluted the dna into water, but it looks slight yellowish. I'm not sure why but i continue to use the eluate to perform ethanol precipitation to concentrate the DNA.

Although the kit mentions that from 200ul blood you should get at least 2ug of DNA, i got only approximately 2ug from 600ul of blood.

Anyways, after dissolving the pellet in water, I nanodrop it and the 260/280 ratio is 1.8, the the 260/230 ratio is only 1.2. I wonder if that is a bit too low and if so, does anyone know why thats happening? I read online that the low 260/230 can be due to contaminating organic solvent like phenol, but i did not use any of those reagents. But one thing i noted is that the pellet that i got from precipitation still looks a bit yellowish.

-krystle-

EDTA, carbohydrates and GuHCl too absorb at 230, may be these are the reasons for low 260/230 ratio. As far as the yellow color is concerned, some times if the DNA is too concentrated i have noticed that. But i am not sure if that is the only reason.
Best luck!!!

-Pradeep Iyer-