Hi Patrick, highly unlikely that the temperature had anything to do with your problem; have you tried doing this before at room temperature? Guanidinium thiocyanate contamination should not be a problem if you washed with sufficient ethanol wash buffer.

As already suggested, a high 230 nm peak according to me indicates the presence of contaminants like phenol (used for extraction) or carbohydrate from the source. The cold temperature used may not be the exact problem but may have assisted in the precipitation of the contaminants present in the sample long with your DNA. You can read the following for better understanding.

Hope it helps!

http://www.nanodrop.com/Library/T042-NanoDrop-Spectrophotometers-Nucleic-Acid-Purity-Ratios.pdf

Hey Patrick, hope you're well. Doubt that temperature is the problem here. How concentrated was your purified DNA? I tend to see high A230 when the DNA concentration is in the lower range (say

Thanks to all of you for your answers, and an additional thanks to you, David, for the information you provided; indeed, I did column purification with the same kit, but by using the restriction digestion products directly, rather than from cut gel, and had significantly less contamination around A230, so it may actually be the agarose. I will dig deeper into that later this week. Thanks!

There may be a problem with the ineffcient washing step that leaves some presumable carbohydrate contaminants in your DNA. We have had a similar experience using Spin purification columns of different proveniences. We found that reducing centrigugation speed from 14000 RPM (~20000 x g) to 7000 RPM (5000 x g) and increasing time of centrifugation by 4 x leads to a  more efficient washing of bound DNA and hence a better purity.

Be sure to blank the spectrophotometer with the same buffer that you dissolved your recovered DNA in, not just with water. The Tris and EDTA in TE buffer won't change your A260 and A280 values much, but can impact the A230 significantly.