High 260/230 ratio for DNA

I purified my DNA samples form whole blood using QIAamp Blood Maxi Kit (Spin Protocol). Using Nanodrop, my 260/280 ratio was ok (around 1.8), but 260/230 ratio in some samples was as high as 8! I know that ideal 260/230 ratio is around 2, and if it is lower that probably means contamination with organic solvents. Does anybody  knows what  high ratio means?

 You are right it should be aroung 1.5 ideally. What I know from my previous experience is that the high ratio indicates high salt concentration in your sample. Please try to reduce it.

I may be wrong also. Shouldn't we expect the A260 / A230 ratio to be low if the salt concentration is high in the samples? I have experienced this problem and I have not been able to sort out what the error happening with similar A260 / A230 ratios. I have got even once at 18.

I would advice diluting your sample in 10mM Tris-HCl at pH 7.4 but not water. One more thing, low ratios may be due to phenol contamination. Check it out!!! High ratios might come from salts in yoour samples. I never saw ratios as high as indicated here. But if you used Trizol, maybe try doing clean up using a column spin methods and try again. Wish you good luck. 

 I also suspect the high salts conc is the main reason behind it. But you should check spec instrument functioning also.

 Wouldn't a very high 260/230 ratio indicate a low (in in the case of some samples I just OD'd zero) absorbance at A230. Personally, I'm more concerned with contamination issues when I have significant absorbance at A230 indicating phenol, salt, etc (and low 260/230) than when it's too high. From what I've read anything over 2 is good.

Low A230, could also be related to how dilute your sample is; if the A260 is low (say 0.05), then it may be difficult to accurately estimate A230 resulting in over inflated 260/230 ratios. 

I'd remeasure the samples more concentrated, if possible, and see if you can get a better A230 reading. I like to shoot for an A260 of ~0.1.  However, as I said above I think a higher ratio (low A230) is better than low.

After concentrating my samples (using ethanol precipitation after adition of 3M sodium acetate) and re-measuring the concentration, my A260/230 ratio was normal! I suppose the reason for the high ratio could be high initial salt concentration, but whatever it was it is gone after this procedure

I`m working with AFLPs, so I need a nice DNA that could be completely digested. I have seen that DNAs with low 260/230 ratios don`t have fully digestion... it is logical... but also DNAs with High 260/230 ratios (more than 4) just parcially digest. I am wondering myself why this could be happening????