Isopropanol mixes with water. It is supposed to lead to the DNA precipitating. You centrifuge to have the precipitated DNA accumulate as a pellet at the bottom of your tube.

Thank you very much for your answers. I did not know that it was possible. However, based on your answers, I have one more question.

I used to perform this extraction using normal EDTA Buffer (pH= 8), which did not mix with isopropanol (at least the one I had). On the other hand, isopropanol is soluble in water, as you indicated me.

Do you know why it could be?

Thank you very very much for your time Sven Buelow Bannikov Artyom

Hi, Victor.

As you already know now, they are miscible. But now you want to know hwy you did have two different layers in an old experiment. Rigtht?

If so, maybe you did prepare or got a wrong solution; maybe you left chloroform in the sample and it has given you the different layers; maybe yo're confusing the steps; maybe the concentration was different then the one you're using know (which might be correct now); maybe it was not EDTA or some form of EDTA which has an incompatible additive or modification. So, as you probably noted, there is no answer without complete data. You would need to send your protocol and all solutions concentrations, pHs, etc, for us to think about it.

Hope it helps.