I am trying to use beta Estradiol as a compound to test in cell culture, and it is only dissolvable in ethanol, and whenever I try to carry out serial dilutions to carry out the dilution to nanomolar levels, the hormone seems to come out of solution rapidly. Any pointers/tips/advice for a grad student in need?

I do not have the definite answer, but in most of these cases we either have a massive initial dilution step to avoid precipitation and/or dilute it directly into large volumes (e.g. the cultivation medium itself).

I appreciate the reply CharonY. When you say massive initial dilution step, were you able to still get results regularly? I've tried the mass dilutions and my results always seem to vary for FURA imaging or current clamp work.

i assume that it would depend quite a lot on how precise you can do it. In my case I was looking at protein expression responses and the results were quite consistent.

However I either diluted them into the (bought) media bottle directly and used it for all experiments in one go (although bottle-to bottle variation was not too bad either), for smaller volumes I used either volumetric flasks if I need volume percentages. The controls were also poured into clean flasks, but without addition (to make sure that there was nothing in the glass affecting the results).

For w/v percentages I weighed the medium in.