I'm having trouble dissolving my drugs in RPMI medium (turbidity or precipitation occurs). My drugs are dissolved in 100% ethanol (final concentration on cells should be below 0,5%). I tried to go from 0,1M drug in 100% ethanol to 0,01M in medium (which makes 10% ethanol in 1ml medium) to 100µM in 1mL medium (which gives me 0,1% ethanol). I did this one step in between so I could take 10µL from the 0,01M to the 100µM. But when I add that 100µL from the 0,1M solution to medium, in order to get 0,01M, the medium turns 'milky'. I guess this is totally not ok to use for further diluting...
Is this a correct way to deal with the problem:
I dissolve my compounds in 100% ethanol to a concentration of 0,1M. I will then directly add 1µL of this stock to 999µL medium (final volume of 1mL). By doing this the ethanol will be 0,1% in the final volume, which is save for the cells, and my final concentration will be 100µM.
Is it ok to take only 1µL? And is it ok to assume that a 1/1000 dilution will make the drug dissolve (I tested this in eppendorf tubes and I couldn't see any turbidity or precipitation problems, but this was just by looking at it...)?