Chemists, biochemists, pharmacologists, etc., I seek a piece of practical advice. I have a neuroactive compound that I need to get dissolved in 10 ml of weak salt water so I can expose frog cells to it. What is the best way to get rid of the methanol it comes in? I can evaporate it off but I worry that the drug dries to the sides of the tube and never goes into solution when I put water in it (i.e., I can't tell if there's anything in the water at the end or not). Any ideas?
Have you tried sonicating the solute in the water to dissolve it, and testing the concentration? You may be able to detect it if you can prepare some standards and have access to an HPLC/GC/ or mass spec. Do you know what wavelength the thing absorbs at so you can make a calibration curve for an optical detector? Do you know the expected solubility of the compound in your salt solution?
Alternatively if your compound is stable enough, can you rotovap it? If so, that may help at least remove the methanol, but your solute may still precipitate out of the water, particularly due to the salt. In this case you can readily determine the concentration by knowing the molarity of your original solution, and the volumes of your mixture and the rotovap product; should take out nearly all the guesswork assuming it stays soluble.
