How to prepare solutions of various chemical concentrations/dilutions?

Question

Hello, I'm not sure how to prepare solutions of the concentrations: 0.1, 5, 10, 100 micromolar of chemical where the stock chemical should be at 1000X of the final concentration. I need 50 microliters volume in each solution. I'm not sure if I need to preform a serial dilution or some other method. Also I don't know how much of the stock I need to start with.

Thanks in advance!

Answer 1

Hi Chanapa!

I'm a very visual person, so attached is a video I recorded to help demonstrate how to tackle this problem and similar ones. Hopefully it helps!

Answer 2

Here is the general approach for such a problem, and whether to use serial dilutions or some other is up to you. There are pros and cons to each type of dilution. More on that later.

If I understand your question, you are saying that the stock should be 1000X the final concentration. So, for the 0.1, 5, 10, and 100 uM solutions, you would need stocks of 100, 5000, 10,000 and 100,000 uM. Is that correct? If so, then all you need from here is V1M1 = V2M2 where V1 and M1 are initial volumes and molarity respectively, and V2 and M2 are final volumes and molarity, respectively.

So, from a 100 uM stock to make 50 ul of a 0.1 uM solution, you would have the following equation:

(x ul)(100 uM) = (50 ul)(0.1 uM) and x = 0.05 uM. This is a volume you are not likely able to measure.

So, maybe I have misinterpreted your question. If so, you should repost it with a clearly description of what you want to accomplish.

As for serial dilutions vs. direct dilutions (volumetric), if you make 1 error in your serial dilutions, all of the following solutions will be wrong. If you make 1 error in your direct dilution, only that 1 solution will be wrong. Advantage goes to direct dilution. Direct dilutions are a little more tedious however. The choice is yours.