[pav]

please help me in diluting stock solution.

Stock solution : 25 mg of a compound is dissolved in 100ml of water. so final concentration will be 25,000μg/100ml or 250μg/1ml.

from this solution how to prepare 100 μg/ml, 50 μg/ml, 25 μg/ml, 12.5  μg/ ml concentrated solutions. ?

[sjb]

please help me in diluting stock solution.

Stock solution : 25 mg of a compound is dissolved in 100ml of water. so final concentration will be 25,000μg/100ml or 250μg/1ml.

from this solution how to prepare 100 μg/ml, 50 μg/ml, 25 μg/ml, 12.5  μg/ ml concentrated solutions. ?

Say for instance you need 100 ml of the 100 μg/ml solution? How much of your active compound is this? What volume of 250 μg/ml solution contains this...

[dPaabo]

Here's a nifty formula: (C1)(V1) = (C2)(V2), where C is Concentration and V is volume. Also, ug/mL and ppm are interchangeable; I prefer the latter.

You know C1, C2, and V2 (C1 is 250ppm, C2 is 100ppm, V2 is however much 100ppm solution you want to end up with; we'll need to use some later, so let's make 100mL). V1 will be the amount of 250ppm solution you will need to dilute to 100mL to get your 100ppm solution. So, what happens when you plug your numbers in?

From there, you can make 1:1 dilutions to cut the concentration of any solution in half, which should get you fairly easily to 12.5. Hope this helps!

Edit:
Ehhh I just realized maybe I was being TOO helpful. Edited to make you think a bit about it