Hi, use the formula of M1V1 = M2V2, M = molarity, V = volume

Saying that your initial molarity is 100 pmol/µL and you want to dilute to a final molarity of 5 pmol/µL in a final volume of 50 µL, the equation will be like this.

M1V1 = M2V2

(100 pmol/ul)(V1) = (5 pmol/ul)(50 uL)

(100 pmol/ul)(V1) = (250 pmol/ul)

V1 = 2.5 uL

So, you need to take a 2.5 uL volume from your 100 pmol/uL and dilute them in 47.5 uL of nuclease-free water. Hence, the concentration will be 5 pmol/uL

Thank you