Question

You have a stock solution of epinephrine at a concentration of 1 mg/mL. Knowing that the pipette you will use delivers 20 drops/mL, a. calculate the number of drops of the stock solution that must be added to a smooth muscle bath containing 25 mL of Locke’s solution so that the final concentration of epinephrine in the muscle bath will be 100 µg/mL, and

Answer 1

Answer : The number of drops pf the stock solution mist be added are, 50 drops.

Explanation :

As we are given that the concentration of stock solution 1 mg/mL and pipette delivers 20 drops/mL. That means,

1 mg of epinephrine = 1 mL = 20 drops

The final volume of Locke's solution = 25 mL

and the final concentration needed = $100\mu g/mL$

As, 1 mL of solution contains = $100\mu g$

So, 25 mL of solution contains = $\frac{25mL}{1mL}\times 100\mu g=2500\mu g=2.5mg$

Conversion used : $1\mu g=0.001mg$

Now we have to determine the number of drops needed.

As, 1 mg of epinephrine contains 20 drops.

So, 2.5 mg of epinephrine contains 2.5 × 20 = 50 drops.

Therefore, the number of drops pf the stock solution mist be added are, 50 drops.