Understanding Concentration

Concentration is the amount of substance per unit of volume. A 10 mg vial reconstituted with 2 mL of diluent gives a concentration of 5 mg per mL, which is 5,000 mcg per mL.

To find the volume containing a target amount, divide the target by the concentration. A 500 mcg target at 5,000 mcg per mL is 0.1 mL.

The volume of diluent sets the resolution

More diluent means a lower concentration, so each target amount occupies a larger, easier-to-measure volume. Less diluent means smaller volumes and larger errors from the same measurement imprecision.