Concentration & math
Concentration is the whole game: it is the bridge between the mass of peptide in a vial and the volume you measure on a syringe. One formula covers it, and the arithmetic stays simple.
The formula
Concentration is simply the mass of peptide divided by the volume of water you added when reconstituting:
Concentration (mg/mL) = peptide mass (mg) ÷ water added (mL)Everything else, converting to micrograms, working out what a given number of units holds, falls out of this one relationship. Recall that 1 mg = 1000 mcg.
Worked examples
Two vials, two water volumes. Notice how the same family of compound gives a different concentration purely because of the water added.
Quick reference table
Common vial sizes and water volumes, with what a 10-unit and 20-unit draw on a U-100 syringe holds at each concentration.
| Vial | Water | Concentration | per 10 u (0.1 mL) | per 20 u (0.2 mL) |
|---|---|---|---|---|
| 5 mg | 1 mL | 5.0 mg/mL | 500 mcg | 1000 mcg |
| 5 mg | 2 mL | 2.5 mg/mL | 250 mcg | 500 mcg |
| 5 mg | 2.5 mL | 2.0 mg/mL | 200 mcg | 400 mcg |
| 10 mg | 1 mL | 10.0 mg/mL | 1000 mcg | 2000 mcg |
| 10 mg | 2 mL | 5.0 mg/mL | 500 mcg | 1000 mcg |
| 50 mg | 5 mL | 10.0 mg/mL | 1000 mcg | 2000 mcg |
Let the calculator do it
Once you are comfortable with where the numbers come from, you do not have to do the arithmetic by hand.
Reconstitution calculator
Enter the vial size and water volume and the tool returns the concentration and per-unit figures for you. Open the Peptide.ST reconstitution calculator.