Peptide reconstitution calculator
Three numbers in, one out. It corrects the label mass for net peptide content, which is the step most people skip, and it stops at concentration.
Concentration
5.00 mg/mL
- Peptide in the vial
- 10.00 mg
- Per 0.1 mL
- 0.50 mg
- In micrograms
- 5000 µg/mL
Net peptide content is set to 100 percent, so this is an upper bound. Enter the figure from the certificate if it reports one.
The arithmetic
What the tool is doing
Concentration is peptide mass divided by diluent volume. The only subtlety is which mass. A lyophilized vial is peptide plus counterion, water and residual salts, and the label states the powder. Net peptide content, where the certificate reports it, is the fraction of that powder which is peptide, so the tool multiplies the label mass by it first and divides by the volume second.
The volume is whatever was added, not the volume of the vial. Adding 2 mL to a 3 mL vial makes 2 mL of solution.
Questions
Common questions
Why does the calculator ask for net peptide content?
Because the label mass is the powder and the powder is not all peptide. Counterion, water and residual salts make up the rest. A vial labelled 10 mg at 78 percent net peptide content holds 7.8 mg of peptide, and a concentration worked from 10 is off by that margin in every number after it. Leave it at 100 if the certificate does not report it, and know that the result is then an upper bound.
Why is there no field for how much to draw?
Because that number is a quantity, and this site does not publish quantities for any compound. The calculator gives the concentration of what is in the vial and stops there.
Does the diluent change the answer?
Not the concentration. Bacteriostatic water, sterile water and dilute acetic acid give the same mg per mL for the same volume. What they change is how long the solution keeps and whether a difficult sequence dissolves at all, which the handling guide covers.
What if the peptide will not dissolve at that volume?
Adding more diluent lowers the concentration and does not fix a charge mismatch. The solubility guide explains how to read the sequence for which direction to move the pH.