How to Reconstitute Research Peptides (Step-by-Step + Worked Math)

Research-use information only. The peptides discussed are laboratory reference materials, not for human or animal consumption.

Reconstitution is the process of dissolving a lyophilised (freeze-dried) peptide powder into a liquid so it can be measured and used in research. Done correctly, it is simple volumetric dilution; done carelessly, it degrades the peptide or makes your concentrations unreliable. This guide covers the method and the maths.

What you need

• Bacteriostatic water — water containing 0.9% benzyl alcohol. The preservative lets a multi-use vial stay stable for weeks. Use this rather than sterile or distilled water when the solution will be drawn from more than once.
• A sterile syringe for measuring and transferring liquid.
• The peptide’s Certificate of Analysis (COA), to confirm the stated mass before you calculate anything.

The method, step by step

1. Let both vials reach room temperature.
2. Wipe both rubber stoppers with alcohol.
3. Draw your chosen volume of bacteriostatic water.
4. Add the water slowly down the inside wall of the peptide vial — never squirt it directly onto the powder.
5. Do not shake. Swirl gently and let it stand until fully clear. Peptides are fragile; mechanical agitation can break them.
6. Label the vial with the concentration and the date.

The concentration maths

The only formula you need:

milligrams in the vial ÷ millilitres of water added = milligrams per millilitre (mg/ml)

Worked examples:

• 10 mg vial + 2 ml water = 5 mg/ml
• 10 mg vial + 1 ml water = 10 mg/ml
• 5 mg vial + 2.5 ml water = 2 mg/ml

To find the volume that contains a given quantity of peptide, divide the quantity you want by the mg/ml you prepared. The more water you add, the more dilute (and easier to measure precisely) each unit of volume becomes.

Common mistakes

• Shaking the vial. Swirl only.
• Using tap, distilled or sterile water for a multi-use vial. Without a preservative the solution has a much shorter usable life.
• Not labelling. An unlabelled reconstituted vial is unusable data — you no longer know the concentration.
• Skipping the COA check. Your maths is only as good as the stated mass. Verify it against the batch COA first.

After reconstitution

Store the prepared solution refrigerated at 2–8 °C, protected from light, and avoid repeated freeze–thaw cycles. See our guide on handling and storage for shelf-life details, and browse the catalogue for COA-verified reference materials and bacteriostatic water.