Peptide Storage & Reconstitution Guide

Storing lyophilized (powder) vials

Sealed lyophilized vials are the most stable form the peptide will ever be in. Keep them that way as long as possible — reconstitute only what you plan to use.

• Short term (up to ~4 weeks): refrigerated at 36–46°F (2–8°C).
• Long term (months): freezer at −4°F (−20°C) or colder, in a sealed container with desiccant.
• Always protect from light; keep vials in their original box or an opaque container.
• Let a cold vial reach room temperature before opening — condensation inside the vial introduces moisture that shortens shelf life.

Choosing a diluent

Bacteriostatic water (sterile water with 0.9% benzyl alcohol) is the standard choice for multi-use vials because the preservative suppresses microbial growth. Plain sterile water has no preservative and is appropriate only for single-use preparations.

A small number of peptides are poorly soluble in neutral water and require a small volume of dilute acetic acid or another solvent before bringing the solution up to volume. Check the compound's documentation before assuming water alone will dissolve it.

Reconstitution, step by step

The goal is to dissolve the powder gently and completely, without foaming.

• Work on a clean surface. Wipe both vial stoppers with an alcohol swab and let them dry.
• Draw the target volume of bacteriostatic water into a sterile syringe.
• Angle the needle so the stream runs down the inside wall of the vial — never spray directly onto the powder cake.
• Release the syringe plunger slowly; the vial's vacuum will pull the liquid in on its own.
• Swirl or roll the vial gently until clear. Never shake — shear force and foaming denature peptides.
• If material remains undissolved after a few minutes, let the vial sit at room temperature and swirl again rather than agitating harder.

Working out concentration

Concentration is simply the peptide mass divided by the diluent volume. A 5 mg vial reconstituted with 2 mL of bacteriostatic water yields 2.5 mg/mL. Adding 1 mL to the same vial yields 5 mg/mL.

Choose a volume that makes your measurements easy to read rather than one that minimizes the number of vials — measurement error at very high concentrations is the more common problem.

Storing reconstituted solutions

Once in solution, a peptide's clock starts. Refrigerate immediately after reconstitution and keep it there.

• Refrigerated at 36–46°F, most reconstituted peptides remain usable for roughly 3–6 weeks; some are considerably shorter.
• Avoid repeated freeze-thaw cycles. If freezing is necessary, aliquot into single-use volumes first.
• Keep solutions out of light and away from the refrigerator door, where temperature swings are largest.
• Discard any solution that becomes cloudy, discolored, or shows visible particulate.

Common handling mistakes

• Shaking the vial to speed up dissolution — the single most common cause of potency loss.
• Reconstituting the whole inventory at once instead of one vial at a time.
• Leaving vials on a bench in a warm room between uses.
• Using plain sterile water in a vial that will be accessed repeatedly.
• Reusing needles between vials, which introduces contamination and dulls the tip.

Frequently asked