How to store and reconstitute peptides

Peptides are delicate molecules. How you store and dissolve them decides how long they stay stable and how reliable your research results are. This guide covers the key laboratory guidelines, from storing lyophilised powder to reconstituting with bacteriostatic water.

Storing lyophilised powder

Peptides are most stable freeze-dried. Keep unopened vials dark, dry and cool: a fridge (2–8 °C) for a few weeks, a freezer (−20 °C) for months.

• Protect from light – keep vials in their box or a closed storage case
• Avoid moisture – let a cold vial reach room temperature before opening so no condensation forms
• Avoid repeated freezing and thawing

Bacteriostatic water or sterile water?

Bacteriostatic water is sterile water with 0.9% benzyl alcohol, which inhibits bacterial growth, so a vial can be accessed several times. Sterile water contains no preservative and is meant for single use, for example from an ampoule.

For solutions used over several days in the lab, bacteriostatic water is the usual choice; sterile water suits solutions used immediately.

Step-by-step reconstitution in the lab

Work cleanly and calmly. The standard procedure:

• Let the vial and solvent reach room temperature
• Disinfect both rubber stoppers with an alcohol pad (70% isopropyl alcohol)
• Draw up the calculated volume of solvent with a sterile syringe
• Let the solvent run slowly down the inside wall of the vial, not straight onto the powder
• Swirl gently until dissolved – do not shake, foaming can damage the peptide
• Label the vial with date and concentration

Calculating the concentration

Concentration depends on the amount of peptide in the vial and the volume of solvent. Our free peptide calculator works it out in seconds.

Storing after reconstitution

A dissolved peptide is less stable than the powder. Keep the solution refrigerated (2–8 °C), away from light, and do not freeze it. Use a new sterile needle for every access and note the reconstitution date.

Common mistakes

The mistakes we see most:

• shaking instead of swirling
• opening a cold vial so condensation gets in
• keeping solutions at room temperature or in sunlight
• not labelling date and concentration

Supplies for storage and reconstitution

• Bacteriostatic Water 10mL
• Sterile Water 2mL – Box of 10 Ampoules
• Alcohol Prep Pads – 70% Isopropyl Alcohol (500 stuks)
• Transparante Peptide Vial Storage Box (3ML)
• 3ML Opzuigspuit + Blauwe Naaldkop

Frequently asked questions

How long does lyophilised peptide keep?

Unopened, dark and dry it stays stable for a long time – months to years in a freezer (−20 °C). Follow the expiry date on the label.

Can I freeze a reconstituted peptide?

Better not: repeated freezing and thawing can degrade it. Keep the solution refrigerated.

Why bacteriostatic water?

The 0.9% benzyl alcohol inhibits bacterial growth, so a vial can safely be accessed several times in the lab.