Peptide reconstitution: a laboratory guide.

Lyophilized (freeze-dried) peptides arrive as a stable powder. You reconstitute them in the lab before use. Your aim is a known, repeatable concentration, prepared with sterile technique that keeps the peptide intact.

1. Choosing a diluent

Bacteriostatic water is sterile water with 0.9% benzyl alcohol. It is the most common diluent for vials you draw from more than once, because the preservative limits microbial growth over the working life of the vial. Use sterile or 0.9% sodium chloride when you want a preservative-free, single-use preparation. The diluent volume you choose sets the final concentration. More water gives a lower concentration and a larger, easier-to-measure draw.

2. Technique

• Let both the vial and diluent reach room temperature, then wipe both stoppers with alcohol.
• Draw the chosen diluent volume and release it slowly down the inside wall of the vial. Never jet it straight onto the powder.
• Do not shake. Swirl gently or leave it to dissolve. Agitation can shear and break down peptide chains.
• Once the solution is clear, it is ready. Do not use a cloudy solution or one that stays full of particles.

3. Concentration math

Concentration = peptide mass ÷ diluent volume. A {10 mg} vial reconstituted with 2 mL of bacteriostatic water gives 5 mg/mL (5000 mcg/mL). On a U-100 insulin syringe, 100 units = 1 mL, so each unit holds 50 mcg in that example. To skip the hand math, use the reconstitution calculator. It returns the concentration, the exact syringe draw for a target amount, and how many preparations a vial yields.

4. Storage & stability

Store lyophilized powder cold and dark. We keep most catalog items at 2 to 8 °C and away from light. Reconstituted peptides are far less stable, so keep the solution refrigerated, avoid repeated freeze-thaw cycles, and follow the stability window listed on the product page. Label every prepared vial with the concentration and date.