How to Reconstitute Lyophilized Peptides with Bacteriostatic Water

WHY BACTERIOSTATIC WATER?

Bacteriostatic water is sterile water with 0.9% benzyl alcohol, which inhibits bacterial growth after the vial has been punctured. That makes it the standard diluent when a reconstituted vial will be drawn from more than once over several days or weeks. Plain sterile water has no preservative, so it is generally reserved for single-use preparations.

WHAT YOU NEED

Gather everything before you start so the vials spend as little time open to the air as possible.

• Your lyophilized peptide vial
• Bacteriostatic water
• Alcohol prep pads
• A sterile syringe sized for the volume you plan to add
• A clean, flat work surface and gloves

STEP BY STEP

• Let a refrigerated vial come to room temperature for a few minutes to reduce condensation.
• Wipe both rubber stoppers with an alcohol pad and let them air-dry.
• Draw the chosen volume of bacteriostatic water into the syringe.
• Insert the needle into the peptide vial at an angle and let the water run slowly down the inside wall of the glass — never spray it directly onto the powder.
• Gently swirl or roll the vial until the powder dissolves. Do not shake: vigorous agitation can damage fragile peptide chains.
• The solution should be clear. Cloudiness or particles that do not dissolve are a sign something is off.
• Label the vial with the date and the concentration.

WORKING OUT YOUR CONCENTRATION

Concentration is simply the amount of peptide divided by the volume of liquid. A 10mg vial reconstituted with 2mL of bacteriostatic water gives 5mg/mL (5,000mcg per mL). With 1mL it would be 10mg/mL. Adding less water gives a stronger solution; adding more gives a weaker one that is easier to measure precisely in small amounts.

Pick a volume that makes your downstream math clean, write the result on the label, and keep it consistent across experiments.

STORAGE AFTER RECONSTITUTION

Once in solution, peptides degrade faster than in powder form. Store reconstituted vials refrigerated at 2–8°C, away from light, and use within the window appropriate for the compound — typically a few weeks. Unreconstituted lyophilized vials keep longest refrigerated or frozen.