Reconstituting and storing a lyophilised peptide
The procedure, the arithmetic and the storage conditions, in the order you need them with a vial in front of you. For laboratory use by qualified researchers.
The procedure
- 01
Bring both vials to room temperature
Take the peptide and the bacteriostatic water out of the fridge and let them sit until neither is cold to the touch. Adding cold solvent to cold powder slows dissolution and encourages the cake to clump.
- 02
Wipe both stoppers
Alcohol swab on the rubber septum of each vial, and let it dry. This is the step most often skipped and the one that decides whether the vial stays usable across multiple withdrawals.
- 03
Draw the solvent you calculated
Work out the volume first, not after. The volume you add is what sets the concentration, and it cannot be corrected later without discarding the vial.
- 04
Run it down the glass wall
Angle the needle so the stream lands on the inside wall of the vial and runs down to the cake. Spraying directly onto lyophilised powder drives foaming, and lipidated peptides are shear-sensitive.
- 05
Swirl, never shake
Roll the vial gently between your fingers until the solution is clear. It can take a few minutes. Shaking or vortexing denatures peptide in solution and leaves visible foam on the meniscus.
- 06
Inspect before you use it
A correctly reconstituted vial is clear and free of particles. Cloudiness, visible strands or an unexpected colour mean something is wrong; do not use it, and log the lot number.
- 07
Label with the date
Write the reconstitution date and concentration on the vial. Traceability to a specific assayed lot is the whole point of the batch record, and it survives exactly as long as your labelling does.
Concentration arithmetic
Concentration is vial content divided by the solvent volume you added. Nothing else affects it: not the syringe, not the draw volume, not the number of withdrawals.
Insulin syringes are graduated in units, not millilitres, and 100 units equal 1 mL. That conversion is where most laboratory arithmetic errors happen, so the calculator does it for you and shows the graduation to draw to.
Open the dilution calculatorWorked example
- Vial content
- 5 mg
- Solvent added
- 2 mL
- Concentration
- 2.5 mg/mL
- Per syringe unit
- 0.025 mg
On a 100-unit insulin syringe, where 100 units is 1 mL.
Storage conditions
- Lyophilised, sealed
- 2 to 8 °C, protected from light
- Lyophilised, in transit
- Brief ambient excursions are tolerated; our packing is insulated for it
- Long-term lyophilised
- Minus 20 °C, sealed and dry
- After reconstitution
- 2 to 8 °C, protected from light
- Freeze-thaw cycles
- Avoid. Aliquot instead if a protocol needs repeated access
- Solvent
- Bacteriostatic water for multi-draw work; check your protocol if it requires preservative-free
What goes wrong
- Calculating the concentration after adding the solvent instead of before. The volume decides the concentration, and it is not reversible.
- Spraying solvent straight onto the cake, which foams the solution and, with lipidated peptides, damages material.
- Shaking the vial to speed dissolution up. It does not, and it costs you peptide.
- Reading an insulin syringe as millilitres. A 100-unit syringe is 1 mL end to end.
- Storing a reconstituted vial at room temperature because the powder tolerated transit. Once it is in solution the rules change.
- Losing the link between vial and lot number, which makes the batch certificate meaningless for that vial.