Reconstituting a lyophilized vial
Getting a lyophilized peptide from powder to a solution of known concentration, without degrading it on the way.
What this covers: it ends when the vial is mixed, labeled, and stored. Nothing past that point is in scope, and nothing here is a recommendation of any amount. For research use only.
01What reconstitution actually does
The vial holds a fixed mass of peptide. 10 mg is 10 mg. Adding diluent doesn't change that mass — it only decides how much liquid the mass is spread through.
That ratio, milligrams per millilitre, is the concentration, and it is the only thing your volume choice controls. Every arithmetic error downstream traces back to someone forgetting this one sentence.
02Choosing a diluent
Bacteriostatic water is sterile water with 0.9% benzyl alcohol added as a preservative. The preservative is what makes repeated draws from a single vial viable, because it suppresses microbial growth between entries.
Plain sterile water has no preservative. It's a single-use proposition — once the seal is broken there is nothing in the vial working against contamination.
Some poorly soluble compounds call for a dilute acetic acid solution instead. That's compound-specific and belongs in that compound's own documentation, not in a general guide.
03Before you add anything
- Let a cold vial come to room temperature first. Condensation on a cold stopper is a contamination route.
- Swab both stoppers with 70% isopropyl and let them dry. Wet alcohol dragged into the vial by the needle defeats the point of swabbing.
- Don't touch the septum after swabbing. Not with a finger, not with the needle hub, not with anything.
04Adding the diluent
Aim the stream at the inside glass wall and let it run down to the cake. A stream fired directly into the lyophilized powder shears the peptide — you are hitting a fragile solid with a jet of liquid.
Add slowly. The vial is under vacuum and will pull the liquid in on its own; fighting that pull is how you end up with a spray. Then set it down and leave it alone.
05Dissolving
Swirl gently, or roll the vial between your palms. Do not shake it.
Shaking foams the solution, and the air–liquid interface is exactly where peptides denature. Visible foam means material has already been lost. Don't heat it, don't sonicate it, don't try to force it. Most compounds go clear on their own within a few minutes of sitting.
06When something is wrong
A properly reconstituted vial is clear and free of visible particulates.
Persistent cloudiness, floaters, gel, or discolouration mean something is wrong — with the material, the diluent, or the technique. Don't use it, and don't try to filter or re-dissolve your way out of it. A vial that looks wrong is telling you something you can't un-know.
07Storage and labeling
Reconstituted solution goes in the refrigerator at 2–8 °C, protected from light. Lyophilized material keeps far longer than solution does, frozen and dry.
Label every vial with four things: compound, concentration in mg/mL, diluent used, and the date you reconstituted it.
An unlabeled vial at the back of the fridge is worthless. You no longer know its concentration, which means you no longer know what any measurement taken from it means. The label is not bookkeeping — it's the only thing that makes the arithmetic possible.
08Now the arithmetic
Once you know the mass in the vial and the volume you added, the conversion is fixed and there's nothing left to guess at. The calculator on the front page does it.