Vial, cartridge or pen: what is the difference?
A vial, a cartridge and a disposable pen can hold exactly the same molecule. What differs is the format, and the format decides how much you can still verify yourself.
The three formats side by side
| Vial | Cartridge | Disposable pen | |
|---|---|---|---|
| Contents | powder | solution | solution |
| Needs dissolving | yes | no | no |
| Set the amount yourself | yes | through the pen | through the pen |
| Refillable | not applicable | yes, in a refillable pen | no |
| Shelf life | long | shorter | shorter |
| Can be weighed | yes | no | no |
The vial gives you the most control
Powder in a vial is the oldest and most flexible format. You decide how much solvent to use, and therefore the concentration. You can weigh the powder if you want. And because it is dry, it keeps the longest.
The price you pay is an extra step with an extra chance to get something wrong: measuring badly, shaking too hard, not cleaning the cap.
The cartridge removes a step
A cartridge is a glass sleeve with a rubber plunger, filled with a ready-made solution, that fits a refillable pen. There is nothing to dissolve or transfer, so there are fewer handling steps and with them less chance of contamination.
Against that, the concentration is fixed. You can no longer weigh how much is really in there, because it is already dissolved. From that point the batch certificate of analysis is your only check.
The disposable pen is sealed
A prefilled pen is in effect a cartridge that never leaves its holder. Fewest handling steps, but also the least freedom: you cannot take anything out, top anything up or verify anything. When the pen is empty it goes.
The moment a peptide sits in water the clock runs. Cartridges and pens therefore reach you with a head start on their own ageing. So ask for the fill date, not only the production date of the raw material.
Which format when
- If you want to vary concentrations or weigh something: a vial.
- If you want as few handling steps as possible and always work with the same amount: a cartridge in a refillable pen.
- If it is a short run and you want to prepare nothing at all: a disposable pen.
- If the substance degrades quickly in solution: rather a vial, so you can prepare fresh.
A note on pens and needles
Pen needles are not universal, even though they look alike. Check that the thread matches the pen you have. And use each needle once: after one pass the tip is already slightly deformed, which you notice as rising resistance.
This site is made by the team behind Apex Bio Research, a Dutch supplier of research peptides with a certificate of analysis per batch.
Visit the shopThis site explains what the scientific literature says about peptides. It is not medical advice and not a set of instructions. The substances discussed here are research compounds: they are not approved for use in humans or animals. If you have a health question, see a doctor.
Read next
Dissolving peptides: which solvent for what?
Bacteriostatic water, sterile water or dilute acetic acid. What the difference is, why some peptides refuse to dissolve and what to do then.
Reading a certificate of analysis
What belongs on a CoA, what a purity figure does and does not mean, and how to tell whether a certificate belongs to your vial.