Lyophilised vials vs pre-filled pens: comparing research peptide formats

What each format is

Both are labelled for in vitro laboratory research when sold by a research supplier.

• Lyophilised vial: the peptide is freeze-dried to a powder in a sealed vial and prepared into solution in the laboratory when needed.
• Pre-filled pen: the peptide is supplied already in solution inside a delivery device, so there is no preparation step.

Stability

Dry powders are usually more stable than solutions because hydrolysis, oxidation and microbial growth all depend on water. A pen holds the peptide in solution, so its shelf life and storage conditions matter more and should be stated clearly by the supplier.

Concentration and labelling

For a vial, the label gives the total mass of peptide, and any concentration is decided in the lab. For a pen, the label gives total mass in a fixed volume, so confirm what the stated strength refers to before comparing products.

Comparing price fairly

A pen usually carries a premium for the device and the ready-to-use format. Divide the price by the milligrams of peptide to compare formats, and compare sizes within a format, since larger sizes usually cost less per mg. The price-per-mg guide covers this in detail.

What to check on the CoA

A CoA that cannot be matched to your batch is not evidence about your batch.

• The batch number matches the product in your hand.
• The document names the compound, and ideally the format.
• Identity (mass spectrometry) and purity (HPLC) are both reported, with raw data.