Choosing a research peptide is not about "which one is most popular" — it is about fit to your protocol and the reproducibility of your results. Two lots of the same compound can differ in purity, and poor storage can undo even a high-quality material. Below are the practical criteria to weigh for every peptide before you order.

1. Purity and the certificate of analysis (COA)

Purity is the baseline quality metric. For most research the benchmark is ≥ 98 % by high-performance liquid chromatography (HPLC), with identity confirmed by mass spectrometry (MS). The key rule: judge a peptide not by the "typical" purity in the product copy, but by the COA for your specific lot.

  • HPLC — the actual purity of that lot, not an averaged figure;
  • MS — confirmation of molecular mass and identity;
  • the lot number on the COA must match the number on the vial — the basis of traceability.

If a supplier offers no per-lot COA, or a single document "for all vials", that is a reason to ask further questions.

2. Form, fill and quantity

Research peptides usually ship lyophilized — as a dry solid in the vial. Note the amount of active substance in milligrams per vial: it determines how many experiments you can run and how to work out the target concentration after reconstitution. To compare offers, it is easier to reason in price per milligram rather than per vial.

3. Solubility and reconstitution

Before use, the lyophilate is reconstituted in an appropriate solvent — most often bacteriostatic water. Check the recommended solvent and target concentration in advance so you neither waste material nor end up with a cloudy solution. Add the solvent slowly, down the wall of the vial, without vigorous shaking.

4. Stability and storage

A lyophilized peptide is considerably more stable than a reconstituted one. General guidance:

  • lyophilate — long-term storage at −20 °C, protected from light and moisture;
  • reconstituted solution — short shelf life, refrigerated (+2…+8 °C);
  • avoid repeated freeze/thaw cycles — they accelerate degradation.

5. Documentation and compliance

A reliable supplier provides traceability: a COA for every lot, a match between vial and document, and clear labelling (name, strength, lot, expiry). All materials are intended strictly for laboratory research and not for use in humans or animals.

A quick checklist before ordering

  • Is there a COA for your exact lot (HPLC + MS)?
  • Does the purity match the task (typically ≥ 98 %)?
  • Are the mg-per-vial and price-per-mg clear?
  • Are the solvent and storage conditions stated?
  • Does the lot marking match the paperwork?

Not sure where to start?

We built a short matcher: a few questions and you get a peptide suited to your research goal, together with a link to its COA.

Take the quiz and match a peptide →

This material is informational and concerns in vitro research only. It is not medical advice or a usage guide.